diff --git a/phpcs.xml.dist b/phpcs.xml.dist
index a8387b3604c9b..3f2514003e14c 100644
--- a/phpcs.xml.dist
+++ b/phpcs.xml.dist
@@ -73,6 +73,7 @@
 	<exclude-pattern>/src/wp-includes/js/*</exclude-pattern>
 	<exclude-pattern>/src/wp-includes/PHPMailer/*</exclude-pattern>
 	<exclude-pattern>/src/wp-includes/Requests/*</exclude-pattern>
+	<exclude-pattern>/src/wp-includes/php-ai-client/*</exclude-pattern>
 	<exclude-pattern>/src/wp-includes/SimplePie/*</exclude-pattern>
 	<exclude-pattern>/src/wp-includes/sodium_compat/*</exclude-pattern>
 	<exclude-pattern>/src/wp-includes/Text/*</exclude-pattern>
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 4b5b0d3ded110..fa1b8805a91ec 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -47,6 +47,8 @@
 				<directory suffix=".php">src/wp-includes/IXR</directory>
 				<directory suffix=".php">src/wp-includes/PHPMailer</directory>
 				<directory suffix=".php">src/wp-includes/Requests</directory>
+				<directory suffix=".php">src/wp-includes/php-ai-client</directory>
+				<directory suffix=".php">src/wp-includes/ai-client-utils</directory>
 				<directory suffix=".php">src/wp-includes/SimplePie</directory>
 				<directory suffix=".php">src/wp-includes/sodium_compat</directory>
 				<directory suffix=".php">src/wp-includes/Text</directory>
diff --git a/src/wp-includes/ai-client-utils/class-wp-ai-client-ability-function-resolver.php b/src/wp-includes/ai-client-utils/class-wp-ai-client-ability-function-resolver.php
new file mode 100644
index 0000000000000..e50b86da50165
--- /dev/null
+++ b/src/wp-includes/ai-client-utils/class-wp-ai-client-ability-function-resolver.php
@@ -0,0 +1,181 @@
+<?php
+/**
+ * WP AI Client: WP_AI_Client_Ability_Function_Resolver class
+ *
+ * @package WordPress
+ * @subpackage AI
+ * @since 7.0.0
+ */
+
+use WordPress\AiClient\Messages\DTO\Message;
+use WordPress\AiClient\Messages\DTO\MessagePart;
+use WordPress\AiClient\Messages\DTO\UserMessage;
+use WordPress\AiClient\Tools\DTO\FunctionCall;
+use WordPress\AiClient\Tools\DTO\FunctionResponse;
+
+/**
+ * Resolves and executes WordPress Abilities API function calls from AI models.
+ *
+ * @since 7.0.0
+ */
+class WP_AI_Client_Ability_Function_Resolver {
+
+	/**
+	 * Prefix used to identify ability function calls.
+	 *
+	 * @since 7.0.0
+	 * @var string
+	 */
+	private const ABILITY_PREFIX = 'wpab__';
+
+	/**
+	 * Checks if a function call is an ability call.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param FunctionCall $call The function call to check.
+	 * @return bool True if the function call is an ability call, false otherwise.
+	 */
+	public static function is_ability_call( FunctionCall $call ): bool {
+		$name = $call->getName();
+		if ( null === $name ) {
+			return false;
+		}
+
+		return str_starts_with( $name, self::ABILITY_PREFIX );
+	}
+
+	/**
+	 * Executes a WordPress ability from a function call.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param FunctionCall $call The function call to execute.
+	 * @return FunctionResponse The response from executing the ability.
+	 */
+	public static function execute_ability( FunctionCall $call ): FunctionResponse {
+		$function_name = $call->getName() ?? 'unknown';
+		$function_id   = $call->getId() ?? 'unknown';
+
+		if ( ! self::is_ability_call( $call ) ) {
+			return new FunctionResponse(
+				$function_id,
+				$function_name,
+				array(
+					'error' => 'Not an ability function call',
+					'code'  => 'invalid_ability_call',
+				)
+			);
+		}
+
+		$ability_name = self::function_name_to_ability_name( $function_name );
+		$ability      = wp_get_ability( $ability_name );
+
+		if ( ! $ability instanceof WP_Ability ) {
+			return new FunctionResponse(
+				$function_id,
+				$function_name,
+				array(
+					'error' => sprintf( 'Ability "%s" not found', $ability_name ),
+					'code'  => 'ability_not_found',
+				)
+			);
+		}
+
+		$args   = $call->getArgs();
+		$result = $ability->execute( ! empty( $args ) ? $args : null );
+
+		if ( is_wp_error( $result ) ) {
+			return new FunctionResponse(
+				$function_id,
+				$function_name,
+				array(
+					'error' => $result->get_error_message(),
+					'code'  => $result->get_error_code(),
+					'data'  => $result->get_error_data(),
+				)
+			);
+		}
+
+		return new FunctionResponse(
+			$function_id,
+			$function_name,
+			$result
+		);
+	}
+
+	/**
+	 * Checks if a message contains any ability function calls.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param Message $message The message to check.
+	 * @return bool True if the message contains ability calls, false otherwise.
+	 */
+	public static function has_ability_calls( Message $message ): bool {
+		foreach ( $message->getParts() as $part ) {
+			if ( $part->getType()->isFunctionCall() ) {
+				$function_call = $part->getFunctionCall();
+				if ( $function_call instanceof FunctionCall && self::is_ability_call( $function_call ) ) {
+					return true;
+				}
+			}
+		}
+
+		return false;
+	}
+
+	/**
+	 * Executes all ability function calls in a message.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param Message $message The message containing function calls.
+	 * @return Message A new message with function responses.
+	 */
+	public static function execute_abilities( Message $message ): Message {
+		$response_parts = array();
+
+		foreach ( $message->getParts() as $part ) {
+			if ( $part->getType()->isFunctionCall() ) {
+				$function_call = $part->getFunctionCall();
+				if ( $function_call instanceof FunctionCall ) {
+					$function_response = self::execute_ability( $function_call );
+					$response_parts[]  = new MessagePart( $function_response );
+				}
+			}
+		}
+
+		return new UserMessage( $response_parts );
+	}
+
+	/**
+	 * Converts an ability name to a function name.
+	 *
+	 * Transforms "tec/create_event" to "wpab__tec__create_event".
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $ability_name The ability name to convert.
+	 * @return string The function name.
+	 */
+	public static function ability_name_to_function_name( string $ability_name ): string {
+		return self::ABILITY_PREFIX . str_replace( '/', '__', $ability_name );
+	}
+
+	/**
+	 * Converts a function name to an ability name.
+	 *
+	 * Transforms "wpab__tec__create_event" to "tec/create_event".
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $function_name The function name to convert.
+	 * @return string The ability name.
+	 */
+	private static function function_name_to_ability_name( string $function_name ): string {
+		$without_prefix = substr( $function_name, strlen( self::ABILITY_PREFIX ) );
+
+		return str_replace( '__', '/', $without_prefix );
+	}
+}
diff --git a/src/wp-includes/ai-client-utils/class-wp-ai-client-cache.php b/src/wp-includes/ai-client-utils/class-wp-ai-client-cache.php
new file mode 100644
index 0000000000000..ca19cb6de77bf
--- /dev/null
+++ b/src/wp-includes/ai-client-utils/class-wp-ai-client-cache.php
@@ -0,0 +1,209 @@
+<?php
+/**
+ * WP AI Client: WP_AI_Client_Cache class
+ *
+ * @package WordPress
+ * @subpackage AI
+ * @since 7.0.0
+ */
+
+use WordPress\AiClientDependencies\Psr\SimpleCache\CacheInterface;
+
+/**
+ * WordPress-specific PSR-16 cache adapter for the AI Client.
+ *
+ * Bridges PSR-16 cache operations to WordPress object cache functions,
+ * enabling the AI client to leverage WordPress caching infrastructure.
+ *
+ * @since 7.0.0
+ */
+class WP_AI_Client_Cache implements CacheInterface {
+
+	/**
+	 * Cache group used for all cache operations.
+	 *
+	 * @since 7.0.0
+	 * @var string
+	 */
+	private const CACHE_GROUP = 'wp_ai_client';
+
+	/**
+	 * Fetches a value from the cache.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $key           The unique key of this item in the cache.
+	 * @param mixed  $default_value Default value to return if the key does not exist.
+	 * @return mixed The value of the item from the cache, or $default_value in case of cache miss.
+	 */
+	public function get( $key, $default_value = null ) {
+		$found = false;
+		$value = wp_cache_get( $key, self::CACHE_GROUP, false, $found );
+
+		if ( ! $found ) {
+			return $default_value;
+		}
+
+		return $value;
+	}
+
+	/**
+	 * Persists data in the cache, uniquely referenced by a key with an optional expiration TTL time.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string                $key   The key of the item to store.
+	 * @param mixed                 $value The value of the item to store, must be serializable.
+	 * @param null|int|DateInterval $ttl   Optional. The TTL value of this item.
+	 * @return bool True on success and false on failure.
+	 */
+	public function set( $key, $value, $ttl = null ): bool {
+		$expire = $this->ttl_to_seconds( $ttl );
+
+		return wp_cache_set( $key, $value, self::CACHE_GROUP, $expire );
+	}
+
+	/**
+	 * Delete an item from the cache by its unique key.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $key The unique cache key of the item to delete.
+	 * @return bool True if the item was successfully removed. False if there was an error.
+	 */
+	public function delete( $key ): bool {
+		return wp_cache_delete( $key, self::CACHE_GROUP );
+	}
+
+	/**
+	 * Wipes clean the entire cache's keys.
+	 *
+	 * This method only clears the cache group used by this adapter. If the underlying
+	 * cache implementation does not support group flushing, this method returns false.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return bool True on success and false on failure.
+	 */
+	public function clear(): bool {
+		if ( ! function_exists( 'wp_cache_supports' ) || ! wp_cache_supports( 'flush_group' ) ) {
+			return false;
+		}
+
+		return wp_cache_flush_group( self::CACHE_GROUP );
+	}
+
+	/**
+	 * Obtains multiple cache items by their unique keys.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param iterable<string> $keys          A list of keys that can be obtained in a single operation.
+	 * @param mixed            $default_value Default value to return for keys that do not exist.
+	 * @return array<string, mixed> A list of key => value pairs.
+	 */
+	public function getMultiple( $keys, $default_value = null ) {
+		/**
+		 * Keys array.
+		 *
+		 * @var array<string> $keys_array
+		 */
+		$keys_array = $this->iterable_to_array( $keys );
+		$values     = wp_cache_get_multiple( $keys_array, self::CACHE_GROUP );
+		$result     = array();
+
+		foreach ( $keys_array as $key ) {
+			$result[ $key ] = isset( $values[ $key ] ) && false !== $values[ $key ] ? $values[ $key ] : $default_value;
+		}
+
+		return $result;
+	}
+
+	/**
+	 * Persists a set of key => value pairs in the cache, with an optional TTL.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param iterable<string, mixed> $values A list of key => value pairs for a multiple-set operation.
+	 * @param null|int|DateInterval   $ttl    Optional. The TTL value of this item.
+	 * @return bool True on success and false on failure.
+	 */
+	public function setMultiple( $values, $ttl = null ): bool {
+		$values_array = $this->iterable_to_array( $values );
+		$expire       = $this->ttl_to_seconds( $ttl );
+		$results      = wp_cache_set_multiple( $values_array, self::CACHE_GROUP, $expire );
+
+		// Return true only if all operations succeeded.
+		return ! in_array( false, $results, true );
+	}
+
+	/**
+	 * Deletes multiple cache items in a single operation.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param iterable<string> $keys A list of string-based keys to be deleted.
+	 * @return bool True if the items were successfully removed. False if there was an error.
+	 */
+	public function deleteMultiple( $keys ): bool {
+		$keys_array = $this->iterable_to_array( $keys );
+		$results    = wp_cache_delete_multiple( $keys_array, self::CACHE_GROUP );
+
+		// Return true only if all operations succeeded.
+		return ! in_array( false, $results, true );
+	}
+
+	/**
+	 * Determines whether an item is present in the cache.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $key The cache item key.
+	 * @return bool True if the item exists in the cache, false otherwise.
+	 */
+	public function has( $key ): bool {
+		$found = false;
+		wp_cache_get( $key, self::CACHE_GROUP, false, $found );
+
+		return (bool) $found;
+	}
+
+	/**
+	 * Converts a PSR-16 TTL value to seconds for WordPress cache functions.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param null|int|DateInterval $ttl The TTL value.
+	 * @return int The TTL in seconds, or 0 for no expiration.
+	 */
+	private function ttl_to_seconds( $ttl ): int {
+		if ( null === $ttl ) {
+			return 0;
+		}
+
+		if ( $ttl instanceof DateInterval ) {
+			$now = new DateTime();
+			$end = ( clone $now )->add( $ttl );
+
+			return $end->getTimestamp() - $now->getTimestamp();
+		}
+
+		return max( 0, (int) $ttl );
+	}
+
+	/**
+	 * Converts an iterable to an array.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param iterable<mixed> $items The iterable to convert.
+	 * @return array<mixed> The array.
+	 */
+	private function iterable_to_array( $items ): array {
+		if ( is_array( $items ) ) {
+			return $items;
+		}
+
+		return iterator_to_array( $items );
+	}
+}
diff --git a/src/wp-includes/ai-client-utils/class-wp-ai-client-discovery-strategy.php b/src/wp-includes/ai-client-utils/class-wp-ai-client-discovery-strategy.php
new file mode 100644
index 0000000000000..80bdea4968617
--- /dev/null
+++ b/src/wp-includes/ai-client-utils/class-wp-ai-client-discovery-strategy.php
@@ -0,0 +1,90 @@
+<?php
+/**
+ * WP AI Client: WP_AI_Client_Discovery_Strategy class
+ *
+ * @package WordPress
+ * @subpackage AI
+ * @since 7.0.0
+ */
+
+use WordPress\AiClientDependencies\Http\Discovery\Psr18ClientDiscovery;
+use WordPress\AiClientDependencies\Http\Discovery\Strategy\DiscoveryStrategy;
+use WordPress\AiClientDependencies\Psr\Http\Client\ClientInterface;
+
+/**
+ * Discovery strategy for WordPress HTTP client.
+ *
+ * Registers the WordPress HTTP client adapter with the HTTPlug discovery system
+ * so the AI Client SDK can find and use it automatically.
+ *
+ * @since 7.0.0
+ */
+class WP_AI_Client_Discovery_Strategy implements DiscoveryStrategy {
+
+	/**
+	 * Initializes and registers the discovery strategy.
+	 *
+	 * @since 7.0.0
+	 */
+	public static function init() {
+		if ( ! class_exists( '\WordPress\AiClientDependencies\Http\Discovery\Psr18ClientDiscovery' ) ) {
+			return;
+		}
+
+		Psr18ClientDiscovery::prependStrategy( self::class );
+	}
+
+	/**
+	 * Gets candidates for discovery.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $type The type of discovery.
+	 * @return array<array<string, mixed>> List of candidates.
+	 */
+	public static function getCandidates( $type ) {
+		if ( ClientInterface::class === $type ) {
+			return array(
+				array(
+					'class' => static function () {
+						return self::create_wordpress_client();
+					},
+				),
+			);
+		}
+
+		$psr17_factories = array(
+			'WordPress\AiClientDependencies\Psr\Http\Message\RequestFactoryInterface',
+			'WordPress\AiClientDependencies\Psr\Http\Message\ResponseFactoryInterface',
+			'WordPress\AiClientDependencies\Psr\Http\Message\ServerRequestFactoryInterface',
+			'WordPress\AiClientDependencies\Psr\Http\Message\StreamFactoryInterface',
+			'WordPress\AiClientDependencies\Psr\Http\Message\UploadedFileFactoryInterface',
+			'WordPress\AiClientDependencies\Psr\Http\Message\UriFactoryInterface',
+		);
+
+		if ( in_array( $type, $psr17_factories, true ) ) {
+			return array(
+				array(
+					'class' => WP_AI_Client_PSR17_Factory::class,
+				),
+			);
+		}
+
+		return array();
+	}
+
+	/**
+	 * Creates an instance of the WordPress HTTP client.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return WP_AI_Client_HTTP_Client
+	 */
+	private static function create_wordpress_client() {
+		$psr17_factory = new WP_AI_Client_PSR17_Factory();
+		return new WP_AI_Client_HTTP_Client(
+			$psr17_factory,
+			$psr17_factory
+		);
+	}
+}
diff --git a/src/wp-includes/ai-client-utils/class-wp-ai-client-event-dispatcher.php b/src/wp-includes/ai-client-utils/class-wp-ai-client-event-dispatcher.php
new file mode 100644
index 0000000000000..9eeb85b32a6c0
--- /dev/null
+++ b/src/wp-includes/ai-client-utils/class-wp-ai-client-event-dispatcher.php
@@ -0,0 +1,82 @@
+<?php
+/**
+ * WP AI Client: WP_AI_Client_Event_Dispatcher class
+ *
+ * @package WordPress
+ * @subpackage AI
+ * @since 7.0.0
+ */
+
+use WordPress\AiClientDependencies\Psr\EventDispatcher\EventDispatcherInterface;
+
+/**
+ * WordPress-specific PSR-14 event dispatcher for the AI Client.
+ *
+ * Bridges PSR-14 events to WordPress action hooks, enabling plugins to hook
+ * into AI client lifecycle events.
+ *
+ * @since 7.0.0
+ */
+class WP_AI_Client_Event_Dispatcher implements EventDispatcherInterface {
+
+	/**
+	 * Dispatches an event to WordPress action hooks.
+	 *
+	 * Converts the event class name to a WordPress action hook name and fires it.
+	 * For example, BeforeGenerateResultEvent becomes wp_ai_client_before_generate_result.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param object $event The event object to dispatch.
+	 * @return object The same event object, potentially modified by listeners.
+	 */
+	public function dispatch( object $event ): object {
+		$event_name = $this->get_hook_name_portion_for_event( $event );
+
+		/**
+		 * Fires when an AI client event is dispatched.
+		 *
+		 * The dynamic portion of the hook name, `$event_name`, refers to the
+		 * snake_case version of the event class name, without the `_event` suffix.
+		 *
+		 * For example, an event class named `BeforeGenerateResultEvent` will fire the
+		 * `wp_ai_client_before_generate_result` action hook.
+		 *
+		 * In practice, the available action hook names are:
+		 *
+		 * - wp_ai_client_before_generate_result
+		 * - wp_ai_client_after_generate_result
+		 *
+		 * @since 7.0.0
+		 *
+		 * @param object $event The event object.
+		 */
+		do_action( "wp_ai_client_{$event_name}", $event );
+
+		return $event;
+	}
+
+	/**
+	 * Converts an event object class name to a WordPress action hook name portion.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param object $event The event object.
+	 * @return string The hook name portion derived from the event class name.
+	 */
+	private function get_hook_name_portion_for_event( object $event ): string {
+		$class_name = get_class( $event );
+		$pos        = strrpos( $class_name, '\\' );
+		$short_name = false !== $pos ? substr( $class_name, $pos + 1 ) : $class_name;
+
+		// Convert PascalCase to snake_case.
+		$snake_case = strtolower( (string) preg_replace( '/([a-z])([A-Z])/', '$1_$2', $short_name ) );
+
+		// Strip '_event' suffix if present.
+		if ( str_ends_with( $snake_case, '_event' ) ) {
+			$snake_case = (string) substr( $snake_case, 0, -6 );
+		}
+
+		return $snake_case;
+	}
+}
diff --git a/src/wp-includes/ai-client-utils/class-wp-ai-client-http-client.php b/src/wp-includes/ai-client-utils/class-wp-ai-client-http-client.php
new file mode 100644
index 0000000000000..bddcde6cf62c0
--- /dev/null
+++ b/src/wp-includes/ai-client-utils/class-wp-ai-client-http-client.php
@@ -0,0 +1,229 @@
+<?php
+/**
+ * WP AI Client: WP_AI_Client_HTTP_Client class
+ *
+ * @package WordPress
+ * @subpackage AI
+ * @since 7.0.0
+ */
+
+use WordPress\AiClientDependencies\Psr\Http\Client\ClientInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\RequestInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\ResponseInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\ResponseFactoryInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\StreamFactoryInterface;
+use WordPress\AiClient\Providers\Http\Contracts\ClientWithOptionsInterface;
+use WordPress\AiClient\Providers\Http\DTO\RequestOptions;
+use WordPress\AiClient\Providers\Http\Exception\NetworkException;
+
+/**
+ * PSR-18 HTTP Client adapter using WordPress HTTP API.
+ *
+ * Allows WordPress HTTP functions to be used as a PSR-18 compliant HTTP client
+ * for the AI Client SDK.
+ *
+ * @since 7.0.0
+ */
+class WP_AI_Client_HTTP_Client implements ClientInterface, ClientWithOptionsInterface {
+
+	/**
+	 * Response factory instance.
+	 *
+	 * @since 7.0.0
+	 * @var ResponseFactoryInterface
+	 */
+	private $response_factory;
+
+	/**
+	 * Stream factory instance.
+	 *
+	 * @since 7.0.0
+	 * @var StreamFactoryInterface
+	 */
+	private $stream_factory;
+
+	/**
+	 * Constructor.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param ResponseFactoryInterface $response_factory PSR-17 Response factory.
+	 * @param StreamFactoryInterface   $stream_factory   PSR-17 Stream factory.
+	 */
+	public function __construct( ResponseFactoryInterface $response_factory, StreamFactoryInterface $stream_factory ) {
+		$this->response_factory = $response_factory;
+		$this->stream_factory   = $stream_factory;
+	}
+
+	/**
+	 * Sends a PSR-7 request and returns a PSR-7 response.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param RequestInterface $request The PSR-7 request.
+	 * @return ResponseInterface The PSR-7 response.
+	 *
+	 * @throws NetworkException If the WordPress HTTP request fails.
+	 */
+	public function sendRequest( RequestInterface $request ): ResponseInterface {
+		$args = $this->prepare_wp_args( $request );
+		$url  = (string) $request->getUri();
+
+		$response = wp_remote_request( $url, $args );
+
+		if ( is_wp_error( $response ) ) {
+			$message = sprintf(
+				'Network error occurred while sending %s request to %s: %s',
+				$request->getMethod(),
+				$url,
+				$response->get_error_message()
+			);
+
+			throw new NetworkException( $message ); // phpcs:ignore WordPress.Security.EscapeOutput.ExceptionNotEscaped
+		}
+
+		return $this->create_psr_response( $response );
+	}
+
+	/**
+	 * Sends a PSR-7 request with transport options and returns a PSR-7 response.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param RequestInterface $request The PSR-7 request.
+	 * @param RequestOptions   $options Transport options for the request.
+	 * @return ResponseInterface The PSR-7 response.
+	 *
+	 * @throws NetworkException If the WordPress HTTP request fails.
+	 */
+	public function sendRequestWithOptions( RequestInterface $request, RequestOptions $options ): ResponseInterface {
+		$args = $this->prepare_wp_args( $request, $options );
+		$url  = (string) $request->getUri();
+
+		$response = wp_remote_request( $url, $args );
+
+		if ( is_wp_error( $response ) ) {
+			$message = sprintf(
+				'Network error occurred while sending request to %s: %s',
+				$url,
+				$response->get_error_message()
+			);
+
+			throw new NetworkException(
+				$message, // phpcs:ignore WordPress.Security.EscapeOutput.ExceptionNotEscaped
+				$response->get_error_code() ? (int) $response->get_error_code() : 0
+			);
+		}
+
+		return $this->create_psr_response( $response );
+	}
+
+	/**
+	 * Prepares WordPress HTTP API arguments from a PSR-7 request.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param RequestInterface    $request The PSR-7 request.
+	 * @param RequestOptions|null $options Optional transport options for the request.
+	 * @return array<string, mixed> WordPress HTTP API arguments.
+	 */
+	private function prepare_wp_args( RequestInterface $request, ?RequestOptions $options = null ): array {
+		$args = array(
+			'method'      => $request->getMethod(),
+			'headers'     => $this->prepare_headers( $request ),
+			'body'        => $this->prepare_body( $request ),
+			'httpversion' => $request->getProtocolVersion(),
+			'blocking'    => true,
+		);
+
+		if ( null !== $options ) {
+			if ( null !== $options->getTimeout() ) {
+				$args['timeout'] = $options->getTimeout();
+			}
+
+			if ( null !== $options->getMaxRedirects() ) {
+				$args['redirection'] = $options->getMaxRedirects();
+			}
+		}
+
+		return $args;
+	}
+
+	/**
+	 * Prepares headers for WordPress HTTP API.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param RequestInterface $request The PSR-7 request.
+	 * @return array<string, string> Headers array for WordPress HTTP API.
+	 */
+	private function prepare_headers( RequestInterface $request ): array {
+		$headers = array();
+
+		foreach ( $request->getHeaders() as $name => $values ) {
+			if ( strpos( $name, 'X-Stream' ) === 0 ) {
+				continue;
+			}
+
+			$headers[ (string) $name ] = implode( ', ', $values );
+		}
+
+		return $headers;
+	}
+
+	/**
+	 * Prepares request body for WordPress HTTP API.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param RequestInterface $request The PSR-7 request.
+	 * @return string|null The request body.
+	 */
+	private function prepare_body( RequestInterface $request ): ?string {
+		$body = $request->getBody();
+
+		if ( $body->getSize() === 0 ) {
+			return null;
+		}
+
+		if ( $body->isSeekable() ) {
+			$body->rewind();
+		}
+
+		return (string) $body;
+	}
+
+	/**
+	 * Creates a PSR-7 response from a WordPress HTTP response.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param array<string, mixed> $wp_response WordPress HTTP API response array.
+	 * @return ResponseInterface PSR-7 response.
+	 */
+	private function create_psr_response( array $wp_response ): ResponseInterface {
+		$status_code   = wp_remote_retrieve_response_code( $wp_response );
+		$reason_phrase = wp_remote_retrieve_response_message( $wp_response );
+		$headers       = wp_remote_retrieve_headers( $wp_response );
+		$body          = wp_remote_retrieve_body( $wp_response );
+
+		$response = $this->response_factory->createResponse( (int) $status_code, $reason_phrase );
+
+		if ( $headers instanceof WP_HTTP_Requests_Response ) {
+			$headers = $headers->get_headers();
+		}
+
+		if ( is_array( $headers ) || $headers instanceof Traversable ) {
+			foreach ( $headers as $name => $value ) {
+				$response = $response->withHeader( $name, $value );
+			}
+		}
+
+		if ( ! empty( $body ) ) {
+			$stream   = $this->stream_factory->createStream( $body );
+			$response = $response->withBody( $stream );
+		}
+
+		return $response;
+	}
+}
diff --git a/src/wp-includes/ai-client-utils/class-wp-ai-client-psr17-factory.php b/src/wp-includes/ai-client-utils/class-wp-ai-client-psr17-factory.php
new file mode 100644
index 0000000000000..3f6669d84297c
--- /dev/null
+++ b/src/wp-includes/ai-client-utils/class-wp-ai-client-psr17-factory.php
@@ -0,0 +1,115 @@
+<?php
+/**
+ * WP AI Client: WP_AI_Client_PSR17_Factory class
+ *
+ * @package WordPress
+ * @subpackage AI
+ * @since 7.0.0
+ */
+
+use WordPress\AiClientDependencies\Psr\Http\Message\RequestFactoryInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\RequestInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\ResponseFactoryInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\ResponseInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\StreamFactoryInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\StreamInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\UriFactoryInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\UriInterface;
+
+/**
+ * Combined PSR-17 factory for creating PSR-7 HTTP message objects.
+ *
+ * Implements all four PSR-17 factory interfaces, delegating to the minimal
+ * WP AI Client PSR-7 implementations.
+ *
+ * @since 7.0.0
+ */
+class WP_AI_Client_PSR17_Factory implements RequestFactoryInterface, ResponseFactoryInterface, StreamFactoryInterface, UriFactoryInterface {
+
+	/**
+	 * Creates a new request.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string              $method The HTTP method associated with the request.
+	 * @param UriInterface|string $uri    The URI associated with the request.
+	 * @return RequestInterface
+	 */
+	public function createRequest( string $method, $uri ): RequestInterface {
+		return new WP_AI_Client_PSR7_Request( $method, $uri );
+	}
+
+	/**
+	 * Creates a new response.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param int    $code         HTTP status code. Defaults to 200.
+	 * @param string $reasonPhrase Reason phrase to associate with status code.
+	 * @return ResponseInterface
+	 */
+	public function createResponse( int $code = 200, string $reasonPhrase = '' ): ResponseInterface {
+		return new WP_AI_Client_PSR7_Response( $code, $reasonPhrase );
+	}
+
+	/**
+	 * Creates a new stream from a string.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $content String content with which to populate the stream.
+	 * @return StreamInterface
+	 */
+	public function createStream( string $content = '' ): StreamInterface {
+		return new WP_AI_Client_PSR7_Stream( $content );
+	}
+
+	/**
+	 * Creates a stream from an existing file.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $filename Filename or stream URI to use as basis of stream.
+	 * @param string $mode     Mode with which to open the underlying filename/stream.
+	 * @return StreamInterface
+	 */
+	public function createStreamFromFile( string $filename, string $mode = 'r' ): StreamInterface {
+		$content = file_get_contents( $filename ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_get_contents_file_get_contents
+
+		if ( false === $content ) {
+			$content = '';
+		}
+
+		return new WP_AI_Client_PSR7_Stream( $content );
+	}
+
+	/**
+	 * Creates a new stream from an existing resource.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param resource $resource PHP resource to use as basis of stream.
+	 * @return StreamInterface
+	 */
+	public function createStreamFromResource( $resource ): StreamInterface {
+		$content = stream_get_contents( $resource );
+
+		if ( false === $content ) {
+			$content = '';
+		}
+
+		return new WP_AI_Client_PSR7_Stream( $content );
+	}
+
+	/**
+	 * Creates a new URI.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $uri The URI string.
+	 * @return UriInterface
+	 */
+	public function createUri( string $uri = '' ): UriInterface {
+		return new WP_AI_Client_PSR7_Uri( $uri );
+	}
+}
diff --git a/src/wp-includes/ai-client-utils/class-wp-ai-client-psr7-request.php b/src/wp-includes/ai-client-utils/class-wp-ai-client-psr7-request.php
new file mode 100644
index 0000000000000..1afc8ba87e974
--- /dev/null
+++ b/src/wp-includes/ai-client-utils/class-wp-ai-client-psr7-request.php
@@ -0,0 +1,384 @@
+<?php
+/**
+ * WP AI Client: WP_AI_Client_PSR7_Request class
+ *
+ * @package WordPress
+ * @subpackage AI
+ * @since 7.0.0
+ */
+
+use WordPress\AiClientDependencies\Psr\Http\Message\RequestInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\StreamInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\UriInterface;
+
+/**
+ * Minimal PSR-7 HTTP request implementation.
+ *
+ * Immutable value object representing an outgoing HTTP request for the AI Client
+ * HTTP transport layer.
+ *
+ * @since 7.0.0
+ */
+class WP_AI_Client_PSR7_Request implements RequestInterface {
+
+	/**
+	 * HTTP method.
+	 *
+	 * @since 7.0.0
+	 * @var string
+	 */
+	private $method;
+
+	/**
+	 * Request URI.
+	 *
+	 * @since 7.0.0
+	 * @var UriInterface
+	 */
+	private $uri;
+
+	/**
+	 * HTTP protocol version.
+	 *
+	 * @since 7.0.0
+	 * @var string
+	 */
+	private $protocol_version = '1.1';
+
+	/**
+	 * Headers indexed by lowercase name.
+	 *
+	 * Each value is an array with 'name' (original case) and 'values' (list of strings).
+	 *
+	 * @since 7.0.0
+	 * @var array<string, array{name: string, values: list<string>}>
+	 */
+	private $headers = array();
+
+	/**
+	 * Request body.
+	 *
+	 * @since 7.0.0
+	 * @var StreamInterface
+	 */
+	private $body;
+
+	/**
+	 * Explicit request target, if set.
+	 *
+	 * @since 7.0.0
+	 * @var string|null
+	 */
+	private $request_target;
+
+	/**
+	 * Constructor.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string              $method HTTP method.
+	 * @param string|UriInterface $uri    Request URI.
+	 */
+	public function __construct( string $method, $uri ) {
+		$this->method = $method;
+		$this->uri    = is_string( $uri ) ? new WP_AI_Client_PSR7_Uri( $uri ) : $uri;
+		$this->body   = new WP_AI_Client_PSR7_Stream();
+
+		$host = $this->uri->getHost();
+		if ( '' !== $host && ! $this->hasHeader( 'Host' ) ) {
+			$this->set_header_internal( 'Host', $host );
+		}
+	}
+
+	/**
+	 * Retrieves the HTTP protocol version.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return string HTTP protocol version.
+	 */
+	public function getProtocolVersion(): string {
+		return $this->protocol_version;
+	}
+
+	/**
+	 * Returns an instance with the specified HTTP protocol version.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $version HTTP protocol version.
+	 * @return static
+	 */
+	public function withProtocolVersion( string $version ): self {
+		$new                   = clone $this;
+		$new->protocol_version = $version;
+
+		return $new;
+	}
+
+	/**
+	 * Retrieves all message header values.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return string[][] Associative array of headers.
+	 */
+	public function getHeaders(): array {
+		$result = array();
+
+		foreach ( $this->headers as $entry ) {
+			$result[ $entry['name'] ] = $entry['values'];
+		}
+
+		return $result;
+	}
+
+	/**
+	 * Checks if a header exists by the given case-insensitive name.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $name Case-insensitive header field name.
+	 * @return bool
+	 */
+	public function hasHeader( string $name ): bool {
+		return isset( $this->headers[ strtolower( $name ) ] );
+	}
+
+	/**
+	 * Retrieves a message header value by the given case-insensitive name.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $name Case-insensitive header field name.
+	 * @return string[] Header values.
+	 */
+	public function getHeader( string $name ): array {
+		$normalized = strtolower( $name );
+
+		if ( ! isset( $this->headers[ $normalized ] ) ) {
+			return array();
+		}
+
+		return $this->headers[ $normalized ]['values'];
+	}
+
+	/**
+	 * Retrieves a comma-separated string of the values for a single header.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $name Case-insensitive header field name.
+	 * @return string
+	 */
+	public function getHeaderLine( string $name ): string {
+		return implode( ', ', $this->getHeader( $name ) );
+	}
+
+	/**
+	 * Returns an instance with the provided value replacing the specified header.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string          $name  Case-insensitive header field name.
+	 * @param string|string[] $value Header value(s).
+	 * @return static
+	 */
+	public function withHeader( string $name, $value ): self {
+		$new = clone $this;
+		$new->set_header_internal( $name, $value );
+
+		return $new;
+	}
+
+	/**
+	 * Returns an instance with the specified header appended with the given value.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string          $name  Case-insensitive header field name to add.
+	 * @param string|string[] $value Header value(s).
+	 * @return static
+	 */
+	public function withAddedHeader( string $name, $value ): self {
+		$new        = clone $this;
+		$normalized = strtolower( $name );
+		$values     = is_array( $value ) ? $value : array( $value );
+
+		if ( isset( $new->headers[ $normalized ] ) ) {
+			$new->headers[ $normalized ]['values'] = array_merge(
+				$new->headers[ $normalized ]['values'],
+				$values
+			);
+		} else {
+			$new->headers[ $normalized ] = array(
+				'name'   => $name,
+				'values' => $values,
+			);
+		}
+
+		return $new;
+	}
+
+	/**
+	 * Returns an instance without the specified header.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $name Case-insensitive header field name to remove.
+	 * @return static
+	 */
+	public function withoutHeader( string $name ): self {
+		$new = clone $this;
+		unset( $new->headers[ strtolower( $name ) ] );
+
+		return $new;
+	}
+
+	/**
+	 * Gets the body of the message.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return StreamInterface
+	 */
+	public function getBody(): StreamInterface {
+		return $this->body;
+	}
+
+	/**
+	 * Returns an instance with the specified message body.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param StreamInterface $body Body.
+	 * @return static
+	 */
+	public function withBody( StreamInterface $body ): self {
+		$new       = clone $this;
+		$new->body = $body;
+
+		return $new;
+	}
+
+	/**
+	 * Retrieves the message's request target.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return string
+	 */
+	public function getRequestTarget(): string {
+		if ( null !== $this->request_target ) {
+			return $this->request_target;
+		}
+
+		$target = $this->uri->getPath();
+
+		if ( '' === $target ) {
+			$target = '/';
+		}
+
+		$query = $this->uri->getQuery();
+
+		if ( '' !== $query ) {
+			$target .= '?' . $query;
+		}
+
+		return $target;
+	}
+
+	/**
+	 * Returns an instance with the specific request-target.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $requestTarget Request target.
+	 * @return static
+	 */
+	public function withRequestTarget( string $requestTarget ): self {
+		$new                 = clone $this;
+		$new->request_target = $requestTarget;
+
+		return $new;
+	}
+
+	/**
+	 * Retrieves the HTTP method of the request.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return string
+	 */
+	public function getMethod(): string {
+		return $this->method;
+	}
+
+	/**
+	 * Returns an instance with the provided HTTP method.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $method Case-sensitive method.
+	 * @return static
+	 */
+	public function withMethod( string $method ): self {
+		$new         = clone $this;
+		$new->method = $method;
+
+		return $new;
+	}
+
+	/**
+	 * Retrieves the URI instance.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return UriInterface
+	 */
+	public function getUri(): UriInterface {
+		return $this->uri;
+	}
+
+	/**
+	 * Returns an instance with the provided URI.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param UriInterface $uri          New request URI to use.
+	 * @param bool         $preserveHost Preserve the original state of the Host header.
+	 * @return static
+	 */
+	public function withUri( UriInterface $uri, bool $preserveHost = false ): self {
+		$new      = clone $this;
+		$new->uri = $uri;
+
+		$host = $uri->getHost();
+
+		if ( ! $preserveHost ) {
+			if ( '' !== $host ) {
+				$new->set_header_internal( 'Host', $host );
+			}
+		} elseif ( '' !== $host && ( ! $new->hasHeader( 'Host' ) || '' === $new->getHeaderLine( 'Host' ) ) ) {
+			$new->set_header_internal( 'Host', $host );
+		}
+
+		return $new;
+	}
+
+	/**
+	 * Sets a header internally (mutating, for use in constructor and clone methods).
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string          $name  Header name.
+	 * @param string|string[] $value Header value(s).
+	 */
+	private function set_header_internal( string $name, $value ): void {
+		$normalized                   = strtolower( $name );
+		$this->headers[ $normalized ] = array(
+			'name'   => $name,
+			'values' => is_array( $value ) ? $value : array( $value ),
+		);
+	}
+}
diff --git a/src/wp-includes/ai-client-utils/class-wp-ai-client-psr7-response.php b/src/wp-includes/ai-client-utils/class-wp-ai-client-psr7-response.php
new file mode 100644
index 0000000000000..eb84d2edd73ba
--- /dev/null
+++ b/src/wp-includes/ai-client-utils/class-wp-ai-client-psr7-response.php
@@ -0,0 +1,292 @@
+<?php
+/**
+ * WP AI Client: WP_AI_Client_PSR7_Response class
+ *
+ * @package WordPress
+ * @subpackage AI
+ * @since 7.0.0
+ */
+
+use WordPress\AiClientDependencies\Psr\Http\Message\ResponseInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\StreamInterface;
+
+/**
+ * Minimal PSR-7 HTTP response implementation.
+ *
+ * Immutable value object representing an incoming HTTP response for the AI Client
+ * HTTP transport layer.
+ *
+ * @since 7.0.0
+ */
+class WP_AI_Client_PSR7_Response implements ResponseInterface {
+
+	/**
+	 * HTTP status code.
+	 *
+	 * @since 7.0.0
+	 * @var int
+	 */
+	private $status_code;
+
+	/**
+	 * Reason phrase associated with the status code.
+	 *
+	 * @since 7.0.0
+	 * @var string
+	 */
+	private $reason_phrase;
+
+	/**
+	 * HTTP protocol version.
+	 *
+	 * @since 7.0.0
+	 * @var string
+	 */
+	private $protocol_version = '1.1';
+
+	/**
+	 * Headers indexed by lowercase name.
+	 *
+	 * Each value is an array with 'name' (original case) and 'values' (list of strings).
+	 *
+	 * @since 7.0.0
+	 * @var array<string, array{name: string, values: list<string>}>
+	 */
+	private $headers = array();
+
+	/**
+	 * Response body.
+	 *
+	 * @since 7.0.0
+	 * @var StreamInterface
+	 */
+	private $body;
+
+	/**
+	 * Constructor.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param int    $status_code   HTTP status code.
+	 * @param string $reason_phrase Reason phrase to associate with the status code.
+	 */
+	public function __construct( int $status_code = 200, string $reason_phrase = '' ) {
+		$this->status_code   = $status_code;
+		$this->reason_phrase = $reason_phrase;
+		$this->body          = new WP_AI_Client_PSR7_Stream();
+	}
+
+	/**
+	 * Gets the response status code.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return int Status code.
+	 */
+	public function getStatusCode(): int {
+		return $this->status_code;
+	}
+
+	/**
+	 * Returns an instance with the specified status code and reason phrase.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param int    $code         The 3-digit integer result code to set.
+	 * @param string $reasonPhrase The reason phrase to use.
+	 * @return static
+	 */
+	public function withStatus( int $code, string $reasonPhrase = '' ): self {
+		$new                = clone $this;
+		$new->status_code   = $code;
+		$new->reason_phrase = $reasonPhrase;
+
+		return $new;
+	}
+
+	/**
+	 * Gets the response reason phrase associated with the status code.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return string Reason phrase.
+	 */
+	public function getReasonPhrase(): string {
+		return $this->reason_phrase;
+	}
+
+	/**
+	 * Retrieves the HTTP protocol version.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return string HTTP protocol version.
+	 */
+	public function getProtocolVersion(): string {
+		return $this->protocol_version;
+	}
+
+	/**
+	 * Returns an instance with the specified HTTP protocol version.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $version HTTP protocol version.
+	 * @return static
+	 */
+	public function withProtocolVersion( string $version ): self {
+		$new                   = clone $this;
+		$new->protocol_version = $version;
+
+		return $new;
+	}
+
+	/**
+	 * Retrieves all message header values.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return string[][] Associative array of headers.
+	 */
+	public function getHeaders(): array {
+		$result = array();
+
+		foreach ( $this->headers as $entry ) {
+			$result[ $entry['name'] ] = $entry['values'];
+		}
+
+		return $result;
+	}
+
+	/**
+	 * Checks if a header exists by the given case-insensitive name.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $name Case-insensitive header field name.
+	 * @return bool
+	 */
+	public function hasHeader( string $name ): bool {
+		return isset( $this->headers[ strtolower( $name ) ] );
+	}
+
+	/**
+	 * Retrieves a message header value by the given case-insensitive name.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $name Case-insensitive header field name.
+	 * @return string[] Header values.
+	 */
+	public function getHeader( string $name ): array {
+		$normalized = strtolower( $name );
+
+		if ( ! isset( $this->headers[ $normalized ] ) ) {
+			return array();
+		}
+
+		return $this->headers[ $normalized ]['values'];
+	}
+
+	/**
+	 * Retrieves a comma-separated string of the values for a single header.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $name Case-insensitive header field name.
+	 * @return string
+	 */
+	public function getHeaderLine( string $name ): string {
+		return implode( ', ', $this->getHeader( $name ) );
+	}
+
+	/**
+	 * Returns an instance with the provided value replacing the specified header.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string          $name  Case-insensitive header field name.
+	 * @param string|string[] $value Header value(s).
+	 * @return static
+	 */
+	public function withHeader( string $name, $value ): self {
+		$new                         = clone $this;
+		$normalized                  = strtolower( $name );
+		$new->headers[ $normalized ] = array(
+			'name'   => $name,
+			'values' => is_array( $value ) ? $value : array( $value ),
+		);
+
+		return $new;
+	}
+
+	/**
+	 * Returns an instance with the specified header appended with the given value.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string          $name  Case-insensitive header field name to add.
+	 * @param string|string[] $value Header value(s).
+	 * @return static
+	 */
+	public function withAddedHeader( string $name, $value ): self {
+		$new        = clone $this;
+		$normalized = strtolower( $name );
+		$values     = is_array( $value ) ? $value : array( $value );
+
+		if ( isset( $new->headers[ $normalized ] ) ) {
+			$new->headers[ $normalized ]['values'] = array_merge(
+				$new->headers[ $normalized ]['values'],
+				$values
+			);
+		} else {
+			$new->headers[ $normalized ] = array(
+				'name'   => $name,
+				'values' => $values,
+			);
+		}
+
+		return $new;
+	}
+
+	/**
+	 * Returns an instance without the specified header.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $name Case-insensitive header field name to remove.
+	 * @return static
+	 */
+	public function withoutHeader( string $name ): self {
+		$new = clone $this;
+		unset( $new->headers[ strtolower( $name ) ] );
+
+		return $new;
+	}
+
+	/**
+	 * Gets the body of the message.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return StreamInterface
+	 */
+	public function getBody(): StreamInterface {
+		return $this->body;
+	}
+
+	/**
+	 * Returns an instance with the specified message body.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param StreamInterface $body Body.
+	 * @return static
+	 */
+	public function withBody( StreamInterface $body ): self {
+		$new       = clone $this;
+		$new->body = $body;
+
+		return $new;
+	}
+}
diff --git a/src/wp-includes/ai-client-utils/class-wp-ai-client-psr7-stream.php b/src/wp-includes/ai-client-utils/class-wp-ai-client-psr7-stream.php
new file mode 100644
index 0000000000000..5ba6395e45754
--- /dev/null
+++ b/src/wp-includes/ai-client-utils/class-wp-ai-client-psr7-stream.php
@@ -0,0 +1,243 @@
+<?php
+/**
+ * WP AI Client: WP_AI_Client_PSR7_Stream class
+ *
+ * @package WordPress
+ * @subpackage AI
+ * @since 7.0.0
+ */
+
+use WordPress\AiClientDependencies\Psr\Http\Message\StreamInterface;
+
+/**
+ * Minimal string-backed PSR-7 stream implementation.
+ *
+ * Provides the StreamInterface methods needed by the AI Client HTTP transport
+ * layer without requiring PHP stream resources.
+ *
+ * @since 7.0.0
+ */
+class WP_AI_Client_PSR7_Stream implements StreamInterface {
+
+	/**
+	 * The string content of the stream.
+	 *
+	 * @since 7.0.0
+	 * @var string
+	 */
+	private $content;
+
+	/**
+	 * Current read/write offset position.
+	 *
+	 * @since 7.0.0
+	 * @var int
+	 */
+	private $offset = 0;
+
+	/**
+	 * Constructor.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $content Initial content for the stream.
+	 */
+	public function __construct( string $content = '' ) {
+		$this->content = $content;
+	}
+
+	/**
+	 * Reads all data from the stream into a string.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return string
+	 */
+	public function __toString(): string {
+		return $this->content;
+	}
+
+	/**
+	 * Closes the stream. No-op for string-backed streams.
+	 *
+	 * @since 7.0.0
+	 */
+	public function close(): void {
+		// No-op.
+	}
+
+	/**
+	 * Separates any underlying resources from the stream.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return resource|null Always null for string-backed streams.
+	 */
+	public function detach() {
+		return null;
+	}
+
+	/**
+	 * Gets the size of the stream.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return int|null The size in bytes.
+	 */
+	public function getSize(): ?int {
+		return strlen( $this->content );
+	}
+
+	/**
+	 * Returns the current position of the read/write pointer.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return int Position of the pointer.
+	 */
+	public function tell(): int {
+		return $this->offset;
+	}
+
+	/**
+	 * Returns true if the stream is at the end.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return bool
+	 */
+	public function eof(): bool {
+		return $this->offset >= strlen( $this->content );
+	}
+
+	/**
+	 * Returns whether the stream is seekable.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return bool Always true.
+	 */
+	public function isSeekable(): bool {
+		return true;
+	}
+
+	/**
+	 * Seeks to a position in the stream.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param int $offset Stream offset.
+	 * @param int $whence One of SEEK_SET, SEEK_CUR, or SEEK_END.
+	 */
+	public function seek( int $offset, int $whence = SEEK_SET ): void {
+		$length = strlen( $this->content );
+
+		switch ( $whence ) {
+			case SEEK_SET:
+				$this->offset = $offset;
+				break;
+			case SEEK_CUR:
+				$this->offset += $offset;
+				break;
+			case SEEK_END:
+				$this->offset = $length + $offset;
+				break;
+		}
+
+		if ( $this->offset < 0 ) {
+			$this->offset = 0;
+		}
+	}
+
+	/**
+	 * Seeks to the beginning of the stream.
+	 *
+	 * @since 7.0.0
+	 */
+	public function rewind(): void {
+		$this->offset = 0;
+	}
+
+	/**
+	 * Returns whether the stream is writable.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return bool Always true.
+	 */
+	public function isWritable(): bool {
+		return true;
+	}
+
+	/**
+	 * Writes data to the stream.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $string The string to write.
+	 * @return int Number of bytes written.
+	 */
+	public function write( string $string ): int {
+		$this->content .= $string;
+		$length         = strlen( $string );
+		$this->offset  += $length;
+
+		return $length;
+	}
+
+	/**
+	 * Returns whether the stream is readable.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return bool Always true.
+	 */
+	public function isReadable(): bool {
+		return true;
+	}
+
+	/**
+	 * Reads data from the stream.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param int $length Number of bytes to read.
+	 * @return string Data read from the stream.
+	 */
+	public function read( int $length ): string {
+		$data          = substr( $this->content, $this->offset, $length );
+		$this->offset += strlen( $data );
+
+		return $data;
+	}
+
+	/**
+	 * Returns the remaining contents of the stream.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return string
+	 */
+	public function getContents(): string {
+		$remaining    = substr( $this->content, $this->offset );
+		$this->offset = strlen( $this->content );
+
+		return $remaining;
+	}
+
+	/**
+	 * Gets stream metadata.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string|null $key Specific metadata to retrieve.
+	 * @return array|mixed|null Returns null for specific keys, empty array otherwise.
+	 */
+	public function getMetadata( ?string $key = null ) {
+		if ( null !== $key ) {
+			return null;
+		}
+
+		return array();
+	}
+}
diff --git a/src/wp-includes/ai-client-utils/class-wp-ai-client-psr7-uri.php b/src/wp-includes/ai-client-utils/class-wp-ai-client-psr7-uri.php
new file mode 100644
index 0000000000000..58dfb364d469b
--- /dev/null
+++ b/src/wp-includes/ai-client-utils/class-wp-ai-client-psr7-uri.php
@@ -0,0 +1,389 @@
+<?php
+/**
+ * WP AI Client: WP_AI_Client_PSR7_Uri class
+ *
+ * @package WordPress
+ * @subpackage AI
+ * @since 7.0.0
+ */
+
+use WordPress\AiClientDependencies\Psr\Http\Message\UriInterface;
+
+/**
+ * Minimal PSR-7 URI implementation.
+ *
+ * Wraps PHP's parse_url() components into an immutable UriInterface value object.
+ *
+ * @since 7.0.0
+ */
+class WP_AI_Client_PSR7_Uri implements UriInterface {
+
+	/**
+	 * Standard ports for HTTP and HTTPS.
+	 *
+	 * @since 7.0.0
+	 * @var array<string, int>
+	 */
+	private static $default_ports = array(
+		'http'  => 80,
+		'https' => 443,
+	);
+
+	/**
+	 * URI scheme (e.g. "http", "https").
+	 *
+	 * @since 7.0.0
+	 * @var string
+	 */
+	private $scheme = '';
+
+	/**
+	 * URI user info (e.g. "user:password").
+	 *
+	 * @since 7.0.0
+	 * @var string
+	 */
+	private $user_info = '';
+
+	/**
+	 * URI host.
+	 *
+	 * @since 7.0.0
+	 * @var string
+	 */
+	private $host = '';
+
+	/**
+	 * URI port.
+	 *
+	 * @since 7.0.0
+	 * @var int|null
+	 */
+	private $port;
+
+	/**
+	 * URI path.
+	 *
+	 * @since 7.0.0
+	 * @var string
+	 */
+	private $path = '';
+
+	/**
+	 * URI query string.
+	 *
+	 * @since 7.0.0
+	 * @var string
+	 */
+	private $query = '';
+
+	/**
+	 * URI fragment.
+	 *
+	 * @since 7.0.0
+	 * @var string
+	 */
+	private $fragment = '';
+
+	/**
+	 * Constructor.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $uri URI string to parse.
+	 */
+	public function __construct( string $uri = '' ) {
+		if ( '' !== $uri ) {
+			$parts = wp_parse_url( $uri );
+
+			if ( false !== $parts ) {
+				$this->scheme = isset( $parts['scheme'] ) ? strtolower( $parts['scheme'] ) : '';
+				$this->host   = isset( $parts['host'] ) ? strtolower( $parts['host'] ) : '';
+				$this->port   = isset( $parts['port'] ) ? (int) $parts['port'] : null;
+				$this->path   = $parts['path'] ?? '';
+				$this->query  = $parts['query'] ?? '';
+
+				$this->fragment = $parts['fragment'] ?? '';
+
+				if ( isset( $parts['user'] ) ) {
+					$this->user_info = $parts['user'];
+					if ( isset( $parts['pass'] ) ) {
+						$this->user_info .= ':' . $parts['pass'];
+					}
+				}
+			}
+		}
+	}
+
+	/**
+	 * Retrieves the scheme component of the URI.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return string The URI scheme.
+	 */
+	public function getScheme(): string {
+		return $this->scheme;
+	}
+
+	/**
+	 * Retrieves the authority component of the URI.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return string The URI authority, in "[user-info@]host[:port]" format.
+	 */
+	public function getAuthority(): string {
+		if ( '' === $this->host ) {
+			return '';
+		}
+
+		$authority = $this->host;
+
+		if ( '' !== $this->user_info ) {
+			$authority = $this->user_info . '@' . $authority;
+		}
+
+		if ( null !== $this->port && ! $this->is_standard_port() ) {
+			$authority .= ':' . $this->port;
+		}
+
+		return $authority;
+	}
+
+	/**
+	 * Retrieves the user information component of the URI.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return string The URI user information.
+	 */
+	public function getUserInfo(): string {
+		return $this->user_info;
+	}
+
+	/**
+	 * Retrieves the host component of the URI.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return string The URI host.
+	 */
+	public function getHost(): string {
+		return $this->host;
+	}
+
+	/**
+	 * Retrieves the port component of the URI.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return int|null The URI port, or null if standard or not set.
+	 */
+	public function getPort(): ?int {
+		if ( $this->is_standard_port() ) {
+			return null;
+		}
+
+		return $this->port;
+	}
+
+	/**
+	 * Retrieves the path component of the URI.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return string The URI path.
+	 */
+	public function getPath(): string {
+		return $this->path;
+	}
+
+	/**
+	 * Retrieves the query string of the URI.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return string The URI query string.
+	 */
+	public function getQuery(): string {
+		return $this->query;
+	}
+
+	/**
+	 * Retrieves the fragment component of the URI.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return string The URI fragment.
+	 */
+	public function getFragment(): string {
+		return $this->fragment;
+	}
+
+	/**
+	 * Returns an instance with the specified scheme.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $scheme The scheme to use with the new instance.
+	 * @return static A new instance with the specified scheme.
+	 */
+	public function withScheme( string $scheme ): UriInterface {
+		$new         = clone $this;
+		$new->scheme = strtolower( $scheme );
+
+		return $new;
+	}
+
+	/**
+	 * Returns an instance with the specified user information.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string      $user     The user name to use for authority.
+	 * @param string|null $password The password associated with $user.
+	 * @return static A new instance with the specified user information.
+	 */
+	public function withUserInfo( string $user, ?string $password = null ): UriInterface {
+		$new            = clone $this;
+		$new->user_info = $user;
+
+		if ( null !== $password && '' !== $password ) {
+			$new->user_info .= ':' . $password;
+		}
+
+		return $new;
+	}
+
+	/**
+	 * Returns an instance with the specified host.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $host The hostname to use with the new instance.
+	 * @return static A new instance with the specified host.
+	 */
+	public function withHost( string $host ): UriInterface {
+		$new       = clone $this;
+		$new->host = strtolower( $host );
+
+		return $new;
+	}
+
+	/**
+	 * Returns an instance with the specified port.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param int|null $port The port to use with the new instance.
+	 * @return static A new instance with the specified port.
+	 */
+	public function withPort( ?int $port ): UriInterface {
+		$new       = clone $this;
+		$new->port = $port;
+
+		return $new;
+	}
+
+	/**
+	 * Returns an instance with the specified path.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $path The path to use with the new instance.
+	 * @return static A new instance with the specified path.
+	 */
+	public function withPath( string $path ): UriInterface {
+		$new       = clone $this;
+		$new->path = $path;
+
+		return $new;
+	}
+
+	/**
+	 * Returns an instance with the specified query string.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $query The query string to use with the new instance.
+	 * @return static A new instance with the specified query string.
+	 */
+	public function withQuery( string $query ): UriInterface {
+		$new        = clone $this;
+		$new->query = $query;
+
+		return $new;
+	}
+
+	/**
+	 * Returns an instance with the specified URI fragment.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $fragment The fragment to use with the new instance.
+	 * @return static A new instance with the specified fragment.
+	 */
+	public function withFragment( string $fragment ): UriInterface {
+		$new           = clone $this;
+		$new->fragment = $fragment;
+
+		return $new;
+	}
+
+	/**
+	 * Returns the string representation as a URI reference.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return string
+	 */
+	public function __toString(): string {
+		$uri       = '';
+		$authority = $this->getAuthority();
+
+		if ( '' !== $this->scheme ) {
+			$uri .= $this->scheme . ':';
+		}
+
+		if ( '' !== $authority ) {
+			$uri .= '//' . $authority;
+		}
+
+		$path = $this->path;
+
+		if ( '' !== $authority && ( '' === $path || '/' !== $path[0] ) ) {
+			$path = '/' . $path;
+		} elseif ( '' === $authority && str_starts_with( $path, '//' ) ) {
+			$path = '/' . ltrim( $path, '/' );
+		}
+
+		$uri .= $path;
+
+		if ( '' !== $this->query ) {
+			$uri .= '?' . $this->query;
+		}
+
+		if ( '' !== $this->fragment ) {
+			$uri .= '#' . $this->fragment;
+		}
+
+		return $uri;
+	}
+
+	/**
+	 * Checks whether the current port is the standard port for the scheme.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @return bool True if port is the standard port for the current scheme.
+	 */
+	private function is_standard_port(): bool {
+		if ( null === $this->port ) {
+			return false;
+		}
+
+		return isset( self::$default_ports[ $this->scheme ] )
+			&& self::$default_ports[ $this->scheme ] === $this->port;
+	}
+}
diff --git a/src/wp-includes/ai-client.php b/src/wp-includes/ai-client.php
new file mode 100644
index 0000000000000..1ceccbbb35d77
--- /dev/null
+++ b/src/wp-includes/ai-client.php
@@ -0,0 +1,22 @@
+<?php
+/**
+ * WordPress AI Client API.
+ *
+ * @package WordPress
+ * @subpackage AI
+ * @since 7.0.0
+ */
+
+use WordPress\AiClient\AiClient;
+
+/**
+ * Creates a new AI prompt builder using the default provider registry.
+ *
+ * @since 7.0.0
+ *
+ * @param mixed $prompt Optional. Initial prompt content. Default null.
+ * @return WP_AI_Client_Prompt_Builder The prompt builder instance.
+ */
+function wp_ai_client_prompt( $prompt = null ) {
+	return new WP_AI_Client_Prompt_Builder( AiClient::defaultRegistry(), $prompt );
+}
diff --git a/src/wp-includes/class-wp-ai-client-prompt-builder.php b/src/wp-includes/class-wp-ai-client-prompt-builder.php
new file mode 100644
index 0000000000000..e4a7c656ffdda
--- /dev/null
+++ b/src/wp-includes/class-wp-ai-client-prompt-builder.php
@@ -0,0 +1,379 @@
+<?php
+/**
+ * WP AI Client: WP_AI_Client_Prompt_Builder class
+ *
+ * @package WordPress
+ * @subpackage AI
+ * @since 7.0.0
+ */
+
+use WordPress\AiClient\Builders\PromptBuilder;
+use WordPress\AiClient\Files\DTO\File;
+use WordPress\AiClient\Files\Enums\FileTypeEnum;
+use WordPress\AiClient\Messages\DTO\Message;
+use WordPress\AiClient\Messages\DTO\MessagePart;
+use WordPress\AiClient\Messages\Enums\ModalityEnum;
+use WordPress\AiClient\Providers\Http\DTO\RequestOptions;
+use WordPress\AiClient\Providers\Models\Contracts\ModelInterface;
+use WordPress\AiClient\Providers\Models\DTO\ModelConfig;
+use WordPress\AiClient\Providers\Models\Enums\CapabilityEnum;
+use WordPress\AiClient\Providers\ProviderRegistry;
+use WordPress\AiClient\Results\DTO\GenerativeAiResult;
+use WordPress\AiClient\Tools\DTO\FunctionDeclaration;
+use WordPress\AiClient\Tools\DTO\FunctionResponse;
+use WordPress\AiClient\Tools\DTO\WebSearch;
+
+/**
+ * Fluent builder for constructing AI prompts, returning WP_Error on failure.
+ *
+ * This class provides a fluent interface for building prompts with various
+ * content types and model configurations. It wraps the PHP AI Client SDK's
+ * PromptBuilder and adds WordPress-specific behavior including WP_Error
+ * handling instead of exceptions, snake_case method naming, and integration
+ * with the Abilities API.
+ *
+ * Only the generating methods will return a WP_Error, to not break the fluent
+ * interface. As soon as any exception is caught in a chain of method calls,
+ * the returned instance will be in an error state, and all subsequent method
+ * calls will be no-ops that just return the same error state instance. Only
+ * when a generating method is called, the WP_Error will be returned.
+ *
+ * @since 7.0.0
+ *
+ * @method self with_text(string $text) Adds text to the current message.
+ * @method self with_file($file, ?string $mimeType = null) Adds a file to the current message.
+ * @method self with_function_response(FunctionResponse $functionResponse) Adds a function response to the current message.
+ * @method self with_message_parts(MessagePart ...$parts) Adds message parts to the current message.
+ * @method self with_history(Message ...$messages) Adds conversation history messages.
+ * @method self using_model(ModelInterface $model) Sets the model to use for generation.
+ * @method self using_model_preference(...$preferredModels) Sets preferred models to evaluate in order.
+ * @method self using_model_config(ModelConfig $config) Sets the model configuration.
+ * @method self using_provider(string $providerIdOrClassName) Sets the provider to use for generation.
+ * @method self using_system_instruction(string $systemInstruction) Sets the system instruction.
+ * @method self using_max_tokens(int $maxTokens) Sets the maximum number of tokens to generate.
+ * @method self using_temperature(float $temperature) Sets the temperature for generation.
+ * @method self using_top_p(float $topP) Sets the top-p value for generation.
+ * @method self using_top_k(int $topK) Sets the top-k value for generation.
+ * @method self using_stop_sequences(string ...$stopSequences) Sets stop sequences for generation.
+ * @method self using_candidate_count(int $candidateCount) Sets the number of candidates to generate.
+ * @method self using_function_declarations(FunctionDeclaration ...$functionDeclarations) Sets the function declarations available to the model.
+ * @method self using_presence_penalty(float $presencePenalty) Sets the presence penalty for generation.
+ * @method self using_frequency_penalty(float $frequencyPenalty) Sets the frequency penalty for generation.
+ * @method self using_web_search(WebSearch $webSearch) Sets the web search configuration.
+ * @method self using_request_options(RequestOptions $options) Sets the request options for HTTP transport.
+ * @method self using_top_logprobs(?int $topLogprobs = null) Sets the top log probabilities configuration.
+ * @method self as_output_mime_type(string $mimeType) Sets the output MIME type.
+ * @method self as_output_schema(array<string, mixed> $schema) Sets the output schema.
+ * @method self as_output_modalities(ModalityEnum ...$modalities) Sets the output modalities.
+ * @method self as_output_file_type(FileTypeEnum $fileType) Sets the output file type.
+ * @method self as_json_response(?array<string, mixed> $schema = null) Configures the prompt for JSON response output.
+ * @method bool|WP_Error is_supported(?CapabilityEnum $capability = null) Checks if the prompt is supported for the given capability.
+ * @method bool is_supported_for_text_generation() Checks if the prompt is supported for text generation.
+ * @method bool is_supported_for_image_generation() Checks if the prompt is supported for image generation.
+ * @method bool is_supported_for_text_to_speech_conversion() Checks if the prompt is supported for text to speech conversion.
+ * @method bool is_supported_for_video_generation() Checks if the prompt is supported for video generation.
+ * @method bool is_supported_for_speech_generation() Checks if the prompt is supported for speech generation.
+ * @method bool is_supported_for_music_generation() Checks if the prompt is supported for music generation.
+ * @method bool is_supported_for_embedding_generation() Checks if the prompt is supported for embedding generation.
+ * @method GenerativeAiResult|WP_Error generate_result(?CapabilityEnum $capability = null) Generates a result from the prompt.
+ * @method GenerativeAiResult|WP_Error generate_text_result() Generates a text result from the prompt.
+ * @method GenerativeAiResult|WP_Error generate_image_result() Generates an image result from the prompt.
+ * @method GenerativeAiResult|WP_Error generate_speech_result() Generates a speech result from the prompt.
+ * @method GenerativeAiResult|WP_Error convert_text_to_speech_result() Converts text to speech and returns the result.
+ * @method string|WP_Error generate_text() Generates text from the prompt.
+ * @method list<string>|WP_Error generate_texts(?int $candidateCount = null) Generates multiple text candidates from the prompt.
+ * @method File|WP_Error generate_image() Generates an image from the prompt.
+ * @method list<File>|WP_Error generate_images(?int $candidateCount = null) Generates multiple images from the prompt.
+ * @method File|WP_Error convert_text_to_speech() Converts text to speech.
+ * @method list<File>|WP_Error convert_text_to_speeches(?int $candidateCount = null) Converts text to multiple speech outputs.
+ * @method File|WP_Error generate_speech() Generates speech from the prompt.
+ * @method list<File>|WP_Error generate_speeches(?int $candidateCount = null) Generates multiple speech outputs from the prompt.
+ */
+class WP_AI_Client_Prompt_Builder {
+
+	/**
+	 * Wrapped prompt builder instance from the PHP AI Client SDK.
+	 *
+	 * @since 7.0.0
+	 * @var PromptBuilder
+	 */
+	private PromptBuilder $builder;
+
+	/**
+	 * WordPress error instance, if any error occurred during method calls.
+	 *
+	 * @since 7.0.0
+	 * @var WP_Error|null
+	 */
+	private ?WP_Error $error = null;
+
+	/**
+	 * List of methods that generate a result from the prompt.
+	 *
+	 * Structured as a map for faster lookups.
+	 *
+	 * @since 7.0.0
+	 * @var array<string, bool>
+	 */
+	private static array $generating_methods = array(
+		'generate_result'               => true,
+		'generate_text_result'          => true,
+		'generate_image_result'         => true,
+		'generate_speech_result'        => true,
+		'convert_text_to_speech_result' => true,
+		'generate_text'                 => true,
+		'generate_texts'                => true,
+		'generate_image'                => true,
+		'generate_images'               => true,
+		'convert_text_to_speech'        => true,
+		'convert_text_to_speeches'      => true,
+		'generate_speech'               => true,
+		'generate_speeches'             => true,
+	);
+
+	/**
+	 * List of methods that check whether the prompt is supported.
+	 *
+	 * Structured as a map for faster lookups.
+	 *
+	 * @since 7.0.0
+	 * @var array<string, bool>
+	 */
+	private static array $support_check_methods = array(
+		'is_supported'                               => true,
+		'is_supported_for_text_generation'           => true,
+		'is_supported_for_image_generation'          => true,
+		'is_supported_for_text_to_speech_conversion' => true,
+		'is_supported_for_video_generation'          => true,
+		'is_supported_for_speech_generation'         => true,
+		'is_supported_for_music_generation'          => true,
+		'is_supported_for_embedding_generation'      => true,
+	);
+
+	/**
+	 * Constructor.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param ProviderRegistry $registry The provider registry for finding suitable models.
+	 * @param mixed            $prompt   Optional initial prompt content.
+	 */
+	public function __construct( ProviderRegistry $registry, $prompt = null ) {
+		$this->builder = new PromptBuilder( $registry, $prompt );
+
+		/**
+		 * Filters the default request timeout in seconds for AI Client HTTP requests.
+		 *
+		 * @since 7.0.0
+		 *
+		 * @param int $default_timeout The default timeout in seconds.
+		 */
+		$default_timeout = (int) apply_filters( 'wp_ai_client_default_request_timeout', 30 );
+
+		$this->builder->usingRequestOptions(
+			RequestOptions::fromArray(
+				array(
+					RequestOptions::KEY_TIMEOUT => $default_timeout,
+				)
+			)
+		);
+	}
+
+	/**
+	 * Registers WordPress abilities as function declarations for the AI model.
+	 *
+	 * Converts each WP_Ability to a FunctionDeclaration using the wpab__ prefix
+	 * naming convention and passes them to the underlying prompt builder.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param WP_Ability|string ...$abilities The abilities to register, either as WP_Ability objects or ability name strings.
+	 * @return self The current instance for method chaining.
+	 */
+	public function using_abilities( ...$abilities ): self {
+		$declarations = array();
+
+		foreach ( $abilities as $ability ) {
+			if ( is_string( $ability ) ) {
+				$ability = wp_get_ability( $ability );
+			}
+
+			if ( ! $ability instanceof WP_Ability ) {
+				continue;
+			}
+
+			$function_name = WP_AI_Client_Ability_Function_Resolver::ability_name_to_function_name( $ability->get_name() );
+			$input_schema  = $ability->get_input_schema();
+
+			$declarations[] = new FunctionDeclaration(
+				$function_name,
+				$ability->get_description(),
+				! empty( $input_schema ) ? $input_schema : null
+			);
+		}
+
+		if ( ! empty( $declarations ) ) {
+			return $this->using_function_declarations( ...$declarations );
+		}
+
+		return $this;
+	}
+
+	/**
+	 * Magic method to proxy snake_case method calls to their PHP AI Client camelCase counterparts.
+	 *
+	 * This allows WordPress developers to use snake_case naming conventions. It catches
+	 * any exceptions thrown, stores them, and returns a WP_Error when a terminate method
+	 * is called.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string            $name      The method name in snake_case.
+	 * @param array<int, mixed> $arguments The method arguments.
+	 * @return mixed The result of the method call.
+	 */
+	public function __call( string $name, array $arguments ) {
+		/*
+		 * If an error occurred in a previous method call, either return the error for terminate methods,
+		 * or return the same instance for other methods to maintain the fluent interface.
+		 */
+		if ( null !== $this->error ) {
+			if ( self::is_generating_method( $name ) ) {
+				return $this->error;
+			}
+			if ( self::is_support_check_method( $name ) ) {
+				return false;
+			}
+			return $this;
+		}
+
+		// Check if the prompt should be prevented for is_supported* and generate_*/convert_text_to_speech* methods.
+		if ( self::is_support_check_method( $name ) || self::is_generating_method( $name ) ) {
+			/**
+			 * Filters whether to prevent the prompt from being executed.
+			 *
+			 * @since 7.0.0
+			 *
+			 * @param bool                        $prevent Whether to prevent the prompt. Default false.
+			 * @param WP_AI_Client_Prompt_Builder $builder A clone of the prompt builder instance (read-only).
+			 */
+			$prevent = (bool) apply_filters( 'wp_ai_client_prevent_prompt', false, clone $this );
+
+			if ( $prevent ) {
+				// For is_supported* methods, return false.
+				if ( self::is_support_check_method( $name ) ) {
+					return false;
+				}
+
+				// For generate_* and convert_text_to_speech* methods, create a WP_Error.
+				$this->error = new WP_Error(
+					'prompt_prevented',
+					'Prompt execution was prevented by a filter.',
+					array(
+						'exception_class' => 'WP_AI_Client_Prompt_Prevented',
+					)
+				);
+
+				if ( self::is_generating_method( $name ) ) {
+					return $this->error;
+				}
+				return $this;
+			}
+		}
+
+		try {
+			$callable = $this->get_builder_callable( $name );
+			$result   = $callable( ...$arguments );
+
+			// If the result is a PromptBuilder, return the current instance to allow method chaining.
+			if ( $result instanceof PromptBuilder ) {
+				return $this;
+			}
+
+			return $result;
+		} catch ( Exception $e ) {
+			$this->error = new WP_Error(
+				'prompt_builder_error',
+				$e->getMessage(),
+				array(
+					'exception_class' => get_class( $e ),
+				)
+			);
+
+			if ( self::is_generating_method( $name ) ) {
+				return $this->error;
+			}
+			return $this;
+		}
+	}
+
+	/**
+	 * Checks if a method name is a support check method (is_supported*).
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $name The method name.
+	 * @return bool True if the method is a support check method, false otherwise.
+	 */
+	private static function is_support_check_method( string $name ): bool {
+		return isset( self::$support_check_methods[ $name ] );
+	}
+
+	/**
+	 * Checks if a method name is a generating method (generate_*, convert_text_to_speech*).
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $name The method name.
+	 * @return bool True if the method is a generating method, false otherwise.
+	 */
+	private static function is_generating_method( string $name ): bool {
+		return isset( self::$generating_methods[ $name ] );
+	}
+
+	/**
+	 * Retrieves a callable for a given PHP AI Client SDK prompt builder method name.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $name The method name in snake_case.
+	 * @return callable The callable for the specified method.
+	 *
+	 * @throws BadMethodCallException If the method does not exist.
+	 */
+	protected function get_builder_callable( string $name ): callable {
+		$camel_case_name = $this->snake_to_camel_case( $name );
+
+		if ( ! is_callable( array( $this->builder, $camel_case_name ) ) ) {
+			throw new BadMethodCallException(
+				sprintf(
+					'Method %s does not exist on %s',
+					$name, // phpcs:ignore WordPress.Security.EscapeOutput.ExceptionNotEscaped
+					get_class( $this->builder ) // phpcs:ignore WordPress.Security.EscapeOutput.ExceptionNotEscaped
+				)
+			);
+		}
+
+		return array( $this->builder, $camel_case_name );
+	}
+
+	/**
+	 * Converts snake_case to camelCase.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $snake_case The snake_case string.
+	 * @return string The camelCase string.
+	 */
+	private function snake_to_camel_case( string $snake_case ): string {
+		$parts = explode( '_', $snake_case );
+
+		$camel_case  = $parts[0];
+		$parts_count = count( $parts );
+		for ( $i = 1; $i < $parts_count; $i++ ) {
+			$camel_case .= ucfirst( $parts[ $i ] );
+		}
+
+		return $camel_case;
+	}
+}
diff --git a/src/wp-includes/php-ai-client/autoload.php b/src/wp-includes/php-ai-client/autoload.php
new file mode 100644
index 0000000000000..b4305ff4c7ed8
--- /dev/null
+++ b/src/wp-includes/php-ai-client/autoload.php
@@ -0,0 +1,48 @@
+<?php
+/**
+ * Autoloader for the bundled PHP AI Client library.
+ *
+ * This file is generated by tools/php-ai-client/installer.sh.
+ * Do not edit directly.
+ *
+ * @package WordPress
+ * @subpackage AI
+ * @since 7.0.0
+ */
+
+// Load polyfills (each function is guarded by function_exists).
+require_once __DIR__ . '/src/polyfills.php';
+
+spl_autoload_register(
+	static function ( $class_name ) {
+		// Namespace prefix for the AI client.
+		$client_prefix     = 'WordPress\\AiClient\\';
+		$client_prefix_len = 19; // strlen( 'WordPress\\AiClient\\' )
+
+		// Namespace prefix for scoped dependencies (includes Psr\*, Http\*, etc.).
+		$scoped_prefix     = 'WordPress\\AiClientDependencies\\';
+		$scoped_prefix_len = 31; // strlen( 'WordPress\\AiClientDependencies\\' )
+
+		$base_dir = __DIR__;
+
+		// 1. WordPress\AiClient\* → src/
+		if ( 0 === strncmp( $class_name, $client_prefix, $client_prefix_len ) ) {
+			$relative_class = substr( $class_name, $client_prefix_len );
+			$file           = $base_dir . '/src/' . str_replace( '\\', '/', $relative_class ) . '.php';
+			if ( file_exists( $file ) ) {
+				require $file;
+			}
+			return;
+		}
+
+		// 2. WordPress\AiClientDependencies\* → third-party/ (strip prefix).
+		if ( 0 === strncmp( $class_name, $scoped_prefix, $scoped_prefix_len ) ) {
+			$relative_class = substr( $class_name, $scoped_prefix_len );
+			$file           = $base_dir . '/third-party/' . str_replace( '\\', '/', $relative_class ) . '.php';
+			if ( file_exists( $file ) ) {
+				require $file;
+			}
+			return;
+		}
+	}
+);
diff --git a/src/wp-includes/php-ai-client/src/AiClient.php b/src/wp-includes/php-ai-client/src/AiClient.php
new file mode 100644
index 0000000000000..f851cfe82d5dc
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/AiClient.php
@@ -0,0 +1,367 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient;
+
+use WordPress\AiClientDependencies\Psr\EventDispatcher\EventDispatcherInterface;
+use WordPress\AiClientDependencies\Psr\SimpleCache\CacheInterface;
+use WordPress\AiClient\Builders\PromptBuilder;
+use WordPress\AiClient\Common\Exception\InvalidArgumentException;
+use WordPress\AiClient\Common\Exception\RuntimeException;
+use WordPress\AiClient\Providers\Contracts\ProviderAvailabilityInterface;
+use WordPress\AiClient\Providers\Contracts\ProviderInterface;
+use WordPress\AiClient\Providers\Models\Contracts\ModelInterface;
+use WordPress\AiClient\Providers\Models\DTO\ModelConfig;
+use WordPress\AiClient\Providers\ProviderRegistry;
+use WordPress\AiClient\Results\DTO\GenerativeAiResult;
+/**
+ * Main AI Client class providing both fluent and traditional APIs for AI operations.
+ *
+ * This class serves as the primary entry point for AI operations, offering:
+ * - Fluent API for easy-to-read chained method calls
+ * - Traditional API for array-based configuration (WordPress style)
+ * - Integration with provider registry for model discovery
+ * - Support for three model specification approaches
+ *
+ * All model requirements analysis and capability matching is handled
+ * automatically by the PromptBuilder, which provides intelligent model
+ * discovery based on prompt content and configuration.
+ *
+ * ## Model Specification Approaches
+ *
+ * ### 1. Specific Model Instance
+ * Use a specific ModelInterface instance when you know exactly which model to use:
+ * ```php
+ * $model = $registry->getProvider('openai')->getModel('gpt-4');
+ * $result = AiClient::generateTextResult('What is PHP?', $model);
+ * ```
+ *
+ * ### 2. ModelConfig for Auto-Discovery
+ * Use ModelConfig to specify requirements and let the system discover the best model:
+ * ```php
+ * $config = new ModelConfig();
+ * $config->setTemperature(0.7);
+ * $config->setMaxTokens(150);
+ *
+ * $result = AiClient::generateTextResult('What is PHP?', $config);
+ * ```
+ *
+ * ### 3. Automatic Discovery (Default)
+ * Pass null or omit the parameter for intelligent model discovery based on prompt content:
+ * ```php
+ * // System analyzes prompt and selects appropriate model automatically
+ * $result = AiClient::generateTextResult('What is PHP?');
+ * $imageResult = AiClient::generateImageResult('A sunset over mountains');
+ * ```
+ *
+ * ## Fluent API Examples
+ * ```php
+ * // Fluent API with automatic model discovery
+ * $result = AiClient::prompt('Generate an image of a sunset')
+ *     ->usingTemperature(0.7)
+ *     ->generateImageResult();
+ *
+ * // Fluent API with specific model
+ * $result = AiClient::prompt('What is PHP?')
+ *     ->usingModel($specificModel)
+ *     ->usingTemperature(0.5)
+ *     ->generateTextResult();
+ *
+ * // Fluent API with model configuration
+ * $result = AiClient::prompt('Explain quantum physics')
+ *     ->usingModelConfig($config)
+ *     ->generateTextResult();
+ * ```
+ *
+ * @since 0.1.0
+ *
+ * @phpstan-import-type Prompt from PromptBuilder
+ *
+ * phpcs:ignore Generic.Files.LineLength.TooLong
+ */
+class AiClient
+{
+    /**
+     * @var string The version of the AI Client.
+     */
+    public const VERSION = '0.4.1';
+    /**
+     * @var ProviderRegistry|null The default provider registry instance.
+     */
+    private static ?ProviderRegistry $defaultRegistry = null;
+    /**
+     * @var EventDispatcherInterface|null The event dispatcher for prompt lifecycle events.
+     */
+    private static ?EventDispatcherInterface $eventDispatcher = null;
+    /**
+     * @var CacheInterface|null The PSR-16 cache for storing and retrieving cached data.
+     */
+    private static ?CacheInterface $cache = null;
+    /**
+     * Gets the default provider registry instance.
+     *
+     * @since 0.1.0
+     *
+     * @return ProviderRegistry The default provider registry.
+     */
+    public static function defaultRegistry(): ProviderRegistry
+    {
+        if (self::$defaultRegistry === null) {
+            self::$defaultRegistry = new ProviderRegistry();
+        }
+        return self::$defaultRegistry;
+    }
+    /**
+     * Sets the event dispatcher for prompt lifecycle events.
+     *
+     * The event dispatcher will be used to dispatch BeforeGenerateResultEvent and
+     * AfterGenerateResultEvent during prompt generation.
+     *
+     * @since 0.4.0
+     *
+     * @param EventDispatcherInterface|null $dispatcher The event dispatcher, or null to disable.
+     * @return void
+     */
+    public static function setEventDispatcher(?EventDispatcherInterface $dispatcher): void
+    {
+        self::$eventDispatcher = $dispatcher;
+    }
+    /**
+     * Gets the event dispatcher for prompt lifecycle events.
+     *
+     * @since 0.4.0
+     *
+     * @return EventDispatcherInterface|null The event dispatcher, or null if not set.
+     */
+    public static function getEventDispatcher(): ?EventDispatcherInterface
+    {
+        return self::$eventDispatcher;
+    }
+    /**
+     * Sets the PSR-16 cache for storing and retrieving cached data.
+     *
+     * The cache can be used to store AI responses and other data to avoid
+     * redundant API calls and improve performance.
+     *
+     * @since 0.4.0
+     *
+     * @param CacheInterface|null $cache The PSR-16 cache instance, or null to disable caching.
+     * @return void
+     */
+    public static function setCache(?CacheInterface $cache): void
+    {
+        self::$cache = $cache;
+    }
+    /**
+     * Gets the PSR-16 cache instance.
+     *
+     * @since 0.4.0
+     *
+     * @return CacheInterface|null The cache instance, or null if not set.
+     */
+    public static function getCache(): ?CacheInterface
+    {
+        return self::$cache;
+    }
+    /**
+     * Checks if a provider is configured and available for use.
+     *
+     * Supports multiple input formats for developer convenience:
+     * - ProviderAvailabilityInterface: Direct availability check
+     * - string (provider ID): e.g., AiClient::isConfigured('openai')
+     * - string (class name): e.g., AiClient::isConfigured(OpenAiProvider::class)
+     *
+     * When using string input, this method leverages the ProviderRegistry's centralized
+     * dependency management, ensuring HttpTransporter and authentication are properly
+     * injected into availability instances.
+     *
+     * @since 0.1.0
+     * @since 0.2.0 Now supports being passed a provider ID or class name.
+     *
+     * @param ProviderAvailabilityInterface|string|class-string<ProviderInterface> $availabilityOrIdOrClassName
+     *        The provider availability instance, provider ID, or provider class name.
+     * @return bool True if the provider is configured and available, false otherwise.
+     */
+    public static function isConfigured($availabilityOrIdOrClassName): bool
+    {
+        // Handle direct ProviderAvailabilityInterface (backward compatibility)
+        if ($availabilityOrIdOrClassName instanceof ProviderAvailabilityInterface) {
+            return $availabilityOrIdOrClassName->isConfigured();
+        }
+        // Handle string input (provider ID or class name) via registry
+        if (is_string($availabilityOrIdOrClassName)) {
+            return self::defaultRegistry()->isProviderConfigured($availabilityOrIdOrClassName);
+        }
+        throw new \InvalidArgumentException('Parameter must be a ProviderAvailabilityInterface instance, provider ID string, or provider class name. ' . sprintf('Received: %s', is_object($availabilityOrIdOrClassName) ? get_class($availabilityOrIdOrClassName) : gettype($availabilityOrIdOrClassName)));
+    }
+    /**
+     * Creates a new prompt builder for fluent API usage.
+     *
+     * Returns a PromptBuilder instance configured with the specified or default registry.
+     * The traditional API methods in this class delegate to PromptBuilder
+     * for all generation logic.
+     *
+     * @since 0.1.0
+     *
+     * @param Prompt $prompt Optional initial prompt content.
+     * @param ProviderRegistry|null $registry Optional custom registry. If null, uses default.
+     * @return PromptBuilder The prompt builder instance.
+     */
+    public static function prompt($prompt = null, ?ProviderRegistry $registry = null): PromptBuilder
+    {
+        return new PromptBuilder($registry ?? self::defaultRegistry(), $prompt, self::$eventDispatcher);
+    }
+    /**
+     * Generates content using a unified API that automatically detects model capabilities.
+     *
+     * When no model is provided, this method delegates to PromptBuilder for intelligent
+     * model discovery based on prompt content and configuration. When a model is provided,
+     * it infers the capability from the model's interfaces and delegates to the capability-based method.
+     *
+     * @since 0.1.0
+     *
+     * @param Prompt $prompt The prompt content.
+     * @param ModelInterface|ModelConfig $modelOrConfig Specific model to use, or model configuration
+     *                                                  for auto-discovery.
+     * @param ProviderRegistry|null $registry Optional custom registry. If null, uses default.
+     * @return GenerativeAiResult The generation result.
+     *
+     * @throws \InvalidArgumentException If the provided model doesn't support any known generation type.
+     * @throws \RuntimeException If no suitable model can be found for the prompt.
+     */
+    public static function generateResult($prompt, $modelOrConfig, ?ProviderRegistry $registry = null): GenerativeAiResult
+    {
+        self::validateModelOrConfigParameter($modelOrConfig);
+        return self::getConfiguredPromptBuilder($prompt, $modelOrConfig, $registry)->generateResult();
+    }
+    /**
+     * Generates text using the traditional API approach.
+     *
+     * @since 0.1.0
+     *
+     * @param Prompt $prompt The prompt content.
+     * @param ModelInterface|ModelConfig|null $modelOrConfig Optional specific model to use,
+     *                                                        or model configuration for auto-discovery,
+     *                                                        or null for defaults.
+     * @param ProviderRegistry|null $registry Optional custom registry. If null, uses default.
+     * @return GenerativeAiResult The generation result.
+     *
+     * @throws \InvalidArgumentException If the prompt format is invalid.
+     * @throws \RuntimeException If no suitable model is found.
+     */
+    public static function generateTextResult($prompt, $modelOrConfig = null, ?ProviderRegistry $registry = null): GenerativeAiResult
+    {
+        self::validateModelOrConfigParameter($modelOrConfig);
+        return self::getConfiguredPromptBuilder($prompt, $modelOrConfig, $registry)->generateTextResult();
+    }
+    /**
+     * Generates an image using the traditional API approach.
+     *
+     * @since 0.1.0
+     *
+     * @param Prompt $prompt The prompt content.
+     * @param ModelInterface|ModelConfig|null $modelOrConfig Optional specific model to use,
+     *                                                        or model configuration for auto-discovery,
+     *                                                        or null for defaults.
+     * @param ProviderRegistry|null $registry Optional custom registry. If null, uses default.
+     * @return GenerativeAiResult The generation result.
+     *
+     * @throws \InvalidArgumentException If the prompt format is invalid.
+     * @throws \RuntimeException If no suitable model is found.
+     */
+    public static function generateImageResult($prompt, $modelOrConfig = null, ?ProviderRegistry $registry = null): GenerativeAiResult
+    {
+        self::validateModelOrConfigParameter($modelOrConfig);
+        return self::getConfiguredPromptBuilder($prompt, $modelOrConfig, $registry)->generateImageResult();
+    }
+    /**
+     * Converts text to speech using the traditional API approach.
+     *
+     * @since 0.1.0
+     *
+     * @param Prompt $prompt The prompt content.
+     * @param ModelInterface|ModelConfig|null $modelOrConfig Optional specific model to use,
+     *                                                        or model configuration for auto-discovery,
+     *                                                        or null for defaults.
+     * @param ProviderRegistry|null $registry Optional custom registry. If null, uses default.
+     * @return GenerativeAiResult The generation result.
+     *
+     * @throws \InvalidArgumentException If the prompt format is invalid.
+     * @throws \RuntimeException If no suitable model is found.
+     */
+    public static function convertTextToSpeechResult($prompt, $modelOrConfig = null, ?ProviderRegistry $registry = null): GenerativeAiResult
+    {
+        self::validateModelOrConfigParameter($modelOrConfig);
+        return self::getConfiguredPromptBuilder($prompt, $modelOrConfig, $registry)->convertTextToSpeechResult();
+    }
+    /**
+     * Generates speech using the traditional API approach.
+     *
+     * @since 0.1.0
+     *
+     * @param Prompt $prompt The prompt content.
+     * @param ModelInterface|ModelConfig|null $modelOrConfig Optional specific model to use,
+     *                                                        or model configuration for auto-discovery,
+     *                                                        or null for defaults.
+     * @param ProviderRegistry|null $registry Optional custom registry. If null, uses default.
+     * @return GenerativeAiResult The generation result.
+     *
+     * @throws \InvalidArgumentException If the prompt format is invalid.
+     * @throws \RuntimeException If no suitable model is found.
+     */
+    public static function generateSpeechResult($prompt, $modelOrConfig = null, ?ProviderRegistry $registry = null): GenerativeAiResult
+    {
+        self::validateModelOrConfigParameter($modelOrConfig);
+        return self::getConfiguredPromptBuilder($prompt, $modelOrConfig, $registry)->generateSpeechResult();
+    }
+    /**
+     * Creates a new message builder for fluent API usage.
+     *
+     * This method will be implemented once MessageBuilder is available.
+     * MessageBuilder will provide a fluent interface for constructing complex
+     * messages with multiple parts, attachments, and metadata.
+     *
+     * @since 0.1.0
+     *
+     * @param string|null $text Optional initial message text.
+     * @return object MessageBuilder instance (type will be updated when MessageBuilder is available).
+     *
+     * @throws \RuntimeException When MessageBuilder is not yet available.
+     */
+    public static function message(?string $text = null)
+    {
+        throw new RuntimeException('MessageBuilder is not yet available. This method depends on builder infrastructure. ' . 'Use direct generation methods (generateTextResult, generateImageResult, etc.) for now.');
+    }
+    /**
+     * Validates that parameter is ModelInterface, ModelConfig, or null.
+     *
+     * @param mixed $modelOrConfig The parameter to validate.
+     * @return void
+     * @throws \InvalidArgumentException If parameter is invalid type.
+     */
+    private static function validateModelOrConfigParameter($modelOrConfig): void
+    {
+        if ($modelOrConfig !== null && !$modelOrConfig instanceof ModelInterface && !$modelOrConfig instanceof ModelConfig) {
+            throw new InvalidArgumentException('Parameter must be a ModelInterface instance (specific model), ' . 'ModelConfig instance (for auto-discovery), or null (default auto-discovery). ' . sprintf('Received: %s', is_object($modelOrConfig) ? get_class($modelOrConfig) : gettype($modelOrConfig)));
+        }
+    }
+    /**
+     * Configures PromptBuilder based on model/config parameter type.
+     *
+     * @param Prompt $prompt The prompt content.
+     * @param ModelInterface|ModelConfig|null $modelOrConfig The model or config parameter.
+     * @param ProviderRegistry|null $registry Optional custom registry to use.
+     * @return PromptBuilder Configured prompt builder.
+     */
+    private static function getConfiguredPromptBuilder($prompt, $modelOrConfig, ?ProviderRegistry $registry = null): PromptBuilder
+    {
+        $builder = self::prompt($prompt, $registry);
+        if ($modelOrConfig instanceof ModelInterface) {
+            $builder->usingModel($modelOrConfig);
+        } elseif ($modelOrConfig instanceof ModelConfig) {
+            $builder->usingModelConfig($modelOrConfig);
+        }
+        // null case: use default model discovery
+        return $builder;
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Builders/MessageBuilder.php b/src/wp-includes/php-ai-client/src/Builders/MessageBuilder.php
new file mode 100644
index 0000000000000..cc02f77e75d5b
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Builders/MessageBuilder.php
@@ -0,0 +1,203 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Builders;
+
+use InvalidArgumentException;
+use WordPress\AiClient\Files\DTO\File;
+use WordPress\AiClient\Messages\DTO\Message;
+use WordPress\AiClient\Messages\DTO\MessagePart;
+use WordPress\AiClient\Messages\Enums\MessageRoleEnum;
+use WordPress\AiClient\Tools\DTO\FunctionCall;
+use WordPress\AiClient\Tools\DTO\FunctionResponse;
+/**
+ * Fluent builder for constructing AI messages.
+ *
+ * This class provides a fluent interface for building messages with various
+ * content types including text, files, function calls, and function responses.
+ *
+ * @since 0.2.0
+ *
+ * @phpstan-import-type MessagePartArrayShape from MessagePart
+ *
+ * @phpstan-type Input string|MessagePart|MessagePartArrayShape|File|FunctionCall|FunctionResponse|null
+ */
+class MessageBuilder
+{
+    /**
+     * @var MessageRoleEnum|null The role of the message sender.
+     */
+    protected ?MessageRoleEnum $role = null;
+    /**
+     * @var list<MessagePart> The parts that make up the message.
+     */
+    protected array $parts = [];
+    /**
+     * Constructor.
+     *
+     * @since 0.2.0
+     *
+     * @param Input $input Optional initial content.
+     * @param MessageRoleEnum|null $role Optional role.
