ai

@mariozechner/pi-ai

Unified LLM API with automatic model discovery, provider configuration, token and cost tracking, and simple context persistence and hand-off to other models mid-session.

Note: This library only includes models that support tool calling (function calling), as this is essential for agentic workflows.

Table of Contents

• Supported Providers
• Installation
• Quick Start
• Tools
  • Defining Tools
  • Handling Tool Calls
  • Streaming Tool Calls with Partial JSON
  • Validating Tool Arguments
  • Complete Event Reference
• Image Input
• Thinking/Reasoning
  • Unified Interface
  • Provider-Specific Options
  • Streaming Thinking Content
• Stop Reasons
• Error Handling
  • Aborting Requests
  • Continuing After Abort
• APIs, Models, and Providers
  • Providers and Models
  • Querying Providers and Models
  • Custom Models
  • OpenAI Compatibility Settings
  • Type Safety
• Cross-Provider Handoffs
• Context Serialization
• Browser Usage
  • Environment Variables
  • Checking Environment Variables
• OAuth Providers
  • Vertex AI (ADC)
  • CLI Login
  • Programmatic OAuth
  • Login Flow Example
  • Using OAuth Tokens
  • Provider Notes
• License

Supported Providers

• OpenAI
• Azure OpenAI (Responses)
• OpenAI Codex (ChatGPT Plus/Pro subscription, requires OAuth, see below)
• Anthropic
• Google
• Vertex AI (Gemini via Vertex AI)
• Mistral
• Groq
• Cerebras
• xAI
• OpenRouter
• Vercel AI Gateway
• MiniMax
• GitHub Copilot (requires OAuth, see below)
• Google Gemini CLI (requires OAuth, see below)
• Antigravity (requires OAuth, see below)
• Amazon Bedrock
• Kimi For Coding (Moonshot AI, uses Anthropic-compatible API)
• Any OpenAI-compatible API: Ollama, vLLM, LM Studio, etc.

Installation

npm install @mariozechner/pi-ai

TypeBox exports are re-exported from @mariozechner/pi-ai: Type, Static, and TSchema.

Quick Start

import { Type, getModel, stream, complete, Context, Tool, StringEnum } from '@mariozechner/pi-ai';

// Fully typed with auto-complete support for both providers and models
const model = getModel('openai', 'gpt-4o-mini');

// Define tools with TypeBox schemas for type safety and validation
const tools: Tool[] = [{
  name: 'get_time',
  description: 'Get the current time',
  parameters: Type.Object({
    timezone: Type.Optional(Type.String({ description: 'Optional timezone (e.g., America/New_York)' }))
  })
}];

// Build a conversation context (easily serializable and transferable between models)
const context: Context = {
  systemPrompt: 'You are a helpful assistant.',
  messages: [{ role: 'user', content: 'What time is it?' }],
  tools
};

// Option 1: Streaming with all event types
const s = stream(model, context);

for await (const event of s) {
  switch (event.type) {
    case 'start':
      console.log(`Starting with ${event.partial.model}`);
      break;
    case 'text_start':
      console.log('\n[Text started]');
      break;
    case 'text_delta':
      process.stdout.write(event.delta);
      break;
    case 'text_end':
      console.log('\n[Text ended]');
      break;
    case 'thinking_start':
      console.log('[Model is thinking...]');
      break;
    case 'thinking_delta':
      process.stdout.write(event.delta);
      break;
    case 'thinking_end':
      console.log('[Thinking complete]');
      break;
    case 'toolcall_start':
      console.log(`\n[Tool call started: index ${event.contentIndex}]`);
      break;
    case 'toolcall_delta':
      // Partial tool arguments are being streamed
      const partialCall = event.partial.content[event.contentIndex];
      if (partialCall.type === 'toolCall') {
        console.log(`[Streaming args for ${partialCall.name}]`);
      }
      break;
    case 'toolcall_end':
      console.log(`\nTool called: ${event.toolCall.name}`);
      console.log(`Arguments: ${JSON.stringify(event.toolCall.arguments)}`);
      break;
    case 'done':
      console.log(`\nFinished: ${event.reason}`);
      break;
    case 'error':
      console.error(`Error: ${event.error}`);
      break;
  }
}

// Get the final message after streaming, add it to the context
const finalMessage = await s.result();
context.messages.push(finalMessage);