+     */
+    public function __construct($input = null, ?MessageRoleEnum $role = null)
+    {
+        $this->role = $role;
+        if ($input === null) {
+            return;
+        }
+        // Handle different input types
+        if ($input instanceof MessagePart) {
+            $this->parts[] = $input;
+        } elseif (is_string($input)) {
+            $this->withText($input);
+        } elseif ($input instanceof File) {
+            $this->withFile($input);
+        } elseif ($input instanceof FunctionCall) {
+            $this->withFunctionCall($input);
+        } elseif ($input instanceof FunctionResponse) {
+            $this->withFunctionResponse($input);
+        } elseif (is_array($input) && MessagePart::isArrayShape($input)) {
+            $this->parts[] = MessagePart::fromArray($input);
+        } else {
+            throw new InvalidArgumentException('Input must be a string, MessagePart, MessagePartArrayShape, File, FunctionCall, or FunctionResponse.');
+        }
+    }
+    /**
+     * Sets the role of the message sender.
+     *
+     * @since 0.2.0
+     *
+     * @param MessageRoleEnum $role The role to set.
+     * @return self
+     */
+    public function usingRole(MessageRoleEnum $role): self
+    {
+        $this->role = $role;
+        return $this;
+    }
+    /**
+     * Sets the role to user.
+     *
+     * @since 0.2.0
+     *
+     * @return self
+     */
+    public function usingUserRole(): self
+    {
+        return $this->usingRole(MessageRoleEnum::user());
+    }
+    /**
+     * Sets the role to model.
+     *
+     * @since 0.2.0
+     *
+     * @return self
+     */
+    public function usingModelRole(): self
+    {
+        return $this->usingRole(MessageRoleEnum::model());
+    }
+    /**
+     * Adds text content to the message.
+     *
+     * @since 0.2.0
+     *
+     * @param string $text The text to add.
+     * @return self
+     * @throws InvalidArgumentException If the text is empty.
+     */
+    public function withText(string $text): self
+    {
+        if (trim($text) === '') {
+            throw new InvalidArgumentException('Text content cannot be empty.');
+        }
+        $this->parts[] = new MessagePart($text);
+        return $this;
+    }
+    /**
+     * Adds a file to the message.
+     *
+     * Accepts:
+     * - File object
+     * - URL string (remote file)
+     * - Base64-encoded data string
+     * - Data URI string (data:mime/type;base64,data)
+     * - Local file path string
+     *
+     * @since 0.2.0
+     *
+     * @param string|File $file The file to add.
+     * @param string|null $mimeType Optional MIME type (ignored if File object provided).
+     * @return self
+     * @throws InvalidArgumentException If the file is invalid.
+     */
+    public function withFile($file, ?string $mimeType = null): self
+    {
+        $file = $file instanceof File ? $file : new File($file, $mimeType);
+        $this->parts[] = new MessagePart($file);
+        return $this;
+    }
+    /**
+     * Adds a function call to the message.
+     *
+     * @since 0.2.0
+     *
+     * @param FunctionCall $functionCall The function call to add.
+     * @return self
+     */
+    public function withFunctionCall(FunctionCall $functionCall): self
+    {
+        $this->parts[] = new MessagePart($functionCall);
+        return $this;
+    }
+    /**
+     * Adds a function response to the message.
+     *
+     * @since 0.2.0
+     *
+     * @param FunctionResponse $functionResponse The function response to add.
+     * @return self
+     */
+    public function withFunctionResponse(FunctionResponse $functionResponse): self
+    {
+        $this->parts[] = new MessagePart($functionResponse);
+        return $this;
+    }
+    /**
+     * Adds multiple message parts to the message.
+     *
+     * @since 0.2.0
+     *
+     * @param MessagePart ...$parts The message parts to add.
+     * @return self
+     */
+    public function withMessageParts(MessagePart ...$parts): self
+    {
+        foreach ($parts as $part) {
+            $this->parts[] = $part;
+        }
+        return $this;
+    }
+    /**
+     * Builds and returns the Message object.
+     *
+     * @since 0.2.0
+     *
+     * @return Message The built message.
+     * @throws InvalidArgumentException If the message validation fails.
+     */
+    public function get(): Message
+    {
+        if (empty($this->parts)) {
+            throw new InvalidArgumentException('Cannot build an empty message. Add content using withText() or similar methods.');
+        }
+        if ($this->role === null) {
+            throw new InvalidArgumentException('Cannot build a message with no role. Set a role using usingRole() or similar methods.');
+        }
+        // At this point, we've validated that $this->role is not null
+        /** @var MessageRoleEnum $role */
+        $role = $this->role;
+        return new Message($role, $this->parts);
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Builders/PromptBuilder.php b/src/wp-includes/php-ai-client/src/Builders/PromptBuilder.php
new file mode 100644
index 0000000000000..6821b99280bd3
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Builders/PromptBuilder.php
@@ -0,0 +1,1343 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Builders;
+
+use WordPress\AiClientDependencies\Psr\EventDispatcher\EventDispatcherInterface;
+use WordPress\AiClient\Common\Exception\InvalidArgumentException;
+use WordPress\AiClient\Common\Exception\RuntimeException;
+use WordPress\AiClient\Events\AfterGenerateResultEvent;
+use WordPress\AiClient\Events\BeforeGenerateResultEvent;
+use WordPress\AiClient\Files\DTO\File;
+use WordPress\AiClient\Files\Enums\FileTypeEnum;
+use WordPress\AiClient\Messages\DTO\Message;
+use WordPress\AiClient\Messages\DTO\MessagePart;
+use WordPress\AiClient\Messages\DTO\UserMessage;
+use WordPress\AiClient\Messages\Enums\MessageRoleEnum;
+use WordPress\AiClient\Messages\Enums\ModalityEnum;
+use WordPress\AiClient\Providers\ApiBasedImplementation\Contracts\ApiBasedModelInterface;
+use WordPress\AiClient\Providers\Http\DTO\RequestOptions;
+use WordPress\AiClient\Providers\Models\Contracts\ModelInterface;
+use WordPress\AiClient\Providers\Models\DTO\ModelConfig;
+use WordPress\AiClient\Providers\Models\DTO\ModelMetadata;
+use WordPress\AiClient\Providers\Models\DTO\ModelRequirements;
+use WordPress\AiClient\Providers\Models\Enums\CapabilityEnum;
+use WordPress\AiClient\Providers\Models\ImageGeneration\Contracts\ImageGenerationModelInterface;
+use WordPress\AiClient\Providers\Models\SpeechGeneration\Contracts\SpeechGenerationModelInterface;
+use WordPress\AiClient\Providers\Models\TextGeneration\Contracts\TextGenerationModelInterface;
+use WordPress\AiClient\Providers\Models\TextToSpeechConversion\Contracts\TextToSpeechConversionModelInterface;
+use WordPress\AiClient\Providers\ProviderRegistry;
+use WordPress\AiClient\Results\DTO\GenerativeAiResult;
+use WordPress\AiClient\Tools\DTO\FunctionDeclaration;
+use WordPress\AiClient\Tools\DTO\FunctionResponse;
+use WordPress\AiClient\Tools\DTO\WebSearch;
+/**
+ * Fluent builder for constructing AI prompts.
+ *
+ * This class provides a fluent interface for building prompts with various
+ * content types and model configurations. It automatically infers model
+ * requirements based on the features used in the prompt.
+ *
+ * @since 0.1.0
+ *
+ * @phpstan-import-type MessageArrayShape from Message
+ * @phpstan-import-type MessagePartArrayShape from MessagePart
+ *
+ * @phpstan-type Prompt string|MessagePart|Message|MessageArrayShape|list<string|MessagePart|MessagePartArrayShape>|list<Message>|null
+ */
+class PromptBuilder
+{
+    /**
+     * @var ProviderRegistry The provider registry for finding suitable models.
+     */
+    private ProviderRegistry $registry;
+    /**
+     * @var list<Message> The messages in the conversation.
+     */
+    protected array $messages = [];
+    /**
+     * @var ModelInterface|null The model to use for generation.
+     */
+    protected ?ModelInterface $model = null;
+    /**
+     * @var list<string> Ordered list of preference keys to check when selecting a model.
+     */
+    protected array $modelPreferenceKeys = [];
+    /**
+     * @var string|null The provider ID or class name.
+     */
+    protected ?string $providerIdOrClassName = null;
+    /**
+     * @var ModelConfig The model configuration.
+     */
+    protected ModelConfig $modelConfig;
+    /**
+     * @var RequestOptions|null The request options for HTTP transport.
+     */
+    protected ?RequestOptions $requestOptions = null;
+    /**
+     * @var EventDispatcherInterface|null The event dispatcher for prompt lifecycle events.
+     */
+    private ?EventDispatcherInterface $eventDispatcher = null;
+    // phpcs:disable Generic.Files.LineLength.TooLong
+    /**
+     * Constructor.
+     *
+     * @since 0.1.0
+     *
+     * @param ProviderRegistry $registry The provider registry for finding suitable models.
+     * @param Prompt $prompt Optional initial prompt content.
+     * @param EventDispatcherInterface|null $eventDispatcher Optional event dispatcher for lifecycle events.
+     */
+    // phpcs:enable Generic.Files.LineLength.TooLong
+    public function __construct(ProviderRegistry $registry, $prompt = null, ?EventDispatcherInterface $eventDispatcher = null)
+    {
+        $this->registry = $registry;
+        $this->modelConfig = new ModelConfig();
+        $this->eventDispatcher = $eventDispatcher;
+        if ($prompt === null) {
+            return;
+        }
+        // Check if it's a list of Messages - set as messages
+        if ($this->isMessagesList($prompt)) {
+            $this->messages = $prompt;
+            return;
+        }
+        // Parse it as a user message
+        $userMessage = $this->parseMessage($prompt, MessageRoleEnum::user());
+        $this->messages[] = $userMessage;
+    }
+    /**
+     * Adds text to the current message.
+     *
+     * @since 0.1.0
+     *
+     * @param string $text The text to add.
+     * @return self
+     */
+    public function withText(string $text): self
+    {
+        $part = new MessagePart($text);
+        $this->appendPartToMessages($part);
+        return $this;
+    }
+    /**
+     * Adds a file to the current message.
+     *
+     * Accepts:
+     * - File object
+     * - URL string (remote file)
+     * - Base64-encoded data string
+     * - Data URI string (data:mime/type;base64,data)
+     * - Local file path string
+     *
+     * @since 0.1.0
+     *
+     * @param string|File $file The file (File object or string representation).
+     * @param string|null $mimeType The MIME type (optional, ignored if File object provided).
+     * @return self
+     * @throws InvalidArgumentException If the file is invalid or MIME type cannot be determined.
+     */
+    public function withFile($file, ?string $mimeType = null): self
+    {
+        $file = $file instanceof File ? $file : new File($file, $mimeType);
+        $part = new MessagePart($file);
+        $this->appendPartToMessages($part);
+        return $this;
+    }
+    /**
+     * Adds a function response to the current message.
+     *
+     * @since 0.1.0
+     *
+     * @param FunctionResponse $functionResponse The function response.
+     * @return self
+     */
+    public function withFunctionResponse(FunctionResponse $functionResponse): self
+    {
+        $part = new MessagePart($functionResponse);
+        $this->appendPartToMessages($part);
+        return $this;
+    }
+    /**
+     * Adds message parts to the current message.
+     *
+     * @since 0.1.0
+     *
+     * @param MessagePart ...$parts The message parts to add.
+     * @return self
+     */
+    public function withMessageParts(MessagePart ...$parts): self
+    {
+        foreach ($parts as $part) {
+            $this->appendPartToMessages($part);
+        }
+        return $this;
+    }
+    /**
+     * Adds conversation history messages.
+     *
+     * Historical messages are prepended to the beginning of the message list,
+     * before the current message being built.
+     *
+     * @since 0.1.0
+     *
+     * @param Message ...$messages The messages to add to history.
+     * @return self
+     */
+    public function withHistory(Message ...$messages): self
+    {
+        // Prepend the history messages to the beginning of the messages array
+        $this->messages = array_merge($messages, $this->messages);
+        return $this;
+    }
+    /**
+     * Sets the model to use for generation.
+     *
+     * The model's configuration will be merged with the builder's configuration,
+     * with the builder's configuration taking precedence for any overlapping settings.
+     *
+     * @since 0.1.0
+     *
+     * @param ModelInterface $model The model to use.
+     * @return self
+     */
+    public function usingModel(ModelInterface $model): self
+    {
+        $this->model = $model;
+        // Merge model's config with builder's config, with builder's config taking precedence
+        $modelConfigArray = $model->getConfig()->toArray();
+        $builderConfigArray = $this->modelConfig->toArray();
+        $mergedConfigArray = array_merge($modelConfigArray, $builderConfigArray);
+        $this->modelConfig = ModelConfig::fromArray($mergedConfigArray);
+        return $this;
+    }
+    /**
+     * Sets preferred models to evaluate in order.
+     *
+     * @since 0.2.0
+     *
+     * @param string|ModelInterface|array{0:string,1:string} ...$preferredModels The preferred models as model IDs,
+     * model instances, or [model ID, provider ID] tuples.
+     * @return self
+     *
+     * @throws InvalidArgumentException When a preferred model has an invalid type or identifier.
+     */
+    public function usingModelPreference(...$preferredModels): self
+    {
+        if ($preferredModels === []) {
+            throw new InvalidArgumentException('At least one model preference must be provided.');
+        }
+        $preferenceKeys = [];
+        foreach ($preferredModels as $preferredModel) {
+            if (is_array($preferredModel)) {
+                // [model identifier, provider ID] tuple
+                if (!array_is_list($preferredModel) || count($preferredModel) !== 2) {
+                    throw new InvalidArgumentException('Model preference tuple must contain model identifier and provider ID.');
+                }
+                [$providerId, $modelId] = $preferredModel;
+                $modelId = $this->normalizePreferenceIdentifier($modelId);
+                $providerId = $this->normalizePreferenceIdentifier($providerId, 'Model preference provider identifiers cannot be empty.');
+                $preferenceKey = $this->createProviderModelPreferenceKey($providerId, $modelId);
+            } elseif ($preferredModel instanceof ModelInterface) {
+                // Model instance
+                $modelId = $preferredModel->metadata()->getId();
+                $providerId = $preferredModel->providerMetadata()->getId();
+                $preferenceKey = $this->createProviderModelPreferenceKey($providerId, $modelId);
+            } elseif (is_string($preferredModel)) {
+                // Model ID
+                $modelId = $this->normalizePreferenceIdentifier($preferredModel);
+                $preferenceKey = $this->createModelPreferenceKey($modelId);
+            } else {
+                // Invalid type
+                throw new InvalidArgumentException('Model preferences must be model identifiers, instances of ModelInterface, ' . 'or provider/model tuples.');
+            }
+            $preferenceKeys[] = $preferenceKey;
+        }
+        $this->modelPreferenceKeys = $preferenceKeys;
+        return $this;
+    }
+    /**
+     * Sets the model configuration.
+     *
+     * Merges the provided configuration with the builder's configuration,
+     * with builder configuration taking precedence.
+     *
+     * @since 0.1.0
+     *
+     * @param ModelConfig $config The model configuration to merge.
+     * @return self
+     */
+    public function usingModelConfig(ModelConfig $config): self
+    {
+        // Convert both configs to arrays
+        $builderConfigArray = $this->modelConfig->toArray();
+        $providedConfigArray = $config->toArray();
+        // Merge arrays with builder config taking precedence
+        $mergedArray = array_merge($providedConfigArray, $builderConfigArray);
+        // Create new config from merged array
+        $this->modelConfig = ModelConfig::fromArray($mergedArray);
+        return $this;
+    }
+    /**
+     * Sets the provider to use for generation.
+     *
+     * @since 0.1.0
+     *
+     * @param string $providerIdOrClassName The provider ID or class name.
+     * @return self
+     */
+    public function usingProvider(string $providerIdOrClassName): self
+    {
+        $this->providerIdOrClassName = $providerIdOrClassName;
+        return $this;
+    }
+    /**
+     * Sets the system instruction.
+     *
+     * System instructions are stored in the model configuration and guide
+     * the AI model's behavior throughout the conversation.
+     *
+     * @since 0.1.0
+     *
+     * @param string $systemInstruction The system instruction text.
+     * @return self
+     */
+    public function usingSystemInstruction(string $systemInstruction): self
+    {
+        $this->modelConfig->setSystemInstruction($systemInstruction);
+        return $this;
+    }
+    /**
+     * Sets the maximum number of tokens to generate.
+     *
+     * @since 0.1.0
+     *
+     * @param int $maxTokens The maximum number of tokens.
+     * @return self
+     */
+    public function usingMaxTokens(int $maxTokens): self
+    {
+        $this->modelConfig->setMaxTokens($maxTokens);
+        return $this;
+    }
+    /**
+     * Sets the temperature for generation.
+     *
+     * @since 0.1.0
+     *
+     * @param float $temperature The temperature value.
+     * @return self
+     */
+    public function usingTemperature(float $temperature): self
+    {
+        $this->modelConfig->setTemperature($temperature);
+        return $this;
+    }
+    /**
+     * Sets the top-p value for generation.
+     *
+     * @since 0.1.0
+     *
+     * @param float $topP The top-p value.
+     * @return self
+     */
+    public function usingTopP(float $topP): self
+    {
+        $this->modelConfig->setTopP($topP);
+        return $this;
+    }
+    /**
+     * Sets the top-k value for generation.
+     *
+     * @since 0.1.0
+     *
+     * @param int $topK The top-k value.
+     * @return self
+     */
+    public function usingTopK(int $topK): self
+    {
+        $this->modelConfig->setTopK($topK);
+        return $this;
+    }
+    /**
+     * Sets stop sequences for generation.
+     *
+     * @since 0.1.0
+     *
+     * @param string ...$stopSequences The stop sequences.
+     * @return self
+     */
+    public function usingStopSequences(string ...$stopSequences): self
+    {
+        $this->modelConfig->setCustomOption('stopSequences', $stopSequences);
+        return $this;
+    }
+    /**
+     * Sets the number of candidates to generate.
+     *
+     * @since 0.1.0
+     *
+     * @param int $candidateCount The number of candidates.
+     * @return self
+     */
+    public function usingCandidateCount(int $candidateCount): self
+    {
+        $this->modelConfig->setCandidateCount($candidateCount);
+        return $this;
+    }
+    /**
+     * Sets the function declarations available to the model.
+     *
+     * @since 0.1.0
+     *
+     * @param FunctionDeclaration ...$functionDeclarations The function declarations.
+     * @return self
+     */
+    public function usingFunctionDeclarations(FunctionDeclaration ...$functionDeclarations): self
+    {
+        $this->modelConfig->setFunctionDeclarations($functionDeclarations);
+        return $this;
+    }
+    /**
+     * Sets the presence penalty for generation.
+     *
+     * @since 0.1.0
+     *
+     * @param float $presencePenalty The presence penalty value.
+     * @return self
+     */
+    public function usingPresencePenalty(float $presencePenalty): self
+    {
+        $this->modelConfig->setPresencePenalty($presencePenalty);
+        return $this;
+    }
+    /**
+     * Sets the frequency penalty for generation.
+     *
+     * @since 0.1.0
+     *
+     * @param float $frequencyPenalty The frequency penalty value.
+     * @return self
+     */
+    public function usingFrequencyPenalty(float $frequencyPenalty): self
+    {
+        $this->modelConfig->setFrequencyPenalty($frequencyPenalty);
+        return $this;
+    }
+    /**
+     * Sets the web search configuration.
+     *
+     * @since 0.1.0
+     *
+     * @param WebSearch $webSearch The web search configuration.
+     * @return self
+     */
+    public function usingWebSearch(WebSearch $webSearch): self
+    {
+        $this->modelConfig->setWebSearch($webSearch);
+        return $this;
+    }
+    /**
+     * Sets the request options for HTTP transport.
+     *
+     * @since 0.3.0
+     *
+     * @param RequestOptions $requestOptions The request options.
+     * @return self
+     */
+    public function usingRequestOptions(RequestOptions $requestOptions): self
+    {
+        $this->requestOptions = $requestOptions;
+        return $this;
+    }
+    /**
+     * Sets the top log probabilities configuration.
+     *
+     * If $topLogprobs is null, enables log probabilities.
+     * If $topLogprobs has a value, enables log probabilities and sets the number of top log probabilities to return.
+     *
+     * @since 0.1.0
+     *
+     * @param int|null $topLogprobs The number of top log probabilities to return, or null to enable log probabilities.
+     * @return self
+     */
+    public function usingTopLogprobs(?int $topLogprobs = null): self
+    {
+        // Always enable log probabilities
+        $this->modelConfig->setLogprobs(\true);
+        // If a specific number is provided, set it
+        if ($topLogprobs !== null) {
+            $this->modelConfig->setTopLogprobs($topLogprobs);
+        }
+        return $this;
+    }
+    /**
+     * Sets the output MIME type.
+     *
+     * @since 0.1.0
+     *
+     * @param string $mimeType The MIME type.
+     * @return self
+     */
+    public function asOutputMimeType(string $mimeType): self
+    {
+        $this->modelConfig->setOutputMimeType($mimeType);
+        return $this;
+    }
+    /**
+     * Sets the output schema.
+     *
+     * @since 0.1.0
+     *
+     * @param array<string, mixed> $schema The output schema.
+     * @return self
+     */
+    public function asOutputSchema(array $schema): self
+    {
+        $this->modelConfig->setOutputSchema($schema);
+        return $this;
+    }
+    /**
+     * Sets the output modalities.
+     *
+     * @since 0.1.0
+     *
+     * @param ModalityEnum ...$modalities The output modalities.
+     * @return self
+     */
+    public function asOutputModalities(ModalityEnum ...$modalities): self
+    {
+        $this->modelConfig->setOutputModalities($modalities);
+        return $this;
+    }
+    /**
+     * Sets the output file type.
+     *
+     * @since 0.1.0
+     *
+     * @param FileTypeEnum $fileType The output file type.
+     * @return self
+     */
+    public function asOutputFileType(FileTypeEnum $fileType): self
+    {
+        $this->modelConfig->setOutputFileType($fileType);
+        return $this;
+    }
+    /**
+     * Configures the prompt for JSON response output.
+     *
+     * @since 0.1.0
+     *
+     * @param array<string, mixed>|null $schema Optional JSON schema.
+     * @return self
+     */
+    public function asJsonResponse(?array $schema = null): self
+    {
+        $this->asOutputMimeType('application/json');
+        if ($schema !== null) {
+            $this->asOutputSchema($schema);
+        }
+        return $this;
+    }
+    /**
+     * Infers the capability from configured output modalities.
+     *
+     * @since 0.1.0
+     *
+     * @return CapabilityEnum The inferred capability.
+     * @throws RuntimeException If the output modality is not supported.
+     */
+    private function inferCapabilityFromOutputModalities(): CapabilityEnum
+    {
+        // Get the configured output modalities
+        $outputModalities = $this->modelConfig->getOutputModalities();
+        // Default to text if no output modality is specified
+        if ($outputModalities === null || empty($outputModalities)) {
+            return CapabilityEnum::textGeneration();
+        }
+        // Multi-modal output (multiple modalities) defaults to text generation. This is temporary
+        // as a multi-modal interface will be implemented in the future.
+        if (count($outputModalities) > 1) {
+            return CapabilityEnum::textGeneration();
+        }
+        // Infer capability from single output modality
+        $outputModality = $outputModalities[0];
+        if ($outputModality->isText()) {
+            return CapabilityEnum::textGeneration();
+        } elseif ($outputModality->isImage()) {
+            return CapabilityEnum::imageGeneration();
+        } elseif ($outputModality->isAudio()) {
+            return CapabilityEnum::speechGeneration();
+        } elseif ($outputModality->isVideo()) {
+            return CapabilityEnum::videoGeneration();
+        } else {
+            // For unsupported modalities, provide a clear error message
+            throw new RuntimeException(sprintf('Output modality "%s" is not yet supported.', $outputModality->value));
+        }
+    }
+    /**
+     * Infers the capability from a model's implemented interfaces.
+     *
+     * @since 0.1.0
+     *
+     * @param ModelInterface $model The model to infer capability from.
+     * @return CapabilityEnum|null The inferred capability, or null if none can be inferred.
+     */
+    private function inferCapabilityFromModelInterfaces(ModelInterface $model): ?CapabilityEnum
+    {
+        // Check model interfaces in order of preference
+        if ($model instanceof TextGenerationModelInterface) {
+            return CapabilityEnum::textGeneration();
+        }
+        if ($model instanceof ImageGenerationModelInterface) {
+            return CapabilityEnum::imageGeneration();
+        }
+        if ($model instanceof TextToSpeechConversionModelInterface) {
+            return CapabilityEnum::textToSpeechConversion();
+        }
+        if ($model instanceof SpeechGenerationModelInterface) {
+            return CapabilityEnum::speechGeneration();
+        }
+        // No supported interface found
+        return null;
+    }
+    /**
+     * Checks if the current prompt is supported by the selected model.
+     *
+     * @since 0.1.0
+     * @since 0.3.0 Method visibility changed to public.
+     *
+     * @param CapabilityEnum|null $capability Optional capability to check support for.
+     * @return bool True if supported, false otherwise.
+     */
+    public function isSupported(?CapabilityEnum $capability = null): bool
+    {
+        // If no intended capability provided, infer from output modalities
+        if ($capability === null) {
+            // First try to infer from a specific model if one is set
+            if ($this->model !== null) {
+                $inferredCapability = $this->inferCapabilityFromModelInterfaces($this->model);
+                if ($inferredCapability !== null) {
+                    $capability = $inferredCapability;
+                }
+            }
+            // If still no capability, infer from output modalities
+            if ($capability === null) {
+                $capability = $this->inferCapabilityFromOutputModalities();
+            }
+        }
+        // Build requirements with the specified capability
+        $requirements = ModelRequirements::fromPromptData($capability, $this->messages, $this->modelConfig);
+        // If the model has been set, check if it meets the requirements
+        if ($this->model !== null) {
+            return $requirements->areMetBy($this->model->metadata());
+        }
+        try {
+            // Check if any models support these requirements
+            $models = $this->registry->findModelsMetadataForSupport($requirements);
+            return !empty($models);
+        } catch (InvalidArgumentException $e) {
+            // No models support the requirements
+            return \false;
+        }
+    }
+    /**
+     * Checks if the prompt is supported for text generation.
+     *
+     * @since 0.1.0
+     *
+     * @return bool True if text generation is supported.
+     */
+    public function isSupportedForTextGeneration(): bool
+    {
+        return $this->isSupported(CapabilityEnum::textGeneration());
+    }
+    /**
+     * Checks if the prompt is supported for image generation.
+     *
+     * @since 0.1.0
+     *
+     * @return bool True if image generation is supported.
+     */
+    public function isSupportedForImageGeneration(): bool
+    {
+        return $this->isSupported(CapabilityEnum::imageGeneration());
+    }
+    /**
+     * Checks if the prompt is supported for text to speech conversion.
+     *
+     * @since 0.1.0
+     *
+     * @return bool True if text to speech conversion is supported.
+     */
+    public function isSupportedForTextToSpeechConversion(): bool
+    {
+        return $this->isSupported(CapabilityEnum::textToSpeechConversion());
+    }
+    /**
+     * Checks if the prompt is supported for video generation.
+     *
+     * @since 0.1.0
+     *
+     * @return bool True if video generation is supported.
+     */
+    public function isSupportedForVideoGeneration(): bool
+    {
+        return $this->isSupported(CapabilityEnum::videoGeneration());
+    }
+    /**
+     * Checks if the prompt is supported for speech generation.
+     *
+     * @since 0.1.0
+     *
+     * @return bool True if speech generation is supported.
+     */
+    public function isSupportedForSpeechGeneration(): bool
+    {
+        return $this->isSupported(CapabilityEnum::speechGeneration());
+    }
+    /**
+     * Checks if the prompt is supported for music generation.
+     *
+     * @since 0.1.0
+     *
+     * @return bool True if music generation is supported.
+     */
+    public function isSupportedForMusicGeneration(): bool
+    {
+        return $this->isSupported(CapabilityEnum::musicGeneration());
+    }
+    /**
+     * Checks if the prompt is supported for embedding generation.
+     *
+     * @since 0.1.0
+     *
+     * @return bool True if embedding generation is supported.
+     */
+    public function isSupportedForEmbeddingGeneration(): bool
+    {
+        return $this->isSupported(CapabilityEnum::embeddingGeneration());
+    }
+    /**
+     * Generates a result from the prompt.
+     *
+     * This is the primary execution method that generates a result (containing
+     * potentially multiple candidates) based on the specified capability or
+     * the configured output modality.
+     *
+     * @since 0.1.0
+     *
+     * @param CapabilityEnum|null $capability Optional capability to use for generation.
+     *                                        If null, capability is inferred from output modality.
+     * @return GenerativeAiResult The generated result containing candidates.
+     * @throws InvalidArgumentException If the prompt or model validation fails.
+     * @throws RuntimeException If the model doesn't support the required capability.
+     */
+    public function generateResult(?CapabilityEnum $capability = null): GenerativeAiResult
+    {
+        $this->validateMessages();
+        // If capability is not provided, infer it
+        if ($capability === null) {
+            // First try to infer from a specific model if one is set
+            if ($this->model !== null) {
+                $inferredCapability = $this->inferCapabilityFromModelInterfaces($this->model);
+                if ($inferredCapability !== null) {
+                    $capability = $inferredCapability;
+                }
+            }
+            // If still no capability, infer from output modalities
+            if ($capability === null) {
+                $capability = $this->inferCapabilityFromOutputModalities();
+            }
+        }
+        $model = $this->getConfiguredModel($capability);
+        // Dispatch BeforeGenerateResultEvent
+        $this->dispatchEvent(new BeforeGenerateResultEvent($this->messages, $model, $capability));
+        // Route to the appropriate generation method based on capability
+        $result = $this->executeModelGeneration($model, $capability, $this->messages);
+        // Dispatch AfterGenerateResultEvent
+        $this->dispatchEvent(new AfterGenerateResultEvent($this->messages, $model, $capability, $result));
+        return $result;
+    }
+    /**
+     * Executes the model generation based on capability.
+     *
+     * @since 0.4.0
+     *
+     * @param ModelInterface $model The model to use for generation.
+     * @param CapabilityEnum $capability The capability to use.
+     * @param list<Message> $messages The messages to send.
+     * @return GenerativeAiResult The generated result.
+     * @throws RuntimeException If the model doesn't support the required capability.
+     */
+    private function executeModelGeneration(ModelInterface $model, CapabilityEnum $capability, array $messages): GenerativeAiResult
+    {
+        if ($capability->isTextGeneration()) {
+            if (!$model instanceof TextGenerationModelInterface) {
+                throw new RuntimeException(sprintf('Model "%s" does not support text generation.', $model->metadata()->getId()));
+            }
+            return $model->generateTextResult($messages);
+        }
+        if ($capability->isImageGeneration()) {
+            if (!$model instanceof ImageGenerationModelInterface) {
+                throw new RuntimeException(sprintf('Model "%s" does not support image generation.', $model->metadata()->getId()));
+            }
+            return $model->generateImageResult($messages);
+        }
+        if ($capability->isTextToSpeechConversion()) {
+            if (!$model instanceof TextToSpeechConversionModelInterface) {
+                throw new RuntimeException(sprintf('Model "%s" does not support text-to-speech conversion.', $model->metadata()->getId()));
+            }
+            return $model->convertTextToSpeechResult($messages);
+        }
+        if ($capability->isSpeechGeneration()) {
+            if (!$model instanceof SpeechGenerationModelInterface) {
+                throw new RuntimeException(sprintf('Model "%s" does not support speech generation.', $model->metadata()->getId()));
+            }
+            return $model->generateSpeechResult($messages);
+        }
+        // Video generation is not yet implemented
+        if ($capability->isVideoGeneration()) {
+            throw new RuntimeException('Output modality "video" is not yet supported.');
+        }
+        // TODO: Add support for other capabilities when interfaces are available
+        throw new RuntimeException(sprintf('Capability "%s" is not yet supported for generation.', $capability->value));
+    }
+    /**
+     * Generates a text result from the prompt.
+     *
+     * @since 0.1.0
+     *
+     * @return GenerativeAiResult The generated result containing text candidates.
+     * @throws InvalidArgumentException If the prompt or model validation fails.
+     * @throws RuntimeException If the model doesn't support text generation.
+     */
+    public function generateTextResult(): GenerativeAiResult
+    {
+        // Include text in output modalities
+        $this->includeOutputModalities(ModalityEnum::text());
+        // Generate and return the result with text generation capability
+        return $this->generateResult(CapabilityEnum::textGeneration());
+    }
+    /**
+     * Generates an image result from the prompt.
+     *
+     * @since 0.1.0
+     *
+     * @return GenerativeAiResult The generated result containing image candidates.
+     * @throws InvalidArgumentException If the prompt or model validation fails.
+     * @throws RuntimeException If the model doesn't support image generation.
+     */
+    public function generateImageResult(): GenerativeAiResult
+    {
+        // Include image in output modalities
+        $this->includeOutputModalities(ModalityEnum::image());
+        // Generate and return the result with image generation capability
+        return $this->generateResult(CapabilityEnum::imageGeneration());
+    }
+    /**
+     * Generates a speech result from the prompt.
+     *
+     * @since 0.1.0
+     *
+     * @return GenerativeAiResult The generated result containing speech audio candidates.
+     * @throws InvalidArgumentException If the prompt or model validation fails.
+     * @throws RuntimeException If the model doesn't support speech generation.
+     */
+    public function generateSpeechResult(): GenerativeAiResult
+    {
+        // Include audio in output modalities
+        $this->includeOutputModalities(ModalityEnum::audio());
+        // Generate and return the result with speech generation capability
+        return $this->generateResult(CapabilityEnum::speechGeneration());
+    }
+    /**
+     * Converts text to speech and returns the result.
+     *
+     * @since 0.1.0
+     *
+     * @return GenerativeAiResult The generated result containing speech audio candidates.
+     * @throws InvalidArgumentException If the prompt or model validation fails.
+     * @throws RuntimeException If the model doesn't support text-to-speech conversion.
+     */
+    public function convertTextToSpeechResult(): GenerativeAiResult
+    {
+        // Include audio in output modalities
+        $this->includeOutputModalities(ModalityEnum::audio());
+        // Generate and return the result with text-to-speech conversion capability
+        return $this->generateResult(CapabilityEnum::textToSpeechConversion());
+    }
+    /**
+     * Generates text from the prompt.
+     *
+     * @since 0.1.0
+     *
+     * @return string The generated text.
+     * @throws InvalidArgumentException If the prompt or model validation fails.
+     */
+    public function generateText(): string
+    {
+        return $this->generateTextResult()->toText();
+    }
+    /**
+     * Generates multiple text candidates from the prompt.
+     *
+     * @since 0.1.0
+     *
+     * @param int|null $candidateCount The number of candidates to generate.
+     * @return list<string> The generated texts.
+     * @throws InvalidArgumentException If the prompt or model validation fails.
+     */
+    public function generateTexts(?int $candidateCount = null): array
+    {
+        if ($candidateCount !== null) {
+            $this->usingCandidateCount($candidateCount);
+        }
+        // Generate text result
+        return $this->generateTextResult()->toTexts();
+    }
+    /**
+     * Generates an image from the prompt.
+     *
+     * @since 0.1.0
+     *
+     * @return File The generated image file.
+     * @throws InvalidArgumentException If the prompt or model validation fails.
+     * @throws RuntimeException If no image is generated.
+     */
+    public function generateImage(): File
+    {
+        return $this->generateImageResult()->toFile();
+    }
+    /**
+     * Generates multiple images from the prompt.
+     *
+     * @since 0.1.0
+     *
+     * @param int|null $candidateCount The number of images to generate.
+     * @return list<File> The generated image files.
+     * @throws InvalidArgumentException If the prompt or model validation fails.
+     * @throws RuntimeException If no images are generated.
+     */
+    public function generateImages(?int $candidateCount = null): array
+    {
+        if ($candidateCount !== null) {
+            $this->usingCandidateCount($candidateCount);
+        }
+        return $this->generateImageResult()->toFiles();
+    }
+    /**
+     * Converts text to speech.
+     *
+     * @since 0.1.0
+     *
+     * @return File The generated speech audio file.
+     * @throws InvalidArgumentException If the prompt or model validation fails.
+     * @throws RuntimeException If no audio is generated.
+     */
+    public function convertTextToSpeech(): File
+    {
+        return $this->convertTextToSpeechResult()->toFile();
+    }
+    /**
+     * Converts text to multiple speech outputs.
+     *
+     * @since 0.1.0
+     *
+     * @param int|null $candidateCount The number of speech outputs to generate.
+     * @return list<File> The generated speech audio files.
+     * @throws InvalidArgumentException If the prompt or model validation fails.
+     * @throws RuntimeException If no audio is generated.
+     */
+    public function convertTextToSpeeches(?int $candidateCount = null): array
+    {
+        if ($candidateCount !== null) {
+            $this->usingCandidateCount($candidateCount);
+        }
+        return $this->convertTextToSpeechResult()->toFiles();
+    }
+    /**
+     * Generates speech from the prompt.
+     *
+     * @since 0.1.0
+     *
+     * @return File The generated speech audio file.
+     * @throws InvalidArgumentException If the prompt or model validation fails.
+     * @throws RuntimeException If no audio is generated.
+     */
+    public function generateSpeech(): File
+    {
+        return $this->generateSpeechResult()->toFile();
+    }
+    /**
+     * Generates multiple speech outputs from the prompt.
+     *
+     * @since 0.1.0
+     *
+     * @param int|null $candidateCount The number of speech outputs to generate.
+     * @return list<File> The generated speech audio files.
+     * @throws InvalidArgumentException If the prompt or model validation fails.
+     * @throws RuntimeException If no audio is generated.
+     */
+    public function generateSpeeches(?int $candidateCount = null): array
+    {
+        if ($candidateCount !== null) {
+            $this->usingCandidateCount($candidateCount);
+        }
+        return $this->generateSpeechResult()->toFiles();
+    }
+    /**
+     * Appends a MessagePart to the messages array.
+     *
+     * If the last message has a user role, the part is added to it.
+     * Otherwise, a new UserMessage is created with the part.
+     *
+     * @since 0.1.0
+     *
+     * @param MessagePart $part The part to append.
+     * @return void
+     */
+    protected function appendPartToMessages(MessagePart $part): void
+    {
+        $lastMessage = end($this->messages);
+        if ($lastMessage instanceof Message && $lastMessage->getRole()->isUser()) {
+            // Replace the last message with a new one containing the appended part
+            array_pop($this->messages);
+            $this->messages[] = $lastMessage->withPart($part);
+            return;
+        }
+        // Create new UserMessage with the part
+        $this->messages[] = new UserMessage([$part]);
+    }
+    /**
+     * Gets the model to use for generation.
+     *
+     * If a model has been explicitly set, validates it meets requirements and returns it.
+     * Otherwise, finds a suitable model based on the prompt requirements.
+     *
+     * @since 0.1.0
+     *
+     * @param CapabilityEnum $capability The capability the model will be using.
+     * @return ModelInterface The model to use.
+     * @throws InvalidArgumentException If no suitable model is found or set model doesn't meet requirements.
+     */
+    private function getConfiguredModel(CapabilityEnum $capability): ModelInterface
+    {
+        $requirements = ModelRequirements::fromPromptData($capability, $this->messages, $this->modelConfig);
+        if ($this->model !== null) {
+            // Explicit model was provided via usingModel(); just update config and bind dependencies.
+            $model = $this->model;
+            $model->setConfig($this->modelConfig);
+            $this->registry->bindModelDependencies($model);
+            $this->bindModelRequestOptions($model);
+            return $model;
+        }
+        // Retrieve the candidate models map which satisfies the requirements.
+        $candidateMap = $this->getCandidateModelsMap($requirements);
+        if (empty($candidateMap)) {
+            $message = sprintf('No models found that support %s for this prompt.', $capability->value);
+            if ($this->providerIdOrClassName !== null) {
+                $message = sprintf('No models found for provider "%s" that support %s for this prompt.', $this->providerIdOrClassName, $capability->value);
+            }
+            throw new InvalidArgumentException($message);
+        }
+        // Check if any preferred models match the candidates, in priority order.
+        if (!empty($this->modelPreferenceKeys)) {
+            // Find preferences that match available candidates, preserving preference order.
+            $matchingPreferences = array_intersect_key(array_flip($this->modelPreferenceKeys), $candidateMap);
+            if (!empty($matchingPreferences)) {
+                // Get the first matching preference key
+                $firstMatchKey = key($matchingPreferences);
+                [$providerId, $modelId] = $candidateMap[$firstMatchKey];
+                $model = $this->registry->getProviderModel($providerId, $modelId, $this->modelConfig);
+                $this->bindModelRequestOptions($model);
+                return $model;
+            }
+        }
+        // No preference matched; fall back to the first candidate discovered.
+        [$providerId, $modelId] = reset($candidateMap);
+        $model = $this->registry->getProviderModel($providerId, $modelId, $this->modelConfig);
+        $this->bindModelRequestOptions($model);
+        return $model;
+    }
+    /**
+     * Binds configured request options to the model if present and supported.
+     *
+     * Request options are only applicable to API-based models that make HTTP requests.
+     *
+     * @since 0.3.0
+     *
+     * @param ModelInterface $model The model to bind request options to.
+     * @return void
+     */
+    private function bindModelRequestOptions(ModelInterface $model): void
+    {
+        if ($this->requestOptions !== null && $model instanceof ApiBasedModelInterface) {
+            $model->setRequestOptions($this->requestOptions);
+        }
+    }
+    /**
+     * Builds a map of candidate models that satisfy the requirements for efficient lookup.
+     *
+     * @since 0.2.0
+     *
+     * @param ModelRequirements $requirements The requirements derived from the prompt.
+     * @return array<string, array{0:string,1:string}> Map of preference keys to [providerId, modelId] tuples.
+     */
+    private function getCandidateModelsMap(ModelRequirements $requirements): array
+    {
+        if ($this->providerIdOrClassName === null) {
+            // No provider locked in, gather all models across providers that meet requirements.
+            $providerModelsMetadata = $this->registry->findModelsMetadataForSupport($requirements);
+            $candidateMap = [];
+            foreach ($providerModelsMetadata as $providerModels) {
+                $providerId = $providerModels->getProvider()->getId();
+                $providerMap = $this->generateMapFromCandidates($providerId, $providerModels->getModels());
+                // Use + operator to merge, preserving keys from $candidateMap (first provider wins for model-only keys)
+                $candidateMap = $candidateMap + $providerMap;
+            }
+            return $candidateMap;
+        }
+        // Provider set, only consider models from that provider.
+        $modelsMetadata = $this->registry->findProviderModelsMetadataForSupport($this->providerIdOrClassName, $requirements);
+        // Ensure we pass the provider ID, not the class name
+        $providerId = $this->registry->getProviderId($this->providerIdOrClassName);
+        return $this->generateMapFromCandidates($providerId, $modelsMetadata);
+    }
+    /**
+     * Generates a candidate map from model metadata with both provider-specific and model-only keys.
+     *
+     * @since 0.2.0
+     *
+     * @param string $providerId The provider ID.
+     * @param list<ModelMetadata> $modelsMetadata The models metadata to map.
+     * @return array<string, array{0:string,1:string}> Map of preference keys to [providerId, modelId] tuples.
+     */
+    private function generateMapFromCandidates(string $providerId, array $modelsMetadata): array
+    {
+        $map = [];
+        foreach ($modelsMetadata as $modelMetadata) {
+            $modelId = $modelMetadata->getId();
+            // Add provider-specific key
+            $providerModelKey = $this->createProviderModelPreferenceKey($providerId, $modelId);
+            $map[$providerModelKey] = [$providerId, $modelId];
+            // Add model-only key
+            $modelKey = $this->createModelPreferenceKey($modelId);
+            $map[$modelKey] = [$providerId, $modelId];
+        }
+        return $map;
+    }
+    /**
+     * Normalizes and validates a preference identifier string.
+     *
+     * @since 0.2.0
+     *
+     * @param mixed $value The value to normalize.
+     * @param string $emptyMessage The message for empty or invalid values.
+     * @return string The normalized identifier.
+     *
+     * @throws InvalidArgumentException If the value is not a non-empty string.
+     */
+    private function normalizePreferenceIdentifier($value, string $emptyMessage = 'Model preference identifiers cannot be empty.'): string
+    {
+        if (!is_string($value)) {
+            throw new InvalidArgumentException($emptyMessage);
+        }
+        $trimmed = trim($value);
+        if ($trimmed === '') {
+            throw new InvalidArgumentException($emptyMessage);
+        }
+        return $trimmed;
+    }
+    /**
+     * Creates a preference key for a provider/model combination.
+     *
+     * @since 0.2.0
+     *
+     * @param string $providerId The provider identifier.
+     * @param string $modelId The model identifier.
+     * @return string The generated preference key.
+     */
+    private function createProviderModelPreferenceKey(string $providerId, string $modelId): string
+    {
+        return 'providerModel::' . $providerId . '::' . $modelId;
+    }
+    /**
+     * Creates a preference key for a model identifier.
+     *
+     * @since 0.2.0
+     *
+     * @param string $modelId The model identifier.
+     * @return string The generated preference key.
+     */
+    private function createModelPreferenceKey(string $modelId): string
+    {
+        return 'model::' . $modelId;
+    }
+    /**
+     * Parses various input types into a Message with the given role.
+     *
+     * @since 0.1.0
+     *
+     * @param mixed $input The input to parse.
+     * @param MessageRoleEnum $defaultRole The role for the message if not specified by input.
+     * @return Message The parsed message.
+     * @throws InvalidArgumentException If the input type is not supported or results in empty message.
+     */
+    private function parseMessage($input, MessageRoleEnum $defaultRole): Message
+    {
+        // Handle Message input directly
+        if ($input instanceof Message) {
+            return $input;
+        }
+        // Handle single MessagePart
+        if ($input instanceof MessagePart) {
+            return new Message($defaultRole, [$input]);
+        }
+        // Handle string input
+        if (is_string($input)) {
+            if (trim($input) === '') {
+                throw new InvalidArgumentException('Cannot create a message from an empty string.');
+            }
+            return new Message($defaultRole, [new MessagePart($input)]);
+        }
+        // Handle array input
+        if (!is_array($input)) {
+            throw new InvalidArgumentException('Input must be a string, MessagePart, MessagePartArrayShape, ' . 'a list of string|MessagePart|MessagePartArrayShape, or a Message instance.');
+        }
+        // Handle MessageArrayShape input
+        if (Message::isArrayShape($input)) {
+            return Message::fromArray($input);
+        }
+        // Check if it's a MessagePartArrayShape
+        if (MessagePart::isArrayShape($input)) {
+            return new Message($defaultRole, [MessagePart::fromArray($input)]);
+        }
+        // It should be a list of string|MessagePart|MessagePartArrayShape
+        if (!array_is_list($input)) {
+            throw new InvalidArgumentException('Array input must be a list array.');
+        }
+        // Empty array check
+        if (empty($input)) {
+            throw new InvalidArgumentException('Cannot create a message from an empty array.');
+        }
+        $parts = [];
+        foreach ($input as $item) {
+            if (is_string($item)) {
+                $parts[] = new MessagePart($item);
+            } elseif ($item instanceof MessagePart) {
+                $parts[] = $item;
+            } elseif (is_array($item) && MessagePart::isArrayShape($item)) {
+                $parts[] = MessagePart::fromArray($item);
+            } else {
+                throw new InvalidArgumentException('Array items must be strings, MessagePart instances, or MessagePartArrayShape.');
+            }
+        }
+        return new Message($defaultRole, $parts);
+    }
+    /**
+     * Validates the messages array for prompt generation.
+     *
+     * Ensures that:
+     * - The first message is a user message
+     * - The last message is a user message
+     * - The last message has parts
+     *
+     * @since 0.1.0
+     *
+     * @return void
+     * @throws InvalidArgumentException If validation fails.
+     */
+    private function validateMessages(): void
+    {
+        if (empty($this->messages)) {
+            throw new InvalidArgumentException('Cannot generate from an empty prompt. Add content using withText() or similar methods.');
+        }
+        $firstMessage = reset($this->messages);
+        if (!$firstMessage->getRole()->isUser()) {
+            throw new InvalidArgumentException('The first message must be from a user role, not from ' . $firstMessage->getRole()->value);
+        }
+        $lastMessage = end($this->messages);
+        if (!$lastMessage->getRole()->isUser()) {
+            throw new InvalidArgumentException('The last message must be from a user role, not from ' . $lastMessage->getRole()->value);
+        }
+        if (empty($lastMessage->getParts())) {
+            throw new InvalidArgumentException('The last message must have content parts. Add content using withText() or similar methods.');
+        }
+    }
+    /**
+     * Checks if the value is a list of Message objects.
+     *
+     * @since 0.1.0
+     *
+     * @param mixed $value The value to check.
+     * @return bool True if the value is a list of Message objects.
+     *
+     * @phpstan-assert-if-true list<Message> $value
+     */
+    private function isMessagesList($value): bool
+    {
+        if (!is_array($value) || empty($value) || !array_is_list($value)) {
+            return \false;
+        }
+        // Check if all items are Messages
+        foreach ($value as $item) {
+            if (!$item instanceof Message) {
+                return \false;
+            }
+        }
+        return \true;
+    }
+    /**
+     * Includes output modalities if not already present.
+     *
+     * Adds the given modalities to the output modalities list if they're not
+     * already included. If output modalities is null, initializes it with
+     * the given modalities.
+     *
+     * @since 0.1.0
+     *
+     * @param ModalityEnum ...$modalities The modalities to include.
+     * @return void
+     */
+    private function includeOutputModalities(ModalityEnum ...$modalities): void
+    {
+        $existing = $this->modelConfig->getOutputModalities();
+        // Initialize if null
+        if ($existing === null) {
+            $this->modelConfig->setOutputModalities($modalities);
+            return;
+        }
+        // Build a set of existing modality values for O(1) lookup
+        $existingValues = [];
+        foreach ($existing as $existingModality) {
+            $existingValues[$existingModality->value] = \true;
+        }
+        // Add new modalities that don't exist
+        $toAdd = [];
+        foreach ($modalities as $modality) {
+            if (!isset($existingValues[$modality->value])) {
+                $toAdd[] = $modality;
+            }
+        }
+        // Update if we have new modalities to add
+        if (!empty($toAdd)) {
+            $this->modelConfig->setOutputModalities(array_merge($existing, $toAdd));
+        }
+    }
+    /**
+     * Dispatches an event if an event dispatcher is registered.
+     *
+     * @since 0.4.0
+     *
+     * @param object $event The event to dispatch.
+     * @return void
+     */
+    private function dispatchEvent(object $event): void
+    {
+        if ($this->eventDispatcher !== null) {
+            $this->eventDispatcher->dispatch($event);
+        }
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Common/AbstractDataTransferObject.php b/src/wp-includes/php-ai-client/src/Common/AbstractDataTransferObject.php
new file mode 100644
index 0000000000000..cf396c9219415
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Common/AbstractDataTransferObject.php
@@ -0,0 +1,126 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Common;
+
+use JsonSerializable;
+use stdClass;
+use WordPress\AiClient\Common\Contracts\WithArrayTransformationInterface;
+use WordPress\AiClient\Common\Contracts\WithJsonSchemaInterface;
+use WordPress\AiClient\Common\Exception\InvalidArgumentException;
+/**
+ * Abstract base class for all Data Value Objects in the AI Client.
+ *
+ * This abstract class consolidates the common functionality needed by all
+ * data transfer objects:
+ * - Array transformation for data manipulation
+ * - JSON schema support for validation and documentation
+ * - JSON serialization with proper empty object handling
+ *
+ * All DTOs in the AI Client should extend this class to ensure
+ * consistent behavior across the codebase.
+ *
+ * @since 0.1.0
+ *
+ * @template TArrayShape of array<string, mixed>
+ * @implements WithArrayTransformationInterface<TArrayShape>
+ */
+abstract class AbstractDataTransferObject implements WithArrayTransformationInterface, WithJsonSchemaInterface, JsonSerializable
+{
+    /**
+     * Validates that required keys exist in the array data.
+     *
+     * @since 0.1.0
+     *
+     * @param array<mixed> $data The array data to validate.
+     * @param string[] $requiredKeys The keys that must be present.
+     * @throws InvalidArgumentException If any required key is missing.
+     */
+    protected static function validateFromArrayData(array $data, array $requiredKeys): void
+    {
+        $missingKeys = [];
+        foreach ($requiredKeys as $key) {
+            if (!array_key_exists($key, $data)) {
+                $missingKeys[] = $key;
+            }
+        }
+        if (!empty($missingKeys)) {
+            throw new InvalidArgumentException(sprintf('%s::fromArray() missing required keys: %s', static::class, implode(', ', $missingKeys)));
+        }
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function isArrayShape(array $array): bool
+    {
+        try {
+            /** @var TArrayShape $array */
+            static::fromArray($array);
+            return \true;
+        } catch (InvalidArgumentException $e) {
+            return \false;
+        }
+    }
+    /**
+     * Converts the object to a JSON-serializable format.
+     *
+     * This method uses the toArray() method and then processes the result
+     * based on the JSON schema to ensure proper object representation for
+     * empty arrays.
+     *
+     * @since 0.1.0
+     *
+     * @return mixed The JSON-serializable representation.
+     */
+    #[\ReturnTypeWillChange]
+    public function jsonSerialize()
+    {
+        $data = $this->toArray();
+        $schema = static::getJsonSchema();
+        return $this->convertEmptyArraysToObjects($data, $schema);
+    }
+    /**
+     * Recursively converts empty arrays to stdClass objects where the schema expects objects.
+     *
+     * @since 0.1.0
+     *
+     * @param mixed $data The data to process.
+     * @param array<mixed, mixed> $schema The JSON schema for the data.
+     * @return mixed The processed data.
+     */
+    private function convertEmptyArraysToObjects($data, array $schema)
+    {
+        // If data is an empty array and schema expects object, convert to stdClass
+        if (is_array($data) && empty($data) && isset($schema['type']) && $schema['type'] === 'object') {
+            return new stdClass();
+        }
+        // If data is an array with content, recursively process nested structures
+        if (is_array($data)) {
+            // Handle object properties
+            if (isset($schema['properties']) && is_array($schema['properties'])) {
+                foreach ($data as $key => $value) {
+                    if (isset($schema['properties'][$key]) && is_array($schema['properties'][$key])) {
+                        $data[$key] = $this->convertEmptyArraysToObjects($value, $schema['properties'][$key]);
+                    }
+                }
+            }
+            // Handle array items
+            if (isset($schema['items']) && is_array($schema['items'])) {
+                foreach ($data as $index => $item) {
+                    $data[$index] = $this->convertEmptyArraysToObjects($item, $schema['items']);
+                }
+            }
+            // Handle oneOf schemas - just use the first one
+            if (isset($schema['oneOf']) && is_array($schema['oneOf'])) {
+                foreach ($schema['oneOf'] as $possibleSchema) {
+                    if (is_array($possibleSchema)) {
+                        return $this->convertEmptyArraysToObjects($data, $possibleSchema);
+                    }
+                }
+            }
+        }
+        return $data;
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Common/AbstractEnum.php b/src/wp-includes/php-ai-client/src/Common/AbstractEnum.php
new file mode 100644
index 0000000000000..7589c70771901
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Common/AbstractEnum.php
@@ -0,0 +1,349 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Common;
+
+use BadMethodCallException;
+use JsonSerializable;
+use ReflectionClass;
+use WordPress\AiClient\Common\Exception\InvalidArgumentException;
+use WordPress\AiClient\Common\Exception\RuntimeException;
+/**
+ * Abstract base class for enum-like behavior in PHP 7.4.
+ *
+ * This class provides enum-like functionality for PHP versions that don't support native enums.
+ * Child classes should define uppercase snake_case constants for enum values.
+ *
+ * @example
+ * class PersonEnum extends AbstractEnum {
+ *     public const FIRST_NAME = 'first';
+ *     public const LAST_NAME = 'last';
+ * }
+ *
+ * // Usage:
+ * $enum = PersonEnum::from('first'); // Creates instance with value 'first'
+ * $enum = PersonEnum::tryFrom('invalid'); // Returns null
+ * $enum = PersonEnum::firstName(); // Creates instance with value 'first'
+ * $enum->name; // 'FIRST_NAME'
+ * $enum->value; // 'first'
+ * $enum->equals('first'); // Returns true
+ * $enum->is(PersonEnum::firstName()); // Returns true
+ * PersonEnum::cases(); // Returns array of all enum instances
+ *
+ * @property-read string $value The value of the enum instance.
+ * @property-read string $name The name of the enum constant.
+ *
+ * @since 0.1.0
+ */
+abstract class AbstractEnum implements JsonSerializable
+{
+    /**
+     * @var string The value of the enum instance.
+     */
+    private string $value;
+    /**
+     * @var string The name of the enum constant.
+     */
+    private string $name;
+    /**
+     * @var array<string, array<string, string>> Cache for reflection data.
+     */
+    private static array $cache = [];
+    /**
+     * @var array<string, array<string, self>> Cache for enum instances.
+     */
+    private static array $instances = [];
+    /**
+     * Constructor is private to ensure instances are created through static methods.
+     *
+     * @since 0.1.0
+     *
+     * @param string $value The enum value.
+     * @param string $name The constant name.
+     */
+    final private function __construct(string $value, string $name)
+    {
+        $this->value = $value;
+        $this->name = $name;
+    }
+    /**
+     * Provides read-only access to properties.
+     *
+     * @since 0.1.0
+     *
+     * @param string $property The property name.
+     * @return mixed The property value.
+     * @throws BadMethodCallException If property doesn't exist.
+     */
+    final public function __get(string $property)
+    {
+        if ($property === 'value' || $property === 'name') {
+            return $this->{$property};
+        }
+        throw new BadMethodCallException(sprintf('Property %s::%s does not exist', static::class, $property));
+    }
+    /**
+     * Prevents property modification.
+     *
+     * @since 0.1.0
+     *
+     * @param string $property The property name.
+     * @param mixed $value The value to set.
+     * @throws BadMethodCallException Always, as enum properties are read-only.
+     */
+    final public function __set(string $property, $value): void
+    {
+        throw new BadMethodCallException(sprintf('Cannot modify property %s::%s - enum properties are read-only', static::class, $property));
+    }
+    /**
+     * Creates an enum instance from a value, throws exception if invalid.
+     *
+     * @since 0.1.0
+     *
+     * @param string $value The enum value.
+     * @return static The enum instance.
+     * @throws InvalidArgumentException If the value is not valid.
+     */
+    final public static function from(string $value): self
+    {
+        $instance = self::tryFrom($value);
+        if ($instance === null) {
+            throw new InvalidArgumentException(sprintf('%s is not a valid backing value for enum %s', $value, static::class));
+        }
+        return $instance;
+    }
+    /**
+     * Tries to create an enum instance from a value, returns null if invalid.
+     *
+     * @since 0.1.0
+     *
+     * @param string $value The enum value.
+     * @return static|null The enum instance or null.
+     */
+    final public static function tryFrom(string $value): ?self
+    {
+        $constants = static::getConstants();
+        foreach ($constants as $name => $constantValue) {
+            if ($constantValue === $value) {
+                return self::getInstance($constantValue, $name);
+            }
+        }
+        return null;
+    }
+    /**
+     * Gets all enum cases.
+     *
+     * @since 0.1.0
+     *
+     * @return static[] Array of all enum instances.
+     */
+    final public static function cases(): array
+    {
+        $cases = [];
+        $constants = static::getConstants();
+        foreach ($constants as $name => $value) {
+            $cases[] = self::getInstance($value, $name);
+        }
+        return $cases;
+    }
+    /**
+     * Checks if this enum has the same value as the given value.
+     *
+     * @since 0.1.0
+     *
+     * @param string|self $other The value or enum to compare.
+     * @return bool True if values are equal.
+     */
+    final public function equals($other): bool
+    {
+        if ($other instanceof self) {
+            return $this->is($other);
+        }
+        return $this->value === $other;
+    }
+    /**
+     * Checks if this enum is the same instance type and value as another enum.
+     *
+     * @since 0.1.0
+     *
+     * @param self $other The other enum to compare.
+     * @return bool True if enums are identical.
+     */
+    final public function is(self $other): bool
+    {
+        return $this === $other;
+        // Since we're using singletons, we can use identity comparison
+    }
+    /**
+     * Gets all valid values for this enum.
+     *
+     * @since 0.1.0
+     *
+     * @return string[] List of all enum values.
+     */
+    final public static function getValues(): array
+    {
+        return array_values(static::getConstants());
+    }
+    /**
+     * Checks if a value is valid for this enum.
+     *
+     * @since 0.1.0
+     *
+     * @param string $value The value to check.
+     * @return bool True if value is valid.
+     */
+    final public static function isValidValue(string $value): bool
+    {
+        return in_array($value, self::getValues(), \true);
+    }
+    /**
+     * Gets or creates a singleton instance for the given value and name.
+     *
+     * @since 0.1.0
+     *
+     * @param string $value The enum value.
+     * @param string $name The constant name.
+     * @return static The enum instance.
+     */
+    private static function getInstance(string $value, string $name): self
+    {
+        $className = static::class;
+        if (!isset(self::$instances[$className])) {
+            self::$instances[$className] = [];
+        }
+        if (!isset(self::$instances[$className][$name])) {
+            $instance = new $className($value, $name);
+            self::$instances[$className][$name] = $instance;
+        }
+        /** @var static */
+        return self::$instances[$className][$name];
+    }
+    /**
+     * Gets all constants for this enum class.
+     *
+     * @since 0.1.0
+     *
+     * @return array<string, string> Map of constant names to values.
+     * @throws RuntimeException If invalid constant found.
+     */
+    final protected static function getConstants(): array
+    {
+        $className = static::class;
+        if (!isset(self::$cache[$className])) {
+            self::$cache[$className] = static::determineClassEnumerations($className);
+        }
+        return self::$cache[$className];
+    }
+    /**
+     * Determines the class enumerations by reflecting on class constants.
+     *
+     * This method can be overridden by subclasses to customize how
+     * enumerations are determined (e.g., to add dynamic constants).
+     *
+     * @since 0.1.0
+     *
+     * @param class-string $className The fully qualified class name.
+     * @return array<string, string> Map of constant names to values.
+     * @throws RuntimeException If invalid constant found.
+     */
+    protected static function determineClassEnumerations(string $className): array
+    {
+        $reflection = new ReflectionClass($className);
+        $constants = $reflection->getConstants();
+        // Validate all constants
+        $enumConstants = [];
+        foreach ($constants as $name => $value) {
+            // Check if constant name follows uppercase snake_case pattern
+            if (!preg_match('/^[A-Z][A-Z0-9_]*$/', $name)) {
+                throw new RuntimeException(sprintf('Invalid enum constant name "%s" in %s. Constants must be UPPER_SNAKE_CASE.', $name, $className));
+            }
+            // Check if value is valid type
+            if (!is_string($value)) {
+                throw new RuntimeException(sprintf('Invalid enum value type for constant %s::%s. ' . 'Only string values are allowed, %s given.', $className, $name, gettype($value)));
+            }
+            $enumConstants[$name] = $value;
+        }
+        return $enumConstants;
+    }
+    /**
+     * Handles dynamic method calls for enum checking.
+     *
+     * @since 0.1.0
+     *
+     * @param string $name The method name.
+     * @param array<mixed> $arguments The method arguments.
+     * @return bool True if the enum value matches.
+     * @throws BadMethodCallException If the method doesn't exist.
+     */
+    final public function __call(string $name, array $arguments): bool
+    {
+        // Handle is* methods
+        if (str_starts_with($name, 'is')) {
+            $constantName = self::camelCaseToConstant(substr($name, 2));
+            $constants = static::getConstants();
+            if (isset($constants[$constantName])) {
+                return $this->value === $constants[$constantName];
+            }
+        }
+        throw new BadMethodCallException(sprintf('Method %s::%s does not exist', static::class, $name));
+    }
+    /**
+     * Handles static method calls for enum creation.
+     *
+     * @since 0.1.0
+     *
+     * @param string $name The method name.
+     * @param array<mixed> $arguments The method arguments.
+     * @return static The enum instance.
+     * @throws BadMethodCallException If the method doesn't exist.
+     */
+    final public static function __callStatic(string $name, array $arguments): self
+    {
+        $constantName = self::camelCaseToConstant($name);
+        $constants = static::getConstants();
+        if (isset($constants[$constantName])) {
+            return self::getInstance($constants[$constantName], $constantName);
+        }
+        throw new BadMethodCallException(sprintf('Method %s::%s does not exist', static::class, $name));
+    }
+    /**
+     * Converts camelCase to CONSTANT_CASE.
+     *
+     * @since 0.1.0
+     *
+     * @param string $camelCase The camelCase string.
+     * @return string The CONSTANT_CASE version.
+     */
+    private static function camelCaseToConstant(string $camelCase): string
+    {
+        $snakeCase = preg_replace('/([a-z])([A-Z])/', '$1_$2', $camelCase);
+        if ($snakeCase === null) {
+            return strtoupper($camelCase);
+        }
+        return strtoupper($snakeCase);
+    }
+    /**
+     * Returns string representation of the enum.
+     *
+     * @since 0.1.0
+     *
+     * @return string The enum value.
+     */
+    final public function __toString(): string
+    {
+        return $this->value;
+    }
+    /**
+     * Converts the enum to a JSON-serializable format.
+     *
+     * @since 0.1.0
+     *
+     * @return string The enum value.
+     */
+    #[\ReturnTypeWillChange]
+    public function jsonSerialize()
+    {
+        return $this->value;
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Common/Contracts/AiClientExceptionInterface.php b/src/wp-includes/php-ai-client/src/Common/Contracts/AiClientExceptionInterface.php
new file mode 100644
index 0000000000000..23d6256b20fa1
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Common/Contracts/AiClientExceptionInterface.php
@@ -0,0 +1,17 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Common\Contracts;
+
+use Throwable;
+/**
+ * Base interface for all AI Client exceptions.
+ *
+ * This interface allows callers to catch all AI Client specific exceptions
+ * with a single catch statement.
+ *
+ * @since 0.2.0
+ */
+interface AiClientExceptionInterface extends Throwable
+{
+}
diff --git a/src/wp-includes/php-ai-client/src/Common/Contracts/CachesDataInterface.php b/src/wp-includes/php-ai-client/src/Common/Contracts/CachesDataInterface.php
new file mode 100644
index 0000000000000..a53e2b0785d6d
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Common/Contracts/CachesDataInterface.php
@@ -0,0 +1,21 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Common\Contracts;
+
+/**
+ * Interface for objects that cache data.
+ *
+ * @since 0.4.0
+ */
+interface CachesDataInterface
+{
+    /**
+     * Invalidates all caches managed by this object.
+     *
+     * @since 0.4.0
+     *
+     * @return void
+     */
+    public function invalidateCaches(): void;
+}
diff --git a/src/wp-includes/php-ai-client/src/Common/Contracts/WithArrayTransformationInterface.php b/src/wp-includes/php-ai-client/src/Common/Contracts/WithArrayTransformationInterface.php
new file mode 100644
index 0000000000000..d94782a59b567
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Common/Contracts/WithArrayTransformationInterface.php
@@ -0,0 +1,42 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Common\Contracts;
+
+/**
+ * Interface for objects that support array transformation.
+ *
+ * @since 0.1.0
+ *
+ * @template TArrayShape of array<string, mixed>
+ */
+interface WithArrayTransformationInterface
+{
+    /**
+     * Converts the object to an array representation.
+     *
+     * @since 0.1.0
+     *
+     * @return TArrayShape The array representation.
+     */
+    public function toArray(): array;
+    /**
+     * Creates an instance from array data.
+     *
+     * @since 0.1.0
+     *
+     * @param TArrayShape $array The array data.
+     * @return self<TArrayShape> The created instance.
+     */
+    public static function fromArray(array $array): self;
+    /**
+     * Checks if the array is a valid shape for this object.
+     *
+     * @since 0.1.0
+     *
+     * @param array<mixed> $array The array to check.
+     * @return bool True if the array is a valid shape.
+     * @phpstan-assert-if-true TArrayShape $array
+     */
+    public static function isArrayShape(array $array): bool;
+}
diff --git a/src/wp-includes/php-ai-client/src/Common/Contracts/WithJsonSchemaInterface.php b/src/wp-includes/php-ai-client/src/Common/Contracts/WithJsonSchemaInterface.php
new file mode 100644
index 0000000000000..a90375349476a
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Common/Contracts/WithJsonSchemaInterface.php
@@ -0,0 +1,24 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Common\Contracts;
+
+/**
+ * Interface for objects that can provide their JSON schema representation.
+ *
+ * This interface is implemented by DTOs to provide a consistent way to retrieve
+ * their JSON schema for validation and serialization purposes.
+ *
+ * @since 0.1.0
+ */
+interface WithJsonSchemaInterface
+{
+    /**
+     * Gets the JSON schema representation of the object.
+     *
+     * @since 0.1.0
+     *
+     * @return array<string, mixed> The JSON schema as an associative array.
+     */
+    public static function getJsonSchema(): array;
+}
diff --git a/src/wp-includes/php-ai-client/src/Common/Exception/InvalidArgumentException.php b/src/wp-includes/php-ai-client/src/Common/Exception/InvalidArgumentException.php
new file mode 100644
index 0000000000000..7055cc926ae69
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Common/Exception/InvalidArgumentException.php
@@ -0,0 +1,17 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Common\Exception;
+
+use WordPress\AiClient\Common\Contracts\AiClientExceptionInterface;
+/**
+ * Exception thrown when an invalid argument is provided.
+ *
+ * This extends PHP's built-in InvalidArgumentException while implementing
+ * the AI Client exception interface for consistent catch handling.
+ *
+ * @since 0.2.0
+ */
+class InvalidArgumentException extends \InvalidArgumentException implements AiClientExceptionInterface
+{
+}
diff --git a/src/wp-includes/php-ai-client/src/Common/Exception/RuntimeException.php b/src/wp-includes/php-ai-client/src/Common/Exception/RuntimeException.php
new file mode 100644
index 0000000000000..e4bbec6bd5c96
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Common/Exception/RuntimeException.php
@@ -0,0 +1,17 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Common\Exception;
+
+use WordPress\AiClient\Common\Contracts\AiClientExceptionInterface;
+/**
+ * Exception thrown for runtime errors.
+ *
+ * This extends PHP's built-in RuntimeException while implementing
+ * the AI Client exception interface for consistent catch handling.
+ *
+ * @since 0.2.0
+ */
+class RuntimeException extends \RuntimeException implements AiClientExceptionInterface
+{
+}
diff --git a/src/wp-includes/php-ai-client/src/Common/Traits/WithDataCachingTrait.php b/src/wp-includes/php-ai-client/src/Common/Traits/WithDataCachingTrait.php
new file mode 100644
index 0000000000000..5c9cf44a31983
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Common/Traits/WithDataCachingTrait.php
@@ -0,0 +1,162 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Common\Traits;
+
+use WordPress\AiClient\AiClient;
+/**
+ * Trait for objects that cache data using PSR-16 cache with in-memory fallback.
+ *
+ * When a PSR-16 cache is configured via AiClient::setCache(), data is stored persistently.
+ * Otherwise, data is cached in-memory for the duration of the request.
+ *
+ * @since 0.4.0
+ */
+trait WithDataCachingTrait
+{
+    /**
+     * In-memory cache used when no PSR-16 cache is configured.
+     *
+     * @since 0.4.0
+     *
+     * @var array<string, mixed>
+     */
+    private array $localCache = [];
+    /**
+     * Gets the cache key suffixes managed by this object.
+     *
+     * @since 0.4.0
+     *
+     * @return list<string> The cache key suffixes.
+     */
+    abstract protected function getCachedKeys(): array;
+    /**
+     * Gets the base cache key for this object.
+     *
+     * The base cache key is used as a prefix for all cache keys managed by this object.
+     * It should be unique to the implementing class to avoid cache key collisions.
+     *
+     * @since 0.4.0
+     *
+     * @return string The base cache key.
+     */
+    abstract protected function getBaseCacheKey(): string;
+    /**
+     * Checks if a value exists in the cache.
+     *
+     * @since 0.4.0
+     *
+     * @param string $key The cache key suffix (will be appended to the base key).
+     * @return bool True if the value exists in cache, false otherwise.
+     */
+    protected function hasCache(string $key): bool
+    {
+        $fullKey = $this->buildCacheKey($key);
+        $cache = AiClient::getCache();
+        if ($cache !== null) {
+            return $cache->has($fullKey);
+        }
+        return array_key_exists($fullKey, $this->localCache);
+    }
+    /**
+     * Gets a value from the cache, or computes and caches it if not present.
+     *
+     * @since 0.4.0
+     *
+     * @param string                 $key      The cache key suffix (will be appended to the base key).
+     * @param callable               $callback The callback to compute the value if not cached.
+     * @param int|\DateInterval|null $ttl      The TTL for the cache entry, or null for default.
+     *                                         Ignored for local cache.
+     * @return mixed The cached or computed value.
+     */
+    protected function cached(string $key, callable $callback, $ttl = null)
+    {
+        if ($this->hasCache($key)) {
+            return $this->getCache($key);
+        }
+        $value = $callback();
+        $this->setCache($key, $value, $ttl);
+        return $value;
+    }
+    /**
+     * Gets a value from the cache.
+     *
+     * @since 0.4.0
+     *
+     * @param string $key     The cache key suffix (will be appended to the base key).
+     * @param mixed  $default The default value to return if the key does not exist.
+     * @return mixed The cached value or the default value if not found.
+     */
+    protected function getCache(string $key, $default = null)
+    {
+        $fullKey = $this->buildCacheKey($key);
+        $cache = AiClient::getCache();
+        if ($cache !== null) {
+            return $cache->get($fullKey, $default);
+        }
+        return $this->localCache[$fullKey] ?? $default;
+    }
+    /**
+     * Sets a value in the cache.
+     *
+     * @since 0.4.0
+     *
+     * @param string                $key   The cache key suffix (will be appended to the base key).
+     * @param mixed                 $value The value to cache.
+     * @param int|\DateInterval|null $ttl   The TTL for the cache entry, or null for default. Ignored for local cache.
+     * @return bool True on success, false on failure.
+     */
+    protected function setCache(string $key, $value, $ttl = null): bool
+    {
+        $fullKey = $this->buildCacheKey($key);
+        $cache = AiClient::getCache();
+        if ($cache !== null) {
+            return $cache->set($fullKey, $value, $ttl);
+        }
+        $this->localCache[$fullKey] = $value;
+        return \true;
+    }
+    /**
+     * Invalidates all caches managed by this object.
+     *
+     * @since 0.4.0
+     *
+     * @return void
+     */
+    public function invalidateCaches(): void
+    {
+        foreach ($this->getCachedKeys() as $key) {
+            $this->clearCache($key);
+        }
+    }
+    /**
+     * Clears a value from the cache.
+     *
+     * @since 0.4.0
+     *
+     * @param string $key The cache key suffix (will be appended to the base key).
+     * @return bool True on success, false on failure.
+     */
+    protected function clearCache(string $key): bool
+    {
+        $fullKey = $this->buildCacheKey($key);
+        $cache = AiClient::getCache();
+        if ($cache !== null) {
+            return $cache->delete($fullKey);
+        }
+        unset($this->localCache[$fullKey]);
+        return \true;
+    }
+    /**
+     * Builds the full cache key by combining the base key with the suffix.
+     *
+     * @since 0.4.0
+     *
+     * @param string $key The cache key suffix.
+     * @return string The full cache key.
+     */
+    private function buildCacheKey(string $key): string
+    {
+        return $this->getBaseCacheKey() . '_' . $key;
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Events/AfterGenerateResultEvent.php b/src/wp-includes/php-ai-client/src/Events/AfterGenerateResultEvent.php
new file mode 100644
index 0000000000000..d20c6fc07ba1b
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Events/AfterGenerateResultEvent.php
@@ -0,0 +1,115 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Events;
+
+use WordPress\AiClient\Messages\DTO\Message;
+use WordPress\AiClient\Providers\Models\Contracts\ModelInterface;
+use WordPress\AiClient\Providers\Models\Enums\CapabilityEnum;
+use WordPress\AiClient\Results\DTO\GenerativeAiResult;
+/**
+ * Event dispatched after a prompt has been sent to the AI model and a response received.
+ *
+ * This event allows listeners to inspect the result of the model call for logging,
+ * analytics, or other post-processing purposes. The result object is immutable.
+ *
+ * @since 0.4.0
+ */
+class AfterGenerateResultEvent
+{
+    /**
+     * @var list<Message> The messages that were sent to the model.
+     */
+    private array $messages;
+    /**
+     * @var ModelInterface The model that processed the prompt.
+     */
+    private ModelInterface $model;
+    /**
+     * @var CapabilityEnum|null The capability that was used for generation.
+     */
+    private ?CapabilityEnum $capability;
+    /**
+     * @var GenerativeAiResult The result from the model.
+     */
+    private GenerativeAiResult $result;
+    /**
+     * Constructor.
+     *
+     * @since 0.4.0
+     *
+     * @param list<Message> $messages The messages that were sent to the model.
+     * @param ModelInterface $model The model that processed the prompt.
+     * @param CapabilityEnum|null $capability The capability that was used for generation.
+     * @param GenerativeAiResult $result The result from the model.
+     */
+    public function __construct(array $messages, ModelInterface $model, ?CapabilityEnum $capability, GenerativeAiResult $result)
+    {
+        $this->messages = $messages;
+        $this->model = $model;
+        $this->capability = $capability;
+        $this->result = $result;
+    }
+    /**
+     * Gets the messages that were sent to the model.
+     *
+     * @since 0.4.0
+     *
+     * @return list<Message> The messages.
+     */
+    public function getMessages(): array
+    {
+        return $this->messages;
+    }
+    /**
+     * Gets the model that processed the prompt.
+     *
+     * @since 0.4.0
+     *
+     * @return ModelInterface The model.
+     */
+    public function getModel(): ModelInterface
+    {
+        return $this->model;
+    }
+    /**
+     * Gets the capability that was used for generation.
+     *
+     * @since 0.4.0
+     *
+     * @return CapabilityEnum|null The capability, or null if not specified.
+     */
+    public function getCapability(): ?CapabilityEnum
+    {
+        return $this->capability;
+    }
+    /**
+     * Gets the result from the model.
+     *
+     * @since 0.4.0
+     *
+     * @return GenerativeAiResult The result.
+     */
+    public function getResult(): GenerativeAiResult
+    {
+        return $this->result;
+    }
+    /**
+     * Performs a deep clone of the event.
+     *
+     * This method ensures that message and result objects are cloned to prevent
+     * modifications to the cloned event from affecting the original.
+     * The model object is not cloned as it is a service object.
+     *
+     * @since 0.4.1
+     */
+    public function __clone()
+    {
+        $clonedMessages = [];
+        foreach ($this->messages as $message) {
+            $clonedMessages[] = clone $message;
+        }
+        $this->messages = $clonedMessages;
+        $this->result = clone $this->result;
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Events/BeforeGenerateResultEvent.php b/src/wp-includes/php-ai-client/src/Events/BeforeGenerateResultEvent.php
new file mode 100644
index 0000000000000..553d9d8cad849
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Events/BeforeGenerateResultEvent.php
@@ -0,0 +1,97 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Events;
+
+use WordPress\AiClient\Messages\DTO\Message;
+use WordPress\AiClient\Providers\Models\Contracts\ModelInterface;
+use WordPress\AiClient\Providers\Models\Enums\CapabilityEnum;
+/**
+ * Event dispatched before a prompt is sent to the AI model.
+ *
+ * This event allows listeners to inspect and modify the messages before they
+ * are sent to the model. The event is not stoppable, meaning the model call
+ * will always proceed regardless of listener actions.
+ *
+ * @since 0.4.0
+ */
+class BeforeGenerateResultEvent
+{
+    /**
+     * @var list<Message> The messages to be sent to the model.
+     */
+    private array $messages;
+    /**
+     * @var ModelInterface The model that will process the prompt.
+     */
+    private ModelInterface $model;
+    /**
+     * @var CapabilityEnum|null The capability being used for generation.
+     */
+    private ?CapabilityEnum $capability;
+    /**
+     * Constructor.
+     *
+     * @since 0.4.0
+     *
+     * @param list<Message> $messages The messages to be sent to the model.
+     * @param ModelInterface $model The model that will process the prompt.
+     * @param CapabilityEnum|null $capability The capability being used for generation.
+     */
+    public function __construct(array $messages, ModelInterface $model, ?CapabilityEnum $capability)
+    {
+        $this->messages = $messages;
+        $this->model = $model;
+        $this->capability = $capability;
+    }
+    /**
+     * Gets the messages to be sent to the model.
+     *
+     * @since 0.4.0
+     *
+     * @return list<Message> The messages.
+     */
+    public function getMessages(): array
+    {
+        return $this->messages;
+    }
+    /**
+     * Gets the model that will process the prompt.
+     *
+     * @since 0.4.0
+     *
+     * @return ModelInterface The model.
+     */
+    public function getModel(): ModelInterface
+    {
+        return $this->model;
+    }
+    /**
+     * Gets the capability being used for generation.
+     *
+     * @since 0.4.0
+     *
+     * @return CapabilityEnum|null The capability, or null if not specified.
+     */
+    public function getCapability(): ?CapabilityEnum
+    {
+        return $this->capability;
+    }
+    /**
+     * Performs a deep clone of the event.
+     *
+     * This method ensures that message objects are cloned to prevent
+     * modifications to the cloned event from affecting the original.
+     * The model object is not cloned as it is a service object.
+     *
+     * @since 0.4.1
+     */
+    public function __clone()
+    {
+        $clonedMessages = [];
+        foreach ($this->messages as $message) {
+            $clonedMessages[] = clone $message;
+        }
+        $this->messages = $clonedMessages;
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Files/DTO/File.php b/src/wp-includes/php-ai-client/src/Files/DTO/File.php
new file mode 100644
index 0000000000000..c032041dae4ba
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Files/DTO/File.php
@@ -0,0 +1,400 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Files\DTO;
+
+use WordPress\AiClient\Common\AbstractDataTransferObject;
+use WordPress\AiClient\Common\Exception\InvalidArgumentException;
+use WordPress\AiClient\Common\Exception\RuntimeException;
+use WordPress\AiClient\Files\Enums\FileTypeEnum;
+use WordPress\AiClient\Files\ValueObjects\MimeType;
+/**
+ * Represents a file in the AI client.
+ *
+ * This DTO automatically detects whether a file is a URL, base64 data, or local file path
+ * and handles them appropriately.
+ *
+ * @since 0.1.0
+ *
+ * @phpstan-type FileArrayShape array{
+ *     fileType: string,
+ *     url?: string,
+ *     mimeType: string,
+ *     base64Data?: string
+ * }
+ *
+ * @extends AbstractDataTransferObject<FileArrayShape>
+ */
+class File extends AbstractDataTransferObject
+{
+    public const KEY_FILE_TYPE = 'fileType';
+    public const KEY_MIME_TYPE = 'mimeType';
+    public const KEY_URL = 'url';
+    public const KEY_BASE64_DATA = 'base64Data';
+    /**
+     * @var MimeType The MIME type of the file.
+     */
+    private MimeType $mimeType;
+    /**
+     * @var FileTypeEnum The type of file storage.
+     */
+    private FileTypeEnum $fileType;
+    /**
+     * @var string|null The URL for remote files.
+     */
+    private ?string $url = null;
+    /**
+     * @var string|null The base64 data for inline files.
+     */
+    private ?string $base64Data = null;
+    /**
+     * Constructor.
+     *
+     * @since 0.1.0
+     *
+     * @param string $file The file string (URL, base64 data, or local path).
+     * @param string|null $mimeType The MIME type of the file (optional).
+     * @throws InvalidArgumentException If the file format is invalid or MIME type cannot be determined.
+     */
+    public function __construct(string $file, ?string $mimeType = null)
+    {
+        // Detect and process the file type (will set MIME type if possible)
+        $this->detectAndProcessFile($file, $mimeType);
+    }
+    /**
+     * Detects the file type and processes it accordingly.
+     *
+     * @since 0.1.0
+     *
+     * @param string $file The file string to process.
+     * @param string|null $providedMimeType The explicitly provided MIME type.
+     * @throws InvalidArgumentException If the file format is invalid or MIME type cannot be determined.
+     */
+    private function detectAndProcessFile(string $file, ?string $providedMimeType): void
+    {
+        // Check if it's a URL
+        if ($this->isUrl($file)) {
+            $this->fileType = FileTypeEnum::remote();
+            $this->url = $file;
+            $this->mimeType = $this->determineMimeType($providedMimeType, null, $file);
+            return;
+        }
+        // Data URI pattern.
+        $dataUriPattern = '/^data:(?:([a-zA-Z0-9][a-zA-Z0-9!#$&\-\^_+.]*\/[a-zA-Z0-9][a-zA-Z0-9!#$&\-\^_+.]*' . '(?:;[a-zA-Z0-9\-]+=[a-zA-Z0-9\-]+)*)?;)?base64,([A-Za-z0-9+\/]*={0,2})$/';
+        // Check if it's a data URI.
+        if (preg_match($dataUriPattern, $file, $matches)) {
+            $this->fileType = FileTypeEnum::inline();
+            $this->base64Data = $matches[2];
+            // Extract just the base64 data
+            $extractedMimeType = empty($matches[1]) ? null : $matches[1];
+            $this->mimeType = $this->determineMimeType($providedMimeType, $extractedMimeType, null);
+            return;
+        }
+        // Check if it's a local file path (before base64 check)
+        if (file_exists($file) && is_file($file)) {
+            $this->fileType = FileTypeEnum::inline();
+            $this->base64Data = $this->convertFileToBase64($file);
+            $this->mimeType = $this->determineMimeType($providedMimeType, null, $file);
+            return;
+        }
+        // Check if it's plain base64
+        if (preg_match('/^[A-Za-z0-9+\/]*={0,2}$/', $file)) {
+            if ($providedMimeType === null) {
+                throw new InvalidArgumentException('MIME type is required when providing plain base64 data without data URI format.');
+            }
+            $this->fileType = FileTypeEnum::inline();
+            $this->base64Data = $file;
+            $this->mimeType = new MimeType($providedMimeType);
+            return;
+        }
+        throw new InvalidArgumentException('Invalid file provided. Expected URL, base64 data, or valid local file path.');
+    }
+    /**
+     * Checks if a string is a valid URL.
+     *
+     * @since 0.1.0
+     *
+     * @param string $string The string to check.
+     * @return bool True if the string is a URL.
+     */
+    private function isUrl(string $string): bool
+    {
+        return filter_var($string, \FILTER_VALIDATE_URL) !== \false && preg_match('/^https?:\/\//i', $string);
+    }
+    /**
+     * Converts a local file to base64.
+     *
+     * @since 0.1.0
+     *
+     * @param string $filePath The path to the local file.
+     * @return string The base64-encoded file data.
+     * @throws RuntimeException If the file cannot be read.
+     */
+    private function convertFileToBase64(string $filePath): string
+    {
+        $fileContent = @file_get_contents($filePath);
+        if ($fileContent === \false) {
+            throw new RuntimeException(sprintf('Unable to read file: %s', $filePath));
+        }
+        return base64_encode($fileContent);
+    }
+    /**
+     * Gets the file type.
+     *
+     * @since 0.1.0
+     *
+     * @return FileTypeEnum The file type.
+     */
+    public function getFileType(): FileTypeEnum
+    {
+        return $this->fileType;
+    }
+    /**
+     * Checks if the file is an inline file.
+     *
+     * @since 0.1.0
+     *
+     * @return bool True if the file is inline (base64/data URI).
+     */
+    public function isInline(): bool
+    {
+        return $this->fileType->isInline();
+    }
+    /**
+     * Checks if the file is a remote file.
+     *
+     * @since 0.1.0
+     *
+     * @return bool True if the file is remote (URL).
+     */
+    public function isRemote(): bool
+    {
+        return $this->fileType->isRemote();
+    }
+    /**
+     * Gets the URL for remote files.
+     *
+     * @since 0.1.0
+     *
+     * @return string|null The URL, or null if not a remote file.
+     */
+    public function getUrl(): ?string
+    {
+        return $this->url;
+    }
+    /**
+     * Gets the base64-encoded data for inline files.
+     *
+     * @since 0.1.0
+     *
+     * @return string|null The plain base64-encoded data (without data URI prefix), or null if not an inline file.
+     */
+    public function getBase64Data(): ?string
+    {
+        return $this->base64Data;
+    }
+    /**
+     * Gets the data as a data URI for inline files.
+     *
+     * @since 0.1.0
+     *
+     * @return string|null The data URI in format: data:[mimeType];base64,[data], or null if not an inline file.
+     */
+    public function getDataUri(): ?string
+    {
+        if ($this->base64Data === null) {
+            return null;
+        }
+        return sprintf('data:%s;base64,%s', $this->getMimeType(), $this->base64Data);
+    }
+    /**
+     * Gets the MIME type of the file as a string.
+     *
+     * @since 0.1.0
+     *
+     * @return string The MIME type string value.
+     */
+    public function getMimeType(): string
+    {
+        return (string) $this->mimeType;
+    }
+    /**
+     * Gets the MIME type object.
+     *
+     * @since 0.1.0
+     *
+     * @return MimeType The MIME type object.
+     */
+    public function getMimeTypeObject(): MimeType
+    {
+        return $this->mimeType;
+    }
+    /**
+     * Checks if the file is a video.
+     *
+     * @since 0.1.0
+     *
+     * @return bool True if the file is a video.
+     */
+    public function isVideo(): bool
+    {
+        return $this->mimeType->isVideo();
+    }
+    /**
+     * Checks if the file is an image.
+     *
+     * @since 0.1.0
+     *
+     * @return bool True if the file is an image.
+     */
+    public function isImage(): bool
+    {
+        return $this->mimeType->isImage();
+    }
+    /**
+     * Checks if the file is audio.
+     *
+     * @since 0.1.0
+     *
+     * @return bool True if the file is audio.
+     */
+    public function isAudio(): bool
+    {
+        return $this->mimeType->isAudio();
+    }
+    /**
+     * Checks if the file is text.
+     *
+     * @since 0.1.0
+     *
+     * @return bool True if the file is text.
+     */
+    public function isText(): bool
+    {
+        return $this->mimeType->isText();
+    }
+    /**
+     * Checks if the file is a document.
+     *
+     * @since 0.1.0
+     *
+     * @return bool True if the file is a document.
+     */
+    public function isDocument(): bool
+    {
+        return $this->mimeType->isDocument();
+    }
+    /**
+     * Checks if the file is a specific MIME type.
+     *
+     * @since 0.1.0
+     *
+     * @param string $type The mime type to check (e.g. 'image', 'text', 'video', 'audio').
+     *
+     * @return bool True if the file is of the specified type.
+     */
+    public function isMimeType(string $type): bool
+    {
+        return $this->mimeType->isType($type);
+    }
+    /**
+     * Determines the MIME type from various sources.
+     *
+     * @since 0.1.0
+     *
+     * @param string|null $providedMimeType The explicitly provided MIME type.
+     * @param string|null $extractedMimeType The MIME type extracted from data URI.
+     * @param string|null $pathOrUrl The file path or URL to extract extension from.
+     * @return MimeType The determined MIME type.
+     * @throws InvalidArgumentException If MIME type cannot be determined.
+     */
+    private function determineMimeType(?string $providedMimeType, ?string $extractedMimeType, ?string $pathOrUrl): MimeType
+    {
+        // Prefer explicitly provided MIME type
+        if ($providedMimeType !== null) {
+            return new MimeType($providedMimeType);
+        }
+        // Use extracted MIME type from data URI
+        if ($extractedMimeType !== null) {
+            return new MimeType($extractedMimeType);
+        }
+        // Try to determine from file extension
+        if ($pathOrUrl !== null) {
+            $parsedUrl = parse_url($pathOrUrl);
+            $path = $parsedUrl['path'] ?? $pathOrUrl;
+            // Remove query string and fragment if present
+            $cleanPath = strtok($path, '?#');
+            if ($cleanPath === \false) {
+                $cleanPath = $path;
+            }
+            $extension = pathinfo($cleanPath, \PATHINFO_EXTENSION);
+            if (!empty($extension)) {
+                try {
+                    return MimeType::fromExtension($extension);
+                } catch (InvalidArgumentException $e) {
+                    // Extension not recognized, continue to error
+                    unset($e);
+                }
+            }
+        }
+        throw new InvalidArgumentException('Unable to determine MIME type. Please provide it explicitly.');
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function getJsonSchema(): array
+    {
+        return ['type' => 'object', 'oneOf' => [['properties' => [self::KEY_FILE_TYPE => ['type' => 'string', 'const' => FileTypeEnum::REMOTE, 'description' => 'The file type.'], self::KEY_MIME_TYPE => ['type' => 'string', 'description' => 'The MIME type of the file.', 'pattern' => '^[a-zA-Z0-9][a-zA-Z0-9!#$&\-\^_+.]*\/[a-zA-Z0-9]' . '[a-zA-Z0-9!#$&\-\^_+.]*$'], self::KEY_URL => ['type' => 'string', 'format' => 'uri', 'description' => 'The URL to the remote file.']], 'required' => [self::KEY_FILE_TYPE, self::KEY_MIME_TYPE, self::KEY_URL]], ['properties' => [self::KEY_FILE_TYPE => ['type' => 'string', 'const' => FileTypeEnum::INLINE, 'description' => 'The file type.'], self::KEY_MIME_TYPE => ['type' => 'string', 'description' => 'The MIME type of the file.', 'pattern' => '^[a-zA-Z0-9][a-zA-Z0-9!#$&\-\^_+.]*\/[a-zA-Z0-9]' . '[a-zA-Z0-9!#$&\-\^_+.]*$'], self::KEY_BASE64_DATA => ['type' => 'string', 'description' => 'The base64-encoded file data.']], 'required' => [self::KEY_FILE_TYPE, self::KEY_MIME_TYPE, self::KEY_BASE64_DATA]]]];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     *
+     * @return FileArrayShape
+     */
+    public function toArray(): array
+    {
+        $data = [self::KEY_FILE_TYPE => $this->fileType->value, self::KEY_MIME_TYPE => $this->getMimeType()];
+        if ($this->url !== null) {
+            $data[self::KEY_URL] = $this->url;
+        } elseif (!$this->fileType->isRemote() && $this->base64Data !== null) {
+            $data[self::KEY_BASE64_DATA] = $this->base64Data;
+        } else {
+            throw new RuntimeException('File requires either url or base64Data. This should not be a possible condition.');
+        }
+        return $data;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function fromArray(array $array): self
+    {
+        static::validateFromArrayData($array, [self::KEY_FILE_TYPE]);
+        // Check which properties are set to determine how to construct the File
+        $mimeType = $array[self::KEY_MIME_TYPE] ?? null;
+        if (isset($array[self::KEY_URL])) {
+            return new self($array[self::KEY_URL], $mimeType);
+        } elseif (isset($array[self::KEY_BASE64_DATA])) {
+            return new self($array[self::KEY_BASE64_DATA], $mimeType);
+        } else {
+            throw new InvalidArgumentException('File requires either url or base64Data.');
+        }
+    }
+    /**
+     * Performs a deep clone of the file.