// Handle tool calls if any
const toolCalls = finalMessage.content.filter(b => b.type === 'toolCall');
for (const call of toolCalls) {
  // Execute the tool
  const result = call.name === 'get_time'
    ? new Date().toLocaleString('en-US', {
        timeZone: call.arguments.timezone || 'UTC',
        dateStyle: 'full',
        timeStyle: 'long'
      })
    : 'Unknown tool';

  // Add tool result to context (supports text and images)
  context.messages.push({
    role: 'toolResult',
    toolCallId: call.id,
    toolName: call.name,
    content: [{ type: 'text', text: result }],
    isError: false,
    timestamp: Date.now()
  });
}

// Continue if there were tool calls
if (toolCalls.length > 0) {
  const continuation = await complete(model, context);
  context.messages.push(continuation);
  console.log('After tool execution:', continuation.content);
}

console.log(`Total tokens: ${finalMessage.usage.input} in, ${finalMessage.usage.output} out`);
console.log(`Cost: $${finalMessage.usage.cost.total.toFixed(4)}`);

// Option 2: Get complete response without streaming
const response = await complete(model, context);

for (const block of response.content) {
  if (block.type === 'text') {
    console.log(block.text);
  } else if (block.type === 'toolCall') {
    console.log(`Tool: ${block.name}(${JSON.stringify(block.arguments)})`);
  }
}

Tools

Tools enable LLMs to interact with external systems. This library uses TypeBox schemas for type-safe tool definitions with automatic validation using AJV. TypeBox schemas can be serialized and deserialized as plain JSON, making them ideal for distributed systems.

Defining Tools

import { Type, Tool, StringEnum } from '@mariozechner/pi-ai';

// Define tool parameters with TypeBox
const weatherTool: Tool = {
  name: 'get_weather',
  description: 'Get current weather for a location',
  parameters: Type.Object({
    location: Type.String({ description: 'City name or coordinates' }),
    units: StringEnum(['celsius', 'fahrenheit'], { default: 'celsius' })
  })
};

// Note: For Google API compatibility, use StringEnum helper instead of Type.Enum
// Type.Enum generates anyOf/const patterns that Google doesn't support

const bookMeetingTool: Tool = {
  name: 'book_meeting',
  description: 'Schedule a meeting',
  parameters: Type.Object({
    title: Type.String({ minLength: 1 }),
    startTime: Type.String({ format: 'date-time' }),
    endTime: Type.String({ format: 'date-time' }),
    attendees: Type.Array(Type.String({ format: 'email' }), { minItems: 1 })
  })
};

Handling Tool Calls

Tool results use content blocks and can include both text and images:

import { readFileSync } from 'fs';

const context: Context = {
  messages: [{ role: 'user', content: 'What is the weather in London?' }],
  tools: [weatherTool]
};

const response = await complete(model, context);

// Check for tool calls in the response
for (const block of response.content) {
  if (block.type === 'toolCall') {
    // Execute your tool with the arguments
    // See "Validating Tool Arguments" section for validation
    const result = await executeWeatherApi(block.arguments);

    // Add tool result with text content
    context.messages.push({
      role: 'toolResult',
      toolCallId: block.id,
      toolName: block.name,
      content: [{ type: 'text', text: JSON.stringify(result) }],
      isError: false,
      timestamp: Date.now()
    });
  }
}

// Tool results can also include images (for vision-capable models)
const imageBuffer = readFileSync('chart.png');
context.messages.push({
  role: 'toolResult',
  toolCallId: 'tool_xyz',
  toolName: 'generate_chart',
  content: [
    { type: 'text', text: 'Generated chart showing temperature trends' },
    { type: 'image', data: imageBuffer.toString('base64'), mimeType: 'image/png' }
  ],
  isError: false,
  timestamp: Date.now()
});

Streaming Tool Calls with Partial JSON

During streaming, tool call arguments are progressively parsed as they arrive. This enables real-time UI updates before the complete arguments are available:

const s = stream(model, context);

for await (const event of s) {
  if (event.type === 'toolcall_delta') {
    const toolCall = event.partial.content[event.contentIndex];

    // toolCall.arguments contains partially parsed JSON during streaming
    // This allows for progressive UI updates
    if (toolCall.type === 'toolCall' && toolCall.arguments) {
      // BE DEFENSIVE: arguments may be incomplete
      // Example: Show file path being written even before content is complete
      if (toolCall.name === 'write_file' && toolCall.arguments.path) {
        console.log(`Writing to: ${toolCall.arguments.path}`);

        // Content might be partial or missing
        if (toolCall.arguments.content) {
          console.log(`Content preview: ${toolCall.arguments.content.substring(0, 100)}...`);
        }
      }
    }
  }

  if (event.type === 'toolcall_end') {
    // Here toolCall.arguments is complete (but not yet validated)
    const toolCall = event.toolCall;
    console.log(`Tool completed: ${toolCall.name}`, toolCall.arguments);
  }
}

Important notes about partial tool arguments:

• During toolcall_delta events, arguments contains the best-effort parse of partial JSON
• Fields may be missing or incomplete - always check for existence before use
• String values may be truncated mid-word
• Arrays may be incomplete
• Nested objects may be partially populated
• At minimum, arguments will be an empty object {}, never undefined
• The Google provider does not support function call streaming. Instead, you will receive a single toolcall_delta event with the full arguments.

Validating Tool Arguments

When using agentLoop, tool arguments are automatically validated against your TypeBox schemas before execution. If validation fails, the error is returned to the model as a tool result, allowing it to retry.

When implementing your own tool execution loop with stream() or complete(), use validateToolCall to validate arguments before passing them to your tools:

import { stream, validateToolCall, Tool } from '@mariozechner/pi-ai';

const tools: Tool[] = [weatherTool, calculatorTool];
const s = stream(model, { messages, tools });

for await (const event of s) {
  if (event.type === 'toolcall_end') {
    const toolCall = event.toolCall;

    try {
      // Validate arguments against the tool's schema (throws on invalid args)
      const validatedArgs = validateToolCall(tools, toolCall);
      const result = await executeMyTool(toolCall.name, validatedArgs);
      // ... add tool result to context
    } catch (error) {
      // Validation failed - return error as tool result so model can retry
      context.messages.push({
        role: 'toolResult',
        toolCallId: toolCall.id,
        toolName: toolCall.name,
        content: [{ type: 'text', text: error.message }],
        isError: true,
        timestamp: Date.now()
      });
    }
  }
}

Complete Event Reference

All streaming events emitted during assistant message generation:

Event Type	Description	Key Properties
start	Stream begins	partial: Initial assistant message structure
text_start	Text block starts	contentIndex: Position in content array
text_delta	Text chunk received	delta: New text, contentIndex: Position
text_end	Text block complete	content: Full text, contentIndex: Position
thinking_start	Thinking block starts	contentIndex: Position in content array
thinking_delta	Thinking chunk received	delta: New text, contentIndex: Position
thinking_end	Thinking block complete	content: Full thinking, contentIndex: Position
toolcall_start	Tool call begins	contentIndex: Position in content array
toolcall_delta	Tool arguments streaming	delta: JSON chunk, partial.content[contentIndex].arguments: Partial parsed args
toolcall_end	Tool call complete	toolCall: Complete validated tool call with id, name, arguments
done	Stream complete	reason: Stop reason ("stop", "length", "toolUse"), message: Final assistant message
error	Error occurred	reason: Error type ("error" or "aborted"), error: AssistantMessage with partial content

Image Input

Models with vision capabilities can process images. You can check if a model supports images via the input property. If you pass images to a non-vision model, they are silently ignored.

import { readFileSync } from 'fs';
import { getModel, complete } from '@mariozechner/pi-ai';

const model = getModel('openai', 'gpt-4o-mini');

// Check if model supports images
if (model.input.includes('image')) {
  console.log('Model supports vision');
}

const imageBuffer = readFileSync('image.png');
const base64Image = imageBuffer.toString('base64');

const response = await complete(model, {
  messages: [{
    role: 'user',
    content: [
      { type: 'text', text: 'What is in this image?' },
      { type: 'image', data: base64Image, mimeType: 'image/png' }
    ]
  }]
});

// Access the response
for (const block of response.content) {
  if (block.type === 'text') {
    console.log(block.text);
  }
}

Thinking/Reasoning

Many models support thinking/reasoning capabilities where they can show their internal thought process. You can check if a model supports reasoning via the reasoning property. If you pass reasoning options to a non-reasoning model, they are silently ignored.