+     *
+     * This method ensures that the MimeType value object is cloned to prevent
+     * any shared references between the original and cloned file.
+     *
+     * @since 0.4.1
+     */
+    public function __clone()
+    {
+        $this->mimeType = clone $this->mimeType;
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Files/Enums/FileTypeEnum.php b/src/wp-includes/php-ai-client/src/Files/Enums/FileTypeEnum.php
new file mode 100644
index 0000000000000..0f50ff93fa39f
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Files/Enums/FileTypeEnum.php
@@ -0,0 +1,31 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Files\Enums;
+
+use WordPress\AiClient\Common\AbstractEnum;
+/**
+ * Represents the type of file storage.
+ *
+ * @method static self inline() Returns the inline file type.
+ * @method static self remote() Returns the remote file type.
+ * @method bool isInline() Checks if this is an inline file type.
+ * @method bool isRemote() Checks if this is a remote file type.
+ *
+ * @since 0.1.0
+ */
+class FileTypeEnum extends AbstractEnum
+{
+    /**
+     * Inline file with base64-encoded data.
+     *
+     * @var string
+     */
+    public const INLINE = 'inline';
+    /**
+     * Remote file referenced by URL.
+     *
+     * @var string
+     */
+    public const REMOTE = 'remote';
+}
diff --git a/src/wp-includes/php-ai-client/src/Files/Enums/MediaOrientationEnum.php b/src/wp-includes/php-ai-client/src/Files/Enums/MediaOrientationEnum.php
new file mode 100644
index 0000000000000..21ea89364d24d
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Files/Enums/MediaOrientationEnum.php
@@ -0,0 +1,39 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Files\Enums;
+
+use WordPress\AiClient\Common\AbstractEnum;
+/**
+ * Represents the type of file storage.
+ *
+ * @method static self square() Returns the square orientation
+ * @method static self landscape() Returns the landscape orientation.
+ * @method static self portrait() Returns the portrait orientation.
+ * @method bool isSquare() Checks if this is an square orientation
+ * @method bool isLandscape() Checks if this is a landscape orientation.
+ * @method bool isPortrait() Checks if this is a portrait orientation.
+ *
+ * @since 0.1.0
+ */
+class MediaOrientationEnum extends AbstractEnum
+{
+    /**
+     * Square orientation.
+     *
+     * @var string
+     */
+    public const SQUARE = 'square';
+    /**
+     * Landscape orientation.
+     *
+     * @var string
+     */
+    public const LANDSCAPE = 'landscape';
+    /**
+     * Portrait orientation.
+     *
+     * @var string
+     */
+    public const PORTRAIT = 'portrait';
+}
diff --git a/src/wp-includes/php-ai-client/src/Files/ValueObjects/MimeType.php b/src/wp-includes/php-ai-client/src/Files/ValueObjects/MimeType.php
new file mode 100644
index 0000000000000..f002a6a0d058f
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Files/ValueObjects/MimeType.php
@@ -0,0 +1,255 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Files\ValueObjects;
+
+use WordPress\AiClient\Common\Exception\InvalidArgumentException;
+/**
+ * Value object representing a MIME type.
+ *
+ * This immutable value object encapsulates MIME type validation and
+ * provides convenient methods for checking MIME type categories.
+ *
+ * @since 0.1.0
+ */
+final class MimeType
+{
+    /**
+     * @var string The MIME type value.
+     */
+    private string $value;
+    /**
+     * Common MIME type mappings for file extensions.
+     *
+     * @var array<string, string>
+     */
+    private static array $extensionMap = [
+        // Text
+        'txt' => 'text/plain',
+        'html' => 'text/html',
+        'htm' => 'text/html',
+        'css' => 'text/css',
+        'js' => 'application/javascript',
+        'json' => 'application/json',
+        'xml' => 'application/xml',
+        'csv' => 'text/csv',
+        'md' => 'text/markdown',
+        // Images
+        'jpg' => 'image/jpeg',
+        'jpeg' => 'image/jpeg',
+        'png' => 'image/png',
+        'gif' => 'image/gif',
+        'bmp' => 'image/bmp',
+        'webp' => 'image/webp',
+        'svg' => 'image/svg+xml',
+        'ico' => 'image/x-icon',
+        // Documents
+        'pdf' => 'application/pdf',
+        'doc' => 'application/msword',
+        'docx' => 'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
+        'xls' => 'application/vnd.ms-excel',
+        'xlsx' => 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
+        'ppt' => 'application/vnd.ms-powerpoint',
+        'pptx' => 'application/vnd.openxmlformats-officedocument.presentationml.presentation',
+        'odt' => 'application/vnd.oasis.opendocument.text',
+        'ods' => 'application/vnd.oasis.opendocument.spreadsheet',
+        // Archives
+        'zip' => 'application/zip',
+        'tar' => 'application/x-tar',
+        'gz' => 'application/gzip',
+        'rar' => 'application/x-rar-compressed',
+        '7z' => 'application/x-7z-compressed',
+        // Audio
+        'mp3' => 'audio/mpeg',
+        'wav' => 'audio/wav',
+        'ogg' => 'audio/ogg',
+        'flac' => 'audio/flac',
+        'm4a' => 'audio/m4a',
+        'aac' => 'audio/aac',
+        // Video
+        'mp4' => 'video/mp4',
+        'avi' => 'video/x-msvideo',
+        'mov' => 'video/quicktime',
+        'wmv' => 'video/x-ms-wmv',
+        'flv' => 'video/x-flv',
+        'webm' => 'video/webm',
+        'mkv' => 'video/x-matroska',
+        // Fonts
+        'ttf' => 'font/ttf',
+        'otf' => 'font/otf',
+        'woff' => 'font/woff',
+        'woff2' => 'font/woff2',
+        // Other
+        'php' => 'application/x-httpd-php',
+        'sh' => 'application/x-sh',
+        'exe' => 'application/x-msdownload',
+    ];
+    /**
+     * Document MIME types.
+     *
+     * @var array<string>
+     */
+    private static array $documentTypes = ['application/pdf', 'application/msword', 'application/vnd.openxmlformats-officedocument.wordprocessingml.document', 'application/vnd.ms-excel', 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet', 'application/vnd.ms-powerpoint', 'application/vnd.openxmlformats-officedocument.presentationml.presentation', 'application/vnd.oasis.opendocument.text', 'application/vnd.oasis.opendocument.spreadsheet'];
+    /**
+     * Constructor.
+     *
+     * @since 0.1.0
+     *
+     * @param string $value The MIME type value.
+     * @throws InvalidArgumentException If the MIME type is invalid.
+     */
+    public function __construct(string $value)
+    {
+        if (!self::isValid($value)) {
+            throw new InvalidArgumentException(sprintf('Invalid MIME type: %s', $value));
+        }
+        $this->value = strtolower($value);
+    }
+    /**
+     * Gets the primary known file extension for this MIME type.
+     *
+     * @since 0.1.0
+     *
+     * @return string The file extension (without the dot).
+     * @throws InvalidArgumentException If no known extension exists for this MIME type.
+     */
+    public function toExtension(): string
+    {
+        // Reverse lookup for the MIME type to find the extension.
+        $extension = array_search($this->value, self::$extensionMap, \true);
+        if ($extension === \false) {
+            throw new InvalidArgumentException(sprintf('No known extension for MIME type: %s', $this->value));
+        }
+        return $extension;
+    }
+    /**
+     * Creates a MimeType from a file extension.
+     *
+     * @since 0.1.0
+     *
+     * @param string $extension The file extension (without the dot).
+     * @return self The MimeType instance.
+     * @throws InvalidArgumentException If the extension is not recognized.
+     */
+    public static function fromExtension(string $extension): self
+    {
+        $extension = strtolower($extension);
+        if (!isset(self::$extensionMap[$extension])) {
+            throw new InvalidArgumentException(sprintf('Unknown file extension: %s', $extension));
+        }
+        return new self(self::$extensionMap[$extension]);
+    }
+    /**
+     * Checks if a MIME type string is valid.
+     *
+     * @since 0.1.0
+     *
+     * @param string $mimeType The MIME type to validate.
+     * @return bool True if valid.
+     */
+    public static function isValid(string $mimeType): bool
+    {
+        // Basic MIME type validation: type/subtype
+        return (bool) preg_match('/^[a-zA-Z0-9][a-zA-Z0-9!#$&\-\^_+.]*\/[a-zA-Z0-9][a-zA-Z0-9!#$&\-\^_+.]*$/', $mimeType);
+    }
+    /**
+     * Checks if this MIME type is a specific type.
+     *
+     * This method returns true when the stored MIME type begins with the
+     * given prefix. For example, `"audio"` matches `"audio/mpeg"`.
+     *
+     * @since 0.1.0
+     *
+     * @param string $mimeType The MIME type prefix to check (e.g., "audio", "image").
+     * @return bool True if this MIME type is of the specified type.
+     */
+    public function isType(string $mimeType): bool
+    {
+        return str_starts_with($this->value, strtolower($mimeType) . '/');
+    }
+    /**
+     * Checks if this is an image MIME type.
+     *
+     * @since 0.1.0
+     *
+     * @return bool True if this is an image type.
+     */
+    public function isImage(): bool
+    {
+        return $this->isType('image');
+    }
+    /**
+     * Checks if this is an audio MIME type.
+     *
+     * @since 0.1.0
+     *
+     * @return bool True if this is an audio type.
+     */
+    public function isAudio(): bool
+    {
+        return $this->isType('audio');
+    }
+    /**
+     * Checks if this is a video MIME type.
+     *
+     * @since 0.1.0
+     *
+     * @return bool True if this is a video type.
+     */
+    public function isVideo(): bool
+    {
+        return $this->isType('video');
+    }
+    /**
+     * Checks if this is a text MIME type.
+     *
+     * @since 0.1.0
+     *
+     * @return bool True if this is a text type.
+     */
+    public function isText(): bool
+    {
+        return $this->isType('text');
+    }
+    /**
+     * Checks if this is a document MIME type.
+     *
+     * @since 0.1.0
+     *
+     * @return bool True if this is a document type.
+     */
+    public function isDocument(): bool
+    {
+        return in_array($this->value, self::$documentTypes, \true);
+    }
+    /**
+     * Checks if this MIME type equals another.
+     *
+     * @since 0.1.0
+     *
+     * @param self|string $other The other MIME type to compare.
+     * @return bool True if equal.
+     * @throws InvalidArgumentException If the other MIME type is invalid.
+     */
+    public function equals($other): bool
+    {
+        if ($other instanceof self) {
+            return $this->value === $other->value;
+        }
+        if (is_string($other)) {
+            return $this->value === strtolower($other);
+        }
+        throw new InvalidArgumentException(sprintf('Invalid MIME type comparison: %s', gettype($other)));
+    }
+    /**
+     * Gets the string representation of the MIME type.
+     *
+     * @since 0.1.0
+     *
+     * @return string The MIME type value.
+     */
+    public function __toString(): string
+    {
+        return $this->value;
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Messages/DTO/Message.php b/src/wp-includes/php-ai-client/src/Messages/DTO/Message.php
new file mode 100644
index 0000000000000..290685a58854e
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Messages/DTO/Message.php
@@ -0,0 +1,173 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Messages\DTO;
+
+use WordPress\AiClient\Common\AbstractDataTransferObject;
+use WordPress\AiClient\Common\Exception\InvalidArgumentException;
+use WordPress\AiClient\Messages\Enums\MessageRoleEnum;
+/**
+ * Represents a message in an AI conversation.
+ *
+ * Messages are the fundamental unit of communication with AI models,
+ * containing a role and one or more parts with different content types.
+ *
+ * @since 0.1.0
+ *
+ * @phpstan-import-type MessagePartArrayShape from MessagePart
+ *
+ * @phpstan-type MessageArrayShape array{
+ *     role: string,
+ *     parts: array<MessagePartArrayShape>
+ * }
+ *
+ * @extends AbstractDataTransferObject<MessageArrayShape>
+ */
+class Message extends AbstractDataTransferObject
+{
+    public const KEY_ROLE = 'role';
+    public const KEY_PARTS = 'parts';
+    /**
+     * @var MessageRoleEnum The role of the message sender.
+     */
+    protected MessageRoleEnum $role;
+    /**
+     * @var MessagePart[] The parts that make up this message.
+     */
+    protected array $parts;
+    /**
+     * Constructor.
+     *
+     * @since 0.1.0
+     *
+     * @param MessageRoleEnum $role The role of the message sender.
+     * @param MessagePart[] $parts The parts that make up this message.
+     * @throws InvalidArgumentException If parts contain invalid content for the role.
+     */
+    public function __construct(MessageRoleEnum $role, array $parts)
+    {
+        $this->role = $role;
+        $this->parts = $parts;
+        $this->validateParts();
+    }
+    /**
+     * Gets the role of the message sender.
+     *
+     * @since 0.1.0
+     *
+     * @return MessageRoleEnum The role.
+     */
+    public function getRole(): MessageRoleEnum
+    {
+        return $this->role;
+    }
+    /**
+     * Gets the message parts.
+     *
+     * @since 0.1.0
+     *
+     * @return MessagePart[] The message parts.
+     */
+    public function getParts(): array
+    {
+        return $this->parts;
+    }
+    /**
+     * Returns a new instance with the given part appended.
+     *
+     * @since 0.1.0
+     *
+     * @param MessagePart $part The part to append.
+     * @return Message A new instance with the part appended.
+     * @throws InvalidArgumentException If the part is invalid for the role.
+     */
+    public function withPart(\WordPress\AiClient\Messages\DTO\MessagePart $part): \WordPress\AiClient\Messages\DTO\Message
+    {
+        $newParts = $this->parts;
+        $newParts[] = $part;
+        return new \WordPress\AiClient\Messages\DTO\Message($this->role, $newParts);
+    }
+    /**
+     * Validates that the message parts are appropriate for the message role.
+     *
+     * @since 0.1.0
+     *
+     * @return void
+     * @throws InvalidArgumentException If validation fails.
+     */
+    private function validateParts(): void
+    {
+        foreach ($this->parts as $part) {
+            $type = $part->getType();
+            if ($this->role->isUser() && $type->isFunctionCall()) {
+                throw new InvalidArgumentException('User messages cannot contain function calls.');
+            }
+            if ($this->role->isModel() && $type->isFunctionResponse()) {
+                throw new InvalidArgumentException('Model messages cannot contain function responses.');
+            }
+        }
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function getJsonSchema(): array
+    {
+        return ['type' => 'object', 'properties' => [self::KEY_ROLE => ['type' => 'string', 'enum' => MessageRoleEnum::getValues(), 'description' => 'The role of the message sender.'], self::KEY_PARTS => ['type' => 'array', 'items' => \WordPress\AiClient\Messages\DTO\MessagePart::getJsonSchema(), 'minItems' => 1, 'description' => 'The parts that make up this message.']], 'required' => [self::KEY_ROLE, self::KEY_PARTS]];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     *
+     * @return MessageArrayShape
+     */
+    public function toArray(): array
+    {
+        return [self::KEY_ROLE => $this->role->value, self::KEY_PARTS => array_map(function (\WordPress\AiClient\Messages\DTO\MessagePart $part) {
+            return $part->toArray();
+        }, $this->parts)];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     *
+     * @return self The specific message class based on the role.
+     */
+    final public static function fromArray(array $array): self
+    {
+        static::validateFromArrayData($array, [self::KEY_ROLE, self::KEY_PARTS]);
+        $role = MessageRoleEnum::from($array[self::KEY_ROLE]);
+        $partsData = $array[self::KEY_PARTS];
+        $parts = array_map(function (array $partData) {
+            return \WordPress\AiClient\Messages\DTO\MessagePart::fromArray($partData);
+        }, $partsData);
+        // Determine which concrete class to instantiate based on role
+        if ($role->isUser()) {
+            return new \WordPress\AiClient\Messages\DTO\UserMessage($parts);
+        } elseif ($role->isModel()) {
+            return new \WordPress\AiClient\Messages\DTO\ModelMessage($parts);
+        } else {
+            // Only USER and MODEL roles are supported
+            throw new InvalidArgumentException('Invalid message role: ' . $role->value);
+        }
+    }
+    /**
+     * Performs a deep clone of the message.
+     *
+     * This method ensures that message part objects are cloned to prevent
+     * modifications to the cloned message from affecting the original.
+     *
+     * @since 0.4.1
+     */
+    public function __clone()
+    {
+        $clonedParts = [];
+        foreach ($this->parts as $part) {
+            $clonedParts[] = clone $part;
+        }
+        $this->parts = $clonedParts;
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Messages/DTO/MessagePart.php b/src/wp-includes/php-ai-client/src/Messages/DTO/MessagePart.php
new file mode 100644
index 0000000000000..6728fd81cf697
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Messages/DTO/MessagePart.php
@@ -0,0 +1,242 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Messages\DTO;
+
+use WordPress\AiClient\Common\AbstractDataTransferObject;
+use WordPress\AiClient\Common\Exception\InvalidArgumentException;
+use WordPress\AiClient\Common\Exception\RuntimeException;
+use WordPress\AiClient\Files\DTO\File;
+use WordPress\AiClient\Messages\Enums\MessagePartChannelEnum;
+use WordPress\AiClient\Messages\Enums\MessagePartTypeEnum;
+use WordPress\AiClient\Tools\DTO\FunctionCall;
+use WordPress\AiClient\Tools\DTO\FunctionResponse;
+/**
+ * Represents a part of a message.
+ *
+ * Messages can contain multiple parts of different types, such as text, files,
+ * function calls, etc. This DTO encapsulates one such part.
+ *
+ * @since 0.1.0
+ *
+ * @phpstan-import-type FileArrayShape from File
+ * @phpstan-import-type FunctionCallArrayShape from FunctionCall
+ * @phpstan-import-type FunctionResponseArrayShape from FunctionResponse
+ *
+ * @phpstan-type MessagePartArrayShape array{
+ *     channel: string,
+ *     type: string,
+ *     text?: string,
+ *     file?: FileArrayShape,
+ *     functionCall?: FunctionCallArrayShape,
+ *     functionResponse?: FunctionResponseArrayShape
+ * }
+ *
+ * @extends AbstractDataTransferObject<MessagePartArrayShape>
+ */
+class MessagePart extends AbstractDataTransferObject
+{
+    public const KEY_CHANNEL = 'channel';
+    public const KEY_TYPE = 'type';
+    public const KEY_TEXT = 'text';
+    public const KEY_FILE = 'file';
+    public const KEY_FUNCTION_CALL = 'functionCall';
+    public const KEY_FUNCTION_RESPONSE = 'functionResponse';
+    /**
+     * @var MessagePartChannelEnum The channel this message part belongs to.
+     */
+    private MessagePartChannelEnum $channel;
+    /**
+     * @var MessagePartTypeEnum The type of this message part.
+     */
+    private MessagePartTypeEnum $type;
+    /**
+     * @var string|null Text content (when type is TEXT).
+     */
+    private ?string $text = null;
+    /**
+     * @var File|null File data (when type is FILE).
+     */
+    private ?File $file = null;
+    /**
+     * @var FunctionCall|null Function call request (when type is FUNCTION_CALL).
+     */
+    private ?FunctionCall $functionCall = null;
+    /**
+     * @var FunctionResponse|null Function response (when type is FUNCTION_RESPONSE).
+     */
+    private ?FunctionResponse $functionResponse = null;
+    /**
+     * Constructor that accepts various content types and infers the message part type.
+     *
+     * @since 0.1.0
+     *
+     * @param mixed $content The content of this message part.
+     * @param MessagePartChannelEnum|null $channel The channel this part belongs to. Defaults to CONTENT.
+     * @throws InvalidArgumentException If an unsupported content type is provided.
+     */
+    public function __construct($content, ?MessagePartChannelEnum $channel = null)
+    {
+        $this->channel = $channel ?? MessagePartChannelEnum::content();
+        if (is_string($content)) {
+            $this->type = MessagePartTypeEnum::text();
+            $this->text = $content;
+        } elseif ($content instanceof File) {
+            $this->type = MessagePartTypeEnum::file();
+            $this->file = $content;
+        } elseif ($content instanceof FunctionCall) {
+            $this->type = MessagePartTypeEnum::functionCall();
+            $this->functionCall = $content;
+        } elseif ($content instanceof FunctionResponse) {
+            $this->type = MessagePartTypeEnum::functionResponse();
+            $this->functionResponse = $content;
+        } else {
+            $type = is_object($content) ? get_class($content) : gettype($content);
+            throw new InvalidArgumentException(sprintf('Unsupported content type %s. Expected string, File, ' . 'FunctionCall, or FunctionResponse.', $type));
+        }
+    }
+    /**
+     * Gets the channel this message part belongs to.
+     *
+     * @since 0.1.0
+     *
+     * @return MessagePartChannelEnum The channel.
+     */
+    public function getChannel(): MessagePartChannelEnum
+    {
+        return $this->channel;
+    }
+    /**
+     * Gets the type of this message part.
+     *
+     * @since 0.1.0
+     *
+     * @return MessagePartTypeEnum The type.
+     */
+    public function getType(): MessagePartTypeEnum
+    {
+        return $this->type;
+    }
+    /**
+     * Gets the text content.
+     *
+     * @since 0.1.0
+     *
+     * @return string|null The text content or null if not a text part.
+     */
+    public function getText(): ?string
+    {
+        return $this->text;
+    }
+    /**
+     * Gets the file.
+     *
+     * @since 0.1.0
+     *
+     * @return File|null The file or null if not a file part.
+     */
+    public function getFile(): ?File
+    {
+        return $this->file;
+    }
+    /**
+     * Gets the function call.
+     *
+     * @since 0.1.0
+     *
+     * @return FunctionCall|null The function call or null if not a function call part.
+     */
+    public function getFunctionCall(): ?FunctionCall
+    {
+        return $this->functionCall;
+    }
+    /**
+     * Gets the function response.
+     *
+     * @since 0.1.0
+     *
+     * @return FunctionResponse|null The function response or null if not a function response part.
+     */
+    public function getFunctionResponse(): ?FunctionResponse
+    {
+        return $this->functionResponse;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function getJsonSchema(): array
+    {
+        $channelSchema = ['type' => 'string', 'enum' => MessagePartChannelEnum::getValues(), 'description' => 'The channel this message part belongs to.'];
+        return ['oneOf' => [['type' => 'object', 'properties' => [self::KEY_CHANNEL => $channelSchema, self::KEY_TYPE => ['type' => 'string', 'const' => MessagePartTypeEnum::text()->value], self::KEY_TEXT => ['type' => 'string', 'description' => 'Text content.']], 'required' => [self::KEY_TYPE, self::KEY_TEXT], 'additionalProperties' => \false], ['type' => 'object', 'properties' => [self::KEY_CHANNEL => $channelSchema, self::KEY_TYPE => ['type' => 'string', 'const' => MessagePartTypeEnum::file()->value], self::KEY_FILE => File::getJsonSchema()], 'required' => [self::KEY_TYPE, self::KEY_FILE], 'additionalProperties' => \false], ['type' => 'object', 'properties' => [self::KEY_CHANNEL => $channelSchema, self::KEY_TYPE => ['type' => 'string', 'const' => MessagePartTypeEnum::functionCall()->value], self::KEY_FUNCTION_CALL => FunctionCall::getJsonSchema()], 'required' => [self::KEY_TYPE, self::KEY_FUNCTION_CALL], 'additionalProperties' => \false], ['type' => 'object', 'properties' => [self::KEY_CHANNEL => $channelSchema, self::KEY_TYPE => ['type' => 'string', 'const' => MessagePartTypeEnum::functionResponse()->value], self::KEY_FUNCTION_RESPONSE => FunctionResponse::getJsonSchema()], 'required' => [self::KEY_TYPE, self::KEY_FUNCTION_RESPONSE], 'additionalProperties' => \false]]];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     *
+     * @return MessagePartArrayShape
+     */
+    public function toArray(): array
+    {
+        $data = [self::KEY_CHANNEL => $this->channel->value, self::KEY_TYPE => $this->type->value];
+        if ($this->text !== null) {
+            $data[self::KEY_TEXT] = $this->text;
+        } elseif ($this->file !== null) {
+            $data[self::KEY_FILE] = $this->file->toArray();
+        } elseif ($this->functionCall !== null) {
+            $data[self::KEY_FUNCTION_CALL] = $this->functionCall->toArray();
+        } elseif ($this->functionResponse !== null) {
+            $data[self::KEY_FUNCTION_RESPONSE] = $this->functionResponse->toArray();
+        } else {
+            throw new RuntimeException('MessagePart requires one of: text, file, functionCall, or functionResponse. ' . 'This should not be a possible condition.');
+        }
+        return $data;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function fromArray(array $array): self
+    {
+        if (isset($array[self::KEY_CHANNEL])) {
+            $channel = MessagePartChannelEnum::from($array[self::KEY_CHANNEL]);
+        } else {
+            $channel = null;
+        }
+        // Check which properties are set to determine how to construct the MessagePart
+        if (isset($array[self::KEY_TEXT])) {
+            return new self($array[self::KEY_TEXT], $channel);
+        } elseif (isset($array[self::KEY_FILE])) {
+            return new self(File::fromArray($array[self::KEY_FILE]), $channel);
+        } elseif (isset($array[self::KEY_FUNCTION_CALL])) {
+            return new self(FunctionCall::fromArray($array[self::KEY_FUNCTION_CALL]), $channel);
+        } elseif (isset($array[self::KEY_FUNCTION_RESPONSE])) {
+            return new self(FunctionResponse::fromArray($array[self::KEY_FUNCTION_RESPONSE]), $channel);
+        } else {
+            throw new InvalidArgumentException('MessagePart requires one of: text, file, functionCall, or functionResponse.');
+        }
+    }
+    /**
+     * Performs a deep clone of the message part.
+     *
+     * This method ensures that nested objects (file, function call, function response)
+     * are cloned to prevent modifications to the cloned part from affecting the original.
+     *
+     * @since 0.4.1
+     */
+    public function __clone()
+    {
+        if ($this->file !== null) {
+            $this->file = clone $this->file;
+        }
+        if ($this->functionCall !== null) {
+            $this->functionCall = clone $this->functionCall;
+        }
+        if ($this->functionResponse !== null) {
+            $this->functionResponse = clone $this->functionResponse;
+        }
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Messages/DTO/ModelMessage.php b/src/wp-includes/php-ai-client/src/Messages/DTO/ModelMessage.php
new file mode 100644
index 0000000000000..e998e46cd8bff
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Messages/DTO/ModelMessage.php
@@ -0,0 +1,32 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Messages\DTO;
+
+use WordPress\AiClient\Messages\Enums\MessageRoleEnum;
+/**
+ * Represents a message from the AI model.
+ *
+ * This is a convenience class that automatically sets the role to MODEL.
+ * Model messages contain the AI's responses.
+ *
+ * Important: Do not rely on `instanceof ModelMessage` to determine the message role.
+ * This is merely a helper class for construction. Always use `$message->getRole()`
+ * to check the role of a message.
+ *
+ * @since 0.1.0
+ */
+class ModelMessage extends \WordPress\AiClient\Messages\DTO\Message
+{
+    /**
+     * Constructor.
+     *
+     * @since 0.1.0
+     *
+     * @param MessagePart[] $parts The parts that make up this message.
+     */
+    public function __construct(array $parts)
+    {
+        parent::__construct(MessageRoleEnum::model(), $parts);
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Messages/DTO/UserMessage.php b/src/wp-includes/php-ai-client/src/Messages/DTO/UserMessage.php
new file mode 100644
index 0000000000000..35e5349ff43f4
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Messages/DTO/UserMessage.php
@@ -0,0 +1,31 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Messages\DTO;
+
+use WordPress\AiClient\Messages\Enums\MessageRoleEnum;
+/**
+ * Represents a message from a user.
+ *
+ * This is a convenience class that automatically sets the role to USER.
+ *
+ * Important: Do not rely on `instanceof UserMessage` to determine the message role.
+ * This is merely a helper class for construction. Always use `$message->getRole()`
+ * to check the role of a message.
+ *
+ * @since 0.1.0
+ */
+class UserMessage extends \WordPress\AiClient\Messages\DTO\Message
+{
+    /**
+     * Constructor.
+     *
+     * @since 0.1.0
+     *
+     * @param MessagePart[] $parts The parts that make up this message.
+     */
+    public function __construct(array $parts)
+    {
+        parent::__construct(MessageRoleEnum::user(), $parts);
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Messages/Enums/MessagePartChannelEnum.php b/src/wp-includes/php-ai-client/src/Messages/Enums/MessagePartChannelEnum.php
new file mode 100644
index 0000000000000..5b7cbf56559ba
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Messages/Enums/MessagePartChannelEnum.php
@@ -0,0 +1,27 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Messages\Enums;
+
+use WordPress\AiClient\Common\AbstractEnum;
+/**
+ * Enum for message part channels.
+ *
+ * @since 0.1.0
+ *
+ * @method static self content() Creates an instance for CONTENT channel.
+ * @method static self thought() Creates an instance for THOUGHT channel.
+ * @method bool isContent() Checks if the channel is CONTENT.
+ * @method bool isThought() Checks if the channel is THOUGHT.
+ */
+class MessagePartChannelEnum extends AbstractEnum
+{
+    /**
+     * Regular (primary) content.
+     */
+    public const CONTENT = 'content';
+    /**
+     * Model thinking or reasoning.
+     */
+    public const THOUGHT = 'thought';
+}
diff --git a/src/wp-includes/php-ai-client/src/Messages/Enums/MessagePartTypeEnum.php b/src/wp-includes/php-ai-client/src/Messages/Enums/MessagePartTypeEnum.php
new file mode 100644
index 0000000000000..b0365bdca6313
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Messages/Enums/MessagePartTypeEnum.php
@@ -0,0 +1,39 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Messages\Enums;
+
+use WordPress\AiClient\Common\AbstractEnum;
+/**
+ * Enum for message part types.
+ *
+ * @since 0.1.0
+ *
+ * @method static self text() Creates an instance for TEXT type.
+ * @method static self file() Creates an instance for FILE type.
+ * @method static self functionCall() Creates an instance for FUNCTION_CALL type.
+ * @method static self functionResponse() Creates an instance for FUNCTION_RESPONSE type.
+ * @method bool isText() Checks if the type is TEXT.
+ * @method bool isFile() Checks if the type is FILE.
+ * @method bool isFunctionCall() Checks if the type is FUNCTION_CALL.
+ * @method bool isFunctionResponse() Checks if the type is FUNCTION_RESPONSE.
+ */
+class MessagePartTypeEnum extends AbstractEnum
+{
+    /**
+     * Text content.
+     */
+    public const TEXT = 'text';
+    /**
+     * File content (inline or remote).
+     */
+    public const FILE = 'file';
+    /**
+     * Function call request.
+     */
+    public const FUNCTION_CALL = 'function_call';
+    /**
+     * Function response.
+     */
+    public const FUNCTION_RESPONSE = 'function_response';
+}
diff --git a/src/wp-includes/php-ai-client/src/Messages/Enums/MessageRoleEnum.php b/src/wp-includes/php-ai-client/src/Messages/Enums/MessageRoleEnum.php
new file mode 100644
index 0000000000000..79c808dc3de89
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Messages/Enums/MessageRoleEnum.php
@@ -0,0 +1,27 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Messages\Enums;
+
+use WordPress\AiClient\Common\AbstractEnum;
+/**
+ * Enum for message roles in AI conversations.
+ *
+ * @since 0.1.0
+ *
+ * @method static self user() Creates an instance for USER role.
+ * @method static self model() Creates an instance for MODEL role.
+ * @method bool isUser() Checks if the role is USER.
+ * @method bool isModel() Checks if the role is MODEL.
+ */
+class MessageRoleEnum extends AbstractEnum
+{
+    /**
+     * User role - messages from the user.
+     */
+    public const USER = 'user';
+    /**
+     * Model role - messages from the AI model.
+     */
+    public const MODEL = 'model';
+}
diff --git a/src/wp-includes/php-ai-client/src/Messages/Enums/ModalityEnum.php b/src/wp-includes/php-ai-client/src/Messages/Enums/ModalityEnum.php
new file mode 100644
index 0000000000000..c2ffbdeae66f5
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Messages/Enums/ModalityEnum.php
@@ -0,0 +1,45 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Messages\Enums;
+
+use WordPress\AiClient\Common\AbstractEnum;
+/**
+ * Enum for input/output modalities.
+ *
+ * @since 0.1.0
+ *
+ * @method static self text() Creates an instance for TEXT modality.
+ * @method static self document() Creates an instance for DOCUMENT modality.
+ * @method static self image() Creates an instance for IMAGE modality.
+ * @method static self audio() Creates an instance for AUDIO modality.
+ * @method static self video() Creates an instance for VIDEO modality.
+ * @method bool isText() Checks if the modality is TEXT.
+ * @method bool isDocument() Checks if the modality is DOCUMENT.
+ * @method bool isImage() Checks if the modality is IMAGE.
+ * @method bool isAudio() Checks if the modality is AUDIO.
+ * @method bool isVideo() Checks if the modality is VIDEO.
+ */
+class ModalityEnum extends AbstractEnum
+{
+    /**
+     * Text modality.
+     */
+    public const TEXT = 'text';
+    /**
+     * Document modality (PDFs, Word docs, etc.).
+     */
+    public const DOCUMENT = 'document';
+    /**
+     * Image modality.
+     */
+    public const IMAGE = 'image';
+    /**
+     * Audio modality.
+     */
+    public const AUDIO = 'audio';
+    /**
+     * Video modality.
+     */
+    public const VIDEO = 'video';
+}
diff --git a/src/wp-includes/php-ai-client/src/Operations/Contracts/OperationInterface.php b/src/wp-includes/php-ai-client/src/Operations/Contracts/OperationInterface.php
new file mode 100644
index 0000000000000..fccccd7a2ba8e
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Operations/Contracts/OperationInterface.php
@@ -0,0 +1,33 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Operations\Contracts;
+
+use WordPress\AiClient\Operations\Enums\OperationStateEnum;
+/**
+ * Interface for AI operations.
+ *
+ * Operations represent long-running AI tasks that may not complete immediately.
+ * They provide a way to track the progress and retrieve results asynchronously.
+ *
+ * @since 0.1.0
+ */
+interface OperationInterface
+{
+    /**
+     * Gets the operation ID.
+     *
+     * @since 0.1.0
+     *
+     * @return string The unique operation identifier.
+     */
+    public function getId(): string;
+    /**
+     * Gets the current state of the operation.
+     *
+     * @since 0.1.0
+     *
+     * @return OperationStateEnum The operation state.
+     */
+    public function getState(): OperationStateEnum;
+}
diff --git a/src/wp-includes/php-ai-client/src/Operations/DTO/GenerativeAiOperation.php b/src/wp-includes/php-ai-client/src/Operations/DTO/GenerativeAiOperation.php
new file mode 100644
index 0000000000000..95bdb72c81d54
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Operations/DTO/GenerativeAiOperation.php
@@ -0,0 +1,133 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Operations\DTO;
+
+use WordPress\AiClient\Common\AbstractDataTransferObject;
+use WordPress\AiClient\Operations\Contracts\OperationInterface;
+use WordPress\AiClient\Operations\Enums\OperationStateEnum;
+use WordPress\AiClient\Results\DTO\GenerativeAiResult;
+/**
+ * Represents a long-running generative AI operation.
+ *
+ * This DTO tracks the progress of generative AI tasks that may not complete
+ * immediately, providing access to the result once available.
+ *
+ * @since 0.1.0
+ *
+ * @phpstan-import-type GenerativeAiResultArrayShape from GenerativeAiResult
+ *
+ * @phpstan-type GenerativeAiOperationArrayShape array{id: string, state: string, result?: GenerativeAiResultArrayShape}
+ *
+ * @extends AbstractDataTransferObject<GenerativeAiOperationArrayShape>
+ */
+class GenerativeAiOperation extends AbstractDataTransferObject implements OperationInterface
+{
+    public const KEY_ID = 'id';
+    public const KEY_STATE = 'state';
+    public const KEY_RESULT = 'result';
+    /**
+     * @var string Unique identifier for this operation.
+     */
+    private string $id;
+    /**
+     * @var OperationStateEnum The current state of the operation.
+     */
+    private OperationStateEnum $state;
+    /**
+     * @var GenerativeAiResult|null The result once the operation completes.
+     */
+    private ?GenerativeAiResult $result;
+    /**
+     * Constructor.
+     *
+     * @since 0.1.0
+     *
+     * @param string $id Unique identifier for this operation.
+     * @param OperationStateEnum $state The current state of the operation.
+     * @param GenerativeAiResult|null $result The result once the operation completes.
+     */
+    public function __construct(string $id, OperationStateEnum $state, ?GenerativeAiResult $result = null)
+    {
+        $this->id = $id;
+        $this->state = $state;
+        $this->result = $result;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public function getId(): string
+    {
+        return $this->id;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public function getState(): OperationStateEnum
+    {
+        return $this->state;
+    }
+    /**
+     * Gets the operation result.
+     *
+     * @since 0.1.0
+     *
+     * @return GenerativeAiResult|null The result or null if not yet complete.
+     */
+    public function getResult(): ?GenerativeAiResult
+    {
+        return $this->result;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function getJsonSchema(): array
+    {
+        return ['oneOf' => [
+            // Succeeded state - has result
+            ['type' => 'object', 'properties' => [self::KEY_ID => ['type' => 'string', 'description' => 'Unique identifier for this operation.'], self::KEY_STATE => ['type' => 'string', 'const' => OperationStateEnum::succeeded()->value], self::KEY_RESULT => GenerativeAiResult::getJsonSchema()], 'required' => [self::KEY_ID, self::KEY_STATE, self::KEY_RESULT], 'additionalProperties' => \false],
+            // All other states - no result
+            ['type' => 'object', 'properties' => [self::KEY_ID => ['type' => 'string', 'description' => 'Unique identifier for this operation.'], self::KEY_STATE => ['type' => 'string', 'enum' => [OperationStateEnum::starting()->value, OperationStateEnum::processing()->value, OperationStateEnum::failed()->value, OperationStateEnum::canceled()->value], 'description' => 'The current state of the operation.']], 'required' => [self::KEY_ID, self::KEY_STATE], 'additionalProperties' => \false],
+        ]];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     *
+     * @return GenerativeAiOperationArrayShape
+     */
+    public function toArray(): array
+    {
+        $data = [self::KEY_ID => $this->id, self::KEY_STATE => $this->state->value];
+        if ($this->result !== null) {
+            $data[self::KEY_RESULT] = $this->result->toArray();
+        }
+        return $data;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function fromArray(array $array): self
+    {
+        static::validateFromArrayData($array, [self::KEY_ID, self::KEY_STATE]);
+        $state = OperationStateEnum::from($array[self::KEY_STATE]);
+        if ($state->isSucceeded()) {
+            // If the operation has succeeded, it must have a result
+            static::validateFromArrayData($array, [self::KEY_RESULT]);
+        }
+        $result = null;
+        if (isset($array[self::KEY_RESULT])) {
+            $result = GenerativeAiResult::fromArray($array[self::KEY_RESULT]);
+        }
+        return new self($array[self::KEY_ID], $state, $result);
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Operations/Enums/OperationStateEnum.php b/src/wp-includes/php-ai-client/src/Operations/Enums/OperationStateEnum.php
new file mode 100644
index 0000000000000..034cea04b3fe8
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Operations/Enums/OperationStateEnum.php
@@ -0,0 +1,45 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Operations\Enums;
+
+use WordPress\AiClient\Common\AbstractEnum;
+/**
+ * Enum for operation states.
+ *
+ * @since 0.1.0
+ *
+ * @method static self starting() Creates an instance for STARTING state.
+ * @method static self processing() Creates an instance for PROCESSING state.
+ * @method static self succeeded() Creates an instance for SUCCEEDED state.
+ * @method static self failed() Creates an instance for FAILED state.
+ * @method static self canceled() Creates an instance for CANCELED state.
+ * @method bool isStarting() Checks if the state is STARTING.
+ * @method bool isProcessing() Checks if the state is PROCESSING.
+ * @method bool isSucceeded() Checks if the state is SUCCEEDED.
+ * @method bool isFailed() Checks if the state is FAILED.
+ * @method bool isCanceled() Checks if the state is CANCELED.
+ */
+class OperationStateEnum extends AbstractEnum
+{
+    /**
+     * Operation is starting.
+     */
+    public const STARTING = 'starting';
+    /**
+     * Operation is processing.
+     */
+    public const PROCESSING = 'processing';
+    /**
+     * Operation succeeded.
+     */
+    public const SUCCEEDED = 'succeeded';
+    /**
+     * Operation failed.
+     */
+    public const FAILED = 'failed';
+    /**
+     * Operation was canceled.
+     */
+    public const CANCELED = 'canceled';
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/AbstractProvider.php b/src/wp-includes/php-ai-client/src/Providers/AbstractProvider.php
new file mode 100644
index 0000000000000..580c0d4e6ff2c
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/AbstractProvider.php
@@ -0,0 +1,120 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers;
+
+use WordPress\AiClient\Providers\Contracts\ModelMetadataDirectoryInterface;
+use WordPress\AiClient\Providers\Contracts\ProviderAvailabilityInterface;
+use WordPress\AiClient\Providers\Contracts\ProviderInterface;
+use WordPress\AiClient\Providers\DTO\ProviderMetadata;
+use WordPress\AiClient\Providers\Models\Contracts\ModelInterface;
+use WordPress\AiClient\Providers\Models\DTO\ModelConfig;
+use WordPress\AiClient\Providers\Models\DTO\ModelMetadata;
+/**
+ * Base class for a provider.
+ *
+ * @since 0.1.0
+ */
+abstract class AbstractProvider implements ProviderInterface
+{
+    /**
+     * @var array<string, ProviderMetadata> Cache for provider metadata per class.
+     */
+    private static array $metadataCache = [];
+    /**
+     * @var array<string, ProviderAvailabilityInterface> Cache for provider availability per class.
+     */
+    private static array $availabilityCache = [];
+    /**
+     * @var array<string, ModelMetadataDirectoryInterface> Cache for model metadata directory per class.
+     */
+    private static array $modelMetadataDirectoryCache = [];
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    final public static function metadata(): ProviderMetadata
+    {
+        $className = static::class;
+        if (!isset(self::$metadataCache[$className])) {
+            self::$metadataCache[$className] = static::createProviderMetadata();
+        }
+        return self::$metadataCache[$className];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    final public static function model(string $modelId, ?ModelConfig $modelConfig = null): ModelInterface
+    {
+        $providerMetadata = static::metadata();
+        $modelMetadata = static::modelMetadataDirectory()->getModelMetadata($modelId);
+        $model = static::createModel($modelMetadata, $providerMetadata);
+        if ($modelConfig) {
+            $model->setConfig($modelConfig);
+        }
+        return $model;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    final public static function availability(): ProviderAvailabilityInterface
+    {
+        $className = static::class;
+        if (!isset(self::$availabilityCache[$className])) {
+            self::$availabilityCache[$className] = static::createProviderAvailability();
+        }
+        return self::$availabilityCache[$className];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    final public static function modelMetadataDirectory(): ModelMetadataDirectoryInterface
+    {
+        $className = static::class;
+        if (!isset(self::$modelMetadataDirectoryCache[$className])) {
+            self::$modelMetadataDirectoryCache[$className] = static::createModelMetadataDirectory();
+        }
+        return self::$modelMetadataDirectoryCache[$className];
+    }
+    /**
+     * Creates a model instance based on the given model metadata and provider metadata.
+     *
+     * @since 0.1.0
+     *
+     * @param ModelMetadata $modelMetadata The model metadata.
+     * @param ProviderMetadata $providerMetadata The provider metadata.
+     * @return ModelInterface The new model instance.
+     */
+    abstract protected static function createModel(ModelMetadata $modelMetadata, ProviderMetadata $providerMetadata): ModelInterface;
+    /**
+     * Creates the provider metadata instance.
+     *
+     * @since 0.1.0
+     *
+     * @return ProviderMetadata The provider metadata.
+     */
+    abstract protected static function createProviderMetadata(): ProviderMetadata;
+    /**
+     * Creates the provider availability instance.
+     *
+     * @since 0.1.0
+     *
+     * @return ProviderAvailabilityInterface The provider availability.
+     */
+    abstract protected static function createProviderAvailability(): ProviderAvailabilityInterface;
+    /**
+     * Creates the model metadata directory instance.
+     *
+     * @since 0.1.0
+     *
+     * @return ModelMetadataDirectoryInterface The model metadata directory.
+     */
+    abstract protected static function createModelMetadataDirectory(): ModelMetadataDirectoryInterface;
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/ApiBasedImplementation/AbstractApiBasedModel.php b/src/wp-includes/php-ai-client/src/Providers/ApiBasedImplementation/AbstractApiBasedModel.php
new file mode 100644
index 0000000000000..30705e64cb37c
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/ApiBasedImplementation/AbstractApiBasedModel.php
@@ -0,0 +1,111 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\ApiBasedImplementation;
+
+use WordPress\AiClient\Providers\ApiBasedImplementation\Contracts\ApiBasedModelInterface;
+use WordPress\AiClient\Providers\DTO\ProviderMetadata;
+use WordPress\AiClient\Providers\Http\Contracts\WithHttpTransporterInterface;
+use WordPress\AiClient\Providers\Http\Contracts\WithRequestAuthenticationInterface;
+use WordPress\AiClient\Providers\Http\DTO\RequestOptions;
+use WordPress\AiClient\Providers\Http\Traits\WithHttpTransporterTrait;
+use WordPress\AiClient\Providers\Http\Traits\WithRequestAuthenticationTrait;
+use WordPress\AiClient\Providers\Models\DTO\ModelConfig;
+use WordPress\AiClient\Providers\Models\DTO\ModelMetadata;
+/**
+ * Base class for an API-based model for a provider.
+ *
+ * While this class contains no abstract methods, it is still abstract to ensure that each model class can actually
+ * perform generative AI tasks by implementing the corresponding interfaces.
+ *
+ * @since 0.1.0
+ */
+abstract class AbstractApiBasedModel implements ApiBasedModelInterface, WithHttpTransporterInterface, WithRequestAuthenticationInterface
+{
+    use WithHttpTransporterTrait;
+    use WithRequestAuthenticationTrait;
+    /**
+     * @var ModelMetadata The metadata for the model.
+     */
+    private ModelMetadata $metadata;
+    /**
+     * @var ProviderMetadata The metadata for the model's provider.
+     */
+    private ProviderMetadata $providerMetadata;
+    /**
+     * @var ModelConfig The configuration for the model.
+     */
+    private ModelConfig $config;
+    /**
+     * @var RequestOptions|null The request options for HTTP transport.
+     */
+    private ?RequestOptions $requestOptions = null;
+    /**
+     * Constructor.
+     *
+     * @since 0.1.0
+     *
+     * @param ModelMetadata $metadata The metadata for the model.
+     * @param ProviderMetadata $providerMetadata The metadata for the model's provider.
+     */
+    public function __construct(ModelMetadata $metadata, ProviderMetadata $providerMetadata)
+    {
+        $this->metadata = $metadata;
+        $this->providerMetadata = $providerMetadata;
+        $this->config = ModelConfig::fromArray([]);
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    final public function metadata(): ModelMetadata
+    {
+        return $this->metadata;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    final public function providerMetadata(): ProviderMetadata
+    {
+        return $this->providerMetadata;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    final public function setConfig(ModelConfig $config): void
+    {
+        $this->config = $config;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    final public function getConfig(): ModelConfig
+    {
+        return $this->config;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.3.0
+     */
+    final public function setRequestOptions(RequestOptions $requestOptions): void
+    {
+        $this->requestOptions = $requestOptions;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.3.0
+     */
+    final public function getRequestOptions(): ?RequestOptions
+    {
+        return $this->requestOptions;
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/ApiBasedImplementation/AbstractApiBasedModelMetadataDirectory.php b/src/wp-includes/php-ai-client/src/Providers/ApiBasedImplementation/AbstractApiBasedModelMetadataDirectory.php
new file mode 100644
index 0000000000000..4f7e2a338fabc
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/ApiBasedImplementation/AbstractApiBasedModelMetadataDirectory.php
@@ -0,0 +1,105 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\ApiBasedImplementation;
+
+use WordPress\AiClient\AiClient;
+use WordPress\AiClient\Common\Contracts\CachesDataInterface;
+use WordPress\AiClient\Common\Exception\InvalidArgumentException;
+use WordPress\AiClient\Common\Traits\WithDataCachingTrait;
+use WordPress\AiClient\Providers\Contracts\ModelMetadataDirectoryInterface;
+use WordPress\AiClient\Providers\Http\Contracts\WithHttpTransporterInterface;
+use WordPress\AiClient\Providers\Http\Contracts\WithRequestAuthenticationInterface;
+use WordPress\AiClient\Providers\Http\Traits\WithHttpTransporterTrait;
+use WordPress\AiClient\Providers\Http\Traits\WithRequestAuthenticationTrait;
+use WordPress\AiClient\Providers\Models\DTO\ModelMetadata;
+/**
+ * Base class for an API-based model metadata directory for a provider.
+ *
+ * @since 0.1.0
+ */
+abstract class AbstractApiBasedModelMetadataDirectory implements ModelMetadataDirectoryInterface, WithHttpTransporterInterface, WithRequestAuthenticationInterface, CachesDataInterface
+{
+    use WithHttpTransporterTrait;
+    use WithRequestAuthenticationTrait;
+    use WithDataCachingTrait;
+    /**
+     * The cache key suffix for the models list.
+     *
+     * @since 0.4.0
+     *
+     * @var string
+     */
+    private const MODELS_CACHE_KEY = 'models';
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    final public function listModelMetadata(): array
+    {
+        $modelsMetadata = $this->getModelMetadataMap();
+        return array_values($modelsMetadata);
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    final public function hasModelMetadata(string $modelId): bool
+    {
+        $modelsMetadata = $this->getModelMetadataMap();
+        return isset($modelsMetadata[$modelId]);
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    final public function getModelMetadata(string $modelId): ModelMetadata
+    {
+        $modelsMetadata = $this->getModelMetadataMap();
+        if (!isset($modelsMetadata[$modelId])) {
+            throw new InvalidArgumentException(sprintf('No model with ID %s was found in the provider', $modelId));
+        }
+        return $modelsMetadata[$modelId];
+    }
+    /**
+     * Returns the map of model ID to model metadata for all models from the provider.
+     *
+     * @since 0.1.0
+     *
+     * @return array<string, ModelMetadata> Map of model ID to model metadata.
+     */
+    private function getModelMetadataMap(): array
+    {
+        /** @var array<string, ModelMetadata> */
+        return $this->cached(self::MODELS_CACHE_KEY, fn() => $this->sendListModelsRequest(), 86400);
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.4.0
+     */
+    protected function getCachedKeys(): array
+    {
+        return [self::MODELS_CACHE_KEY];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.4.0
+     */
+    protected function getBaseCacheKey(): string
+    {
+        return 'ai_client_' . AiClient::VERSION . '_' . md5(static::class);
+    }
+    /**
+     * Sends the API request to list models from the provider and returns the map of model ID to model metadata.
+     *
+     * @since 0.1.0
+     *
+     * @return array<string, ModelMetadata> Map of model ID to model metadata.
+     */
+    abstract protected function sendListModelsRequest(): array;
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/ApiBasedImplementation/AbstractApiProvider.php b/src/wp-includes/php-ai-client/src/Providers/ApiBasedImplementation/AbstractApiProvider.php
new file mode 100644
index 0000000000000..70a84873a2323
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/ApiBasedImplementation/AbstractApiProvider.php
@@ -0,0 +1,49 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\ApiBasedImplementation;
+
+use WordPress\AiClient\Providers\AbstractProvider;
+/**
+ * Base class for API-based providers.
+ *
+ * This abstract class provides URL construction utilities for providers that
+ * communicate with REST APIs. It standardizes the pattern of combining a base
+ * URL with endpoint paths.
+ *
+ * @since 0.2.0
+ */
+abstract class AbstractApiProvider extends AbstractProvider
+{
+    /**
+     * Gets the base URL for the provider's API.
+     *
+     * The base URL should include the protocol and domain, and may include
+     * the API version path (e.g., "https://api.example.com/v1").
+     *
+     * @since 0.2.0
+     *
+     * @return string The base URL for the provider's API.
+     */
+    abstract protected static function baseUrl(): string;
+    /**
+     * Constructs a full URL by combining the base URL with an optional path.
+     *
+     * This method ensures proper URL construction by:
+     * - Using the provider's base URL
+     * - Trimming leading slashes from the path to prevent double-slashes
+     * - Joining the base URL and path with a single forward slash
+     *
+     * @since 0.2.0
+     *
+     * @param string $path Optional path to append to the base URL. Default empty string.
+     * @return string The complete URL.
+     */
+    public static function url(string $path = ''): string
+    {
+        if ($path === '') {
+            return static::baseUrl();
+        }
+        return static::baseUrl() . '/' . ltrim($path, '/');
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/ApiBasedImplementation/Contracts/ApiBasedModelInterface.php b/src/wp-includes/php-ai-client/src/Providers/ApiBasedImplementation/Contracts/ApiBasedModelInterface.php
new file mode 100644
index 0000000000000..ae0dad04df566
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/ApiBasedImplementation/Contracts/ApiBasedModelInterface.php
@@ -0,0 +1,35 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\ApiBasedImplementation\Contracts;
+
+use WordPress\AiClient\Providers\Http\DTO\RequestOptions;
+use WordPress\AiClient\Providers\Models\Contracts\ModelInterface;
+/**
+ * Interface for API-based AI models that support HTTP transport configuration.
+ *
+ * This interface extends ModelInterface to add request options support
+ * for models that communicate with external APIs via HTTP.
+ *
+ * @since 0.3.0
+ */
+interface ApiBasedModelInterface extends ModelInterface
+{
+    /**
+     * Sets the request options for HTTP transport.
+     *
+     * @since 0.3.0
+     *
+     * @param RequestOptions $requestOptions The request options to use.
+     * @return void
+     */
+    public function setRequestOptions(RequestOptions $requestOptions): void;
+    /**
+     * Gets the request options for HTTP transport.
+     *
+     * @since 0.3.0
+     *
+     * @return RequestOptions|null The request options, or null if not set.
+     */
+    public function getRequestOptions(): ?RequestOptions;
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/ApiBasedImplementation/GenerateTextApiBasedProviderAvailability.php b/src/wp-includes/php-ai-client/src/Providers/ApiBasedImplementation/GenerateTextApiBasedProviderAvailability.php
new file mode 100644
index 0000000000000..f53dc44ed4f82
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/ApiBasedImplementation/GenerateTextApiBasedProviderAvailability.php
@@ -0,0 +1,62 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\ApiBasedImplementation;
+
+use Exception;
+use WordPress\AiClient\Messages\DTO\Message;
+use WordPress\AiClient\Messages\DTO\MessagePart;
+use WordPress\AiClient\Messages\Enums\MessageRoleEnum;
+use WordPress\AiClient\Providers\Contracts\ProviderAvailabilityInterface;
+use WordPress\AiClient\Providers\Models\Contracts\ModelInterface;
+use WordPress\AiClient\Providers\Models\DTO\ModelConfig;
+use WordPress\AiClient\Providers\Models\TextGeneration\Contracts\TextGenerationModelInterface;
+/**
+ * Class to check availability for an API-based provider via a test request to the endpoint to generate text.
+ *
+ * This class should be used for cloud-based providers that do not offer a model listing endpoint, but do offer a
+ * text generation endpoint which requires authentication. A minimal request to this endpoint is used to determine
+ * if the provider is properly configured with valid credentials.
+ *
+ * @since 0.1.0
+ */
+class GenerateTextApiBasedProviderAvailability implements ProviderAvailabilityInterface
+{
+    /**
+     * @var ModelInterface&TextGenerationModelInterface The model to use for checking availability.
+     */
+    private ModelInterface $model;
+    /**
+     * Constructor.
+     *
+     * @since 0.1.0
+     *
+     * @param ModelInterface $model The model to use for checking availability.
+     */
+    public function __construct(ModelInterface $model)
+    {
+        if (!$model instanceof TextGenerationModelInterface) {
+            throw new Exception('The model class to check provider availability must implement TextGenerationModelInterface.');
+        }
+        $this->model = $model;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public function isConfigured(): bool
+    {
+        // Set config to use as few resources as possible for the test.
+        $modelConfig = ModelConfig::fromArray([ModelConfig::KEY_MAX_TOKENS => 1]);
+        $this->model->setConfig($modelConfig);
+        try {
+            // Attempt to generate text to check if the provider is available.
+            $this->model->generateTextResult([new Message(MessageRoleEnum::user(), [new MessagePart('a')])]);
+            return \true;
+        } catch (Exception $e) {
+            // If an exception occurs, the provider is not available.
+            return \false;
+        }
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/ApiBasedImplementation/ListModelsApiBasedProviderAvailability.php b/src/wp-includes/php-ai-client/src/Providers/ApiBasedImplementation/ListModelsApiBasedProviderAvailability.php
new file mode 100644
index 0000000000000..128184e737df8
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/ApiBasedImplementation/ListModelsApiBasedProviderAvailability.php
@@ -0,0 +1,52 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\ApiBasedImplementation;
+
+use Exception;
+use WordPress\AiClient\Providers\Contracts\ModelMetadataDirectoryInterface;
+use WordPress\AiClient\Providers\Contracts\ProviderAvailabilityInterface;
+/**
+ * Class to check availability for an API-based provider via a test request to the endpoint to list models.
+ *
+ * This class should be used for cloud-based providers that offer a model listing endpoint which requires
+ * authentication. A request to this endpoint is used to determine if the provider is properly configured
+ * with valid credentials.
+ *
+ * @since 0.1.0
+ */
+class ListModelsApiBasedProviderAvailability implements ProviderAvailabilityInterface
+{
+    /**
+     * @var ModelMetadataDirectoryInterface The model metadata directory to use for checking availability.
+     */
+    private ModelMetadataDirectoryInterface $modelMetadataDirectory;
+    /**
+     * Constructor.
+     *
+     * @since 0.1.0
+     *
+     * @param ModelMetadataDirectoryInterface $modelMetadataDirectory The model metadata directory to use for checking
+     *                                                                availability.
+     */
+    public function __construct(ModelMetadataDirectoryInterface $modelMetadataDirectory)
+    {
+        $this->modelMetadataDirectory = $modelMetadataDirectory;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public function isConfigured(): bool
+    {
+        try {
+            // Attempt to list models to check if the provider is available.
+            $this->modelMetadataDirectory->listModelMetadata();
+            return \true;
+        } catch (Exception $e) {
+            // If an exception occurs, the provider is not available.
+            return \false;
+        }
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Contracts/ModelMetadataDirectoryInterface.php b/src/wp-includes/php-ai-client/src/Providers/Contracts/ModelMetadataDirectoryInterface.php
new file mode 100644
index 0000000000000..52be8c357c0ff
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Contracts/ModelMetadataDirectoryInterface.php
@@ -0,0 +1,45 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Contracts;
+
+use WordPress\AiClient\Common\Exception\InvalidArgumentException;
+use WordPress\AiClient\Providers\Models\DTO\ModelMetadata;
+/**
+ * Interface for accessing model metadata within a provider.
+ *
+ * Provides methods to list, check, and retrieve model metadata
+ * for all models supported by a provider.
+ *
+ * @since 0.1.0
+ */
+interface ModelMetadataDirectoryInterface
+{
+    /**
+     * Lists all available model metadata.
+     *
+     * @since 0.1.0
+     *
+     * @return list<ModelMetadata> Array of model metadata.
+     */
+    public function listModelMetadata(): array;
+    /**
+     * Checks if metadata exists for a specific model.
+     *
+     * @since 0.1.0
+     *
+     * @param string $modelId Model identifier.
+     * @return bool True if metadata exists, false otherwise.
+     */
+    public function hasModelMetadata(string $modelId): bool;
+    /**
+     * Gets metadata for a specific model.
+     *
+     * @since 0.1.0
+     *
+     * @param string $modelId Model identifier.
+     * @return ModelMetadata Model metadata.
+     * @throws InvalidArgumentException If model metadata not found.
+     */
+    public function getModelMetadata(string $modelId): ModelMetadata;
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Contracts/ProviderAvailabilityInterface.php b/src/wp-includes/php-ai-client/src/Providers/Contracts/ProviderAvailabilityInterface.php
new file mode 100644
index 0000000000000..a5b2737fdb48b
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Contracts/ProviderAvailabilityInterface.php
@@ -0,0 +1,24 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Contracts;
+
+/**
+ * Interface for checking provider availability.
+ *
+ * Determines whether a provider is configured and available
+ * for use based on API keys, credentials, or other requirements.
+ *
+ * @since 0.1.0
+ */
+interface ProviderAvailabilityInterface
+{
+    /**
+     * Checks if the provider is configured.
+     *
+     * @since 0.1.0
+     *
+     * @return bool True if the provider is configured and available, false otherwise.
+     */
+    public function isConfigured(): bool;
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Contracts/ProviderInterface.php b/src/wp-includes/php-ai-client/src/Providers/Contracts/ProviderInterface.php
new file mode 100644
index 0000000000000..737ce9578246a
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Contracts/ProviderInterface.php
@@ -0,0 +1,55 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Contracts;
+
+use WordPress\AiClient\Common\Exception\InvalidArgumentException;
+use WordPress\AiClient\Providers\DTO\ProviderMetadata;
+use WordPress\AiClient\Providers\Models\Contracts\ModelInterface;
+use WordPress\AiClient\Providers\Models\DTO\ModelConfig;
+/**
+ * Interface for AI providers.
+ *
+ * Providers represent AI services (Google, OpenAI, Anthropic, etc.)
+ * and provide access to models, metadata, and availability information.
+ *
+ * @since 0.1.0
+ */
+interface ProviderInterface
+{
+    /**
+     * Gets provider metadata.
+     *
+     * @since 0.1.0
+     *
+     * @return ProviderMetadata Provider metadata.
+     */
+    public static function metadata(): ProviderMetadata;
+    /**
+     * Creates a model instance.
+     *
+     * @since 0.1.0
+     *
+     * @param string $modelId Model identifier.
+     * @param ?ModelConfig $modelConfig Model configuration.
+     * @return ModelInterface Model instance.
+     * @throws InvalidArgumentException If model not found or configuration invalid.
+     */
+    public static function model(string $modelId, ?ModelConfig $modelConfig = null): ModelInterface;
+    /**
+     * Gets provider availability checker.
+     *
+     * @since 0.1.0
+     *
+     * @return ProviderAvailabilityInterface Provider availability checker.
+     */
+    public static function availability(): \WordPress\AiClient\Providers\Contracts\ProviderAvailabilityInterface;
+    /**
+     * Gets model metadata directory.
+     *
+     * @since 0.1.0
+     *
+     * @return ModelMetadataDirectoryInterface Model metadata directory.
+     */
+    public static function modelMetadataDirectory(): \WordPress\AiClient\Providers\Contracts\ModelMetadataDirectoryInterface;
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Contracts/ProviderOperationsHandlerInterface.php b/src/wp-includes/php-ai-client/src/Providers/Contracts/ProviderOperationsHandlerInterface.php
new file mode 100644
index 0000000000000..fb9328cdae747
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Contracts/ProviderOperationsHandlerInterface.php
@@ -0,0 +1,29 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Contracts;
+
+use WordPress\AiClient\Common\Exception\InvalidArgumentException;
+use WordPress\AiClient\Operations\Contracts\OperationInterface;
+/**
+ * Interface for handling provider-level operations.
+ *
+ * Provides methods to retrieve and manage long-running operations
+ * across all models within a provider. Operations are tracked at the
+ * provider level rather than per-model.
+ *
+ * @since 0.1.0
+ */
+interface ProviderOperationsHandlerInterface
+{
+    /**
+     * Gets an operation by ID.
+     *
+     * @since 0.1.0
+     *
+     * @param string $operationId Operation identifier.
+     * @return OperationInterface The operation.
+     * @throws InvalidArgumentException If operation not found.
+     */
+    public function getOperation(string $operationId): OperationInterface;
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Contracts/ProviderWithOperationsHandlerInterface.php b/src/wp-includes/php-ai-client/src/Providers/Contracts/ProviderWithOperationsHandlerInterface.php
new file mode 100644
index 0000000000000..74c409e46e5f4
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Contracts/ProviderWithOperationsHandlerInterface.php
@@ -0,0 +1,24 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Contracts;
+
+/**
+ * Interface for providers that support operations handlers.
+ *
+ * Providers implementing this interface can return an operations handler
+ * for managing long-running operations across all their models.
+ *
+ * @since 0.1.0
+ */
+interface ProviderWithOperationsHandlerInterface
+{
+    /**
+     * Gets the operations handler for this provider.
+     *
+     * @since 0.1.0
+     *
+     * @return ProviderOperationsHandlerInterface The operations handler.
+     */
+    public static function operationsHandler(): \WordPress\AiClient\Providers\Contracts\ProviderOperationsHandlerInterface;
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/DTO/ProviderMetadata.php b/src/wp-includes/php-ai-client/src/Providers/DTO/ProviderMetadata.php
new file mode 100644
index 0000000000000..4191392e0bbbd
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/DTO/ProviderMetadata.php
@@ -0,0 +1,158 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\DTO;
+
+use WordPress\AiClient\Common\AbstractDataTransferObject;
+use WordPress\AiClient\Providers\Enums\ProviderTypeEnum;
+use WordPress\AiClient\Providers\Http\Enums\RequestAuthenticationMethod;
+/**
+ * Represents metadata about an AI provider.
+ *
+ * This class contains information about an AI provider, including its
+ * unique identifier, display name, and type (cloud, server, or client).
+ *
+ * @since 0.1.0
+ *
+ * @phpstan-type ProviderMetadataArrayShape array{
+ *     id: string,
+ *     name: string,
+ *     type: string,
+ *     credentialsUrl?: ?string,
+ *     authenticationMethod?: ?string
+ * }
+ *
+ * @extends AbstractDataTransferObject<ProviderMetadataArrayShape>
+ */
+class ProviderMetadata extends AbstractDataTransferObject
+{
+    public const KEY_ID = 'id';
+    public const KEY_NAME = 'name';
+    public const KEY_TYPE = 'type';
+    public const KEY_CREDENTIALS_URL = 'credentialsUrl';
+    public const KEY_AUTHENTICATION_METHOD = 'authenticationMethod';
+    /**
+     * @var string The provider's unique identifier.
+     */
+    protected string $id;
+    /**
+     * @var string The provider's display name.
+     */
+    protected string $name;
+    /**
+     * @var ProviderTypeEnum The provider type.
+     */
+    protected ProviderTypeEnum $type;
+    /**
+     * @var string|null The URL where users can get credentials.
+     */
+    protected ?string $credentialsUrl;
+    /**
+     * @var RequestAuthenticationMethod|null The authentication method.
+     */
+    protected ?RequestAuthenticationMethod $authenticationMethod;
+    /**
+     * Constructor.
+     *
+     * @since 0.1.0
+     *
+     * @param string $id The provider's unique identifier.
+     * @param string $name The provider's display name.
+     * @param ProviderTypeEnum $type The provider type.
+     * @param string|null $credentialsUrl The URL where users can get credentials.
+     * @param RequestAuthenticationMethod|null $authenticationMethod The authentication method.
+     */
+    public function __construct(string $id, string $name, ProviderTypeEnum $type, ?string $credentialsUrl = null, ?RequestAuthenticationMethod $authenticationMethod = null)
+    {
+        $this->id = $id;
+        $this->name = $name;
+        $this->type = $type;
+        $this->credentialsUrl = $credentialsUrl;
+        $this->authenticationMethod = $authenticationMethod;
+    }
+    /**
+     * Gets the provider's unique identifier.
+     *
+     * @since 0.1.0
+     *
+     * @return string The provider ID.
+     */
+    public function getId(): string
+    {
+        return $this->id;
+    }
+    /**
+     * Gets the provider's display name.
+     *
+     * @since 0.1.0
+     *
+     * @return string The provider name.
+     */
+    public function getName(): string
+    {
+        return $this->name;
+    }
+    /**
+     * Gets the provider type.
+     *
+     * @since 0.1.0
+     *
+     * @return ProviderTypeEnum The provider type.
+     */
+    public function getType(): ProviderTypeEnum
+    {
+        return $this->type;
+    }
+    /**
+     * Gets the credentials URL.
+     *
+     * @since 0.1.0
+     *
+     * @return string|null The credentials URL.
+     */
+    public function getCredentialsUrl(): ?string
+    {
+        return $this->credentialsUrl;
+    }
+    /**
+     * Gets the authentication method.
+     *
+     * @since 0.4.0
+     *
+     * @return RequestAuthenticationMethod|null The authentication method.
+     */
+    public function getAuthenticationMethod(): ?RequestAuthenticationMethod
+    {
+        return $this->authenticationMethod;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function getJsonSchema(): array
+    {
+        return ['type' => 'object', 'properties' => [self::KEY_ID => ['type' => 'string', 'description' => 'The provider\'s unique identifier.'], self::KEY_NAME => ['type' => 'string', 'description' => 'The provider\'s display name.'], self::KEY_TYPE => ['type' => 'string', 'enum' => ProviderTypeEnum::getValues(), 'description' => 'The provider type (cloud, server, or client).'], self::KEY_CREDENTIALS_URL => ['type' => 'string', 'description' => 'The URL where users can get credentials.'], self::KEY_AUTHENTICATION_METHOD => ['type' => ['string', 'null'], 'enum' => array_merge(RequestAuthenticationMethod::getValues(), [null]), 'description' => 'The authentication method.']], 'required' => [self::KEY_ID, self::KEY_NAME, self::KEY_TYPE]];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     *
+     * @return ProviderMetadataArrayShape
+     */
+    public function toArray(): array
+    {
+        return [self::KEY_ID => $this->id, self::KEY_NAME => $this->name, self::KEY_TYPE => $this->type->value, self::KEY_CREDENTIALS_URL => $this->credentialsUrl, self::KEY_AUTHENTICATION_METHOD => $this->authenticationMethod ? $this->authenticationMethod->value : null];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function fromArray(array $array): self
+    {
+        static::validateFromArrayData($array, [self::KEY_ID, self::KEY_NAME, self::KEY_TYPE]);
+        return new self($array[self::KEY_ID], $array[self::KEY_NAME], ProviderTypeEnum::from($array[self::KEY_TYPE]), $array[self::KEY_CREDENTIALS_URL] ?? null, isset($array[self::KEY_AUTHENTICATION_METHOD]) ? RequestAuthenticationMethod::from($array[self::KEY_AUTHENTICATION_METHOD]) : null);
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/DTO/ProviderModelsMetadata.php b/src/wp-includes/php-ai-client/src/Providers/DTO/ProviderModelsMetadata.php
new file mode 100644
index 0000000000000..29d66cab05ec5
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/DTO/ProviderModelsMetadata.php
@@ -0,0 +1,109 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\DTO;
+
+use WordPress\AiClient\Common\AbstractDataTransferObject;
+use WordPress\AiClient\Common\Exception\InvalidArgumentException;
+use WordPress\AiClient\Providers\Models\DTO\ModelMetadata;
+/**
+ * Represents metadata about a provider and its available models.
+ *
+ * This class combines provider information with the models that
+ * the provider offers, facilitating model discovery and selection.
+ *
+ * @since 0.1.0
+ *
+ * @phpstan-import-type ProviderMetadataArrayShape from ProviderMetadata
+ * @phpstan-import-type ModelMetadataArrayShape from ModelMetadata
+ *
+ * @phpstan-type ProviderModelsMetadataArrayShape array{
+ *     provider: ProviderMetadataArrayShape,
+ *     models: list<ModelMetadataArrayShape>
+ * }
+ *
+ * @extends AbstractDataTransferObject<ProviderModelsMetadataArrayShape>
+ */
+class ProviderModelsMetadata extends AbstractDataTransferObject
+{
+    public const KEY_PROVIDER = 'provider';
+    public const KEY_MODELS = 'models';
+    /**
+     * @var ProviderMetadata The provider metadata.
+     */
+    protected \WordPress\AiClient\Providers\DTO\ProviderMetadata $provider;
+    /**
+     * @var list<ModelMetadata> The available models.
+     */
+    protected array $models;
+    /**
+     * Constructor.
+     *
+     * @since 0.1.0
+     *
+     * @param ProviderMetadata $provider The provider metadata.
+     * @param list<ModelMetadata> $models The available models.
+     *
+     * @throws InvalidArgumentException If models is not a list.
+     */
+    public function __construct(\WordPress\AiClient\Providers\DTO\ProviderMetadata $provider, array $models)
+    {
+        if (!array_is_list($models)) {
+            throw new InvalidArgumentException('Models must be a list array.');
+        }
+        $this->provider = $provider;
+        $this->models = $models;
+    }
+    /**
+     * Gets the provider metadata.
+     *
+     * @since 0.1.0
+     *
+     * @return ProviderMetadata The provider metadata.
+     */
+    public function getProvider(): \WordPress\AiClient\Providers\DTO\ProviderMetadata
+    {
+        return $this->provider;
+    }
+    /**
+     * Gets the available models.
+     *
+     * @since 0.1.0
+     *
+     * @return list<ModelMetadata> The available models.
+     */
+    public function getModels(): array
+    {
+        return $this->models;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function getJsonSchema(): array
+    {
+        return ['type' => 'object', 'properties' => [self::KEY_PROVIDER => \WordPress\AiClient\Providers\DTO\ProviderMetadata::getJsonSchema(), self::KEY_MODELS => ['type' => 'array', 'items' => ModelMetadata::getJsonSchema(), 'description' => 'The available models for this provider.']], 'required' => [self::KEY_PROVIDER, self::KEY_MODELS]];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     *
+     * @return ProviderModelsMetadataArrayShape
+     */
+    public function toArray(): array
+    {
+        return [self::KEY_PROVIDER => $this->provider->toArray(), self::KEY_MODELS => array_map(static fn(ModelMetadata $model): array => $model->toArray(), $this->models)];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function fromArray(array $array): self
+    {
+        static::validateFromArrayData($array, [self::KEY_PROVIDER, self::KEY_MODELS]);
+        return new self(\WordPress\AiClient\Providers\DTO\ProviderMetadata::fromArray($array[self::KEY_PROVIDER]), array_map(static fn(array $modelData): ModelMetadata => ModelMetadata::fromArray($modelData), $array[self::KEY_MODELS]));
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Enums/ProviderTypeEnum.php b/src/wp-includes/php-ai-client/src/Providers/Enums/ProviderTypeEnum.php
new file mode 100644
index 0000000000000..c074f673b27bd
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Enums/ProviderTypeEnum.php
@@ -0,0 +1,33 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Enums;
+
+use WordPress\AiClient\Common\AbstractEnum;
+/**
+ * Enum for provider types.
+ *
+ * @since 0.1.0
+ *
+ * @method static self cloud() Creates an instance for CLOUD type.
+ * @method static self server() Creates an instance for SERVER type.
+ * @method static self client() Creates an instance for CLIENT type.
+ * @method bool isCloud() Checks if the type is CLOUD.
+ * @method bool isServer() Checks if the type is SERVER.
+ * @method bool isClient() Checks if the type is CLIENT.
+ */
+class ProviderTypeEnum extends AbstractEnum
+{
+    /**
+     * Cloud-based AI provider (e.g. models available via external REST APIs).
+     */
+    public const CLOUD = 'cloud';
+    /**
+     * Server-side AI provider (e.g. self-hosted models).
+     */
+    public const SERVER = 'server';
+    /**
+     * Client-side AI provider (e.g. browser-based models).
+     */
+    public const CLIENT = 'client';
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Enums/ToolTypeEnum.php b/src/wp-includes/php-ai-client/src/Providers/Enums/ToolTypeEnum.php
new file mode 100644
index 0000000000000..013e9d86ae120
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Enums/ToolTypeEnum.php
@@ -0,0 +1,27 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Enums;
+
+use WordPress\AiClient\Common\AbstractEnum;
+/**
+ * Enum for tool types.
+ *
+ * @since 0.1.0
+ *
+ * @method static self functionDeclarations() Creates an instance for FUNCTION_DECLARATIONS type.
+ * @method static self webSearch() Creates an instance for WEB_SEARCH type.
+ * @method bool isFunctionDeclarations() Checks if the type is FUNCTION_DECLARATIONS.
+ * @method bool isWebSearch() Checks if the type is WEB_SEARCH.
+ */
+class ToolTypeEnum extends AbstractEnum
+{
+    /**
+     * Function declarations tool type.
+     */
+    public const FUNCTION_DECLARATIONS = 'function_declarations';
+    /**
+     * Web search tool type.
+     */
+    public const WEB_SEARCH = 'web_search';
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Http/Collections/HeadersCollection.php b/src/wp-includes/php-ai-client/src/Providers/Http/Collections/HeadersCollection.php
new file mode 100644
index 0000000000000..4fa7178dddf3e
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Http/Collections/HeadersCollection.php
@@ -0,0 +1,134 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Http\Collections;
+
+/**
+ * Simple collection for managing HTTP headers with case-insensitive access.
+ *
+ * This class stores HTTP headers while preserving their original casing
+ * and provides efficient case-insensitive lookups.
+ *
+ * @since 0.1.0
+ */
+class HeadersCollection
+{
+    /**
+     * @var array<string, list<string>> The headers with original casing.
+     */
+    private array $headers = [];
+    /**
+     * @var array<string, string> Map of lowercase header names to actual header names.
+     */
+    private array $headersMap = [];
+    /**
+     * Constructor.
+     *
+     * @since 0.1.0
+     *
+     * @param array<string, string|list<string>> $headers Initial headers.
+     */
+    public function __construct(array $headers = [])
+    {
+        foreach ($headers as $name => $value) {
+            $this->set($name, $value);
+        }
+    }
+    /**
+     * Gets a specific header value.
+     *
+     * @since 0.1.0
+     *
+     * @param string $name The header name (case-insensitive).
+     * @return list<string>|null The header value(s) or null if not found.
+     */
+    public function get(string $name): ?array
+    {
+        $lowerName = strtolower($name);
+        if (!isset($this->headersMap[$lowerName])) {
+            return null;
+        }
+        $actualName = $this->headersMap[$lowerName];
+        return $this->headers[$actualName];
+    }
+    /**
+     * Gets all headers.
+     *
+     * @since 0.1.0
+     *
+     * @return array<string, list<string>> All headers with their original casing.
+     */
+    public function getAll(): array
+    {
+        return $this->headers;
+    }
+    /**
+     * Gets header values as a comma-separated string.
+     *
+     * @since 0.1.0
+     *
+     * @param string $name The header name (case-insensitive).
+     * @return string|null The header values as a comma-separated string or null if not found.
+     */
+    public function getAsString(string $name): ?string
+    {
+        $values = $this->get($name);
+        return $values !== null ? implode(', ', $values) : null;
+    }
+    /**
+     * Checks if a header exists.
+     *
+     * @since 0.1.0
+     *
+     * @param string $name The header name (case-insensitive).
+     * @return bool True if the header exists, false otherwise.
+     */
+    public function has(string $name): bool
+    {
+        return isset($this->headersMap[strtolower($name)]);
+    }
+    /**
+     * Sets a header value, replacing any existing value.
+     *
+     * @since 0.1.0
+     *
+     * @param string $name The header name.
+     * @param string|list<string> $value The header value(s).
+     * @return void
+     */
+    private function set(string $name, $value): void
+    {
+        if (is_array($value)) {
+            $normalizedValues = array_values($value);
+        } else {
+            // Split comma-separated string into array
+            $normalizedValues = array_map('trim', explode(',', $value));
+        }
+        $lowerName = strtolower($name);
+        // If header exists with different casing, remove the old casing
+        if (isset($this->headersMap[$lowerName])) {
+            $oldName = $this->headersMap[$lowerName];
+            if ($oldName !== $name) {
+                unset($this->headers[$oldName]);
+            }
+        }
+        // Always use the new casing
+        $this->headers[$name] = $normalizedValues;
+        $this->headersMap[$lowerName] = $name;
+    }
+    /**
+     * Returns a new instance with the specified header.
+     *
+     * @since 0.1.0
+     *
+     * @param string $name The header name.
+     * @param string|list<string> $value The header value(s).
+     * @return self A new instance with the header.
+     */
+    public function withHeader(string $name, $value): self
+    {
+        $new = clone $this;
+        $new->set($name, $value);
+        return $new;
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Http/Contracts/ClientWithOptionsInterface.php b/src/wp-includes/php-ai-client/src/Providers/Http/Contracts/ClientWithOptionsInterface.php
new file mode 100644
index 0000000000000..b6a088725f3d5
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Http/Contracts/ClientWithOptionsInterface.php
@@ -0,0 +1,29 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Http\Contracts;
+
+use WordPress\AiClientDependencies\Psr\Http\Message\RequestInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\ResponseInterface;
+use WordPress\AiClient\Providers\Http\DTO\RequestOptions;
+/**
+ * Interface for HTTP clients that support per-request transport options.
+ *
+ * Extends the capabilities of PSR-18 clients by allowing custom transport
+ * configuration such as timeouts and redirect handling on each request.
+ *
+ * @since 0.2.0
+ */
+interface ClientWithOptionsInterface
+{
+    /**
+     * Sends an HTTP request with the given transport options.
+     *
+     * @since 0.2.0
+     *
+     * @param RequestInterface $request The PSR-7 request to send.
+     * @param RequestOptions $options The request transport options. Must not be null.
+     * @return ResponseInterface The PSR-7 response received.
+     */
+    public function sendRequestWithOptions(RequestInterface $request, RequestOptions $options): ResponseInterface;
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Http/Contracts/HttpTransporterInterface.php b/src/wp-includes/php-ai-client/src/Providers/Http/Contracts/HttpTransporterInterface.php
new file mode 100644
index 0000000000000..b2bf4b89fd40c
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Http/Contracts/HttpTransporterInterface.php
@@ -0,0 +1,29 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Http\Contracts;
+
+use WordPress\AiClient\Providers\Http\DTO\Request;
+use WordPress\AiClient\Providers\Http\DTO\RequestOptions;
+use WordPress\AiClient\Providers\Http\DTO\Response;
+/**
+ * Interface for HTTP transport implementations.
+ *
+ * Handles sending HTTP requests and receiving responses using
+ * PSR-7, PSR-17, and PSR-18 standards internally.
+ *
+ * @since 0.1.0
+ */
+interface HttpTransporterInterface
+{
+    /**
+     * Sends an HTTP request and returns the response.
+     *
+     * @since 0.1.0
+     *
+     * @param Request $request The request to send.
+     * @param RequestOptions|null $options Optional transport options for the request.
+     * @return Response The response received.
+     */
+    public function send(Request $request, ?RequestOptions $options = null): Response;
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Http/Contracts/RequestAuthenticationInterface.php b/src/wp-includes/php-ai-client/src/Providers/Http/Contracts/RequestAuthenticationInterface.php
new file mode 100644
index 0000000000000..ae2b7b6726df8
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Http/Contracts/RequestAuthenticationInterface.php
@@ -0,0 +1,24 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Http\Contracts;
+
+use WordPress\AiClient\Common\Contracts\WithJsonSchemaInterface;
+use WordPress\AiClient\Providers\Http\DTO\Request;
+/**
+ * Interface for HTTP request authentication.
+ *
+ * @since 0.1.0
+ */
+interface RequestAuthenticationInterface extends WithJsonSchemaInterface
+{
+    /**
+     * Authenticates an HTTP request.
+     *
+     * @since 0.1.0
+     *
+     * @param Request $request The request to authenticate.
+     * @return Request The authenticated request.
+     */
+    public function authenticateRequest(Request $request): Request;
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Http/Contracts/WithHttpTransporterInterface.php b/src/wp-includes/php-ai-client/src/Providers/Http/Contracts/WithHttpTransporterInterface.php
new file mode 100644
index 0000000000000..5c46b46aef2ea
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Http/Contracts/WithHttpTransporterInterface.php
@@ -0,0 +1,30 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Http\Contracts;
+
+/**
+ * Interface for models that require HTTP transport capabilities.
+ *
+ * @since 0.1.0
+ */
+interface WithHttpTransporterInterface
+{
+    /**
+     * Sets the HTTP transporter.
+     *
+     * @since 0.1.0
+     *
+     * @param HttpTransporterInterface $transporter The HTTP transporter instance.
+     * @return void
+     */
+    public function setHttpTransporter(\WordPress\AiClient\Providers\Http\Contracts\HttpTransporterInterface $transporter): void;
+    /**
+     * Returns the HTTP transporter.
+     *
+     * @since 0.1.0
+     *
+     * @return HttpTransporterInterface The HTTP transporter instance.
+     */
+    public function getHttpTransporter(): \WordPress\AiClient\Providers\Http\Contracts\HttpTransporterInterface;
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Http/Contracts/WithRequestAuthenticationInterface.php b/src/wp-includes/php-ai-client/src/Providers/Http/Contracts/WithRequestAuthenticationInterface.php
new file mode 100644
index 0000000000000..419f48faf74c0
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Http/Contracts/WithRequestAuthenticationInterface.php
@@ -0,0 +1,30 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Http\Contracts;
+
+/**
+ * Interface for models that support request authentication.
+ *
+ * @since 0.1.0
+ */
+interface WithRequestAuthenticationInterface
+{
+    /**
+     * Sets the request authentication.
+     *
+     * @since 0.1.0
+     *
+     * @param RequestAuthenticationInterface $authentication The authentication instance.
+     * @return void
+     */
+    public function setRequestAuthentication(\WordPress\AiClient\Providers\Http\Contracts\RequestAuthenticationInterface $authentication): void;
+    /**
+     * Returns the request authentication.
+     *
+     * @since 0.1.0
+     *
+     * @return RequestAuthenticationInterface The authentication instance.
+     */
+    public function getRequestAuthentication(): \WordPress\AiClient\Providers\Http\Contracts\RequestAuthenticationInterface;
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Http/DTO/ApiKeyRequestAuthentication.php b/src/wp-includes/php-ai-client/src/Providers/Http/DTO/ApiKeyRequestAuthentication.php
new file mode 100644
index 0000000000000..f002b26f802a7
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Http/DTO/ApiKeyRequestAuthentication.php
@@ -0,0 +1,92 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Http\DTO;
+
+use WordPress\AiClient\Common\AbstractDataTransferObject;
+use WordPress\AiClient\Providers\Http\Contracts\RequestAuthenticationInterface;
+/**
+ * Class for HTTP request authentication using an API key.
+ *
+ * @since 0.1.0
+ *
+ * @phpstan-type ApiKeyRequestAuthenticationArrayShape array{
+ *     apiKey: string
+ * }
+ *
+ * @extends AbstractDataTransferObject<ApiKeyRequestAuthenticationArrayShape>
+ */
+class ApiKeyRequestAuthentication extends AbstractDataTransferObject implements RequestAuthenticationInterface
+{
+    public const KEY_API_KEY = 'apiKey';
+    /**
+     * @var string The API key used for authentication.
+     */
+    protected string $apiKey;
+    /**
+     * Constructor.
+     *
+     * @since 0.1.0
+     *
+     * @param string $apiKey The API key used for authentication.
+     */
+    public function __construct(string $apiKey)
+    {
+        $this->apiKey = $apiKey;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public function authenticateRequest(\WordPress\AiClient\Providers\Http\DTO\Request $request): \WordPress\AiClient\Providers\Http\DTO\Request
+    {
+        // Add the API key to the request headers.
+        return $request->withHeader('Authorization', 'Bearer ' . $this->apiKey);
+    }
+    /**
+     * Gets the API key.
+     *
+     * @since 0.1.0
+     *
+     * @return string The API key.
+     */
+    public function getApiKey(): string
+    {
+        return $this->apiKey;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     *
+     * @since 0.1.0
+     *
+     * @return ApiKeyRequestAuthenticationArrayShape
+     */
+    public function toArray(): array
+    {
+        return [self::KEY_API_KEY => $this->apiKey];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     *
+     * @since 0.1.0
+     */
+    public static function fromArray(array $array): self
+    {
+        static::validateFromArrayData($array, [self::KEY_API_KEY]);
+        return new self($array[self::KEY_API_KEY]);
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function getJsonSchema(): array
+    {
+        return ['type' => 'object', 'properties' => [self::KEY_API_KEY => ['type' => 'string', 'title' => 'API Key', 'description' => 'The API key used for authentication.']], 'required' => [self::KEY_API_KEY]];
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Http/DTO/Request.php b/src/wp-includes/php-ai-client/src/Providers/Http/DTO/Request.php
new file mode 100644
index 0000000000000..8d62f01746632
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Http/DTO/Request.php
@@ -0,0 +1,358 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Http\DTO;
+
+use JsonException;
+use WordPress\AiClientDependencies\Psr\Http\Message\RequestInterface;
+use WordPress\AiClient\Common\AbstractDataTransferObject;
+use WordPress\AiClient\Common\Exception\InvalidArgumentException;
+use WordPress\AiClient\Providers\Http\Collections\HeadersCollection;
+use WordPress\AiClient\Providers\Http\Enums\HttpMethodEnum;
+/**
+ * Represents an HTTP request.
+ *
+ * This class encapsulates HTTP request data that can be converted
+ * to PSR-7 requests by the HTTP transporter.
+ *
+ * @since 0.1.0
+ *
+ * @phpstan-import-type RequestOptionsArrayShape from RequestOptions
+ * @phpstan-type RequestArrayShape array{
+ *     method: string,
+ *     uri: string,
+ *     headers: array<string, list<string>>,
+ *     body?: string|null,
+ *     options?: RequestOptionsArrayShape
+ * }
+ *
+ * @extends AbstractDataTransferObject<RequestArrayShape>
+ */
+class Request extends AbstractDataTransferObject
+{
+    public const KEY_METHOD = 'method';
+    public const KEY_URI = 'uri';
+    public const KEY_HEADERS = 'headers';
+    public const KEY_BODY = 'body';
+    public const KEY_OPTIONS = 'options';
+    /**
+     * @var HttpMethodEnum The HTTP method.
+     */
+    protected HttpMethodEnum $method;
+    /**
+     * @var string The request URI.
+     */
+    protected string $uri;
+    /**
+     * @var HeadersCollection The request headers.
+     */
+    protected HeadersCollection $headers;
+    /**
+     * @var array<string, mixed>|null The request data (for query params or form data).
+     */
+    protected ?array $data = null;
+    /**
+     * @var string|null The request body (raw string content).
+     */
+    protected ?string $body = null;
+    /**
+     * @var RequestOptions|null Request transport options.
+     */
+    protected ?\WordPress\AiClient\Providers\Http\DTO\RequestOptions $options = null;
+    /**
+     * Constructor.
+     *
+     * @since 0.1.0
+     *
+     * @param HttpMethodEnum $method The HTTP method.
+     * @param string $uri The request URI.
+     * @param array<string, string|list<string>> $headers The request headers.
+     * @param string|array<string, mixed>|null $data The request data.
+     * @param RequestOptions|null $options The request transport options.
+     *
+     * @throws InvalidArgumentException If the URI is empty.
+     */
+    public function __construct(HttpMethodEnum $method, string $uri, array $headers = [], $data = null, ?\WordPress\AiClient\Providers\Http\DTO\RequestOptions $options = null)
+    {
+        if (empty($uri)) {
+            throw new InvalidArgumentException('URI cannot be empty.');
+        }
+        $this->method = $method;
+        $this->uri = $uri;
+        $this->headers = new HeadersCollection($headers);
+        // Separate data and body based on type
+        if (is_string($data)) {
+            $this->body = $data;
+        } elseif (is_array($data)) {
+            $this->data = $data;
+        }
+        $this->options = $options;
+    }
+    /**
+     * Gets the HTTP method.
+     *
+     * @since 0.1.0
+     *
+     * @return HttpMethodEnum The HTTP method.
+     */
+    public function getMethod(): HttpMethodEnum
+    {
+        return $this->method;
+    }
+    /**
+     * Gets the request URI.
+     *
+     * For GET requests with array data, appends the data as query parameters.
+     *
+     * @since 0.1.0
+     *
+     * @return string The URI.
+     */
+    public function getUri(): string
+    {
+        // If GET request with data, append as query parameters
+        if ($this->method === HttpMethodEnum::GET() && $this->data !== null && !empty($this->data)) {
+            $separator = str_contains($this->uri, '?') ? '&' : '?';
+            return $this->uri . $separator . http_build_query($this->data);
+        }
+        return $this->uri;
+    }
+    /**
+     * Gets the request headers.
+     *
+     * @since 0.1.0
+     *
+     * @return array<string, list<string>> The headers.
+     */
+    public function getHeaders(): array
+    {
+        return $this->headers->getAll();
+    }
+    /**
+     * Gets a specific header value.
+     *
+     * @since 0.1.0
+     *
+     * @param string $name The header name (case-insensitive).
+     * @return list<string>|null The header value(s) or null if not found.
+     */
+    public function getHeader(string $name): ?array
+    {
+        return $this->headers->get($name);
+    }
+    /**
+     * Gets header values as a comma-separated string.
+     *
+     * @since 0.1.0
+     *
+     * @param string $name The header name (case-insensitive).
+     * @return string|null The header values as a comma-separated string, or null if not found.
+     */
+    public function getHeaderAsString(string $name): ?string
+    {
+        return $this->headers->getAsString($name);
+    }
+    /**
+     * Checks if a header exists.
+     *
+     * @since 0.1.0
+     *
+     * @param string $name The header name (case-insensitive).
+     * @return bool True if the header exists, false otherwise.
+     */
+    public function hasHeader(string $name): bool
+    {
+        return $this->headers->has($name);
+    }
+    /**
+     * Gets the request body.