Unified Interface (streamSimple/completeSimple)

import { getModel, streamSimple, completeSimple } from '@mariozechner/pi-ai';

// Many models across providers support thinking/reasoning
const model = getModel('anthropic', 'claude-sonnet-4-20250514');
// or getModel('openai', 'gpt-5-mini');
// or getModel('google', 'gemini-2.5-flash');
// or getModel('xai', 'grok-code-fast-1');
// or getModel('groq', 'openai/gpt-oss-20b');
// or getModel('cerebras', 'gpt-oss-120b');
// or getModel('openrouter', 'z-ai/glm-4.5v');

// Check if model supports reasoning
if (model.reasoning) {
  console.log('Model supports reasoning/thinking');
}

// Use the simplified reasoning option
const response = await completeSimple(model, {
  messages: [{ role: 'user', content: 'Solve: 2x + 5 = 13' }]
}, {
  reasoning: 'medium'  // 'minimal' | 'low' | 'medium' | 'high' | 'xhigh' (xhigh maps to high on non-OpenAI providers)
});

// Access thinking and text blocks
for (const block of response.content) {
  if (block.type === 'thinking') {
    console.log('Thinking:', block.thinking);
  } else if (block.type === 'text') {
    console.log('Response:', block.text);
  }
}

Provider-Specific Options (stream/complete)

For fine-grained control, use the provider-specific options:

import { getModel, complete } from '@mariozechner/pi-ai';

// OpenAI Reasoning (o1, o3, gpt-5)
const openaiModel = getModel('openai', 'gpt-5-mini');
await complete(openaiModel, context, {
  reasoningEffort: 'medium',
  reasoningSummary: 'detailed'  // OpenAI Responses API only
});

// Anthropic Thinking (Claude Sonnet 4)
const anthropicModel = getModel('anthropic', 'claude-sonnet-4-20250514');
await complete(anthropicModel, context, {
  thinkingEnabled: true,
  thinkingBudgetTokens: 8192  // Optional token limit
});

// Google Gemini Thinking
const googleModel = getModel('google', 'gemini-2.5-flash');
await complete(googleModel, context, {
  thinking: {
    enabled: true,
    budgetTokens: 8192  // -1 for dynamic, 0 to disable
  }
});

Streaming Thinking Content

When streaming, thinking content is delivered through specific events:

const s = streamSimple(model, context, { reasoning: 'high' });

for await (const event of s) {
  switch (event.type) {
    case 'thinking_start':
      console.log('[Model started thinking]');
      break;
    case 'thinking_delta':
      process.stdout.write(event.delta);  // Stream thinking content
      break;
    case 'thinking_end':
      console.log('\n[Thinking complete]');
      break;
  }
}

Stop Reasons

Every AssistantMessage includes a stopReason field that indicates how the generation ended:

• "stop" - Normal completion, the model finished its response
• "length" - Output hit the maximum token limit
• "toolUse" - Model is calling tools and expects tool results
• "error" - An error occurred during generation
• "aborted" - Request was cancelled via abort signal

Error Handling

When a request ends with an error (including aborts and tool call validation errors), the streaming API emits an error event:

// In streaming
for await (const event of stream) {
  if (event.type === 'error') {
    // event.reason is either "error" or "aborted"
    // event.error is the AssistantMessage with partial content
    console.error(`Error (${event.reason}):`, event.error.errorMessage);
    console.log('Partial content:', event.error.content);
  }
}

// The final message will have the error details
const message = await stream.result();
if (message.stopReason === 'error' || message.stopReason === 'aborted') {
  console.error('Request failed:', message.errorMessage);
  // message.content contains any partial content received before the error
  // message.usage contains partial token counts and costs
}

Aborting Requests

The abort signal allows you to cancel in-progress requests. Aborted requests have stopReason === 'aborted':

import { getModel, stream } from '@mariozechner/pi-ai';

const model = getModel('openai', 'gpt-4o-mini');
const controller = new AbortController();

// Abort after 2 seconds
setTimeout(() => controller.abort(), 2000);

const s = stream(model, {
  messages: [{ role: 'user', content: 'Write a long story' }]
}, {
  signal: controller.signal
});

for await (const event of s) {
  if (event.type === 'text_delta') {
    process.stdout.write(event.delta);
  } else if (event.type === 'error') {
    // event.reason tells you if it was "error" or "aborted"
    console.log(`${event.reason === 'aborted' ? 'Aborted' : 'Error'}:`, event.error.errorMessage);
  }
}

// Get results (may be partial if aborted)
const response = await s.result();
if (response.stopReason === 'aborted') {
  console.log('Request was aborted:', response.errorMessage);
  console.log('Partial content received:', response.content);
  console.log('Tokens used:', response.usage);
}

Continuing After Abort

Aborted messages can be added to the conversation context and continued in subsequent requests:

const context = {
  messages: [
    { role: 'user', content: 'Explain quantum computing in detail' }
  ]
};

// First request gets aborted after 2 seconds
const controller1 = new AbortController();
setTimeout(() => controller1.abort(), 2000);

const partial = await complete(model, context, { signal: controller1.signal });

// Add the partial response to context
context.messages.push(partial);
context.messages.push({ role: 'user', content: 'Please continue' });

// Continue the conversation
const continuation = await complete(model, context);

Debugging Provider Payloads

Use the onPayload callback to inspect the request payload sent to the provider. This is useful for debugging request formatting issues or provider validation errors.

const response = await complete(model, context, {
  onPayload: (payload) => {
    console.log('Provider payload:', JSON.stringify(payload, null, 2));
  }
});

The callback is supported by stream, complete, streamSimple, and completeSimple.

APIs, Models, and Providers

The library uses a registry of API implementations. Built-in APIs include:

• anthropic-messages: Anthropic Messages API (streamAnthropic, AnthropicOptions)
• google-generative-ai: Google Generative AI API (streamGoogle, GoogleOptions)
• google-gemini-cli: Google Cloud Code Assist API (streamGoogleGeminiCli, GoogleGeminiCliOptions)
• google-vertex: Google Vertex AI API (streamGoogleVertex, GoogleVertexOptions)
• openai-completions: OpenAI Chat Completions API (streamOpenAICompletions, OpenAICompletionsOptions)
• openai-responses: OpenAI Responses API (streamOpenAIResponses, OpenAIResponsesOptions)
• openai-codex-responses: OpenAI Codex Responses API (streamOpenAICodexResponses, OpenAICodexResponsesOptions)
• azure-openai-responses: Azure OpenAI Responses API (streamAzureOpenAIResponses, AzureOpenAIResponsesOptions)
• bedrock-converse-stream: Amazon Bedrock Converse API (streamBedrock, BedrockOptions)

Providers and Models

A provider offers models through a specific API. For example:

• Anthropic models use the anthropic-messages API
• Google models use the google-generative-ai API
• OpenAI models use the openai-responses API
• Mistral, xAI, Cerebras, Groq, etc. models use the openai-completions API (OpenAI-compatible)

Querying Providers and Models

import { getProviders, getModels, getModel } from '@mariozechner/pi-ai';

// Get all available providers
const providers = getProviders();
console.log(providers); // ['openai', 'anthropic', 'google', 'xai', 'groq', ...]

// Get all models from a provider (fully typed)
const anthropicModels = getModels('anthropic');
for (const model of anthropicModels) {
  console.log(`${model.id}: ${model.name}`);
  console.log(`  API: ${model.api}`); // 'anthropic-messages'
  console.log(`  Context: ${model.contextWindow} tokens`);
  console.log(`  Vision: ${model.input.includes('image')}`);
  console.log(`  Reasoning: ${model.reasoning}`);
}

// Get a specific model (both provider and model ID are auto-completed in IDEs)
const model = getModel('openai', 'gpt-4o-mini');
console.log(`Using ${model.name} via ${model.api} API`);

Custom Models

You can create custom models for local inference servers or custom endpoints:

import { Model, stream } from '@mariozechner/pi-ai';

// Example: Ollama using OpenAI-compatible API
const ollamaModel: Model<'openai-completions'> = {
  id: 'llama-3.1-8b',
  name: 'Llama 3.1 8B (Ollama)',
  api: 'openai-completions',
  provider: 'ollama',
  baseUrl: 'http://localhost:11434/v1',
  reasoning: false,
  input: ['text'],
  cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
  contextWindow: 128000,
  maxTokens: 32000
};