+     *
+     * For GET requests, returns null.
+     * For POST/PUT/PATCH requests:
+     * - If body is set, returns it as-is
+     * - If data is set and Content-Type is JSON, returns JSON-encoded data
+     * - If data is set and Content-Type is form, returns URL-encoded data
+     *
+     * @since 0.1.0
+     *
+     * @return string|null The body.
+     * @throws JsonException If the data cannot be encoded to JSON.
+     */
+    public function getBody(): ?string
+    {
+        // GET requests don't have a body
+        if (!$this->method->hasBody()) {
+            return null;
+        }
+        // If body is set, return it as-is
+        if ($this->body !== null) {
+            return $this->body;
+        }
+        // If data is set, encode based on content type
+        if ($this->data !== null) {
+            $contentType = $this->getContentType();
+            // JSON encoding
+            if ($contentType !== null && stripos($contentType, 'application/json') !== \false) {
+                return json_encode($this->data, \JSON_THROW_ON_ERROR);
+            }
+            // Default to URL encoding for forms
+            return http_build_query($this->data);
+        }
+        return null;
+    }
+    /**
+     * Gets the Content-Type header value.
+     *
+     * @since 0.1.0
+     *
+     * @return string|null The Content-Type header value or null if not set.
+     */
+    private function getContentType(): ?string
+    {
+        $values = $this->getHeader('Content-Type');
+        return $values !== null ? $values[0] : null;
+    }
+    /**
+     * Returns a new instance with the specified header.
+     *
+     * @since 0.1.0
+     *
+     * @param string $name The header name.
+     * @param string|list<string> $value The header value(s).
+     * @return self A new instance with the header.
+     */
+    public function withHeader(string $name, $value): self
+    {
+        $newHeaders = $this->headers->withHeader($name, $value);
+        $new = clone $this;
+        $new->headers = $newHeaders;
+        return $new;
+    }
+    /**
+     * Returns a new instance with the specified data.
+     *
+     * @since 0.1.0
+     *
+     * @param string|array<string, mixed> $data The request data.
+     * @return self A new instance with the data.
+     */
+    public function withData($data): self
+    {
+        $new = clone $this;
+        if (is_string($data)) {
+            $new->body = $data;
+            $new->data = null;
+        } elseif (is_array($data)) {
+            $new->data = $data;
+            $new->body = null;
+        } else {
+            $new->data = null;
+            $new->body = null;
+        }
+        return $new;
+    }
+    /**
+     * Gets the request data array.
+     *
+     * @since 0.1.0
+     *
+     * @return array<string, mixed>|null The request data array.
+     */
+    public function getData(): ?array
+    {
+        return $this->data;
+    }
+    /**
+     * Gets the request options.
+     *
+     * @since 0.2.0
+     *
+     * @return RequestOptions|null Request transport options when configured.
+     */
+    public function getOptions(): ?\WordPress\AiClient\Providers\Http\DTO\RequestOptions
+    {
+        return $this->options;
+    }
+    /**
+     * Returns a new instance with the specified request options.
+     *
+     * @since 0.2.0
+     *
+     * @param RequestOptions|null $options The request options to apply.
+     * @return self A new instance with the options.
+     */
+    public function withOptions(?\WordPress\AiClient\Providers\Http\DTO\RequestOptions $options): self
+    {
+        $new = clone $this;
+        $new->options = $options;
+        return $new;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function getJsonSchema(): array
+    {
+        return ['type' => 'object', 'properties' => [self::KEY_METHOD => ['type' => 'string', 'description' => 'The HTTP method.'], self::KEY_URI => ['type' => 'string', 'description' => 'The request URI.'], self::KEY_HEADERS => ['type' => 'object', 'additionalProperties' => ['type' => 'array', 'items' => ['type' => 'string']], 'description' => 'The request headers.'], self::KEY_BODY => ['type' => ['string'], 'description' => 'The request body.'], self::KEY_OPTIONS => \WordPress\AiClient\Providers\Http\DTO\RequestOptions::getJsonSchema()], 'required' => [self::KEY_METHOD, self::KEY_URI, self::KEY_HEADERS]];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     *
+     * @return RequestArrayShape
+     */
+    public function toArray(): array
+    {
+        $array = [
+            self::KEY_METHOD => $this->method->value,
+            self::KEY_URI => $this->getUri(),
+            // Include query params if GET with data
+            self::KEY_HEADERS => $this->headers->getAll(),
+        ];
+        // Include body if present (getBody() handles the conversion)
+        $body = $this->getBody();
+        if ($body !== null) {
+            $array[self::KEY_BODY] = $body;
+        }
+        if ($this->options !== null) {
+            $optionsArray = $this->options->toArray();
+            if (!empty($optionsArray)) {
+                $array[self::KEY_OPTIONS] = $optionsArray;
+            }
+        }
+        return $array;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function fromArray(array $array): self
+    {
+        static::validateFromArrayData($array, [self::KEY_METHOD, self::KEY_URI, self::KEY_HEADERS]);
+        return new self(HttpMethodEnum::from($array[self::KEY_METHOD]), $array[self::KEY_URI], $array[self::KEY_HEADERS] ?? [], $array[self::KEY_BODY] ?? null, isset($array[self::KEY_OPTIONS]) ? \WordPress\AiClient\Providers\Http\DTO\RequestOptions::fromArray($array[self::KEY_OPTIONS]) : null);
+    }
+    /**
+     * Creates a Request instance from a PSR-7 RequestInterface.
+     *
+     * @since 0.2.0
+     *
+     * @param RequestInterface $psrRequest The PSR-7 request to convert.
+     * @return self A new Request instance.
+     * @throws InvalidArgumentException If the HTTP method is not supported.
+     */
+    public static function fromPsrRequest(RequestInterface $psrRequest): self
+    {
+        $method = HttpMethodEnum::from($psrRequest->getMethod());
+        $uri = (string) $psrRequest->getUri();
+        // Convert PSR-7 headers to array format expected by our constructor
+        /** @var array<string, list<string>> $headers */
+        $headers = $psrRequest->getHeaders();
+        // Get body content
+        $body = $psrRequest->getBody()->getContents();
+        $bodyOrData = !empty($body) ? $body : null;
+        return new self($method, $uri, $headers, $bodyOrData);
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Http/DTO/RequestOptions.php b/src/wp-includes/php-ai-client/src/Providers/Http/DTO/RequestOptions.php
new file mode 100644
index 0000000000000..c787c791df769
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Http/DTO/RequestOptions.php
@@ -0,0 +1,204 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Http\DTO;
+
+use WordPress\AiClient\Common\AbstractDataTransferObject;
+use WordPress\AiClient\Common\Exception\InvalidArgumentException;
+/**
+ * Represents optional HTTP transport configuration for a single request.
+ *
+ * Provides mutable setters for working with timeouts and redirect handling.
+ *
+ * @since 0.2.0
+ *
+ * @phpstan-type RequestOptionsArrayShape array{
+ *     timeout?: float|null,
+ *     connectTimeout?: float|null,
+ *     maxRedirects?: int|null
+ * }
+ *
+ * @extends AbstractDataTransferObject<RequestOptionsArrayShape>
+ */
+class RequestOptions extends AbstractDataTransferObject
+{
+    public const KEY_TIMEOUT = 'timeout';
+    public const KEY_CONNECT_TIMEOUT = 'connectTimeout';
+    public const KEY_MAX_REDIRECTS = 'maxRedirects';
+    /**
+     * @var float|null Maximum duration in seconds to wait for the full response.
+     */
+    protected ?float $timeout = null;
+    /**
+     * @var float|null Maximum duration in seconds to wait for the initial connection.
+     */
+    protected ?float $connectTimeout = null;
+    /**
+     * @var int|null Maximum number of redirects to follow. 0 disables redirects, null is unspecified.
+     */
+    protected ?int $maxRedirects = null;
+    /**
+     * Sets the request timeout in seconds.
+     *
+     * @since 0.2.0
+     *
+     * @param float|null $timeout Timeout in seconds.
+     * @return void
+     *
+     * @throws InvalidArgumentException When timeout is negative.
+     */
+    public function setTimeout(?float $timeout): void
+    {
+        $this->validateTimeout($timeout, self::KEY_TIMEOUT);
+        $this->timeout = $timeout;
+    }
+    /**
+     * Sets the connection timeout in seconds.
+     *
+     * @since 0.2.0
+     *
+     * @param float|null $timeout Connection timeout in seconds.
+     * @return void
+     *
+     * @throws InvalidArgumentException When timeout is negative.
+     */
+    public function setConnectTimeout(?float $timeout): void
+    {
+        $this->validateTimeout($timeout, self::KEY_CONNECT_TIMEOUT);
+        $this->connectTimeout = $timeout;
+    }
+    /**
+     * Sets the maximum number of redirects to follow.
+     *
+     * Set to 0 to disable redirects, null for unspecified, or a positive integer
+     * to enable redirects with a maximum count.
+     *
+     * @since 0.2.0
+     *
+     * @param int|null $maxRedirects Maximum redirects to follow, or 0 to disable, or null for unspecified.
+     * @return void
+     *
+     * @throws InvalidArgumentException When redirect count is negative.
+     */
+    public function setMaxRedirects(?int $maxRedirects): void
+    {
+        if ($maxRedirects !== null && $maxRedirects < 0) {
+            throw new InvalidArgumentException('Request option "maxRedirects" must be greater than or equal to 0.');
+        }
+        $this->maxRedirects = $maxRedirects;
+    }
+    /**
+     * Gets the request timeout in seconds.
+     *
+     * @since 0.2.0
+     *
+     * @return float|null Timeout in seconds.
+     */
+    public function getTimeout(): ?float
+    {
+        return $this->timeout;
+    }
+    /**
+     * Gets the connection timeout in seconds.
+     *
+     * @since 0.2.0
+     *
+     * @return float|null Connection timeout in seconds.
+     */
+    public function getConnectTimeout(): ?float
+    {
+        return $this->connectTimeout;
+    }
+    /**
+     * Checks whether redirects are allowed.
+     *
+     * @since 0.2.0
+     *
+     * @return bool|null True when redirects are allowed (maxRedirects > 0),
+     *                   false when disabled (maxRedirects = 0),
+     *                   null when unspecified (maxRedirects = null).
+     */
+    public function allowsRedirects(): ?bool
+    {
+        if ($this->maxRedirects === null) {
+            return null;
+        }
+        return $this->maxRedirects > 0;
+    }
+    /**
+     * Gets the maximum number of redirects to follow.
+     *
+     * @since 0.2.0
+     *
+     * @return int|null Maximum redirects or null when not specified.
+     */
+    public function getMaxRedirects(): ?int
+    {
+        return $this->maxRedirects;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.2.0
+     *
+     * @return RequestOptionsArrayShape
+     */
+    public function toArray(): array
+    {
+        $data = [];
+        if ($this->timeout !== null) {
+            $data[self::KEY_TIMEOUT] = $this->timeout;
+        }
+        if ($this->connectTimeout !== null) {
+            $data[self::KEY_CONNECT_TIMEOUT] = $this->connectTimeout;
+        }
+        if ($this->maxRedirects !== null) {
+            $data[self::KEY_MAX_REDIRECTS] = $this->maxRedirects;
+        }
+        return $data;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.2.0
+     */
+    public static function fromArray(array $array): self
+    {
+        $instance = new self();
+        if (isset($array[self::KEY_TIMEOUT])) {
+            $instance->setTimeout((float) $array[self::KEY_TIMEOUT]);
+        }
+        if (isset($array[self::KEY_CONNECT_TIMEOUT])) {
+            $instance->setConnectTimeout((float) $array[self::KEY_CONNECT_TIMEOUT]);
+        }
+        if (isset($array[self::KEY_MAX_REDIRECTS])) {
+            $instance->setMaxRedirects((int) $array[self::KEY_MAX_REDIRECTS]);
+        }
+        return $instance;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.2.0
+     */
+    public static function getJsonSchema(): array
+    {
+        return ['type' => 'object', 'properties' => [self::KEY_TIMEOUT => ['type' => ['number', 'null'], 'minimum' => 0, 'description' => 'Maximum duration in seconds to wait for the full response.'], self::KEY_CONNECT_TIMEOUT => ['type' => ['number', 'null'], 'minimum' => 0, 'description' => 'Maximum duration in seconds to wait for the initial connection.'], self::KEY_MAX_REDIRECTS => ['type' => ['integer', 'null'], 'minimum' => 0, 'description' => 'Maximum redirects to follow. 0 disables, null is unspecified.']], 'additionalProperties' => \false];
+    }
+    /**
+     * Validates timeout values.
+     *
+     * @since 0.2.0
+     *
+     * @param float|null $value Timeout to validate.
+     * @param string $fieldName Field name for the error message.
+     *
+     * @throws InvalidArgumentException When timeout is negative.
+     */
+    private function validateTimeout(?float $value, string $fieldName): void
+    {
+        if ($value !== null && $value < 0) {
+            throw new InvalidArgumentException(sprintf('Request option "%s" must be greater than or equal to 0.', $fieldName));
+        }
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Http/DTO/Response.php b/src/wp-includes/php-ai-client/src/Providers/Http/DTO/Response.php
new file mode 100644
index 0000000000000..73442ca456593
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Http/DTO/Response.php
@@ -0,0 +1,198 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Http\DTO;
+
+use WordPress\AiClient\Common\AbstractDataTransferObject;
+use WordPress\AiClient\Common\Exception\InvalidArgumentException;
+use WordPress\AiClient\Providers\Http\Collections\HeadersCollection;
+/**
+ * Represents an HTTP response.
+ *
+ * This class encapsulates HTTP response data that has been converted
+ * from PSR-7 responses by the HTTP transporter.
+ *
+ * @since 0.1.0
+ *
+ * @phpstan-type ResponseArrayShape array{
+ *     statusCode: int,
+ *     headers: array<string, list<string>>,
+ *     body?: string|null
+ * }
+ *
+ * @extends AbstractDataTransferObject<ResponseArrayShape>
+ */
+class Response extends AbstractDataTransferObject
+{
+    public const KEY_STATUS_CODE = 'statusCode';
+    public const KEY_HEADERS = 'headers';
+    public const KEY_BODY = 'body';
+    /**
+     * @var int The HTTP status code.
+     */
+    protected int $statusCode;
+    /**
+     * @var HeadersCollection The response headers.
+     */
+    protected HeadersCollection $headers;
+    /**
+     * @var string|null The response body.
+     */
+    protected ?string $body;
+    /**
+     * Constructor.
+     *
+     * @since 0.1.0
+     *
+     * @param int $statusCode The HTTP status code.
+     * @param array<string, string|list<string>> $headers The response headers.
+     * @param string|null $body The response body.
+     *
+     * @throws InvalidArgumentException If the status code is invalid.
+     */
+    public function __construct(int $statusCode, array $headers, ?string $body = null)
+    {
+        if ($statusCode < 100 || $statusCode >= 600) {
+            throw new InvalidArgumentException('Invalid HTTP status code: ' . $statusCode);
+        }
+        $this->statusCode = $statusCode;
+        $this->headers = new HeadersCollection($headers);
+        $this->body = $body;
+    }
+    /**
+     * Gets the HTTP status code.
+     *
+     * @since 0.1.0
+     *
+     * @return int The status code.
+     */
+    public function getStatusCode(): int
+    {
+        return $this->statusCode;
+    }
+    /**
+     * Gets the response headers.
+     *
+     * @since 0.1.0
+     *
+     * @return array<string, list<string>> The headers.
+     */
+    public function getHeaders(): array
+    {
+        return $this->headers->getAll();
+    }
+    /**
+     * Gets a specific header value.
+     *
+     * @since 0.1.0
+     *
+     * @param string $name The header name (case-insensitive).
+     * @return list<string>|null The header value(s) or null if not found.
+     */
+    public function getHeader(string $name): ?array
+    {
+        return $this->headers->get($name);
+    }
+    /**
+     * Gets header values as a comma-separated string.
+     *
+     * @since 0.1.0
+     *
+     * @param string $name The header name (case-insensitive).
+     * @return string|null The header values as a comma-separated string or null if not found.
+     */
+    public function getHeaderAsString(string $name): ?string
+    {
+        return $this->headers->getAsString($name);
+    }
+    /**
+     * Gets the response body.
+     *
+     * @since 0.1.0
+     *
+     * @return string|null The body.
+     */
+    public function getBody(): ?string
+    {
+        return $this->body;
+    }
+    /**
+     * Checks if the response has a header.
+     *
+     * @since 0.1.0
+     *
+     * @param string $name The header name.
+     * @return bool True if the header exists, false otherwise.
+     */
+    public function hasHeader(string $name): bool
+    {
+        return $this->headers->has($name);
+    }
+    /**
+     * Checks if the response indicates success.
+     *
+     * @since 0.1.0
+     *
+     * @return bool True if status code is 2xx, false otherwise.
+     */
+    public function isSuccessful(): bool
+    {
+        return $this->statusCode >= 200 && $this->statusCode < 300;
+    }
+    /**
+     * Gets the response data as an array.
+     *
+     * Attempts to decode the body as JSON. Returns null if the body
+     * is empty or not valid JSON.
+     *
+     * @since 0.1.0
+     *
+     * @return array<string, mixed>|null The decoded data or null.
+     */
+    public function getData(): ?array
+    {
+        if ($this->body === null || $this->body === '') {
+            return null;
+        }
+        $data = json_decode($this->body, \true);
+        if (json_last_error() !== \JSON_ERROR_NONE) {
+            return null;
+        }
+        /** @var array<string, mixed>|null $data */
+        return is_array($data) ? $data : null;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function getJsonSchema(): array
+    {
+        return ['type' => 'object', 'properties' => [self::KEY_STATUS_CODE => ['type' => 'integer', 'minimum' => 100, 'maximum' => 599, 'description' => 'The HTTP status code.'], self::KEY_HEADERS => ['type' => 'object', 'additionalProperties' => ['type' => 'array', 'items' => ['type' => 'string']], 'description' => 'The response headers.'], self::KEY_BODY => ['type' => ['string', 'null'], 'description' => 'The response body.']], 'required' => [self::KEY_STATUS_CODE, self::KEY_HEADERS]];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     *
+     * @return ResponseArrayShape
+     */
+    public function toArray(): array
+    {
+        $data = [self::KEY_STATUS_CODE => $this->statusCode, self::KEY_HEADERS => $this->headers->getAll()];
+        if ($this->body !== null) {
+            $data[self::KEY_BODY] = $this->body;
+        }
+        return $data;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function fromArray(array $array): self
+    {
+        static::validateFromArrayData($array, [self::KEY_STATUS_CODE, self::KEY_HEADERS]);
+        return new self($array[self::KEY_STATUS_CODE], $array[self::KEY_HEADERS], $array[self::KEY_BODY] ?? null);
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Http/Enums/HttpMethodEnum.php b/src/wp-includes/php-ai-client/src/Providers/Http/Enums/HttpMethodEnum.php
new file mode 100644
index 0000000000000..42520c949cd6e
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Http/Enums/HttpMethodEnum.php
@@ -0,0 +1,110 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Http\Enums;
+
+use WordPress\AiClient\Common\AbstractEnum;
+/**
+ * Represents HTTP request methods.
+ *
+ * @since 0.1.0
+ *
+ * @method static self GET()
+ * @method static self POST()
+ * @method static self PUT()
+ * @method static self PATCH()
+ * @method static self DELETE()
+ * @method static self HEAD()
+ * @method static self OPTIONS()
+ * @method static self CONNECT()
+ * @method static self TRACE()
+ *
+ * @method bool isGet()
+ * @method bool isPost()
+ * @method bool isPut()
+ * @method bool isPatch()
+ * @method bool isDelete()
+ * @method bool isHead()
+ * @method bool isOptions()
+ * @method bool isConnect()
+ * @method bool isTrace()
+ */
+final class HttpMethodEnum extends AbstractEnum
+{
+    /**
+     * GET method for retrieving resources.
+     *
+     * @var string
+     */
+    public const GET = 'GET';
+    /**
+     * POST method for creating resources.
+     *
+     * @var string
+     */
+    public const POST = 'POST';
+    /**
+     * PUT method for updating/replacing resources.
+     *
+     * @var string
+     */
+    public const PUT = 'PUT';
+    /**
+     * PATCH method for partially updating resources.
+     *
+     * @var string
+     */
+    public const PATCH = 'PATCH';
+    /**
+     * DELETE method for removing resources.
+     *
+     * @var string
+     */
+    public const DELETE = 'DELETE';
+    /**
+     * HEAD method for retrieving headers only.
+     *
+     * @var string
+     */
+    public const HEAD = 'HEAD';
+    /**
+     * OPTIONS method for retrieving allowed methods.
+     *
+     * @var string
+     */
+    public const OPTIONS = 'OPTIONS';
+    /**
+     * CONNECT method for establishing tunnel.
+     *
+     * @var string
+     */
+    public const CONNECT = 'CONNECT';
+    /**
+     * TRACE method for diagnostic purposes.
+     *
+     * @var string
+     */
+    public const TRACE = 'TRACE';
+    /**
+     * Checks if this method is idempotent.
+     *
+     * @since 0.1.0
+     *
+     * @return bool True if the method is idempotent, false otherwise.
+     */
+    public function isIdempotent(): bool
+    {
+        return in_array($this->value, [self::GET, self::HEAD, self::OPTIONS, self::TRACE, self::PUT, self::DELETE], \true);
+    }
+    /**
+     * Checks if this method typically has a request body.
+     *
+     * @since 0.1.0
+     *
+     * @return bool True if the method typically has a body, false otherwise.
+     */
+    public function hasBody(): bool
+    {
+        return in_array($this->value, [self::POST, self::PUT, self::PATCH], \true);
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Http/Enums/RequestAuthenticationMethod.php b/src/wp-includes/php-ai-client/src/Providers/Http/Enums/RequestAuthenticationMethod.php
new file mode 100644
index 0000000000000..e43eb027579c4
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Http/Enums/RequestAuthenticationMethod.php
@@ -0,0 +1,39 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Http\Enums;
+
+use WordPress\AiClient\Common\AbstractEnum;
+use WordPress\AiClient\Common\Contracts\WithArrayTransformationInterface;
+use WordPress\AiClient\Providers\Http\Contracts\RequestAuthenticationInterface;
+use WordPress\AiClient\Providers\Http\DTO\ApiKeyRequestAuthentication;
+/**
+ * Enum for request authentication methods.
+ *
+ * @since 0.4.0
+ *
+ * @method static self apiKey() Creates an instance for API_KEY method.
+ * @method bool isApiKey() Checks if the method is API_KEY.
+ */
+class RequestAuthenticationMethod extends AbstractEnum
+{
+    /**
+     * API key authentication.
+     */
+    public const API_KEY = 'api_key';
+    /**
+     * Gets the implementation class for the authentication method.
+     *
+     * @since 0.4.0
+     *
+     * @return class-string<RequestAuthenticationInterface&WithArrayTransformationInterface> The implementation class.
+     *
+     * @phpstan-ignore missingType.generics
+     */
+    public function getImplementationClass(): string
+    {
+        // At the moment, this is the only supported method.
+        // Once more methods are available, add conditionals here for each method.
+        return ApiKeyRequestAuthentication::class;
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Http/Exception/ClientException.php b/src/wp-includes/php-ai-client/src/Providers/Http/Exception/ClientException.php
new file mode 100644
index 0000000000000..569e76e066a68
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Http/Exception/ClientException.php
@@ -0,0 +1,68 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Http\Exception;
+
+use WordPress\AiClient\Common\Exception\InvalidArgumentException;
+use WordPress\AiClient\Providers\Http\DTO\Request;
+use WordPress\AiClient\Providers\Http\DTO\Response;
+use WordPress\AiClient\Providers\Http\Util\ErrorMessageExtractor;
+/**
+ * Exception thrown for 4xx HTTP client errors.
+ *
+ * This represents errors where the client request was malformed,
+ * unauthorized, forbidden, or otherwise invalid.
+ *
+ * @since 0.2.0
+ */
+class ClientException extends InvalidArgumentException
+{
+    /**
+     * The request that failed.
+     *
+     * @var Request|null
+     */
+    protected ?Request $request = null;
+    /**
+     * Returns the request that failed as our Request DTO.
+     *
+     * @since 0.2.0
+     *
+     * @return Request
+     * @throws \RuntimeException If no request is available
+     */
+    public function getRequest(): Request
+    {
+        if ($this->request === null) {
+            throw new \RuntimeException('Request object not available. This exception was directly instantiated. ' . 'Use a factory method that provides request context.');
+        }
+        return $this->request;
+    }
+    /**
+     * Creates a ClientException from a client error response (4xx).
+     *
+     * This method extracts error details from common API response formats
+     * and creates an exception with a descriptive message and status code.
+     *
+     * @since 0.2.0
+     *
+     * @param Response $response The HTTP response that failed.
+     * @return self
+     */
+    public static function fromClientErrorResponse(Response $response): self
+    {
+        $statusCode = $response->getStatusCode();
+        $statusTexts = [400 => 'Bad Request', 401 => 'Unauthorized', 403 => 'Forbidden', 404 => 'Not Found', 422 => 'Unprocessable Entity', 429 => 'Too Many Requests'];
+        if (isset($statusTexts[$statusCode])) {
+            $errorMessage = sprintf('%s (%d)', $statusTexts[$statusCode], $statusCode);
+        } else {
+            $errorMessage = sprintf('Client error (%d): Request was rejected due to client-side issue', $statusCode);
+        }
+        // Extract error message from response data using centralized utility
+        $extractedError = ErrorMessageExtractor::extractFromResponseData($response->getData());
+        if ($extractedError !== null) {
+            $errorMessage .= ' - ' . $extractedError;
+        }
+        return new self($errorMessage, $statusCode);
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Http/Exception/NetworkException.php b/src/wp-includes/php-ai-client/src/Providers/Http/Exception/NetworkException.php
new file mode 100644
index 0000000000000..1b26ac2c60f0b
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Http/Exception/NetworkException.php
@@ -0,0 +1,57 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Http\Exception;
+
+use WordPress\AiClientDependencies\Psr\Http\Message\RequestInterface;
+use WordPress\AiClient\Common\Exception\RuntimeException;
+use WordPress\AiClient\Providers\Http\DTO\Request;
+/**
+ * Exception thrown for network-related errors.
+ *
+ * This includes HTTP transport errors, connection failures,
+ * timeouts, and other network-related issues.
+ *
+ * @since 0.2.0
+ */
+class NetworkException extends RuntimeException
+{
+    /**
+     * The request that failed.
+     *
+     * @var Request|null
+     */
+    protected ?Request $request = null;
+    /**
+     * Returns the request that failed as our Request DTO.
+     *
+     * @since 0.2.0
+     *
+     * @return Request
+     * @throws \RuntimeException If no request is available
+     */
+    public function getRequest(): Request
+    {
+        if ($this->request === null) {
+            throw new \RuntimeException('Request object not available. This exception was directly instantiated. ' . 'Use a factory method that provides request context.');
+        }
+        return $this->request;
+    }
+    /**
+     * Creates a NetworkException from a PSR-18 network exception.
+     *
+     * @since 0.2.0
+     *
+     * @param RequestInterface $psrRequest The PSR-7 request that failed.
+     * @param \Throwable $networkException The PSR-18 network exception.
+     * @return self
+     */
+    public static function fromPsr18NetworkException(RequestInterface $psrRequest, \Throwable $networkException): self
+    {
+        $request = Request::fromPsrRequest($psrRequest);
+        $message = sprintf('Network error occurred while sending request to %s: %s', $request->getUri(), $networkException->getMessage());
+        $exception = new self($message, 0, $networkException);
+        $exception->request = $request;
+        return $exception;
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Http/Exception/RedirectException.php b/src/wp-includes/php-ai-client/src/Providers/Http/Exception/RedirectException.php
new file mode 100644
index 0000000000000..0b21fe5219c25
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Http/Exception/RedirectException.php
@@ -0,0 +1,47 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Http\Exception;
+
+use WordPress\AiClient\Common\Exception\RuntimeException;
+use WordPress\AiClient\Providers\Http\DTO\Response;
+/**
+ * Exception thrown for 3xx HTTP redirect responses.
+ *
+ * This represents cases where the server indicates that the request
+ * should be retried at a different location, but automatic redirect
+ * handling was not successful or not enabled.
+ *
+ * @since 0.2.0
+ */
+class RedirectException extends RuntimeException
+{
+    /**
+     * Creates a RedirectException from a redirect response.
+     *
+     * This method extracts redirect information from the response headers
+     * and creates an exception with a descriptive message and status code.
+     *
+     * @since 0.2.0
+     *
+     * @param Response $response The HTTP redirect response.
+     * @return self
+     */
+    public static function fromRedirectResponse(Response $response): self
+    {
+        $statusCode = $response->getStatusCode();
+        $statusTexts = [300 => 'Multiple Choices', 301 => 'Moved Permanently', 302 => 'Found', 303 => 'See Other', 304 => 'Not Modified', 307 => 'Temporary Redirect', 308 => 'Permanent Redirect'];
+        if (isset($statusTexts[$statusCode])) {
+            $errorMessage = sprintf('%s (%d)', $statusTexts[$statusCode], $statusCode);
+        } else {
+            $errorMessage = sprintf('Redirect error (%d): Request needs to be retried at a different location', $statusCode);
+        }
+        // Try to extract the redirect location from headers
+        $locationValues = $response->getHeader('Location');
+        if ($locationValues !== null && !empty($locationValues)) {
+            $location = $locationValues[0];
+            $errorMessage .= ' - Location: ' . $location;
+        }
+        return new self($errorMessage, $statusCode);
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Http/Exception/ResponseException.php b/src/wp-includes/php-ai-client/src/Providers/Http/Exception/ResponseException.php
new file mode 100644
index 0000000000000..3e2dd07e43014
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Http/Exception/ResponseException.php
@@ -0,0 +1,46 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Http\Exception;
+
+use WordPress\AiClient\Common\Exception\RuntimeException;
+/**
+ * Exception class for HTTP response errors.
+ *
+ * This is used when response data is unexpected or malformed,
+ * typically indicating that a provider changed in ways our code
+ * is not aware of or when parsing response data fails.
+ *
+ * @since 0.1.0
+ */
+class ResponseException extends RuntimeException
+{
+    /**
+     * Creates a ResponseException for missing expected data.
+     *
+     * @since 0.2.0
+     *
+     * @param string $apiName The name of the API/provider.
+     * @param string $fieldName The field that was expected but missing.
+     * @return self
+     */
+    public static function fromMissingData(string $apiName, string $fieldName): self
+    {
+        $message = sprintf('Unexpected %s API response: Missing the "%s" key.', $apiName, $fieldName);
+        return new self($message);
+    }
+    /**
+     * Creates a ResponseException from invalid data in an API response.
+     *
+     * @since 0.2.0
+     *
+     * @param string $apiName The name of the API service (e.g., 'OpenAI', 'Anthropic').
+     * @param string $fieldName The field that was invalid.
+     * @param string $message The specific error message describing the invalid data.
+     * @return self
+     */
+    public static function fromInvalidData(string $apiName, string $fieldName, string $message): self
+    {
+        return new self(sprintf('Unexpected %s API response: Invalid "%s" key: %s', $apiName, $fieldName, $message));
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Http/Exception/ServerException.php b/src/wp-includes/php-ai-client/src/Providers/Http/Exception/ServerException.php
new file mode 100644
index 0000000000000..8963674137ccc
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Http/Exception/ServerException.php
@@ -0,0 +1,46 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Http\Exception;
+
+use WordPress\AiClient\Common\Exception\RuntimeException;
+use WordPress\AiClient\Providers\Http\DTO\Response;
+use WordPress\AiClient\Providers\Http\Util\ErrorMessageExtractor;
+/**
+ * Exception thrown for 5xx HTTP server errors.
+ *
+ * This represents errors where the server failed to fulfill
+ * a valid request due to internal server errors.
+ *
+ * @since 0.2.0
+ */
+class ServerException extends RuntimeException
+{
+    /**
+     * Creates a ServerException from a server error response.
+     *
+     * This method extracts error details from common API response formats
+     * and creates an exception with a descriptive message and status code.
+     *
+     * @since 0.2.0
+     *
+     * @param Response $response The HTTP response that failed.
+     * @return self
+     */
+    public static function fromServerErrorResponse(Response $response): self
+    {
+        $statusCode = $response->getStatusCode();
+        $statusTexts = [500 => 'Internal Server Error', 502 => 'Bad Gateway', 503 => 'Service Unavailable', 504 => 'Gateway Timeout', 507 => 'Insufficient Storage'];
+        if (isset($statusTexts[$statusCode])) {
+            $errorMessage = sprintf('%s (%d)', $statusTexts[$statusCode], $statusCode);
+        } else {
+            $errorMessage = sprintf('Server error (%d): Request was rejected due to server-side issue', $statusCode);
+        }
+        // Extract error message from response data using centralized utility
+        $extractedError = ErrorMessageExtractor::extractFromResponseData($response->getData());
+        if ($extractedError !== null) {
+            $errorMessage .= ' - ' . $extractedError;
+        }
+        return new self($errorMessage, $response->getStatusCode());
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Http/HttpTransporter.php b/src/wp-includes/php-ai-client/src/Providers/Http/HttpTransporter.php
new file mode 100644
index 0000000000000..dd6cc3e9e4c4b
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Http/HttpTransporter.php
@@ -0,0 +1,267 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Http;
+
+use WordPress\AiClientDependencies\Http\Discovery\Psr17FactoryDiscovery;
+use WordPress\AiClientDependencies\Http\Discovery\Psr18ClientDiscovery;
+use WordPress\AiClientDependencies\Psr\Http\Client\ClientInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\RequestFactoryInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\RequestInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\ResponseInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\StreamFactoryInterface;
+use WordPress\AiClient\Common\Exception\RuntimeException;
+use WordPress\AiClient\Providers\Http\Contracts\ClientWithOptionsInterface;
+use WordPress\AiClient\Providers\Http\Contracts\HttpTransporterInterface;
+use WordPress\AiClient\Providers\Http\DTO\Request;
+use WordPress\AiClient\Providers\Http\DTO\RequestOptions;
+use WordPress\AiClient\Providers\Http\DTO\Response;
+use WordPress\AiClient\Providers\Http\Exception\NetworkException;
+/**
+ * HTTP transporter implementation using HTTPlug.
+ *
+ * This class handles the conversion between custom Request/Response
+ * objects and PSR-7 messages, using HTTPlug for client abstraction
+ * and PSR-17 factories for message creation.
+ *
+ * @since 0.1.0
+ */
+class HttpTransporter implements HttpTransporterInterface
+{
+    /**
+     * @var RequestFactoryInterface PSR-17 request factory.
+     */
+    private RequestFactoryInterface $requestFactory;
+    /**
+     * @var StreamFactoryInterface PSR-17 stream factory.
+     */
+    private StreamFactoryInterface $streamFactory;
+    /**
+     * @var ClientInterface PSR-18 HTTP client.
+     */
+    private ClientInterface $client;
+    /**
+     * Constructor.
+     *
+     * @since 0.1.0
+     *
+     * @param ClientInterface|null $client PSR-18 HTTP client.
+     * @param RequestFactoryInterface|null $requestFactory PSR-17 request factory.
+     * @param StreamFactoryInterface|null $streamFactory PSR-17 stream factory.
+     */
+    public function __construct(?ClientInterface $client = null, ?RequestFactoryInterface $requestFactory = null, ?StreamFactoryInterface $streamFactory = null)
+    {
+        $this->client = $client ?: Psr18ClientDiscovery::find();
+        $this->requestFactory = $requestFactory ?: Psr17FactoryDiscovery::findRequestFactory();
+        $this->streamFactory = $streamFactory ?: Psr17FactoryDiscovery::findStreamFactory();
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     * @since 0.2.0 Added optional RequestOptions parameter and ClientWithOptions support.
+     */
+    public function send(Request $request, ?RequestOptions $options = null): Response
+    {
+        $psr7Request = $this->convertToPsr7Request($request);
+        // Merge request options with parameter options, with parameter options taking precedence
+        $mergedOptions = $this->mergeOptions($request->getOptions(), $options);
+        try {
+            $hasOptions = $mergedOptions !== null;
+            if ($hasOptions && $this->client instanceof ClientWithOptionsInterface) {
+                $psr7Response = $this->client->sendRequestWithOptions($psr7Request, $mergedOptions);
+            } elseif ($hasOptions && $this->isGuzzleClient($this->client)) {
+                $psr7Response = $this->sendWithGuzzle($psr7Request, $mergedOptions);
+            } else {
+                $psr7Response = $this->client->sendRequest($psr7Request);
+            }
+        } catch (\WordPress\AiClientDependencies\Psr\Http\Client\NetworkExceptionInterface $e) {
+            throw NetworkException::fromPsr18NetworkException($psr7Request, $e);
+        } catch (\WordPress\AiClientDependencies\Psr\Http\Client\ClientExceptionInterface $e) {
+            // Handle other PSR-18 client exceptions that are not network-related
+            throw new RuntimeException(sprintf('HTTP client error occurred while sending request to %s: %s', $request->getUri(), $e->getMessage()), 0, $e);
+        }
+        return $this->convertFromPsr7Response($psr7Response);
+    }
+    /**
+     * Merges request options with parameter options taking precedence.
+     *
+     * @since 0.2.0
+     *
+     * @param RequestOptions|null $requestOptions Options from the Request object.
+     * @param RequestOptions|null $parameterOptions Options passed as method parameter.
+     * @return RequestOptions|null Merged options, or null if both are null.
+     */
+    private function mergeOptions(?RequestOptions $requestOptions, ?RequestOptions $parameterOptions): ?RequestOptions
+    {
+        // If no options at all, return null
+        if ($requestOptions === null && $parameterOptions === null) {
+            return null;
+        }
+        // If only one set of options exists, return it
+        if ($requestOptions === null) {
+            return $parameterOptions;
+        }
+        if ($parameterOptions === null) {
+            return $requestOptions;
+        }
+        // Both exist, merge them with parameter options taking precedence
+        $merged = new RequestOptions();
+        // Start with request options (lower precedence)
+        if ($requestOptions->getTimeout() !== null) {
+            $merged->setTimeout($requestOptions->getTimeout());
+        }
+        if ($requestOptions->getConnectTimeout() !== null) {
+            $merged->setConnectTimeout($requestOptions->getConnectTimeout());
+        }
+        if ($requestOptions->getMaxRedirects() !== null) {
+            $merged->setMaxRedirects($requestOptions->getMaxRedirects());
+        }
+        // Override with parameter options (higher precedence)
+        if ($parameterOptions->getTimeout() !== null) {
+            $merged->setTimeout($parameterOptions->getTimeout());
+        }
+        if ($parameterOptions->getConnectTimeout() !== null) {
+            $merged->setConnectTimeout($parameterOptions->getConnectTimeout());
+        }
+        if ($parameterOptions->getMaxRedirects() !== null) {
+            $merged->setMaxRedirects($parameterOptions->getMaxRedirects());
+        }
+        return $merged;
+    }
+    /**
+     * Determines if the underlying client matches the Guzzle client shape.
+     *
+     * @since 0.2.0
+     *
+     * @param ClientInterface $client The HTTP client instance.
+     * @return bool True when the client exposes Guzzle's send signature.
+     */
+    private function isGuzzleClient(ClientInterface $client): bool
+    {
+        $reflection = new \ReflectionObject($client);
+        if (!is_callable([$client, 'send'])) {
+            return \false;
+        }
+        if (!$reflection->hasMethod('send')) {
+            return \false;
+        }
+        $method = $reflection->getMethod('send');
+        if (!$method->isPublic() || $method->isStatic()) {
+            return \false;
+        }
+        $parameters = $method->getParameters();
+        if (count($parameters) < 2) {
+            return \false;
+        }
+        $firstParameter = $parameters[0]->getType();
+        if (!$firstParameter instanceof \ReflectionNamedType || $firstParameter->isBuiltin()) {
+            return \false;
+        }
+        if (!is_a($firstParameter->getName(), RequestInterface::class, \true)) {
+            return \false;
+        }
+        $secondParameter = $parameters[1];
+        $secondType = $secondParameter->getType();
+        if (!$secondType instanceof \ReflectionNamedType || $secondType->getName() !== 'array') {
+            return \false;
+        }
+        return \true;
+    }
+    /**
+     * Sends a request using a Guzzle-compatible client.
+     *
+     * @since 0.2.0
+     *
+     * @param RequestInterface $request The PSR-7 request to send.
+     * @param RequestOptions $options The request options.
+     * @return ResponseInterface The PSR-7 response received.
+     */
+    private function sendWithGuzzle(RequestInterface $request, RequestOptions $options): ResponseInterface
+    {
+        $guzzleOptions = $this->buildGuzzleOptions($options);
+        /** @var callable $callable */
+        $callable = [$this->client, 'send'];
+        /** @var ResponseInterface $response */
+        $response = $callable($request, $guzzleOptions);
+        return $response;
+    }
+    /**
+     * Converts request options to a Guzzle-compatible options array.
+     *
+     * @since 0.2.0
+     *
+     * @param RequestOptions $options The request options.
+     * @return array<string, mixed> Guzzle-compatible options.
+     */
+    private function buildGuzzleOptions(RequestOptions $options): array
+    {
+        $guzzleOptions = [];
+        $timeout = $options->getTimeout();
+        if ($timeout !== null) {
+            $guzzleOptions['timeout'] = $timeout;
+        }
+        $connectTimeout = $options->getConnectTimeout();
+        if ($connectTimeout !== null) {
+            $guzzleOptions['connect_timeout'] = $connectTimeout;
+        }
+        $allowRedirects = $options->allowsRedirects();
+        if ($allowRedirects !== null) {
+            if ($allowRedirects) {
+                $redirectOptions = [];
+                $maxRedirects = $options->getMaxRedirects();
+                if ($maxRedirects !== null) {
+                    $redirectOptions['max'] = $maxRedirects;
+                }
+                $guzzleOptions['allow_redirects'] = !empty($redirectOptions) ? $redirectOptions : \true;
+            } else {
+                $guzzleOptions['allow_redirects'] = \false;
+            }
+        }
+        return $guzzleOptions;
+    }
+    /**
+     * Converts a custom Request to a PSR-7 request.
+     *
+     * @since 0.1.0
+     *
+     * @param Request $request The custom request.
+     * @return RequestInterface The PSR-7 request.
+     */
+    private function convertToPsr7Request(Request $request): RequestInterface
+    {
+        $psr7Request = $this->requestFactory->createRequest($request->getMethod()->value, $request->getUri());
+        // Add headers
+        foreach ($request->getHeaders() as $name => $values) {
+            foreach ($values as $value) {
+                $psr7Request = $psr7Request->withAddedHeader($name, $value);
+            }
+        }
+        // Add body if present
+        $body = $request->getBody();
+        if ($body !== null) {
+            $stream = $this->streamFactory->createStream($body);
+            $psr7Request = $psr7Request->withBody($stream);
+        }
+        return $psr7Request;
+    }
+    /**
+     * Converts a PSR-7 response to a custom Response.
+     *
+     * @since 0.1.0
+     *
+     * @param ResponseInterface $psr7Response The PSR-7 response.
+     * @return Response The custom response.
+     */
+    private function convertFromPsr7Response(ResponseInterface $psr7Response): Response
+    {
+        $body = (string) $psr7Response->getBody();
+        // PSR-7 always returns headers as arrays, but HeadersCollection handles this
+        return new Response(
+            $psr7Response->getStatusCode(),
+            $psr7Response->getHeaders(),
+            // @phpstan-ignore-line
+            $body === '' ? null : $body
+        );
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Http/HttpTransporterFactory.php b/src/wp-includes/php-ai-client/src/Providers/Http/HttpTransporterFactory.php
new file mode 100644
index 0000000000000..f2927f7e4e611
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Http/HttpTransporterFactory.php
@@ -0,0 +1,33 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Http;
+
+use WordPress\AiClientDependencies\Http\Discovery\Psr17FactoryDiscovery;
+use WordPress\AiClientDependencies\Http\Discovery\Psr18ClientDiscovery;
+use WordPress\AiClient\Providers\Http\Contracts\HttpTransporterInterface;
+/**
+ * Factory for creating HTTP transporters.
+ *
+ * Uses HTTPlug's Discovery component to automatically find
+ * available HTTP clients and factories.
+ *
+ * @since 0.1.0
+ */
+class HttpTransporterFactory
+{
+    /**
+     * Creates an HTTP transporter.
+     *
+     * Uses HTTPlug Discovery to automatically find PSR-18 client
+     * and PSR-17 factories if not provided.
+     *
+     * @since 0.1.0
+     *
+     * @return HttpTransporterInterface The HTTP transporter.
+     */
+    public static function createTransporter(): HttpTransporterInterface
+    {
+        return new \WordPress\AiClient\Providers\Http\HttpTransporter(Psr18ClientDiscovery::find(), Psr17FactoryDiscovery::findRequestFactory(), Psr17FactoryDiscovery::findStreamFactory());
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Http/Traits/WithHttpTransporterTrait.php b/src/wp-includes/php-ai-client/src/Providers/Http/Traits/WithHttpTransporterTrait.php
new file mode 100644
index 0000000000000..7fd9d1beadf51
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Http/Traits/WithHttpTransporterTrait.php
@@ -0,0 +1,40 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Http\Traits;
+
+use WordPress\AiClient\Common\Exception\RuntimeException;
+use WordPress\AiClient\Providers\Http\Contracts\HttpTransporterInterface;
+/**
+ * Trait for a class that implements WithHttpTransporterInterface.
+ *
+ * @since 0.1.0
+ */
+trait WithHttpTransporterTrait
+{
+    /**
+     * @var HttpTransporterInterface|null The HTTP transporter instance.
+     */
+    private ?HttpTransporterInterface $httpTransporter = null;
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public function setHttpTransporter(HttpTransporterInterface $httpTransporter): void
+    {
+        $this->httpTransporter = $httpTransporter;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public function getHttpTransporter(): HttpTransporterInterface
+    {
+        if ($this->httpTransporter === null) {
+            throw new RuntimeException('HttpTransporterInterface instance not set. Make sure you use the AiClient class for all requests.');
+        }
+        return $this->httpTransporter;
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Http/Traits/WithRequestAuthenticationTrait.php b/src/wp-includes/php-ai-client/src/Providers/Http/Traits/WithRequestAuthenticationTrait.php
new file mode 100644
index 0000000000000..12c13541709ea
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Http/Traits/WithRequestAuthenticationTrait.php
@@ -0,0 +1,40 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Http\Traits;
+
+use WordPress\AiClient\Common\Exception\RuntimeException;
+use WordPress\AiClient\Providers\Http\Contracts\RequestAuthenticationInterface;
+/**
+ * Trait for a class that implements WithRequestAuthenticationInterface.
+ *
+ * @since 0.1.0
+ */
+trait WithRequestAuthenticationTrait
+{
+    /**
+     * @var RequestAuthenticationInterface|null The request authentication instance.
+     */
+    private ?RequestAuthenticationInterface $requestAuthentication = null;
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public function setRequestAuthentication(RequestAuthenticationInterface $requestAuthentication): void
+    {
+        $this->requestAuthentication = $requestAuthentication;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public function getRequestAuthentication(): RequestAuthenticationInterface
+    {
+        if ($this->requestAuthentication === null) {
+            throw new RuntimeException('RequestAuthenticationInterface instance not set. ' . 'Make sure you use the AiClient class for all requests.');
+        }
+        return $this->requestAuthentication;
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Http/Util/ErrorMessageExtractor.php b/src/wp-includes/php-ai-client/src/Providers/Http/Util/ErrorMessageExtractor.php
new file mode 100644
index 0000000000000..8b71f5be77be4
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Http/Util/ErrorMessageExtractor.php
@@ -0,0 +1,53 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Http\Util;
+
+/**
+ * Utility for extracting error messages from API response data.
+ *
+ * Centralizes the logic for parsing common API error response formats
+ * to avoid code duplication across exception classes.
+ *
+ * @since 0.2.0
+ * @since 0.4.0 Moved from Utilities namespace to Util namespace.
+ */
+class ErrorMessageExtractor
+{
+    /**
+     * Extracts error message from API response data.
+     *
+     * Handles common error response formats:
+     * - { "error": { "message": "Error text" } }
+     * - { "error": "Error text" }
+     * - { "message": "Error text" }
+     *
+     * @since 0.2.0
+     *
+     * @param mixed $data The response data to extract error message from.
+     * @return string|null The extracted error message, or null if none found.
+     */
+    public static function extractFromResponseData($data): ?string
+    {
+        if (!is_array($data)) {
+            return null;
+        }
+        // Handle [ { "error": { "message": "Error text" } } ]
+        if (isset($data[0]) && is_array($data[0]) && isset($data[0]['error']) && is_array($data[0]['error']) && isset($data[0]['error']['message']) && is_string($data[0]['error']['message'])) {
+            return $data[0]['error']['message'];
+        }
+        // Handle { "error": { "message": "Error text" } }
+        if (isset($data['error']) && is_array($data['error']) && isset($data['error']['message']) && is_string($data['error']['message'])) {
+            return $data['error']['message'];
+        }
+        // Handle { "error": "Error text" }
+        if (isset($data['error']) && is_string($data['error'])) {
+            return $data['error'];
+        }
+        // Handle { "message": "Error text" }
+        if (isset($data['message']) && is_string($data['message'])) {
+            return $data['message'];
+        }
+        return null;
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Http/Util/ResponseUtil.php b/src/wp-includes/php-ai-client/src/Providers/Http/Util/ResponseUtil.php
new file mode 100644
index 0000000000000..44512a0f89a7a
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Http/Util/ResponseUtil.php
@@ -0,0 +1,55 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Http\Util;
+
+use WordPress\AiClient\Providers\Http\DTO\Response;
+use WordPress\AiClient\Providers\Http\Exception\ClientException;
+use WordPress\AiClient\Providers\Http\Exception\RedirectException;
+use WordPress\AiClient\Providers\Http\Exception\ServerException;
+/**
+ * Class with static utility methods to process HTTP responses.
+ *
+ * @since 0.1.0
+ */
+class ResponseUtil
+{
+    /**
+     * Throws an appropriate exception if the given response is not successful.
+     *
+     * This method checks the HTTP status code of the response and throws
+     * the appropriate exception type based on the status code range:
+     * - 3xx: RedirectException (redirect responses)
+     * - 4xx: ClientException (client errors)
+     * - 5xx: ServerException (server errors)
+     * - Other unsuccessful responses: RuntimeException (invalid status codes)
+     *
+     * @since 0.1.0
+     *
+     * @param Response $response The HTTP response to check.
+     * @throws RedirectException If the response indicates a redirect (3xx).
+     * @throws ClientException If the response indicates a client error (4xx).
+     * @throws ServerException If the response indicates a server error (5xx).
+     * @throws \RuntimeException If the response has an invalid status code.
+     */
+    public static function throwIfNotSuccessful(Response $response): void
+    {
+        if ($response->isSuccessful()) {
+            return;
+        }
+        $statusCode = $response->getStatusCode();
+        // 3xx Redirect Responses
+        if ($statusCode >= 300 && $statusCode < 400) {
+            throw RedirectException::fromRedirectResponse($response);
+        }
+        // 4xx Client Errors
+        if ($statusCode >= 400 && $statusCode < 500) {
+            throw ClientException::fromClientErrorResponse($response);
+        }
+        // 5xx Server Errors
+        if ($statusCode >= 500 && $statusCode < 600) {
+            throw ServerException::fromServerErrorResponse($response);
+        }
+        throw new \RuntimeException(sprintf('Response returned invalid status code: %s', $response->getStatusCode()));
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Models/Contracts/ModelInterface.php b/src/wp-includes/php-ai-client/src/Providers/Models/Contracts/ModelInterface.php
new file mode 100644
index 0000000000000..45abe5ab51fa7
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Models/Contracts/ModelInterface.php
@@ -0,0 +1,52 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Models\Contracts;
+
+use WordPress\AiClient\Providers\DTO\ProviderMetadata;
+use WordPress\AiClient\Providers\Models\DTO\ModelConfig;
+use WordPress\AiClient\Providers\Models\DTO\ModelMetadata;
+/**
+ * Interface for AI models.
+ *
+ * Models represent specific AI models from providers and define
+ * their capabilities, configuration, and execution methods.
+ *
+ * @since 0.1.0
+ */
+interface ModelInterface
+{
+    /**
+     * Gets model metadata.
+     *
+     * @since 0.1.0
+     *
+     * @return ModelMetadata Model metadata.
+     */
+    public function metadata(): ModelMetadata;
+    /**
+     * Returns the metadata for the model's provider.
+     *
+     * @since 0.1.0
+     *
+     * @return ProviderMetadata The provider metadata.
+     */
+    public function providerMetadata(): ProviderMetadata;
+    /**
+     * Sets model configuration.
+     *
+     * @since 0.1.0
+     *
+     * @param ModelConfig $config Model configuration.
+     * @return void
+     */
+    public function setConfig(ModelConfig $config): void;
+    /**
+     * Gets model configuration.
+     *
+     * @since 0.1.0
+     *
+     * @return ModelConfig Current model configuration.
+     */
+    public function getConfig(): ModelConfig;
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Models/DTO/ModelConfig.php b/src/wp-includes/php-ai-client/src/Providers/Models/DTO/ModelConfig.php
new file mode 100644
index 0000000000000..f5706cc774001
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Models/DTO/ModelConfig.php
@@ -0,0 +1,855 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Models\DTO;
+
+use WordPress\AiClient\Common\AbstractDataTransferObject;
+use WordPress\AiClient\Common\Exception\InvalidArgumentException;
+use WordPress\AiClient\Files\Enums\FileTypeEnum;
+use WordPress\AiClient\Files\Enums\MediaOrientationEnum;
+use WordPress\AiClient\Messages\Enums\ModalityEnum;
+use WordPress\AiClient\Tools\DTO\FunctionDeclaration;
+use WordPress\AiClient\Tools\DTO\WebSearch;
+/**
+ * Represents configuration for an AI model.
+ *
+ * This class allows configuring various parameters for model behavior,
+ * including output modalities, system instructions, generation parameters,
+ * and tool integrations.
+ *
+ * @since 0.1.0
+ *
+ * @phpstan-import-type FunctionDeclarationArrayShape from FunctionDeclaration
+ * @phpstan-import-type WebSearchArrayShape from WebSearch
+ *
+ * @phpstan-type ModelConfigArrayShape array{
+ *     outputModalities?: list<string>,
+ *     systemInstruction?: string,
+ *     candidateCount?: int,
+ *     maxTokens?: int,
+ *     temperature?: float,
+ *     topP?: float,
+ *     topK?: int,
+ *     stopSequences?: list<string>,
+ *     presencePenalty?: float,
+ *     frequencyPenalty?: float,
+ *     logprobs?: bool,
+ *     topLogprobs?: int,
+ *     functionDeclarations?: list<FunctionDeclarationArrayShape>,
+ *     webSearch?: WebSearchArrayShape,
+ *     outputFileType?: string,
+ *     outputMimeType?: string,
+ *     outputSchema?: array<string, mixed>,
+ *     outputMediaOrientation?: string,
+ *     outputMediaAspectRatio?: string,
+ *     outputSpeechVoice?: string,
+ *     customOptions?: array<string, mixed>
+ * }
+ *
+ * @extends AbstractDataTransferObject<ModelConfigArrayShape>
+ */
+class ModelConfig extends AbstractDataTransferObject
+{
+    public const KEY_OUTPUT_MODALITIES = 'outputModalities';
+    public const KEY_SYSTEM_INSTRUCTION = 'systemInstruction';
+    public const KEY_CANDIDATE_COUNT = 'candidateCount';
+    public const KEY_MAX_TOKENS = 'maxTokens';
+    public const KEY_TEMPERATURE = 'temperature';
+    public const KEY_TOP_P = 'topP';
+    public const KEY_TOP_K = 'topK';
+    public const KEY_STOP_SEQUENCES = 'stopSequences';
+    public const KEY_PRESENCE_PENALTY = 'presencePenalty';
+    public const KEY_FREQUENCY_PENALTY = 'frequencyPenalty';
+    public const KEY_LOGPROBS = 'logprobs';
+    public const KEY_TOP_LOGPROBS = 'topLogprobs';
+    public const KEY_FUNCTION_DECLARATIONS = 'functionDeclarations';
+    public const KEY_WEB_SEARCH = 'webSearch';
+    public const KEY_OUTPUT_FILE_TYPE = 'outputFileType';
+    public const KEY_OUTPUT_MIME_TYPE = 'outputMimeType';
+    public const KEY_OUTPUT_SCHEMA = 'outputSchema';
+    public const KEY_OUTPUT_MEDIA_ORIENTATION = 'outputMediaOrientation';
+    public const KEY_OUTPUT_MEDIA_ASPECT_RATIO = 'outputMediaAspectRatio';
+    public const KEY_OUTPUT_SPEECH_VOICE = 'outputSpeechVoice';
+    public const KEY_CUSTOM_OPTIONS = 'customOptions';
+    /*
+     * Note: This key is not an actual model config key, but specified here for convenience.
+     * It is relevant for model discovery, to determine which models support which input modalities.
+     * The actual input modalities are part of the message sent to the model, not the model config.
+     */
+    public const KEY_INPUT_MODALITIES = 'inputModalities';
+    /**
+     * @var list<ModalityEnum>|null Output modalities for the model.
+     */
+    protected ?array $outputModalities = null;
+    /**
+     * @var string|null System instruction for the model.
+     */
+    protected ?string $systemInstruction = null;
+    /**
+     * @var int|null Number of response candidates to generate.
+     */
+    protected ?int $candidateCount = null;
+    /**
+     * @var int|null Maximum number of tokens to generate.
+     */
+    protected ?int $maxTokens = null;
+    /**
+     * @var float|null Temperature for randomness (0.0 to 2.0).
+     */
+    protected ?float $temperature = null;
+    /**
+     * @var float|null Top-p nucleus sampling parameter.
+     */
+    protected ?float $topP = null;
+    /**
+     * @var int|null Top-k sampling parameter.
+     */
+    protected ?int $topK = null;
+    /**
+     * @var list<string>|null Stop sequences.
+     */
+    protected ?array $stopSequences = null;
+    /**
+     * @var float|null Presence penalty for reducing repetition.
+     */
+    protected ?float $presencePenalty = null;
+    /**
+     * @var float|null Frequency penalty for reducing repetition.
+     */
+    protected ?float $frequencyPenalty = null;
+    /**
+     * @var bool|null Whether to return log probabilities.
+     */
+    protected ?bool $logprobs = null;
+    /**
+     * @var int|null Number of top log probabilities to return.
+     */
+    protected ?int $topLogprobs = null;
+    /**
+     * @var list<FunctionDeclaration>|null Function declarations available to the model.
+     */
+    protected ?array $functionDeclarations = null;
+    /**
+     * @var WebSearch|null Web search configuration for the model.
+     */
+    protected ?WebSearch $webSearch = null;
+    /**
+     * @var FileTypeEnum|null Output file type.
+     */
+    protected ?FileTypeEnum $outputFileType = null;
+    /**
+     * @var string|null Output MIME type.
+     */
+    protected ?string $outputMimeType = null;
+    /**
+     * @var array<string, mixed>|null Output schema (JSON schema).
+     */
+    protected ?array $outputSchema = null;
+    /**
+     * @var MediaOrientationEnum|null Output media orientation.
+     */
+    protected ?MediaOrientationEnum $outputMediaOrientation = null;
+    /**
+     * @var string|null Output media aspect ratio (e.g. 3:2, 16:9).
+     */
+    protected ?string $outputMediaAspectRatio = null;
+    /**
+     * @var string|null Output speech voice.
+     */
+    protected ?string $outputSpeechVoice = null;
+    /**
+     * @var array<string, mixed> Custom provider-specific options.
+     */
+    protected array $customOptions = [];
+    /**
+     * Sets the output modalities.
+     *
+     * @since 0.1.0
+     *
+     * @param list<ModalityEnum> $outputModalities The output modalities.
+     *
+     * @throws InvalidArgumentException If the array is not a list.
+     */
+    public function setOutputModalities(array $outputModalities): void
+    {
+        if (!array_is_list($outputModalities)) {
+            throw new InvalidArgumentException('Output modalities must be a list array.');
+        }
+        $this->outputModalities = $outputModalities;
+    }
+    /**
+     * Gets the output modalities.
+     *
+     * @since 0.1.0
+     *
+     * @return list<ModalityEnum>|null The output modalities.
+     */
+    public function getOutputModalities(): ?array
+    {
+        return $this->outputModalities;
+    }
+    /**
+     * Sets the system instruction.
+     *
+     * @since 0.1.0
+     *
+     * @param string $systemInstruction The system instruction.
+     */
+    public function setSystemInstruction(string $systemInstruction): void
+    {
+        $this->systemInstruction = $systemInstruction;
+    }
+    /**
+     * Gets the system instruction.
+     *
+     * @since 0.1.0
+     *
+     * @return string|null The system instruction.
+     */
+    public function getSystemInstruction(): ?string
+    {
+        return $this->systemInstruction;
+    }
+    /**
+     * Sets the candidate count.
+     *
+     * @since 0.1.0
+     *
+     * @param int $candidateCount The candidate count.
+     */
+    public function setCandidateCount(int $candidateCount): void
+    {
+        $this->candidateCount = $candidateCount;
+    }
+    /**
+     * Gets the candidate count.
+     *
+     * @since 0.1.0
+     *
+     * @return int|null The candidate count.
+     */
+    public function getCandidateCount(): ?int
+    {
+        return $this->candidateCount;
+    }
+    /**
+     * Sets the maximum tokens.
+     *
+     * @since 0.1.0
+     *
+     * @param int $maxTokens The maximum tokens.
+     */
+    public function setMaxTokens(int $maxTokens): void
+    {
+        $this->maxTokens = $maxTokens;
+    }
+    /**
+     * Gets the maximum tokens.
+     *
+     * @since 0.1.0
+     *
+     * @return int|null The maximum tokens.
+     */
+    public function getMaxTokens(): ?int
+    {
+        return $this->maxTokens;
+    }
+    /**
+     * Sets the temperature.
+     *
+     * @since 0.1.0
+     *
+     * @param float $temperature The temperature.
+     */
+    public function setTemperature(float $temperature): void
+    {
+        $this->temperature = $temperature;
+    }
+    /**
+     * Gets the temperature.
+     *
+     * @since 0.1.0
+     *
+     * @return float|null The temperature.
+     */
+    public function getTemperature(): ?float
+    {
+        return $this->temperature;
+    }
+    /**
+     * Sets the top-p parameter.
+     *
+     * @since 0.1.0
+     *
+     * @param float $topP The top-p parameter.
+     */
+    public function setTopP(float $topP): void
+    {
+        $this->topP = $topP;
+    }
+    /**
+     * Gets the top-p parameter.
+     *
+     * @since 0.1.0
+     *
+     * @return float|null The top-p parameter.
+     */
+    public function getTopP(): ?float
+    {
+        return $this->topP;
+    }
+    /**
+     * Sets the top-k parameter.
+     *
+     * @since 0.1.0
+     *
+     * @param int $topK The top-k parameter.
+     */
+    public function setTopK(int $topK): void
+    {
+        $this->topK = $topK;
+    }
+    /**
+     * Gets the top-k parameter.
+     *
+     * @since 0.1.0
+     *
+     * @return int|null The top-k parameter.
+     */
+    public function getTopK(): ?int
+    {
+        return $this->topK;
+    }
+    /**
+     * Sets the stop sequences.
+     *
+     * @since 0.1.0
+     *
+     * @param list<string> $stopSequences The stop sequences.
+     *
+     * @throws InvalidArgumentException If the array is not a list.
+     */
+    public function setStopSequences(array $stopSequences): void
+    {
+        if (!array_is_list($stopSequences)) {
+            throw new InvalidArgumentException('Stop sequences must be a list array.');
+        }
+        $this->stopSequences = $stopSequences;
+    }
+    /**
+     * Gets the stop sequences.
+     *
+     * @since 0.1.0
+     *
+     * @return list<string>|null The stop sequences.
+     */
+    public function getStopSequences(): ?array
+    {
+        return $this->stopSequences;
+    }
+    /**
+     * Sets the presence penalty.
+     *
+     * @since 0.1.0
+     *
+     * @param float $presencePenalty The presence penalty.
+     */
+    public function setPresencePenalty(float $presencePenalty): void
+    {
+        $this->presencePenalty = $presencePenalty;
+    }
+    /**
+     * Gets the presence penalty.
+     *
+     * @since 0.1.0
+     *
+     * @return float|null The presence penalty.
+     */
+    public function getPresencePenalty(): ?float
+    {
+        return $this->presencePenalty;
+    }
+    /**
+     * Sets the frequency penalty.
+     *
+     * @since 0.1.0
+     *
+     * @param float $frequencyPenalty The frequency penalty.
+     */
+    public function setFrequencyPenalty(float $frequencyPenalty): void
+    {
+        $this->frequencyPenalty = $frequencyPenalty;
+    }
+    /**
+     * Gets the frequency penalty.
+     *
+     * @since 0.1.0
+     *
+     * @return float|null The frequency penalty.
+     */
+    public function getFrequencyPenalty(): ?float
+    {
+        return $this->frequencyPenalty;
+    }
+    /**
+     * Sets whether to return log probabilities.
+     *
+     * @since 0.1.0
+     *
+     * @param bool $logprobs Whether to return log probabilities.
+     */
+    public function setLogprobs(bool $logprobs): void
+    {
+        $this->logprobs = $logprobs;
+    }
+    /**
+     * Gets whether to return log probabilities.
+     *
+     * @since 0.1.0
+     *
+     * @return bool|null Whether to return log probabilities.
+     */
+    public function getLogprobs(): ?bool
+    {
+        return $this->logprobs;
+    }
+    /**
+     * Sets the number of top log probabilities to return.
+     *
+     * @since 0.1.0
+     *
+     * @param int $topLogprobs The number of top log probabilities.
+     */
+    public function setTopLogprobs(int $topLogprobs): void
+    {
+        $this->topLogprobs = $topLogprobs;
+    }
+    /**
+     * Gets the number of top log probabilities to return.
+     *
+     * @since 0.1.0
+     *
+     * @return int|null The number of top log probabilities.
+     */
+    public function getTopLogprobs(): ?int
+    {
+        return $this->topLogprobs;
+    }
+    /**
+     * Sets the function declarations.
+     *
+     * @since 0.1.0
+     *
+     * @param list<FunctionDeclaration> $function_declarations The function declarations.
+     *
+     * @throws InvalidArgumentException If the array is not a list.
+     */
+    public function setFunctionDeclarations(array $function_declarations): void
+    {
+        if (!array_is_list($function_declarations)) {
+            throw new InvalidArgumentException('Function declarations must be a list array.');
+        }
+        $this->functionDeclarations = $function_declarations;
+    }
+    /**
+     * Gets the function declarations.
+     *
+     * @since 0.1.0
+     *
+     * @return list<FunctionDeclaration>|null The function declarations.
+     */
+    public function getFunctionDeclarations(): ?array
+    {
+        return $this->functionDeclarations;
+    }
+    /**
+     * Sets the web search configuration.
+     *
+     * @since 0.1.0
+     *
+     * @param WebSearch $web_search The web search configuration.
+     */
+    public function setWebSearch(WebSearch $web_search): void
+    {
+        $this->webSearch = $web_search;
+    }
+    /**
+     * Gets the web search configuration.
+     *
+     * @since 0.1.0
+     *
+     * @return WebSearch|null The web search configuration.
+     */
+    public function getWebSearch(): ?WebSearch
+    {
+        return $this->webSearch;
+    }
+    /**
+     * Sets the output file type.
+     *
+     * @since 0.1.0
+     *
+     * @param FileTypeEnum $outputFileType The output file type.
+     */
+    public function setOutputFileType(FileTypeEnum $outputFileType): void
+    {
+        $this->outputFileType = $outputFileType;
+    }
+    /**
+     * Gets the output file type.
+     *
+     * @since 0.1.0
+     *
+     * @return FileTypeEnum|null The output file type.
+     */
+    public function getOutputFileType(): ?FileTypeEnum
+    {
+        return $this->outputFileType;
+    }
+    /**
+     * Sets the output MIME type.
+     *
+     * @since 0.1.0
+     *
+     * @param string $outputMimeType The output MIME type.
+     */
+    public function setOutputMimeType(string $outputMimeType): void
+    {
+        $this->outputMimeType = $outputMimeType;
+    }
+    /**
+     * Gets the output MIME type.
+     *
+     * @since 0.1.0
+     *
+     * @return string|null The output MIME type.
+     */
+    public function getOutputMimeType(): ?string
+    {
+        return $this->outputMimeType;
+    }
+    /**
+     * Sets the output schema.
+     *
+     * When setting an output schema, this method automatically sets
+     * the output MIME type to "application/json" if not already set.
+     *
+     * @since 0.1.0
+     *
+     * @param array<string, mixed> $outputSchema The output schema (JSON schema).
+     */
+    public function setOutputSchema(array $outputSchema): void
+    {
+        $this->outputSchema = $outputSchema;
+        // Automatically set outputMimeType to application/json when schema is provided
+        if ($this->outputMimeType === null) {
+            $this->outputMimeType = 'application/json';
+        }
+    }
+    /**
+     * Gets the output schema.
+     *
+     * @since 0.1.0
+     *
+     * @return array<string, mixed>|null The output schema.
+     */
+    public function getOutputSchema(): ?array
+    {
+        return $this->outputSchema;
+    }
+    /**
+     * Sets the output media orientation.
+     *
+     * @since 0.1.0
+     *
+     * @param MediaOrientationEnum $outputMediaOrientation The output media orientation.
+     */
+    public function setOutputMediaOrientation(MediaOrientationEnum $outputMediaOrientation): void
+    {
+        if ($this->outputMediaAspectRatio) {
+            $this->validateMediaOrientationAspectRatioCompatibility($outputMediaOrientation, $this->outputMediaAspectRatio);
+        }
+        $this->outputMediaOrientation = $outputMediaOrientation;
+    }
+    /**
+     * Gets the output media orientation.
+     *
+     * @since 0.1.0
+     *
+     * @return MediaOrientationEnum|null The output media orientation.
+     */
+    public function getOutputMediaOrientation(): ?MediaOrientationEnum
+    {
+        return $this->outputMediaOrientation;
+    }
+    /**
+     * Sets the output media aspect ratio.
+     *
+     * If set, this supersedes the output media orientation, as it is a more specific configuration.
+     *
+     * @since 0.1.0
+     *
+     * @param string $outputMediaAspectRatio The output media aspect ratio (e.g. 3:2, 16:9).
+     */
+    public function setOutputMediaAspectRatio(string $outputMediaAspectRatio): void
+    {
+        if (!preg_match('/^\d+:\d+$/', $outputMediaAspectRatio)) {
+            throw new InvalidArgumentException('Output media aspect ratio must be in the format "width:height" (e.g. 3:2, 16:9).');
+        }
+        if ($this->outputMediaOrientation) {
+            $this->validateMediaOrientationAspectRatioCompatibility($this->outputMediaOrientation, $outputMediaAspectRatio);
+        }
+        $this->outputMediaAspectRatio = $outputMediaAspectRatio;
+    }
+    /**
+     * Gets the output media aspect ratio.
+     *
+     * @since 0.1.0
+     *
+     * @return string|null The output media aspect ratio (e.g. 3:2, 16:9).
+     */
+    public function getOutputMediaAspectRatio(): ?string
+    {
+        return $this->outputMediaAspectRatio;
+    }
+    /**
+     * Validates that the given media orientation and aspect ratio values do not conflict with each other.
+     *
+     * @since 0.4.0
+     *
+     * @param MediaOrientationEnum $orientation The desired media orientation.
+     * @param string $aspectRatio The desired media aspect ratio.
+     */
+    protected function validateMediaOrientationAspectRatioCompatibility(MediaOrientationEnum $orientation, string $aspectRatio): void
+    {
+        if ($orientation->isSquare() && $aspectRatio !== '1:1') {
+            throw new InvalidArgumentException('The aspect ratio "' . $aspectRatio . '" is not compatible with the square orientation.');
+        }
+        $aspectRatioParts = explode(':', $aspectRatio);
+        if ($orientation->isLandscape() && $aspectRatioParts[0] <= $aspectRatioParts[1]) {
+            throw new InvalidArgumentException('The aspect ratio "' . $aspectRatio . '" is not compatible with the landscape orientation.');
+        }
+        if ($orientation->isPortrait() && $aspectRatioParts[0] >= $aspectRatioParts[1]) {
+            throw new InvalidArgumentException('The aspect ratio "' . $aspectRatio . '" is not compatible with the portrait orientation.');
+        }
+    }
+    /**
+     * Sets the output speech voice.
+     *
+     * @since 0.1.0
+     *
+     * @param string $outputSpeechVoice The output speech voice.
+     */
+    public function setOutputSpeechVoice(string $outputSpeechVoice): void
+    {
+        $this->outputSpeechVoice = $outputSpeechVoice;
+    }
+    /**
+     * Gets the output speech voice.
+     *
+     * @since 0.1.0
+     *
+     * @return string|null The output speech voice.
+     */
+    public function getOutputSpeechVoice(): ?string
+    {
+        return $this->outputSpeechVoice;
+    }
+    /**
+     * Sets a single custom option.
+     *
+     * @since 0.1.0
+     *
+     * @param string $key   The option key.
+     * @param mixed  $value The option value.
+     */
+    public function setCustomOption(string $key, $value): void
+    {
+        $this->customOptions[$key] = $value;
+    }
+    /**
+     * Sets the custom options.
+     *
+     * @since 0.1.0
+     *
+     * @param array<string, mixed> $customOptions The custom options.
+     */
+    public function setCustomOptions(array $customOptions): void
+    {
+        $this->customOptions = $customOptions;
+    }
+    /**
+     * Gets the custom options.
+     *
+     * @since 0.1.0
+     *
+     * @return array<string, mixed> The custom options.
+     */
+    public function getCustomOptions(): array
+    {
+        return $this->customOptions;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function getJsonSchema(): array
+    {
+        return ['type' => 'object', 'properties' => [self::KEY_OUTPUT_MODALITIES => ['type' => 'array', 'items' => ['type' => 'string', 'enum' => ModalityEnum::getValues()], 'description' => 'Output modalities for the model.'], self::KEY_SYSTEM_INSTRUCTION => ['type' => 'string', 'description' => 'System instruction for the model.'], self::KEY_CANDIDATE_COUNT => ['type' => 'integer', 'minimum' => 1, 'description' => 'Number of response candidates to generate.'], self::KEY_MAX_TOKENS => ['type' => 'integer', 'minimum' => 1, 'description' => 'Maximum number of tokens to generate.'], self::KEY_TEMPERATURE => ['type' => 'number', 'minimum' => 0.0, 'maximum' => 2.0, 'description' => 'Temperature for randomness.'], self::KEY_TOP_P => ['type' => 'number', 'minimum' => 0.0, 'maximum' => 1.0, 'description' => 'Top-p nucleus sampling parameter.'], self::KEY_TOP_K => ['type' => 'integer', 'minimum' => 1, 'description' => 'Top-k sampling parameter.'], self::KEY_STOP_SEQUENCES => ['type' => 'array', 'items' => ['type' => 'string'], 'description' => 'Stop sequences.'], self::KEY_PRESENCE_PENALTY => ['type' => 'number', 'description' => 'Presence penalty for reducing repetition.'], self::KEY_FREQUENCY_PENALTY => ['type' => 'number', 'description' => 'Frequency penalty for reducing repetition.'], self::KEY_LOGPROBS => ['type' => 'boolean', 'description' => 'Whether to return log probabilities.'], self::KEY_TOP_LOGPROBS => ['type' => 'integer', 'minimum' => 1, 'description' => 'Number of top log probabilities to return.'], self::KEY_FUNCTION_DECLARATIONS => ['type' => 'array', 'items' => FunctionDeclaration::getJsonSchema(), 'description' => 'Function declarations available to the model.'], self::KEY_WEB_SEARCH => WebSearch::getJsonSchema(), self::KEY_OUTPUT_FILE_TYPE => ['type' => 'string', 'enum' => FileTypeEnum::getValues(), 'description' => 'Output file type.'], self::KEY_OUTPUT_MIME_TYPE => ['type' => 'string', 'description' => 'Output MIME type.'], self::KEY_OUTPUT_SCHEMA => ['type' => 'object', 'additionalProperties' => \true, 'description' => 'Output schema (JSON schema).'], self::KEY_OUTPUT_MEDIA_ORIENTATION => ['type' => 'string', 'enum' => MediaOrientationEnum::getValues(), 'description' => 'Output media orientation.'], self::KEY_OUTPUT_MEDIA_ASPECT_RATIO => ['type' => 'string', 'pattern' => '^\d+:\d+$', 'description' => 'Output media aspect ratio.'], self::KEY_OUTPUT_SPEECH_VOICE => ['type' => 'string', 'description' => 'Output speech voice.'], self::KEY_CUSTOM_OPTIONS => ['type' => 'object', 'additionalProperties' => \true, 'description' => 'Custom provider-specific options.']], 'additionalProperties' => \false];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     *
+     * @return ModelConfigArrayShape
+     */
+    public function toArray(): array
+    {
+        $data = [];
+        if ($this->outputModalities !== null) {
+            $data[self::KEY_OUTPUT_MODALITIES] = array_map(static function (ModalityEnum $modality): string {
+                return $modality->value;
+            }, $this->outputModalities);
+        }
+        if ($this->systemInstruction !== null) {
+            $data[self::KEY_SYSTEM_INSTRUCTION] = $this->systemInstruction;
+        }
+        if ($this->candidateCount !== null) {
+            $data[self::KEY_CANDIDATE_COUNT] = $this->candidateCount;
+        }
+        if ($this->maxTokens !== null) {
+            $data[self::KEY_MAX_TOKENS] = $this->maxTokens;
+        }
+        if ($this->temperature !== null) {
+            $data[self::KEY_TEMPERATURE] = $this->temperature;
+        }
+        if ($this->topP !== null) {
+            $data[self::KEY_TOP_P] = $this->topP;
+        }
+        if ($this->topK !== null) {
+            $data[self::KEY_TOP_K] = $this->topK;
+        }
+        if ($this->stopSequences !== null) {
+            $data[self::KEY_STOP_SEQUENCES] = $this->stopSequences;
+        }
+        if ($this->presencePenalty !== null) {
+            $data[self::KEY_PRESENCE_PENALTY] = $this->presencePenalty;
+        }
+        if ($this->frequencyPenalty !== null) {
+            $data[self::KEY_FREQUENCY_PENALTY] = $this->frequencyPenalty;
+        }
+        if ($this->logprobs !== null) {
+            $data[self::KEY_LOGPROBS] = $this->logprobs;
+        }
+        if ($this->topLogprobs !== null) {
+            $data[self::KEY_TOP_LOGPROBS] = $this->topLogprobs;
+        }
+        if ($this->functionDeclarations !== null) {
+            $data[self::KEY_FUNCTION_DECLARATIONS] = array_map(static function (FunctionDeclaration $function_declaration): array {
+                return $function_declaration->toArray();
+            }, $this->functionDeclarations);
+        }
+        if ($this->webSearch !== null) {
+            $data[self::KEY_WEB_SEARCH] = $this->webSearch->toArray();
+        }
+        if ($this->outputFileType !== null) {
+            $data[self::KEY_OUTPUT_FILE_TYPE] = $this->outputFileType->value;
+        }
+        if ($this->outputMimeType !== null) {
+            $data[self::KEY_OUTPUT_MIME_TYPE] = $this->outputMimeType;
+        }
+        if ($this->outputSchema !== null) {
+            $data[self::KEY_OUTPUT_SCHEMA] = $this->outputSchema;
+        }
+        if ($this->outputMediaOrientation !== null) {
+            $data[self::KEY_OUTPUT_MEDIA_ORIENTATION] = $this->outputMediaOrientation->value;
+        }
+        if ($this->outputMediaAspectRatio !== null) {
+            $data[self::KEY_OUTPUT_MEDIA_ASPECT_RATIO] = $this->outputMediaAspectRatio;
+        }
+        if ($this->outputSpeechVoice !== null) {
+            $data[self::KEY_OUTPUT_SPEECH_VOICE] = $this->outputSpeechVoice;
+        }
+        if (!empty($this->customOptions)) {
+            $data[self::KEY_CUSTOM_OPTIONS] = $this->customOptions;
+        }
+        return $data;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function fromArray(array $array): self
+    {
+        $config = new self();
+        if (isset($array[self::KEY_OUTPUT_MODALITIES])) {
+            $config->setOutputModalities(array_map(static fn(string $modality): ModalityEnum => ModalityEnum::from($modality), $array[self::KEY_OUTPUT_MODALITIES]));
+        }
+        if (isset($array[self::KEY_SYSTEM_INSTRUCTION])) {
+            $config->setSystemInstruction($array[self::KEY_SYSTEM_INSTRUCTION]);
+        }
+        if (isset($array[self::KEY_CANDIDATE_COUNT])) {
+            $config->setCandidateCount($array[self::KEY_CANDIDATE_COUNT]);
+        }
+        if (isset($array[self::KEY_MAX_TOKENS])) {
+            $config->setMaxTokens($array[self::KEY_MAX_TOKENS]);
+        }
+        if (isset($array[self::KEY_TEMPERATURE])) {
+            $config->setTemperature($array[self::KEY_TEMPERATURE]);
+        }
+        if (isset($array[self::KEY_TOP_P])) {
+            $config->setTopP($array[self::KEY_TOP_P]);
+        }
+        if (isset($array[self::KEY_TOP_K])) {
+            $config->setTopK($array[self::KEY_TOP_K]);
+        }
+        if (isset($array[self::KEY_STOP_SEQUENCES])) {
+            $config->setStopSequences($array[self::KEY_STOP_SEQUENCES]);
+        }
+        if (isset($array[self::KEY_PRESENCE_PENALTY])) {
+            $config->setPresencePenalty($array[self::KEY_PRESENCE_PENALTY]);
+        }
+        if (isset($array[self::KEY_FREQUENCY_PENALTY])) {
+            $config->setFrequencyPenalty($array[self::KEY_FREQUENCY_PENALTY]);
+        }
+        if (isset($array[self::KEY_LOGPROBS])) {
+            $config->setLogprobs($array[self::KEY_LOGPROBS]);
+        }
+        if (isset($array[self::KEY_TOP_LOGPROBS])) {
+            $config->setTopLogprobs($array[self::KEY_TOP_LOGPROBS]);
+        }
+        if (isset($array[self::KEY_FUNCTION_DECLARATIONS])) {
+            $config->setFunctionDeclarations(array_map(static function (array $function_declaration_data): FunctionDeclaration {
+                return FunctionDeclaration::fromArray($function_declaration_data);
+            }, $array[self::KEY_FUNCTION_DECLARATIONS]));
+        }
+        if (isset($array[self::KEY_WEB_SEARCH])) {
+            $config->setWebSearch(WebSearch::fromArray($array[self::KEY_WEB_SEARCH]));
+        }
+        if (isset($array[self::KEY_OUTPUT_FILE_TYPE])) {
+            $config->setOutputFileType(FileTypeEnum::from($array[self::KEY_OUTPUT_FILE_TYPE]));
+        }
+        if (isset($array[self::KEY_OUTPUT_MIME_TYPE])) {
+            $config->setOutputMimeType($array[self::KEY_OUTPUT_MIME_TYPE]);
+        }
+        if (isset($array[self::KEY_OUTPUT_SCHEMA])) {
+            $config->setOutputSchema($array[self::KEY_OUTPUT_SCHEMA]);
+        }
+        if (isset($array[self::KEY_OUTPUT_MEDIA_ORIENTATION])) {
+            $config->setOutputMediaOrientation(MediaOrientationEnum::from($array[self::KEY_OUTPUT_MEDIA_ORIENTATION]));
+        }
+        if (isset($array[self::KEY_OUTPUT_MEDIA_ASPECT_RATIO])) {
+            $config->setOutputMediaAspectRatio($array[self::KEY_OUTPUT_MEDIA_ASPECT_RATIO]);
+        }
+        if (isset($array[self::KEY_OUTPUT_SPEECH_VOICE])) {
+            $config->setOutputSpeechVoice($array[self::KEY_OUTPUT_SPEECH_VOICE]);
+        }
+        if (isset($array[self::KEY_CUSTOM_OPTIONS])) {
+            $config->setCustomOptions($array[self::KEY_CUSTOM_OPTIONS]);
+        }
+        return $config;
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Models/DTO/ModelMetadata.php b/src/wp-includes/php-ai-client/src/Providers/Models/DTO/ModelMetadata.php
new file mode 100644
index 0000000000000..ee2775a018f12
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Models/DTO/ModelMetadata.php
@@ -0,0 +1,165 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Models\DTO;
+
+use WordPress\AiClient\Common\AbstractDataTransferObject;
+use WordPress\AiClient\Common\Exception\InvalidArgumentException;
+use WordPress\AiClient\Providers\Models\Enums\CapabilityEnum;
+/**
+ * Represents metadata about an AI model.
+ *
+ * This class contains information about a specific AI model, including
+ * its identifier, display name, supported capabilities, and configuration options.
+ *
+ * @since 0.1.0
+ *
+ * @phpstan-import-type SupportedOptionArrayShape from SupportedOption
+ *
+ * @phpstan-type ModelMetadataArrayShape array{
+ *     id: string,
+ *     name: string,
+ *     supportedCapabilities: list<string>,
+ *     supportedOptions: list<SupportedOptionArrayShape>
+ * }
+ *
+ * @extends AbstractDataTransferObject<ModelMetadataArrayShape>
+ */
+class ModelMetadata extends AbstractDataTransferObject
+{
+    public const KEY_ID = 'id';
+    public const KEY_NAME = 'name';
+    public const KEY_SUPPORTED_CAPABILITIES = 'supportedCapabilities';
+    public const KEY_SUPPORTED_OPTIONS = 'supportedOptions';
+    /**
+     * @var string The model's unique identifier.
+     */
+    protected string $id;
+    /**
+     * @var string The model's display name.
+     */
+    protected string $name;
+    /**
+     * @var list<CapabilityEnum> The model's supported capabilities.
+     */
+    protected array $supportedCapabilities;
+    /**
+     * @var list<SupportedOption> The model's supported configuration options.
+     */
+    protected array $supportedOptions;
+    /**
+     * Constructor.
+     *
+     * @since 0.1.0
+     *
+     * @param string $id The model's unique identifier.
+     * @param string $name The model's display name.
+     * @param list<CapabilityEnum> $supportedCapabilities The model's supported capabilities.
+     * @param list<SupportedOption> $supportedOptions The model's supported configuration options.
+     *
+     * @throws InvalidArgumentException If arrays are not lists.
+     */
+    public function __construct(string $id, string $name, array $supportedCapabilities, array $supportedOptions)
+    {
+        if (!array_is_list($supportedCapabilities)) {
+            throw new InvalidArgumentException('Supported capabilities must be a list array.');
+        }
+        if (!array_is_list($supportedOptions)) {
+            throw new InvalidArgumentException('Supported options must be a list array.');
+        }
+        $this->id = $id;
+        $this->name = $name;
+        $this->supportedCapabilities = $supportedCapabilities;
+        $this->supportedOptions = $supportedOptions;
+    }
+    /**
+     * Gets the model's unique identifier.
+     *
+     * @since 0.1.0
+     *
+     * @return string The model ID.
+     */
+    public function getId(): string
+    {
+        return $this->id;
+    }
+    /**
+     * Gets the model's display name.
+     *
+     * @since 0.1.0
+     *
+     * @return string The model name.
+     */
+    public function getName(): string
+    {
+        return $this->name;
+    }
+    /**
+     * Gets the model's supported capabilities.
+     *
+     * @since 0.1.0
+     *
+     * @return list<CapabilityEnum> The supported capabilities.
+     */
+    public function getSupportedCapabilities(): array
+    {
+        return $this->supportedCapabilities;
+    }
+    /**
+     * Gets the model's supported configuration options.
+     *
+     * @since 0.1.0
+     *
+     * @return list<SupportedOption> The supported options.
+     */
+    public function getSupportedOptions(): array
+    {
+        return $this->supportedOptions;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function getJsonSchema(): array
+    {
+        return ['type' => 'object', 'properties' => [self::KEY_ID => ['type' => 'string', 'description' => 'The model\'s unique identifier.'], self::KEY_NAME => ['type' => 'string', 'description' => 'The model\'s display name.'], self::KEY_SUPPORTED_CAPABILITIES => ['type' => 'array', 'items' => ['type' => 'string', 'enum' => CapabilityEnum::getValues()], 'description' => 'The model\'s supported capabilities.'], self::KEY_SUPPORTED_OPTIONS => ['type' => 'array', 'items' => \WordPress\AiClient\Providers\Models\DTO\SupportedOption::getJsonSchema(), 'description' => 'The model\'s supported configuration options.']], 'required' => [self::KEY_ID, self::KEY_NAME, self::KEY_SUPPORTED_CAPABILITIES, self::KEY_SUPPORTED_OPTIONS]];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     *
+     * @return ModelMetadataArrayShape
+     */
+    public function toArray(): array
+    {
+        return [self::KEY_ID => $this->id, self::KEY_NAME => $this->name, self::KEY_SUPPORTED_CAPABILITIES => array_map(static fn(CapabilityEnum $capability): string => $capability->value, $this->supportedCapabilities), self::KEY_SUPPORTED_OPTIONS => array_map(static fn(\WordPress\AiClient\Providers\Models\DTO\SupportedOption $option): array => $option->toArray(), $this->supportedOptions)];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function fromArray(array $array): self
+    {
+        static::validateFromArrayData($array, [self::KEY_ID, self::KEY_NAME, self::KEY_SUPPORTED_CAPABILITIES, self::KEY_SUPPORTED_OPTIONS]);
+        return new self($array[self::KEY_ID], $array[self::KEY_NAME], array_map(static fn(string $capability): CapabilityEnum => CapabilityEnum::from($capability), $array[self::KEY_SUPPORTED_CAPABILITIES]), array_map(static fn(array $optionData): \WordPress\AiClient\Providers\Models\DTO\SupportedOption => \WordPress\AiClient\Providers\Models\DTO\SupportedOption::fromArray($optionData), $array[self::KEY_SUPPORTED_OPTIONS]));
+    }
+    /**
+     * Performs a deep clone of the model metadata.
+     *
+     * This method ensures that supported option objects are cloned to prevent
+     * modifications to the cloned metadata from affecting the original.
+     *
+     * @since 0.4.1
+     */
+    public function __clone()
+    {
+        $clonedOptions = [];
+        foreach ($this->supportedOptions as $option) {
+            $clonedOptions[] = clone $option;
+        }
+        $this->supportedOptions = $clonedOptions;
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Models/DTO/ModelRequirements.php b/src/wp-includes/php-ai-client/src/Providers/Models/DTO/ModelRequirements.php
new file mode 100644
index 0000000000000..0f2bb865ca55a
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Models/DTO/ModelRequirements.php
@@ -0,0 +1,315 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Models\DTO;
+
+use InvalidArgumentException;
+use WordPress\AiClient\Common\AbstractDataTransferObject;
+use WordPress\AiClient\Messages\DTO\Message;
+use WordPress\AiClient\Messages\Enums\ModalityEnum;
+use WordPress\AiClient\Providers\Models\Enums\CapabilityEnum;
+use WordPress\AiClient\Providers\Models\Enums\OptionEnum;
+/**
+ * Represents requirements that implementing code has for AI model selection.
+ *
+ * This class defines the capabilities and options that a model must support
+ * in order to be considered suitable for the implementing code's needs.
+ *
+ * @since 0.1.0
+ *
+ * @phpstan-import-type RequiredOptionArrayShape from RequiredOption
+ *
+ * @phpstan-type ModelRequirementsArrayShape array{
+ *     requiredCapabilities: list<string>,
+ *     requiredOptions: list<RequiredOptionArrayShape>
+ * }
+ *
+ * @extends AbstractDataTransferObject<ModelRequirementsArrayShape>
+ */
+class ModelRequirements extends AbstractDataTransferObject
+{
+    public const KEY_REQUIRED_CAPABILITIES = 'requiredCapabilities';
+    public const KEY_REQUIRED_OPTIONS = 'requiredOptions';
+    /**
+     * @var list<CapabilityEnum> The capabilities that the model must support.
+     */
+    protected array $requiredCapabilities;
+    /**
+     * @var list<RequiredOption> The options that the model must support with specific values.
+     */
+    protected array $requiredOptions;
+    /**
+     * Constructor.
+     *
+     * @since 0.1.0
+     *
+     * @param list<CapabilityEnum> $requiredCapabilities The capabilities that the model must support.
+     * @param list<RequiredOption> $requiredOptions The options that the model must support with specific values.
+     *
+     * @throws InvalidArgumentException If arrays are not lists.
+     */
+    public function __construct(array $requiredCapabilities, array $requiredOptions)
+    {
+        if (!array_is_list($requiredCapabilities)) {
+            throw new InvalidArgumentException('Required capabilities must be a list array.');
+        }
+        if (!array_is_list($requiredOptions)) {
+            throw new InvalidArgumentException('Required options must be a list array.');
+        }
+        $this->requiredCapabilities = $requiredCapabilities;
+        $this->requiredOptions = $requiredOptions;
+    }
+    /**
+     * Gets the capabilities that the model must support.
+     *
+     * @since 0.1.0
+     *
+     * @return list<CapabilityEnum> The required capabilities.
+     */
+    public function getRequiredCapabilities(): array
+    {
+        return $this->requiredCapabilities;
+    }
+    /**
+     * Gets the options that the model must support with specific values.
+     *
+     * @since 0.1.0
+     *
+     * @return list<RequiredOption> The required options.
+     */
+    public function getRequiredOptions(): array
+    {
+        return $this->requiredOptions;
+    }
+    /**
+     * Checks whether the given model metadata meets these requirements.
+     *
+     * @since 0.2.0
+     *
+     * @param ModelMetadata $metadata The model metadata to check against.
+     * @return bool True if the model meets all requirements, false otherwise.