// Example: LiteLLM proxy with explicit compat settings
const litellmModel: Model<'openai-completions'> = {
  id: 'gpt-4o',
  name: 'GPT-4o (via LiteLLM)',
  api: 'openai-completions',
  provider: 'litellm',
  baseUrl: 'http://localhost:4000/v1',
  reasoning: false,
  input: ['text', 'image'],
  cost: { input: 2.5, output: 10, cacheRead: 0, cacheWrite: 0 },
  contextWindow: 128000,
  maxTokens: 16384,
  compat: {
    supportsStore: false,  // LiteLLM doesn't support the store field
  }
};

// Example: Custom endpoint with headers (bypassing Cloudflare bot detection)
const proxyModel: Model<'anthropic-messages'> = {
  id: 'claude-sonnet-4',
  name: 'Claude Sonnet 4 (Proxied)',
  api: 'anthropic-messages',
  provider: 'custom-proxy',
  baseUrl: 'https://proxy.example.com/v1',
  reasoning: true,
  input: ['text', 'image'],
  cost: { input: 3, output: 15, cacheRead: 0.3, cacheWrite: 3.75 },
  contextWindow: 200000,
  maxTokens: 8192,
  headers: {
    'User-Agent': 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36',
    'X-Custom-Auth': 'bearer-token-here'
  }
};

// Use the custom model
const response = await stream(ollamaModel, context, {
  apiKey: 'dummy' // Ollama doesn't need a real key
});

OpenAI Compatibility Settings

The openai-completions API is implemented by many providers with minor differences. By default, the library auto-detects compatibility settings based on baseUrl for known providers (Cerebras, xAI, Mistral, Chutes, etc.). For custom proxies or unknown endpoints, you can override these settings via the compat field. For openai-responses models, the compat field only supports Responses-specific flags.

interface OpenAICompletionsCompat {
  supportsStore?: boolean;           // Whether provider supports the `store` field (default: true)
  supportsDeveloperRole?: boolean;   // Whether provider supports `developer` role vs `system` (default: true)
  supportsReasoningEffort?: boolean; // Whether provider supports `reasoning_effort` (default: true)
  supportsUsageInStreaming?: boolean; // Whether provider supports `stream_options: { include_usage: true }` (default: true)
  supportsStrictMode?: boolean;      // Whether provider supports `strict` in tool definitions (default: true)
  maxTokensField?: 'max_completion_tokens' | 'max_tokens';  // Which field name to use (default: max_completion_tokens)
  requiresToolResultName?: boolean;  // Whether tool results require the `name` field (default: false)
  requiresAssistantAfterToolResult?: boolean; // Whether tool results must be followed by an assistant message (default: false)
  requiresThinkingAsText?: boolean;  // Whether thinking blocks must be converted to text (default: false)
  requiresMistralToolIds?: boolean;  // Whether tool call IDs must be normalized to Mistral format (default: false)
  thinkingFormat?: 'openai' | 'zai' | 'qwen'; // Format for reasoning param: 'openai' uses reasoning_effort, 'zai' uses thinking: { type: "enabled" }, 'qwen' uses enable_thinking: boolean (default: openai)
  openRouterRouting?: OpenRouterRouting; // OpenRouter routing preferences (default: {})
  vercelGatewayRouting?: VercelGatewayRouting; // Vercel AI Gateway routing preferences (default: {})
}

interface OpenAIResponsesCompat {
  // Reserved for future use
}

If compat is not set, the library falls back to URL-based detection. If compat is partially set, unspecified fields use the detected defaults. This is useful for:

• LiteLLM proxies: May not support store field
• Custom inference servers: May use non-standard field names
• Self-hosted endpoints: May have different feature support

Type Safety

Models are typed by their API, which keeps the model metadata accurate. Provider-specific option types are enforced when you call the provider functions directly. The generic stream and complete functions accept StreamOptions with additional provider fields.

import { streamAnthropic, type AnthropicOptions } from '@mariozechner/pi-ai';

// TypeScript knows this is an Anthropic model
const claude = getModel('anthropic', 'claude-sonnet-4-20250514');

const options: AnthropicOptions = {
  thinkingEnabled: true,
  thinkingBudgetTokens: 2048
};

await streamAnthropic(claude, context, options);

Cross-Provider Handoffs

The library supports seamless handoffs between different LLM providers within the same conversation. This allows you to switch models mid-conversation while preserving context, including thinking blocks, tool calls, and tool results.

How It Works

When messages from one provider are sent to a different provider, the library automatically transforms them for compatibility:

• User and tool result messages are passed through unchanged
• Assistant messages from the same provider/API are preserved as-is
• Assistant messages from different providers have their thinking blocks converted to text with <thinking> tags
• Tool calls and regular text are preserved unchanged

Example: Multi-Provider Conversation

import { getModel, complete, Context } from '@mariozechner/pi-ai';

// Start with Claude
const claude = getModel('anthropic', 'claude-sonnet-4-20250514');
const context: Context = {
  messages: []
};

context.messages.push({ role: 'user', content: 'What is 25 * 18?' });
const claudeResponse = await complete(claude, context, {
  thinkingEnabled: true
});
context.messages.push(claudeResponse);

// Switch to GPT-5 - it will see Claude's thinking as <thinking> tagged text
const gpt5 = getModel('openai', 'gpt-5-mini');
context.messages.push({ role: 'user', content: 'Is that calculation correct?' });
const gptResponse = await complete(gpt5, context);
context.messages.push(gptResponse);

// Switch to Gemini
const gemini = getModel('google', 'gemini-2.5-flash');
context.messages.push({ role: 'user', content: 'What was the original question?' });
const geminiResponse = await complete(gemini, context);

Provider Compatibility

All providers can handle messages from other providers, including:

• Text content
• Tool calls and tool results (including images in tool results)
• Thinking/reasoning blocks (transformed to tagged text for cross-provider compatibility)
• Aborted messages with partial content

This enables flexible workflows where you can:

• Start with a fast model for initial responses
• Switch to a more capable model for complex reasoning
• Use specialized models for specific tasks
• Maintain conversation continuity across provider outages

Context Serialization

The Context object can be easily serialized and deserialized using standard JSON methods, making it simple to persist conversations, implement chat history, or transfer contexts between services:

import { Context, getModel, complete } from '@mariozechner/pi-ai';

// Create and use a context
const context: Context = {
  systemPrompt: 'You are a helpful assistant.',
  messages: [
    { role: 'user', content: 'What is TypeScript?' }
  ]
};

const model = getModel('openai', 'gpt-4o-mini');
const response = await complete(model, context);
context.messages.push(response);

// Serialize the entire context
const serialized = JSON.stringify(context);
console.log('Serialized context size:', serialized.length, 'bytes');

// Save to database, localStorage, file, etc.
localStorage.setItem('conversation', serialized);

// Later: deserialize and continue the conversation
const restored: Context = JSON.parse(localStorage.getItem('conversation')!);
restored.messages.push({ role: 'user', content: 'Tell me more about its type system' });

// Continue with any model
const newModel = getModel('anthropic', 'claude-3-5-haiku-20241022');
const continuation = await complete(newModel, restored);

Note: If the context contains images (encoded as base64 as shown in the Image Input section), those will also be serialized.

Browser Usage

The library supports browser environments. You must pass the API key explicitly since environment variables are not available in browsers:

import { getModel, complete } from '@mariozechner/pi-ai';

// API key must be passed explicitly in browser
const model = getModel('anthropic', 'claude-3-5-haiku-20241022');

const response = await complete(model, {
  messages: [{ role: 'user', content: 'Hello!' }]
}, {
  apiKey: 'your-api-key'
});

Security Warning: Exposing API keys in frontend code is dangerous. Anyone can extract and abuse your keys. Only use this approach for internal tools or demos. For production applications, use a backend proxy that keeps your API keys secure.

Environment Variables (Node.js only)

In Node.js environments, you can set environment variables to avoid passing API keys:

Provider	Environment Variable(s)
OpenAI	OPENAI_API_KEY
Azure OpenAI	AZURE_OPENAI_API_KEY + AZURE_OPENAI_BASE_URL or AZURE_OPENAI_RESOURCE_NAME (optional AZURE_OPENAI_API_VERSION, AZURE_OPENAI_DEPLOYMENT_NAME_MAP like model=deployment,model2=deployment2)
Anthropic	ANTHROPIC_API_KEY or ANTHROPIC_OAUTH_TOKEN
Google	GEMINI_API_KEY
Vertex AI	GOOGLE_CLOUD_PROJECT (or GCLOUD_PROJECT) + GOOGLE_CLOUD_LOCATION + ADC
Mistral	MISTRAL_API_KEY
Groq	GROQ_API_KEY
Cerebras	CEREBRAS_API_KEY
xAI	XAI_API_KEY
OpenRouter	OPENROUTER_API_KEY
Vercel AI Gateway	AI_GATEWAY_API_KEY
zAI	ZAI_API_KEY
MiniMax	MINIMAX_API_KEY
Kimi For Coding	KIMI_API_KEY
GitHub Copilot	COPILOT_GITHUB_TOKEN or GH_TOKEN or GITHUB_TOKEN