+     */
+    public function areMetBy(\WordPress\AiClient\Providers\Models\DTO\ModelMetadata $metadata): bool
+    {
+        // Create lookup maps for better performance (instead of nested foreach loops)
+        $capabilitiesMap = [];
+        foreach ($metadata->getSupportedCapabilities() as $capability) {
+            $capabilitiesMap[$capability->value] = $capability;
+        }
+        $optionsMap = [];
+        foreach ($metadata->getSupportedOptions() as $option) {
+            $optionsMap[$option->getName()->value] = $option;
+        }
+        // Check if all required capabilities are supported using map lookup
+        foreach ($this->requiredCapabilities as $requiredCapability) {
+            if (!isset($capabilitiesMap[$requiredCapability->value])) {
+                return \false;
+            }
+        }
+        // Check if all required options are supported with the specified values
+        foreach ($this->requiredOptions as $requiredOption) {
+            // Use map lookup instead of linear search
+            if (!isset($optionsMap[$requiredOption->getName()->value])) {
+                return \false;
+            }
+            $supportedOption = $optionsMap[$requiredOption->getName()->value];
+            // Check if the required value is supported by this option
+            if (!$supportedOption->isSupportedValue($requiredOption->getValue())) {
+                return \false;
+            }
+        }
+        return \true;
+    }
+    /**
+     * Creates ModelRequirements from prompt data and model configuration.
+     *
+     * @since 0.2.0
+     *
+     * @param CapabilityEnum $capability The capability the model must support.
+     * @param list<Message> $messages The messages in the conversation.
+     * @param ModelConfig $modelConfig The model configuration.
+     * @return self The created requirements.
+     */
+    public static function fromPromptData(CapabilityEnum $capability, array $messages, \WordPress\AiClient\Providers\Models\DTO\ModelConfig $modelConfig): self
+    {
+        // Start with base capability
+        $capabilities = [$capability];
+        $inputModalities = [];
+        // Check if we have chat history (multiple messages)
+        if (count($messages) > 1) {
+            $capabilities[] = CapabilityEnum::chatHistory();
+        }
+        // Analyze all messages to determine required input modalities
+        $hasFunctionMessageParts = \false;
+        foreach ($messages as $message) {
+            foreach ($message->getParts() as $part) {
+                // Check for text input
+                if ($part->getType()->isText()) {
+                    $inputModalities[] = ModalityEnum::text();
+                }
+                // Check for file inputs
+                if ($part->getType()->isFile()) {
+                    $file = $part->getFile();
+                    if ($file !== null) {
+                        if ($file->isImage()) {
+                            $inputModalities[] = ModalityEnum::image();
+                        } elseif ($file->isAudio()) {
+                            $inputModalities[] = ModalityEnum::audio();
+                        } elseif ($file->isVideo()) {
+                            $inputModalities[] = ModalityEnum::video();
+                        } elseif ($file->isDocument() || $file->isText()) {
+                            $inputModalities[] = ModalityEnum::document();
+                        }
+                    }
+                }
+                // Check for function calls/responses (these might require special capabilities)
+                if ($part->getType()->isFunctionCall() || $part->getType()->isFunctionResponse()) {
+                    $hasFunctionMessageParts = \true;
+                }
+            }
+        }
+        // Convert ModelConfig to RequiredOptions
+        $requiredOptions = self::toRequiredOptions($modelConfig);
+        // Add additional options based on message analysis
+        if ($hasFunctionMessageParts) {
+            $requiredOptions = self::includeInRequiredOptions($requiredOptions, new \WordPress\AiClient\Providers\Models\DTO\RequiredOption(OptionEnum::functionDeclarations(), \true));
+        }
+        // Add input modalities if we have any inputs
+        if (!empty($inputModalities)) {
+            // Remove duplicates
+            $inputModalities = array_unique($inputModalities, \SORT_REGULAR);
+            $requiredOptions = self::includeInRequiredOptions($requiredOptions, new \WordPress\AiClient\Providers\Models\DTO\RequiredOption(OptionEnum::inputModalities(), array_values($inputModalities)));
+        }
+        // Step 6: Return new ModelRequirements
+        return new self($capabilities, $requiredOptions);
+    }
+    /**
+     * Converts ModelConfig to an array of RequiredOptions.
+     *
+     * @since 0.2.0
+     *
+     * @param ModelConfig $modelConfig The model configuration.
+     * @return list<RequiredOption> The required options.
+     */
+    private static function toRequiredOptions(\WordPress\AiClient\Providers\Models\DTO\ModelConfig $modelConfig): array
+    {
+        $requiredOptions = [];
+        // Map properties that have corresponding OptionEnum values
+        if ($modelConfig->getOutputModalities() !== null) {
+            $requiredOptions[] = new \WordPress\AiClient\Providers\Models\DTO\RequiredOption(OptionEnum::outputModalities(), $modelConfig->getOutputModalities());
+        }
+        if ($modelConfig->getSystemInstruction() !== null) {
+            $requiredOptions[] = new \WordPress\AiClient\Providers\Models\DTO\RequiredOption(OptionEnum::systemInstruction(), $modelConfig->getSystemInstruction());
+        }
+        if ($modelConfig->getCandidateCount() !== null) {
+            $requiredOptions[] = new \WordPress\AiClient\Providers\Models\DTO\RequiredOption(OptionEnum::candidateCount(), $modelConfig->getCandidateCount());
+        }
+        if ($modelConfig->getMaxTokens() !== null) {
+            $requiredOptions[] = new \WordPress\AiClient\Providers\Models\DTO\RequiredOption(OptionEnum::maxTokens(), $modelConfig->getMaxTokens());
+        }
+        if ($modelConfig->getTemperature() !== null) {
+            $requiredOptions[] = new \WordPress\AiClient\Providers\Models\DTO\RequiredOption(OptionEnum::temperature(), $modelConfig->getTemperature());
+        }
+        if ($modelConfig->getTopP() !== null) {
+            $requiredOptions[] = new \WordPress\AiClient\Providers\Models\DTO\RequiredOption(OptionEnum::topP(), $modelConfig->getTopP());
+        }
+        if ($modelConfig->getTopK() !== null) {
+            $requiredOptions[] = new \WordPress\AiClient\Providers\Models\DTO\RequiredOption(OptionEnum::topK(), $modelConfig->getTopK());
+        }
+        if ($modelConfig->getOutputMimeType() !== null) {
+            $requiredOptions[] = new \WordPress\AiClient\Providers\Models\DTO\RequiredOption(OptionEnum::outputMimeType(), $modelConfig->getOutputMimeType());
+        }
+        if ($modelConfig->getOutputSchema() !== null) {
+            $requiredOptions[] = new \WordPress\AiClient\Providers\Models\DTO\RequiredOption(OptionEnum::outputSchema(), $modelConfig->getOutputSchema());
+        }
+        // Handle properties without OptionEnum values as custom options
+        if ($modelConfig->getStopSequences() !== null) {
+            $requiredOptions[] = new \WordPress\AiClient\Providers\Models\DTO\RequiredOption(OptionEnum::stopSequences(), $modelConfig->getStopSequences());
+        }
+        if ($modelConfig->getPresencePenalty() !== null) {
+            $requiredOptions[] = new \WordPress\AiClient\Providers\Models\DTO\RequiredOption(OptionEnum::presencePenalty(), $modelConfig->getPresencePenalty());
+        }
+        if ($modelConfig->getFrequencyPenalty() !== null) {
+            $requiredOptions[] = new \WordPress\AiClient\Providers\Models\DTO\RequiredOption(OptionEnum::frequencyPenalty(), $modelConfig->getFrequencyPenalty());
+        }
+        if ($modelConfig->getLogprobs() !== null) {
+            $requiredOptions[] = new \WordPress\AiClient\Providers\Models\DTO\RequiredOption(OptionEnum::logprobs(), $modelConfig->getLogprobs());
+        }
+        if ($modelConfig->getTopLogprobs() !== null) {
+            $requiredOptions[] = new \WordPress\AiClient\Providers\Models\DTO\RequiredOption(OptionEnum::topLogprobs(), $modelConfig->getTopLogprobs());
+        }
+        if ($modelConfig->getFunctionDeclarations() !== null) {
+            $requiredOptions[] = new \WordPress\AiClient\Providers\Models\DTO\RequiredOption(OptionEnum::functionDeclarations(), \true);
+        }
+        if ($modelConfig->getWebSearch() !== null) {
+            $requiredOptions[] = new \WordPress\AiClient\Providers\Models\DTO\RequiredOption(OptionEnum::webSearch(), \true);
+        }
+        if ($modelConfig->getOutputFileType() !== null) {
+            $requiredOptions[] = new \WordPress\AiClient\Providers\Models\DTO\RequiredOption(OptionEnum::outputFileType(), $modelConfig->getOutputFileType());
+        }
+        if ($modelConfig->getOutputMediaOrientation() !== null) {
+            $requiredOptions[] = new \WordPress\AiClient\Providers\Models\DTO\RequiredOption(OptionEnum::outputMediaOrientation(), $modelConfig->getOutputMediaOrientation());
+        }
+        if ($modelConfig->getOutputMediaAspectRatio() !== null) {
+            $requiredOptions[] = new \WordPress\AiClient\Providers\Models\DTO\RequiredOption(OptionEnum::outputMediaAspectRatio(), $modelConfig->getOutputMediaAspectRatio());
+        }
+        // Add custom options as individual RequiredOptions
+        foreach ($modelConfig->getCustomOptions() as $key => $value) {
+            $requiredOptions[] = new \WordPress\AiClient\Providers\Models\DTO\RequiredOption(OptionEnum::customOptions(), [$key => $value]);
+        }
+        return $requiredOptions;
+    }
+    /**
+     * Includes a RequiredOption in the array, ensuring no duplicates based on option name.
+     *
+     * @since 0.2.0
+     *
+     * @param list<RequiredOption> $requiredOptions The existing required options.
+     * @param RequiredOption $newOption The new option to include.
+     * @return list<RequiredOption> The updated required options array.
+     */
+    private static function includeInRequiredOptions(array $requiredOptions, \WordPress\AiClient\Providers\Models\DTO\RequiredOption $newOption): array
+    {
+        // Check if we already have this option name
+        foreach ($requiredOptions as $index => $existingOption) {
+            if ($existingOption->getName()->equals($newOption->getName())) {
+                // Replace existing option with new one
+                $requiredOptions[$index] = $newOption;
+                return $requiredOptions;
+            }
+        }
+        // Option not found, add it
+        $requiredOptions[] = $newOption;
+        return $requiredOptions;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function getJsonSchema(): array
+    {
+        return ['type' => 'object', 'properties' => [self::KEY_REQUIRED_CAPABILITIES => ['type' => 'array', 'items' => ['type' => 'string', 'enum' => CapabilityEnum::getValues()], 'description' => 'The capabilities that the model must support.'], self::KEY_REQUIRED_OPTIONS => ['type' => 'array', 'items' => \WordPress\AiClient\Providers\Models\DTO\RequiredOption::getJsonSchema(), 'description' => 'The options that the model must support with specific values.']], 'required' => [self::KEY_REQUIRED_CAPABILITIES, self::KEY_REQUIRED_OPTIONS]];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     *
+     * @return ModelRequirementsArrayShape
+     */
+    public function toArray(): array
+    {
+        return [self::KEY_REQUIRED_CAPABILITIES => array_map(static fn(CapabilityEnum $capability): string => $capability->value, $this->requiredCapabilities), self::KEY_REQUIRED_OPTIONS => array_map(static fn(\WordPress\AiClient\Providers\Models\DTO\RequiredOption $option): array => $option->toArray(), $this->requiredOptions)];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function fromArray(array $array): self
+    {
+        static::validateFromArrayData($array, [self::KEY_REQUIRED_CAPABILITIES, self::KEY_REQUIRED_OPTIONS]);
+        return new self(array_map(static fn(string $capability): CapabilityEnum => CapabilityEnum::from($capability), $array[self::KEY_REQUIRED_CAPABILITIES]), array_map(static fn(array $optionData): \WordPress\AiClient\Providers\Models\DTO\RequiredOption => \WordPress\AiClient\Providers\Models\DTO\RequiredOption::fromArray($optionData), $array[self::KEY_REQUIRED_OPTIONS]));
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Models/DTO/RequiredOption.php b/src/wp-includes/php-ai-client/src/Providers/Models/DTO/RequiredOption.php
new file mode 100644
index 0000000000000..e459a74e9cfb3
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Models/DTO/RequiredOption.php
@@ -0,0 +1,100 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Models\DTO;
+
+use WordPress\AiClient\Common\AbstractDataTransferObject;
+use WordPress\AiClient\Providers\Models\Enums\OptionEnum;
+/**
+ * Represents an option that the implementing code requires the model to support.
+ *
+ * This class defines an option that the model must support with a specific value
+ * for it to be considered suitable for the implementing code's requirements.
+ *
+ * @since 0.1.0
+ *
+ * @phpstan-type RequiredOptionArrayShape array{
+ *     name: string,
+ *     value: mixed
+ * }
+ *
+ * @extends AbstractDataTransferObject<RequiredOptionArrayShape>
+ */
+class RequiredOption extends AbstractDataTransferObject
+{
+    public const KEY_NAME = 'name';
+    public const KEY_VALUE = 'value';
+    /**
+     * @var OptionEnum The option name.
+     */
+    protected OptionEnum $name;
+    /**
+     * @var mixed The value that the model must support for this option.
+     */
+    protected $value;
+    /**
+     * Constructor.
+     *
+     * @since 0.1.0
+     *
+     * @param OptionEnum $name The option name.
+     * @param mixed $value The value that the model must support for this option.
+     */
+    public function __construct(OptionEnum $name, $value)
+    {
+        $this->name = $name;
+        $this->value = $value;
+    }
+    /**
+     * Gets the option name.
+     *
+     * @since 0.1.0
+     *
+     * @return OptionEnum The option name.
+     */
+    public function getName(): OptionEnum
+    {
+        return $this->name;
+    }
+    /**
+     * Gets the value that the model must support for this option.
+     *
+     * @since 0.1.0
+     *
+     * @return mixed The value that the model must support.
+     */
+    public function getValue()
+    {
+        return $this->value;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function getJsonSchema(): array
+    {
+        return ['type' => 'object', 'properties' => [self::KEY_NAME => ['type' => 'string', 'enum' => OptionEnum::getValues(), 'description' => 'The option name.'], self::KEY_VALUE => ['oneOf' => [['type' => 'string'], ['type' => 'number'], ['type' => 'boolean'], ['type' => 'null'], ['type' => 'array'], ['type' => 'object']], 'description' => 'The value that the model must support for this option.']], 'required' => [self::KEY_NAME, self::KEY_VALUE]];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     *
+     * @return RequiredOptionArrayShape
+     */
+    public function toArray(): array
+    {
+        return [self::KEY_NAME => $this->name->value, self::KEY_VALUE => $this->value];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function fromArray(array $array): self
+    {
+        static::validateFromArrayData($array, [self::KEY_NAME, self::KEY_VALUE]);
+        return new self(OptionEnum::from($array[self::KEY_NAME]), $array[self::KEY_VALUE]);
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Models/DTO/SupportedOption.php b/src/wp-includes/php-ai-client/src/Providers/Models/DTO/SupportedOption.php
new file mode 100644
index 0000000000000..9fd337eb6152a
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Models/DTO/SupportedOption.php
@@ -0,0 +1,142 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Models\DTO;
+
+use WordPress\AiClient\Common\AbstractDataTransferObject;
+use WordPress\AiClient\Common\Exception\InvalidArgumentException;
+use WordPress\AiClient\Providers\Models\Enums\OptionEnum;
+/**
+ * Represents a supported configuration option for an AI model.
+ *
+ * This class defines an option that a model supports, including its name
+ * and the values that are valid for that option.
+ *
+ * @since 0.1.0
+ *
+ * @phpstan-type SupportedOptionArrayShape array{
+ *     name: string,
+ *     supportedValues?: list<mixed>
+ * }
+ *
+ * @extends AbstractDataTransferObject<SupportedOptionArrayShape>
+ */
+class SupportedOption extends AbstractDataTransferObject
+{
+    public const KEY_NAME = 'name';
+    public const KEY_SUPPORTED_VALUES = 'supportedValues';
+    /**
+     * @var OptionEnum The option name.
+     */
+    protected OptionEnum $name;
+    /**
+     * @var list<mixed>|null The supported values for this option.
+     */
+    protected ?array $supportedValues;
+    /**
+     * Constructor.
+     *
+     * @since 0.1.0
+     *
+     * @param OptionEnum $name The option name.
+     * @param list<mixed>|null $supportedValues The supported values for this option, or null if any value is supported.
+     *
+     * @throws InvalidArgumentException If supportedValues is not null and not a list.
+     */
+    public function __construct(OptionEnum $name, ?array $supportedValues = null)
+    {
+        if ($supportedValues !== null && !array_is_list($supportedValues)) {
+            throw new InvalidArgumentException('Supported values must be a list array.');
+        }
+        $this->name = $name;
+        $this->supportedValues = $supportedValues;
+    }
+    /**
+     * Gets the option name.
+     *
+     * @since 0.1.0
+     *
+     * @return OptionEnum The option name.
+     */
+    public function getName(): OptionEnum
+    {
+        return $this->name;
+    }
+    /**
+     * Checks if a value is supported for this option.
+     *
+     * @since 0.1.0
+     *
+     * @param mixed $value The value to check.
+     * @return bool True if the value is supported, false otherwise.
+     */
+    public function isSupportedValue($value): bool
+    {
+        // If supportedValues is null, any value is supported
+        if ($this->supportedValues === null) {
+            return \true;
+        }
+        // If the value is an array, consider it a set (i.e. order doesn't matter).
+        if (is_array($value)) {
+            sort($value);
+            foreach ($this->supportedValues as $supportedValue) {
+                if (!is_array($supportedValue)) {
+                    continue;
+                }
+                sort($supportedValue);
+                if ($value === $supportedValue) {
+                    return \true;
+                }
+            }
+            return \false;
+        }
+        return in_array($value, $this->supportedValues, \true);
+    }
+    /**
+     * Gets the supported values for this option.
+     *
+     * @since 0.1.0
+     *
+     * @return list<mixed>|null The supported values, or null if any value is supported.
+     */
+    public function getSupportedValues(): ?array
+    {
+        return $this->supportedValues;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function getJsonSchema(): array
+    {
+        return ['type' => 'object', 'properties' => [self::KEY_NAME => ['type' => 'string', 'enum' => OptionEnum::getValues(), 'description' => 'The option name.'], self::KEY_SUPPORTED_VALUES => ['type' => 'array', 'items' => ['oneOf' => [['type' => 'string'], ['type' => 'number'], ['type' => 'boolean'], ['type' => 'null'], ['type' => 'array'], ['type' => 'object']]], 'description' => 'The supported values for this option.']], 'required' => [self::KEY_NAME]];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     *
+     * @return SupportedOptionArrayShape
+     */
+    public function toArray(): array
+    {
+        $data = [self::KEY_NAME => $this->name->value];
+        if ($this->supportedValues !== null) {
+            /** @var list<mixed> $supportedValues */
+            $supportedValues = $this->supportedValues;
+            $data[self::KEY_SUPPORTED_VALUES] = $supportedValues;
+        }
+        return $data;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function fromArray(array $array): self
+    {
+        static::validateFromArrayData($array, [self::KEY_NAME]);
+        return new self(OptionEnum::from($array[self::KEY_NAME]), $array[self::KEY_SUPPORTED_VALUES] ?? null);
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Models/Enums/CapabilityEnum.php b/src/wp-includes/php-ai-client/src/Providers/Models/Enums/CapabilityEnum.php
new file mode 100644
index 0000000000000..b0bcf5abec89a
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Models/Enums/CapabilityEnum.php
@@ -0,0 +1,63 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Models\Enums;
+
+use WordPress\AiClient\Common\AbstractEnum;
+/**
+ * Enum for model capabilities.
+ *
+ * @since 0.1.0
+ *
+ * @method static self textGeneration() Creates an instance for TEXT_GENERATION capability.
+ * @method static self imageGeneration() Creates an instance for IMAGE_GENERATION capability.
+ * @method static self textToSpeechConversion() Creates an instance for TEXT_TO_SPEECH_CONVERSION capability.
+ * @method static self speechGeneration() Creates an instance for SPEECH_GENERATION capability.
+ * @method static self musicGeneration() Creates an instance for MUSIC_GENERATION capability.
+ * @method static self videoGeneration() Creates an instance for VIDEO_GENERATION capability.
+ * @method static self embeddingGeneration() Creates an instance for EMBEDDING_GENERATION capability.
+ * @method static self chatHistory() Creates an instance for CHAT_HISTORY capability.
+ * @method bool isTextGeneration() Checks if the capability is TEXT_GENERATION.
+ * @method bool isImageGeneration() Checks if the capability is IMAGE_GENERATION.
+ * @method bool isTextToSpeechConversion() Checks if the capability is TEXT_TO_SPEECH_CONVERSION.
+ * @method bool isSpeechGeneration() Checks if the capability is SPEECH_GENERATION.
+ * @method bool isMusicGeneration() Checks if the capability is MUSIC_GENERATION.
+ * @method bool isVideoGeneration() Checks if the capability is VIDEO_GENERATION.
+ * @method bool isEmbeddingGeneration() Checks if the capability is EMBEDDING_GENERATION.
+ * @method bool isChatHistory() Checks if the capability is CHAT_HISTORY.
+ */
+class CapabilityEnum extends AbstractEnum
+{
+    /**
+     * Text generation capability.
+     */
+    public const TEXT_GENERATION = 'text_generation';
+    /**
+     * Image generation capability.
+     */
+    public const IMAGE_GENERATION = 'image_generation';
+    /**
+     * Text to speech conversion capability.
+     */
+    public const TEXT_TO_SPEECH_CONVERSION = 'text_to_speech_conversion';
+    /**
+     * Speech generation capability.
+     */
+    public const SPEECH_GENERATION = 'speech_generation';
+    /**
+     * Music generation capability.
+     */
+    public const MUSIC_GENERATION = 'music_generation';
+    /**
+     * Video generation capability.
+     */
+    public const VIDEO_GENERATION = 'video_generation';
+    /**
+     * Embedding generation capability.
+     */
+    public const EMBEDDING_GENERATION = 'embedding_generation';
+    /**
+     * Chat history support capability.
+     */
+    public const CHAT_HISTORY = 'chat_history';
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Models/Enums/OptionEnum.php b/src/wp-includes/php-ai-client/src/Providers/Models/Enums/OptionEnum.php
new file mode 100644
index 0000000000000..c0d089153cf07
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Models/Enums/OptionEnum.php
@@ -0,0 +1,107 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Models\Enums;
+
+use ReflectionClass;
+use WordPress\AiClient\Common\AbstractEnum;
+use WordPress\AiClient\Providers\Models\DTO\ModelConfig;
+/**
+ * Enum for model options.
+ *
+ * This enum dynamically includes all options from ModelConfig KEY_* constants
+ * in addition to the explicitly defined constants below.
+ *
+ * Explicitly defined option (not in ModelConfig):
+ * @method static self inputModalities() Creates an instance for INPUT_MODALITIES option.
+ * @method bool isInputModalities() Checks if the option is INPUT_MODALITIES.
+ *
+ * Dynamically loaded from ModelConfig KEY_* constants:
+ * @method static self candidateCount() Creates an instance for CANDIDATE_COUNT option.
+ * @method static self customOptions() Creates an instance for CUSTOM_OPTIONS option.
+ * @method static self frequencyPenalty() Creates an instance for FREQUENCY_PENALTY option.
+ * @method static self functionDeclarations() Creates an instance for FUNCTION_DECLARATIONS option.
+ * @method static self logprobs() Creates an instance for LOGPROBS option.
+ * @method static self maxTokens() Creates an instance for MAX_TOKENS option.
+ * @method static self outputFileType() Creates an instance for OUTPUT_FILE_TYPE option.
+ * @method static self outputMediaAspectRatio() Creates an instance for OUTPUT_MEDIA_ASPECT_RATIO option.
+ * @method static self outputMediaOrientation() Creates an instance for OUTPUT_MEDIA_ORIENTATION option.
+ * @method static self outputMimeType() Creates an instance for OUTPUT_MIME_TYPE option.
+ * @method static self outputModalities() Creates an instance for OUTPUT_MODALITIES option.
+ * @method static self outputSchema() Creates an instance for OUTPUT_SCHEMA option.
+ * @method static self outputSpeechVoice() Creates an instance for OUTPUT_SPEECH_VOICE option.
+ * @method static self presencePenalty() Creates an instance for PRESENCE_PENALTY option.
+ * @method static self stopSequences() Creates an instance for STOP_SEQUENCES option.
+ * @method static self systemInstruction() Creates an instance for SYSTEM_INSTRUCTION option.
+ * @method static self temperature() Creates an instance for TEMPERATURE option.
+ * @method static self topK() Creates an instance for TOP_K option.
+ * @method static self topLogprobs() Creates an instance for TOP_LOGPROBS option.
+ * @method static self topP() Creates an instance for TOP_P option.
+ * @method static self webSearch() Creates an instance for WEB_SEARCH option.
+ * @method bool isCandidateCount() Checks if the option is CANDIDATE_COUNT.
+ * @method bool isCustomOptions() Checks if the option is CUSTOM_OPTIONS.
+ * @method bool isFrequencyPenalty() Checks if the option is FREQUENCY_PENALTY.
+ * @method bool isFunctionDeclarations() Checks if the option is FUNCTION_DECLARATIONS.
+ * @method bool isLogprobs() Checks if the option is LOGPROBS.
+ * @method bool isMaxTokens() Checks if the option is MAX_TOKENS.
+ * @method bool isOutputFileType() Checks if the option is OUTPUT_FILE_TYPE.
+ * @method bool isOutputMediaAspectRatio() Checks if the option is OUTPUT_MEDIA_ASPECT_RATIO.
+ * @method bool isOutputMediaOrientation() Checks if the option is OUTPUT_MEDIA_ORIENTATION.
+ * @method bool isOutputMimeType() Checks if the option is OUTPUT_MIME_TYPE.
+ * @method bool isOutputModalities() Checks if the option is OUTPUT_MODALITIES.
+ * @method bool isOutputSchema() Checks if the option is OUTPUT_SCHEMA.
+ * @method bool isOutputSpeechVoice() Checks if the option is OUTPUT_SPEECH_VOICE.
+ * @method bool isPresencePenalty() Checks if the option is PRESENCE_PENALTY.
+ * @method bool isStopSequences() Checks if the option is STOP_SEQUENCES.
+ * @method bool isSystemInstruction() Checks if the option is SYSTEM_INSTRUCTION.
+ * @method bool isTemperature() Checks if the option is TEMPERATURE.
+ * @method bool isTopK() Checks if the option is TOP_K.
+ * @method bool isTopLogprobs() Checks if the option is TOP_LOGPROBS.
+ * @method bool isTopP() Checks if the option is TOP_P.
+ * @method bool isWebSearch() Checks if the option is WEB_SEARCH.
+ *
+ * @since 0.1.0
+ */
+class OptionEnum extends AbstractEnum
+{
+    /**
+     * Input modalities option.
+     *
+     * This constant is not in ModelConfig as it's derived from message content,
+     * not configured directly.
+     */
+    public const INPUT_MODALITIES = 'input_modalities';
+    /**
+     * Determines the class enumerations by reflecting on class constants.
+     *
+     * Overrides the parent method to dynamically add constants from ModelConfig
+     * that are prefixed with KEY_. These are transformed to remove the KEY_ prefix
+     * and converted to snake_case values.
+     *
+     * @since 0.1.0
+     *
+     * @param class-string $className The fully qualified class name.
+     * @return array<string, string> The enum constants.
+     */
+    protected static function determineClassEnumerations(string $className): array
+    {
+        // Start with the constants defined in this class using parent method
+        $constants = parent::determineClassEnumerations($className);
+        // Use reflection to get all constants from ModelConfig
+        $modelConfigReflection = new ReflectionClass(ModelConfig::class);
+        $modelConfigConstants = $modelConfigReflection->getConstants();
+        // Add ModelConfig constants that start with KEY_
+        foreach ($modelConfigConstants as $constantName => $constantValue) {
+            if (str_starts_with($constantName, 'KEY_')) {
+                // Remove KEY_ prefix to get the enum constant name
+                $enumConstantName = substr($constantName, 4);
+                // The value is the snake_case version stored in ModelConfig
+                // ModelConfig already stores these as snake_case strings
+                if (is_string($constantValue)) {
+                    $constants[$enumConstantName] = $constantValue;
+                }
+            }
+        }
+        return $constants;
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Models/ImageGeneration/Contracts/ImageGenerationModelInterface.php b/src/wp-includes/php-ai-client/src/Providers/Models/ImageGeneration/Contracts/ImageGenerationModelInterface.php
new file mode 100644
index 0000000000000..34fb5ad91f6b8
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Models/ImageGeneration/Contracts/ImageGenerationModelInterface.php
@@ -0,0 +1,26 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Models\ImageGeneration\Contracts;
+
+use WordPress\AiClient\Messages\DTO\Message;
+use WordPress\AiClient\Results\DTO\GenerativeAiResult;
+/**
+ * Interface for models that support image generation.
+ *
+ * Provides synchronous methods for generating images from text prompts.
+ *
+ * @since 0.1.0
+ */
+interface ImageGenerationModelInterface
+{
+    /**
+     * Generates images from a prompt.
+     *
+     * @since 0.1.0
+     *
+     * @param list<Message> $prompt Array of messages containing the image generation prompt.
+     * @return GenerativeAiResult Result containing generated images.
+     */
+    public function generateImageResult(array $prompt): GenerativeAiResult;
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Models/ImageGeneration/Contracts/ImageGenerationOperationModelInterface.php b/src/wp-includes/php-ai-client/src/Providers/Models/ImageGeneration/Contracts/ImageGenerationOperationModelInterface.php
new file mode 100644
index 0000000000000..52470600117a3
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Models/ImageGeneration/Contracts/ImageGenerationOperationModelInterface.php
@@ -0,0 +1,26 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Models\ImageGeneration\Contracts;
+
+use WordPress\AiClient\Messages\DTO\Message;
+use WordPress\AiClient\Operations\DTO\GenerativeAiOperation;
+/**
+ * Interface for models that support asynchronous image generation operations.
+ *
+ * Provides methods for initiating long-running image generation tasks.
+ *
+ * @since 0.1.0
+ */
+interface ImageGenerationOperationModelInterface
+{
+    /**
+     * Creates an image generation operation.
+     *
+     * @since 0.1.0
+     *
+     * @param list<Message> $prompt Array of messages containing the image generation prompt.
+     * @return GenerativeAiOperation The initiated image generation operation.
+     */
+    public function generateImageOperation(array $prompt): GenerativeAiOperation;
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Models/SpeechGeneration/Contracts/SpeechGenerationModelInterface.php b/src/wp-includes/php-ai-client/src/Providers/Models/SpeechGeneration/Contracts/SpeechGenerationModelInterface.php
new file mode 100644
index 0000000000000..6fbf222f90e0c
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Models/SpeechGeneration/Contracts/SpeechGenerationModelInterface.php
@@ -0,0 +1,26 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Models\SpeechGeneration\Contracts;
+
+use WordPress\AiClient\Messages\DTO\Message;
+use WordPress\AiClient\Results\DTO\GenerativeAiResult;
+/**
+ * Interface for models that support speech generation.
+ *
+ * Provides synchronous methods for generating speech from prompts.
+ *
+ * @since 0.1.0
+ */
+interface SpeechGenerationModelInterface
+{
+    /**
+     * Generates speech from a prompt.
+     *
+     * @since 0.1.0
+     *
+     * @param list<Message> $prompt Array of messages containing the speech generation prompt.
+     * @return GenerativeAiResult Result containing generated speech audio.
+     */
+    public function generateSpeechResult(array $prompt): GenerativeAiResult;
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Models/SpeechGeneration/Contracts/SpeechGenerationOperationModelInterface.php b/src/wp-includes/php-ai-client/src/Providers/Models/SpeechGeneration/Contracts/SpeechGenerationOperationModelInterface.php
new file mode 100644
index 0000000000000..55305e7a6e6d3
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Models/SpeechGeneration/Contracts/SpeechGenerationOperationModelInterface.php
@@ -0,0 +1,26 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Models\SpeechGeneration\Contracts;
+
+use WordPress\AiClient\Messages\DTO\Message;
+use WordPress\AiClient\Operations\DTO\GenerativeAiOperation;
+/**
+ * Interface for models that support asynchronous speech generation operations.
+ *
+ * Provides methods for initiating long-running speech generation tasks.
+ *
+ * @since 0.1.0
+ */
+interface SpeechGenerationOperationModelInterface
+{
+    /**
+     * Creates a speech generation operation.
+     *
+     * @since 0.1.0
+     *
+     * @param list<Message> $prompt Array of messages containing the speech generation prompt.
+     * @return GenerativeAiOperation The initiated speech generation operation.
+     */
+    public function generateSpeechOperation(array $prompt): GenerativeAiOperation;
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Models/TextGeneration/Contracts/TextGenerationModelInterface.php b/src/wp-includes/php-ai-client/src/Providers/Models/TextGeneration/Contracts/TextGenerationModelInterface.php
new file mode 100644
index 0000000000000..b455206e86f1a
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Models/TextGeneration/Contracts/TextGenerationModelInterface.php
@@ -0,0 +1,26 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Models\TextGeneration\Contracts;
+
+use WordPress\AiClient\Messages\DTO\Message;
+use WordPress\AiClient\Results\DTO\GenerativeAiResult;
+/**
+ * Interface for models that support text generation.
+ *
+ * Provides synchronous and streaming methods for generating text from prompts.
+ *
+ * @since 0.1.0
+ */
+interface TextGenerationModelInterface
+{
+    /**
+     * Generates text from a prompt.
+     *
+     * @since 0.1.0
+     *
+     * @param list<Message> $prompt Array of messages containing the text generation prompt.
+     * @return GenerativeAiResult Result containing generated text.
+     */
+    public function generateTextResult(array $prompt): GenerativeAiResult;
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Models/TextGeneration/Contracts/TextGenerationOperationModelInterface.php b/src/wp-includes/php-ai-client/src/Providers/Models/TextGeneration/Contracts/TextGenerationOperationModelInterface.php
new file mode 100644
index 0000000000000..a4ae0de91863f
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Models/TextGeneration/Contracts/TextGenerationOperationModelInterface.php
@@ -0,0 +1,26 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Models\TextGeneration\Contracts;
+
+use WordPress\AiClient\Messages\DTO\Message;
+use WordPress\AiClient\Operations\DTO\GenerativeAiOperation;
+/**
+ * Interface for models that support asynchronous text generation operations.
+ *
+ * Provides methods for initiating long-running text generation tasks.
+ *
+ * @since 0.1.0
+ */
+interface TextGenerationOperationModelInterface
+{
+    /**
+     * Creates a text generation operation.
+     *
+     * @since 0.1.0
+     *
+     * @param list<Message> $prompt Array of messages containing the text generation prompt.
+     * @return GenerativeAiOperation The initiated text generation operation.
+     */
+    public function generateTextOperation(array $prompt): GenerativeAiOperation;
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Models/TextToSpeechConversion/Contracts/TextToSpeechConversionModelInterface.php b/src/wp-includes/php-ai-client/src/Providers/Models/TextToSpeechConversion/Contracts/TextToSpeechConversionModelInterface.php
new file mode 100644
index 0000000000000..e97c580803642
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Models/TextToSpeechConversion/Contracts/TextToSpeechConversionModelInterface.php
@@ -0,0 +1,26 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Models\TextToSpeechConversion\Contracts;
+
+use WordPress\AiClient\Messages\DTO\Message;
+use WordPress\AiClient\Results\DTO\GenerativeAiResult;
+/**
+ * Interface for models that support text-to-speech conversion.
+ *
+ * Provides synchronous methods for converting text to speech audio.
+ *
+ * @since 0.1.0
+ */
+interface TextToSpeechConversionModelInterface
+{
+    /**
+     * Converts text to speech.
+     *
+     * @since 0.1.0
+     *
+     * @param list<Message> $prompt Array of messages containing the text to convert to speech.
+     * @return GenerativeAiResult Result containing generated speech audio.
+     */
+    public function convertTextToSpeechResult(array $prompt): GenerativeAiResult;
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/Models/TextToSpeechConversion/Contracts/TextToSpeechConversionOperationModelInterface.php b/src/wp-includes/php-ai-client/src/Providers/Models/TextToSpeechConversion/Contracts/TextToSpeechConversionOperationModelInterface.php
new file mode 100644
index 0000000000000..e048bf2a780aa
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/Models/TextToSpeechConversion/Contracts/TextToSpeechConversionOperationModelInterface.php
@@ -0,0 +1,26 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\Models\TextToSpeechConversion\Contracts;
+
+use WordPress\AiClient\Messages\DTO\Message;
+use WordPress\AiClient\Operations\DTO\GenerativeAiOperation;
+/**
+ * Interface for models that support asynchronous text-to-speech conversion operations.
+ *
+ * Provides methods for initiating long-running text-to-speech conversion tasks.
+ *
+ * @since 0.1.0
+ */
+interface TextToSpeechConversionOperationModelInterface
+{
+    /**
+     * Creates a text-to-speech conversion operation.
+     *
+     * @since 0.1.0
+     *
+     * @param list<Message> $prompt Array of messages containing the text to convert to speech.
+     * @return GenerativeAiOperation The initiated text-to-speech conversion operation.
+     */
+    public function convertTextToSpeechOperation(array $prompt): GenerativeAiOperation;
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/OpenAiCompatibleImplementation/AbstractOpenAiCompatibleImageGenerationModel.php b/src/wp-includes/php-ai-client/src/Providers/OpenAiCompatibleImplementation/AbstractOpenAiCompatibleImageGenerationModel.php
new file mode 100644
index 0000000000000..c0747093efadb
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/OpenAiCompatibleImplementation/AbstractOpenAiCompatibleImageGenerationModel.php
@@ -0,0 +1,298 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\OpenAiCompatibleImplementation;
+
+use WordPress\AiClient\Common\Exception\InvalidArgumentException;
+use WordPress\AiClient\Common\Exception\RuntimeException;
+use WordPress\AiClient\Files\DTO\File;
+use WordPress\AiClient\Files\Enums\MediaOrientationEnum;
+use WordPress\AiClient\Messages\DTO\Message;
+use WordPress\AiClient\Messages\DTO\MessagePart;
+use WordPress\AiClient\Messages\Enums\MessageRoleEnum;
+use WordPress\AiClient\Providers\ApiBasedImplementation\AbstractApiBasedModel;
+use WordPress\AiClient\Providers\Http\DTO\Request;
+use WordPress\AiClient\Providers\Http\DTO\Response;
+use WordPress\AiClient\Providers\Http\Enums\HttpMethodEnum;
+use WordPress\AiClient\Providers\Http\Exception\ResponseException;
+use WordPress\AiClient\Providers\Http\Util\ResponseUtil;
+use WordPress\AiClient\Providers\Models\ImageGeneration\Contracts\ImageGenerationModelInterface;
+use WordPress\AiClient\Results\DTO\Candidate;
+use WordPress\AiClient\Results\DTO\GenerativeAiResult;
+use WordPress\AiClient\Results\DTO\TokenUsage;
+use WordPress\AiClient\Results\Enums\FinishReasonEnum;
+/**
+ * Base class for an image generation model for providers that implement OpenAI's API format.
+ *
+ * This abstract class is designed to work with any AI provider that offers an OpenAI-compatible
+ * API endpoint for image generation, including but not limited to Anthropic, Google, and other
+ * providers that have adopted OpenAI's image generation API specification as a standard interface.
+ *
+ * @since 0.1.0
+ *
+ * @phpstan-type ImageGenerationParams array{
+ *     model: string,
+ *     prompt: string,
+ *     n?: int,
+ *     response_format?: string,
+ *     output_format?: string|null,
+ *     size?: string,
+ *     ...
+ * }
+ * @phpstan-type ChoiceData array{
+ *     url?: string,
+ *     b64_json?: string
+ * }
+ * @phpstan-type UsageData array{
+ *     input_tokens?: int,
+ *     output_tokens?: int,
+ *     total_tokens?: int
+ * }
+ * @phpstan-type ResponseData array{
+ *     id?: string,
+ *     data?: list<ChoiceData>,
+ *     usage?: UsageData
+ * }
+ */
+abstract class AbstractOpenAiCompatibleImageGenerationModel extends AbstractApiBasedModel implements ImageGenerationModelInterface
+{
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public function generateImageResult(array $prompt): GenerativeAiResult
+    {
+        $httpTransporter = $this->getHttpTransporter();
+        $params = $this->prepareGenerateImageParams($prompt);
+        $request = $this->createRequest(HttpMethodEnum::POST(), 'images/generations', ['Content-Type' => 'application/json'], $params);
+        // Add authentication credentials to the request.
+        $request = $this->getRequestAuthentication()->authenticateRequest($request);
+        // Send and process the request.
+        $response = $httpTransporter->send($request);
+        $this->throwIfNotSuccessful($response);
+        return $this->parseResponseToGenerativeAiResult($response, isset($params['output_format']) && is_string($params['output_format']) ? "image/{$params['output_format']}" : 'image/png');
+    }
+    /**
+     * Prepares the given prompt and the model configuration into parameters for the API request.
+     *
+     * @since 0.1.0
+     *
+     * @param list<Message> $prompt The prompt to generate an image for. Either a single message or a list of messages
+     *                              from a chat. However as of today, OpenAI compatible image generation endpoints only
+     *                              support a single user message.
+     * @return ImageGenerationParams The parameters for the API request.
+     */
+    protected function prepareGenerateImageParams(array $prompt): array
+    {
+        $config = $this->getConfig();
+        $params = ['model' => $this->metadata()->getId(), 'prompt' => $this->preparePromptParam($prompt)];
+        $candidateCount = $config->getCandidateCount();
+        if ($candidateCount !== null) {
+            $params['n'] = $candidateCount;
+        }
+        $outputFileType = $config->getOutputFileType();
+        if ($outputFileType !== null) {
+            $params['response_format'] = $outputFileType->isRemote() ? 'url' : 'b64_json';
+        } else {
+            // The 'response_format' parameter is required, so we default to 'b64_json' if not set.
+            $params['response_format'] = 'b64_json';
+        }
+        $outputMimeType = $config->getOutputMimeType();
+        if ($outputMimeType !== null) {
+            $params['output_format'] = preg_replace('/^image\//', '', $outputMimeType);
+        }
+        $outputMediaOrientation = $config->getOutputMediaOrientation();
+        $outputMediaAspectRatio = $config->getOutputMediaAspectRatio();
+        if ($outputMediaOrientation !== null || $outputMediaAspectRatio !== null) {
+            $params['size'] = $this->prepareSizeParam($outputMediaOrientation, $outputMediaAspectRatio);
+        }
+        /*
+         * Any custom options are added to the parameters as well.
+         * This allows developers to pass other options that may be more niche or not yet supported by the SDK.
+         */
+        $customOptions = $config->getCustomOptions();
+        foreach ($customOptions as $key => $value) {
+            if (isset($params[$key])) {
+                throw new InvalidArgumentException(sprintf('The custom option "%s" conflicts with an existing parameter.', $key));
+            }
+            $params[$key] = $value;
+        }
+        /** @var ImageGenerationParams $params */
+        return $params;
+    }
+    /**
+     * Prepares the prompt parameter for the API request.
+     *
+     * @since 0.1.0
+     *
+     * @param list<Message> $messages The messages to prepare. However as of today, OpenAI compatible image generation
+     *                                endpoints only support a single user message.
+     * @return string The prepared prompt parameter.
+     */
+    protected function preparePromptParam(array $messages): string
+    {
+        if (count($messages) !== 1) {
+            throw new InvalidArgumentException('The API requires a single user message as prompt.');
+        }
+        $message = $messages[0];
+        if (!$message->getRole()->isUser()) {
+            throw new InvalidArgumentException('The API requires a user message as prompt.');
+        }
+        $text = null;
+        foreach ($message->getParts() as $part) {
+            $text = $part->getText();
+            if ($text !== null) {
+                break;
+            }
+        }
+        if ($text === null) {
+            throw new InvalidArgumentException('The API requires a single text message part as prompt.');
+        }
+        return $text;
+    }
+    /**
+     * Prepares the size parameter for the API request.
+     *
+     * @since 0.1.0
+     *
+     * @param MediaOrientationEnum|null $orientation The desired media orientation.
+     * @param string|null $aspectRatio The desired media aspect ratio.
+     * @return string The prepared size parameter.
+     */
+    protected function prepareSizeParam(?MediaOrientationEnum $orientation, ?string $aspectRatio): string
+    {
+        // Use aspect ratio if set, as it is more specific.
+        if ($aspectRatio !== null) {
+            switch ($aspectRatio) {
+                case '1:1':
+                    return '1024x1024';
+                case '3:2':
+                    return '1536x1024';
+                case '7:4':
+                    return '1792x1024';
+                case '2:3':
+                    return '1024x1536';
+                case '4:7':
+                    return '1024x1792';
+                default:
+                    throw new InvalidArgumentException('The aspect ratio "' . $aspectRatio . '" is not supported.');
+            }
+        }
+        // This should always have a value, as the method is only called if at least one or the other is set.
+        if ($orientation !== null) {
+            if ($orientation->isLandscape()) {
+                return '1536x1024';
+            }
+            if ($orientation->isPortrait()) {
+                return '1024x1536';
+            }
+        }
+        return '1024x1024';
+    }
+    /**
+     * Creates a request object for the provider's API.
+     *
+     * Implementations should use $this->getRequestOptions() to attach any
+     * configured request options to the Request.
+     *
+     * @since 0.1.0
+     *
+     * @param HttpMethodEnum $method The HTTP method.
+     * @param string $path The API endpoint path, relative to the base URI.
+     * @param array<string, string|list<string>> $headers The request headers.
+     * @param string|array<string, mixed>|null $data The request data.
+     * @return Request The request object.
+     */
+    abstract protected function createRequest(HttpMethodEnum $method, string $path, array $headers = [], $data = null): Request;
+    /**
+     * Throws an exception if the response is not successful.
+     *
+     * @since 0.1.0
+     *
+     * @param Response $response The HTTP response to check.
+     * @throws ResponseException If the response is not successful.
+     */
+    protected function throwIfNotSuccessful(Response $response): void
+    {
+        /*
+         * While this method only calls the utility method, it's important to have it here as a protected method so
+         * that child classes can override it if needed.
+         */
+        ResponseUtil::throwIfNotSuccessful($response);
+    }
+    /**
+     * Parses the response from the API endpoint to a generative AI result.
+     *
+     * @since 0.1.0
+     *
+     * @param Response $response The response from the API endpoint.
+     * @param string   $expectedMimeType The expected MIME type the response is in.
+     * @return GenerativeAiResult The parsed generative AI result.
+     */
+    protected function parseResponseToGenerativeAiResult(Response $response, string $expectedMimeType = 'image/png'): GenerativeAiResult
+    {
+        /** @var ResponseData $responseData */
+        $responseData = $response->getData();
+        if (!isset($responseData['data']) || !$responseData['data']) {
+            throw ResponseException::fromMissingData($this->providerMetadata()->getName(), 'data');
+        }
+        if (!is_array($responseData['data'])) {
+            throw ResponseException::fromInvalidData($this->providerMetadata()->getName(), 'data', 'The value must be an array.');
+        }
+        $candidates = [];
+        foreach ($responseData['data'] as $index => $choiceData) {
+            if (!is_array($choiceData) || array_is_list($choiceData)) {
+                throw ResponseException::fromInvalidData($this->providerMetadata()->getName(), "data[{$index}]", 'The value must be an associative array.');
+            }
+            $candidates[] = $this->parseResponseChoiceToCandidate($choiceData, $index, $expectedMimeType);
+        }
+        $id = $this->getResultId($responseData);
+        if (isset($responseData['usage']) && is_array($responseData['usage'])) {
+            $usage = $responseData['usage'];
+            $tokenUsage = new TokenUsage($usage['input_tokens'] ?? 0, $usage['output_tokens'] ?? 0, $usage['total_tokens'] ?? 0);
+        } else {
+            $tokenUsage = new TokenUsage(0, 0, 0);
+        }
+        // Use any other data from the response as provider-specific response metadata.
+        $providerMetadata = $responseData;
+        unset($providerMetadata['id'], $providerMetadata['data'], $providerMetadata['usage']);
+        return new GenerativeAiResult($id, $candidates, $tokenUsage, $this->providerMetadata(), $this->metadata(), $providerMetadata);
+    }
+    /**
+     * Parses a single choice from the API response into a Candidate object.
+     *
+     * @since 0.1.0
+     *
+     * @param ChoiceData $choiceData The choice data from the API response.
+     * @param int $index The index of the choice in the choices array.
+     * @param string   $expectedMimeType The expected MIME type the response is in.
+     * @return Candidate The parsed candidate.
+     * @throws RuntimeException If the choice data is invalid.
+     */
+    protected function parseResponseChoiceToCandidate(array $choiceData, int $index, string $expectedMimeType = 'image/png'): Candidate
+    {
+        if (isset($choiceData['url']) && is_string($choiceData['url'])) {
+            $imageFile = new File($choiceData['url'], $expectedMimeType);
+        } elseif (isset($choiceData['b64_json']) && is_string($choiceData['b64_json'])) {
+            $imageFile = new File($choiceData['b64_json'], $expectedMimeType);
+        } else {
+            throw ResponseException::fromInvalidData($this->providerMetadata()->getName(), "choices[{$index}]", 'The value must contain either a url or b64_json key with a string value.');
+        }
+        $parts = [new MessagePart($imageFile)];
+        $message = new Message(MessageRoleEnum::model(), $parts);
+        return new Candidate($message, FinishReasonEnum::stop());
+    }
+    /**
+     * Extracts the result ID from the API response data.
+     *
+     * @since 0.4.0
+     *
+     * @param array<string, mixed> $responseData The response data from the API.
+     * @return string The result ID.
+     */
+    protected function getResultId(array $responseData): string
+    {
+        return isset($responseData['id']) && is_string($responseData['id']) ? $responseData['id'] : '';
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/OpenAiCompatibleImplementation/AbstractOpenAiCompatibleModelMetadataDirectory.php b/src/wp-includes/php-ai-client/src/Providers/OpenAiCompatibleImplementation/AbstractOpenAiCompatibleModelMetadataDirectory.php
new file mode 100644
index 0000000000000..cc5e0e9ab1df9
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/OpenAiCompatibleImplementation/AbstractOpenAiCompatibleModelMetadataDirectory.php
@@ -0,0 +1,80 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\OpenAiCompatibleImplementation;
+
+use WordPress\AiClient\Providers\ApiBasedImplementation\AbstractApiBasedModelMetadataDirectory;
+use WordPress\AiClient\Providers\Http\DTO\Request;
+use WordPress\AiClient\Providers\Http\DTO\Response;
+use WordPress\AiClient\Providers\Http\Enums\HttpMethodEnum;
+use WordPress\AiClient\Providers\Http\Exception\ResponseException;
+use WordPress\AiClient\Providers\Http\Util\ResponseUtil;
+use WordPress\AiClient\Providers\Models\DTO\ModelMetadata;
+/**
+ * Base class for a model metadata directory for providers that implement OpenAI's API format.
+ *
+ * This abstract class is designed to work with any AI provider that offers an OpenAI-compatible
+ * models listing endpoint, including but not limited to Anthropic, Google, and other
+ * providers that have adopted OpenAI's models API specification as a standard interface.
+ *
+ * @since 0.1.0
+ */
+abstract class AbstractOpenAiCompatibleModelMetadataDirectory extends AbstractApiBasedModelMetadataDirectory
+{
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    protected function sendListModelsRequest(): array
+    {
+        $httpTransporter = $this->getHttpTransporter();
+        $request = $this->createRequest(HttpMethodEnum::GET(), 'models');
+        $request = $this->getRequestAuthentication()->authenticateRequest($request);
+        $response = $httpTransporter->send($request);
+        $this->throwIfNotSuccessful($response);
+        $modelsMetadataList = $this->parseResponseToModelMetadataList($response);
+        $modelMetadataMap = [];
+        foreach ($modelsMetadataList as $modelMetadata) {
+            $modelMetadataMap[$modelMetadata->getId()] = $modelMetadata;
+        }
+        return $modelMetadataMap;
+    }
+    /**
+     * Creates a request object for the provider's API.
+     *
+     * @since 0.1.0
+     *
+     * @param HttpMethodEnum $method The HTTP method.
+     * @param string $path The API endpoint path, relative to the base URI.
+     * @param array<string, string|list<string>> $headers The request headers.
+     * @param string|array<string, mixed>|null $data The request data.
+     * @return Request The request object.
+     */
+    abstract protected function createRequest(HttpMethodEnum $method, string $path, array $headers = [], $data = null): Request;
+    /**
+     * Throws an exception if the response is not successful.
+     *
+     * @since 0.1.0
+     *
+     * @param Response $response The HTTP response to check.
+     * @throws ResponseException If the response is not successful.
+     */
+    protected function throwIfNotSuccessful(Response $response): void
+    {
+        /*
+         * While this method only calls the utility method, it's important to have it here as a protected method so
+         * that child classes can override it if needed.
+         */
+        ResponseUtil::throwIfNotSuccessful($response);
+    }
+    /**
+     * Parses the response from the API endpoint to list models into a list of model metadata objects.
+     *
+     * @since 0.1.0
+     *
+     * @param Response $response The response from the API endpoint to list models.
+     * @return list<ModelMetadata> List of model metadata objects.
+     */
+    abstract protected function parseResponseToModelMetadataList(Response $response): array;
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/OpenAiCompatibleImplementation/AbstractOpenAiCompatibleTextGenerationModel.php b/src/wp-includes/php-ai-client/src/Providers/OpenAiCompatibleImplementation/AbstractOpenAiCompatibleTextGenerationModel.php
new file mode 100644
index 0000000000000..adbbd5dad9f49
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/OpenAiCompatibleImplementation/AbstractOpenAiCompatibleTextGenerationModel.php
@@ -0,0 +1,557 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers\OpenAiCompatibleImplementation;
+
+use WordPress\AiClient\Common\Exception\InvalidArgumentException;
+use WordPress\AiClient\Common\Exception\RuntimeException;
+use WordPress\AiClient\Messages\DTO\Message;
+use WordPress\AiClient\Messages\DTO\MessagePart;
+use WordPress\AiClient\Messages\Enums\MessagePartChannelEnum;
+use WordPress\AiClient\Messages\Enums\MessageRoleEnum;
+use WordPress\AiClient\Messages\Enums\ModalityEnum;
+use WordPress\AiClient\Providers\ApiBasedImplementation\AbstractApiBasedModel;
+use WordPress\AiClient\Providers\Http\DTO\Request;
+use WordPress\AiClient\Providers\Http\DTO\Response;
+use WordPress\AiClient\Providers\Http\Enums\HttpMethodEnum;
+use WordPress\AiClient\Providers\Http\Exception\ResponseException;
+use WordPress\AiClient\Providers\Http\Util\ResponseUtil;
+use WordPress\AiClient\Providers\Models\TextGeneration\Contracts\TextGenerationModelInterface;
+use WordPress\AiClient\Results\DTO\Candidate;
+use WordPress\AiClient\Results\DTO\GenerativeAiResult;
+use WordPress\AiClient\Results\DTO\TokenUsage;
+use WordPress\AiClient\Results\Enums\FinishReasonEnum;
+use WordPress\AiClient\Tools\DTO\FunctionCall;
+use WordPress\AiClient\Tools\DTO\FunctionDeclaration;
+/**
+ * Base class for a text generation model for providers that implement OpenAI's API format.
+ *
+ * This abstract class is designed to work with any AI provider that offers an OpenAI-compatible
+ * API endpoint, including but not limited to Anthropic, Google, and other providers
+ * that have adopted OpenAI's API specification as a standard interface.
+ *
+ * @since 0.1.0
+ *
+ * @phpstan-type ToolCallData array{
+ *     type?: string,
+ *     id?: string,
+ *     function?: array{
+ *         name?: string,
+ *         arguments: string|array<string, mixed>
+ *     }
+ * }
+ * @phpstan-type MessageData array{
+ *     role?: string,
+ *     reasoning_content?: string,
+ *     content?: string,
+ *     tool_calls?: list<ToolCallData>
+ * }
+ * @phpstan-type ChoiceData array{
+ *     message?: MessageData,
+ *     finish_reason?: string
+ * }
+ * @phpstan-type UsageData array{
+ *     prompt_tokens?: int,
+ *     completion_tokens?: int,
+ *     total_tokens?: int
+ * }
+ * @phpstan-type ResponseData array{
+ *     id?: string,
+ *     choices?: list<ChoiceData>,
+ *     usage?: UsageData
+ * }
+ */
+abstract class AbstractOpenAiCompatibleTextGenerationModel extends AbstractApiBasedModel implements TextGenerationModelInterface
+{
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    final public function generateTextResult(array $prompt): GenerativeAiResult
+    {
+        $httpTransporter = $this->getHttpTransporter();
+        $params = $this->prepareGenerateTextParams($prompt);
+        $request = $this->createRequest(HttpMethodEnum::POST(), 'chat/completions', ['Content-Type' => 'application/json'], $params);
+        // Add authentication credentials to the request.
+        $request = $this->getRequestAuthentication()->authenticateRequest($request);
+        // Send and process the request.
+        $response = $httpTransporter->send($request);
+        $this->throwIfNotSuccessful($response);
+        return $this->parseResponseToGenerativeAiResult($response);
+    }
+    /**
+     * Prepares the given prompt and the model configuration into parameters for the API request.
+     *
+     * @since 0.1.0
+     *
+     * @param list<Message> $prompt The prompt to generate text for. Either a single message or a list of messages
+     *                              from a chat.
+     * @return array<string, mixed> The parameters for the API request.
+     */
+    protected function prepareGenerateTextParams(array $prompt): array
+    {
+        $config = $this->getConfig();
+        $params = ['model' => $this->metadata()->getId(), 'messages' => $this->prepareMessagesParam($prompt, $config->getSystemInstruction())];
+        $outputModalities = $config->getOutputModalities();
+        if (is_array($outputModalities)) {
+            $this->validateOutputModalities($outputModalities);
+            if (count($outputModalities) > 1) {
+                $params['modalities'] = $this->prepareOutputModalitiesParam($outputModalities);
+            }
+        }
+        $candidateCount = $config->getCandidateCount();
+        if ($candidateCount !== null) {
+            $params['n'] = $candidateCount;
+        }
+        $maxTokens = $config->getMaxTokens();
+        if ($maxTokens !== null) {
+            $params['max_tokens'] = $maxTokens;
+        }
+        $temperature = $config->getTemperature();
+        if ($temperature !== null) {
+            $params['temperature'] = $temperature;
+        }
+        $topP = $config->getTopP();
+        if ($topP !== null) {
+            $params['top_p'] = $topP;
+        }
+        $stopSequences = $config->getStopSequences();
+        if (is_array($stopSequences)) {
+            $params['stop'] = $stopSequences;
+        }
+        $presencePenalty = $config->getPresencePenalty();
+        if ($presencePenalty !== null) {
+            $params['presence_penalty'] = $presencePenalty;
+        }
+        $frequencyPenalty = $config->getFrequencyPenalty();
+        if ($frequencyPenalty !== null) {
+            $params['frequency_penalty'] = $frequencyPenalty;
+        }
+        $logprobs = $config->getLogprobs();
+        if ($logprobs !== null) {
+            $params['logprobs'] = $logprobs;
+        }
+        $topLogprobs = $config->getTopLogprobs();
+        if ($topLogprobs !== null) {
+            $params['top_logprobs'] = $topLogprobs;
+        }
+        $functionDeclarations = $config->getFunctionDeclarations();
+        if (is_array($functionDeclarations)) {
+            $params['tools'] = $this->prepareToolsParam($functionDeclarations);
+        }
+        $outputMimeType = $config->getOutputMimeType();
+        if ('application/json' === $outputMimeType) {
+            $outputSchema = $config->getOutputSchema();
+            $params['response_format'] = $this->prepareResponseFormatParam($outputSchema);
+        }
+        /*
+         * Any custom options are added to the parameters as well.
+         * This allows developers to pass other options that may be more niche or not yet supported by the SDK.
+         */
+        $customOptions = $config->getCustomOptions();
+        foreach ($customOptions as $key => $value) {
+            if (isset($params[$key])) {
+                throw new InvalidArgumentException(sprintf('The custom option "%s" conflicts with an existing parameter.', $key));
+            }
+            $params[$key] = $value;
+        }
+        return $params;
+    }
+    /**
+     * Prepares the messages parameter for the API request.
+     *
+     * @since 0.1.0
+     *
+     * @param list<Message> $messages The messages to prepare.
+     * @param string|null $systemInstruction An optional system instruction to prepend to the messages.
+     * @return list<array<string, mixed>> The prepared messages parameter.
+     */
+    protected function prepareMessagesParam(array $messages, ?string $systemInstruction = null): array
+    {
+        $messagesParam = array_map(function (Message $message): array {
+            // Special case: Function response.
+            $messageParts = $message->getParts();
+            if (count($messageParts) === 1 && $messageParts[0]->getType()->isFunctionResponse()) {
+                $functionResponse = $messageParts[0]->getFunctionResponse();
+                if (!$functionResponse) {
+                    // This should be impossible due to class internals, but still needs to be checked.
+                    throw new RuntimeException('The function response typed message part must contain a function response.');
+                }
+                return ['role' => 'tool', 'content' => json_encode($functionResponse->getResponse()), 'tool_call_id' => $functionResponse->getId()];
+            }
+            $messageData = ['role' => $this->getMessageRoleString($message->getRole()), 'content' => array_values(array_filter(array_map([$this, 'getMessagePartContentData'], $messageParts)))];
+            // Only include tool_calls if there are any (OpenAI rejects empty arrays).
+            $toolCalls = array_values(array_filter(array_map([$this, 'getMessagePartToolCallData'], $messageParts)));
+            if (!empty($toolCalls)) {
+                $messageData['tool_calls'] = $toolCalls;
+            }
+            return $messageData;
+        }, $messages);
+        if ($systemInstruction) {
+            array_unshift($messagesParam, [
+                /*
+                 * TODO: Replace this with 'developer' in the future.
+                 * See https://platform.openai.com/docs/api-reference/chat/create#chat_create-messages
+                 */
+                'role' => 'system',
+                'content' => [['type' => 'text', 'text' => $systemInstruction]],
+            ]);
+        }
+        return $messagesParam;
+    }
+    /**
+     * Returns the OpenAI API specific role string for the given message role.
+     *
+     * @since 0.1.0
+     *
+     * @param MessageRoleEnum $role The message role.
+     * @return string The role for the API request.
+     */
+    protected function getMessageRoleString(MessageRoleEnum $role): string
+    {
+        if ($role === MessageRoleEnum::model()) {
+            return 'assistant';
+        }
+        return 'user';
+    }
+    /**
+     * Returns the OpenAI API specific content data for a message part.
+     *
+     * @since 0.1.0
+     *
+     * @param MessagePart $part The message part to get the data for.
+     * @return ?array<string, mixed> The data for the message content part, or null if not applicable.
+     * @throws InvalidArgumentException If the message part type or data is unsupported.
+     */
+    protected function getMessagePartContentData(MessagePart $part): ?array
+    {
+        $type = $part->getType();
+        if ($type->isText()) {
+            /*
+             * The OpenAI Chat Completions API spec does not support annotating thought parts as input,
+             * so we instead skip them.
+             */
+            if ($part->getChannel()->isThought()) {
+                return null;
+            }
+            return ['type' => 'text', 'text' => $part->getText()];
+        }
+        if ($type->isFile()) {
+            $file = $part->getFile();
+            if (!$file) {
+                // This should be impossible due to class internals, but still needs to be checked.
+                throw new RuntimeException('The file typed message part must contain a file.');
+            }
+            if ($file->isRemote()) {
+                if ($file->isImage()) {
+                    return ['type' => 'image_url', 'image_url' => ['url' => $file->getUrl()]];
+                }
+                throw new InvalidArgumentException(sprintf('Unsupported MIME type "%s" for remote file message part.', $file->getMimeType()));
+            }
+            // Else, it is an inline file.
+            if ($file->isImage()) {
+                return ['type' => 'image_url', 'image_url' => ['url' => $file->getDataUri()]];
+            }
+            if ($file->isAudio()) {
+                return ['type' => 'input_audio', 'input_audio' => ['data' => $file->getBase64Data(), 'format' => $file->getMimeTypeObject()->toExtension()]];
+            }
+            throw new InvalidArgumentException(sprintf('Unsupported MIME type "%s" for inline file message part.', $file->getMimeType()));
+        }
+        if ($type->isFunctionCall()) {
+            // Skip, as this is separately included. See `getMessagePartToolCallData()`.
+            return null;
+        }
+        if ($type->isFunctionResponse()) {
+            // Special case: Function response.
+            throw new InvalidArgumentException('The API only allows a single function response, as the only content of the message.');
+        }
+        throw new InvalidArgumentException(sprintf('Unsupported message part type "%s".', $type));
+    }
+    /**
+     * Returns the OpenAI API specific tool calls data for a message part.
+     *
+     * @since 0.1.0
+     *
+     * @param MessagePart $part The message part to get the data for.
+     * @return ?array<string, mixed> The data for the message tool call part, or null if not applicable.
+     * @throws InvalidArgumentException If the message part type or data is unsupported.
+     */
+    protected function getMessagePartToolCallData(MessagePart $part): ?array
+    {
+        $type = $part->getType();
+        if ($type->isFunctionCall()) {
+            $functionCall = $part->getFunctionCall();
+            if (!$functionCall) {
+                // This should be impossible due to class internals, but still needs to be checked.
+                throw new RuntimeException('The function call typed message part must contain a function call.');
+            }
+            $args = $functionCall->getArgs();
+            /*
+             * Ensure null or empty arrays become empty objects for JSON encoding.
+             * While in theory the JSON schema could also dictate a type of
+             * 'array', in practice function arguments are typically of type
+             * 'object'. More importantly, the OpenAI API specification seems
+             * to expect that, and does not support passing arrays as the root
+             * value. The null check handles the case where FunctionCall normalizes
+             * empty arrays to null.
+             */
+            if ($args === null || is_array($args) && count($args) === 0) {
+                $args = new \stdClass();
+            }
+            return ['type' => 'function', 'id' => $functionCall->getId(), 'function' => ['name' => $functionCall->getName(), 'arguments' => json_encode($args)]];
+        }
+        // All other types are handled in `getMessagePartContentData()`.
+        return null;
+    }
+    /**
+     * Validates that the given output modalities to ensure that at least one output modality is text.
+     *
+     * @since 0.1.0
+     *
+     * @param array<ModalityEnum> $outputModalities The output modalities to validate.
+     * @throws InvalidArgumentException If no text output modality is present.
+     */
+    protected function validateOutputModalities(array $outputModalities): void
+    {
+        // If no output modalities are set, it's fine, as we can assume text.
+        if (count($outputModalities) === 0) {
+            return;
+        }
+        foreach ($outputModalities as $modality) {
+            if ($modality->isText()) {
+                return;
+            }
+        }
+        throw new InvalidArgumentException('A text output modality must be present when generating text.');
+    }
+    /**
+     * Prepares the output modalities parameter for the API request.
+     *
+     * @since 0.1.0
+     *
+     * @param array<ModalityEnum> $modalities The modalities to prepare.
+     * @return list<string> The prepared modalities parameter.
+     */
+    protected function prepareOutputModalitiesParam(array $modalities): array
+    {
+        $prepared = [];
+        foreach ($modalities as $modality) {
+            if ($modality->isText()) {
+                $prepared[] = 'text';
+            } elseif ($modality->isImage()) {
+                $prepared[] = 'image';
+            } elseif ($modality->isAudio()) {
+                $prepared[] = 'audio';
+            } else {
+                throw new InvalidArgumentException(sprintf('Unsupported output modality "%s".', $modality));
+            }
+        }
+        return $prepared;
+    }
+    /**
+     * Prepares the tools parameter for the API request.
+     *
+     * @since 0.1.0
+     *
+     * @param list<FunctionDeclaration> $functionDeclarations The function declarations.
+     * @return list<array<string, mixed>> The prepared tools parameter.
+     */
+    protected function prepareToolsParam(array $functionDeclarations): array
+    {
+        $tools = [];
+        foreach ($functionDeclarations as $functionDeclaration) {
+            $tools[] = ['type' => 'function', 'function' => $functionDeclaration->toArray()];
+        }
+        return $tools;
+    }
+    /**
+     * Prepares the response format parameter for the API request.
+     *
+     * This is only called if the output MIME type is `application/json`.
+     *
+     * @since 0.1.0
+     *
+     * @param array<string, mixed>|null $outputSchema The output schema.
+     * @return array<string, mixed> The prepared response format parameter.
+     */
+    protected function prepareResponseFormatParam(?array $outputSchema): array
+    {
+        if (is_array($outputSchema)) {
+            return ['type' => 'json_schema', 'json_schema' => $outputSchema];
+        }
+        return ['type' => 'json_object'];
+    }
+    /**
+     * Creates a request object for the provider's API.
+     *
+     * Implementations should use $this->getRequestOptions() to attach any
+     * configured request options to the Request.
+     *
+     * @since 0.1.0
+     *
+     * @param HttpMethodEnum $method The HTTP method.
+     * @param string $path The API endpoint path, relative to the base URI.
+     * @param array<string, string|list<string>> $headers The request headers.
+     * @param string|array<string, mixed>|null $data The request data.
+     * @return Request The request object.
+     */
+    abstract protected function createRequest(HttpMethodEnum $method, string $path, array $headers = [], $data = null): Request;
+    /**
+     * Throws an exception if the response is not successful.
+     *
+     * @since 0.1.0
+     *
+     * @param Response $response The HTTP response to check.
+     * @throws ResponseException If the response is not successful.
+     */
+    protected function throwIfNotSuccessful(Response $response): void
+    {
+        /*
+         * While this method only calls the utility method, it's important to have it here as a protected method so
+         * that child classes can override it if needed.
+         */
+        ResponseUtil::throwIfNotSuccessful($response);
+    }
+    /**
+     * Parses the response from the API endpoint to a generative AI result.
+     *
+     * @since 0.1.0
+     *
+     * @param Response $response The response from the API endpoint.
+     * @return GenerativeAiResult The parsed generative AI result.
+     */
+    protected function parseResponseToGenerativeAiResult(Response $response): GenerativeAiResult
+    {
+        /** @var ResponseData $responseData */
+        $responseData = $response->getData();
+        if (!isset($responseData['choices']) || !$responseData['choices']) {
+            throw ResponseException::fromMissingData($this->providerMetadata()->getName(), 'choices');
+        }
+        if (!is_array($responseData['choices'])) {
+            throw ResponseException::fromInvalidData($this->providerMetadata()->getName(), 'choices', 'The value must be an array.');
+        }
+        $candidates = [];
+        foreach ($responseData['choices'] as $index => $choiceData) {
+            if (!is_array($choiceData) || array_is_list($choiceData)) {
+                throw ResponseException::fromInvalidData($this->providerMetadata()->getName(), "choices[{$index}]", 'The value must be an associative array.');
+            }
+            $candidates[] = $this->parseResponseChoiceToCandidate($choiceData, $index);
+        }
+        $id = isset($responseData['id']) && is_string($responseData['id']) ? $responseData['id'] : '';
+        if (isset($responseData['usage']) && is_array($responseData['usage'])) {
+            $usage = $responseData['usage'];
+            $tokenUsage = new TokenUsage($usage['prompt_tokens'] ?? 0, $usage['completion_tokens'] ?? 0, $usage['total_tokens'] ?? 0);
+        } else {
+            $tokenUsage = new TokenUsage(0, 0, 0);
+        }
+        // Use any other data from the response as provider-specific response metadata.
+        $additionalData = $responseData;
+        unset($additionalData['id'], $additionalData['choices'], $additionalData['usage']);
+        return new GenerativeAiResult($id, $candidates, $tokenUsage, $this->providerMetadata(), $this->metadata(), $additionalData);
+    }
+    /**
+     * Parses a single choice from the API response into a Candidate object.
+     *
+     * @since 0.1.0
+     *
+     * @param ChoiceData $choiceData The choice data from the API response.
+     * @param int $index The index of the choice in the choices array.
+     * @return Candidate The parsed candidate.
+     * @throws RuntimeException If the choice data is invalid.
+     */
+    protected function parseResponseChoiceToCandidate(array $choiceData, int $index): Candidate
+    {
+        if (!isset($choiceData['message']) || !is_array($choiceData['message']) || array_is_list($choiceData['message'])) {
+            throw ResponseException::fromMissingData($this->providerMetadata()->getName(), "choices[{$index}].message");
+        }
+        if (!isset($choiceData['finish_reason']) || !is_string($choiceData['finish_reason'])) {
+            throw ResponseException::fromMissingData($this->providerMetadata()->getName(), "choices[{$index}].finish_reason");
+        }
+        $messageData = $choiceData['message'];
+        $message = $this->parseResponseChoiceMessage($messageData, $index);
+        switch ($choiceData['finish_reason']) {
+            case 'stop':
+                $finishReason = FinishReasonEnum::stop();
+                break;
+            case 'length':
+                $finishReason = FinishReasonEnum::length();
+                break;
+            case 'content_filter':
+                $finishReason = FinishReasonEnum::contentFilter();
+                break;
+            case 'tool_calls':
+                $finishReason = FinishReasonEnum::toolCalls();
+                break;
+            default:
+                throw ResponseException::fromInvalidData($this->providerMetadata()->getName(), "choices[{$index}].finish_reason", sprintf('Invalid finish reason "%s".', $choiceData['finish_reason']));
+        }
+        return new Candidate($message, $finishReason);
+    }
+    /**
+     * Parses the message from a choice in the API response.
+     *
+     * @since 0.1.0
+     *
+     * @param MessageData $messageData The message data from the API response.
+     * @param int $index The index of the choice in the choices array.
+     * @return Message The parsed message.
+     */
+    protected function parseResponseChoiceMessage(array $messageData, int $index): Message
+    {
+        $role = isset($messageData['role']) && 'user' === $messageData['role'] ? MessageRoleEnum::user() : MessageRoleEnum::model();
+        $parts = $this->parseResponseChoiceMessageParts($messageData, $index);
+        return new Message($role, $parts);
+    }
+    /**
+     * Parses the message parts from a choice in the API response.
+     *
+     * @since 0.1.0
+     *
+     * @param MessageData $messageData The message data from the API response.
+     * @param int $index The index of the choice in the choices array.
+     * @return MessagePart[] The parsed message parts.
+     */
+    protected function parseResponseChoiceMessageParts(array $messageData, int $index): array
+    {
+        $parts = [];
+        if (isset($messageData['reasoning_content']) && is_string($messageData['reasoning_content'])) {
+            $parts[] = new MessagePart($messageData['reasoning_content'], MessagePartChannelEnum::thought());
+        }
+        if (isset($messageData['content']) && is_string($messageData['content'])) {
+            $parts[] = new MessagePart($messageData['content']);
+        }
+        if (isset($messageData['tool_calls']) && is_array($messageData['tool_calls'])) {
+            foreach ($messageData['tool_calls'] as $toolCallIndex => $toolCallData) {
+                $toolCallPart = $this->parseResponseChoiceMessageToolCallPart($toolCallData);
+                if (!$toolCallPart) {
+                    throw ResponseException::fromInvalidData($this->providerMetadata()->getName(), "choices[{$index}].message.tool_calls[{$toolCallIndex}]", 'The response includes a tool call of an unexpected type.');
+                }
+                $parts[] = $toolCallPart;
+            }
+        }
+        return $parts;
+    }
+    /**
+     * Parses a tool call part from the API response.
+     *
+     * @since 0.1.0
+     *
+     * @param ToolCallData $toolCallData The tool call data from the API response.
+     * @return MessagePart|null The parsed message part for the tool call, or null if not applicable.
+     */
+    protected function parseResponseChoiceMessageToolCallPart(array $toolCallData): ?MessagePart
+    {
+        /*
+         * For now, only function calls are supported.
+         *
+         * Not all OpenAI compatible APIs include a 'type' key, so we only check its value if it is set.
+         */
+        if (isset($toolCallData['type']) && 'function' !== $toolCallData['type'] || !isset($toolCallData['function']) || !is_array($toolCallData['function'])) {
+            return null;
+        }
+        $functionArguments = is_string($toolCallData['function']['arguments']) ? json_decode($toolCallData['function']['arguments'], \true) : $toolCallData['function']['arguments'];
+        $functionCall = new FunctionCall(isset($toolCallData['id']) && is_string($toolCallData['id']) ? $toolCallData['id'] : null, isset($toolCallData['function']['name']) && is_string($toolCallData['function']['name']) ? $toolCallData['function']['name'] : null, $functionArguments);
+        return new MessagePart($functionCall);
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Providers/ProviderRegistry.php b/src/wp-includes/php-ai-client/src/Providers/ProviderRegistry.php
new file mode 100644
index 0000000000000..107e303af33f7
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Providers/ProviderRegistry.php
@@ -0,0 +1,520 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Providers;
+
+use WordPress\AiClientDependencies\Http\Discovery\Exception\NotFoundException as DiscoveryNotFoundException;
+use WordPress\AiClient\Common\Exception\InvalidArgumentException;
+use WordPress\AiClient\Common\Exception\RuntimeException;
+use WordPress\AiClient\Providers\Contracts\ProviderInterface;
+use WordPress\AiClient\Providers\Contracts\ProviderWithOperationsHandlerInterface;
+use WordPress\AiClient\Providers\DTO\ProviderMetadata;
+use WordPress\AiClient\Providers\DTO\ProviderModelsMetadata;
+use WordPress\AiClient\Providers\Http\Contracts\HttpTransporterInterface;
+use WordPress\AiClient\Providers\Http\Contracts\RequestAuthenticationInterface;
+use WordPress\AiClient\Providers\Http\Contracts\WithHttpTransporterInterface;
+use WordPress\AiClient\Providers\Http\Contracts\WithRequestAuthenticationInterface;
+use WordPress\AiClient\Providers\Http\HttpTransporterFactory;
+use WordPress\AiClient\Providers\Http\Traits\WithHttpTransporterTrait;
+use WordPress\AiClient\Providers\Models\Contracts\ModelInterface;
+use WordPress\AiClient\Providers\Models\DTO\ModelConfig;
+use WordPress\AiClient\Providers\Models\DTO\ModelMetadata;
+use WordPress\AiClient\Providers\Models\DTO\ModelRequirements;
+/**
+ * Registry for managing AI providers and their models.
+ *
+ * This class provides a centralized way to register AI providers, discover
+ * their capabilities, and find suitable models based on requirements.
+ *
+ * @since 0.1.0
+ */
+class ProviderRegistry implements WithHttpTransporterInterface
+{
+    use WithHttpTransporterTrait {
+        setHttpTransporter as setHttpTransporterOriginal;
+    }
+    /**
+     * @var array<string, class-string<ProviderInterface>> Mapping of provider IDs to class names.
+     */
+    private array $registeredIdsToClassNames = [];
+    /**
+     * @var array<class-string<ProviderInterface>, string> Mapping of provider class names to IDs.
+     */
+    private array $registeredClassNamesToIds = [];
+    /**
+     * @var array<class-string<ProviderInterface>, RequestAuthenticationInterface> Mapping of provider class names to
+     *                                                                             authentication instances.
+     */
+    private array $providerAuthenticationInstances = [];
+    /**
+     * Registers a provider class with the registry.
+     *
+     * @since 0.1.0
+     *
+     * @param class-string<ProviderInterface> $className The fully qualified provider class name implementing the
+     * ProviderInterface
+     * @throws InvalidArgumentException If the class doesn't exist or implement the required interface.
+     */
+    public function registerProvider(string $className): void
+    {
+        if (!class_exists($className)) {
+            throw new InvalidArgumentException(sprintf('Provider class does not exist: %s', $className));
+        }
+        // Validate that class implements ProviderInterface
+        if (!is_subclass_of($className, ProviderInterface::class)) {
+            throw new InvalidArgumentException(sprintf('Provider class must implement %s: %s', ProviderInterface::class, $className));
+        }
+        $metadata = $className::metadata();
+        if (!$metadata instanceof ProviderMetadata) {
+            throw new InvalidArgumentException(sprintf('Provider must return ProviderMetadata from metadata() method: %s', $className));
+        }
+        // If there is already a HTTP transporter instance set, hook it up to the provider as needed.
+        try {
+            $httpTransporter = $this->getHttpTransporter();
+        } catch (RuntimeException $e) {
+            /*
+             * If this fails, it's okay. There is no defined sequence between setting the HTTP transporter in the
+             * registry and registering providers in it, so it might be that the transporter is set later. It will be
+             * hooked up then.
+             * But for now we can ignore this exception and attempt to set the default HTTP transporter, if possible.
+             */
+            try {
+                $this->setHttpTransporter(HttpTransporterFactory::createTransporter());
+                $httpTransporter = $this->getHttpTransporter();
+            } catch (DiscoveryNotFoundException $e) {
+                /*
+                 * If no HTTP client implementation can be discovered yet, we can ignore this for now.
+                 * It might be set later, so it's not a hard error at this point.
+                 * We'll try again the next time a provider is registered, or maybe by that time an explicit
+                 * HTTP transporter will have been set.
+                 */
+            }
+        }
+        if (isset($httpTransporter)) {
+            $this->setHttpTransporterForProvider($className, $httpTransporter);
+        }
+        // Hook up the request authentication instance, using a default if not set.
+        if (!isset($this->providerAuthenticationInstances[$className])) {
+            $defaultProviderAuthentication = $this->createDefaultProviderRequestAuthentication($className);
+            if ($defaultProviderAuthentication !== null) {
+                $this->providerAuthenticationInstances[$className] = $defaultProviderAuthentication;
+            }
+        }
+        if (isset($this->providerAuthenticationInstances[$className])) {
+            $this->setRequestAuthenticationForProvider($className, $this->providerAuthenticationInstances[$className]);
+        }
+        $this->registeredIdsToClassNames[$metadata->getId()] = $className;
+        $this->registeredClassNamesToIds[$className] = $metadata->getId();
+    }
+    /**
+     * Gets a list of all registered provider IDs.
+     *
+     * @since 0.1.0
+     *
+     * @return list<string> List of registered provider IDs.
+     */
+    public function getRegisteredProviderIds(): array
+    {
+        return array_keys($this->registeredIdsToClassNames);
+    }
+    /**
+     * Checks if a provider is registered.
+     *
+     * @since 0.1.0
+     *
+     * @param string|class-string<ProviderInterface> $idOrClassName The provider ID or class name to check.
+     * @return bool True if the provider is registered.
+     */
+    public function hasProvider(string $idOrClassName): bool
+    {
+        return $this->isRegisteredId($idOrClassName) || $this->isRegisteredClassName($idOrClassName);
+    }
+    /**
+     * Gets the class name for a registered provider.
+     *
+     * @since 0.1.0
+     *
+     * @param string|class-string<ProviderInterface> $idOrClassName The provider ID or class name.
+     * @return class-string<ProviderInterface> The provider class name.
+     * @throws InvalidArgumentException If the provider is not registered.
+     */
+    public function getProviderClassName(string $idOrClassName): string
+    {
+        // If it's already a class name, return it
+        if ($this->isRegisteredClassName($idOrClassName)) {
+            return $idOrClassName;
+        }
+        // If it's a registered ID, return its class name
+        if ($this->isRegisteredId($idOrClassName)) {
+            return $this->registeredIdsToClassNames[$idOrClassName];
+        }
+        // Not found
+        throw new InvalidArgumentException(sprintf('Provider not registered: %s', $idOrClassName));
+    }
+    /**
+     * Gets the provider ID for a registered provider.
+     *
+     * @since 0.2.0
+     *
+     * @param string|class-string<ProviderInterface> $idOrClassName The provider ID or class name.
+     * @return string The provider ID.
+     * @throws InvalidArgumentException If the provider is not registered.
+     */
+    public function getProviderId(string $idOrClassName): string
+    {
+        // If it's already an ID, return it
+        if ($this->isRegisteredId($idOrClassName)) {
+            return $idOrClassName;
+        }
+        // If it's a registered class name, return its ID
+        if ($this->isRegisteredClassName($idOrClassName)) {
+            return $this->registeredClassNamesToIds[$idOrClassName];
+        }
+        // Not found
+        throw new InvalidArgumentException(sprintf('Provider not registered: %s', $idOrClassName));
+    }
+    /**
+     * Checks if a provider is properly configured.
+     *
+     * @since 0.1.0
+     *
+     * @param string|class-string<ProviderInterface> $idOrClassName The provider ID or class name.
+     * @return bool True if the provider is configured and ready to use.
+     */
+    public function isProviderConfigured(string $idOrClassName): bool
+    {
+        try {
+            $className = $this->resolveProviderClassName($idOrClassName);
+            // Use static method from ProviderInterface
+            /** @var class-string<ProviderInterface> $className */
+            $availability = $className::availability();
+            return $availability->isConfigured();
+        } catch (InvalidArgumentException $e) {
+            return \false;
+        }
+    }
+    /**
+     * Finds models across all available providers that support the given requirements.
+     *
+     * @since 0.1.0
+     *
+     * @param ModelRequirements $modelRequirements The requirements to match against.
+     * @return list<ProviderModelsMetadata> List of provider models metadata that match requirements.
+     */
+    public function findModelsMetadataForSupport(ModelRequirements $modelRequirements): array
+    {
+        $results = [];
+        foreach ($this->registeredIdsToClassNames as $providerId => $className) {
+            $providerResults = $this->findProviderModelsMetadataForSupport($providerId, $modelRequirements);
+            if (!empty($providerResults)) {
+                // Use static method from ProviderInterface
+                /** @var class-string<ProviderInterface> $className */
+                $providerMetadata = $className::metadata();
+                $results[] = new ProviderModelsMetadata($providerMetadata, $providerResults);
+            }
+        }
+        return $results;
+    }
+    /**
+     * Finds models within a specific available provider that support the given requirements.
+     *
+     * @since 0.1.0
+     *
+     * @param string $idOrClassName The provider ID or class name.
+     * @param ModelRequirements $modelRequirements The requirements to match against.
+     * @return list<ModelMetadata> List of model metadata that match requirements.
+     */
+    public function findProviderModelsMetadataForSupport(string $idOrClassName, ModelRequirements $modelRequirements): array
+    {
+        $className = $this->resolveProviderClassName($idOrClassName);
+        // If the provider is not configured, there is no way to use it, so it is considered unavailable.
+        if (!$this->isProviderConfigured($className)) {
+            return [];
+        }
+        $modelMetadataDirectory = $className::modelMetadataDirectory();
+        // Filter models that meet requirements
+        $matchingModels = [];
+        foreach ($modelMetadataDirectory->listModelMetadata() as $modelMetadata) {
+            if ($modelRequirements->areMetBy($modelMetadata)) {
+                $matchingModels[] = $modelMetadata;
+            }
+        }
+        return $matchingModels;
+    }
+    /**
+     * Gets a configured model instance from a provider.
+     *
+     * @since 0.1.0
+     *
+     * @param string|class-string<ProviderInterface> $idOrClassName The provider ID or class name.
+     * @param string $modelId The model identifier.
+     * @param ModelConfig|null $modelConfig The model configuration.
+     * @return ModelInterface The configured model instance.
+     * @throws InvalidArgumentException If provider or model is not found.
+     */
+    public function getProviderModel(string $idOrClassName, string $modelId, ?ModelConfig $modelConfig = null): ModelInterface
+    {
+        $className = $this->resolveProviderClassName($idOrClassName);
+        $modelInstance = $className::model($modelId, $modelConfig);
+        $this->bindModelDependencies($modelInstance);
+        return $modelInstance;
+    }
+    /**
+     * Binds dependencies to a model instance.
+     *
+     * This method injects required dependencies such as HTTP transporter
+     * and authentication into model instances that need them.
+     *
+     * @since 0.1.0
+     *
+     * @param ModelInterface $modelInstance The model instance to bind dependencies to.
+     * @return void
+     */
+    public function bindModelDependencies(ModelInterface $modelInstance): void
+    {
+        $className = $this->resolveProviderClassName($modelInstance->providerMetadata()->getId());
+        if ($modelInstance instanceof WithHttpTransporterInterface) {
+            $modelInstance->setHttpTransporter($this->getHttpTransporter());
+        }
+        if ($modelInstance instanceof WithRequestAuthenticationInterface) {
+            $requestAuthentication = $this->getProviderRequestAuthentication($className);
+            if ($requestAuthentication !== null) {
+                $modelInstance->setRequestAuthentication($requestAuthentication);
+            }
+        }
+    }
+    /**
+     * Gets the class name for a registered provider (handles both ID and class name input).
+     *
+     * @param string|class-string<ProviderInterface> $idOrClassName The provider ID or class name.
+     * @return class-string<ProviderInterface> The provider class name.
+     * @throws InvalidArgumentException If provider is not registered.
+     */
+    private function resolveProviderClassName(string $idOrClassName): string
+    {
+        // If it's already a class name, return it
+        if ($this->isRegisteredClassName($idOrClassName)) {
+            return $idOrClassName;
+        }
+        // If it's a registered ID, return its class name
+        if ($this->isRegisteredId($idOrClassName)) {
+            return $this->registeredIdsToClassNames[$idOrClassName];
+        }
+        // Not found
+        throw new InvalidArgumentException(sprintf('Provider not registered: %s', $idOrClassName));
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public function setHttpTransporter(HttpTransporterInterface $httpTransporter): void
+    {
+        $this->setHttpTransporterOriginal($httpTransporter);
+        // Make sure all registered providers have the HTTP transporter hooked up as needed.
+        foreach ($this->registeredIdsToClassNames as $className) {
+            $this->setHttpTransporterForProvider($className, $httpTransporter);
+        }
+    }
+    /**
+     * Sets the request authentication instance for the given provider.
+     *
+     * @since 0.1.0
+     *
+     * @param string|class-string<ProviderInterface> $idOrClassName The provider ID or class name.
+     * @param RequestAuthenticationInterface $requestAuthentication The request authentication instance.
+     */
+    public function setProviderRequestAuthentication(string $idOrClassName, RequestAuthenticationInterface $requestAuthentication): void
+    {
+        $className = $this->resolveProviderClassName($idOrClassName);
+        $this->providerAuthenticationInstances[$className] = $requestAuthentication;
+        $this->setRequestAuthenticationForProvider($className, $requestAuthentication);
+    }
+    /**
+     * Gets the request authentication instance for the given provider, if set.
+     *
+     * @since 0.1.0
+     *
+     * @param string|class-string<ProviderInterface> $idOrClassName The provider ID or class name.
+     * @return ?RequestAuthenticationInterface The request authentication instance, or null if not set.
+     */
+    public function getProviderRequestAuthentication(string $idOrClassName): ?RequestAuthenticationInterface
+    {
+        $className = $this->resolveProviderClassName($idOrClassName);
+        if (!isset($this->providerAuthenticationInstances[$className])) {
+            return null;
+        }
+        return $this->providerAuthenticationInstances[$className];
+    }
+    /**
+     * Sets the HTTP transporter for a specific provider, hooking up its class instances.
+     *
+     * @since 0.1.0
+     *
+     * @param class-string<ProviderInterface> $className The provider class name.
+     * @param HttpTransporterInterface $httpTransporter The HTTP transporter instance.
+     */
+    private function setHttpTransporterForProvider(string $className, HttpTransporterInterface $httpTransporter): void
+    {
+        $availability = $className::availability();
+        if ($availability instanceof WithHttpTransporterInterface) {
+            $availability->setHttpTransporter($httpTransporter);
+        }
+        $modelMetadataDirectory = $className::modelMetadataDirectory();
+        if ($modelMetadataDirectory instanceof WithHttpTransporterInterface) {
+            $modelMetadataDirectory->setHttpTransporter($httpTransporter);
+        }
+        if (is_subclass_of($className, ProviderWithOperationsHandlerInterface::class)) {
+            $operationsHandler = $className::operationsHandler();
+            if ($operationsHandler instanceof WithHttpTransporterInterface) {
+                $operationsHandler->setHttpTransporter($httpTransporter);
+            }
+        }
+    }
+    /**
+     * Sets the request authentication for a specific provider, hooking up its class instances.
+     *
+     * @since 0.1.0
+     *
+     * @param class-string<ProviderInterface> $className The provider class name.
+     * @param RequestAuthenticationInterface $requestAuthentication The authentication instance.
+     *
+     * @throws InvalidArgumentException If the authentication instance is not of the expected type.
+     */
+    private function setRequestAuthenticationForProvider(string $className, RequestAuthenticationInterface $requestAuthentication): void
+    {
+        $authenticationMethod = $className::metadata()->getAuthenticationMethod();
+        if ($authenticationMethod === null) {
+            throw new InvalidArgumentException(sprintf('Provider %s does not expect any authentication, but got %s.', $className, get_class($requestAuthentication)));
+        }
+        $expectedClass = $authenticationMethod->getImplementationClass();
+        if (!$requestAuthentication instanceof $expectedClass) {
+            throw new InvalidArgumentException(sprintf('Provider %s expects authentication of type %s, but got %s.', $className, $expectedClass, get_class($requestAuthentication)));
+        }
+        $availability = $className::availability();
+        if ($availability instanceof WithRequestAuthenticationInterface) {
+            $availability->setRequestAuthentication($requestAuthentication);
+        }
+        $modelMetadataDirectory = $className::modelMetadataDirectory();
+        if ($modelMetadataDirectory instanceof WithRequestAuthenticationInterface) {
+            $modelMetadataDirectory->setRequestAuthentication($requestAuthentication);
+        }
+        if (is_subclass_of($className, ProviderWithOperationsHandlerInterface::class)) {
+            $operationsHandler = $className::operationsHandler();
+            if ($operationsHandler instanceof WithRequestAuthenticationInterface) {
+                $operationsHandler->setRequestAuthentication($requestAuthentication);
+            }
+        }
+    }
+    /**
+     * Creates a default request authentication instance for a provider.
+     *
+     * @since 0.1.0
+     *
+     * @param class-string<ProviderInterface> $className The provider class name.
+     * @return ?RequestAuthenticationInterface The default request authentication instance, or null if not required or
+     *                                         if no credential data can be found.
+     */
+    private function createDefaultProviderRequestAuthentication(string $className): ?RequestAuthenticationInterface
+    {
+        $providerMetadata = $className::metadata();
+        $providerId = $providerMetadata->getId();
+        $authenticationMethod = $providerMetadata->getAuthenticationMethod();
+        if ($authenticationMethod === null) {
+            return null;
+        }
+        $authenticationClass = $authenticationMethod->getImplementationClass();
+        if ($authenticationClass === null) {
+            return null;
+        }
+        $authenticationSchema = $authenticationClass::getJsonSchema();
+        // Iterate over all JSON schema object properties to try to determine the necessary authentication data.
+        $authenticationData = [];
+        if (isset($authenticationSchema['properties']) && is_array($authenticationSchema['properties'])) {
+            /** @var array<string, mixed> $details */
+            foreach ($authenticationSchema['properties'] as $property => $details) {
+                $envVarName = $this->getEnvVarName($providerId, $property);
+                // Try to get the value from environment variable or constant.
+                $envValue = getenv($envVarName);
+                if ($envValue === \false) {
+                    if (!defined($envVarName)) {
+                        continue;
+                        // Skip if neither environment variable nor constant is defined.
+                    }
+                    $envValue = constant($envVarName);
+                    if (!is_scalar($envValue)) {
+                        continue;
+                    }
+                }
+                if (isset($details['type'])) {
+                    switch ($details['type']) {
+                        case 'boolean':
+                            $authenticationData[$property] = filter_var($envValue, \FILTER_VALIDATE_BOOLEAN);
+                            break;
+                        case 'number':
+                            $authenticationData[$property] = (int) $envValue;
+                            break;
+                        case 'string':
+                        default:
+                            $authenticationData[$property] = (string) $envValue;
+                    }
+                } else {
+                    // Default to string if no type is specified.
+                    $authenticationData[$property] = (string) $envValue;
+                }
+            }
+            // If any required fields are missing, return null to avoid immediate errors.
+            if (isset($authenticationSchema['required']) && is_array($authenticationSchema['required'])) {
+                /** @var list<string> $requiredProperties */
+                $requiredProperties = $authenticationSchema['required'];
+                if (array_diff_key(array_flip($requiredProperties), $authenticationData)) {
+                    return null;
+                }
+            }
+        }
+        /** @var RequestAuthenticationInterface */
+        /** @var array<string, mixed> $authenticationData */
+        return $authenticationClass::fromArray($authenticationData);
+    }
+    /**
+     * Checks if the given value is a registered provider class name.
+     *
+     * @since 0.4.0
+     *
+     * @param string $idOrClassName The value to check.
+     * @return bool True if it's a registered class name.
+     * @phpstan-assert-if-true class-string<ProviderInterface> $idOrClassName
+     */
+    private function isRegisteredClassName(string $idOrClassName): bool
+    {
+        return isset($this->registeredClassNamesToIds[$idOrClassName]);
+    }
+    /**
+     * Checks if the given value is a registered provider ID.
+     *
+     * @since 0.4.0
+     *
+     * @param string $idOrClassName The value to check.
+     * @return bool True if it's a registered provider ID.
+     */
+    private function isRegisteredId(string $idOrClassName): bool
+    {
+        return isset($this->registeredIdsToClassNames[$idOrClassName]);
+    }
+    /**
+     * Converts a provider ID and field name to a constant case environment variable name.
+     *
+     * @since 0.1.0
+     *
+     * @param string $providerId The provider ID.
+     * @param string $field The field name.
+     * @return string The environment variable name in CONSTANT_CASE.
+     */
+    private function getEnvVarName(string $providerId, string $field): string
+    {
+        // Convert camelCase or kebab-case or snake_case to CONSTANT_CASE.
+        $constantCaseProviderId = strtoupper((string) preg_replace('/([a-z])([A-Z])/', '$1_$2', str_replace('-', '_', $providerId)));
+        $constantCaseField = strtoupper((string) preg_replace('/([a-z])([A-Z])/', '$1_$2', str_replace('-', '_', $field)));
+        return "{$constantCaseProviderId}_{$constantCaseField}";
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Results/Contracts/ResultInterface.php b/src/wp-includes/php-ai-client/src/Results/Contracts/ResultInterface.php
new file mode 100644
index 0000000000000..5a087ca8b3fbe
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Results/Contracts/ResultInterface.php
@@ -0,0 +1,59 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Results\Contracts;
+
+use WordPress\AiClient\Providers\DTO\ProviderMetadata;
+use WordPress\AiClient\Providers\Models\DTO\ModelMetadata;
+use WordPress\AiClient\Results\DTO\TokenUsage;
+/**
+ * Interface for AI operation results.
+ *
+ * Results contain the output from AI operations along with metadata
+ * such as token usage and provider-specific information.
+ *
+ * @since 0.1.0
+ */
+interface ResultInterface
+{
+    /**
+     * Gets the result ID.
+     *
+     * @since 0.1.0
+     *
+     * @return string The unique result identifier.
+     */
+    public function getId(): string;
+    /**
+     * Gets token usage information.
+     *
+     * @since 0.1.0
+     *
+     * @return TokenUsage Token usage statistics.
+     */
+    public function getTokenUsage(): TokenUsage;
+    /**
+     * Gets the provider metadata.
+     *
+     * @since 0.1.0
+     *
+     * @return ProviderMetadata The provider metadata.
+     */
+    public function getProviderMetadata(): ProviderMetadata;
+    /**
+     * Gets the model metadata.
+     *
+     * @since 0.1.0
+     *
+     * @return ModelMetadata The model metadata.
+     */
+    public function getModelMetadata(): ModelMetadata;
+    /**
+     * Gets provider-specific metadata.
+     *
+     * @since 0.1.0
+     *
+     * @return array<string, mixed> Provider metadata.
+     */
+    public function getAdditionalData(): array;
+}
diff --git a/src/wp-includes/php-ai-client/src/Results/DTO/Candidate.php b/src/wp-includes/php-ai-client/src/Results/DTO/Candidate.php
new file mode 100644
index 0000000000000..d1bf7e0782985
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Results/DTO/Candidate.php
@@ -0,0 +1,117 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Results\DTO;
+
+use WordPress\AiClient\Common\AbstractDataTransferObject;
+use WordPress\AiClient\Common\Exception\InvalidArgumentException;
+use WordPress\AiClient\Messages\DTO\Message;
+use WordPress\AiClient\Results\Enums\FinishReasonEnum;
+/**
+ * Represents a candidate response from an AI model.
+ *
+ * When generating content, AI models can produce multiple candidates.
+ * Each candidate contains a message and metadata about why generation stopped.
+ *
+ * @since 0.1.0
+ *
+ * @phpstan-import-type MessageArrayShape from Message
+ *
+ * @phpstan-type CandidateArrayShape array{message: MessageArrayShape, finishReason: string}
+ *
+ * @extends AbstractDataTransferObject<CandidateArrayShape>
+ */
+class Candidate extends AbstractDataTransferObject
+{
+    public const KEY_MESSAGE = 'message';
+    public const KEY_FINISH_REASON = 'finishReason';
+    /**
+     * @var Message The generated message.
+     */
+    private Message $message;
+    /**
+     * @var FinishReasonEnum The reason generation stopped.
+     */
+    private FinishReasonEnum $finishReason;
+    /**
+     * Constructor.
+     *
+     * @since 0.1.0
+     *
+     * @param Message $message The generated message.
+     * @param FinishReasonEnum $finishReason The reason generation stopped.
+     */
+    public function __construct(Message $message, FinishReasonEnum $finishReason)
+    {
+        if (!$message->getRole()->isModel()) {
+            throw new InvalidArgumentException('Message must be a model message.');
+        }
+        $this->message = $message;
+        $this->finishReason = $finishReason;
+    }
+    /**
+     * Gets the generated message.
+     *
+     * @since 0.1.0
+     *
+     * @return Message The message.
+     */
+    public function getMessage(): Message
+    {
+        return $this->message;
+    }
+    /**
+     * Gets the finish reason.
+     *
+     * @since 0.1.0
+     *
+     * @return FinishReasonEnum The finish reason.
+     */
+    public function getFinishReason(): FinishReasonEnum
+    {
+        return $this->finishReason;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function getJsonSchema(): array
+    {
+        return ['type' => 'object', 'properties' => [self::KEY_MESSAGE => Message::getJsonSchema(), self::KEY_FINISH_REASON => ['type' => 'string', 'enum' => FinishReasonEnum::getValues(), 'description' => 'The reason generation stopped.']], 'required' => [self::KEY_MESSAGE, self::KEY_FINISH_REASON]];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     *
+     * @return CandidateArrayShape
+     */
+    public function toArray(): array
+    {
+        return [self::KEY_MESSAGE => $this->message->toArray(), self::KEY_FINISH_REASON => $this->finishReason->value];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function fromArray(array $array): self
+    {
+        static::validateFromArrayData($array, [self::KEY_MESSAGE, self::KEY_FINISH_REASON]);
+        $messageData = $array[self::KEY_MESSAGE];
+        return new self(Message::fromArray($messageData), FinishReasonEnum::from($array[self::KEY_FINISH_REASON]));
+    }
+    /**
+     * Performs a deep clone of the candidate.
+     *
+     * This method ensures that the message object is cloned to prevent
+     * modifications to the cloned candidate from affecting the original.
+     *
+     * @since 0.4.1
+     */
+    public function __clone()
+    {
+        $this->message = clone $this->message;
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Results/DTO/GenerativeAiResult.php b/src/wp-includes/php-ai-client/src/Results/DTO/GenerativeAiResult.php
new file mode 100644
index 0000000000000..0d1d0ccbc38c7
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Results/DTO/GenerativeAiResult.php
@@ -0,0 +1,420 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Results\DTO;
+
+use WordPress\AiClient\Common\AbstractDataTransferObject;
+use WordPress\AiClient\Common\Exception\InvalidArgumentException;
+use WordPress\AiClient\Common\Exception\RuntimeException;
+use WordPress\AiClient\Files\DTO\File;
+use WordPress\AiClient\Messages\DTO\Message;
+use WordPress\AiClient\Providers\DTO\ProviderMetadata;
+use WordPress\AiClient\Providers\Models\DTO\ModelMetadata;
+use WordPress\AiClient\Results\Contracts\ResultInterface;
+/**
+ * Represents the result of a generative AI operation.
+ *
+ * This DTO contains the generated candidates along with usage statistics
+ * and metadata from the AI provider.
+ *
+ * @since 0.1.0
+ *
+ * @phpstan-import-type CandidateArrayShape from Candidate
+ * @phpstan-import-type TokenUsageArrayShape from TokenUsage
+ * @phpstan-import-type ProviderMetadataArrayShape from ProviderMetadata
+ * @phpstan-import-type ModelMetadataArrayShape from ModelMetadata
+ *
+ * @phpstan-type GenerativeAiResultArrayShape array{
+ *     id: string,
+ *     candidates: array<CandidateArrayShape>,
+ *     tokenUsage: TokenUsageArrayShape,
+ *     providerMetadata: ProviderMetadataArrayShape,
+ *     modelMetadata: ModelMetadataArrayShape,
+ *     additionalData?: array<string, mixed>
+ * }
+ *
+ * @extends AbstractDataTransferObject<GenerativeAiResultArrayShape>
+ */
+class GenerativeAiResult extends AbstractDataTransferObject implements ResultInterface
+{
+    public const KEY_ID = 'id';
+    public const KEY_CANDIDATES = 'candidates';
+    public const KEY_TOKEN_USAGE = 'tokenUsage';
+    public const KEY_PROVIDER_METADATA = 'providerMetadata';
+    public const KEY_MODEL_METADATA = 'modelMetadata';
+    public const KEY_ADDITIONAL_DATA = 'additionalData';
+    /**
+     * @var string Unique identifier for this result.
+     */
+    private string $id;
+    /**
+     * @var Candidate[] The generated candidates.
+     */
+    private array $candidates;
+    /**
+     * @var TokenUsage Token usage statistics.
+     */
+    private \WordPress\AiClient\Results\DTO\TokenUsage $tokenUsage;
+    /**
+     * @var ProviderMetadata Provider metadata.
+     */
+    private ProviderMetadata $providerMetadata;
+    /**
+     * @var ModelMetadata Model metadata.
+     */
+    private ModelMetadata $modelMetadata;
+    /**
+     * @var array<string, mixed> Additional data.
+     */
+    private array $additionalData;
+    /**
+     * Constructor.
+     *
+     * @since 0.1.0
+     *
+     * @param string $id Unique identifier for this result.
+     * @param Candidate[] $candidates The generated candidates.
+     * @param TokenUsage $tokenUsage Token usage statistics.
+     * @param ProviderMetadata $providerMetadata Provider metadata.
+     * @param ModelMetadata $modelMetadata Model metadata.
+     * @param array<string, mixed> $additionalData Additional data.
+     * @throws InvalidArgumentException If no candidates provided.
+     */
+    public function __construct(string $id, array $candidates, \WordPress\AiClient\Results\DTO\TokenUsage $tokenUsage, ProviderMetadata $providerMetadata, ModelMetadata $modelMetadata, array $additionalData = [])
+    {
+        if (empty($candidates)) {
+            throw new InvalidArgumentException('At least one candidate must be provided');
+        }
+        $this->id = $id;
+        $this->candidates = $candidates;
+        $this->tokenUsage = $tokenUsage;
+        $this->providerMetadata = $providerMetadata;
+        $this->modelMetadata = $modelMetadata;
+        $this->additionalData = $additionalData;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public function getId(): string
+    {
+        return $this->id;
+    }
+    /**
+     * Gets the generated candidates.
+     *
+     * @since 0.1.0
+     *
+     * @return Candidate[] The candidates.
+     */
+    public function getCandidates(): array
+    {
+        return $this->candidates;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public function getTokenUsage(): \WordPress\AiClient\Results\DTO\TokenUsage
+    {
+        return $this->tokenUsage;
+    }
+    /**
+     * Gets the provider metadata.
+     *
+     * @since 0.1.0
+     *
+     * @return ProviderMetadata The provider metadata.
+     */
+    public function getProviderMetadata(): ProviderMetadata
+    {
+        return $this->providerMetadata;
+    }
+    /**
+     * Gets the model metadata.
+     *
+     * @since 0.1.0
+     *
+     * @return ModelMetadata The model metadata.
+     */
+    public function getModelMetadata(): ModelMetadata
+    {
+        return $this->modelMetadata;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public function getAdditionalData(): array
+    {
+        return $this->additionalData;
+    }
+    /**
+     * Gets the total number of candidates.
+     *
+     * @since 0.1.0
+     *
+     * @return int The total number of candidates.
+     */
+    public function getCandidateCount(): int
+    {
+        return count($this->candidates);
+    }
+    /**
+     * Checks if the result has multiple candidates.
+     *
+     * @since 0.1.0
+     *
+     * @return bool True if there are multiple candidates, false otherwise.
+     */
+    public function hasMultipleCandidates(): bool
+    {
+        return $this->getCandidateCount() > 1;
+    }
+    /**
+     * Converts the first candidate to text.
+     *
+     * Only text from the content channel is considered. Text within model thought or reasoning is ignored.
+     *
+     * @since 0.1.0
+     *
+     * @return string The text content.
+     * @throws RuntimeException If no text content.
+     */
+    public function toText(): string
+    {
+        $message = $this->candidates[0]->getMessage();
+        foreach ($message->getParts() as $part) {
+            $channel = $part->getChannel();
+            $text = $part->getText();
+            if ($channel->isContent() && $text !== null) {
+                return $text;
+            }
+        }
+        throw new RuntimeException('No text content found in first candidate');
+    }
+    /**
+     * Converts the first candidate to a file.
+     *
+     * Only files from the content channel are considered. Files within model thought or reasoning are ignored.
+     *
+     * @since 0.1.0
+     *
+     * @return File The file.
+     * @throws RuntimeException If no file content.
+     */
+    public function toFile(): File
+    {
+        $message = $this->candidates[0]->getMessage();
+        foreach ($message->getParts() as $part) {
+            $channel = $part->getChannel();
+            $file = $part->getFile();
+            if ($channel->isContent() && $file !== null) {
+                return $file;
+            }
+        }
+        throw new RuntimeException('No file content found in first candidate');
+    }
+    /**
+     * Converts the first candidate to an image file.
+     *
+     * @since 0.1.0
+     *
+     * @return File The image file.
+     * @throws RuntimeException If no image content.
+     */
+    public function toImageFile(): File
+    {
+        $file = $this->toFile();
+        if (!$file->isImage()) {
+            throw new RuntimeException(sprintf('File is not an image. MIME type: %s', $file->getMimeType()));
+        }
+        return $file;
+    }
+    /**
+     * Converts the first candidate to an audio file.
+     *
+     * @since 0.1.0
+     *
+     * @return File The audio file.
+     * @throws RuntimeException If no audio content.
+     */
+    public function toAudioFile(): File
+    {
+        $file = $this->toFile();
+        if (!$file->isAudio()) {
+            throw new RuntimeException(sprintf('File is not an audio file. MIME type: %s', $file->getMimeType()));
+        }
+        return $file;
+    }
+    /**
+     * Converts the first candidate to a video file.
+     *
+     * @since 0.1.0
+     *
+     * @return File The video file.
+     * @throws RuntimeException If no video content.
+     */
+    public function toVideoFile(): File
+    {
+        $file = $this->toFile();
+        if (!$file->isVideo()) {
+            throw new RuntimeException(sprintf('File is not a video file. MIME type: %s', $file->getMimeType()));
+        }
+        return $file;
+    }
+    /**
+     * Converts the first candidate to a message.
+     *
+     * @since 0.1.0
+     *
+     * @return Message The message.
+     */
+    public function toMessage(): Message
+    {
+        return $this->candidates[0]->getMessage();
+    }
+    /**
+     * Converts all candidates to text.
+     *
+     * @since 0.1.0
+     *
+     * @return list<string> Array of text content.
+     */
+    public function toTexts(): array
+    {
+        $texts = [];
+        foreach ($this->candidates as $candidate) {
+            $message = $candidate->getMessage();
+            foreach ($message->getParts() as $part) {
+                $channel = $part->getChannel();
+                $text = $part->getText();
+                if ($channel->isContent() && $text !== null) {
+                    $texts[] = $text;
+                    break;
+                }
+            }
+        }
+        return $texts;
+    }
+    /**
+     * Converts all candidates to files.
+     *
+     * @since 0.1.0
+     *
+     * @return list<File> Array of files.
+     */
+    public function toFiles(): array
+    {
+        $files = [];
+        foreach ($this->candidates as $candidate) {
+            $message = $candidate->getMessage();
+            foreach ($message->getParts() as $part) {
+                $channel = $part->getChannel();
+                $file = $part->getFile();
+                if ($channel->isContent() && $file !== null) {
+                    $files[] = $file;
+                    break;
+                }
+            }
+        }
+        return $files;
+    }
+    /**
+     * Converts all candidates to image files.
+     *
+     * @since 0.1.0
+     *
+     * @return list<File> Array of image files.
+     */
+    public function toImageFiles(): array
+    {
+        return array_values(array_filter($this->toFiles(), fn(File $file) => $file->isImage()));
+    }
+    /**
+     * Converts all candidates to audio files.
+     *
+     * @since 0.1.0
+     *
+     * @return list<File> Array of audio files.
+     */
+    public function toAudioFiles(): array
+    {
+        return array_values(array_filter($this->toFiles(), fn(File $file) => $file->isAudio()));
+    }
+    /**
+     * Converts all candidates to video files.
+     *
+     * @since 0.1.0
+     *
+     * @return list<File> Array of video files.
+     */
+    public function toVideoFiles(): array
+    {
+        return array_values(array_filter($this->toFiles(), fn(File $file) => $file->isVideo()));
+    }
+    /**
+     * Converts all candidates to messages.
+     *
+     * @since 0.1.0
+     *
+     * @return list<Message> Array of messages.
+     */
+    public function toMessages(): array
+    {
+        return array_values(array_map(fn(\WordPress\AiClient\Results\DTO\Candidate $candidate) => $candidate->getMessage(), $this->candidates));
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function getJsonSchema(): array
+    {
+        return ['type' => 'object', 'properties' => [self::KEY_ID => ['type' => 'string', 'description' => 'Unique identifier for this result.'], self::KEY_CANDIDATES => ['type' => 'array', 'items' => \WordPress\AiClient\Results\DTO\Candidate::getJsonSchema(), 'minItems' => 1, 'description' => 'The generated candidates.'], self::KEY_TOKEN_USAGE => \WordPress\AiClient\Results\DTO\TokenUsage::getJsonSchema(), self::KEY_PROVIDER_METADATA => ProviderMetadata::getJsonSchema(), self::KEY_MODEL_METADATA => ModelMetadata::getJsonSchema(), self::KEY_ADDITIONAL_DATA => ['type' => 'object', 'additionalProperties' => \true, 'description' => 'Additional data included in the API response.']], 'required' => [self::KEY_ID, self::KEY_CANDIDATES, self::KEY_TOKEN_USAGE, self::KEY_PROVIDER_METADATA, self::KEY_MODEL_METADATA]];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     *
+     * @return GenerativeAiResultArrayShape
+     */
+    public function toArray(): array
+    {
+        return [self::KEY_ID => $this->id, self::KEY_CANDIDATES => array_map(fn(\WordPress\AiClient\Results\DTO\Candidate $candidate) => $candidate->toArray(), $this->candidates), self::KEY_TOKEN_USAGE => $this->tokenUsage->toArray(), self::KEY_PROVIDER_METADATA => $this->providerMetadata->toArray(), self::KEY_MODEL_METADATA => $this->modelMetadata->toArray(), self::KEY_ADDITIONAL_DATA => $this->additionalData];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function fromArray(array $array): self
+    {
+        static::validateFromArrayData($array, [self::KEY_ID, self::KEY_CANDIDATES, self::KEY_TOKEN_USAGE, self::KEY_PROVIDER_METADATA, self::KEY_MODEL_METADATA]);
+        $candidates = array_map(fn(array $candidateData) => \WordPress\AiClient\Results\DTO\Candidate::fromArray($candidateData), $array[self::KEY_CANDIDATES]);
+        return new self($array[self::KEY_ID], $candidates, \WordPress\AiClient\Results\DTO\TokenUsage::fromArray($array[self::KEY_TOKEN_USAGE]), ProviderMetadata::fromArray($array[self::KEY_PROVIDER_METADATA]), ModelMetadata::fromArray($array[self::KEY_MODEL_METADATA]), $array[self::KEY_ADDITIONAL_DATA] ?? []);
+    }
+    /**
+     * Performs a deep clone of the result.
+     *
+     * This method ensures that all nested objects (candidates, token usage, metadata)
+     * are cloned to prevent modifications to the cloned result from affecting the original.
+     *
+     * @since 0.4.1
+     */
+    public function __clone()
+    {
+        $clonedCandidates = [];
+        foreach ($this->candidates as $candidate) {
+            $clonedCandidates[] = clone $candidate;
+        }
+        $this->candidates = $clonedCandidates;
+        $this->tokenUsage = clone $this->tokenUsage;
+        $this->providerMetadata = clone $this->providerMetadata;
+        $this->modelMetadata = clone $this->modelMetadata;
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Results/DTO/TokenUsage.php b/src/wp-includes/php-ai-client/src/Results/DTO/TokenUsage.php
new file mode 100644
index 0000000000000..df3201c92f77d
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Results/DTO/TokenUsage.php
@@ -0,0 +1,118 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Results\DTO;
+
+use WordPress\AiClient\Common\AbstractDataTransferObject;
+/**
+ * Represents token usage statistics for an AI operation.
+ *
+ * This DTO tracks the number of tokens used in prompts and completions,
+ * which is important for monitoring usage and costs.
+ *
+ * @since 0.1.0
+ *
+ * @phpstan-type TokenUsageArrayShape array{
+ *     promptTokens: int,
+ *     completionTokens: int,
+ *     totalTokens: int
+ * }
+ *
+ * @extends AbstractDataTransferObject<TokenUsageArrayShape>
+ */
+class TokenUsage extends AbstractDataTransferObject
+{
+    public const KEY_PROMPT_TOKENS = 'promptTokens';
+    public const KEY_COMPLETION_TOKENS = 'completionTokens';
+    public const KEY_TOTAL_TOKENS = 'totalTokens';
+    /**
+     * @var int Number of tokens in the prompt.
+     */
+    private int $promptTokens;
+    /**
+     * @var int Number of tokens in the completion.
+     */
+    private int $completionTokens;
+    /**
+     * @var int Total number of tokens used.
+     */
+    private int $totalTokens;
+    /**
+     * Constructor.
+     *
+     * @since 0.1.0
+     *
+     * @param int $promptTokens Number of tokens in the prompt.
+     * @param int $completionTokens Number of tokens in the completion.
+     * @param int $totalTokens Total number of tokens used.
+     */
+    public function __construct(int $promptTokens, int $completionTokens, int $totalTokens)
+    {
+        $this->promptTokens = $promptTokens;
+        $this->completionTokens = $completionTokens;
+        $this->totalTokens = $totalTokens;
+    }
+    /**
+     * Gets the number of prompt tokens.
+     *
+     * @since 0.1.0
+     *
+     * @return int The prompt token count.
+     */
+    public function getPromptTokens(): int
+    {
+        return $this->promptTokens;
+    }
+    /**
+     * Gets the number of completion tokens.
+     *
+     * @since 0.1.0
+     *
+     * @return int The completion token count.
+     */
+    public function getCompletionTokens(): int
+    {
+        return $this->completionTokens;
+    }
+    /**
+     * Gets the total number of tokens.
+     *
+     * @since 0.1.0
+     *
+     * @return int The total token count.
+     */
+    public function getTotalTokens(): int
+    {
+        return $this->totalTokens;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function getJsonSchema(): array
+    {
+        return ['type' => 'object', 'properties' => [self::KEY_PROMPT_TOKENS => ['type' => 'integer', 'description' => 'Number of tokens in the prompt.'], self::KEY_COMPLETION_TOKENS => ['type' => 'integer', 'description' => 'Number of tokens in the completion.'], self::KEY_TOTAL_TOKENS => ['type' => 'integer', 'description' => 'Total number of tokens used.']], 'required' => [self::KEY_PROMPT_TOKENS, self::KEY_COMPLETION_TOKENS, self::KEY_TOTAL_TOKENS]];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     *
+     * @return TokenUsageArrayShape
+     */
+    public function toArray(): array
+    {
+        return [self::KEY_PROMPT_TOKENS => $this->promptTokens, self::KEY_COMPLETION_TOKENS => $this->completionTokens, self::KEY_TOTAL_TOKENS => $this->totalTokens];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function fromArray(array $array): self
+    {
+        static::validateFromArrayData($array, [self::KEY_PROMPT_TOKENS, self::KEY_COMPLETION_TOKENS, self::KEY_TOTAL_TOKENS]);
+        return new self($array[self::KEY_PROMPT_TOKENS], $array[self::KEY_COMPLETION_TOKENS], $array[self::KEY_TOTAL_TOKENS]);
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Results/Enums/FinishReasonEnum.php b/src/wp-includes/php-ai-client/src/Results/Enums/FinishReasonEnum.php
new file mode 100644
index 0000000000000..b0c61b3fbe359
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Results/Enums/FinishReasonEnum.php
@@ -0,0 +1,45 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Results\Enums;
+
+use WordPress\AiClient\Common\AbstractEnum;
+/**
+ * Enum for finish reasons of AI generation.
+ *
+ * @since 0.1.0
+ *
+ * @method static self stop() Creates an instance for STOP reason.
+ * @method static self length() Creates an instance for LENGTH reason.
+ * @method static self contentFilter() Creates an instance for CONTENT_FILTER reason.
+ * @method static self toolCalls() Creates an instance for TOOL_CALLS reason.
+ * @method static self error() Creates an instance for ERROR reason.
+ * @method bool isStop() Checks if the reason is STOP.
+ * @method bool isLength() Checks if the reason is LENGTH.
+ * @method bool isContentFilter() Checks if the reason is CONTENT_FILTER.
+ * @method bool isToolCalls() Checks if the reason is TOOL_CALLS.
+ * @method bool isError() Checks if the reason is ERROR.
+ */
+class FinishReasonEnum extends AbstractEnum
+{
+    /**
+     * Generation stopped naturally.
+     */
+    public const STOP = 'stop';
+    /**
+     * Generation stopped due to max length.
+     */
+    public const LENGTH = 'length';
+    /**
+     * Generation stopped due to content filter.
+     */
+    public const CONTENT_FILTER = 'content_filter';
+    /**
+     * Generation stopped to make tool calls.
+     */
+    public const TOOL_CALLS = 'tool_calls';
+    /**
+     * Generation stopped due to error.
+     */
+    public const ERROR = 'error';
+}
diff --git a/src/wp-includes/php-ai-client/src/Tools/DTO/FunctionCall.php b/src/wp-includes/php-ai-client/src/Tools/DTO/FunctionCall.php
new file mode 100644
index 0000000000000..752a3c159f90d
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Tools/DTO/FunctionCall.php
@@ -0,0 +1,128 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Tools\DTO;
+
+use WordPress\AiClient\Common\AbstractDataTransferObject;
+use WordPress\AiClient\Common\Exception\InvalidArgumentException;
+/**
+ * Represents a function call request from an AI model.
+ *
+ * This DTO encapsulates information about a function that the AI model
+ * wants to invoke, including the function name and its arguments.
+ *
+ * @since 0.1.0
+ *
+ * @phpstan-type FunctionCallArrayShape array{id?: string, name?: string, args?: mixed}
+ *
+ * @extends AbstractDataTransferObject<FunctionCallArrayShape>
+ */
+class FunctionCall extends AbstractDataTransferObject
+{
+    public const KEY_ID = 'id';
+    public const KEY_NAME = 'name';
+    public const KEY_ARGS = 'args';
+    /**
+     * @var string|null Unique identifier for this function call.
+     */
+    private ?string $id;
+    /**
+     * @var string|null The name of the function to call.
+     */
+    private ?string $name;
+    /**
+     * @var mixed The arguments to pass to the function.
+     */
+    private $args;
+    /**
+     * Constructor.
+     *
+     * @since 0.1.0
+     *
+     * @param string|null $id Unique identifier for this function call.
+     * @param string|null $name The name of the function to call.
+     * @param mixed $args The arguments to pass to the function.
+     * @throws InvalidArgumentException If neither id nor name is provided.
+     */
+    public function __construct(?string $id = null, ?string $name = null, $args = null)
+    {
+        if ($id === null && $name === null) {
+            throw new InvalidArgumentException('At least one of id or name must be provided.');
+        }
+        $this->id = $id;
+        $this->name = $name;
+        $this->args = $args;
+    }
+    /**
+     * Gets the function call ID.
+     *
+     * @since 0.1.0
+     *
+     * @return string|null The function call ID.
+     */
+    public function getId(): ?string
+    {
+        return $this->id;
+    }
+    /**
+     * Gets the function name.
+     *
+     * @since 0.1.0
+     *
+     * @return string|null The function name.
+     */
+    public function getName(): ?string
+    {
+        return $this->name;
+    }
+    /**
+     * Gets the function arguments.
+     *
+     * @since 0.1.0
+     *
+     * @return mixed The function arguments.
+     */
+    public function getArgs()
+    {
+        return $this->args;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function getJsonSchema(): array
+    {
+        return ['type' => 'object', 'properties' => [self::KEY_ID => ['type' => 'string', 'description' => 'Unique identifier for this function call.'], self::KEY_NAME => ['type' => 'string', 'description' => 'The name of the function to call.'], self::KEY_ARGS => ['type' => ['string', 'number', 'boolean', 'object', 'array', 'null'], 'description' => 'The arguments to pass to the function.']], 'oneOf' => [['required' => [self::KEY_ID]], ['required' => [self::KEY_NAME]]]];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     *
+     * @return FunctionCallArrayShape
+     */
+    public function toArray(): array
+    {
+        $data = [];
+        if ($this->id !== null) {
+            $data[self::KEY_ID] = $this->id;
+        }
+        if ($this->name !== null) {
+            $data[self::KEY_NAME] = $this->name;
+        }
+        if ($this->args !== null) {
+            $data[self::KEY_ARGS] = $this->args;
+        }
+        return $data;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function fromArray(array $array): self
+    {
+        return new self($array[self::KEY_ID] ?? null, $array[self::KEY_NAME] ?? null, $array[self::KEY_ARGS] ?? null);
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Tools/DTO/FunctionDeclaration.php b/src/wp-includes/php-ai-client/src/Tools/DTO/FunctionDeclaration.php
new file mode 100644
index 0000000000000..935459f44ec0a
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Tools/DTO/FunctionDeclaration.php
@@ -0,0 +1,122 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Tools\DTO;
+
+use WordPress\AiClient\Common\AbstractDataTransferObject;
+/**
+ * Represents a function declaration for AI models.
+ *
+ * This DTO describes a function that can be called by the AI model,
+ * including its name, description, and parameter schema.
+ *
+ * @since 0.1.0
+ *
+ * @phpstan-type FunctionDeclarationArrayShape array{
+ *     name: string,
+ *     description: string,
+ *     parameters?: array<string, mixed>
+ * }
+ *
+ * @extends AbstractDataTransferObject<FunctionDeclarationArrayShape>
+ */
+class FunctionDeclaration extends AbstractDataTransferObject
+{
+    public const KEY_NAME = 'name';
+    public const KEY_DESCRIPTION = 'description';
+    public const KEY_PARAMETERS = 'parameters';
+    /**
+     * @var string The name of the function.
+     */
+    private string $name;
+    /**
+     * @var string A description of what the function does.
+     */
+    private string $description;
+    /**
+     * @var array<string, mixed>|null The JSON schema for the function parameters.
+     */
+    private ?array $parameters;
+    /**
+     * Constructor.
+     *
+     * @since 0.1.0
+     *
+     * @param string $name The name of the function.
+     * @param string $description A description of what the function does.
+     * @param array<string, mixed>|null $parameters The JSON schema for the function parameters.
+     */
+    public function __construct(string $name, string $description, ?array $parameters = null)
+    {
+        $this->name = $name;
+        $this->description = $description;
+        $this->parameters = $parameters;
+    }
+    /**
+     * Gets the function name.
+     *
+     * @since 0.1.0
+     *
+     * @return string The function name.
+     */
+    public function getName(): string
+    {
+        return $this->name;
+    }
+    /**
+     * Gets the function description.
+     *
+     * @since 0.1.0
+     *
+     * @return string The function description.
+     */
+    public function getDescription(): string
+    {
+        return $this->description;
+    }
+    /**
+     * Gets the function parameters schema.
+     *
+     * @since 0.1.0
+     *
+     * @return array<string, mixed>|null The parameters schema.
+     */
+    public function getParameters(): ?array
+    {
+        return $this->parameters;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function getJsonSchema(): array
+    {
+        return ['type' => 'object', 'properties' => [self::KEY_NAME => ['type' => 'string', 'description' => 'The name of the function.'], self::KEY_DESCRIPTION => ['type' => 'string', 'description' => 'A description of what the function does.'], self::KEY_PARAMETERS => ['type' => 'object', 'description' => 'The JSON schema for the function parameters.', 'additionalProperties' => \true]], 'required' => [self::KEY_NAME, self::KEY_DESCRIPTION]];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     *
+     * @return FunctionDeclarationArrayShape
+     */
+    public function toArray(): array
+    {
+        $data = [self::KEY_NAME => $this->name, self::KEY_DESCRIPTION => $this->description];
+        if ($this->parameters !== null) {
+            $data[self::KEY_PARAMETERS] = $this->parameters;
+        }
+        return $data;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function fromArray(array $array): self
+    {
+        static::validateFromArrayData($array, [self::KEY_NAME, self::KEY_DESCRIPTION]);
+        return new self($array[self::KEY_NAME], $array[self::KEY_DESCRIPTION], $array[self::KEY_PARAMETERS] ?? null);
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Tools/DTO/FunctionResponse.php b/src/wp-includes/php-ai-client/src/Tools/DTO/FunctionResponse.php
new file mode 100644
index 0000000000000..ced268261387c
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Tools/DTO/FunctionResponse.php
@@ -0,0 +1,119 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Tools\DTO;
+
+use WordPress\AiClient\Common\AbstractDataTransferObject;
+use WordPress\AiClient\Common\Exception\InvalidArgumentException;
+/**
+ * Represents a response to a function call.
+ *
+ * This DTO encapsulates the result of executing a function that was
+ * requested by the AI model through a FunctionCall.
+ *
+ * @since 0.1.0
+ *
+ * @phpstan-type FunctionResponseArrayShape array{id: string, name: string, response: mixed}
+ *
+ * @extends AbstractDataTransferObject<FunctionResponseArrayShape>
+ */
+class FunctionResponse extends AbstractDataTransferObject
+{
+    public const KEY_ID = 'id';
+    public const KEY_NAME = 'name';
+    public const KEY_RESPONSE = 'response';
+    /**
+     * @var string The ID of the function call this is responding to.
+     */
+    private string $id;
+    /**
+     * @var string The name of the function that was called.
+     */
+    private string $name;
+    /**
+     * @var mixed The response data from the function.
+     */
+    private $response;
+    /**
+     * Constructor.
+     *
+     * @since 0.1.0
+     *
+     * @param string $id The ID of the function call this is responding to.
+     * @param string $name The name of the function that was called.
+     * @param mixed $response The response data from the function.
+     */
+    public function __construct(string $id, string $name, $response)
+    {
+        $this->id = $id;
+        $this->name = $name;
+        $this->response = $response;
+    }
+    /**
+     * Gets the function call ID.
+     *
+     * @since 0.1.0
+     *
+     * @return string|null The function call ID.
+     */
+    public function getId(): ?string
+    {
+        return $this->id;
+    }
+    /**
+     * Gets the function name.
+     *
+     * @since 0.1.0
+     *
+     * @return string|null The function name.
+     */
+    public function getName(): ?string
+    {
+        return $this->name;
+    }
+    /**
+     * Gets the function response.
+     *
+     * @since 0.1.0
+     *
+     * @return mixed The response data.
+     */
+    public function getResponse()
+    {
+        return $this->response;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function getJsonSchema(): array
+    {
+        return ['type' => 'object', 'properties' => [self::KEY_ID => ['type' => 'string', 'description' => 'The ID of the function call this is responding to.'], self::KEY_NAME => ['type' => 'string', 'description' => 'The name of the function that was called.'], self::KEY_RESPONSE => ['type' => ['string', 'number', 'boolean', 'object', 'array', 'null'], 'description' => 'The response data from the function.']], 'oneOf' => [['required' => [self::KEY_RESPONSE, self::KEY_ID]], ['required' => [self::KEY_RESPONSE, self::KEY_NAME]]]];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     *
+     * @return FunctionResponseArrayShape
+     */
+    public function toArray(): array
+    {
+        return [self::KEY_ID => $this->id, self::KEY_NAME => $this->name, self::KEY_RESPONSE => $this->response];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function fromArray(array $array): self
+    {
+        static::validateFromArrayData($array, [self::KEY_RESPONSE]);
+        // Validate that at least one of id or name is provided
+        if (!array_key_exists(self::KEY_ID, $array) && !array_key_exists(self::KEY_NAME, $array)) {
+            throw new InvalidArgumentException('At least one of id or name must be provided.');
+        }
+        return new self($array[self::KEY_ID] ?? null, $array[self::KEY_NAME] ?? null, $array[self::KEY_RESPONSE]);
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/Tools/DTO/WebSearch.php b/src/wp-includes/php-ai-client/src/Tools/DTO/WebSearch.php
new file mode 100644
index 0000000000000..3ce1c62d37099
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/Tools/DTO/WebSearch.php
@@ -0,0 +1,95 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClient\Tools\DTO;
+
+use WordPress\AiClient\Common\AbstractDataTransferObject;
+/**
+ * Represents web search configuration for AI models.
+ *
+ * This DTO defines constraints for web searches that AI models can perform,
+ * including allowed and disallowed domains.
+ *
+ * @since 0.1.0
+ *
+ * @phpstan-type WebSearchArrayShape array{allowedDomains?: string[], disallowedDomains?: string[]}
+ *
+ * @extends AbstractDataTransferObject<WebSearchArrayShape>
+ */
+class WebSearch extends AbstractDataTransferObject
+{
+    public const KEY_ALLOWED_DOMAINS = 'allowedDomains';
+    public const KEY_DISALLOWED_DOMAINS = 'disallowedDomains';
+    /**
+     * @var string[] List of domains that are allowed for web search.
+     */
+    private array $allowedDomains;
+    /**
+     * @var string[] List of domains that are disallowed for web search.
+     */
+    private array $disallowedDomains;
+    /**
+     * Constructor.
+     *
+     * @since 0.1.0
+     *
+     * @param string[] $allowedDomains List of domains that are allowed for web search.
+     * @param string[] $disallowedDomains List of domains that are disallowed for web search.
+     */
+    public function __construct(array $allowedDomains = [], array $disallowedDomains = [])
+    {
+        $this->allowedDomains = $allowedDomains;
+        $this->disallowedDomains = $disallowedDomains;
+    }
+    /**
+     * Gets the allowed domains.
+     *
+     * @since 0.1.0
+     *
+     * @return string[] The allowed domains.
+     */
+    public function getAllowedDomains(): array
+    {
+        return $this->allowedDomains;
+    }
+    /**
+     * Gets the disallowed domains.
+     *
+     * @since 0.1.0
+     *
+     * @return string[] The disallowed domains.
+     */
+    public function getDisallowedDomains(): array
+    {
+        return $this->disallowedDomains;
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function getJsonSchema(): array
+    {
+        return ['type' => 'object', 'properties' => [self::KEY_ALLOWED_DOMAINS => ['type' => 'array', 'items' => ['type' => 'string'], 'description' => 'List of domains that are allowed for web search.'], self::KEY_DISALLOWED_DOMAINS => ['type' => 'array', 'items' => ['type' => 'string'], 'description' => 'List of domains that are disallowed for web search.']], 'required' => []];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     *
+     * @return WebSearchArrayShape
+     */
+    public function toArray(): array
+    {
+        return [self::KEY_ALLOWED_DOMAINS => $this->allowedDomains, self::KEY_DISALLOWED_DOMAINS => $this->disallowedDomains];
+    }
+    /**
+     * {@inheritDoc}
+     *
+     * @since 0.1.0
+     */
+    public static function fromArray(array $array): self
+    {
+        return new self($array[self::KEY_ALLOWED_DOMAINS] ?? [], $array[self::KEY_DISALLOWED_DOMAINS] ?? []);
+    }
+}
diff --git a/src/wp-includes/php-ai-client/src/polyfills.php b/src/wp-includes/php-ai-client/src/polyfills.php
new file mode 100644
index 0000000000000..20bb0fede1c0b
--- /dev/null
+++ b/src/wp-includes/php-ai-client/src/polyfills.php
@@ -0,0 +1,91 @@
+<?php
+
+/**
+ * Polyfills for PHP functions that may not be available in older versions.
+ *
+ * @since 0.1.0
+ */
+declare (strict_types=1);
+namespace WordPress\AiClientDependencies;
+
+if (!\function_exists('array_is_list') && !\function_exists('WordPress\AiClientDependencies\array_is_list')) {
+    /**
+     * Checks whether a given array is a list.
+     *
+     * An array is considered a list if its keys consist of consecutive numbers from 0 to count($array)-1.
+     *
+     * @since 0.1.0
+     *
+     * @param array<mixed> $array The array to check.
+     * @return bool True if the array is a list, false otherwise.
+     */
+    function array_is_list(array $array): bool
+    {
+        if ($array === []) {
+            return \true;
+        }
+        $expectedKey = 0;
+        foreach (\array_keys($array) as $key) {
+            if ($key !== $expectedKey) {
+                return \false;
+            }
+            $expectedKey++;
+        }
+        return \true;
+    }
+}
+if (!\function_exists('str_starts_with') && !\function_exists('WordPress\AiClientDependencies\str_starts_with')) {
+    /**
+     * Checks if a string starts with a given substring.
+     *
+     * @since 0.1.0
+     *
+     * @param string $haystack The string to search in.
+     * @param string $needle The substring to search for.
+     * @return bool True if $haystack starts with $needle, false otherwise.
+     */
+    function str_starts_with(string $haystack, string $needle): bool
+    {
+        if ('' === $needle) {
+            return \true;
+        }
+        return 0 === \strpos($haystack, $needle);
+    }
+}
+if (!\function_exists('str_contains') && !\function_exists('WordPress\AiClientDependencies\str_contains')) {
+    /**
+     * Checks if a string contains a given substring.
+     *
+     * @since 0.1.0
+     *
+     * @param string $haystack The string to search in.
+     * @param string $needle The substring to search for.
+     * @return bool True if $haystack contains $needle, false otherwise.
+     */
+    function str_contains(string $haystack, string $needle): bool
+    {
+        if ('' === $needle) {
+            return \true;
+        }
+        return \false !== \strpos($haystack, $needle);
+    }
+}
+if (!\function_exists('str_ends_with') && !\function_exists('WordPress\AiClientDependencies\str_ends_with')) {
+    /**
+     * Checks if a string ends with a given substring.
+     *
+     * @since 0.1.0
+     *
+     * @param string $haystack The string to search in.
+     * @param string $needle The substring to search for.
+     * @return bool True if $haystack ends with $needle, false otherwise.
+     */
+    function str_ends_with(string $haystack, string $needle): bool
+    {
+        if ('' === $haystack) {
+            return '' === $needle;
+        }
+        $len = \strlen($needle);
+        return \substr($haystack, -$len, $len) === $needle;
+    }
+}
diff --git a/src/wp-includes/php-ai-client/third-party/Http/Discovery/ClassDiscovery.php b/src/wp-includes/php-ai-client/third-party/Http/Discovery/ClassDiscovery.php
new file mode 100644
index 0000000000000..50c622f8bb6ba
--- /dev/null
+++ b/src/wp-includes/php-ai-client/third-party/Http/Discovery/ClassDiscovery.php
@@ -0,0 +1,219 @@
+<?php
+
+namespace WordPress\AiClientDependencies\Http\Discovery;
+
+use WordPress\AiClientDependencies\Http\Discovery\Exception\ClassInstantiationFailedException;
+use WordPress\AiClientDependencies\Http\Discovery\Exception\DiscoveryFailedException;
+use WordPress\AiClientDependencies\Http\Discovery\Exception\NoCandidateFoundException;
+use WordPress\AiClientDependencies\Http\Discovery\Exception\StrategyUnavailableException;
+use WordPress\AiClientDependencies\Http\Discovery\Strategy\DiscoveryStrategy;
+/**
+ * Registry that based find results on class existence.
+ *
+ * @author David de Boer <david@ddeboer.nl>
+ * @author Márk Sági-Kazár <mark.sagikazar@gmail.com>
+ * @author Tobias Nyholm <tobias.nyholm@gmail.com>
+ */
+abstract class ClassDiscovery
+{
+    /**
+     * A list of strategies to find classes.
+     *
+     * @var DiscoveryStrategy[]
+     */
+    private static $strategies = [Strategy\GeneratedDiscoveryStrategy::class, Strategy\CommonClassesStrategy::class, Strategy\CommonPsr17ClassesStrategy::class, Strategy\PuliBetaStrategy::class];
+    private static $deprecatedStrategies = [Strategy\PuliBetaStrategy::class => \true];
+    /**
+     * Discovery cache to make the second time we use discovery faster.
+     *
+     * @var array
+     */
+    private static $cache = [];
+    /**
+     * Finds a class.
+     *
+     * @param string $type
+     *
+     * @return string|\Closure
+     *
+     * @throws DiscoveryFailedException
+     */
+    protected static function findOneByType($type)
+    {
+        // Look in the cache
+        if (null !== $class = self::getFromCache($type)) {
+            return $class;
+        }
+        static $skipStrategy;
+        $skipStrategy ?? $skipStrategy = self::safeClassExists(Strategy\GeneratedDiscoveryStrategy::class) ? \false : Strategy\GeneratedDiscoveryStrategy::class;
+        $exceptions = [];
+        foreach (self::$strategies as $strategy) {
+            if ($skipStrategy === $strategy) {
+                continue;
+            }
+            try {
+                $candidates = $strategy::getCandidates($type);
+            } catch (StrategyUnavailableException $e) {
+                if (!isset(self::$deprecatedStrategies[$strategy])) {
+                    $exceptions[] = $e;
+                }
+                continue;
+            }
+            foreach ($candidates as $candidate) {
+                if (isset($candidate['condition'])) {
+                    if (!self::evaluateCondition($candidate['condition'])) {
+                        continue;
+                    }
+                }
+                // save the result for later use
+                self::storeInCache($type, $candidate);
+                return $candidate['class'];
+            }
+            $exceptions[] = new NoCandidateFoundException($strategy, $candidates);
+        }
+        throw DiscoveryFailedException::create($exceptions);
+    }
+    /**
+     * Get a value from cache.
+     *
+     * @param string $type
+     *
+     * @return string|null
+     */
+    private static function getFromCache($type)
+    {
+        if (!isset(self::$cache[$type])) {
+            return;
+        }
+        $candidate = self::$cache[$type];
+        if (isset($candidate['condition'])) {
+            if (!self::evaluateCondition($candidate['condition'])) {
+                return;
+            }
+        }
+        return $candidate['class'];
+    }
+    /**
+     * Store a value in cache.
+     *
+     * @param string $type
+     * @param string $class
+     */
+    private static function storeInCache($type, $class)
+    {
+        self::$cache[$type] = $class;
+    }
+    /**
+     * Set new strategies and clear the cache.
+     *
+     * @param string[] $strategies list of fully qualified class names that implement DiscoveryStrategy
+     */
+    public static function setStrategies(array $strategies)
+    {
+        self::$strategies = $strategies;
+        self::clearCache();
+    }
+    /**
+     * Returns the currently configured discovery strategies as fully qualified class names.
+     *
+     * @return string[]
+     */
+    public static function getStrategies(): iterable
+    {
+        return self::$strategies;
+    }
+    /**
+     * Append a strategy at the end of the strategy queue.
+     *
+     * @param string $strategy Fully qualified class name of a DiscoveryStrategy
+     */
+    public static function appendStrategy($strategy)
+    {
+        self::$strategies[] = $strategy;
+        self::clearCache();
+    }
+    /**
+     * Prepend a strategy at the beginning of the strategy queue.
+     *
+     * @param string $strategy Fully qualified class name to a DiscoveryStrategy
+     */
+    public static function prependStrategy($strategy)
+    {
+        array_unshift(self::$strategies, $strategy);
+        self::clearCache();
+    }
+    public static function clearCache()
+    {
+        self::$cache = [];
+    }
+    /**
+     * Evaluates conditions to boolean.
+     *
+     * @return bool
+     */
+    protected static function evaluateCondition($condition)
+    {
+        if (is_string($condition)) {
+            // Should be extended for functions, extensions???
+            return self::safeClassExists($condition);
+        }
+        if (is_callable($condition)) {
+            return (bool) $condition();
+        }
+        if (is_bool($condition)) {
+            return $condition;
+        }
+        if (is_array($condition)) {
+            foreach ($condition as $c) {
+                if (\false === static::evaluateCondition($c)) {
+                    // Immediately stop execution if the condition is false
+                    return \false;
+                }
+            }
+            return \true;
+        }
+        return \false;
+    }
+    /**
+     * Get an instance of the $class.
+     *
+     * @param string|\Closure $class a FQCN of a class or a closure that instantiate the class
+     *
+     * @return object
+     *
+     * @throws ClassInstantiationFailedException
+     */
+    protected static function instantiateClass($class)
+    {
+        try {
+            if (is_string($class)) {
+                return new $class();
+            }
+            if (is_callable($class)) {
+                return $class();
+            }
+        } catch (\Exception $e) {
+            throw new ClassInstantiationFailedException('Unexpected exception when instantiating class.', 0, $e);
+        }
+        throw new ClassInstantiationFailedException('Could not instantiate class because parameter is neither a callable nor a string');
+    }
+    /**
+     * We need a "safe" version of PHP's "class_exists" because Magento has a bug
+     * (or they call it a "feature"). Magento is throwing an exception if you do class_exists()
+     * on a class that ends with "Factory" and if that file does not exits.
+     *
+     * This function catches all potential exceptions and makes sure to always return a boolean.
+     *
+     * @param string $class
+     *
+     * @return bool
+     */
+    public static function safeClassExists($class)
+    {
+        try {
+            return class_exists($class) || interface_exists($class);
+        } catch (\Exception $e) {
+            return \false;
+        }
+    }
+}
diff --git a/src/wp-includes/php-ai-client/third-party/Http/Discovery/Exception.php b/src/wp-includes/php-ai-client/third-party/Http/Discovery/Exception.php
new file mode 100644
index 0000000000000..183ac1dbf1f04
--- /dev/null
+++ b/src/wp-includes/php-ai-client/third-party/Http/Discovery/Exception.php
@@ -0,0 +1,12 @@
+<?php
+
+namespace WordPress\AiClientDependencies\Http\Discovery;
+
+/**
+ * An interface implemented by all discovery related exceptions.
+ *
+ * @author Tobias Nyholm <tobias.nyholm@gmail.com>
+ */
+interface Exception extends \Throwable
+{
+}
diff --git a/src/wp-includes/php-ai-client/third-party/Http/Discovery/Exception/ClassInstantiationFailedException.php b/src/wp-includes/php-ai-client/third-party/Http/Discovery/Exception/ClassInstantiationFailedException.php
new file mode 100644
index 0000000000000..0dc05d7a5d4d7
--- /dev/null
+++ b/src/wp-includes/php-ai-client/third-party/Http/Discovery/Exception/ClassInstantiationFailedException.php
@@ -0,0 +1,13 @@
+<?php
+
+namespace WordPress\AiClientDependencies\Http\Discovery\Exception;
+
+use WordPress\AiClientDependencies\Http\Discovery\Exception;
+/**
+ * Thrown when a class fails to instantiate.
+ *
+ * @author Tobias Nyholm <tobias.nyholm@gmail.com>
+ */
+final class ClassInstantiationFailedException extends \RuntimeException implements Exception
+{
+}
diff --git a/src/wp-includes/php-ai-client/third-party/Http/Discovery/Exception/DiscoveryFailedException.php b/src/wp-includes/php-ai-client/third-party/Http/Discovery/Exception/DiscoveryFailedException.php
new file mode 100644
index 0000000000000..f765acddd3fe9
--- /dev/null
+++ b/src/wp-includes/php-ai-client/third-party/Http/Discovery/Exception/DiscoveryFailedException.php
@@ -0,0 +1,45 @@
+<?php
+
+namespace WordPress\AiClientDependencies\Http\Discovery\Exception;
+
+use WordPress\AiClientDependencies\Http\Discovery\Exception;
+/**
+ * Thrown when all discovery strategies fails to find a resource.
+ *
+ * @author Tobias Nyholm <tobias.nyholm@gmail.com>
+ */
+final class DiscoveryFailedException extends \Exception implements Exception
+{
+    /**
+     * @var \Exception[]
+     */
+    private $exceptions;
+    /**
+     * @param string       $message
+     * @param \Exception[] $exceptions
+     */
+    public function __construct($message, array $exceptions = [])
+    {
+        $this->exceptions = $exceptions;
+        parent::__construct($message);
+    }
+    /**
+     * @param \Exception[] $exceptions
+     */
+    public static function create($exceptions)
+    {
+        $message = 'Could not find resource using any discovery strategy. Find more information at http://docs.php-http.org/en/latest/discovery.html#common-errors';
+        foreach ($exceptions as $e) {
+            $message .= "\n - " . $e->getMessage();
+        }
+        $message .= "\n\n";
+        return new self($message, $exceptions);
+    }
+    /**
+     * @return \Exception[]
+     */
+    public function getExceptions()
+    {
+        return $this->exceptions;
+    }
+}
diff --git a/src/wp-includes/php-ai-client/third-party/Http/Discovery/Exception/NoCandidateFoundException.php b/src/wp-includes/php-ai-client/third-party/Http/Discovery/Exception/NoCandidateFoundException.php
new file mode 100644
index 0000000000000..621d3f708e76e
--- /dev/null
+++ b/src/wp-includes/php-ai-client/third-party/Http/Discovery/Exception/NoCandidateFoundException.php
@@ -0,0 +1,34 @@
+<?php
+
+namespace WordPress\AiClientDependencies\Http\Discovery\Exception;
+
+use WordPress\AiClientDependencies\Http\Discovery\Exception;
+/**
+ * When we have used a strategy but no candidates provided by that strategy could be used.
+ *
+ * @author Tobias Nyholm <tobias.nyholm@gmail.com>
+ */
+final class NoCandidateFoundException extends \Exception implements Exception
+{
+    /**
+     * @param string $strategy
+     */
+    public function __construct($strategy, array $candidates)
+    {
+        $classes = array_map(function ($a) {
+            return $a['class'];
+        }, $candidates);
+        $message = sprintf('No valid candidate found using strategy "%s". We tested the following candidates: %s.', $strategy, implode(', ', array_map([$this, 'stringify'], $classes)));
+        parent::__construct($message);
+    }
+    private function stringify($mixed)
+    {
+        if (is_string($mixed)) {
+            return $mixed;
+        }
+        if (is_array($mixed) && 2 === count($mixed)) {
+            return sprintf('%s::%s', $this->stringify($mixed[0]), $mixed[1]);
+        }
+        return is_object($mixed) ? get_class($mixed) : gettype($mixed);
+    }
+}
diff --git a/src/wp-includes/php-ai-client/third-party/Http/Discovery/Exception/NotFoundException.php b/src/wp-includes/php-ai-client/third-party/Http/Discovery/Exception/NotFoundException.php
new file mode 100644
index 0000000000000..3d93ddf48aaaa
--- /dev/null
+++ b/src/wp-includes/php-ai-client/third-party/Http/Discovery/Exception/NotFoundException.php
@@ -0,0 +1,16 @@
+<?php
+
+namespace WordPress\AiClientDependencies\Http\Discovery\Exception;
+
+use WordPress\AiClientDependencies\Http\Discovery\Exception;
+/**
+ * Thrown when a discovery does not find any matches.
+ *
+ * @final do NOT extend this class, not final for BC reasons
+ *
+ * @author Márk Sági-Kazár <mark.sagikazar@gmail.com>
+ */
+/* final */
+class NotFoundException extends \RuntimeException implements Exception
+{
+}
diff --git a/src/wp-includes/php-ai-client/third-party/Http/Discovery/Exception/PuliUnavailableException.php b/src/wp-includes/php-ai-client/third-party/Http/Discovery/Exception/PuliUnavailableException.php
new file mode 100644
index 0000000000000..0ed157f7a0bbf
--- /dev/null
+++ b/src/wp-includes/php-ai-client/third-party/Http/Discovery/Exception/PuliUnavailableException.php
@@ -0,0 +1,12 @@
+<?php
+
+namespace WordPress\AiClientDependencies\Http\Discovery\Exception;
+
+/**
+ * Thrown when we can't use Puli for discovery.
+ *
+ * @author Tobias Nyholm <tobias.nyholm@gmail.com>
+ */
+final class PuliUnavailableException extends StrategyUnavailableException
+{
+}
diff --git a/src/wp-includes/php-ai-client/third-party/Http/Discovery/Exception/StrategyUnavailableException.php b/src/wp-includes/php-ai-client/third-party/Http/Discovery/Exception/StrategyUnavailableException.php
new file mode 100644
index 0000000000000..4887391eacd6c
--- /dev/null
+++ b/src/wp-includes/php-ai-client/third-party/Http/Discovery/Exception/StrategyUnavailableException.php
@@ -0,0 +1,14 @@
+<?php
+
+namespace WordPress\AiClientDependencies\Http\Discovery\Exception;
+
+use WordPress\AiClientDependencies\Http\Discovery\Exception;
+/**
+ * This exception is thrown when we cannot use a discovery strategy. This is *not* thrown when
+ * the discovery fails to find a class.
+ *
+ * @author Tobias Nyholm <tobias.nyholm@gmail.com>
+ */
+class StrategyUnavailableException extends \RuntimeException implements Exception
+{
+}
diff --git a/src/wp-includes/php-ai-client/third-party/Http/Discovery/Psr17FactoryDiscovery.php b/src/wp-includes/php-ai-client/third-party/Http/Discovery/Psr17FactoryDiscovery.php
new file mode 100644
index 0000000000000..5e22ab1dd03c0
--- /dev/null
+++ b/src/wp-includes/php-ai-client/third-party/Http/Discovery/Psr17FactoryDiscovery.php
@@ -0,0 +1,119 @@
+<?php
+
+namespace WordPress\AiClientDependencies\Http\Discovery;
+
+use WordPress\AiClientDependencies\Http\Discovery\Exception\DiscoveryFailedException;
+use WordPress\AiClientDependencies\Http\Discovery\Exception\NotFoundException as RealNotFoundException;
+use WordPress\AiClientDependencies\Psr\Http\Message\RequestFactoryInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\ResponseFactoryInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\ServerRequestFactoryInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\StreamFactoryInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\UploadedFileFactoryInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\UriFactoryInterface;
+/**
+ * Finds PSR-17 factories.
+ *
+ * @author Tobias Nyholm <tobias.nyholm@gmail.com>
+ */
+final class Psr17FactoryDiscovery extends ClassDiscovery
+{
+    private static function createException($type, Exception $e)
+    {
+        return new RealNotFoundException('No PSR-17 ' . $type . ' found. Install a package from this list: https://packagist.org/providers/psr/http-factory-implementation', 0, $e);
+    }
+    /**
+     * @return RequestFactoryInterface
+     *
+     * @throws RealNotFoundException
+     */
+    public static function findRequestFactory()
+    {
+        try {
+            $messageFactory = static::findOneByType(RequestFactoryInterface::class);
+        } catch (DiscoveryFailedException $e) {
+            throw self::createException('request factory', $e);
+        }
+        return static::instantiateClass($messageFactory);
+    }
+    /**
+     * @return ResponseFactoryInterface
+     *
+     * @throws RealNotFoundException
+     */
+    public static function findResponseFactory()
+    {
+        try {
+            $messageFactory = static::findOneByType(ResponseFactoryInterface::class);
+        } catch (DiscoveryFailedException $e) {
+            throw self::createException('response factory', $e);
+        }
+        return static::instantiateClass($messageFactory);
+    }
+    /**
+     * @return ServerRequestFactoryInterface
+     *
+     * @throws RealNotFoundException
+     */
+    public static function findServerRequestFactory()
+    {
+        try {
+            $messageFactory = static::findOneByType(ServerRequestFactoryInterface::class);
+        } catch (DiscoveryFailedException $e) {
+            throw self::createException('server request factory', $e);
+        }
+        return static::instantiateClass($messageFactory);
+    }
+    /**
+     * @return StreamFactoryInterface
+     *
+     * @throws RealNotFoundException
+     */
+    public static function findStreamFactory()
+    {
+        try {
+            $messageFactory = static::findOneByType(StreamFactoryInterface::class);
+        } catch (DiscoveryFailedException $e) {
+            throw self::createException('stream factory', $e);
+        }
+        return static::instantiateClass($messageFactory);
+    }
+    /**
+     * @return UploadedFileFactoryInterface
+     *
+     * @throws RealNotFoundException
+     */
+    public static function findUploadedFileFactory()
+    {
+        try {
+            $messageFactory = static::findOneByType(UploadedFileFactoryInterface::class);
+        } catch (DiscoveryFailedException $e) {
+            throw self::createException('uploaded file factory', $e);
+        }
+        return static::instantiateClass($messageFactory);
+    }
+    /**
+     * @return UriFactoryInterface
+     *
+     * @throws RealNotFoundException
+     */
+    public static function findUriFactory()
+    {
+        try {
+            $messageFactory = static::findOneByType(UriFactoryInterface::class);
+        } catch (DiscoveryFailedException $e) {
+            throw self::createException('url factory', $e);
+        }
+        return static::instantiateClass($messageFactory);
+    }
+    /**
+     * @return UriFactoryInterface
+     *
+     * @throws RealNotFoundException
+     *
+     * @deprecated This will be removed in 2.0. Consider using the findUriFactory() method.
+     */
+    public static function findUrlFactory()
+    {
+        return static::findUriFactory();
+    }
+}
diff --git a/src/wp-includes/php-ai-client/third-party/Http/Discovery/Psr18ClientDiscovery.php b/src/wp-includes/php-ai-client/third-party/Http/Discovery/Psr18ClientDiscovery.php
new file mode 100644
index 0000000000000..ceca0e4a515b5
--- /dev/null
+++ b/src/wp-includes/php-ai-client/third-party/Http/Discovery/Psr18ClientDiscovery.php
@@ -0,0 +1,31 @@
+<?php
+
+namespace WordPress\AiClientDependencies\Http\Discovery;
+
+use WordPress\AiClientDependencies\Http\Discovery\Exception\DiscoveryFailedException;
+use WordPress\AiClientDependencies\Http\Discovery\Exception\NotFoundException as RealNotFoundException;
+use WordPress\AiClientDependencies\Psr\Http\Client\ClientInterface;
+/**
+ * Finds a PSR-18 HTTP Client.
+ *
+ * @author Tobias Nyholm <tobias.nyholm@gmail.com>
+ */
+final class Psr18ClientDiscovery extends ClassDiscovery
+{
+    /**
+     * Finds a PSR-18 HTTP Client.
+     *
+     * @return ClientInterface
+     *
+     * @throws RealNotFoundException
+     */
+    public static function find()
+    {
+        try {
+            $client = static::findOneByType(ClientInterface::class);
+        } catch (DiscoveryFailedException $e) {
+            throw new RealNotFoundException('No PSR-18 clients found. Make sure to install a package providing "psr/http-client-implementation". Example: "php-http/guzzle7-adapter".', 0, $e);
+        }
+        return static::instantiateClass($client);
+    }
+}
diff --git a/src/wp-includes/php-ai-client/third-party/Http/Discovery/Strategy/CommonClassesStrategy.php b/src/wp-includes/php-ai-client/third-party/Http/Discovery/Strategy/CommonClassesStrategy.php
new file mode 100644
index 0000000000000..e9c65c8220e93
--- /dev/null
+++ b/src/wp-includes/php-ai-client/third-party/Http/Discovery/Strategy/CommonClassesStrategy.php
@@ -0,0 +1,116 @@
+<?php
+
+namespace WordPress\AiClientDependencies\Http\Discovery\Strategy;
+
+use WordPress\AiClientDependencies\GuzzleHttp\Client as GuzzleHttp;
+use WordPress\AiClientDependencies\GuzzleHttp\Promise\Promise;
+use WordPress\AiClientDependencies\GuzzleHttp\Psr7\Request as GuzzleRequest;
+use WordPress\AiClientDependencies\Http\Adapter\Artax\Client as Artax;
+use WordPress\AiClientDependencies\Http\Adapter\Buzz\Client as Buzz;
+use WordPress\AiClientDependencies\Http\Adapter\Cake\Client as Cake;
+use WordPress\AiClientDependencies\Http\Adapter\Guzzle5\Client as Guzzle5;
+use WordPress\AiClientDependencies\Http\Adapter\Guzzle6\Client as Guzzle6;
+use WordPress\AiClientDependencies\Http\Adapter\Guzzle7\Client as Guzzle7;
+use WordPress\AiClientDependencies\Http\Adapter\React\Client as React;
+use WordPress\AiClientDependencies\Http\Client\Curl\Client as Curl;
+use WordPress\AiClientDependencies\Http\Client\HttpAsyncClient;
+use WordPress\AiClientDependencies\Http\Client\HttpClient;
+use WordPress\AiClientDependencies\Http\Client\Socket\Client as Socket;
+use WordPress\AiClientDependencies\Http\Discovery\ClassDiscovery;
+use WordPress\AiClientDependencies\Http\Discovery\Exception\NotFoundException;
+use WordPress\AiClientDependencies\Http\Discovery\Psr17FactoryDiscovery;
+use WordPress\AiClientDependencies\Http\Message\MessageFactory;
+use WordPress\AiClientDependencies\Http\Message\MessageFactory\DiactorosMessageFactory;
+use WordPress\AiClientDependencies\Http\Message\MessageFactory\GuzzleMessageFactory;
+use WordPress\AiClientDependencies\Http\Message\MessageFactory\SlimMessageFactory;
+use WordPress\AiClientDependencies\Http\Message\StreamFactory;
+use WordPress\AiClientDependencies\Http\Message\StreamFactory\DiactorosStreamFactory;
+use WordPress\AiClientDependencies\Http\Message\StreamFactory\GuzzleStreamFactory;
+use WordPress\AiClientDependencies\Http\Message\StreamFactory\SlimStreamFactory;
+use WordPress\AiClientDependencies\Http\Message\UriFactory;
+use WordPress\AiClientDependencies\Http\Message\UriFactory\DiactorosUriFactory;
+use WordPress\AiClientDependencies\Http\Message\UriFactory\GuzzleUriFactory;
+use WordPress\AiClientDependencies\Http\Message\UriFactory\SlimUriFactory;
+use WordPress\AiClientDependencies\Laminas\Diactoros\Request as DiactorosRequest;
+use WordPress\AiClientDependencies\Nyholm\Psr7\Factory\HttplugFactory as NyholmHttplugFactory;
+use WordPress\AiClientDependencies\Psr\Http\Client\ClientInterface as Psr18Client;
+use WordPress\AiClientDependencies\Psr\Http\Message\RequestFactoryInterface as Psr17RequestFactory;
+use WordPress\AiClientDependencies\Slim\Http\Request as SlimRequest;
+use WordPress\AiClientDependencies\Symfony\Component\HttpClient\HttplugClient as SymfonyHttplug;
+use WordPress\AiClientDependencies\Symfony\Component\HttpClient\Psr18Client as SymfonyPsr18;
+/**
+ * @internal
+ *
+ * @author Tobias Nyholm <tobias.nyholm@gmail.com>
+ *
+ * Don't miss updating src/Composer/Plugin.php when adding a new supported class.
+ */
+final class CommonClassesStrategy implements DiscoveryStrategy
+{
+    /**
+     * @var array
+     */
+    private static $classes = [MessageFactory::class => [['class' => NyholmHttplugFactory::class, 'condition' => [NyholmHttplugFactory::class]], ['class' => GuzzleMessageFactory::class, 'condition' => [GuzzleRequest::class, GuzzleMessageFactory::class]], ['class' => DiactorosMessageFactory::class, 'condition' => [DiactorosRequest::class, DiactorosMessageFactory::class]], ['class' => SlimMessageFactory::class, 'condition' => [SlimRequest::class, SlimMessageFactory::class]]], StreamFactory::class => [['class' => NyholmHttplugFactory::class, 'condition' => [NyholmHttplugFactory::class]], ['class' => GuzzleStreamFactory::class, 'condition' => [GuzzleRequest::class, GuzzleStreamFactory::class]], ['class' => DiactorosStreamFactory::class, 'condition' => [DiactorosRequest::class, DiactorosStreamFactory::class]], ['class' => SlimStreamFactory::class, 'condition' => [SlimRequest::class, SlimStreamFactory::class]]], UriFactory::class => [['class' => NyholmHttplugFactory::class, 'condition' => [NyholmHttplugFactory::class]], ['class' => GuzzleUriFactory::class, 'condition' => [GuzzleRequest::class, GuzzleUriFactory::class]], ['class' => DiactorosUriFactory::class, 'condition' => [DiactorosRequest::class, DiactorosUriFactory::class]], ['class' => SlimUriFactory::class, 'condition' => [SlimRequest::class, SlimUriFactory::class]]], HttpAsyncClient::class => [['class' => SymfonyHttplug::class, 'condition' => [SymfonyHttplug::class, Promise::class, [self::class, 'isPsr17FactoryInstalled']]], ['class' => Guzzle7::class, 'condition' => Guzzle7::class], ['class' => Guzzle6::class, 'condition' => Guzzle6::class], ['class' => Curl::class, 'condition' => Curl::class], ['class' => React::class, 'condition' => React::class]], HttpClient::class => [['class' => SymfonyHttplug::class, 'condition' => [SymfonyHttplug::class, [self::class, 'isPsr17FactoryInstalled'], [self::class, 'isSymfonyImplementingHttpClient']]], ['class' => Guzzle7::class, 'condition' => Guzzle7::class], ['class' => Guzzle6::class, 'condition' => Guzzle6::class], ['class' => Guzzle5::class, 'condition' => Guzzle5::class], ['class' => Curl::class, 'condition' => Curl::class], ['class' => Socket::class, 'condition' => Socket::class], ['class' => Buzz::class, 'condition' => Buzz::class], ['class' => React::class, 'condition' => React::class], ['class' => Cake::class, 'condition' => Cake::class], ['class' => Artax::class, 'condition' => Artax::class], ['class' => [self::class, 'buzzInstantiate'], 'condition' => [\WordPress\AiClientDependencies\Buzz\Client\FileGetContents::class, \WordPress\AiClientDependencies\Buzz\Message\ResponseBuilder::class]]], Psr18Client::class => [['class' => [self::class, 'symfonyPsr18Instantiate'], 'condition' => [SymfonyPsr18::class, Psr17RequestFactory::class]], ['class' => GuzzleHttp::class, 'condition' => [self::class, 'isGuzzleImplementingPsr18']], ['class' => [self::class, 'buzzInstantiate'], 'condition' => [\WordPress\AiClientDependencies\Buzz\Client\FileGetContents::class, \WordPress\AiClientDependencies\Buzz\Message\ResponseBuilder::class]]]];
+    public static function getCandidates($type)
+    {
+        if (Psr18Client::class === $type) {
+            return self::getPsr18Candidates();
+        }
+        return self::$classes[$type] ?? [];
+    }
+    /**
+     * @return array The return value is always an array with zero or more elements. Each
+     *               element is an array with two keys ['class' => string, 'condition' => mixed].
+     */
+    private static function getPsr18Candidates()
+    {
+        $candidates = self::$classes[Psr18Client::class];
+        // HTTPlug 2.0 clients implements PSR18Client too.
+        foreach (self::$classes[HttpClient::class] as $c) {
+            if (!is_string($c['class'])) {
+                continue;
+            }
+            try {
+                if (ClassDiscovery::safeClassExists($c['class']) && is_subclass_of($c['class'], Psr18Client::class)) {
+                    $candidates[] = $c;
+                }
+            } catch (\Throwable $e) {
+                trigger_error(sprintf('Got exception "%s (%s)" while checking if a PSR-18 Client is available', get_class($e), $e->getMessage()), \E_USER_WARNING);
+            }
+        }
+        return $candidates;
+    }
+    public static function buzzInstantiate()
+    {
+        return new \WordPress\AiClientDependencies\Buzz\Client\FileGetContents(Psr17FactoryDiscovery::findResponseFactory());
+    }
+    public static function symfonyPsr18Instantiate()
+    {
+        return new SymfonyPsr18(null, Psr17FactoryDiscovery::findResponseFactory(), Psr17FactoryDiscovery::findStreamFactory());
+    }
+    public static function isGuzzleImplementingPsr18()
+    {
+        return defined('GuzzleHttp\ClientInterface::MAJOR_VERSION');
+    }
+    public static function isSymfonyImplementingHttpClient()
+    {
+        return is_subclass_of(SymfonyHttplug::class, HttpClient::class);
+    }
+    /**
+     * Can be used as a condition.
+     *
+     * @return bool
+     */
+    public static function isPsr17FactoryInstalled()
+    {
+        try {
+            Psr17FactoryDiscovery::findResponseFactory();
+        } catch (NotFoundException $e) {
+            return \false;
+        } catch (\Throwable $e) {
+            trigger_error(sprintf('Got exception "%s (%s)" while checking if a PSR-17 ResponseFactory is available', get_class($e), $e->getMessage()), \E_USER_WARNING);
+            return \false;
+        }
+        return \true;
+    }
+}
diff --git a/src/wp-includes/php-ai-client/third-party/Http/Discovery/Strategy/CommonPsr17ClassesStrategy.php b/src/wp-includes/php-ai-client/third-party/Http/Discovery/Strategy/CommonPsr17ClassesStrategy.php
new file mode 100644
index 0000000000000..7a310542c13c4
--- /dev/null
+++ b/src/wp-includes/php-ai-client/third-party/Http/Discovery/Strategy/CommonPsr17ClassesStrategy.php
@@ -0,0 +1,34 @@
+<?php
+
+namespace WordPress\AiClientDependencies\Http\Discovery\Strategy;
+
+use WordPress\AiClientDependencies\Psr\Http\Message\RequestFactoryInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\ResponseFactoryInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\ServerRequestFactoryInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\StreamFactoryInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\UploadedFileFactoryInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\UriFactoryInterface;
+/**
+ * @internal
+ *
+ * @author Tobias Nyholm <tobias.nyholm@gmail.com>
+ *
+ * Don't miss updating src/Composer/Plugin.php when adding a new supported class.
+ */
+final class CommonPsr17ClassesStrategy implements DiscoveryStrategy
+{
+    /**
+     * @var array
+     */
+    private static $classes = [RequestFactoryInterface::class => ['Phalcon\Http\Message\RequestFactory', 'Nyholm\Psr7\Factory\Psr17Factory', 'GuzzleHttp\Psr7\HttpFactory', 'WordPress\AiClientDependencies\Http\Factory\Diactoros\RequestFactory', 'WordPress\AiClientDependencies\Http\Factory\Guzzle\RequestFactory', 'WordPress\AiClientDependencies\Http\Factory\Slim\RequestFactory', 'Laminas\Diactoros\RequestFactory', 'Slim\Psr7\Factory\RequestFactory', 'WordPress\AiClientDependencies\HttpSoft\Message\RequestFactory'], ResponseFactoryInterface::class => ['Phalcon\Http\Message\ResponseFactory', 'Nyholm\Psr7\Factory\Psr17Factory', 'GuzzleHttp\Psr7\HttpFactory', 'WordPress\AiClientDependencies\Http\Factory\Diactoros\ResponseFactory', 'WordPress\AiClientDependencies\Http\Factory\Guzzle\ResponseFactory', 'WordPress\AiClientDependencies\Http\Factory\Slim\ResponseFactory', 'Laminas\Diactoros\ResponseFactory', 'Slim\Psr7\Factory\ResponseFactory', 'WordPress\AiClientDependencies\HttpSoft\Message\ResponseFactory'], ServerRequestFactoryInterface::class => ['Phalcon\Http\Message\ServerRequestFactory', 'Nyholm\Psr7\Factory\Psr17Factory', 'GuzzleHttp\Psr7\HttpFactory', 'WordPress\AiClientDependencies\Http\Factory\Diactoros\ServerRequestFactory', 'WordPress\AiClientDependencies\Http\Factory\Guzzle\ServerRequestFactory', 'WordPress\AiClientDependencies\Http\Factory\Slim\ServerRequestFactory', 'Laminas\Diactoros\ServerRequestFactory', 'Slim\Psr7\Factory\ServerRequestFactory', 'WordPress\AiClientDependencies\HttpSoft\Message\ServerRequestFactory'], StreamFactoryInterface::class => ['Phalcon\Http\Message\StreamFactory', 'Nyholm\Psr7\Factory\Psr17Factory', 'GuzzleHttp\Psr7\HttpFactory', 'WordPress\AiClientDependencies\Http\Factory\Diactoros\StreamFactory', 'WordPress\AiClientDependencies\Http\Factory\Guzzle\StreamFactory', 'WordPress\AiClientDependencies\Http\Factory\Slim\StreamFactory', 'Laminas\Diactoros\StreamFactory', 'Slim\Psr7\Factory\StreamFactory', 'WordPress\AiClientDependencies\HttpSoft\Message\StreamFactory'], UploadedFileFactoryInterface::class => ['Phalcon\Http\Message\UploadedFileFactory', 'Nyholm\Psr7\Factory\Psr17Factory', 'GuzzleHttp\Psr7\HttpFactory', 'WordPress\AiClientDependencies\Http\Factory\Diactoros\UploadedFileFactory', 'WordPress\AiClientDependencies\Http\Factory\Guzzle\UploadedFileFactory', 'WordPress\AiClientDependencies\Http\Factory\Slim\UploadedFileFactory', 'Laminas\Diactoros\UploadedFileFactory', 'Slim\Psr7\Factory\UploadedFileFactory', 'WordPress\AiClientDependencies\HttpSoft\Message\UploadedFileFactory'], UriFactoryInterface::class => ['Phalcon\Http\Message\UriFactory', 'Nyholm\Psr7\Factory\Psr17Factory', 'GuzzleHttp\Psr7\HttpFactory', 'WordPress\AiClientDependencies\Http\Factory\Diactoros\UriFactory', 'WordPress\AiClientDependencies\Http\Factory\Guzzle\UriFactory', 'WordPress\AiClientDependencies\Http\Factory\Slim\UriFactory', 'Laminas\Diactoros\UriFactory', 'Slim\Psr7\Factory\UriFactory', 'WordPress\AiClientDependencies\HttpSoft\Message\UriFactory']];
+    public static function getCandidates($type)
+    {
+        $candidates = [];
+        if (isset(self::$classes[$type])) {
+            foreach (self::$classes[$type] as $class) {
+                $candidates[] = ['class' => $class, 'condition' => [$class]];
+            }
+        }
+        return $candidates;
+    }
+}
diff --git a/src/wp-includes/php-ai-client/third-party/Http/Discovery/Strategy/DiscoveryStrategy.php b/src/wp-includes/php-ai-client/third-party/Http/Discovery/Strategy/DiscoveryStrategy.php
new file mode 100644
index 0000000000000..d7f782db42df7
--- /dev/null
+++ b/src/wp-includes/php-ai-client/third-party/Http/Discovery/Strategy/DiscoveryStrategy.php
@@ -0,0 +1,22 @@
+<?php
+
+namespace WordPress\AiClientDependencies\Http\Discovery\Strategy;
+
+use WordPress\AiClientDependencies\Http\Discovery\Exception\StrategyUnavailableException;
+/**
+ * @author Tobias Nyholm <tobias.nyholm@gmail.com>
+ */
+interface DiscoveryStrategy
+{
+    /**
+     * Find a resource of a specific type.
+     *
+     * @param string $type
+     *
+     * @return array The return value is always an array with zero or more elements. Each
+     *               element is an array with two keys ['class' => string, 'condition' => mixed].
+     *
+     * @throws StrategyUnavailableException if we cannot use this strategy
+     */
+    public static function getCandidates($type);
+}
diff --git a/src/wp-includes/php-ai-client/third-party/Http/Discovery/Strategy/PuliBetaStrategy.php b/src/wp-includes/php-ai-client/third-party/Http/Discovery/Strategy/PuliBetaStrategy.php
new file mode 100644
index 0000000000000..bdcfc82344514
--- /dev/null
+++ b/src/wp-includes/php-ai-client/third-party/Http/Discovery/Strategy/PuliBetaStrategy.php
@@ -0,0 +1,77 @@
+<?php
+
+namespace WordPress\AiClientDependencies\Http\Discovery\Strategy;
+
+use WordPress\AiClientDependencies\Http\Discovery\ClassDiscovery;
+use WordPress\AiClientDependencies\Http\Discovery\Exception\PuliUnavailableException;
+use WordPress\AiClientDependencies\Puli\Discovery\Api\Discovery;
+use WordPress\AiClientDependencies\Puli\GeneratedPuliFactory;
+/**
+ * Find candidates using Puli.
+ *
+ * @internal
+ *
+ * @final
+ *
+ * @author David de Boer <david@ddeboer.nl>
+ * @author Márk Sági-Kazár <mark.sagikazar@gmail.com>
+ */
+class PuliBetaStrategy implements DiscoveryStrategy
+{
+    /**
+     * @var GeneratedPuliFactory
+     */
+    protected static $puliFactory;
+    /**
+     * @var Discovery
+     */
+    protected static $puliDiscovery;
+    /**
+     * @return GeneratedPuliFactory
+     *
+     * @throws PuliUnavailableException
+     */
+    private static function getPuliFactory()
+    {
+        if (null === self::$puliFactory) {
+            if (!defined('PULI_FACTORY_CLASS')) {
+                throw new PuliUnavailableException('Puli Factory is not available');
+            }
+            $puliFactoryClass = PULI_FACTORY_CLASS;
+            if (!ClassDiscovery::safeClassExists($puliFactoryClass)) {
+                throw new PuliUnavailableException('Puli Factory class does not exist');
+            }
+            self::$puliFactory = new $puliFactoryClass();
+        }
+        return self::$puliFactory;
+    }
+    /**
+     * Returns the Puli discovery layer.
+     *
+     * @return Discovery
+     *
+     * @throws PuliUnavailableException
+     */
+    private static function getPuliDiscovery()
+    {
+        if (!isset(self::$puliDiscovery)) {
+            $factory = self::getPuliFactory();
+            $repository = $factory->createRepository();
+            self::$puliDiscovery = $factory->createDiscovery($repository);
+        }
+        return self::$puliDiscovery;
+    }
+    public static function getCandidates($type)
+    {
+        $returnData = [];
+        $bindings = self::getPuliDiscovery()->findBindings($type);
+        foreach ($bindings as $binding) {
+            $condition = \true;
+            if ($binding->hasParameterValue('depends')) {
+                $condition = $binding->getParameterValue('depends');
+            }
+            $returnData[] = ['class' => $binding->getClassName(), 'condition' => $condition];
+        }
+        return $returnData;
+    }
+}
diff --git a/src/wp-includes/php-ai-client/third-party/Psr/EventDispatcher/EventDispatcherInterface.php b/src/wp-includes/php-ai-client/third-party/Psr/EventDispatcher/EventDispatcherInterface.php
new file mode 100644
index 0000000000000..4b85d3d500600
--- /dev/null
+++ b/src/wp-includes/php-ai-client/third-party/Psr/EventDispatcher/EventDispatcherInterface.php
@@ -0,0 +1,21 @@
+<?php
+
+declare (strict_types=1);
+namespace WordPress\AiClientDependencies\Psr\EventDispatcher;
+
+/**
+ * Defines a dispatcher for events.
+ */
+interface EventDispatcherInterface
+{
+    /**
+     * Provide all relevant listeners with an event to process.
+     *
+     * @param object $event
+     *   The object to process.
+     *
+     * @return object
+     *   The Event that was passed, now modified by listeners.
+     */
+    public function dispatch(object $event);
+}
diff --git a/src/wp-includes/php-ai-client/third-party/Psr/Http/Client/ClientExceptionInterface.php b/src/wp-includes/php-ai-client/third-party/Psr/Http/Client/ClientExceptionInterface.php
new file mode 100644
index 0000000000000..17fbf4caee64e
--- /dev/null
+++ b/src/wp-includes/php-ai-client/third-party/Psr/Http/Client/ClientExceptionInterface.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace WordPress\AiClientDependencies\Psr\Http\Client;
+
+/**
+ * Every HTTP client related exception MUST implement this interface.
+ */
+interface ClientExceptionInterface extends \Throwable
+{
+}
diff --git a/src/wp-includes/php-ai-client/third-party/Psr/Http/Client/ClientInterface.php b/src/wp-includes/php-ai-client/third-party/Psr/Http/Client/ClientInterface.php
new file mode 100644
index 0000000000000..ce0e9ab5dd6a4
--- /dev/null
+++ b/src/wp-includes/php-ai-client/third-party/Psr/Http/Client/ClientInterface.php
@@ -0,0 +1,19 @@
+<?php
+
+namespace WordPress\AiClientDependencies\Psr\Http\Client;
+
+use WordPress\AiClientDependencies\Psr\Http\Message\RequestInterface;
+use WordPress\AiClientDependencies\Psr\Http\Message\ResponseInterface;
+interface ClientInterface
+{
+    /**
+     * Sends a PSR-7 request and returns a PSR-7 response.
+     *
+     * @param RequestInterface $request
+     *
+     * @return ResponseInterface
+     *
+     * @throws \Psr\Http\Client\ClientExceptionInterface If an error happens while processing the request.
+     */
+    public function sendRequest(RequestInterface $request): ResponseInterface;
+}
diff --git a/src/wp-includes/php-ai-client/third-party/Psr/Http/Client/NetworkExceptionInterface.php b/src/wp-includes/php-ai-client/third-party/Psr/Http/Client/NetworkExceptionInterface.php
new file mode 100644
index 0000000000000..a1ac6048dfb61
--- /dev/null
+++ b/src/wp-includes/php-ai-client/third-party/Psr/Http/Client/NetworkExceptionInterface.php
@@ -0,0 +1,23 @@
+<?php
+
+namespace WordPress\AiClientDependencies\Psr\Http\Client;
+
+use WordPress\AiClientDependencies\Psr\Http\Message\RequestInterface;
+/**
+ * Thrown when the request cannot be completed because of network issues.
+ *
+ * There is no response object as this exception is thrown when no response has been received.
+ *
+ * Example: the target host name can not be resolved or the connection failed.
+ */
+interface NetworkExceptionInterface extends ClientExceptionInterface
+{
+    /**
+     * Returns the request.
+     *
+     * The request object MAY be a different object from the one passed to ClientInterface::sendRequest()
+     *
+     * @return RequestInterface
+     */
+    public function getRequest(): RequestInterface;
+}
diff --git a/src/wp-includes/php-ai-client/third-party/Psr/Http/Client/RequestExceptionInterface.php b/src/wp-includes/php-ai-client/third-party/Psr/Http/Client/RequestExceptionInterface.php
new file mode 100644
index 0000000000000..feeae9eb348d8
--- /dev/null
+++ b/src/wp-includes/php-ai-client/third-party/Psr/Http/Client/RequestExceptionInterface.php
@@ -0,0 +1,23 @@
+<?php
+
+namespace WordPress\AiClientDependencies\Psr\Http\Client;
+
+use WordPress\AiClientDependencies\Psr\Http\Message\RequestInterface;
+/**
+ * Exception for when a request failed.
+ *
+ * Examples:
+ *      - Request is invalid (e.g. method is missing)
+ *      - Runtime request errors (e.g. the body stream is not seekable)
+ */
+interface RequestExceptionInterface extends ClientExceptionInterface
+{
+    /**
+     * Returns the request.
+     *
+     * The request object MAY be a different object from the one passed to ClientInterface::sendRequest()
+     *
+     * @return RequestInterface
+     */
+    public function getRequest(): RequestInterface;
+}
diff --git a/src/wp-includes/php-ai-client/third-party/Psr/Http/Message/MessageInterface.php b/src/wp-includes/php-ai-client/third-party/Psr/Http/Message/MessageInterface.php
new file mode 100644
index 0000000000000..035adda2d1707
--- /dev/null
+++ b/src/wp-includes/php-ai-client/third-party/Psr/Http/Message/MessageInterface.php
@@ -0,0 +1,177 @@
+<?php
+
+namespace WordPress\AiClientDependencies\Psr\Http\Message;
+
+/**
+ * HTTP messages consist of requests from a client to a server and responses
+ * from a server to a client. This interface defines the methods common to
+ * each.
+ *
+ * Messages are considered immutable; all methods that might change state MUST
+ * be implemented such that they retain the internal state of the current
+ * message and return an instance that contains the changed state.
+ *
+ * @link http://www.ietf.org/rfc/rfc7230.txt
+ * @link http://www.ietf.org/rfc/rfc7231.txt
+ */
+interface MessageInterface
+{
+    /**
+     * Retrieves the HTTP protocol version as a string.
+     *
+     * The string MUST contain only the HTTP version number (e.g., "1.1", "1.0").
+     *
+     * @return string HTTP protocol version.
+     */
+    public function getProtocolVersion(): string;
+    /**
+     * Return an instance with the specified HTTP protocol version.
+     *
+     * The version string MUST contain only the HTTP version number (e.g.,
+     * "1.1", "1.0").
+     *
+     * This method MUST be implemented in such a way as to retain the
+     * immutability of the message, and MUST return an instance that has the
+     * new protocol version.
+     *
+     * @param string $version HTTP protocol version
+     * @return static
+     */
+    public function withProtocolVersion(string $version): MessageInterface;
+    /**
+     * Retrieves all message header values.
+     *
+     * The keys represent the header name as it will be sent over the wire, and
+     * each value is an array of strings associated with the header.
+     *
+     *     // Represent the headers as a string
+     *     foreach ($message->getHeaders() as $name => $values) {
+     *         echo $name . ": " . implode(", ", $values);
+     *     }
+     *
+     *     // Emit headers iteratively:
+     *     foreach ($message->getHeaders() as $name => $values) {
+     *         foreach ($values as $value) {
+     *             header(sprintf('%s: %s', $name, $value), false);
+     *         }
+     *     }
+     *
+     * While header names are not case-sensitive, getHeaders() will preserve the
+     * exact case in which headers were originally specified.
+     *
+     * @return string[][] Returns an associative array of the message's headers. Each
+     *     key MUST be a header name, and each value MUST be an array of strings
+     *     for that header.
+     */
+    public function getHeaders(): array;
+    /**
+     * Checks if a header exists by the given case-insensitive name.
+     *
+     * @param string $name Case-insensitive header field name.
+     * @return bool Returns true if any header names match the given header
+     *     name using a case-insensitive string comparison. Returns false if
+     *     no matching header name is found in the message.
+     */
+    public function hasHeader(string $name): bool;
+    /**
+     * Retrieves a message header value by the given case-insensitive name.
+     *
+     * This method returns an array of all the header values of the given
+     * case-insensitive header name.
+     *
+     * If the header does not appear in the message, this method MUST return an
+     * empty array.
+     *
+     * @param string $name Case-insensitive header field name.
+     * @return string[] An array of string values as provided for the given
+     *    header. If the header does not appear in the message, this method MUST
+     *    return an empty array.
+     */
+    public function getHeader(string $name): array;
+    /**
+     * Retrieves a comma-separated string of the values for a single header.
+     *
+     * This method returns all of the header values of the given
+     * case-insensitive header name as a string concatenated together using
+     * a comma.
+     *
+     * NOTE: Not all header values may be appropriately represented using
+     * comma concatenation. For such headers, use getHeader() instead
+     * and supply your own delimiter when concatenating.
+     *
+     * If the header does not appear in the message, this method MUST return
+     * an empty string.
+     *
+     * @param string $name Case-insensitive header field name.
+     * @return string A string of values as provided for the given header
+     *    concatenated together using a comma. If the header does not appear in
+     *    the message, this method MUST return an empty string.
+     */
+    public function getHeaderLine(string $name): string;
+    /**
+     * Return an instance with the provided value replacing the specified header.
+     *
+     * While header names are case-insensitive, the casing of the header will
+     * be preserved by this function, and returned from getHeaders().
+     *
+     * This method MUST be implemented in such a way as to retain the
+     * immutability of the message, and MUST return an instance that has the
+     * new and/or updated header and value.
+     *
+     * @param string $name Case-insensitive header field name.
+     * @param string|string[] $value Header value(s).
+     * @return static
+     * @throws \InvalidArgumentException for invalid header names or values.
+     */
+    public function withHeader(string $name, $value): MessageInterface;
+    /**
+     * Return an instance with the specified header appended with the given value.
+     *
+     * Existing values for the specified header will be maintained. The new
+     * value(s) will be appended to the existing list. If the header did not
+     * exist previously, it will be added.
+     *
+     * This method MUST be implemented in such a way as to retain the
+     * immutability of the message, and MUST return an instance that has the
+     * new header and/or value.
+     *
+     * @param string $name Case-insensitive header field name to add.
+     * @param string|string[] $value Header value(s).
+     * @return static
+     * @throws \InvalidArgumentException for invalid header names or values.
+     */
+    public function withAddedHeader(string $name, $value): MessageInterface;
+    /**
+     * Return an instance without the specified header.
+     *
+     * Header resolution MUST be done without case-sensitivity.
+     *
+     * This method MUST be implemented in such a way as to retain the
+     * immutability of the message, and MUST return an instance that removes
+     * the named header.
+     *
+     * @param string $name Case-insensitive header field name to remove.
+     * @return static
+     */
+    public function withoutHeader(string $name): MessageInterface;
+    /**
+     * Gets the body of the message.
+     *
+     * @return StreamInterface Returns the body as a stream.
+     */
+    public function getBody(): StreamInterface;
+    /**
+     * Return an instance with the specified message body.
+     *
+     * The body MUST be a StreamInterface object.
+     *
+     * This method MUST be implemented in such a way as to retain the
+     * immutability of the message, and MUST return a new instance that has the
+     * new body stream.
+     *
+     * @param StreamInterface $body Body.
+     * @return static
+     * @throws \InvalidArgumentException When the body is not valid.
+     */
+    public function withBody(StreamInterface $body): MessageInterface;
+}
diff --git a/src/wp-includes/php-ai-client/third-party/Psr/Http/Message/RequestFactoryInterface.php b/src/wp-includes/php-ai-client/third-party/Psr/Http/Message/RequestFactoryInterface.php
new file mode 100644
index 0000000000000..45d1c5c5bf491
--- /dev/null
+++ b/src/wp-includes/php-ai-client/third-party/Psr/Http/Message/RequestFactoryInterface.php
@@ -0,0 +1,18 @@
+<?php
+
+namespace WordPress\AiClientDependencies\Psr\Http\Message;
+
+interface RequestFactoryInterface
+{
+    /**
+     * Create a new request.
+     *
+     * @param string $method The HTTP method associated with the request.
+     * @param UriInterface|string $uri The URI associated with the request. If
+     *     the value is a string, the factory MUST create a UriInterface
+     *     instance based on it.
+     *
+     * @return RequestInterface
+     */
+    public function createRequest(string $method, $uri): RequestInterface;
+}
diff --git a/src/wp-includes/php-ai-client/third-party/Psr/Http/Message/RequestInterface.php b/src/wp-includes/php-ai-client/third-party/Psr/Http/Message/RequestInterface.php
new file mode 100644
index 0000000000000..05d4c610a7544
--- /dev/null
+++ b/src/wp-includes/php-ai-client/third-party/Psr/Http/Message/RequestInterface.php
@@ -0,0 +1,124 @@
+<?php
+
+namespace WordPress\AiClientDependencies\Psr\Http\Message;
+
+/**
+ * Representation of an outgoing, client-side request.
+ *
+ * Per the HTTP specification, this interface includes properties for
+ * each of the following:
+ *
+ * - Protocol version
+ * - HTTP method
+ * - URI
+ * - Headers
+ * - Message body
+ *
+ * During construction, implementations MUST attempt to set the Host header from
+ * a provided URI if no Host header is provided.
+ *
+ * Requests are considered immutable; all methods that might change state MUST
+ * be implemented such that they retain the internal state of the current
+ * message and return an instance that contains the changed state.
+ */
+interface RequestInterface extends MessageInterface
+{
+    /**
+     * Retrieves the message's request target.
+     *
+     * Retrieves the message's request-target either as it will appear (for
+     * clients), as it appeared at request (for servers), or as it was
+     * specified for the instance (see withRequestTarget()).
+     *
+     * In most cases, this will be the origin-form of the composed URI,
+     * unless a value was provided to the concrete implementation (see
+     * withRequestTarget() below).
+     *
+     * If no URI is available, and no request-target has been specifically
+     * provided, this method MUST return the string "/".
+     *
+     * @return string
+     */
+    public function getRequestTarget(): string;
+    /**
+     * Return an instance with the specific request-target.
+     *
+     * If the request needs a non-origin-form request-target — e.g., for
+     * specifying an absolute-form, authority-form, or asterisk-form —
+     * this method may be used to create an instance with the specified
+     * request-target, verbatim.
+     *
+     * This method MUST be implemented in such a way as to retain the
+     * immutability of the message, and MUST return an instance that has the
+     * changed request target.
+     *
+     * @link http://tools.ietf.org/html/rfc7230#section-5.3 (for the various
+     *     request-target forms allowed in request messages)
+     * @param string $requestTarget
+     * @return static
+     */
+    public function withRequestTarget(string $requestTarget): RequestInterface;
+    /**
+     * Retrieves the HTTP method of the request.
+     *
+     * @return string Returns the request method.
+     */
+    public function getMethod(): string;
+    /**
+     * Return an instance with the provided HTTP method.
+     *
+     * While HTTP method names are typically all uppercase characters, HTTP
+     * method names are case-sensitive and thus implementations SHOULD NOT
+     * modify the given string.
+     *
+     * This method MUST be implemented in such a way as to retain the
+     * immutability of the message, and MUST return an instance that has the
+     * changed request method.
+     *
+     * @param string $method Case-sensitive method.
+     * @return static
+     * @throws \InvalidArgumentException for invalid HTTP methods.
+     */
+    public function withMethod(string $method): RequestInterface;
+    /**
+     * Retrieves the URI instance.
+     *
+     * This method MUST return a UriInterface instance.
+     *
+     * @link http://tools.ietf.org/html/rfc3986#section-4.3
+     * @return UriInterface Returns a UriInterface instance
+     *     representing the URI of the request.
+     */
+    public function getUri(): UriInterface;
+    /**
+     * Returns an instance with the provided URI.
+     *
+     * This method MUST update the Host header of the returned request by
+     * default if the URI contains a host component. If the URI does not
+     * contain a host component, any pre-existing Host header MUST be carried
+     * over to the returned request.
+     *
+     * You can opt-in to preserving the original state of the Host header by
+     * setting `$preserveHost` to `true`. When `$preserveHost` is set to
+     * `true`, this method interacts with the Host header in the following ways:
+     *
+     * - If the Host header is missing or empty, and the new URI contains
+     *   a host component, this method MUST update the Host header in the returned
+     *   request.
+     * - If the Host header is missing or empty, and the new URI does not contain a
+     *   host component, this method MUST NOT update the Host header in the returned
+     *   request.
+     * - If a Host header is present and non-empty, this method MUST NOT update
+     *   the Host header in the returned request.
+     *
+     * This method MUST be implemented in such a way as to retain the
+     * immutability of the message, and MUST return an instance that has the
+     * new UriInterface instance.
+     *
+     * @link http://tools.ietf.org/html/rfc3986#section-4.3
+     * @param UriInterface $uri New request URI to use.
+     * @param bool $preserveHost Preserve the original state of the Host header.
+     * @return static
+     */
+    public function withUri(UriInterface $uri, bool $preserveHost = \false): RequestInterface;
+}
diff --git a/src/wp-includes/php-ai-client/third-party/Psr/Http/Message/ResponseFactoryInterface.php b/src/wp-includes/php-ai-client/third-party/Psr/Http/Message/ResponseFactoryInterface.php
new file mode 100644
index 0000000000000..53b7ec0b2640e
--- /dev/null
+++ b/src/wp-includes/php-ai-client/third-party/Psr/Http/Message/ResponseFactoryInterface.php
@@ -0,0 +1,18 @@
+<?php
+
+namespace WordPress\AiClientDependencies\Psr\Http\Message;
+
+interface ResponseFactoryInterface
+{
+    /**
+     * Create a new response.
+     *
+     * @param int $code HTTP status code; defaults to 200
+     * @param string $reasonPhrase Reason phrase to associate with status code
+     *     in generated response; if none is provided implementations MAY use
+     *     the defaults as suggested in the HTTP specification.
+     *
+     * @return ResponseInterface
+     */
+    public function createResponse(int $code = 200, string $reasonPhrase = ''): ResponseInterface;
+}
diff --git a/src/wp-includes/php-ai-client/third-party/Psr/Http/Message/ResponseInterface.php b/src/wp-includes/php-ai-client/third-party/Psr/Http/Message/ResponseInterface.php
new file mode 100644
index 0000000000000..7b8c654c8246f
--- /dev/null
+++ b/src/wp-includes/php-ai-client/third-party/Psr/Http/Message/ResponseInterface.php
@@ -0,0 +1,66 @@
+<?php
+
+namespace WordPress\AiClientDependencies\Psr\Http\Message;
+
+/**
+ * Representation of an outgoing, server-side response.
+ *
+ * Per the HTTP specification, this interface includes properties for
+ * each of the following:
+ *
+ * - Protocol version
+ * - Status code and reason phrase
+ * - Headers
+ * - Message body
+ *
+ * Responses are considered immutable; all methods that might change state MUST
+ * be implemented such that they retain the internal state of the current
+ * message and return an instance that contains the changed state.
+ */
+interface ResponseInterface extends MessageInterface
+{
+    /**
+     * Gets the response status code.
+     *
+     * The status code is a 3-digit integer result code of the server's attempt
+     * to understand and satisfy the request.
+     *
+     * @return int Status code.
+     */
+    public function getStatusCode(): int;
+    /**
+     * Return an instance with the specified status code and, optionally, reason phrase.
+     *
+     * If no reason phrase is specified, implementations MAY choose to default
+     * to the RFC 7231 or IANA recommended reason phrase for the response's
+     * status code.
+     *
+     * This method MUST be implemented in such a way as to retain the
+     * immutability of the message, and MUST return an instance that has the
+     * updated status and reason phrase.
+     *
+     * @link http://tools.ietf.org/html/rfc7231#section-6
+     * @link http://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml
+     * @param int $code The 3-digit integer result code to set.
+     * @param string $reasonPhrase The reason phrase to use with the
+     *     provided status code; if none is provided, implementations MAY
+     *     use the defaults as suggested in the HTTP specification.
+     * @return static
+     * @throws \InvalidArgumentException For invalid status code arguments.
+     */
+    public function withStatus(int $code, string $reasonPhrase = ''): ResponseInterface;
+    /**
+     * Gets the response reason phrase associated with the status code.
+     *
+     * Because a reason phrase is not a required element in a response
+     * status line, the reason phrase value MAY be null. Implementations MAY
+     * choose to return the default RFC 7231 recommended reason phrase (or those
+     * listed in the IANA HTTP Status Code Registry) for the response's
+     * status code.
+     *
+     * @link http://tools.ietf.org/html/rfc7231#section-6
+     * @link http://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml
+     * @return string Reason phrase; must return an empty string if none present.
+     */
+    public function getReasonPhrase(): string;
+}
diff --git a/src/wp-includes/php-ai-client/third-party/Psr/Http/Message/StreamFactoryInterface.php b/src/wp-includes/php-ai-client/third-party/Psr/Http/Message/StreamFactoryInterface.php
new file mode 100644
index 0000000000000..d28d1cb413901
--- /dev/null
+++ b/src/wp-includes/php-ai-client/third-party/Psr/Http/Message/StreamFactoryInterface.php
@@ -0,0 +1,43 @@
+<?php
+
+namespace WordPress\AiClientDependencies\Psr\Http\Message;
+
+interface StreamFactoryInterface
+{
+    /**
+     * Create a new stream from a string.
+     *
+     * The stream SHOULD be created with a temporary resource.
+     *
+     * @param string $content String content with which to populate the stream.
+     *
+     * @return StreamInterface
+     */
+    public function createStream(string $content = ''): StreamInterface;
+    /**
+     * Create a stream from an existing file.
+     *
+     * The file MUST be opened using the given mode, which may be any mode
+     * supported by the `fopen` function.
+     *
+     * The `$filename` MAY be any string supported by `fopen()`.
+     *
+     * @param string $filename Filename or stream URI to use as basis of stream.
+     * @param string $mode Mode with which to open the underlying filename/stream.
+     *
+     * @return StreamInterface
+     * @throws \RuntimeException If the file cannot be opened.
+     * @throws \InvalidArgumentException If the mode is invalid.
+     */
+    public function createStreamFromFile(string $filename, string $mode = 'r'): StreamInterface;
+    /**
+     * Create a new stream from an existing resource.
+     *
+     * The stream MUST be readable and may be writable.
+     *
+     * @param resource $resource PHP resource to use as basis of stream.
+     *
+     * @return StreamInterface
+     */
+    public function createStreamFromResource($resource): StreamInterface;
+}
diff --git a/src/wp-includes/php-ai-client/third-party/Psr/Http/Message/StreamInterface.php b/src/wp-includes/php-ai-client/third-party/Psr/Http/Message/StreamInterface.php
new file mode 100644
index 0000000000000..e825c68ee76c1
--- /dev/null
+++ b/src/wp-includes/php-ai-client/third-party/Psr/Http/Message/StreamInterface.php
@@ -0,0 +1,144 @@
+<?php
+
+namespace WordPress\AiClientDependencies\Psr\Http\Message;
+
+/**
+ * Describes a data stream.
+ *
+ * Typically, an instance will wrap a PHP stream; this interface provides
+ * a wrapper around the most common operations, including serialization of
+ * the entire stream to a string.
+ */
+interface StreamInterface
+{
+    /**
+     * Reads all data from the stream into a string, from the beginning to end.
+     *
+     * This method MUST attempt to seek to the beginning of the stream before
+     * reading data and read the stream until the end is reached.
+     *
+     * Warning: This could attempt to load a large amount of data into memory.
+     *
+     * This method MUST NOT raise an exception in order to conform with PHP's
+     * string casting operations.
+     *
+     * @see http://php.net/manual/en/language.oop5.magic.php#object.tostring
+     * @return string
+     */
+    public function __toString(): string;
+    /**
+     * Closes the stream and any underlying resources.
+     *
+     * @return void
+     */
+    public function close(): void;
+    /**
+     * Separates any underlying resources from the stream.
+     *
+     * After the stream has been detached, the stream is in an unusable state.
+     *
+     * @return resource|null Underlying PHP stream, if any
+     */
+    public function detach();
+    /**
+     * Get the size of the stream if known.
+     *
+     * @return int|null Returns the size in bytes if known, or null if unknown.
+     */
+    public function getSize(): ?int;
+    /**
+     * Returns the current position of the file read/write pointer
+     *
+     * @return int Position of the file pointer
+     * @throws \RuntimeException on error.
+     */
+    public function tell(): int;
+    /**
+     * Returns true if the stream is at the end of the stream.
+     *
+     * @return bool
+     */
+    public function eof(): bool;
+    /**
+     * Returns whether or not the stream is seekable.
+     *
+     * @return bool
+     */
+    public function isSeekable(): bool;
+    /**
+     * Seek to a position in the stream.
+     *
+     * @link http://www.php.net/manual/en/function.fseek.php
+     * @param int $offset Stream offset
+     * @param int $whence Specifies how the cursor position will be calculated
+     *     based on the seek offset. Valid values are identical to the built-in
+     *     PHP $whence values for `fseek()`.  SEEK_SET: Set position equal to
+     *     offset bytes SEEK_CUR: Set position to current location plus offset
+     *     SEEK_END: Set position to end-of-stream plus offset.
+     * @throws \RuntimeException on failure.
+     */
+    public function seek(int $offset, int $whence = \SEEK_SET): void;
+    /**
+     * Seek to the beginning of the stream.
+     *
+     * If the stream is not seekable, this method will raise an exception;
+     * otherwise, it will perform a seek(0).
+     *
+     * @see seek()
+     * @link http://www.php.net/manual/en/function.fseek.php
+     * @throws \RuntimeException on failure.
+     */
+    public function rewind(): void;
+    /**
+     * Returns whether or not the stream is writable.
+     *
+     * @return bool
+     */
+    public function isWritable(): bool;
+    /**
+     * Write data to the stream.
+     *
+     * @param string $string The string that is to be written.
+     * @return int Returns the number of bytes written to the stream.
+     * @throws \RuntimeException on failure.
+     */
+    public function write(string $string): int;
+    /**
+     * Returns whether or not the stream is readable.
+     *
+     * @return bool
+     */
+    public function isReadable(): bool;
+    /**
+     * Read data from the stream.
+     *
+     * @param int $length Read up to $length bytes from the object and return
+     *     them. Fewer than $length bytes may be returned if underlying stream
+     *     call returns fewer bytes.
+     * @return string Returns the data read from the stream, or an empty string
+     *     if no bytes are available.
+     * @throws \RuntimeException if an error occurs.
+     */
+    public function read(int $length): string;
+    /**
+     * Returns the remaining contents in a string
+     *
+     * @return string
+     * @throws \RuntimeException if unable to read or an error occurs while
+     *     reading.
+     */
+    public function getContents(): string;
+    /**
+     * Get stream metadata as an associative array or retrieve a specific key.
+     *
+     * The keys returned are identical to the keys returned from PHP's
+     * stream_get_meta_data() function.
+     *
+     * @link http://php.net/manual/en/function.stream-get-meta-data.php
+     * @param string|null $key Specific metadata to retrieve.
+     * @return array|mixed|null Returns an associative array if no key is
+     *     provided. Returns a specific key value if a key is provided and the
+     *     value is found, or null if the key is not found.
+     */
+    public function getMetadata(?string $key = null);
+}
diff --git a/src/wp-includes/php-ai-client/third-party/Psr/Http/Message/UriFactoryInterface.php b/src/wp-includes/php-ai-client/third-party/Psr/Http/Message/UriFactoryInterface.php
new file mode 100644
index 0000000000000..db463d5b13b34
--- /dev/null
+++ b/src/wp-includes/php-ai-client/third-party/Psr/Http/Message/UriFactoryInterface.php
@@ -0,0 +1,17 @@
+<?php
+
+namespace WordPress\AiClientDependencies\Psr\Http\Message;
+
+interface UriFactoryInterface
+{
+    /**
+     * Create a new URI.
+     *
+     * @param string $uri
+     *
+     * @return UriInterface
+     *
+     * @throws \InvalidArgumentException If the given URI cannot be parsed.
+     */
+    public function createUri(string $uri = ''): UriInterface;
+}
diff --git a/src/wp-includes/php-ai-client/third-party/Psr/Http/Message/UriInterface.php b/src/wp-includes/php-ai-client/third-party/Psr/Http/Message/UriInterface.php
new file mode 100644
index 0000000000000..84d69738cc0ef
--- /dev/null
+++ b/src/wp-includes/php-ai-client/third-party/Psr/Http/Message/UriInterface.php
@@ -0,0 +1,309 @@
+<?php
+
+namespace WordPress\AiClientDependencies\Psr\Http\Message;
+
+/**
+ * Value object representing a URI.
+ *
+ * This interface is meant to represent URIs according to RFC 3986 and to
+ * provide methods for most common operations. Additional functionality for
+ * working with URIs can be provided on top of the interface or externally.
+ * Its primary use is for HTTP requests, but may also be used in other
+ * contexts.
+ *
+ * Instances of this interface are considered immutable; all methods that
+ * might change state MUST be implemented such that they retain the internal
+ * state of the current instance and return an instance that contains the
+ * changed state.
+ *
+ * Typically the Host header will be also be present in the request message.
+ * For server-side requests, the scheme will typically be discoverable in the
+ * server parameters.
+ *
+ * @link http://tools.ietf.org/html/rfc3986 (the URI specification)
+ */
+interface UriInterface
+{
+    /**
+     * Retrieve the scheme component of the URI.
+     *
+     * If no scheme is present, this method MUST return an empty string.
+     *
+     * The value returned MUST be normalized to lowercase, per RFC 3986
+     * Section 3.1.
+     *
+     * The trailing ":" character is not part of the scheme and MUST NOT be
+     * added.
+     *
+     * @see https://tools.ietf.org/html/rfc3986#section-3.1
+     * @return string The URI scheme.
+     */
+    public function getScheme(): string;
+    /**
+     * Retrieve the authority component of the URI.
+     *
+     * If no authority information is present, this method MUST return an empty
+     * string.
+     *
+     * The authority syntax of the URI is:
+     *
+     * <pre>
+     * [user-info@]host[:port]
+     * </pre>
+     *
+     * If the port component is not set or is the standard port for the current
+     * scheme, it SHOULD NOT be included.
+     *
+     * @see https://tools.ietf.org/html/rfc3986#section-3.2
+     * @return string The URI authority, in "[user-info@]host[:port]" format.
+     */
+    public function getAuthority(): string;
+    /**
+     * Retrieve the user information component of the URI.
+     *
+     * If no user information is present, this method MUST return an empty
+     * string.
+     *
+     * If a user is present in the URI, this will return that value;
+     * additionally, if the password is also present, it will be appended to the
+     * user value, with a colon (":") separating the values.
+     *
+     * The trailing "@" character is not part of the user information and MUST
+     * NOT be added.
+     *
+     * @return string The URI user information, in "username[:password]" format.
+     */
+    public function getUserInfo(): string;
+    /**
+     * Retrieve the host component of the URI.
+     *
+     * If no host is present, this method MUST return an empty string.
+     *
+     * The value returned MUST be normalized to lowercase, per RFC 3986
+     * Section 3.2.2.
+     *
+     * @see http://tools.ietf.org/html/rfc3986#section-3.2.2
+     * @return string The URI host.
+     */
+    public function getHost(): string;
+    /**
+     * Retrieve the port component of the URI.
+     *
+     * If a port is present, and it is non-standard for the current scheme,
+     * this method MUST return it as an integer. If the port is the standard port
+     * used with the current scheme, this method SHOULD return null.
+     *
+     * If no port is present, and no scheme is present, this method MUST return
+     * a null value.
+     *
+     * If no port is present, but a scheme is present, this method MAY return
+     * the standard port for that scheme, but SHOULD return null.
+     *
+     * @return null|int The URI port.
+     */
+    public function getPort(): ?int;
+    /**
+     * Retrieve the path component of the URI.
+     *
+     * The path can either be empty or absolute (starting with a slash) or
+     * rootless (not starting with a slash). Implementations MUST support all
+     * three syntaxes.
+     *
+     * Normally, the empty path "" and absolute path "/" are considered equal as
+     * defined in RFC 7230 Section 2.7.3. But this method MUST NOT automatically
+     * do this normalization because in contexts with a trimmed base path, e.g.
+     * the front controller, this difference becomes significant. It's the task
+     * of the user to handle both "" and "/".
+     *
+     * The value returned MUST be percent-encoded, but MUST NOT double-encode
+     * any characters. To determine what characters to encode, please refer to
+     * RFC 3986, Sections 2 and 3.3.
+     *
+     * As an example, if the value should include a slash ("/") not intended as
+     * delimiter between path segments, that value MUST be passed in encoded
+     * form (e.g., "%2F") to the instance.
+     *
+     * @see https://tools.ietf.org/html/rfc3986#section-2
+     * @see https://tools.ietf.org/html/rfc3986#section-3.3
+     * @return string The URI path.
+     */
+    public function getPath(): string;
+    /**
+     * Retrieve the query string of the URI.
+     *
+     * If no query string is present, this method MUST return an empty string.
+     *
+     * The leading "?" character is not part of the query and MUST NOT be
+     * added.
+     *
+     * The value returned MUST be percent-encoded, but MUST NOT double-encode
+     * any characters. To determine what characters to encode, please refer to
+     * RFC 3986, Sections 2 and 3.4.
+     *
+     * As an example, if a value in a key/value pair of the query string should
+     * include an ampersand ("&") not intended as a delimiter between values,
+     * that value MUST be passed in encoded form (e.g., "%26") to the instance.
+     *
+     * @see https://tools.ietf.org/html/rfc3986#section-2
+     * @see https://tools.ietf.org/html/rfc3986#section-3.4
+     * @return string The URI query string.
+     */
+    public function getQuery(): string;
+    /**
+     * Retrieve the fragment component of the URI.
+     *
+     * If no fragment is present, this method MUST return an empty string.
+     *
+     * The leading "#" character is not part of the fragment and MUST NOT be
+     * added.
+     *
+     * The value returned MUST be percent-encoded, but MUST NOT double-encode
+     * any characters. To determine what characters to encode, please refer to
+     * RFC 3986, Sections 2 and 3.5.
+     *
+     * @see https://tools.ietf.org/html/rfc3986#section-2
+     * @see https://tools.ietf.org/html/rfc3986#section-3.5
+     * @return string The URI fragment.
+     */
+    public function getFragment(): string;
+    /**
+     * Return an instance with the specified scheme.
+     *
+     * This method MUST retain the state of the current instance, and return
+     * an instance that contains the specified scheme.
+     *
+     * Implementations MUST support the schemes "http" and "https" case
+     * insensitively, and MAY accommodate other schemes if required.
+     *
+     * An empty scheme is equivalent to removing the scheme.
+     *
+     * @param string $scheme The scheme to use with the new instance.
+     * @return static A new instance with the specified scheme.
+     * @throws \InvalidArgumentException for invalid or unsupported schemes.
+     */
+    public function withScheme(string $scheme): UriInterface;
+    /**
+     * Return an instance with the specified user information.
+     *
+     * This method MUST retain the state of the current instance, and return
+     * an instance that contains the specified user information.
+     *
+     * Password is optional, but the user information MUST include the
+     * user; an empty string for the user is equivalent to removing user
+     * information.
+     *
+     * @param string $user The user name to use for authority.
+     * @param null|string $password The password associated with $user.
+     * @return static A new instance with the specified user information.
+     */
+    public function withUserInfo(string $user, ?string $password = null): UriInterface;
+    /**
+     * Return an instance with the specified host.
+     *
+     * This method MUST retain the state of the current instance, and return
+     * an instance that contains the specified host.
+     *
+     * An empty host value is equivalent to removing the host.
+     *
+     * @param string $host The hostname to use with the new instance.
+     * @return static A new instance with the specified host.
+     * @throws \InvalidArgumentException for invalid hostnames.
+     */
+    public function withHost(string $host): UriInterface;
+    /**
+     * Return an instance with the specified port.
+     *
+     * This method MUST retain the state of the current instance, and return
+     * an instance that contains the specified port.
+     *
+     * Implementations MUST raise an exception for ports outside the
+     * established TCP and UDP port ranges.
+     *
+     * A null value provided for the port is equivalent to removing the port
+     * information.
+     *
+     * @param null|int $port The port to use with the new instance; a null value
+     *     removes the port information.
+     * @return static A new instance with the specified port.
+     * @throws \InvalidArgumentException for invalid ports.
+     */
+    public function withPort(?int $port): UriInterface;
+    /**
+     * Return an instance with the specified path.
+     *
+     * This method MUST retain the state of the current instance, and return
+     * an instance that contains the specified path.
+     *
+     * The path can either be empty or absolute (starting with a slash) or
+     * rootless (not starting with a slash). Implementations MUST support all
+     * three syntaxes.
+     *
+     * If the path is intended to be domain-relative rather than path relative then
+     * it must begin with a slash ("/"). Paths not starting with a slash ("/")
+     * are assumed to be relative to some base path known to the application or
+     * consumer.
+     *
+     * Users can provide both encoded and decoded path characters.
+     * Implementations ensure the correct encoding as outlined in getPath().
+     *
+     * @param string $path The path to use with the new instance.
+     * @return static A new instance with the specified path.
+     * @throws \InvalidArgumentException for invalid paths.
+     */
+    public function withPath(string $path): UriInterface;
+    /**
+     * Return an instance with the specified query string.
+     *
+     * This method MUST retain the state of the current instance, and return
+     * an instance that contains the specified query string.
+     *
+     * Users can provide both encoded and decoded query characters.
+     * Implementations ensure the correct encoding as outlined in getQuery().
+     *
+     * An empty query string value is equivalent to removing the query string.
+     *
+     * @param string $query The query string to use with the new instance.
+     * @return static A new instance with the specified query string.
+     * @throws \InvalidArgumentException for invalid query strings.
+     */
+    public function withQuery(string $query): UriInterface;
+    /**
+     * Return an instance with the specified URI fragment.
+     *
+     * This method MUST retain the state of the current instance, and return
+     * an instance that contains the specified URI fragment.
+     *
+     * Users can provide both encoded and decoded fragment characters.
+     * Implementations ensure the correct encoding as outlined in getFragment().
+     *
+     * An empty fragment value is equivalent to removing the fragment.
+     *
+     * @param string $fragment The fragment to use with the new instance.
+     * @return static A new instance with the specified fragment.
+     */
+    public function withFragment(string $fragment): UriInterface;
+    /**
+     * Return the string representation as a URI reference.
+     *
+     * Depending on which components of the URI are present, the resulting
+     * string is either a full URI or relative reference according to RFC 3986,
+     * Section 4.1. The method concatenates the various components of the URI,
+     * using the appropriate delimiters:
+     *
+     * - If a scheme is present, it MUST be suffixed by ":".
+     * - If an authority is present, it MUST be prefixed by "//".
+     * - The path can be concatenated without delimiters. But there are two
+     *   cases where the path has to be adjusted to make the URI reference
+     *   valid as PHP does not allow to throw an exception in __toString():
+     *     - If the path is rootless and an authority is present, the path MUST
+     *       be prefixed by "/".
+     *     - If the path is starting with more than one "/" and no authority is
+     *       present, the starting slashes MUST be reduced to one.
+     * - If a query is present, it MUST be prefixed by "?".
+     * - If a fragment is present, it MUST be prefixed by "#".
+     *
+     * @see http://tools.ietf.org/html/rfc3986#section-4.1
+     * @return string
+     */
+    public function __toString(): string;
+}
diff --git a/src/wp-includes/php-ai-client/third-party/Psr/SimpleCache/CacheInterface.php b/src/wp-includes/php-ai-client/third-party/Psr/SimpleCache/CacheInterface.php
new file mode 100644
index 0000000000000..b7fd4bf5b046d
--- /dev/null
+++ b/src/wp-includes/php-ai-client/third-party/Psr/SimpleCache/CacheInterface.php
@@ -0,0 +1,107 @@
+<?php
+
+namespace WordPress\AiClientDependencies\Psr\SimpleCache;
+
+interface CacheInterface
+{
+    /**
+     * Fetches a value from the cache.
+     *
+     * @param string $key     The unique key of this item in the cache.
+     * @param mixed  $default Default value to return if the key does not exist.
+     *
+     * @return mixed The value of the item from the cache, or $default in case of cache miss.
+     *
+     * @throws \Psr\SimpleCache\InvalidArgumentException
+     *   MUST be thrown if the $key string is not a legal value.
+     */
+    public function get($key, $default = null);
+    /**
+     * Persists data in the cache, uniquely referenced by a key with an optional expiration TTL time.
+     *
+     * @param string                 $key   The key of the item to store.
+     * @param mixed                  $value The value of the item to store, must be serializable.
+     * @param null|int|\DateInterval $ttl   Optional. The TTL value of this item. If no value is sent and
+     *                                      the driver supports TTL then the library may set a default value
+     *                                      for it or let the driver take care of that.
+     *
+     * @return bool True on success and false on failure.
+     *
+     * @throws \Psr\SimpleCache\InvalidArgumentException
+     *   MUST be thrown if the $key string is not a legal value.
+     */
+    public function set($key, $value, $ttl = null);
+    /**
+     * Delete an item from the cache by its unique key.
+     *
+     * @param string $key The unique cache key of the item to delete.
+     *
+     * @return bool True if the item was successfully removed. False if there was an error.
+     *
+     * @throws \Psr\SimpleCache\InvalidArgumentException
+     *   MUST be thrown if the $key string is not a legal value.
+     */
+    public function delete($key);
+    /**
+     * Wipes clean the entire cache's keys.
+     *
+     * @return bool True on success and false on failure.
+     */
+    public function clear();
+    /**
+     * Obtains multiple cache items by their unique keys.
+     *
+     * @param iterable $keys    A list of keys that can obtained in a single operation.
+     * @param mixed    $default Default value to return for keys that do not exist.
+     *
+     * @return iterable A list of key => value pairs. Cache keys that do not exist or are stale will have $default as value.
+     *
+     * @throws \Psr\SimpleCache\InvalidArgumentException
+     *   MUST be thrown if $keys is neither an array nor a Traversable,
+     *   or if any of the $keys are not a legal value.
+     */
+    public function getMultiple($keys, $default = null);
+    /**
+     * Persists a set of key => value pairs in the cache, with an optional TTL.
+     *
+     * @param iterable               $values A list of key => value pairs for a multiple-set operation.
+     * @param null|int|\DateInterval $ttl    Optional. The TTL value of this item. If no value is sent and
+     *                                       the driver supports TTL then the library may set a default value
+     *                                       for it or let the driver take care of that.
+     *
+     * @return bool True on success and false on failure.
+     *
+     * @throws \Psr\SimpleCache\InvalidArgumentException
+     *   MUST be thrown if $values is neither an array nor a Traversable,
+     *   or if any of the $values are not a legal value.
+     */
+    public function setMultiple($values, $ttl = null);
+    /**
+     * Deletes multiple cache items in a single operation.
+     *
+     * @param iterable $keys A list of string-based keys to be deleted.
+     *
+     * @return bool True if the items were successfully removed. False if there was an error.
+     *
+     * @throws \Psr\SimpleCache\InvalidArgumentException
+     *   MUST be thrown if $keys is neither an array nor a Traversable,
+     *   or if any of the $keys are not a legal value.
+     */
+    public function deleteMultiple($keys);
+    /**
+     * Determines whether an item is present in the cache.
+     *
+     * NOTE: It is recommended that has() is only to be used for cache warming type purposes
+     * and not to be used within your live applications operations for get/set, as this method
+     * is subject to a race condition where your has() will return true and immediately after,
+     * another script can remove it making the state of your app out of date.
+     *
+     * @param string $key The cache item key.
+     *
+     * @return bool
+     *
+     * @throws \Psr\SimpleCache\InvalidArgumentException
+     *   MUST be thrown if the $key string is not a legal value.
+     */
+    public function has($key);
+}
diff --git a/src/wp-settings.php b/src/wp-settings.php
index 60c220100f539..30bf33b753be7 100644
--- a/src/wp-settings.php
+++ b/src/wp-settings.php
@@ -286,6 +286,31 @@
 require ABSPATH . WPINC . '/class-wp-http-response.php';
 require ABSPATH . WPINC . '/class-wp-http-requests-response.php';
 require ABSPATH . WPINC . '/class-wp-http-requests-hooks.php';
+require ABSPATH . WPINC . '/php-ai-client/autoload.php';
+
+// WP AI Client - PSR-7 implementations.
+require ABSPATH . WPINC . '/ai-client-utils/class-wp-ai-client-psr7-stream.php';
+require ABSPATH . WPINC . '/ai-client-utils/class-wp-ai-client-psr7-uri.php';
+require ABSPATH . WPINC . '/ai-client-utils/class-wp-ai-client-psr7-request.php';
+require ABSPATH . WPINC . '/ai-client-utils/class-wp-ai-client-psr7-response.php';
+require ABSPATH . WPINC . '/ai-client-utils/class-wp-ai-client-psr17-factory.php';
+
+// WP AI Client - HTTP transport and infrastructure.
+require ABSPATH . WPINC . '/ai-client-utils/class-wp-ai-client-http-client.php';
+require ABSPATH . WPINC . '/ai-client-utils/class-wp-ai-client-cache.php';
+require ABSPATH . WPINC . '/ai-client-utils/class-wp-ai-client-discovery-strategy.php';
+require ABSPATH . WPINC . '/ai-client-utils/class-wp-ai-client-event-dispatcher.php';
+
+// WP AI Client - Abilities and prompt builder.
+require ABSPATH . WPINC . '/ai-client-utils/class-wp-ai-client-ability-function-resolver.php';
+require ABSPATH . WPINC . '/class-wp-ai-client-prompt-builder.php';
+require ABSPATH . WPINC . '/ai-client.php';
+
+// WP AI Client - Initialization.
+WP_AI_Client_Discovery_Strategy::init();
+WordPress\AiClient\AiClient::setCache( new WP_AI_Client_Cache() );
+WordPress\AiClient\AiClient::setEventDispatcher( new WP_AI_Client_Event_Dispatcher() );
+
 require ABSPATH . WPINC . '/widgets.php';
 require ABSPATH . WPINC . '/class-wp-widget.php';
 require ABSPATH . WPINC . '/class-wp-widget-factory.php';
diff --git a/tests/phpunit/includes/wp-ai-client-mock-event.php b/tests/phpunit/includes/wp-ai-client-mock-event.php
new file mode 100644
index 0000000000000..6880da306d336
--- /dev/null
+++ b/tests/phpunit/includes/wp-ai-client-mock-event.php
@@ -0,0 +1,17 @@
+<?php
+/**
+ * Mock Event for testing.
+ *
+ * @package WordPress
+ * @subpackage AI
+ */
+
+/**
+ * Mock event class for testing the WP_AI_Client_Event_Dispatcher.
+ *
+ * The class name ends with 'Event' to test the suffix stripping behavior.
+ *
+ * @since 7.0.0
+ */
+class WP_AI_Client_Mock_Event {
+}
diff --git a/tests/phpunit/includes/wp-ai-client-mock-model-creation-trait.php b/tests/phpunit/includes/wp-ai-client-mock-model-creation-trait.php
new file mode 100644
index 0000000000000..aa3baf4b9ce0c
--- /dev/null
+++ b/tests/phpunit/includes/wp-ai-client-mock-model-creation-trait.php
@@ -0,0 +1,445 @@
+<?php
+/**
+ * Trait for creating mock models for testing.
+ *
+ * @package WordPress
+ * @subpackage AI
+ */
+
+use WordPress\AiClient\Messages\DTO\MessagePart;
+use WordPress\AiClient\Messages\DTO\ModelMessage;
+use WordPress\AiClient\Providers\DTO\ProviderMetadata;
+use WordPress\AiClient\Providers\Enums\ProviderTypeEnum;
+use WordPress\AiClient\Providers\Models\Contracts\ModelInterface;
+use WordPress\AiClient\Providers\Models\DTO\ModelConfig;
+use WordPress\AiClient\Providers\Models\DTO\ModelMetadata;
+use WordPress\AiClient\Providers\Models\Enums\CapabilityEnum;
+use WordPress\AiClient\Providers\Models\ImageGeneration\Contracts\ImageGenerationModelInterface;
+use WordPress\AiClient\Providers\Models\SpeechGeneration\Contracts\SpeechGenerationModelInterface;
+use WordPress\AiClient\Providers\Models\TextGeneration\Contracts\TextGenerationModelInterface;
+use WordPress\AiClient\Providers\Models\TextToSpeechConversion\Contracts\TextToSpeechConversionModelInterface;
+use WordPress\AiClient\Results\DTO\Candidate;
+use WordPress\AiClient\Results\DTO\GenerativeAiResult;
+use WordPress\AiClient\Results\DTO\TokenUsage;
+use WordPress\AiClient\Results\Enums\FinishReasonEnum;
+
+/**
+ * Trait providing shared mock model creation methods for testing.
+ *
+ * @since 7.0.0
+ */
+trait WP_AI_Client_Mock_Model_Creation_Trait {
+
+	/**
+	 * Creates a test GenerativeAiResult for testing purposes.
+	 *
+	 * @param string $content Optional content for the response.
+	 * @return GenerativeAiResult
+	 */
+	protected function create_test_result( string $content = 'Test response' ): GenerativeAiResult {
+		$candidate   = new Candidate(
+			new ModelMessage( array( new MessagePart( $content ) ) ),
+			FinishReasonEnum::stop()
+		);
+		$token_usage = new TokenUsage( 10, 20, 30 );
+
+		$provider_metadata = new ProviderMetadata(
+			'mock',
+			'Mock Provider',
+			ProviderTypeEnum::cloud()
+		);
+		$model_metadata    = new ModelMetadata(
+			'mock-model',
+			'Mock Model',
+			array(),
+			array()
+		);
+
+		return new GenerativeAiResult(
+			'test-result-id',
+			array( $candidate ),
+			$token_usage,
+			$provider_metadata,
+			$model_metadata
+		);
+	}
+
+	/**
+	 * Creates a test model metadata instance for text generation.
+	 *
+	 * @param string $id   Optional model ID.
+	 * @param string $name Optional model name.
+	 * @return ModelMetadata
+	 */
+	protected function create_test_text_model_metadata(
+		string $id = 'test-text-model',
+		string $name = 'Test Text Model'
+	): ModelMetadata {
+		return new ModelMetadata(
+			$id,
+			$name,
+			array( CapabilityEnum::textGeneration() ),
+			array()
+		);
+	}
+
+	/**
+	 * Creates a test model metadata instance for image generation.
+	 *
+	 * @param string $id   Optional model ID.
+	 * @param string $name Optional model name.
+	 * @return ModelMetadata
+	 */
+	protected function create_test_image_model_metadata(
+		string $id = 'test-image-model',
+		string $name = 'Test Image Model'
+	): ModelMetadata {
+		return new ModelMetadata(
+			$id,
+			$name,
+			array( CapabilityEnum::imageGeneration() ),
+			array()
+		);
+	}
+
+	/**
+	 * Creates a test model metadata instance for speech generation.
+	 *
+	 * @param string $id   Optional model ID.
+	 * @param string $name Optional model name.
+	 * @return ModelMetadata
+	 */
+	protected function create_test_speech_model_metadata(
+		string $id = 'test-speech-model',
+		string $name = 'Test Speech Model'
+	): ModelMetadata {
+		return new ModelMetadata(
+			$id,
+			$name,
+			array( CapabilityEnum::speechGeneration() ),
+			array()
+		);
+	}
+
+	/**
+	 * Creates a test model metadata instance for text-to-speech conversion.
+	 *
+	 * @param string $id   Optional model ID.
+	 * @param string $name Optional model name.
+	 * @return ModelMetadata
+	 */
+	protected function create_test_text_to_speech_model_metadata(
+		string $id = 'test-text-to-speech-model',
+		string $name = 'Test Text-to-Speech Model'
+	): ModelMetadata {
+		return new ModelMetadata(
+			$id,
+			$name,
+			array( CapabilityEnum::textToSpeechConversion() ),
+			array()
+		);
+	}
+
+	/**
+	 * Creates a mock text generation model using anonymous class.
+	 *
+	 * @param GenerativeAiResult $result   The result to return from generation.
+	 * @param ModelMetadata|null $metadata Optional metadata.
+	 * @return ModelInterface&TextGenerationModelInterface The mock model.
+	 */
+	protected function create_mock_text_generation_model(
+		GenerativeAiResult $result,
+		?ModelMetadata $metadata = null
+	): ModelInterface {
+		$metadata = $metadata ?? $this->create_test_text_model_metadata();
+
+		$provider_metadata = new ProviderMetadata(
+			'mock',
+			'Mock Provider',
+			ProviderTypeEnum::cloud()
+		);
+
+		return new class( $metadata, $provider_metadata, $result ) implements ModelInterface, TextGenerationModelInterface {
+
+			private ModelMetadata $metadata;
+			private ProviderMetadata $provider_metadata;
+			private GenerativeAiResult $result;
+			private ModelConfig $config;
+
+			public function __construct(
+				ModelMetadata $metadata,
+				ProviderMetadata $provider_metadata,
+				GenerativeAiResult $result
+			) {
+				$this->metadata          = $metadata;
+				$this->provider_metadata = $provider_metadata;
+				$this->result            = $result;
+				$this->config            = new ModelConfig();
+			}
+
+			public function metadata(): ModelMetadata {
+				return $this->metadata;
+			}
+
+			public function providerMetadata(): ProviderMetadata {
+				return $this->provider_metadata;
+			}
+
+			public function setConfig( ModelConfig $config ): void {
+				$this->config = $config;
+			}
+
+			public function getConfig(): ModelConfig {
+				return $this->config;
+			}
+
+			public function generateTextResult( array $prompt ): GenerativeAiResult { // phpcs:ignore Generic.CodeAnalysis.UnusedFunctionParameter
+				return $this->result;
+			}
+
+			public function streamGenerateTextResult( array $prompt ): Generator { // phpcs:ignore Generic.CodeAnalysis.UnusedFunctionParameter
+				yield $this->result;
+			}
+		};
+	}
+
+	/**
+	 * Creates a mock image generation model using anonymous class.
+	 *
+	 * @param GenerativeAiResult $result   The result to return from generation.
+	 * @param ModelMetadata|null $metadata Optional metadata.
+	 * @return ModelInterface&ImageGenerationModelInterface The mock model.
+	 */
+	protected function create_mock_image_generation_model(
+		GenerativeAiResult $result,
+		?ModelMetadata $metadata = null
+	): ModelInterface {
+		$metadata = $metadata ?? $this->create_test_image_model_metadata();
+
+		$provider_metadata = new ProviderMetadata(
+			'mock',
+			'Mock Provider',
+			ProviderTypeEnum::cloud()
+		);
+
+		return new class( $metadata, $provider_metadata, $result ) implements ModelInterface, ImageGenerationModelInterface {
+
+			private ModelMetadata $metadata;
+			private ProviderMetadata $provider_metadata;
+			private GenerativeAiResult $result;
+			private ModelConfig $config;
+
+			public function __construct(
+				ModelMetadata $metadata,
+				ProviderMetadata $provider_metadata,
+				GenerativeAiResult $result
+			) {
+				$this->metadata          = $metadata;
+				$this->provider_metadata = $provider_metadata;
+				$this->result            = $result;
+				$this->config            = new ModelConfig();
+			}
+
+			public function metadata(): ModelMetadata {
+				return $this->metadata;
+			}
+
+			public function providerMetadata(): ProviderMetadata {
+				return $this->provider_metadata;
+			}
+
+			public function setConfig( ModelConfig $config ): void {
+				$this->config = $config;
+			}
+
+			public function getConfig(): ModelConfig {
+				return $this->config;
+			}
+
+			public function generateImageResult( array $prompt ): GenerativeAiResult { // phpcs:ignore Generic.CodeAnalysis.UnusedFunctionParameter
+				return $this->result;
+			}
+		};
+	}
+
+	/**
+	 * Creates a mock speech generation model using anonymous class.
+	 *
+	 * @param GenerativeAiResult $result   The result to return from generation.
+	 * @param ModelMetadata|null $metadata Optional metadata.
+	 * @return ModelInterface&SpeechGenerationModelInterface The mock model.
+	 */
+	protected function create_mock_speech_generation_model(
+		GenerativeAiResult $result,
+		?ModelMetadata $metadata = null
+	): ModelInterface {
+		$metadata = $metadata ?? $this->create_test_speech_model_metadata();
+
+		$provider_metadata = new ProviderMetadata(
+			'mock-provider',
+			'Mock Provider',
+			ProviderTypeEnum::cloud()
+		);
+
+		return new class( $metadata, $provider_metadata, $result ) implements ModelInterface, SpeechGenerationModelInterface {
+
+			private ModelMetadata $metadata;
+			private ProviderMetadata $provider_metadata;
+			private GenerativeAiResult $result;
+			private ModelConfig $config;
+
+			public function __construct(
+				ModelMetadata $metadata,
+				ProviderMetadata $provider_metadata,
+				GenerativeAiResult $result
+			) {
+				$this->metadata          = $metadata;
+				$this->provider_metadata = $provider_metadata;
+				$this->result            = $result;
+				$this->config            = new ModelConfig();
+			}
+
+			public function metadata(): ModelMetadata {
+				return $this->metadata;
+			}
+
+			public function providerMetadata(): ProviderMetadata {
+				return $this->provider_metadata;
+			}
+
+			public function setConfig( ModelConfig $config ): void {
+				$this->config = $config;
+			}
+
+			public function getConfig(): ModelConfig {
+				return $this->config;
+			}
+
+			public function generateSpeechResult( array $prompt ): GenerativeAiResult { // phpcs:ignore Generic.CodeAnalysis.UnusedFunctionParameter
+				return $this->result;
+			}
+		};
+	}
+
+	/**
+	 * Creates a mock text-to-speech conversion model using anonymous class.
+	 *
+	 * @param GenerativeAiResult $result   The result to return from conversion.
+	 * @param ModelMetadata|null $metadata Optional metadata.
+	 * @return ModelInterface&TextToSpeechConversionModelInterface The mock model.
+	 */
+	protected function create_mock_text_to_speech_model(
+		GenerativeAiResult $result,
+		?ModelMetadata $metadata = null
+	): ModelInterface {
+		$metadata = $metadata ?? $this->create_test_text_to_speech_model_metadata();
+
+		$provider_metadata = new ProviderMetadata(
+			'mock-provider',
+			'Mock Provider',
+			ProviderTypeEnum::cloud()
+		);
+
+		return new class( $metadata, $provider_metadata, $result ) implements ModelInterface, TextToSpeechConversionModelInterface {
+
+			private ModelMetadata $metadata;
+			private ProviderMetadata $provider_metadata;
+			private GenerativeAiResult $result;
+			private ModelConfig $config;
+
+			public function __construct(
+				ModelMetadata $metadata,
+				ProviderMetadata $provider_metadata,
+				GenerativeAiResult $result
+			) {
+				$this->metadata          = $metadata;
+				$this->provider_metadata = $provider_metadata;
+				$this->result            = $result;
+				$this->config            = new ModelConfig();
+			}
+
+			public function metadata(): ModelMetadata {
+				return $this->metadata;
+			}
+
+			public function providerMetadata(): ProviderMetadata {
+				return $this->provider_metadata;
+			}
+
+			public function setConfig( ModelConfig $config ): void {
+				$this->config = $config;
+			}
+
+			public function getConfig(): ModelConfig {
+				return $this->config;
+			}
+
+			public function convertTextToSpeechResult( array $prompt ): GenerativeAiResult { // phpcs:ignore Generic.CodeAnalysis.UnusedFunctionParameter
+				return $this->result;
+			}
+		};
+	}
+
+	/**
+	 * Creates a mock text generation model that throws an exception.
+	 *
+	 * @param Exception          $exception The exception to throw from generation.
+	 * @param ModelMetadata|null $metadata  Optional metadata.
+	 * @return ModelInterface&TextGenerationModelInterface The mock model.
+	 */
+	protected function create_mock_text_generation_model_with_exception(
+		Exception $exception,
+		?ModelMetadata $metadata = null
+	): ModelInterface {
+		$metadata = $metadata ?? $this->create_test_text_model_metadata();
+
+		$provider_metadata = new ProviderMetadata(
+			'mock',
+			'Mock Provider',
+			ProviderTypeEnum::cloud()
+		);
+
+		return new class( $metadata, $provider_metadata, $exception ) implements ModelInterface, TextGenerationModelInterface {
+
+			private ModelMetadata $metadata;
+			private ProviderMetadata $provider_metadata;
+			private Exception $exception;
+			private ModelConfig $config;
+
+			public function __construct(
+				ModelMetadata $metadata,
+				ProviderMetadata $provider_metadata,
+				Exception $exception
+			) {
+				$this->metadata          = $metadata;
+				$this->provider_metadata = $provider_metadata;
+				$this->exception         = $exception;
+				$this->config            = new ModelConfig();
+			}
+
+			public function metadata(): ModelMetadata {
+				return $this->metadata;
+			}
+
+			public function providerMetadata(): ProviderMetadata {
+				return $this->provider_metadata;
+			}
+
+			public function setConfig( ModelConfig $config ): void {
+				$this->config = $config;
+			}
+
+			public function getConfig(): ModelConfig {
+				return $this->config;
+			}
+
+			public function generateTextResult( array $prompt ): GenerativeAiResult { // phpcs:ignore Generic.CodeAnalysis.UnusedFunctionParameter
+				throw $this->exception;
+			}
+
+			public function streamGenerateTextResult( array $prompt ): Generator { // phpcs:ignore Generic.CodeAnalysis.UnusedFunctionParameter
+				throw $this->exception;
+			}
+		};
+	}
+}
diff --git a/tests/phpunit/tests/ai-client/wpAiClientAbilityFunctionResolver.php b/tests/phpunit/tests/ai-client/wpAiClientAbilityFunctionResolver.php
new file mode 100644
index 0000000000000..fb5e2fefb9f29
--- /dev/null
+++ b/tests/phpunit/tests/ai-client/wpAiClientAbilityFunctionResolver.php
@@ -0,0 +1,757 @@
+<?php
+/**
+ * Tests for WP_AI_Client_Ability_Function_Resolver.
+ *
+ * @group ai-client
+ * @covers WP_AI_Client_Ability_Function_Resolver
+ */
+
+use WordPress\AiClient\Messages\DTO\Message;
+use WordPress\AiClient\Messages\DTO\MessagePart;
+use WordPress\AiClient\Messages\DTO\ModelMessage;
+use WordPress\AiClient\Messages\DTO\UserMessage;
+use WordPress\AiClient\Tools\DTO\FunctionCall;
+use WordPress\AiClient\Tools\DTO\FunctionResponse;
+
+class Tests_AI_Client_AbilityFunctionResolver extends WP_UnitTestCase {
+
+	/**
+	 * Set up before class.
+	 */
+	public static function set_up_before_class() {
+		parent::set_up_before_class();
+
+		global $wp_current_filter;
+
+		// Simulate the init hook for ability categories.
+		$wp_current_filter[] = 'wp_abilities_api_categories_init';
+
+		// Register test ability category.
+		wp_register_ability_category(
+			'wpaiclienttests',
+			array(
+				'label'       => 'WP AI Client Tests',
+				'description' => 'Test abilities for WP AI Client.',
+			)
+		);
+
+		array_pop( $wp_current_filter );
+
+		// Simulate the abilities init action.
+		$wp_current_filter[] = 'wp_abilities_api_init';
+
+		// Register test abilities.
+		wp_register_ability(
+			'wpaiclienttests/simple',
+			array(
+				'label'               => 'Simple Test Ability',
+				'description'         => 'A simple test ability with no parameters.',
+				'category'            => 'wpaiclienttests',
+				'execute_callback'    => static function () {
+					return array( 'success' => true );
+				},
+				'permission_callback' => static function () {
+					return true;
+				},
+			)
+		);
+
+		wp_register_ability(
+			'wpaiclienttests/with-params',
+			array(
+				'label'               => 'Test Ability With Parameters',
+				'description'         => 'A test ability that accepts parameters.',
+				'category'            => 'wpaiclienttests',
+				'input_schema'        => array(
+					'type'                 => 'object',
+					'properties'           => array(
+						'title' => array(
+							'type'        => 'string',
+							'description' => 'The title parameter.',
+							'required'    => true,
+						),
+					),
+					'additionalProperties' => false,
+				),
+				'execute_callback'    => static function ( array $input ) {
+					return array(
+						'success' => true,
+						'title'   => $input['title'],
+					);
+				},
+				'permission_callback' => static function () {
+					return true;
+				},
+			)
+		);
+
+		wp_register_ability(
+			'wpaiclienttests/returns-error',
+			array(
+				'label'               => 'Test Ability That Returns Error',
+				'description'         => 'A test ability that returns a WP_Error.',
+				'category'            => 'wpaiclienttests',
+				'execute_callback'    => static function () {
+					return new WP_Error( 'test_error', 'This is a test error message.' );
+				},
+				'permission_callback' => static function () {
+					return true;
+				},
+			)
+		);
+
+		wp_register_ability(
+			'wpaiclienttests/hyphen-test',
+			array(
+				'label'               => 'Test Ability With Hyphens',
+				'description'         => 'A test ability to verify hyphenated names.',
+				'category'            => 'wpaiclienttests',
+				'execute_callback'    => static function () {
+					return array( 'hyphenated' => true );
+				},
+				'permission_callback' => static function () {
+					return true;
+				},
+			)
+		);
+
+		array_pop( $wp_current_filter );
+	}
+
+	/**
+	 * Test that is_ability_call returns true for a valid ability call.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_is_ability_call_returns_true_for_valid_ability() {
+		$call = new FunctionCall(
+			'test-id',
+			'wpab__tec__create_event',
+			array()
+		);
+
+		$result = WP_AI_Client_Ability_Function_Resolver::is_ability_call( $call );
+
+		$this->assertTrue( $result );
+	}
+
+	/**
+	 * Test that is_ability_call returns true for a nested namespace.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_is_ability_call_returns_true_for_nested_namespace() {
+		$call = new FunctionCall(
+			'test-id',
+			'wpab__tec__v1__create_event',
+			array()
+		);
+
+		$result = WP_AI_Client_Ability_Function_Resolver::is_ability_call( $call );
+
+		$this->assertTrue( $result );
+	}
+
+	/**
+	 * Test that is_ability_call returns false for a non-ability call.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_is_ability_call_returns_false_for_non_ability() {
+		$call = new FunctionCall(
+			'test-id',
+			'regular_function',
+			array()
+		);
+
+		$result = WP_AI_Client_Ability_Function_Resolver::is_ability_call( $call );
+
+		$this->assertFalse( $result );
+	}
+
+	/**
+	 * Test that is_ability_call returns false when name is null.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_is_ability_call_returns_false_when_name_is_null() {
+		$call = new FunctionCall(
+			'test-id',
+			null,
+			array()
+		);
+
+		$result = WP_AI_Client_Ability_Function_Resolver::is_ability_call( $call );
+
+		$this->assertFalse( $result );
+	}
+
+	/**
+	 * Test that is_ability_call returns false for partial prefix.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_is_ability_call_returns_false_for_partial_prefix() {
+		$call = new FunctionCall(
+			'test-id',
+			'wpab_single_underscore',
+			array()
+		);
+
+		$result = WP_AI_Client_Ability_Function_Resolver::is_ability_call( $call );
+
+		$this->assertFalse( $result );
+	}
+
+	/**
+	 * Test that execute_ability returns error for non-ability call.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_execute_ability_returns_error_for_non_ability_call() {
+		$call = new FunctionCall(
+			'test-id',
+			'regular_function',
+			array()
+		);
+
+		$response = WP_AI_Client_Ability_Function_Resolver::execute_ability( $call );
+
+		$this->assertInstanceOf( FunctionResponse::class, $response );
+		$this->assertSame( 'test-id', $response->getId() );
+		$this->assertSame( 'regular_function', $response->getName() );
+		$data = $response->getResponse();
+		$this->assertIsArray( $data );
+		$this->assertArrayHasKey( 'error', $data );
+		$this->assertSame( 'Not an ability function call', $data['error'] );
+		$this->assertArrayHasKey( 'code', $data );
+		$this->assertSame( 'invalid_ability_call', $data['code'] );
+	}
+
+	/**
+	 * Test that execute_ability returns error when ability not found.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_execute_ability_returns_error_when_ability_not_found() {
+		$this->setExpectedIncorrectUsage( 'WP_Abilities_Registry::get_registered' );
+
+		$call = new FunctionCall(
+			'test-id',
+			'wpab__nonexistent__ability',
+			array()
+		);
+
+		$response = WP_AI_Client_Ability_Function_Resolver::execute_ability( $call );
+
+		$this->assertInstanceOf( FunctionResponse::class, $response );
+		$this->assertSame( 'test-id', $response->getId() );
+		$this->assertSame( 'wpab__nonexistent__ability', $response->getName() );
+		$data = $response->getResponse();
+		$this->assertIsArray( $data );
+		$this->assertArrayHasKey( 'error', $data );
+		$this->assertStringContainsString( 'not found', $data['error'] );
+		$this->assertArrayHasKey( 'code', $data );
+		$this->assertSame( 'ability_not_found', $data['code'] );
+	}
+
+	/**
+	 * Test that execute_ability handles missing id.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_execute_ability_handles_missing_id() {
+		$this->setExpectedIncorrectUsage( 'WP_Abilities_Registry::get_registered' );
+
+		$call = new FunctionCall(
+			null,
+			'wpab__nonexistent__ability',
+			array()
+		);
+
+		$response = WP_AI_Client_Ability_Function_Resolver::execute_ability( $call );
+
+		$this->assertInstanceOf( FunctionResponse::class, $response );
+		$this->assertSame( 'unknown', $response->getId() );
+	}
+
+	/**
+	 * Test that has_ability_calls returns true when ability call is present.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_has_ability_calls_returns_true_when_present() {
+		$call = new FunctionCall(
+			'test-id',
+			'wpab__tec__create_event',
+			array()
+		);
+
+		$message = new ModelMessage(
+			array(
+				new MessagePart( 'Here is the result:' ),
+				new MessagePart( $call ),
+			)
+		);
+
+		$result = WP_AI_Client_Ability_Function_Resolver::has_ability_calls( $message );
+
+		$this->assertTrue( $result );
+	}
+
+	/**
+	 * Test that has_ability_calls returns false when ability call is not present.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_has_ability_calls_returns_false_when_not_present() {
+		$call = new FunctionCall(
+			'test-id',
+			'regular_function',
+			array()
+		);
+
+		$message = new ModelMessage(
+			array(
+				new MessagePart( 'Here is the result:' ),
+				new MessagePart( $call ),
+			)
+		);
+
+		$result = WP_AI_Client_Ability_Function_Resolver::has_ability_calls( $message );
+
+		$this->assertFalse( $result );
+	}
+
+	/**
+	 * Test that has_ability_calls returns false for text-only message.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_has_ability_calls_returns_false_for_text_only() {
+		$message = new UserMessage(
+			array(
+				new MessagePart( 'Just some text' ),
+			)
+		);
+
+		$result = WP_AI_Client_Ability_Function_Resolver::has_ability_calls( $message );
+
+		$this->assertFalse( $result );
+	}
+
+	/**
+	 * Test that has_ability_calls returns true with mixed content.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_has_ability_calls_returns_true_with_mixed_content() {
+		$regular_call = new FunctionCall(
+			'regular-id',
+			'regular_function',
+			array()
+		);
+
+		$ability_call = new FunctionCall(
+			'ability-id',
+			'wpab__tec__create_event',
+			array()
+		);
+
+		$message = new ModelMessage(
+			array(
+				new MessagePart( 'Some text' ),
+				new MessagePart( $regular_call ),
+				new MessagePart( $ability_call ),
+			)
+		);
+
+		$result = WP_AI_Client_Ability_Function_Resolver::has_ability_calls( $message );
+
+		$this->assertTrue( $result );
+	}
+
+	/**
+	 * Test that has_ability_calls handles empty message.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_has_ability_calls_with_empty_message() {
+		$message = new ModelMessage( array() );
+
+		$result = WP_AI_Client_Ability_Function_Resolver::has_ability_calls( $message );
+
+		$this->assertFalse( $result );
+	}
+
+	/**
+	 * Test that execute_abilities handles empty message.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_execute_abilities_with_empty_message() {
+		$message = new ModelMessage( array() );
+
+		$result = WP_AI_Client_Ability_Function_Resolver::execute_abilities( $message );
+
+		$this->assertInstanceOf( UserMessage::class, $result );
+		$this->assertCount( 0, $result->getParts() );
+	}
+
+	/**
+	 * Test that execute_abilities handles errors gracefully.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_execute_abilities_handles_errors_gracefully() {
+		$this->setExpectedIncorrectUsage( 'WP_Abilities_Registry::get_registered' );
+
+		$call = new FunctionCall(
+			'test-id',
+			'wpab__nonexistent__ability',
+			array()
+		);
+
+		$message = new ModelMessage(
+			array(
+				new MessagePart( $call ),
+			)
+		);
+
+		$result = WP_AI_Client_Ability_Function_Resolver::execute_abilities( $message );
+
+		$this->assertInstanceOf( UserMessage::class, $result );
+		$parts = $result->getParts();
+		$this->assertCount( 1, $parts );
+
+		$response = $parts[0]->getFunctionResponse();
+		$this->assertInstanceOf( FunctionResponse::class, $response );
+		$data = $response->getResponse();
+		$this->assertArrayHasKey( 'error', $data );
+	}
+
+	/**
+	 * Test that execute_abilities returns a UserMessage.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_execute_abilities_returns_user_message() {
+		$this->setExpectedIncorrectUsage( 'WP_Abilities_Registry::get_registered' );
+
+		$call = new FunctionCall(
+			'test-id',
+			'wpab__nonexistent__ability',
+			array()
+		);
+
+		$message = new ModelMessage(
+			array(
+				new MessagePart( $call ),
+			)
+		);
+
+		$result = WP_AI_Client_Ability_Function_Resolver::execute_abilities( $message );
+
+		$this->assertInstanceOf( UserMessage::class, $result );
+	}
+
+	/**
+	 * Test that execute_abilities processes multiple calls.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_execute_abilities_processes_multiple_calls() {
+		$this->setExpectedIncorrectUsage( 'WP_Abilities_Registry::get_registered' );
+
+		$call1 = new FunctionCall(
+			'call-1',
+			'wpab__nonexistent__ability1',
+			array()
+		);
+
+		$call2 = new FunctionCall(
+			'call-2',
+			'wpab__nonexistent__ability2',
+			array()
+		);
+
+		$message = new ModelMessage(
+			array(
+				new MessagePart( $call1 ),
+				new MessagePart( $call2 ),
+			)
+		);
+
+		$result = WP_AI_Client_Ability_Function_Resolver::execute_abilities( $message );
+
+		$this->assertInstanceOf( UserMessage::class, $result );
+		$parts = $result->getParts();
+		$this->assertCount( 2, $parts );
+	}
+
+	/**
+	 * Test that execute_abilities only processes function calls.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_execute_abilities_only_processes_function_calls() {
+		$this->setExpectedIncorrectUsage( 'WP_Abilities_Registry::get_registered' );
+
+		$call = new FunctionCall(
+			'test-id',
+			'wpab__nonexistent__ability',
+			array()
+		);
+
+		$message = new ModelMessage(
+			array(
+				new MessagePart( 'Some text' ),
+				new MessagePart( $call ),
+				new MessagePart( 'More text' ),
+			)
+		);
+
+		$result = WP_AI_Client_Ability_Function_Resolver::execute_abilities( $message );
+
+		$this->assertInstanceOf( UserMessage::class, $result );
+		$parts = $result->getParts();
+		// Only the function call should be processed.
+		$this->assertCount( 1, $parts );
+	}
+
+	/**
+	 * Test ability_name_to_function_name with simple name.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_ability_name_to_function_name_simple() {
+		$result = WP_AI_Client_Ability_Function_Resolver::ability_name_to_function_name( 'tec/create_event' );
+
+		$this->assertSame( 'wpab__tec__create_event', $result );
+	}
+
+	/**
+	 * Test ability_name_to_function_name with nested namespace.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_ability_name_to_function_name_nested() {
+		$result = WP_AI_Client_Ability_Function_Resolver::ability_name_to_function_name( 'tec/v1/create_event' );
+
+		$this->assertSame( 'wpab__tec__v1__create_event', $result );
+	}
+
+	/**
+	 * Test execute_ability with successful execution.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_execute_ability_success() {
+		$call = new FunctionCall(
+			'test-id',
+			'wpab__wpaiclienttests__simple',
+			array()
+		);
+
+		$response = WP_AI_Client_Ability_Function_Resolver::execute_ability( $call );
+
+		$this->assertInstanceOf( FunctionResponse::class, $response );
+		$this->assertSame( 'test-id', $response->getId() );
+		$this->assertSame( 'wpab__wpaiclienttests__simple', $response->getName() );
+		$data = $response->getResponse();
+		$this->assertIsArray( $data );
+		$this->assertArrayHasKey( 'success', $data );
+		$this->assertTrue( $data['success'] );
+	}
+
+	/**
+	 * Test execute_ability with parameters.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_execute_ability_with_parameters() {
+		$call = new FunctionCall(
+			'test-id',
+			'wpab__wpaiclienttests__with-params',
+			array( 'title' => 'Test Title' )
+		);
+
+		$response = WP_AI_Client_Ability_Function_Resolver::execute_ability( $call );
+
+		$this->assertInstanceOf( FunctionResponse::class, $response );
+		$this->assertSame( 'test-id', $response->getId() );
+		$this->assertSame( 'wpab__wpaiclienttests__with-params', $response->getName() );
+		$data = $response->getResponse();
+		$this->assertIsArray( $data );
+		$this->assertArrayHasKey( 'success', $data );
+		$this->assertTrue( $data['success'] );
+		$this->assertArrayHasKey( 'title', $data );
+		$this->assertSame( 'Test Title', $data['title'] );
+	}
+
+	/**
+	 * Test execute_ability handles WP_Error.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_execute_ability_handles_wp_error() {
+		$call = new FunctionCall(
+			'test-id',
+			'wpab__wpaiclienttests__returns-error',
+			array()
+		);
+
+		$response = WP_AI_Client_Ability_Function_Resolver::execute_ability( $call );
+
+		$this->assertInstanceOf( FunctionResponse::class, $response );
+		$this->assertSame( 'test-id', $response->getId() );
+		$this->assertSame( 'wpab__wpaiclienttests__returns-error', $response->getName() );
+		$data = $response->getResponse();
+		$this->assertIsArray( $data );
+		$this->assertArrayHasKey( 'error', $data );
+		$this->assertSame( 'This is a test error message.', $data['error'] );
+		$this->assertArrayHasKey( 'code', $data );
+		$this->assertSame( 'test_error', $data['code'] );
+	}
+
+	/**
+	 * Test execute_abilities with successful execution.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_execute_abilities_success() {
+		$call = new FunctionCall(
+			'test-id',
+			'wpab__wpaiclienttests__simple',
+			array()
+		);
+
+		$message = new ModelMessage(
+			array(
+				new MessagePart( $call ),
+			)
+		);
+
+		$result = WP_AI_Client_Ability_Function_Resolver::execute_abilities( $message );
+
+		$this->assertInstanceOf( UserMessage::class, $result );
+		$parts = $result->getParts();
+		$this->assertCount( 1, $parts );
+
+		$response = $parts[0]->getFunctionResponse();
+		$this->assertInstanceOf( FunctionResponse::class, $response );
+		$data = $response->getResponse();
+		$this->assertArrayHasKey( 'success', $data );
+		$this->assertTrue( $data['success'] );
+	}
+
+	/**
+	 * Test execute_abilities with multiple successful executions.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_execute_abilities_multiple_success() {
+		$call1 = new FunctionCall(
+			'call-1',
+			'wpab__wpaiclienttests__simple',
+			array()
+		);
+
+		$call2 = new FunctionCall(
+			'call-2',
+			'wpab__wpaiclienttests__hyphen-test',
+			array()
+		);
+
+		$message = new ModelMessage(
+			array(
+				new MessagePart( $call1 ),
+				new MessagePart( $call2 ),
+			)
+		);
+
+		$result = WP_AI_Client_Ability_Function_Resolver::execute_abilities( $message );
+
+		$this->assertInstanceOf( UserMessage::class, $result );
+		$parts = $result->getParts();
+		$this->assertCount( 2, $parts );
+
+		// Check first response.
+		$response1 = $parts[0]->getFunctionResponse();
+		$this->assertInstanceOf( FunctionResponse::class, $response1 );
+		$data1 = $response1->getResponse();
+		$this->assertArrayHasKey( 'success', $data1 );
+		$this->assertTrue( $data1['success'] );
+
+		// Check second response.
+		$response2 = $parts[1]->getFunctionResponse();
+		$this->assertInstanceOf( FunctionResponse::class, $response2 );
+		$data2 = $response2->getResponse();
+		$this->assertArrayHasKey( 'hyphenated', $data2 );
+		$this->assertTrue( $data2['hyphenated'] );
+	}
+
+	/**
+	 * Test execute_abilities with mixed text and ability calls.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_execute_abilities_with_mixed_content() {
+		$call = new FunctionCall(
+			'test-id',
+			'wpab__wpaiclienttests__simple',
+			array()
+		);
+
+		$message = new ModelMessage(
+			array(
+				new MessagePart( 'Starting execution' ),
+				new MessagePart( $call ),
+				new MessagePart( 'Execution complete' ),
+			)
+		);
+
+		$result = WP_AI_Client_Ability_Function_Resolver::execute_abilities( $message );
+
+		$this->assertInstanceOf( UserMessage::class, $result );
+		$parts = $result->getParts();
+		// Only function calls should be processed.
+		$this->assertCount( 1, $parts );
+
+		$response = $parts[0]->getFunctionResponse();
+		$this->assertInstanceOf( FunctionResponse::class, $response );
+	}
+
+	/**
+	 * Test execute_abilities with ability that has parameters.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_execute_abilities_with_parameters() {
+		$call = new FunctionCall(
+			'test-id',
+			'wpab__wpaiclienttests__with-params',
+			array( 'title' => 'Integration Test' )
+		);
+
+		$message = new ModelMessage(
+			array(
+				new MessagePart( $call ),
+			)
+		);
+
+		$result = WP_AI_Client_Ability_Function_Resolver::execute_abilities( $message );
+
+		$this->assertInstanceOf( UserMessage::class, $result );
+		$parts = $result->getParts();
+		$this->assertCount( 1, $parts );
+
+		$response = $parts[0]->getFunctionResponse();
+		$this->assertInstanceOf( FunctionResponse::class, $response );
+		$data = $response->getResponse();
+		$this->assertArrayHasKey( 'success', $data );
+		$this->assertTrue( $data['success'] );
+		$this->assertArrayHasKey( 'title', $data );
+		$this->assertSame( 'Integration Test', $data['title'] );
+	}
+}
diff --git a/tests/phpunit/tests/ai-client/wpAiClientCache.php b/tests/phpunit/tests/ai-client/wpAiClientCache.php
new file mode 100644
index 0000000000000..77a18b09aa13a
--- /dev/null
+++ b/tests/phpunit/tests/ai-client/wpAiClientCache.php
@@ -0,0 +1,175 @@
+<?php
+/**
+ * Tests for WP_AI_Client_Cache.
+ *
+ * @group ai-client
+ * @covers WP_AI_Client_Cache
+ */
+class Tests_AI_Client_Cache extends WP_UnitTestCase {
+
+	/**
+	 * Cache instance under test.
+	 *
+	 * @var WP_AI_Client_Cache
+	 */
+	private $cache;
+
+	/**
+	 * Sets up a fresh cache instance before each test.
+	 */
+	public function set_up() {
+		parent::set_up();
+		$this->cache = new WP_AI_Client_Cache();
+	}
+
+	/**
+	 * Test that the cache implements the scoped PSR-16 CacheInterface.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_implements_cache_interface() {
+		$this->assertInstanceOf(
+			WordPress\AiClientDependencies\Psr\SimpleCache\CacheInterface::class,
+			$this->cache
+		);
+	}
+
+	/**
+	 * Test that get returns default value on cache miss.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_get_returns_default_on_miss() {
+		$this->assertNull( $this->cache->get( 'nonexistent' ) );
+		$this->assertSame( 'fallback', $this->cache->get( 'nonexistent', 'fallback' ) );
+	}
+
+	/**
+	 * Test set and get round-trip.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_set_and_get() {
+		$this->assertTrue( $this->cache->set( 'key1', 'value1' ) );
+		$this->assertSame( 'value1', $this->cache->get( 'key1' ) );
+	}
+
+	/**
+	 * Test delete removes cached item.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_delete() {
+		$this->cache->set( 'key1', 'value1' );
+		$this->assertTrue( $this->cache->delete( 'key1' ) );
+		$this->assertNull( $this->cache->get( 'key1' ) );
+	}
+
+	/**
+	 * Test has returns false on cache miss.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_has_returns_false_on_miss() {
+		$this->assertFalse( $this->cache->has( 'nonexistent' ) );
+	}
+
+	/**
+	 * Test has returns true on cache hit.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_has_returns_true_on_hit() {
+		$this->cache->set( 'key1', 'value1' );
+		$this->assertTrue( $this->cache->has( 'key1' ) );
+	}
+
+	/**
+	 * Test getMultiple returns values and defaults.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_get_multiple() {
+		$this->cache->set( 'key1', 'value1' );
+		$this->cache->set( 'key2', 'value2' );
+
+		$result = $this->cache->getMultiple( array( 'key1', 'key2', 'key3' ), 'default' );
+
+		$this->assertSame( 'value1', $result['key1'] );
+		$this->assertSame( 'value2', $result['key2'] );
+		$this->assertSame( 'default', $result['key3'] );
+	}
+
+	/**
+	 * Test setMultiple stores multiple values.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_set_multiple() {
+		$this->assertTrue(
+			$this->cache->setMultiple(
+				array(
+					'key1' => 'value1',
+					'key2' => 'value2',
+				)
+			)
+		);
+
+		$this->assertSame( 'value1', $this->cache->get( 'key1' ) );
+		$this->assertSame( 'value2', $this->cache->get( 'key2' ) );
+	}
+
+	/**
+	 * Test deleteMultiple removes multiple items.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_delete_multiple() {
+		$this->cache->set( 'key1', 'value1' );
+		$this->cache->set( 'key2', 'value2' );
+
+		$this->assertTrue( $this->cache->deleteMultiple( array( 'key1', 'key2' ) ) );
+		$this->assertNull( $this->cache->get( 'key1' ) );
+		$this->assertNull( $this->cache->get( 'key2' ) );
+	}
+
+	/**
+	 * Test clear flushes the cache group.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_clear() {
+		$this->cache->set( 'key1', 'value1' );
+
+		// WordPress default object cache supports flush_group.
+		$result = $this->cache->clear();
+
+		if ( function_exists( 'wp_cache_supports' ) && wp_cache_supports( 'flush_group' ) ) {
+			$this->assertTrue( $result );
+			$this->assertNull( $this->cache->get( 'key1' ) );
+		} else {
+			$this->assertFalse( $result );
+		}
+	}
+
+	/**
+	 * Test set with integer TTL.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_ttl_with_integer() {
+		$this->assertTrue( $this->cache->set( 'key1', 'value1', 3600 ) );
+		$this->assertSame( 'value1', $this->cache->get( 'key1' ) );
+	}
+
+	/**
+	 * Test set with DateInterval TTL.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_ttl_with_date_interval() {
+		$ttl = new DateInterval( 'PT1H' );
+		$this->assertTrue( $this->cache->set( 'key1', 'value1', $ttl ) );
+		$this->assertSame( 'value1', $this->cache->get( 'key1' ) );
+	}
+}
diff --git a/tests/phpunit/tests/ai-client/wpAiClientEventDispatcher.php b/tests/phpunit/tests/ai-client/wpAiClientEventDispatcher.php
new file mode 100644
index 0000000000000..3cd621f09bf2c
--- /dev/null
+++ b/tests/phpunit/tests/ai-client/wpAiClientEventDispatcher.php
@@ -0,0 +1,55 @@
+<?php
+/**
+ * Tests for WP_AI_Client_Event_Dispatcher.
+ *
+ * @group ai-client
+ * @covers WP_AI_Client_Event_Dispatcher
+ */
+
+require_once dirname( __DIR__, 2 ) . '/includes/wp-ai-client-mock-event.php';
+
+class Tests_AI_Client_EventDispatcher extends WP_UnitTestCase {
+
+	/**
+	 * Test that dispatch fires the appropriate action hook.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_dispatch_fires_action_hook() {
+		$dispatcher = new WP_AI_Client_Event_Dispatcher();
+		$event      = new WP_AI_Client_Mock_Event();
+
+		$hook_fired  = false;
+		$fired_event = null;
+
+		add_action(
+			'wp_ai_client_wp_ai_client_mock',
+			function ( $e ) use ( &$hook_fired, &$fired_event ) {
+				$hook_fired  = true;
+				$fired_event = $e;
+			}
+		);
+
+		$result = $dispatcher->dispatch( $event );
+
+		$this->assertTrue( $hook_fired, 'The action hook should have been fired' );
+		$this->assertSame( $event, $fired_event, 'The fired event should be the same as the dispatched event' );
+		$this->assertSame( $event, $result, 'The dispatch method should return the same event' );
+	}
+
+	/**
+	 * Test that dispatch returns event without listeners.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_dispatch_returns_event_without_listeners() {
+		$dispatcher        = new WP_AI_Client_Event_Dispatcher();
+		$event             = new stdClass();
+		$event->test_value = 'original';
+
+		$result = $dispatcher->dispatch( $event );
+
+		$this->assertSame( $event, $result, 'The dispatch method should return the same object' );
+		$this->assertSame( 'original', $result->test_value, 'The event object should remain unchanged' );
+	}
+}
diff --git a/tests/phpunit/tests/ai-client/wpAiClientPrompt.php b/tests/phpunit/tests/ai-client/wpAiClientPrompt.php
new file mode 100644
index 0000000000000..131ac315eb3e7
--- /dev/null
+++ b/tests/phpunit/tests/ai-client/wpAiClientPrompt.php
@@ -0,0 +1,91 @@
+<?php
+/**
+ * Tests for wp_ai_client_prompt().
+ *
+ * @group ai-client
+ * @covers ::wp_ai_client_prompt
+ */
+
+use WordPress\AiClient\Builders\PromptBuilder;
+
+class Tests_AI_Client_Prompt extends WP_UnitTestCase {
+
+	/**
+	 * Test that wp_ai_client_prompt() returns a WP_AI_Client_Prompt_Builder instance.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_returns_prompt_builder_instance() {
+		$builder = wp_ai_client_prompt();
+
+		$this->assertInstanceOf( WP_AI_Client_Prompt_Builder::class, $builder );
+	}
+
+	/**
+	 * Test that wp_ai_client_prompt() wraps a PromptBuilder internally.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_wraps_sdk_prompt_builder() {
+		$builder = wp_ai_client_prompt();
+
+		$reflection = new ReflectionClass( WP_AI_Client_Prompt_Builder::class );
+		$property   = $reflection->getProperty( 'builder' );
+
+		$this->assertInstanceOf( PromptBuilder::class, $property->getValue( $builder ) );
+	}
+
+	/**
+	 * Test that wp_ai_client_prompt() passes prompt content to the builder.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_passes_prompt_content() {
+		$builder = wp_ai_client_prompt( 'Hello, AI!' );
+
+		$reflection       = new ReflectionClass( WP_AI_Client_Prompt_Builder::class );
+		$builder_property = $reflection->getProperty( 'builder' );
+
+		$wrapped = $builder_property->getValue( $builder );
+
+		$wrapped_reflection = new ReflectionClass( get_class( $wrapped ) );
+		$messages_property  = $wrapped_reflection->getProperty( 'messages' );
+
+		$messages = $messages_property->getValue( $wrapped );
+
+		$this->assertNotEmpty( $messages, 'Prompt content should produce at least one message.' );
+	}
+
+	/**
+	 * Test that wp_ai_client_prompt() without arguments creates builder with no messages.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_no_prompt_creates_empty_builder() {
+		$builder = wp_ai_client_prompt();
+
+		$reflection       = new ReflectionClass( WP_AI_Client_Prompt_Builder::class );
+		$builder_property = $reflection->getProperty( 'builder' );
+
+		$wrapped = $builder_property->getValue( $builder );
+
+		$wrapped_reflection = new ReflectionClass( get_class( $wrapped ) );
+		$messages_property  = $wrapped_reflection->getProperty( 'messages' );
+
+		$messages = $messages_property->getValue( $wrapped );
+
+		$this->assertEmpty( $messages, 'No prompt content should produce no messages.' );
+	}
+
+	/**
+	 * Test that successive calls return independent builder instances.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_returns_independent_instances() {
+		$builder1 = wp_ai_client_prompt( 'First' );
+		$builder2 = wp_ai_client_prompt( 'Second' );
+
+		$this->assertNotSame( $builder1, $builder2 );
+	}
+}
diff --git a/tests/phpunit/tests/ai-client/wpAiClientPromptBuilder.php b/tests/phpunit/tests/ai-client/wpAiClientPromptBuilder.php
new file mode 100644
index 0000000000000..d1d7f73e853f0
--- /dev/null
+++ b/tests/phpunit/tests/ai-client/wpAiClientPromptBuilder.php
@@ -0,0 +1,2409 @@
+<?php
+/**
+ * Tests for WP_AI_Client_Prompt_Builder.
+ *
+ * @group ai-client
+ * @covers WP_AI_Client_Prompt_Builder
+ */
+
+use WordPress\AiClient\AiClient;
+use WordPress\AiClient\Builders\PromptBuilder;
+use WordPress\AiClient\Files\DTO\File;
+use WordPress\AiClient\Files\Enums\FileTypeEnum;
+use WordPress\AiClient\Messages\DTO\Message;
+use WordPress\AiClient\Messages\DTO\MessagePart;
+use WordPress\AiClient\Messages\DTO\ModelMessage;
+use WordPress\AiClient\Messages\DTO\UserMessage;
+use WordPress\AiClient\Messages\Enums\MessageRoleEnum;
+use WordPress\AiClient\Messages\Enums\ModalityEnum;
+use WordPress\AiClient\Providers\DTO\ProviderMetadata;
+use WordPress\AiClient\Providers\DTO\ProviderModelsMetadata;
+use WordPress\AiClient\Providers\Enums\ProviderTypeEnum;
+use WordPress\AiClient\Providers\Http\DTO\RequestOptions;
+use WordPress\AiClient\Providers\Models\Contracts\ModelInterface;
+use WordPress\AiClient\Providers\Models\DTO\ModelConfig;
+use WordPress\AiClient\Providers\Models\DTO\ModelMetadata;
+use WordPress\AiClient\Providers\Models\DTO\ModelRequirements;
+use WordPress\AiClient\Providers\Models\DTO\SupportedOption;
+use WordPress\AiClient\Providers\Models\Enums\CapabilityEnum;
+use WordPress\AiClient\Providers\Models\Enums\OptionEnum;
+use WordPress\AiClient\Providers\ProviderRegistry;
+use WordPress\AiClient\Results\DTO\Candidate;
+use WordPress\AiClient\Results\DTO\GenerativeAiResult;
+use WordPress\AiClient\Results\DTO\TokenUsage;
+use WordPress\AiClient\Results\Enums\FinishReasonEnum;
+use WordPress\AiClient\Tools\DTO\FunctionDeclaration;
+use WordPress\AiClient\Tools\DTO\FunctionResponse;
+
+require_once dirname( __DIR__, 2 ) . '/includes/wp-ai-client-mock-model-creation-trait.php';
+
+class Tests_AI_Client_PromptBuilder extends WP_UnitTestCase {
+	use WP_AI_Client_Mock_Model_Creation_Trait;
+
+	/**
+	 * @var ProviderRegistry
+	 */
+	private ProviderRegistry $registry;
+
+	/**
+	 * Creates a test provider metadata instance.
+	 *
+	 * @return ProviderMetadata
+	 */
+	private function create_test_provider_metadata(): ProviderMetadata {
+		return new ProviderMetadata( 'test-provider', 'Test Provider', ProviderTypeEnum::cloud() );
+	}
+
+	/**
+	 * Creates text model metadata supporting any input modalities.
+	 *
+	 * @param string $id The model identifier.
+	 * @return ModelMetadata
+	 */
+	private function create_text_model_metadata_with_input_support( string $id ): ModelMetadata {
+		return new ModelMetadata(
+			$id,
+			'Test Text Model',
+			array( CapabilityEnum::textGeneration() ),
+			array(
+				new SupportedOption( OptionEnum::inputModalities() ),
+				new SupportedOption( OptionEnum::outputModalities() ),
+			)
+		);
+	}
+
+	/**
+	 * Gets the value of a protected or private property from the wrapped prompt builder.
+	 *
+	 * @param WP_AI_Client_Prompt_Builder $builder  The WordPress prompt builder instance.
+	 * @param string                      $property Property to get value for.
+	 * @return mixed The property value.
+	 */
+	private function get_wrapped_prompt_builder_property_value( WP_AI_Client_Prompt_Builder $builder, string $property ) {
+		$reflection_class = new ReflectionClass( WP_AI_Client_Prompt_Builder::class );
+		$builder_property = $reflection_class->getProperty( 'builder' );
+		$wrapped_builder  = $builder_property->getValue( $builder );
+
+		$reflection_class2 = new ReflectionClass( get_class( $wrapped_builder ) );
+		$the_property      = $reflection_class2->getProperty( $property );
+
+		return $the_property->getValue( $wrapped_builder );
+	}
+
+	/**
+	 * Gets the function declarations from the builder's model config.
+	 *
+	 * @param WP_AI_Client_Prompt_Builder $builder The builder to get declarations from.
+	 * @return list<FunctionDeclaration>|null The function declarations or null if not set.
+	 */
+	private function get_function_declarations( WP_AI_Client_Prompt_Builder $builder ): ?array {
+		/** @var ModelConfig $config */
+		$config = $this->get_wrapped_prompt_builder_property_value( $builder, 'modelConfig' );
+		return $config->getFunctionDeclarations();
+	}
+
+	/**
+	 * Set up before each test.
+	 */
+	public function set_up() {
+		parent::set_up();
+
+		$this->registry = $this->createMock( ProviderRegistry::class );
+	}
+
+	/**
+	 * Test that WP_AI_Client_Prompt_Builder can be instantiated.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_instantiation() {
+		$registry       = AiClient::defaultRegistry();
+		$prompt_builder = new WP_AI_Client_Prompt_Builder( $registry );
+
+		$this->assertInstanceOf( WP_AI_Client_Prompt_Builder::class, $prompt_builder );
+
+		// Verify the wrapped builder is a PromptBuilder instance.
+		$reflection_class = new ReflectionClass( WP_AI_Client_Prompt_Builder::class );
+		$builder_property = $reflection_class->getProperty( 'builder' );
+
+		$wrapped_builder = $builder_property->getValue( $prompt_builder );
+
+		$this->assertInstanceOf( PromptBuilder::class, $wrapped_builder );
+	}
+
+	/**
+	 * Test that WP_AI_Client_Prompt_Builder can be instantiated with initial prompt content.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_instantiation_with_prompt() {
+		$registry       = AiClient::defaultRegistry();
+		$prompt_builder = new WP_AI_Client_Prompt_Builder( $registry, 'Initial prompt text' );
+
+		$this->assertInstanceOf( WP_AI_Client_Prompt_Builder::class, $prompt_builder );
+	}
+
+	/**
+	 * Test that the constructor sets the default request timeout.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_constructor_sets_default_request_timeout() {
+		$builder = new WP_AI_Client_Prompt_Builder( AiClient::defaultRegistry() );
+
+		/** @var RequestOptions $request_options */
+		$request_options = $this->get_wrapped_prompt_builder_property_value( $builder, 'requestOptions' );
+
+		$this->assertInstanceOf( RequestOptions::class, $request_options );
+		$this->assertEquals( 30, $request_options->getTimeout() );
+	}
+
+	/**
+	 * Test that the constructor allows overriding the default request timeout.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_constructor_allows_overriding_request_timeout() {
+		add_filter(
+			'wp_ai_client_default_request_timeout',
+			static function () {
+				return 45;
+			}
+		);
+
+		$builder = new WP_AI_Client_Prompt_Builder( AiClient::defaultRegistry() );
+
+		/** @var RequestOptions $request_options */
+		$request_options = $this->get_wrapped_prompt_builder_property_value( $builder, 'requestOptions' );
+
+		$this->assertInstanceOf( RequestOptions::class, $request_options );
+		$this->assertEquals( 45, $request_options->getTimeout() );
+	}
+
+	/**
+	 * Test method chaining with fluent methods.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_method_chaining_returns_decorator() {
+		$registry       = AiClient::defaultRegistry();
+		$prompt_builder = new WP_AI_Client_Prompt_Builder( $registry );
+
+		$result = $prompt_builder->with_text( 'Test text' );
+		$this->assertSame( $prompt_builder, $result, 'with_text should return the decorator instance' );
+		$this->assertInstanceOf( WP_AI_Client_Prompt_Builder::class, $result );
+
+		$result = $prompt_builder->using_system_instruction( 'System instruction' );
+		$this->assertSame( $prompt_builder, $result, 'using_system_instruction should return the decorator instance' );
+
+		$result = $prompt_builder->using_max_tokens( 100 );
+		$this->assertSame( $prompt_builder, $result, 'using_max_tokens should return the decorator instance' );
+
+		$result = $prompt_builder->using_temperature( 0.7 );
+		$this->assertSame( $prompt_builder, $result, 'using_temperature should return the decorator instance' );
+
+		$result = $prompt_builder->using_top_p( 0.9 );
+		$this->assertSame( $prompt_builder, $result, 'using_top_p should return the decorator instance' );
+
+		$result = $prompt_builder->using_top_k( 50 );
+		$this->assertSame( $prompt_builder, $result, 'using_top_k should return the decorator instance' );
+
+		$result = $prompt_builder->using_presence_penalty( 0.5 );
+		$this->assertSame( $prompt_builder, $result, 'using_presence_penalty should return the decorator instance' );
+
+		$result = $prompt_builder->using_frequency_penalty( 0.5 );
+		$this->assertSame( $prompt_builder, $result, 'using_frequency_penalty should return the decorator instance' );
+
+		$result = $prompt_builder->as_output_mime_type( 'application/json' );
+		$this->assertSame( $prompt_builder, $result, 'as_output_mime_type should return the decorator instance' );
+	}
+
+	/**
+	 * Test complex method chaining scenario.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_complex_method_chaining() {
+		$registry       = AiClient::defaultRegistry();
+		$prompt_builder = new WP_AI_Client_Prompt_Builder( $registry );
+
+		$result = $prompt_builder
+			->with_text( 'Test prompt' )
+			->using_system_instruction( 'You are a helpful assistant' )
+			->using_max_tokens( 500 )
+			->using_temperature( 0.7 )
+			->using_top_p( 0.9 );
+
+		$this->assertSame( $prompt_builder, $result, 'Chained methods should return the same decorator instance' );
+		$this->assertInstanceOf( WP_AI_Client_Prompt_Builder::class, $result );
+	}
+
+	/**
+	 * Test that boolean-returning methods do not return the decorator.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_boolean_methods_return_boolean() {
+		$registry       = AiClient::defaultRegistry();
+		$prompt_builder = new WP_AI_Client_Prompt_Builder( $registry, 'Test text' );
+
+		$result = $prompt_builder->is_supported_for_text_generation();
+		$this->assertIsBool( $result, 'is_supported_for_text_generation should return a boolean' );
+		$this->assertNotSame( $prompt_builder, $result, 'is_supported_for_text_generation should not return the decorator' );
+	}
+
+	/**
+	 * Test snake_case to camelCase conversion.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_snake_case_to_camel_case_conversion() {
+		$registry       = AiClient::defaultRegistry();
+		$prompt_builder = new WP_AI_Client_Prompt_Builder( $registry );
+
+		$test_cases = array(
+			'with_text'                   => 'withText',
+			'using_system_instruction'    => 'usingSystemInstruction',
+			'using_max_tokens'            => 'usingMaxTokens',
+			'as_output_mime_type'         => 'asOutputMimeType',
+			'using_model_config'          => 'usingModelConfig',
+			'with_message_parts'          => 'withMessageParts',
+			'using_stop_sequences'        => 'usingStopSequences',
+			'using_candidate_count'       => 'usingCandidateCount',
+			'using_function_declarations' => 'usingFunctionDeclarations',
+		);
+
+		$reflection_class  = new ReflectionClass( WP_AI_Client_Prompt_Builder::class );
+		$conversion_method = $reflection_class->getMethod( 'snake_to_camel_case' );
+
+		foreach ( $test_cases as $snake_case => $expected_camel_case ) {
+			$actual_camel_case = $conversion_method->invoke( $prompt_builder, $snake_case );
+			$this->assertSame( $expected_camel_case, $actual_camel_case, "Failed converting {$snake_case} to {$expected_camel_case}" );
+		}
+	}
+
+	/**
+	 * Test that calling a non-existent method returns WP_Error on termination.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_invalid_method_returns_wp_error() {
+		$registry       = AiClient::defaultRegistry();
+		$prompt_builder = new WP_AI_Client_Prompt_Builder( $registry );
+
+		// Invalid method call stores error but returns $this for chaining.
+		$result = $prompt_builder->non_existent_method();
+		$this->assertSame( $prompt_builder, $result );
+
+		// Calling a terminate method should return the stored WP_Error.
+		$result = $prompt_builder->generate_text();
+		$this->assertWPError( $result );
+		$this->assertSame( 'prompt_builder_error', $result->get_error_code() );
+		$this->assertStringContainsString( 'non_existent_method does not exist', $result->get_error_message() );
+	}
+
+	/**
+	 * Test that get_builder_callable returns a valid callable.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_get_builder_callable() {
+		$registry       = AiClient::defaultRegistry();
+		$prompt_builder = new WP_AI_Client_Prompt_Builder( $registry );
+
+		$reflection_class = new ReflectionClass( WP_AI_Client_Prompt_Builder::class );
+		$callable_method  = $reflection_class->getMethod( 'get_builder_callable' );
+
+		$callable = $callable_method->invoke( $prompt_builder, 'with_text' );
+		$this->assertTrue( is_callable( $callable ), 'get_builder_callable should return a valid callable' );
+
+		$this->assertIsArray( $callable );
+		$this->assertCount( 2, $callable );
+		$this->assertInstanceOf( PromptBuilder::class, $callable[0] );
+		$this->assertSame( 'withText', $callable[1] );
+	}
+
+	/**
+	 * Test that the wrapped builder is properly configured with the registry.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_wrapped_builder_has_correct_registry() {
+		$registry       = AiClient::defaultRegistry();
+		$prompt_builder = new WP_AI_Client_Prompt_Builder( $registry );
+
+		$reflection_class = new ReflectionClass( WP_AI_Client_Prompt_Builder::class );
+		$builder_property = $reflection_class->getProperty( 'builder' );
+
+		$wrapped_builder = $builder_property->getValue( $prompt_builder );
+
+		$wrapped_builder_reflection = new ReflectionClass( get_class( $wrapped_builder ) );
+		$registry_property          = $wrapped_builder_reflection->getProperty( 'registry' );
+
+		$this->assertSame( $registry, $registry_property->getValue( $wrapped_builder ), 'Wrapped builder should have the same registry' );
+	}
+
+	/**
+	 * Test method chaining with with_history.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_method_chaining_with_history() {
+		$registry       = AiClient::defaultRegistry();
+		$prompt_builder = new WP_AI_Client_Prompt_Builder( $registry );
+
+		$message1 = Message::fromArray(
+			array(
+				'role'  => 'user',
+				'parts' => array(
+					array(
+						'text' => 'Hello',
+					),
+				),
+			)
+		);
+		$message2 = Message::fromArray(
+			array(
+				'role'  => 'user',
+				'parts' => array(
+					array(
+						'text' => 'How are you?',
+					),
+				),
+			)
+		);
+
+		$result = $prompt_builder->with_history( $message1, $message2 );
+		$this->assertSame( $prompt_builder, $result, 'with_history should return the decorator instance' );
+		$this->assertInstanceOf( WP_AI_Client_Prompt_Builder::class, $result );
+	}
+
+	/**
+	 * Test method chaining with using_model_config.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_method_chaining_with_model_config() {
+		$registry       = AiClient::defaultRegistry();
+		$prompt_builder = new WP_AI_Client_Prompt_Builder( $registry );
+
+		$config = new ModelConfig( array( 'maxTokens' => 100 ) );
+
+		$result = $prompt_builder->using_model_config( $config );
+		$this->assertSame( $prompt_builder, $result, 'using_model_config should return the decorator instance' );
+		$this->assertInstanceOf( WP_AI_Client_Prompt_Builder::class, $result );
+	}
+
+	/**
+	 * Tests constructor with no prompt.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_constructor_with_no_prompt() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+
+		$messages = $this->get_wrapped_prompt_builder_property_value( $builder, 'messages' );
+		$this->assertEmpty( $messages );
+	}
+
+	/**
+	 * Tests constructor with string prompt.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_constructor_with_string_prompt() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry, 'Hello, world!' );
+
+		/** @var list<Message> $messages */
+		$messages = $this->get_wrapped_prompt_builder_property_value( $builder, 'messages' );
+
+		$this->assertCount( 1, $messages );
+		$this->assertInstanceOf( Message::class, $messages[0] );
+		$this->assertEquals( 'Hello, world!', $messages[0]->getParts()[0]->getText() );
+	}
+
+	/**
+	 * Tests constructor with MessagePart prompt.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_constructor_with_message_part_prompt() {
+		$part    = new MessagePart( 'Test message' );
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry, $part );
+
+		/** @var list<Message> $messages */
+		$messages = $this->get_wrapped_prompt_builder_property_value( $builder, 'messages' );
+
+		$this->assertCount( 1, $messages );
+		$this->assertInstanceOf( Message::class, $messages[0] );
+		$this->assertEquals( 'Test message', $messages[0]->getParts()[0]->getText() );
+	}
+
+	/**
+	 * Tests constructor with Message prompt.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_constructor_with_message_prompt() {
+		$message = new UserMessage( array( new MessagePart( 'User message' ) ) );
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry, $message );
+
+		/** @var list<Message> $messages */
+		$messages = $this->get_wrapped_prompt_builder_property_value( $builder, 'messages' );
+
+		$this->assertCount( 1, $messages );
+		$this->assertSame( $message, $messages[0] );
+	}
+
+	/**
+	 * Tests constructor with list of Messages.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_constructor_with_messages_list() {
+		$messages = array(
+			new UserMessage( array( new MessagePart( 'First' ) ) ),
+			new ModelMessage( array( new MessagePart( 'Second' ) ) ),
+			new UserMessage( array( new MessagePart( 'Third' ) ) ),
+		);
+		$builder  = new WP_AI_Client_Prompt_Builder( $this->registry, $messages );
+
+		/** @var list<Message> $actual_messages */
+		$actual_messages = $this->get_wrapped_prompt_builder_property_value( $builder, 'messages' );
+
+		$this->assertCount( 3, $actual_messages );
+		$this->assertSame( $messages, $actual_messages );
+	}
+
+	/**
+	 * Tests constructor with MessageArrayShape.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_constructor_with_message_array_shape() {
+		$message_array = array(
+			'role'  => 'user',
+			'parts' => array(
+				array(
+					'type' => 'text',
+					'text' => 'Hello from array',
+				),
+			),
+		);
+		$builder       = new WP_AI_Client_Prompt_Builder( $this->registry, $message_array );
+
+		/** @var list<Message> $messages */
+		$messages = $this->get_wrapped_prompt_builder_property_value( $builder, 'messages' );
+
+		$this->assertCount( 1, $messages );
+		$this->assertInstanceOf( Message::class, $messages[0] );
+		$this->assertEquals( 'Hello from array', $messages[0]->getParts()[0]->getText() );
+	}
+
+	/**
+	 * Tests withText method.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_with_text() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$result  = $builder->with_text( 'Some text' );
+
+		$this->assertSame( $builder, $result );
+
+		/** @var list<Message> $messages */
+		$messages = $this->get_wrapped_prompt_builder_property_value( $builder, 'messages' );
+
+		$this->assertCount( 1, $messages );
+		$this->assertEquals( 'Some text', $messages[0]->getParts()[0]->getText() );
+	}
+
+	/**
+	 * Tests withText appends to existing user message.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_with_text_appends_to_existing_user_message() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry, 'Initial text' );
+		$builder->with_text( ' Additional text' );
+
+		/** @var list<Message> $messages */
+		$messages = $this->get_wrapped_prompt_builder_property_value( $builder, 'messages' );
+
+		$this->assertCount( 1, $messages );
+		$parts = $messages[0]->getParts();
+		$this->assertCount( 2, $parts );
+		$this->assertEquals( 'Initial text', $parts[0]->getText() );
+		$this->assertEquals( ' Additional text', $parts[1]->getText() );
+	}
+
+	/**
+	 * Tests withFile method with base64 data.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_with_inline_file() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$base64  = 'iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mNkYPhfDwAChwGA60e6kgAAAABJRU5ErkJggg==';
+		$result  = $builder->with_file( $base64, 'image/png' );
+
+		$this->assertSame( $builder, $result );
+
+		/** @var list<Message> $messages */
+		$messages = $this->get_wrapped_prompt_builder_property_value( $builder, 'messages' );
+
+		$this->assertCount( 1, $messages );
+		$file = $messages[0]->getParts()[0]->getFile();
+		$this->assertInstanceOf( File::class, $file );
+		$this->assertEquals( 'data:image/png;base64,' . $base64, $file->getDataUri() );
+		$this->assertEquals( 'image/png', $file->getMimeType() );
+	}
+
+	/**
+	 * Tests withFile method with remote URL.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_with_remote_file() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$result  = $builder->with_file( 'https://example.com/image.jpg', 'image/jpeg' );
+
+		$this->assertSame( $builder, $result );
+
+		/** @var list<Message> $messages */
+		$messages = $this->get_wrapped_prompt_builder_property_value( $builder, 'messages' );
+
+		$this->assertCount( 1, $messages );
+		$file = $messages[0]->getParts()[0]->getFile();
+		$this->assertInstanceOf( File::class, $file );
+		$this->assertEquals( 'https://example.com/image.jpg', $file->getUrl() );
+		$this->assertEquals( 'image/jpeg', $file->getMimeType() );
+	}
+
+	/**
+	 * Tests withFile with data URI.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_with_inline_file_data_uri() {
+		$builder  = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$data_uri = 'data:image/jpeg;base64,/9j/4AAQSkZJRg==';
+		$result   = $builder->with_file( $data_uri );
+
+		$this->assertSame( $builder, $result );
+
+		/** @var list<Message> $messages */
+		$messages = $this->get_wrapped_prompt_builder_property_value( $builder, 'messages' );
+
+		$this->assertCount( 1, $messages );
+		$file = $messages[0]->getParts()[0]->getFile();
+		$this->assertInstanceOf( File::class, $file );
+		$this->assertEquals( 'image/jpeg', $file->getMimeType() );
+	}
+
+	/**
+	 * Tests withFile with URL without explicit MIME type.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_with_remote_file_without_mime_type() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$result  = $builder->with_file( 'https://example.com/audio.mp3' );
+
+		$this->assertSame( $builder, $result );
+
+		/** @var list<Message> $messages */
+		$messages = $this->get_wrapped_prompt_builder_property_value( $builder, 'messages' );
+
+		$this->assertCount( 1, $messages );
+		$file = $messages[0]->getParts()[0]->getFile();
+		$this->assertInstanceOf( File::class, $file );
+		$this->assertEquals( 'https://example.com/audio.mp3', $file->getUrl() );
+		$this->assertEquals( 'audio/mpeg', $file->getMimeType() );
+	}
+
+	/**
+	 * Tests withFunctionResponse method.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_with_function_response() {
+		$function_response = new FunctionResponse( 'func_id', 'func_name', array( 'result' => 'data' ) );
+		$builder           = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$result            = $builder->with_function_response( $function_response );
+
+		$this->assertSame( $builder, $result );
+
+		/** @var list<Message> $messages */
+		$messages = $this->get_wrapped_prompt_builder_property_value( $builder, 'messages' );
+
+		$this->assertCount( 1, $messages );
+		$this->assertSame( $function_response, $messages[0]->getParts()[0]->getFunctionResponse() );
+	}
+
+	/**
+	 * Tests withMessageParts method.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_with_message_parts() {
+		$part1 = new MessagePart( 'Part 1' );
+		$part2 = new MessagePart( 'Part 2' );
+		$part3 = new MessagePart( 'Part 3' );
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$result  = $builder->with_message_parts( $part1, $part2, $part3 );
+
+		$this->assertSame( $builder, $result );
+
+		/** @var list<Message> $messages */
+		$messages = $this->get_wrapped_prompt_builder_property_value( $builder, 'messages' );
+
+		$this->assertCount( 1, $messages );
+		$parts = $messages[0]->getParts();
+		$this->assertCount( 3, $parts );
+		$this->assertEquals( 'Part 1', $parts[0]->getText() );
+		$this->assertEquals( 'Part 2', $parts[1]->getText() );
+		$this->assertEquals( 'Part 3', $parts[2]->getText() );
+	}
+
+	/**
+	 * Tests withHistory method.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_with_history() {
+		$history = array(
+			new UserMessage( array( new MessagePart( 'User 1' ) ) ),
+			new ModelMessage( array( new MessagePart( 'Model 1' ) ) ),
+			new UserMessage( array( new MessagePart( 'User 2' ) ) ),
+		);
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$result  = $builder->with_history( ...$history );
+
+		$this->assertSame( $builder, $result );
+
+		/** @var list<Message> $messages */
+		$messages = $this->get_wrapped_prompt_builder_property_value( $builder, 'messages' );
+
+		$this->assertCount( 3, $messages );
+		$this->assertEquals( 'User 1', $messages[0]->getParts()[0]->getText() );
+		$this->assertEquals( 'Model 1', $messages[1]->getParts()[0]->getText() );
+		$this->assertEquals( 'User 2', $messages[2]->getParts()[0]->getText() );
+	}
+
+	/**
+	 * Tests usingModel method.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_using_model() {
+		$model_config = new ModelConfig();
+		$model        = $this->createMock( ModelInterface::class );
+		$model->method( 'getConfig' )->willReturn( $model_config );
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$result  = $builder->using_model( $model );
+
+		$this->assertSame( $builder, $result );
+
+		/** @var ModelInterface $actual_model */
+		$actual_model = $this->get_wrapped_prompt_builder_property_value( $builder, 'model' );
+		$this->assertSame( $model, $actual_model );
+	}
+
+	/**
+	 * Tests constructor with list of string parts.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_constructor_with_string_parts_list() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry, array( 'Part 1', 'Part 2', 'Part 3' ) );
+
+		/** @var list<Message> $messages */
+		$messages = $this->get_wrapped_prompt_builder_property_value( $builder, 'messages' );
+
+		$this->assertCount( 1, $messages );
+		$this->assertInstanceOf( Message::class, $messages[0] );
+		$parts = $messages[0]->getParts();
+		$this->assertCount( 3, $parts );
+		$this->assertEquals( 'Part 1', $parts[0]->getText() );
+		$this->assertEquals( 'Part 2', $parts[1]->getText() );
+		$this->assertEquals( 'Part 3', $parts[2]->getText() );
+	}
+
+	/**
+	 * Tests constructor with mixed parts list.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_constructor_with_mixed_parts_list() {
+		$part1       = new MessagePart( 'Part 1' );
+		$part2_array = array(
+			'type' => 'text',
+			'text' => 'Part 2',
+		);
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry, array( 'String part', $part1, $part2_array ) );
+
+		/** @var list<Message> $messages */
+		$messages = $this->get_wrapped_prompt_builder_property_value( $builder, 'messages' );
+
+		$this->assertCount( 1, $messages );
+		$parts = $messages[0]->getParts();
+		$this->assertCount( 3, $parts );
+		$this->assertEquals( 'String part', $parts[0]->getText() );
+		$this->assertEquals( 'Part 1', $parts[1]->getText() );
+		$this->assertEquals( 'Part 2', $parts[2]->getText() );
+	}
+
+	/**
+	 * Tests full method chaining.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_method_chaining() {
+		$model = $this->createMock( ModelInterface::class );
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$result  = $builder
+			->with_text( 'Start of prompt' )
+			->with_file( 'https://example.com/img.jpg', 'image/jpeg' )
+			->using_model( $model )
+			->using_system_instruction( 'Be helpful' )
+			->using_max_tokens( 500 )
+			->using_temperature( 0.8 )
+			->using_top_p( 0.95 )
+			->using_top_k( 50 )
+			->using_candidate_count( 2 )
+			->as_json_response();
+
+		$this->assertSame( $builder, $result );
+
+		/** @var list<Message> $messages */
+		$messages = $this->get_wrapped_prompt_builder_property_value( $builder, 'messages' );
+		$this->assertCount( 1, $messages );
+		$this->assertCount( 2, $messages[0]->getParts() );
+
+		/** @var ModelInterface $actual_model */
+		$actual_model = $this->get_wrapped_prompt_builder_property_value( $builder, 'model' );
+		$this->assertSame( $model, $actual_model );
+
+		/** @var ModelConfig $config */
+		$config = $this->get_wrapped_prompt_builder_property_value( $builder, 'modelConfig' );
+
+		$this->assertEquals( 'Be helpful', $config->getSystemInstruction() );
+		$this->assertEquals( 500, $config->getMaxTokens() );
+		$this->assertEquals( 0.8, $config->getTemperature() );
+		$this->assertEquals( 0.95, $config->getTopP() );
+		$this->assertEquals( 50, $config->getTopK() );
+		$this->assertEquals( 2, $config->getCandidateCount() );
+		$this->assertEquals( 'application/json', $config->getOutputMimeType() );
+	}
+
+	/**
+	 * Tests usingModelPreference skips unavailable model IDs and falls back.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_using_model_preference_skips_unavailable_model_id() {
+		$result            = $this->create_test_result( 'Fallback model result' );
+		$other_metadata    = $this->create_text_model_metadata_with_input_support( 'other-id' );
+		$fallback_metadata = $this->create_text_model_metadata_with_input_support( 'fallback-id' );
+		$model             = $this->create_mock_text_generation_model( $result, $fallback_metadata );
+
+		$this->registry->expects( $this->once() )
+			->method( 'getProviderId' )
+			->with( 'test-provider' )
+			->willReturn( 'test-provider' );
+
+		$this->registry->expects( $this->once() )
+			->method( 'findProviderModelsMetadataForSupport' )
+			->with( 'test-provider', $this->isInstanceOf( ModelRequirements::class ) )
+			->willReturn( array( $other_metadata, $fallback_metadata ) );
+
+		$this->registry->expects( $this->once() )
+			->method( 'getProviderModel' )
+			->with( 'test-provider', 'fallback-id', $this->isInstanceOf( ModelConfig::class ) )
+			->willReturn( $model );
+
+		$this->registry->expects( $this->never() )
+			->method( 'findModelsMetadataForSupport' );
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry, 'Test prompt' );
+		$builder->using_provider( 'test-provider' );
+		$builder->using_model_preference( 'missing-id', 'fallback-id' );
+
+		$actual_result = $builder->generate_text_result();
+
+		$this->assertSame( $result, $actual_result );
+	}
+
+	/**
+	 * Tests usingModelPreference falls back to discovery when no preferences available.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_using_model_preference_falls_back_to_discovery() {
+		$result                   = $this->create_test_result( 'Discovered model result' );
+		$metadata                 = $this->create_text_model_metadata_with_input_support( 'discovered-id' );
+		$provider_metadata        = $this->create_test_provider_metadata();
+		$provider_models_metadata = new ProviderModelsMetadata( $provider_metadata, array( $metadata ) );
+
+		$model = $this->create_mock_text_generation_model( $result, $metadata );
+
+		$this->registry->expects( $this->once() )
+			->method( 'findModelsMetadataForSupport' )
+			->with( $this->isInstanceOf( ModelRequirements::class ) )
+			->willReturn( array( $provider_models_metadata ) );
+
+		$this->registry->expects( $this->once() )
+			->method( 'getProviderModel' )
+			->with( $provider_metadata->getId(), 'discovered-id', $this->isInstanceOf( ModelConfig::class ) )
+			->willReturn( $model );
+
+		$this->registry->expects( $this->never() )
+			->method( 'findProviderModelsMetadataForSupport' );
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry, 'Test prompt' );
+		$builder->using_model_preference( 'unavailable-model' );
+
+		$actual_result = $builder->generate_text_result();
+
+		$this->assertSame( $result, $actual_result );
+	}
+
+	/**
+	 * Tests usingModelPreference respects priority order when multiple preferred models are available.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_using_model_preference_respects_order_when_multiple_available() {
+		$result                 = $this->create_test_result( 'Second choice result' );
+		$second_choice_metadata = $this->create_text_model_metadata_with_input_support( 'second-choice' );
+		$third_choice_metadata  = $this->create_text_model_metadata_with_input_support( 'third-choice' );
+		$provider_metadata      = $this->create_test_provider_metadata();
+
+		$model = $this->create_mock_text_generation_model( $result, $second_choice_metadata );
+
+		$provider_models_metadata = new ProviderModelsMetadata(
+			$provider_metadata,
+			array( $third_choice_metadata, $second_choice_metadata )
+		);
+
+		$this->registry->expects( $this->once() )
+			->method( 'findModelsMetadataForSupport' )
+			->with( $this->isInstanceOf( ModelRequirements::class ) )
+			->willReturn( array( $provider_models_metadata ) );
+
+		$this->registry->expects( $this->once() )
+			->method( 'getProviderModel' )
+			->with( $provider_metadata->getId(), 'second-choice', $this->isInstanceOf( ModelConfig::class ) )
+			->willReturn( $model );
+
+		$this->registry->expects( $this->never() )
+			->method( 'findProviderModelsMetadataForSupport' );
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry, 'Test prompt' );
+		$builder->using_model_preference( 'first-choice', 'second-choice', 'third-choice' );
+
+		$actual_result = $builder->generate_text_result();
+
+		$this->assertSame( $result, $actual_result );
+	}
+
+	/**
+	 * Tests usingModelPreference rejects invalid preference types, returning WP_Error.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_using_model_preference_with_invalid_type_returns_wp_error() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+
+		$builder->using_model_preference( 123 );
+		$result = $builder->generate_text_result();
+
+		$this->assertWPError( $result );
+		$this->assertSame( 'prompt_builder_error', $result->get_error_code() );
+		$this->assertStringContainsString(
+			'Model preferences must be model identifiers',
+			$result->get_error_message()
+		);
+	}
+
+	/**
+	 * Tests usingModelPreference rejects malformed preference tuples, returning WP_Error.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_using_model_preference_with_invalid_tuple_returns_wp_error() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+
+		$builder->using_model_preference(
+			array(
+				'provider' => 'test',
+				'model'    => 'id',
+			)
+		);
+		$result = $builder->generate_text_result();
+
+		$this->assertWPError( $result );
+		$this->assertSame( 'prompt_builder_error', $result->get_error_code() );
+		$this->assertStringContainsString(
+			'Model preference tuple must contain model identifier and provider ID.',
+			$result->get_error_message()
+		);
+	}
+
+	/**
+	 * Tests usingModelPreference rejects empty preference identifiers, returning WP_Error.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_using_model_preference_with_empty_identifier_returns_wp_error() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+
+		$builder->using_model_preference( '   ' );
+		$result = $builder->generate_text_result();
+
+		$this->assertWPError( $result );
+		$this->assertSame( 'prompt_builder_error', $result->get_error_code() );
+		$this->assertStringContainsString(
+			'Model preference identifiers cannot be empty.',
+			$result->get_error_message()
+		);
+	}
+
+	/**
+	 * Tests usingModelPreference rejects calls without preferences, returning WP_Error.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_using_model_preference_without_arguments_returns_wp_error() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+
+		$builder->using_model_preference();
+		$result = $builder->generate_text_result();
+
+		$this->assertWPError( $result );
+		$this->assertSame( 'prompt_builder_error', $result->get_error_code() );
+		$this->assertStringContainsString(
+			'At least one model preference must be provided.',
+			$result->get_error_message()
+		);
+	}
+
+	/**
+	 * Tests usingModelConfig method.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_using_model_config() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+
+		$builder->using_system_instruction( 'Builder instruction' )
+				->using_max_tokens( 500 )
+				->using_temperature( 0.5 );
+
+		$config = new ModelConfig();
+		$config->setSystemInstruction( 'Config instruction' );
+		$config->setMaxTokens( 1000 );
+		$config->setTopP( 0.9 );
+		$config->setTopK( 40 );
+
+		$result = $builder->using_model_config( $config );
+
+		$this->assertSame( $builder, $result );
+
+		/** @var ModelConfig $merged_config */
+		$merged_config = $this->get_wrapped_prompt_builder_property_value( $builder, 'modelConfig' );
+
+		$this->assertEquals( 'Builder instruction', $merged_config->getSystemInstruction() );
+		$this->assertEquals( 500, $merged_config->getMaxTokens() );
+		$this->assertEquals( 0.5, $merged_config->getTemperature() );
+		$this->assertEquals( 0.9, $merged_config->getTopP() );
+		$this->assertEquals( 40, $merged_config->getTopK() );
+	}
+
+	/**
+	 * Tests usingModelConfig with custom options.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_using_model_config_with_custom_options() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+
+		$config = new ModelConfig();
+		$config->setCustomOption( 'stopSequences', array( 'CONFIG_STOP' ) );
+		$config->setCustomOption( 'otherOption', 'value' );
+
+		$builder->using_model_config( $config );
+
+		/** @var ModelConfig $merged_config */
+		$merged_config  = $this->get_wrapped_prompt_builder_property_value( $builder, 'modelConfig' );
+		$custom_options = $merged_config->getCustomOptions();
+
+		$this->assertArrayHasKey( 'stopSequences', $custom_options );
+		$this->assertIsArray( $custom_options['stopSequences'] );
+		$this->assertEquals( array( 'CONFIG_STOP' ), $custom_options['stopSequences'] );
+		$this->assertArrayHasKey( 'otherOption', $custom_options );
+		$this->assertEquals( 'value', $custom_options['otherOption'] );
+
+		$builder->using_stop_sequences( 'STOP' );
+
+		/** @var ModelConfig $merged_config */
+		$merged_config  = $this->get_wrapped_prompt_builder_property_value( $builder, 'modelConfig' );
+		$custom_options = $merged_config->getCustomOptions();
+
+		$this->assertArrayHasKey( 'stopSequences', $custom_options );
+		$this->assertIsArray( $custom_options['stopSequences'] );
+		$this->assertEquals( array( 'STOP' ), $custom_options['stopSequences'] );
+		$this->assertArrayHasKey( 'otherOption', $custom_options );
+		$this->assertEquals( 'value', $custom_options['otherOption'] );
+	}
+
+	/**
+	 * Tests usingProvider method.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_using_provider() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$result  = $builder->using_provider( 'test-provider' );
+
+		$this->assertSame( $builder, $result );
+
+		$actual_provider = $this->get_wrapped_prompt_builder_property_value( $builder, 'providerIdOrClassName' );
+		$this->assertEquals( 'test-provider', $actual_provider );
+	}
+
+	/**
+	 * Tests usingSystemInstruction method.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_using_system_instruction() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$result  = $builder->using_system_instruction( 'You are a helpful assistant.' );
+
+		$this->assertSame( $builder, $result );
+
+		/** @var ModelConfig $config */
+		$config = $this->get_wrapped_prompt_builder_property_value( $builder, 'modelConfig' );
+
+		$this->assertEquals( 'You are a helpful assistant.', $config->getSystemInstruction() );
+	}
+
+	/**
+	 * Tests usingMaxTokens method.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_using_max_tokens() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$result  = $builder->using_max_tokens( 1000 );
+
+		$this->assertSame( $builder, $result );
+
+		/** @var ModelConfig $config */
+		$config = $this->get_wrapped_prompt_builder_property_value( $builder, 'modelConfig' );
+
+		$this->assertEquals( 1000, $config->getMaxTokens() );
+	}
+
+	/**
+	 * Tests usingTemperature method.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_using_temperature() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$result  = $builder->using_temperature( 0.7 );
+
+		$this->assertSame( $builder, $result );
+
+		/** @var ModelConfig $config */
+		$config = $this->get_wrapped_prompt_builder_property_value( $builder, 'modelConfig' );
+
+		$this->assertEquals( 0.7, $config->getTemperature() );
+	}
+
+	/**
+	 * Tests usingTopP method.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_using_top_p() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$result  = $builder->using_top_p( 0.9 );
+
+		$this->assertSame( $builder, $result );
+
+		/** @var ModelConfig $config */
+		$config = $this->get_wrapped_prompt_builder_property_value( $builder, 'modelConfig' );
+
+		$this->assertEquals( 0.9, $config->getTopP() );
+	}
+
+	/**
+	 * Tests usingTopK method.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_using_top_k() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$result  = $builder->using_top_k( 40 );
+
+		$this->assertSame( $builder, $result );
+
+		/** @var ModelConfig $config */
+		$config = $this->get_wrapped_prompt_builder_property_value( $builder, 'modelConfig' );
+
+		$this->assertEquals( 40, $config->getTopK() );
+	}
+
+	/**
+	 * Tests usingStopSequences method.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_using_stop_sequences() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$result  = $builder->using_stop_sequences( 'STOP', 'END', '###' );
+
+		$this->assertSame( $builder, $result );
+
+		/** @var ModelConfig $config */
+		$config = $this->get_wrapped_prompt_builder_property_value( $builder, 'modelConfig' );
+
+		$custom_options = $config->getCustomOptions();
+		$this->assertArrayHasKey( 'stopSequences', $custom_options );
+		$this->assertEquals( array( 'STOP', 'END', '###' ), $custom_options['stopSequences'] );
+	}
+
+	/**
+	 * Tests usingCandidateCount method.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_using_candidate_count() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$result  = $builder->using_candidate_count( 3 );
+
+		$this->assertSame( $builder, $result );
+
+		/** @var ModelConfig $config */
+		$config = $this->get_wrapped_prompt_builder_property_value( $builder, 'modelConfig' );
+
+		$this->assertEquals( 3, $config->getCandidateCount() );
+	}
+
+	/**
+	 * Tests asOutputMimeType method.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_using_output_mime() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$result  = $builder->as_output_mime_type( 'application/json' );
+
+		$this->assertSame( $builder, $result );
+
+		/** @var ModelConfig $config */
+		$config = $this->get_wrapped_prompt_builder_property_value( $builder, 'modelConfig' );
+
+		$this->assertEquals( 'application/json', $config->getOutputMimeType() );
+	}
+
+	/**
+	 * Tests asOutputSchema method.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_using_output_schema() {
+		$schema = array(
+			'type'       => 'object',
+			'properties' => array(
+				'name' => array( 'type' => 'string' ),
+			),
+		);
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$result  = $builder->as_output_schema( $schema );
+
+		$this->assertSame( $builder, $result );
+
+		/** @var ModelConfig $config */
+		$config = $this->get_wrapped_prompt_builder_property_value( $builder, 'modelConfig' );
+
+		$this->assertEquals( $schema, $config->getOutputSchema() );
+	}
+
+	/**
+	 * Tests asOutputModalities method.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_using_output_modalities() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$result  = $builder->as_output_modalities(
+			ModalityEnum::text(),
+			ModalityEnum::image()
+		);
+
+		$this->assertSame( $builder, $result );
+
+		/** @var ModelConfig $config */
+		$config = $this->get_wrapped_prompt_builder_property_value( $builder, 'modelConfig' );
+
+		$modalities = $config->getOutputModalities();
+		$this->assertCount( 2, $modalities );
+		$this->assertTrue( $modalities[0]->isText() );
+		$this->assertTrue( $modalities[1]->isImage() );
+	}
+
+	/**
+	 * Tests asJsonResponse method.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_as_json_response() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$result  = $builder->as_json_response();
+
+		$this->assertSame( $builder, $result );
+
+		/** @var ModelConfig $config */
+		$config = $this->get_wrapped_prompt_builder_property_value( $builder, 'modelConfig' );
+
+		$this->assertEquals( 'application/json', $config->getOutputMimeType() );
+	}
+
+	/**
+	 * Tests asJsonResponse with schema.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_as_json_response_with_schema() {
+		$schema  = array( 'type' => 'array' );
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$result  = $builder->as_json_response( $schema );
+
+		$this->assertSame( $builder, $result );
+
+		/** @var ModelConfig $config */
+		$config = $this->get_wrapped_prompt_builder_property_value( $builder, 'modelConfig' );
+
+		$this->assertEquals( 'application/json', $config->getOutputMimeType() );
+		$this->assertEquals( $schema, $config->getOutputSchema() );
+	}
+
+	/**
+	 * Tests validateMessages with empty messages returns WP_Error.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_validate_messages_empty_returns_wp_error() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+
+		$result = $builder->generate_result();
+
+		$this->assertWPError( $result );
+		$this->assertSame( 'prompt_builder_error', $result->get_error_code() );
+		$this->assertStringContainsString( 'Cannot generate from an empty prompt', $result->get_error_message() );
+	}
+
+	/**
+	 * Tests validateMessages with non-user first message returns WP_Error.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_validate_messages_non_user_first_returns_wp_error() {
+		$builder = new WP_AI_Client_Prompt_Builder(
+			$this->registry,
+			array(
+				new ModelMessage( array( new MessagePart( 'Model says hi' ) ) ),
+				new UserMessage( array( new MessagePart( 'User response' ) ) ),
+			)
+		);
+
+		$result = $builder->generate_result();
+
+		$this->assertWPError( $result );
+		$this->assertSame( 'prompt_builder_error', $result->get_error_code() );
+		$this->assertStringContainsString( 'The first message must be from a user role', $result->get_error_message() );
+	}
+
+	/**
+	 * Tests validateMessages with non-user last message returns WP_Error.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_validate_messages_non_user_last_returns_wp_error() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$builder->with_text( 'Initial user message' );
+
+		$builder->with_history(
+			new UserMessage( array( new MessagePart( 'Historical user message' ) ) ),
+			new ModelMessage( array( new MessagePart( 'Historical model response' ) ) )
+		);
+
+		// Manually add a model message as the last message.
+		$reflection_class = new ReflectionClass( WP_AI_Client_Prompt_Builder::class );
+		$builder_property = $reflection_class->getProperty( 'builder' );
+
+		$wrapped_builder   = $builder_property->getValue( $builder );
+		$reflection_class2 = new ReflectionClass( get_class( $wrapped_builder ) );
+		$messages_property = $reflection_class2->getProperty( 'messages' );
+
+		$messages   = $messages_property->getValue( $wrapped_builder );
+		$messages[] = new ModelMessage( array( new MessagePart( 'Final model message' ) ) );
+		$messages_property->setValue( $wrapped_builder, $messages );
+
+		$result = $builder->generate_result();
+
+		$this->assertWPError( $result );
+		$this->assertSame( 'prompt_builder_error', $result->get_error_code() );
+		$this->assertStringContainsString( 'The last message must be from a user role', $result->get_error_message() );
+	}
+
+	/**
+	 * Tests parseMessage with empty string returns WP_Error on termination.
+	 *
+	 * The SDK constructor throws immediately for empty strings, so the exception
+	 * is caught in the constructor and stored.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_parse_message_empty_string_returns_wp_error() {
+		// The empty string exception is thrown by the SDK's PromptBuilder constructor,
+		// which happens before our __call() error handling. We must catch it manually.
+		try {
+			$builder = new WP_AI_Client_Prompt_Builder( $this->registry, '   ' );
+			// If we get here, the SDK didn't throw. Test would need adjusting.
+			$result = $builder->generate_result();
+			$this->assertWPError( $result );
+		} catch ( InvalidArgumentException $e ) {
+			$this->assertStringContainsString( 'Cannot create a message from an empty string', $e->getMessage() );
+		}
+	}
+
+	/**
+	 * Tests parseMessage with empty array returns WP_Error on termination.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_parse_message_empty_array_returns_wp_error() {
+		try {
+			$builder = new WP_AI_Client_Prompt_Builder( $this->registry, array() );
+			$result  = $builder->generate_result();
+			$this->assertWPError( $result );
+		} catch ( InvalidArgumentException $e ) {
+			$this->assertStringContainsString( 'Cannot create a message from an empty array', $e->getMessage() );
+		}
+	}
+
+	/**
+	 * Tests parseMessage with invalid type returns WP_Error on termination.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_parse_message_invalid_type_returns_wp_error() {
+		try {
+			$builder = new WP_AI_Client_Prompt_Builder( $this->registry, 123 );
+			$result  = $builder->generate_result();
+			$this->assertWPError( $result );
+		} catch ( InvalidArgumentException $e ) {
+			$this->assertStringContainsString( 'Input must be a string, MessagePart, MessagePartArrayShape', $e->getMessage() );
+		}
+	}
+
+	/**
+	 * Tests generateResult with text output modality.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_generate_result_with_text_modality() {
+		$result = $this->createMock( GenerativeAiResult::class );
+
+		$metadata = $this->createMock( ModelMetadata::class );
+		$metadata->method( 'getId' )->willReturn( 'test-model' );
+
+		$model = $this->create_mock_text_generation_model( $result, $metadata );
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry, 'Test prompt' );
+		$builder->using_model( $model );
+
+		$actual_result = $builder->generate_result();
+		$this->assertSame( $result, $actual_result );
+	}
+
+	/**
+	 * Tests generateResult with image output modality.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_generate_result_with_image_modality() {
+		$result = new GenerativeAiResult(
+			'test-result',
+			array(
+				new Candidate(
+					new ModelMessage( array( new MessagePart( new File( 'data:image/png;base64,iVBORw0KGgo=', 'image/png' ) ) ) ),
+					FinishReasonEnum::stop()
+				),
+			),
+			new TokenUsage( 100, 50, 150 ),
+			$this->create_test_provider_metadata(),
+			$this->create_test_text_model_metadata()
+		);
+
+		$metadata = $this->createMock( ModelMetadata::class );
+		$metadata->method( 'getId' )->willReturn( 'test-model' );
+
+		$model = $this->create_mock_image_generation_model( $result, $metadata );
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry, 'Generate an image' );
+		$builder->using_model( $model );
+		$builder->as_output_modalities( ModalityEnum::image() );
+
+		$actual_result = $builder->generate_result();
+		$this->assertSame( $result, $actual_result );
+	}
+
+	/**
+	 * Tests generateResult with audio output modality.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_generate_result_with_audio_modality() {
+		$result = new GenerativeAiResult(
+			'test-result',
+			array(
+				new Candidate(
+					new ModelMessage( array( new MessagePart( new File( 'data:audio/wav;base64,UklGRigE=', 'audio/wav' ) ) ) ),
+					FinishReasonEnum::stop()
+				),
+			),
+			new TokenUsage( 100, 50, 150 ),
+			$this->create_test_provider_metadata(),
+			$this->create_test_text_model_metadata()
+		);
+
+		$metadata = $this->createMock( ModelMetadata::class );
+		$metadata->method( 'getId' )->willReturn( 'test-model' );
+
+		$model = $this->create_mock_speech_generation_model( $result, $metadata );
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry, 'Generate speech' );
+		$builder->using_model( $model );
+		$builder->as_output_modalities( ModalityEnum::audio() );
+
+		$actual_result = $builder->generate_result();
+		$this->assertSame( $result, $actual_result );
+	}
+
+	/**
+	 * Tests generateResult with multimodal output.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_generate_result_with_multimodal_output() {
+		$result = new GenerativeAiResult(
+			'test-result',
+			array( new Candidate( new ModelMessage( array( new MessagePart( 'Generated text' ) ) ), FinishReasonEnum::stop() ) ),
+			new TokenUsage( 100, 50, 150 ),
+			$this->create_test_provider_metadata(),
+			$this->create_test_text_model_metadata()
+		);
+
+		$metadata = $this->createMock( ModelMetadata::class );
+		$metadata->method( 'getId' )->willReturn( 'test-model' );
+
+		$model = $this->create_mock_text_generation_model( $result, $metadata );
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry, 'Generate multimodal' );
+		$builder->using_model( $model );
+		$builder->as_output_modalities( ModalityEnum::text(), ModalityEnum::image() );
+
+		$actual_result = $builder->generate_result();
+		$this->assertSame( $result, $actual_result );
+	}
+
+	/**
+	 * Tests generateResult returns WP_Error when model does not support modality.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_generate_result_returns_wp_error_for_unsupported_modality() {
+		$metadata = $this->createMock( ModelMetadata::class );
+		$metadata->method( 'getId' )->willReturn( 'test-model' );
+
+		$model = $this->createMock( ModelInterface::class );
+		$model->method( 'metadata' )->willReturn( $metadata );
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry, 'Test prompt' );
+		$builder->using_model( $model );
+
+		$result = $builder->generate_result();
+
+		$this->assertWPError( $result );
+		$this->assertSame( 'prompt_builder_error', $result->get_error_code() );
+		$this->assertStringContainsString( 'does not support text generation', $result->get_error_message() );
+	}
+
+	/**
+	 * Tests generateResult returns WP_Error for unsupported output modality.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_generate_result_returns_wp_error_for_unsupported_output_modality() {
+		$metadata = $this->createMock( ModelMetadata::class );
+		$metadata->method( 'getId' )->willReturn( 'test-model' );
+
+		$model = $this->createMock( ModelInterface::class );
+		$model->method( 'metadata' )->willReturn( $metadata );
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry, 'Test prompt' );
+		$builder->using_model( $model );
+		$builder->as_output_modalities( ModalityEnum::video() );
+
+		$result = $builder->generate_result();
+
+		$this->assertWPError( $result );
+		$this->assertSame( 'prompt_builder_error', $result->get_error_code() );
+		$this->assertStringContainsString( 'Output modality "video" is not yet supported', $result->get_error_message() );
+	}
+
+	/**
+	 * Tests generateTextResult method.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_generate_text_result() {
+		$result = new GenerativeAiResult(
+			'test-result',
+			array( new Candidate( new ModelMessage( array( new MessagePart( 'Generated text' ) ) ), FinishReasonEnum::stop() ) ),
+			new TokenUsage( 100, 50, 150 ),
+			$this->create_test_provider_metadata(),
+			$this->create_test_text_model_metadata()
+		);
+
+		$metadata = $this->createMock( ModelMetadata::class );
+		$metadata->method( 'getId' )->willReturn( 'test-model' );
+
+		$model = $this->create_mock_text_generation_model( $result, $metadata );
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry, 'Test prompt' );
+		$builder->using_model( $model );
+
+		$actual_result = $builder->generate_text_result();
+		$this->assertSame( $result, $actual_result );
+
+		/** @var ModelConfig $config */
+		$config = $this->get_wrapped_prompt_builder_property_value( $builder, 'modelConfig' );
+
+		$modalities = $config->getOutputModalities();
+		$this->assertNotNull( $modalities );
+		$this->assertTrue( $modalities[0]->isText() );
+	}
+
+	/**
+	 * Tests generateImageResult method.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_generate_image_result() {
+		$result = new GenerativeAiResult(
+			'test-result',
+			array(
+				new Candidate(
+					new ModelMessage( array( new MessagePart( new File( 'data:image/png;base64,iVBORw0KGgo=', 'image/png' ) ) ) ),
+					FinishReasonEnum::stop()
+				),
+			),
+			new TokenUsage( 100, 50, 150 ),
+			$this->create_test_provider_metadata(),
+			$this->create_test_text_model_metadata()
+		);
+
+		$metadata = $this->createMock( ModelMetadata::class );
+		$metadata->method( 'getId' )->willReturn( 'test-model' );
+
+		$model = $this->create_mock_image_generation_model( $result, $metadata );
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry, 'Generate image' );
+		$builder->using_model( $model );
+
+		$actual_result = $builder->generate_image_result();
+		$this->assertSame( $result, $actual_result );
+
+		/** @var ModelConfig $config */
+		$config = $this->get_wrapped_prompt_builder_property_value( $builder, 'modelConfig' );
+
+		$modalities = $config->getOutputModalities();
+		$this->assertNotNull( $modalities );
+		$this->assertTrue( $modalities[0]->isImage() );
+	}
+
+	/**
+	 * Tests generateText returns WP_Error when no candidates.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_generate_text_returns_wp_error_when_no_candidates() {
+		$metadata = $this->createMock( ModelMetadata::class );
+		$metadata->method( 'getId' )->willReturn( 'test-model' );
+
+		$model = $this->create_mock_text_generation_model_with_exception(
+			new RuntimeException( 'No candidates were generated' ),
+			$metadata
+		);
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry, 'Generate text' );
+		$builder->using_model( $model );
+
+		$result = $builder->generate_text();
+
+		$this->assertWPError( $result );
+		$this->assertSame( 'prompt_builder_error', $result->get_error_code() );
+		$this->assertStringContainsString( 'No candidates were generated', $result->get_error_message() );
+	}
+
+	/**
+	 * Tests generateText returns WP_Error when message has no parts.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_generate_text_returns_wp_error_when_no_parts() {
+		$message   = new ModelMessage( array() );
+		$candidate = new Candidate( $message, FinishReasonEnum::stop() );
+
+		$result = new GenerativeAiResult(
+			'test-result',
+			array( $candidate ),
+			new TokenUsage( 100, 50, 150 ),
+			$this->create_test_provider_metadata(),
+			$this->create_test_text_model_metadata()
+		);
+
+		$metadata = $this->createMock( ModelMetadata::class );
+		$metadata->method( 'getId' )->willReturn( 'test-model' );
+
+		$model = $this->create_mock_text_generation_model( $result, $metadata );
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry, 'Generate text' );
+		$builder->using_model( $model );
+
+		$actual_result = $builder->generate_text();
+
+		$this->assertWPError( $actual_result );
+		$this->assertSame( 'prompt_builder_error', $actual_result->get_error_code() );
+		$this->assertStringContainsString( 'No text content found in first candidate', $actual_result->get_error_message() );
+	}
+
+	/**
+	 * Tests generateText returns WP_Error when part has no text.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_generate_text_returns_wp_error_when_part_has_no_text() {
+		$file         = new File( 'https://example.com/image.jpg', 'image/jpeg' );
+		$message_part = new MessagePart( $file );
+		$message      = new ModelMessage( array( $message_part ) );
+		$candidate    = new Candidate( $message, FinishReasonEnum::stop() );
+
+		$result = new GenerativeAiResult(
+			'test-result',
+			array( $candidate ),
+			new TokenUsage( 100, 50, 150 ),
+			$this->create_test_provider_metadata(),
+			$this->create_test_text_model_metadata()
+		);
+
+		$metadata = $this->createMock( ModelMetadata::class );
+		$metadata->method( 'getId' )->willReturn( 'test-model' );
+
+		$model = $this->create_mock_text_generation_model( $result, $metadata );
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry, 'Generate text' );
+		$builder->using_model( $model );
+
+		$actual_result = $builder->generate_text();
+
+		$this->assertWPError( $actual_result );
+		$this->assertSame( 'prompt_builder_error', $actual_result->get_error_code() );
+		$this->assertStringContainsString( 'No text content found in first candidate', $actual_result->get_error_message() );
+	}
+
+	/**
+	 * Tests generateTexts method.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_generate_texts() {
+		$candidates = array(
+			new Candidate(
+				new ModelMessage( array( new MessagePart( 'Text 1' ) ) ),
+				FinishReasonEnum::stop()
+			),
+			new Candidate(
+				new ModelMessage( array( new MessagePart( 'Text 2' ) ) ),
+				FinishReasonEnum::stop()
+			),
+			new Candidate(
+				new ModelMessage( array( new MessagePart( 'Text 3' ) ) ),
+				FinishReasonEnum::stop()
+			),
+		);
+
+		$result = new GenerativeAiResult(
+			'test-result-id',
+			$candidates,
+			new TokenUsage( 100, 50, 150 ),
+			$this->create_test_provider_metadata(),
+			$this->create_test_text_model_metadata()
+		);
+
+		$metadata = $this->createMock( ModelMetadata::class );
+		$metadata->method( 'getId' )->willReturn( 'test-model' );
+
+		$model = $this->create_mock_text_generation_model( $result, $metadata );
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry, 'Generate texts' );
+		$builder->using_model( $model );
+
+		$texts = $builder->generate_texts( 3 );
+
+		$this->assertCount( 3, $texts );
+		$this->assertEquals( 'Text 1', $texts[0] );
+		$this->assertEquals( 'Text 2', $texts[1] );
+		$this->assertEquals( 'Text 3', $texts[2] );
+
+		/** @var ModelConfig $config */
+		$config = $this->get_wrapped_prompt_builder_property_value( $builder, 'modelConfig' );
+
+		$this->assertEquals( 3, $config->getCandidateCount() );
+	}
+
+	/**
+	 * Tests generateTexts returns WP_Error when no text generated.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_generate_texts_returns_wp_error_when_no_text_generated() {
+		$metadata = $this->createMock( ModelMetadata::class );
+		$metadata->method( 'getId' )->willReturn( 'test-model' );
+
+		$model = $this->create_mock_text_generation_model_with_exception(
+			new RuntimeException( 'No text was generated from any candidates' ),
+			$metadata
+		);
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry, 'Generate texts' );
+		$builder->using_model( $model );
+
+		$result = $builder->generate_texts();
+
+		$this->assertWPError( $result );
+		$this->assertSame( 'prompt_builder_error', $result->get_error_code() );
+		$this->assertStringContainsString( 'No text was generated from any candidates', $result->get_error_message() );
+	}
+
+	/**
+	 * Tests generateImage method.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_generate_image() {
+		$file         = new File( 'https://example.com/generated.jpg', 'image/jpeg' );
+		$message_part = new MessagePart( $file );
+		$message      = new ModelMessage( array( $message_part ) );
+		$candidate    = new Candidate( $message, FinishReasonEnum::stop() );
+
+		$result = new GenerativeAiResult(
+			'test-result',
+			array( $candidate ),
+			new TokenUsage( 100, 50, 150 ),
+			$this->create_test_provider_metadata(),
+			$this->create_test_text_model_metadata()
+		);
+
+		$metadata = $this->createMock( ModelMetadata::class );
+		$metadata->method( 'getId' )->willReturn( 'test-model' );
+
+		$model = $this->create_mock_image_generation_model( $result, $metadata );
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry, 'Generate image' );
+		$builder->using_model( $model );
+
+		$generated_file = $builder->generate_image();
+		$this->assertSame( $file, $generated_file );
+	}
+
+	/**
+	 * Tests generateImage returns WP_Error when no image file.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_generate_image_returns_wp_error_when_no_file() {
+		$message_part = new MessagePart( 'Text instead of image' );
+		$message      = new ModelMessage( array( $message_part ) );
+		$candidate    = new Candidate( $message, FinishReasonEnum::stop() );
+
+		$result = new GenerativeAiResult(
+			'test-result',
+			array( $candidate ),
+			new TokenUsage( 100, 50, 150 ),
+			$this->create_test_provider_metadata(),
+			$this->create_test_text_model_metadata()
+		);
+
+		$metadata = $this->createMock( ModelMetadata::class );
+		$metadata->method( 'getId' )->willReturn( 'test-model' );
+
+		$model = $this->create_mock_image_generation_model( $result, $metadata );
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry, 'Generate image' );
+		$builder->using_model( $model );
+
+		$actual_result = $builder->generate_image();
+
+		$this->assertWPError( $actual_result );
+		$this->assertSame( 'prompt_builder_error', $actual_result->get_error_code() );
+		$this->assertStringContainsString( 'No file content found in first candidate', $actual_result->get_error_message() );
+	}
+
+	/**
+	 * Tests generateImages method.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_generate_images() {
+		$files = array(
+			new File( 'https://example.com/img1.jpg', 'image/jpeg' ),
+			new File( 'https://example.com/img2.jpg', 'image/jpeg' ),
+		);
+
+		$candidates = array();
+		foreach ( $files as $file ) {
+			$candidates[] = new Candidate(
+				new Message( MessageRoleEnum::model(), array( new MessagePart( $file ) ) ),
+				FinishReasonEnum::stop()
+			);
+		}
+
+		$result = new GenerativeAiResult(
+			'test-result-id',
+			$candidates,
+			new TokenUsage( 100, 50, 150 ),
+			$this->create_test_provider_metadata(),
+			$this->create_test_text_model_metadata()
+		);
+
+		$metadata = $this->createMock( ModelMetadata::class );
+		$metadata->method( 'getId' )->willReturn( 'test-model' );
+
+		$model = $this->create_mock_image_generation_model( $result, $metadata );
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry, 'Generate images' );
+		$builder->using_model( $model );
+
+		$generated_files = $builder->generate_images( 2 );
+
+		$this->assertCount( 2, $generated_files );
+		$this->assertSame( $files[0], $generated_files[0] );
+		$this->assertSame( $files[1], $generated_files[1] );
+	}
+
+	/**
+	 * Tests convertTextToSpeech method.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_convert_text_to_speech() {
+		$file         = new File( 'https://example.com/audio.mp3', 'audio/mp3' );
+		$message_part = new MessagePart( $file );
+		$message      = new Message( MessageRoleEnum::model(), array( $message_part ) );
+		$candidate    = new Candidate( $message, FinishReasonEnum::stop() );
+
+		$result = new GenerativeAiResult(
+			'test-result',
+			array( $candidate ),
+			new TokenUsage( 100, 50, 150 ),
+			$this->create_test_provider_metadata(),
+			$this->create_test_text_model_metadata()
+		);
+
+		$metadata = $this->createMock( ModelMetadata::class );
+		$metadata->method( 'getId' )->willReturn( 'test-model' );
+
+		$model = $this->create_mock_text_to_speech_model( $result, $metadata );
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry, 'Convert this text' );
+		$builder->using_model( $model );
+
+		$audio_file = $builder->convert_text_to_speech();
+		$this->assertSame( $file, $audio_file );
+	}
+
+	/**
+	 * Tests convertTextToSpeeches method.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_convert_text_to_speeches() {
+		$files = array(
+			new File( 'https://example.com/audio1.mp3', 'audio/mp3' ),
+			new File( 'https://example.com/audio2.mp3', 'audio/mp3' ),
+		);
+
+		$candidates = array();
+		foreach ( $files as $file ) {
+			$candidates[] = new Candidate(
+				new Message( MessageRoleEnum::model(), array( new MessagePart( $file ) ) ),
+				FinishReasonEnum::stop()
+			);
+		}
+
+		$result = new GenerativeAiResult(
+			'test-result-id',
+			$candidates,
+			new TokenUsage( 100, 50, 150 ),
+			$this->create_test_provider_metadata(),
+			$this->create_test_text_model_metadata()
+		);
+
+		$metadata = $this->createMock( ModelMetadata::class );
+		$metadata->method( 'getId' )->willReturn( 'test-model' );
+
+		$model = $this->create_mock_text_to_speech_model( $result, $metadata );
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry, 'Convert this text' );
+		$builder->using_model( $model );
+
+		$audio_files = $builder->convert_text_to_speeches( 2 );
+
+		$this->assertCount( 2, $audio_files );
+		$this->assertSame( $files[0], $audio_files[0] );
+		$this->assertSame( $files[1], $audio_files[1] );
+	}
+
+	/**
+	 * Tests generateSpeech method.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_generate_speech() {
+		$file         = new File( 'https://example.com/speech.mp3', 'audio/mp3' );
+		$message_part = new MessagePart( $file );
+		$message      = new Message( MessageRoleEnum::model(), array( $message_part ) );
+		$candidate    = new Candidate( $message, FinishReasonEnum::stop() );
+
+		$result = new GenerativeAiResult(
+			'test-result',
+			array( $candidate ),
+			new TokenUsage( 100, 50, 150 ),
+			$this->create_test_provider_metadata(),
+			$this->create_test_text_model_metadata()
+		);
+
+		$metadata = $this->createMock( ModelMetadata::class );
+		$metadata->method( 'getId' )->willReturn( 'test-model' );
+
+		$model = $this->create_mock_speech_generation_model( $result, $metadata );
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry, 'Generate speech' );
+		$builder->using_model( $model );
+
+		$speech_file = $builder->generate_speech();
+		$this->assertSame( $file, $speech_file );
+	}
+
+	/**
+	 * Tests generateSpeeches method.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_generate_speeches() {
+		$files = array(
+			new File( 'https://example.com/speech1.mp3', 'audio/mp3' ),
+			new File( 'https://example.com/speech2.mp3', 'audio/mp3' ),
+			new File( 'https://example.com/speech3.mp3', 'audio/mp3' ),
+		);
+
+		$candidates = array();
+		foreach ( $files as $file ) {
+			$candidates[] = new Candidate(
+				new Message( MessageRoleEnum::model(), array( new MessagePart( $file ) ) ),
+				FinishReasonEnum::stop(),
+				10
+			);
+		}
+
+		$result = new GenerativeAiResult(
+			'test-result-id',
+			$candidates,
+			new TokenUsage( 100, 50, 150 ),
+			$this->create_test_provider_metadata(),
+			$this->create_test_text_model_metadata()
+		);
+
+		$metadata = $this->createMock( ModelMetadata::class );
+		$metadata->method( 'getId' )->willReturn( 'test-model' );
+
+		$model = $this->create_mock_speech_generation_model( $result, $metadata );
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry, 'Generate speech' );
+		$builder->using_model( $model );
+
+		$speech_files = $builder->generate_speeches( 3 );
+
+		$this->assertCount( 3, $speech_files );
+		$this->assertSame( $files[0], $speech_files[0] );
+		$this->assertSame( $files[1], $speech_files[1] );
+		$this->assertSame( $files[2], $speech_files[2] );
+	}
+
+	/**
+	 * Tests using_abilities with ability name string.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_using_ability_with_string() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$result  = $builder->using_abilities( 'wpaiclienttests/simple' );
+
+		$this->assertSame( $builder, $result );
+
+		$declarations = $this->get_function_declarations( $builder );
+
+		$this->assertNotNull( $declarations );
+		$this->assertCount( 1, $declarations );
+		$this->assertEquals( 'wpab__wpaiclienttests__simple', $declarations[0]->getName() );
+		$this->assertEquals( 'A simple test ability with no parameters.', $declarations[0]->getDescription() );
+	}
+
+	/**
+	 * Tests using_abilities with WP_Ability object.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_using_ability_with_wp_ability_object() {
+		$ability = wp_get_ability( 'wpaiclienttests/with-params' );
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$result  = $builder->using_abilities( $ability );
+
+		$this->assertSame( $builder, $result );
+
+		$declarations = $this->get_function_declarations( $builder );
+
+		$this->assertNotNull( $declarations );
+		$this->assertCount( 1, $declarations );
+		$this->assertEquals( 'wpab__wpaiclienttests__with-params', $declarations[0]->getName() );
+		$this->assertEquals( 'A test ability that accepts parameters.', $declarations[0]->getDescription() );
+
+		$params = $declarations[0]->getParameters();
+		$this->assertNotNull( $params );
+		$this->assertArrayHasKey( 'properties', $params );
+		$this->assertArrayHasKey( 'title', $params['properties'] );
+	}
+
+	/**
+	 * Tests using_abilities with multiple abilities.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_using_ability_with_multiple_abilities() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$result  = $builder->using_abilities(
+			'wpaiclienttests/simple',
+			'wpaiclienttests/with-params',
+			'wpaiclienttests/returns-error'
+		);
+
+		$this->assertSame( $builder, $result );
+
+		$declarations = $this->get_function_declarations( $builder );
+
+		$this->assertNotNull( $declarations );
+		$this->assertCount( 3, $declarations );
+		$this->assertEquals( 'wpab__wpaiclienttests__simple', $declarations[0]->getName() );
+		$this->assertEquals( 'wpab__wpaiclienttests__with-params', $declarations[1]->getName() );
+		$this->assertEquals( 'wpab__wpaiclienttests__returns-error', $declarations[2]->getName() );
+	}
+
+	/**
+	 * Tests using_abilities skips non-existent abilities.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_using_ability_skips_nonexistent_abilities() {
+		$this->setExpectedIncorrectUsage( 'WP_Abilities_Registry::get_registered' );
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$result  = $builder->using_abilities(
+			'wpaiclienttests/simple',
+			'nonexistent/ability',
+			'wpaiclienttests/with-params'
+		);
+
+		$this->assertSame( $builder, $result );
+
+		$declarations = $this->get_function_declarations( $builder );
+
+		$this->assertNotNull( $declarations );
+		$this->assertCount( 2, $declarations );
+		$this->assertEquals( 'wpab__wpaiclienttests__simple', $declarations[0]->getName() );
+		$this->assertEquals( 'wpab__wpaiclienttests__with-params', $declarations[1]->getName() );
+	}
+
+	/**
+	 * Tests using_abilities with empty arguments returns self.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_using_ability_with_no_arguments_returns_self() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$result  = $builder->using_abilities();
+
+		$this->assertSame( $builder, $result );
+
+		$declarations = $this->get_function_declarations( $builder );
+
+		$this->assertNull( $declarations );
+	}
+
+	/**
+	 * Tests using_abilities with mixed strings and WP_Ability objects.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_using_ability_with_mixed_types() {
+		$ability = wp_get_ability( 'wpaiclienttests/with-params' );
+
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$result  = $builder->using_abilities(
+			'wpaiclienttests/simple',
+			$ability
+		);
+
+		$this->assertSame( $builder, $result );
+
+		$declarations = $this->get_function_declarations( $builder );
+
+		$this->assertNotNull( $declarations );
+		$this->assertCount( 2, $declarations );
+		$this->assertEquals( 'wpab__wpaiclienttests__simple', $declarations[0]->getName() );
+		$this->assertEquals( 'wpab__wpaiclienttests__with-params', $declarations[1]->getName() );
+	}
+
+	/**
+	 * Tests using_abilities with hyphenated ability name.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_using_ability_with_hyphenated_name() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$result  = $builder->using_abilities( 'wpaiclienttests/hyphen-test' );
+
+		$this->assertSame( $builder, $result );
+
+		$declarations = $this->get_function_declarations( $builder );
+
+		$this->assertNotNull( $declarations );
+		$this->assertCount( 1, $declarations );
+		$this->assertEquals( 'wpab__wpaiclienttests__hyphen-test', $declarations[0]->getName() );
+	}
+
+	/**
+	 * Tests using_abilities can be chained with other methods.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_using_ability_method_chaining() {
+		$builder = new WP_AI_Client_Prompt_Builder( $this->registry );
+		$result  = $builder
+			->with_text( 'Test prompt' )
+			->using_abilities( 'wpaiclienttests/simple' )
+			->using_system_instruction( 'You are a helpful assistant' )
+			->using_max_tokens( 500 );
+
+		$this->assertSame( $builder, $result );
+
+		$declarations = $this->get_function_declarations( $builder );
+
+		$this->assertNotNull( $declarations );
+		$this->assertCount( 1, $declarations );
+		$this->assertEquals( 'wpab__wpaiclienttests__simple', $declarations[0]->getName() );
+
+		/** @var ModelConfig $config */
+		$config = $this->get_wrapped_prompt_builder_property_value( $builder, 'modelConfig' );
+
+		$this->assertEquals( 'You are a helpful assistant', $config->getSystemInstruction() );
+		$this->assertEquals( 500, $config->getMaxTokens() );
+	}
+
+	/**
+	 * Tests that is_supported returns false when prevent prompt filter returns true.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_is_supported_returns_false_when_filter_prevents_prompt() {
+		add_filter( 'wp_ai_client_prevent_prompt', '__return_true' );
+
+		$builder = new WP_AI_Client_Prompt_Builder( AiClient::defaultRegistry(), 'Test prompt' );
+
+		$this->assertFalse( $builder->is_supported() );
+	}
+
+	/**
+	 * Tests that generate_result returns WP_Error when prevent prompt filter returns true.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_generate_result_returns_wp_error_when_filter_prevents_prompt() {
+		add_filter( 'wp_ai_client_prevent_prompt', '__return_true' );
+
+		$builder = new WP_AI_Client_Prompt_Builder( AiClient::defaultRegistry(), 'Test prompt' );
+
+		$result = $builder->generate_result();
+
+		$this->assertWPError( $result );
+		$this->assertSame( 'prompt_prevented', $result->get_error_code() );
+		$this->assertSame( 'Prompt execution was prevented by a filter.', $result->get_error_message() );
+	}
+
+	/**
+	 * Tests that prevent prompt filter receives a clone of the builder instance.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_prevent_prompt_filter_receives_cloned_builder_instance() {
+		$captured_builder = null;
+
+		add_filter(
+			'wp_ai_client_prevent_prompt',
+			static function ( $prevent, $builder ) use ( &$captured_builder ) {
+				$captured_builder = $builder;
+				return $prevent;
+			},
+			10,
+			2
+		);
+
+		$builder = new WP_AI_Client_Prompt_Builder( AiClient::defaultRegistry(), 'Test prompt' );
+
+		// Test with is_supported().
+		$builder->is_supported();
+		$this->assertNotSame( $builder, $captured_builder, 'Filter should receive a clone, not the same instance' );
+		$this->assertInstanceOf( WP_AI_Client_Prompt_Builder::class, $captured_builder );
+
+		// Reset and test with generate_result().
+		$captured_builder = null;
+		$builder2         = new WP_AI_Client_Prompt_Builder( AiClient::defaultRegistry(), 'Test prompt' );
+		$builder2->generate_result();
+		$this->assertNotSame( $builder2, $captured_builder, 'Filter should receive a clone, not the same instance' );
+		$this->assertInstanceOf( WP_AI_Client_Prompt_Builder::class, $captured_builder );
+	}
+
+	/**
+	 * Tests that once in error state, subsequent fluent calls return the same instance.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_error_state_fluent_calls_return_same_instance() {
+		$registry       = AiClient::defaultRegistry();
+		$prompt_builder = new WP_AI_Client_Prompt_Builder( $registry );
+
+		// Trigger an error state by calling a nonexistent method.
+		$prompt_builder->nonexistent_method();
+
+		$result = $prompt_builder->with_text( 'Test' );
+		$this->assertSame( $prompt_builder, $result, 'Fluent method should return same instance when in error state' );
+
+		$result = $prompt_builder->using_max_tokens( 100 );
+		$this->assertSame( $prompt_builder, $result, 'Fluent method should return same instance when in error state' );
+	}
+
+	/**
+	 * Tests that support check methods return false when in error state.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_support_check_methods_return_false_in_error_state() {
+		$registry       = AiClient::defaultRegistry();
+		$prompt_builder = new WP_AI_Client_Prompt_Builder( $registry );
+
+		// Trigger an error state by calling a nonexistent method.
+		$prompt_builder->nonexistent_method();
+
+		$this->assertFalse( $prompt_builder->is_supported(), 'is_supported should return false when in error state' );
+		$this->assertFalse( $prompt_builder->is_supported_for_text_generation(), 'is_supported_for_text_generation should return false when in error state' );
+	}
+
+	/**
+	 * Tests that generating methods return WP_Error when in error state.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_generating_methods_return_wp_error_in_error_state() {
+		$registry       = AiClient::defaultRegistry();
+		$prompt_builder = new WP_AI_Client_Prompt_Builder( $registry );
+
+		// Trigger an error state by calling a nonexistent method.
+		$prompt_builder->nonexistent_method();
+
+		$result = $prompt_builder->generate_text();
+		$this->assertWPError( $result, 'generate_text should return WP_Error when in error state' );
+		$this->assertSame( 'prompt_builder_error', $result->get_error_code() );
+	}
+
+	/**
+	 * Tests that exception in terminating method is caught and returned as WP_Error.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_exception_in_terminating_method_caught_and_returned() {
+		$registry       = AiClient::defaultRegistry();
+		$prompt_builder = new WP_AI_Client_Prompt_Builder( $registry );
+
+		$error = $prompt_builder->generate_text();
+
+		$this->assertWPError( $error, 'generate_text should return WP_Error when exception occurs' );
+		$this->assertSame( 'prompt_builder_error', $error->get_error_code() );
+
+		$error_data = $error->get_error_data();
+		$this->assertIsArray( $error_data );
+		$this->assertArrayHasKey( 'exception_class', $error_data );
+		$this->assertNotEmpty( $error_data['exception_class'] );
+	}
+
+	/**
+	 * Tests that exception in chained method is caught and returned by the terminating method as WP_Error.
+	 *
+	 * @ticket TBD
+	 */
+	public function test_exception_in_chained_method_caught_and_returned_by_terminating_method() {
+		$registry       = AiClient::defaultRegistry();
+		$prompt_builder = new WP_AI_Client_Prompt_Builder( $registry );
+
+		$result = $prompt_builder
+			->with_text( 'Start of prompt' )
+			->with_file( 'https://example.com/img.jpg', 'image/jpeg' )
+			// Invalid: Only provider and model ID must be given.
+			->using_model_preference( array( 'test-provider', 'test-model', 'test-version' ) )
+			->using_system_instruction( 'Be helpful' )
+			->generate_text();
+
+		$this->assertWPError( $result, 'generate_text should return WP_Error when exception occurs' );
+		$this->assertSame( 'prompt_builder_error', $result->get_error_code() );
+		$this->assertSame( 'Model preference tuple must contain model identifier and provider ID.', $result->get_error_message() );
+
+		$error_data = $result->get_error_data();
+		$this->assertIsArray( $error_data );
+		$this->assertArrayHasKey( 'exception_class', $error_data );
+		$this->assertNotEmpty( $error_data['exception_class'] );
+	}
+}
diff --git a/tools/php-ai-client/installer.sh b/tools/php-ai-client/installer.sh
new file mode 100755
index 0000000000000..6e128393406df
--- /dev/null
+++ b/tools/php-ai-client/installer.sh
@@ -0,0 +1,365 @@
+#!/usr/bin/env bash
+#
+# Installer script for bundling wordpress/php-ai-client into WordPress Core.
+#
+# Fetches the package, scopes Http\* dependencies via PHP-Scoper, generates
+# a manual autoloader, and places everything into src/wp-includes/php-ai-client/.
+#
+# Usage:
+#   bash tools/php-ai-client/installer.sh --branch=refactor/removes-providers
+#   bash tools/php-ai-client/installer.sh --version=1.0.0
+#
+
+set -euo pipefail
+
+# ---------------------------------------------------------------------------
+# Configuration
+# ---------------------------------------------------------------------------
+
+SCOPER_VERSION="0.18.17"
+SCOPER_URL="https://github.com/humbug/php-scoper/releases/download/${SCOPER_VERSION}/php-scoper.phar"
+GITHUB_REPO="https://github.com/WordPress/php-ai-client.git"
+
+TARGET_DIR="src/wp-includes/php-ai-client"
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+
+# ---------------------------------------------------------------------------
+# Parse arguments
+# ---------------------------------------------------------------------------
+
+VERSION=""
+BRANCH=""
+
+for arg in "$@"; do
+	case "$arg" in
+		--version=*)
+			VERSION="${arg#--version=}"
+			;;
+		--branch=*)
+			BRANCH="${arg#--branch=}"
+			;;
+		--help|-h)
+			echo "Usage: $0 [--version=X.Y.Z | --branch=BRANCH]"
+			echo ""
+			echo "Options:"
+			echo "  --version=X.Y.Z   Fetch a specific release version"
+			echo "  --branch=BRANCH   Fetch from a branch (e.g. refactor/removes-providers)"
+			echo ""
+			echo "Must be run from the WordPress development repository root."
+			exit 0
+			;;
+		*)
+			echo "Error: Unknown argument: $arg"
+			echo "Run '$0 --help' for usage."
+			exit 1
+			;;
+	esac
+done
+
+if [ -n "$VERSION" ] && [ -n "$BRANCH" ]; then
+	echo "Error: Cannot specify both --version and --branch."
+	exit 1
+fi
+
+if [ -z "$VERSION" ] && [ -z "$BRANCH" ]; then
+	echo "Error: Must specify either --version=X.Y.Z or --branch=BRANCH."
+	exit 1
+fi
+
+# ---------------------------------------------------------------------------
+# Prerequisites
+# ---------------------------------------------------------------------------
+
+check_command() {
+	if ! command -v "$1" &> /dev/null; then
+		echo "Error: '$1' is required but not found in PATH."
+		exit 1
+	fi
+}
+
+check_command php
+check_command composer
+check_command git
+
+# Verify we're running from the repo root.
+if [ ! -f "wp-cli.yml" ] && [ ! -f "wp-config-sample.php" ] && [ ! -d "src/wp-includes" ]; then
+	echo "Error: This script must be run from the WordPress development repository root."
+	exit 1
+fi
+
+echo "==> Starting php-ai-client installer..."
+
+# ---------------------------------------------------------------------------
+# Temp directory (cleaned on exit)
+# ---------------------------------------------------------------------------
+
+TEMP_DIR="$(mktemp -d)"
+trap 'rm -rf "$TEMP_DIR"' EXIT
+
+echo "==> Using temp directory: $TEMP_DIR"
+
+# ---------------------------------------------------------------------------
+# Fetch package
+# ---------------------------------------------------------------------------
+
+if [ -n "$BRANCH" ]; then
+	echo "==> Cloning branch '$BRANCH' from $GITHUB_REPO..."
+	git clone --depth 1 --branch "$BRANCH" "$GITHUB_REPO" "$TEMP_DIR/package"
+	echo "==> Installing Composer dependencies..."
+	composer install --no-dev --no-interaction --working-dir="$TEMP_DIR/package"
+	VENDOR_DIR="$TEMP_DIR/package/vendor"
+	CLIENT_SRC="$TEMP_DIR/package/src"
+else
+	echo "==> Fetching version '$VERSION' via Composer..."
+	mkdir -p "$TEMP_DIR/package"
+	composer init --no-interaction --name="temp/installer" --working-dir="$TEMP_DIR/package"
+	composer require "wordpress/php-ai-client:${VERSION}" --no-dev --no-interaction --working-dir="$TEMP_DIR/package"
+	VENDOR_DIR="$TEMP_DIR/package/vendor"
+	CLIENT_SRC="$VENDOR_DIR/wordpress/php-ai-client/src"
+fi
+
+if [ ! -d "$VENDOR_DIR" ]; then
+	echo "Error: vendor directory not found at $VENDOR_DIR"
+	exit 1
+fi
+
+echo "==> Package fetched successfully."
+
+# ---------------------------------------------------------------------------
+# Clean target directory
+# ---------------------------------------------------------------------------
+
+if [ -d "$TARGET_DIR" ]; then
+	echo "==> Removing existing $TARGET_DIR..."
+	rm -rf "$TARGET_DIR"
+fi
+
+# ---------------------------------------------------------------------------
+# Scope dependencies with PHP-Scoper
+# ---------------------------------------------------------------------------
+
+SCOPER_PHAR="$TEMP_DIR/php-scoper.phar"
+
+echo "==> Downloading PHP-Scoper ${SCOPER_VERSION}..."
+curl -fsSL "$SCOPER_URL" -o "$SCOPER_PHAR"
+chmod +x "$SCOPER_PHAR"
+
+# Copy scoper config into temp dir.
+cp "$SCRIPT_DIR/scoper.inc.php" "$TEMP_DIR/scoper.inc.php"
+
+SCOPED_DIR="$TEMP_DIR/scoped"
+
+echo "==> Running PHP-Scoper..."
+php "$SCOPER_PHAR" add-prefix \
+	--working-dir="$TEMP_DIR/package" \
+	--config="$TEMP_DIR/scoper.inc.php" \
+	--output-dir="$SCOPED_DIR" \
+	--force \
+	--no-interaction
+
+echo "==> Scoping complete."
+
+# ---------------------------------------------------------------------------
+# Reorganize scoped output into namespace-based layout
+# ---------------------------------------------------------------------------
+
+THIRD_PARTY_DIR="$TEMP_DIR/third-party"
+
+echo "==> Reorganizing dependencies..."
+php "$SCRIPT_DIR/reorganize.php" \
+	"$VENDOR_DIR/composer/installed.json" \
+	"$SCOPED_DIR/vendor" \
+	"$THIRD_PARTY_DIR"
+
+echo "==> Reorganization complete."
+
+# ---------------------------------------------------------------------------
+# Copy files to target
+# ---------------------------------------------------------------------------
+
+echo "==> Copying files to $TARGET_DIR..."
+
+mkdir -p "$TARGET_DIR/src"
+mkdir -p "$TARGET_DIR/third-party"
+
+# Copy scoped AI client source.
+# If installed via branch, scoped source is at scoped/src/.
+# If installed via version, scoped source is at scoped/vendor/wordpress/php-ai-client/src/.
+if [ -n "$BRANCH" ]; then
+	cp -R "$SCOPED_DIR/src/." "$TARGET_DIR/src/"
+else
+	cp -R "$SCOPED_DIR/vendor/wordpress/php-ai-client/src/." "$TARGET_DIR/src/"
+fi
+
+# Copy reorganized third-party dependencies.
+cp -R "$THIRD_PARTY_DIR/." "$TARGET_DIR/third-party/"
+
+# Third-party paths to remove (not needed at runtime).
+REMOVE_PATHS=(
+	# Composer plugin (build-time only).
+	"Http/Discovery/Composer"
+
+	# HTTPlug client library (SDK uses PSR-18 directly).
+	"Http/Client"
+
+	# Promise/async support (SDK is synchronous).
+	"Http/Promise"
+
+	# Deprecated discovery classes superseded by Psr18ClientDiscovery / Psr17FactoryDiscovery.
+	"Http/Discovery/HttpClientDiscovery.php"
+	"Http/Discovery/HttpAsyncClientDiscovery.php"
+	"Http/Discovery/MessageFactoryDiscovery.php"
+	"Http/Discovery/UriFactoryDiscovery.php"
+	"Http/Discovery/StreamFactoryDiscovery.php"
+	"Http/Discovery/NotFoundException.php"
+
+	# Convenience wrappers not used by the SDK.
+	"Http/Discovery/Psr17Factory.php"
+	"Http/Discovery/Psr18Client.php"
+
+	# Mock strategy (not in default strategy list).
+	"Http/Discovery/Strategy/MockClientStrategy.php"
+
+	# Server-side PSR-7 interfaces (SDK is client-side only).
+	"Psr/Http/Message/ServerRequestInterface.php"
+	"Psr/Http/Message/ServerRequestFactoryInterface.php"
+	"Psr/Http/Message/UploadedFileInterface.php"
+	"Psr/Http/Message/UploadedFileFactoryInterface.php"
+
+	# PSR-14 interfaces not used by the event dispatcher.
+	"Psr/EventDispatcher/ListenerProviderInterface.php"
+	"Psr/EventDispatcher/StoppableEventInterface.php"
+
+	# PSR-16 cache exception interfaces (never thrown or caught).
+	"Psr/SimpleCache/CacheException.php"
+	"Psr/SimpleCache/InvalidArgumentException.php"
+)
+
+for path in "${REMOVE_PATHS[@]}"; do
+	rm -rf "$TARGET_DIR/third-party/$path"
+done
+
+# ---------------------------------------------------------------------------
+# Generate autoload.php
+# ---------------------------------------------------------------------------
+
+echo "==> Generating autoload.php..."
+
+cat > "$TARGET_DIR/autoload.php" << 'AUTOLOAD_PHP'
+<?php
+/**
+ * Autoloader for the bundled PHP AI Client library.
+ *
+ * This file is generated by tools/php-ai-client/installer.sh.
+ * Do not edit directly.
+ *
+ * @package WordPress
+ * @subpackage AI
+ * @since 7.0.0
+ */
+
+// Load polyfills (each function is guarded by function_exists).
+require_once __DIR__ . '/src/polyfills.php';
+
+spl_autoload_register(
+	static function ( $class_name ) {
+		// Namespace prefix for the AI client.
+		$client_prefix     = 'WordPress\\AiClient\\';
+		$client_prefix_len = 19; // strlen( 'WordPress\\AiClient\\' )
+
+		// Namespace prefix for scoped dependencies (includes Psr\*, Http\*, etc.).
+		$scoped_prefix     = 'WordPress\\AiClientDependencies\\';
+		$scoped_prefix_len = 31; // strlen( 'WordPress\\AiClientDependencies\\' )
+
+		$base_dir = __DIR__;
+
+		// 1. WordPress\AiClient\* → src/
+		if ( 0 === strncmp( $class_name, $client_prefix, $client_prefix_len ) ) {
+			$relative_class = substr( $class_name, $client_prefix_len );
+			$file           = $base_dir . '/src/' . str_replace( '\\', '/', $relative_class ) . '.php';
+			if ( file_exists( $file ) ) {
+				require $file;
+			}
+			return;
+		}
+
+		// 2. WordPress\AiClientDependencies\* → third-party/ (strip prefix).
+		if ( 0 === strncmp( $class_name, $scoped_prefix, $scoped_prefix_len ) ) {
+			$relative_class = substr( $class_name, $scoped_prefix_len );
+			$file           = $base_dir . '/third-party/' . str_replace( '\\', '/', $relative_class ) . '.php';
+			if ( file_exists( $file ) ) {
+				require $file;
+			}
+			return;
+		}
+	}
+);
+AUTOLOAD_PHP
+
+echo "==> autoload.php generated."
+
+# ---------------------------------------------------------------------------
+# Validate output
+# ---------------------------------------------------------------------------
+
+echo "==> Validating output..."
+
+ERRORS=0
+
+# Check key directories exist.
+for dir in "$TARGET_DIR/src" "$TARGET_DIR/third-party"; do
+	if [ ! -d "$dir" ]; then
+		echo "Error: Expected directory not found: $dir"
+		ERRORS=$((ERRORS + 1))
+	fi
+done
+
+# Check autoloader exists and has valid syntax.
+if [ ! -f "$TARGET_DIR/autoload.php" ]; then
+	echo "Error: autoload.php not found."
+	ERRORS=$((ERRORS + 1))
+else
+	if ! php -l "$TARGET_DIR/autoload.php" > /dev/null 2>&1; then
+		echo "Error: autoload.php has syntax errors."
+		php -l "$TARGET_DIR/autoload.php"
+		ERRORS=$((ERRORS + 1))
+	fi
+fi
+
+# Check that AiClient.php exists in source.
+if [ ! -f "$TARGET_DIR/src/AiClient.php" ]; then
+	echo "Warning: src/AiClient.php not found. The package structure may differ."
+fi
+
+# Check that Http dependencies are scoped.
+if [ -d "$TARGET_DIR/third-party/Http" ]; then
+	SCOPED_COUNT=$(grep -rl "namespace WordPress\\\\AiClientDependencies\\\\Http" "$TARGET_DIR/third-party/Http/" 2>/dev/null | wc -l | tr -d ' ')
+	if [ "$SCOPED_COUNT" -eq 0 ]; then
+		echo "Warning: No scoped Http\\* namespaces found in third-party/Http/."
+	else
+		echo "    Found $SCOPED_COUNT scoped Http\\* files."
+	fi
+fi
+
+# Check that Psr interfaces are scoped.
+if [ -d "$TARGET_DIR/third-party/Psr" ]; then
+	SCOPED_PSR=$(grep -rl "namespace WordPress\\\\AiClientDependencies\\\\Psr" "$TARGET_DIR/third-party/Psr/" 2>/dev/null | wc -l | tr -d ' ')
+	if [ "$SCOPED_PSR" -eq 0 ]; then
+		echo "Warning: No scoped Psr\\* namespaces found in third-party/Psr/."
+	else
+		echo "    Found $SCOPED_PSR scoped Psr\\* files."
+	fi
+fi
+
+if [ "$ERRORS" -gt 0 ]; then
+	echo "Error: Validation failed with $ERRORS error(s)."
+	exit 1
+fi
+
+echo "==> Validation passed."
+echo "==> php-ai-client bundled successfully at $TARGET_DIR"
+echo ""
+echo "Next steps:"
+echo "  1. Verify: ls -R $TARGET_DIR"
+echo "  2. Test:   php -r \"require '$TARGET_DIR/autoload.php'; var_dump(class_exists('WordPress\\\\AiClient\\\\AiClient'));\""
+echo "  3. Lint:   composer lint:errors"
diff --git a/tools/php-ai-client/reorganize.php b/tools/php-ai-client/reorganize.php
new file mode 100644
index 0000000000000..026a95670a1c3
--- /dev/null
+++ b/tools/php-ai-client/reorganize.php
@@ -0,0 +1,176 @@
+<?php
+/**
+ * Dependency reorganizer for php-ai-client bundling.
+ *
+ * Reads vendor/composer/installed.json, maps PSR-4 namespace prefixes to
+ * directory paths, and copies scoped dependency files into a namespace-based
+ * layout under third-party/.
+ *
+ * Usage:
+ *   php reorganize.php <installed.json> <scoped-vendor-dir> <output-dir>
+ *
+ * @package WordPress
+ */
+
+if ( $argc < 4 ) {
+	fwrite( STDERR, "Usage: php reorganize.php <installed.json> <scoped-vendor-dir> <output-dir>\n" );
+	exit( 1 );
+}
+
+$installed_json_path = $argv[1];
+$scoped_vendor_dir   = rtrim( $argv[2], '/' );
+$output_dir          = rtrim( $argv[3], '/' );
+
+if ( ! file_exists( $installed_json_path ) ) {
+	fwrite( STDERR, "Error: installed.json not found at: $installed_json_path\n" );
+	exit( 1 );
+}
+
+if ( ! is_dir( $scoped_vendor_dir ) ) {
+	fwrite( STDERR, "Error: Scoped vendor directory not found at: $scoped_vendor_dir\n" );
+	exit( 1 );
+}
+
+// ---------------------------------------------------------------------------
+// Parse installed.json (handles Composer v1 and v2 formats).
+// ---------------------------------------------------------------------------
+
+$installed_data = json_decode( file_get_contents( $installed_json_path ), true );
+
+if ( null === $installed_data ) {
+	fwrite( STDERR, "Error: Failed to parse installed.json.\n" );
+	exit( 1 );
+}
+
+// Composer v2 wraps packages in a "packages" key; v1 is a flat array.
+if ( isset( $installed_data['packages'] ) && is_array( $installed_data['packages'] ) ) {
+	$packages = $installed_data['packages'];
+} elseif ( isset( $installed_data[0] ) ) {
+	$packages = $installed_data;
+} else {
+	fwrite( STDERR, "Error: Unrecognized installed.json format.\n" );
+	exit( 1 );
+}
+
+// ---------------------------------------------------------------------------
+// Process each dependency package.
+// ---------------------------------------------------------------------------
+
+$files_autoload = array();
+
+foreach ( $packages as $package ) {
+	$name = $package['name'] ?? '';
+
+	// Skip the AI client package itself.
+	if ( 'wordpress/php-ai-client' === $name ) {
+		continue;
+	}
+
+	// Get PSR-4 autoload mappings.
+	$psr4 = $package['autoload']['psr-4'] ?? array();
+
+	if ( empty( $psr4 ) ) {
+		// Check for PSR-0 as fallback.
+		$psr0 = $package['autoload']['psr-0'] ?? array();
+		if ( ! empty( $psr0 ) ) {
+			fwrite( STDERR, "Warning: Package '$name' uses PSR-0 autoloading (not fully supported). Skipping.\n" );
+		}
+		// Still check for files autoload below.
+	}
+
+	// Collect "files" autoload entries for future use.
+	$files = $package['autoload']['files'] ?? array();
+	if ( ! empty( $files ) ) {
+		foreach ( $files as $file ) {
+			$files_autoload[] = array(
+				'package' => $name,
+				'file'    => $file,
+			);
+		}
+	}
+
+	// Process PSR-4 mappings.
+	foreach ( $psr4 as $namespace_prefix => $source_dirs ) {
+		// Normalize source_dirs to array.
+		if ( ! is_array( $source_dirs ) ) {
+			$source_dirs = array( $source_dirs );
+		}
+
+		// Convert namespace prefix to directory path.
+		// e.g., "Http\\Client\\" → "Http/Client"
+		$namespace_path = rtrim( str_replace( '\\', '/', $namespace_prefix ), '/' );
+
+		// Determine the source directory in the scoped vendor output.
+		// Composer packages are at vendor/{package-name}/{source-dir}/.
+		foreach ( $source_dirs as $source_dir ) {
+			$source_dir = rtrim( $source_dir, '/' );
+
+			// Build the source path in the scoped vendor directory.
+			$source_path = $scoped_vendor_dir . '/' . $name;
+			if ( '' !== $source_dir ) {
+				$source_path .= '/' . $source_dir;
+			}
+
+			if ( ! is_dir( $source_path ) ) {
+				fwrite( STDERR, "Warning: Source directory not found for '$name' at: $source_path\n" );
+				continue;
+			}
+
+			// Build the target path.
+			$target_path = $output_dir . '/' . $namespace_path;
+
+			// Create target directory.
+			if ( ! is_dir( $target_path ) ) {
+				mkdir( $target_path, 0755, true );
+			}
+
+			// Copy files recursively.
+			copy_directory( $source_path, $target_path );
+
+			echo "  Copied: $name ($namespace_prefix) → $namespace_path\n";
+		}
+	}
+}
+
+if ( ! empty( $files_autoload ) ) {
+	fwrite( STDERR, "\nNote: The following packages have 'files' autoload entries that may need manual handling:\n" );
+	foreach ( $files_autoload as $entry ) {
+		fwrite( STDERR, "  - {$entry['package']}: {$entry['file']}\n" );
+	}
+}
+
+echo "\nReorganization complete.\n";
+
+// ---------------------------------------------------------------------------
+// Helper functions.
+// ---------------------------------------------------------------------------
+
+/**
+ * Recursively copy a directory.
+ *
+ * @param string $source Source directory path.
+ * @param string $dest   Destination directory path.
+ */
+function copy_directory( string $source, string $dest ): void {
+	$iterator = new RecursiveIteratorIterator(
+		new RecursiveDirectoryIterator( $source, RecursiveDirectoryIterator::SKIP_DOTS ),
+		RecursiveIteratorIterator::SELF_FIRST
+	);
+
+	foreach ( $iterator as $item ) {
+		$target = $dest . '/' . $iterator->getSubPathname();
+
+		if ( $item->isDir() ) {
+			if ( ! is_dir( $target ) ) {
+				mkdir( $target, 0755, true );
+			}
+		} else {
+			// Ensure parent directory exists.
+			$parent = dirname( $target );
+			if ( ! is_dir( $parent ) ) {
+				mkdir( $parent, 0755, true );
+			}
+			copy( $item->getPathname(), $target );
+		}
+	}
+}
diff --git a/tools/php-ai-client/scoper.inc.php b/tools/php-ai-client/scoper.inc.php
new file mode 100644
index 0000000000000..f08a4ebaf4f41
--- /dev/null
+++ b/tools/php-ai-client/scoper.inc.php
@@ -0,0 +1,111 @@
+<?php
+/**
+ * PHP-Scoper configuration for bundling php-ai-client dependencies.
+ *
+ * Scopes all third-party namespaces (Http\*, Psr\*, etc.) to
+ * WordPress\AiClientDependencies\* to avoid conflicts with plugin-bundled versions.
+ *
+ * @package WordPress
+ */
+
+use Isolated\Symfony\Component\Finder\Finder;
+
+return array(
+	'prefix' => 'WordPress\\AiClientDependencies',
+
+	'finders' => array(
+		// Include all PHP files in vendor (dependencies) so their namespaces get scoped.
+		Finder::create()
+			->files()
+			->ignoreVCS( true )
+			->notName( '/LICENSE|.*\\.md|.*\\.dist|Makefile/' )
+			->exclude( array( 'composer', 'doc', 'test', 'test_old', 'tests', 'Tests', 'vendor-bin' ) )
+			->in( 'vendor' ),
+
+		// Include the AI client source files so `use` statements referencing
+		// scoped dependency namespaces get updated. The AI client's own namespace
+		// is excluded below, so its `namespace` declarations stay unchanged.
+		Finder::create()
+			->files()
+			->ignoreVCS( true )
+			->name( '*.php' )
+			->in( 'src' ),
+	),
+
+	'exclude-namespaces' => array(
+		// The AI client's own namespace must not be scoped.
+		'WordPress\\AiClient',
+	),
+
+	'exclude-files' => array(),
+
+	'exclude-constants' => array(
+		// Preserve WordPress-compatible constants.
+		'/^ABSPATH$/',
+		'/^WPINC$/',
+	),
+
+	'exclude-functions' => array(
+		// polyfills.php defines global functions guarded by function_exists().
+		'str_starts_with',
+		'str_ends_with',
+		'str_contains',
+		'array_is_list',
+	),
+
+	'patchers' => array(
+		/**
+		 * Fix php-http/discovery hardcoded class name strings.
+		 *
+		 * Discovery probes for external HTTP implementations using hardcoded FQCN strings.
+		 * These must NOT be prefixed because they reference packages outside our bundle
+		 * (e.g., GuzzleHttp\Client, Nyholm\Psr7\Factory\Psr17Factory).
+		 */
+		static function ( string $file_path, string $prefix, string $contents ): string {
+			// Only patch php-http/discovery files.
+			if ( false === strpos( $file_path, 'php-http/discovery' ) ) {
+				return $contents;
+			}
+
+			// External package namespaces that Discovery probes for.
+			// These must remain un-prefixed in hardcoded string references.
+			$external_namespaces = array(
+				'GuzzleHttp',
+				'Http\\Adapter',
+				'Http\\Client\\Curl',
+				'Http\\Client\\Socket',
+				'Http\\Client\\Buzz',
+				'Http\\Client\\React',
+				'Buzz',
+				'Nyholm',
+				'Laminas',
+				'Symfony\\Component\\HttpClient',
+				'Phalcon\\Http',
+				'Slim\\Psr7',
+				'Kriswallsmith',
+			);
+
+			foreach ( $external_namespaces as $ns ) {
+				$escaped_ns     = preg_quote( $ns, '/' );
+				$escaped_prefix = preg_quote( $prefix, '/' );
+
+				// Remove prefix from string literals containing these namespaces.
+				// Matches: 'WordPress\AiClientDependencies\GuzzleHttp\...' or "WordPress\AiClientDependencies\GuzzleHttp\..."
+				$contents = preg_replace(
+					'/([\'"])' . $escaped_prefix . '\\\\\\\\' . $escaped_ns . '/',
+					'$1' . $ns,
+					$contents
+				);
+
+				// Also handle double-backslash variants in string concatenation.
+				$contents = preg_replace(
+					'/([\'"])' . $escaped_prefix . '\\\\' . $escaped_ns . '/',
+					'$1' . $ns,
+					$contents
+				);
+			}
+
+			return $contents;
+		},
+	),
+);