When set, the library automatically uses these keys:

// Uses OPENAI_API_KEY from environment
const model = getModel('openai', 'gpt-4o-mini');
const response = await complete(model, context);

// Or override with explicit key
const response = await complete(model, context, {
  apiKey: 'sk-different-key'
});

Antigravity Version Override

Set PI_AI_ANTIGRAVITY_VERSION to override the Antigravity User-Agent version when Google updates their requirements:

export PI_AI_ANTIGRAVITY_VERSION="1.23.0"

Cache Retention

Set PI_CACHE_RETENTION=long to extend prompt cache retention:

Provider	Default	With PI_CACHE_RETENTION=long
Anthropic	5 minutes	1 hour
OpenAI	in-memory	24 hours

This only affects direct API calls to api.anthropic.com and api.openai.com. Proxies and other providers are unaffected.

Note: Extended cache retention may increase costs for Anthropic (cache writes are charged at a higher rate). OpenAI's 24h retention has no additional cost.

Checking Environment Variables

import { getEnvApiKey } from '@mariozechner/pi-ai';

// Check if an API key is set in environment variables
const key = getEnvApiKey('openai');  // checks OPENAI_API_KEY

OAuth Providers

Several providers require OAuth authentication instead of static API keys:

• Anthropic (Claude Pro/Max subscription)
• OpenAI Codex (ChatGPT Plus/Pro subscription, access to GPT-5.x Codex models)
• GitHub Copilot (Copilot subscription)
• Google Gemini CLI (Gemini 2.0/2.5 via Google Cloud Code Assist; free tier or paid subscription)
• Antigravity (Free Gemini 3, Claude, GPT-OSS via Google Cloud)

For paid Cloud Code Assist subscriptions, set GOOGLE_CLOUD_PROJECT or GOOGLE_CLOUD_PROJECT_ID to your project ID.

Vertex AI (ADC)

Vertex AI models use Application Default Credentials (ADC):

• Local development: Run gcloud auth application-default login
• CI/Production: Set GOOGLE_APPLICATION_CREDENTIALS to point to a service account JSON key file

Also set GOOGLE_CLOUD_PROJECT (or GCLOUD_PROJECT) and GOOGLE_CLOUD_LOCATION. You can also pass project/location in the call options.

Example:

# Local (uses your user credentials)
gcloud auth application-default login
export GOOGLE_CLOUD_PROJECT="my-project"
export GOOGLE_CLOUD_LOCATION="us-central1"

# CI/Production (service account key file)
export GOOGLE_APPLICATION_CREDENTIALS="/path/to/service-account.json"

import { getModel, complete } from '@mariozechner/pi-ai';

(async () => {
  const model = getModel('google-vertex', 'gemini-2.5-flash');
  const response = await complete(model, {
    messages: [{ role: 'user', content: 'Hello from Vertex AI' }]
  });

  for (const block of response.content) {
    if (block.type === 'text') console.log(block.text);
  }
})().catch(console.error);

Official docs: Application Default Credentials

CLI Login

The quickest way to authenticate:

npx @mariozechner/pi-ai login              # interactive provider selection
npx @mariozechner/pi-ai login anthropic    # login to specific provider
npx @mariozechner/pi-ai list               # list available providers

Credentials are saved to auth.json in the current directory.

Programmatic OAuth

The library provides login and token refresh functions. Credential storage is the caller's responsibility.

import {
  // Login functions (return credentials, do not store)
  loginAnthropic,
  loginOpenAICodex,
  loginGitHubCopilot,
  loginGeminiCli,
  loginAntigravity,

  // Token management
  refreshOAuthToken,   // (provider, credentials) => new credentials
  getOAuthApiKey,      // (provider, credentialsMap) => { newCredentials, apiKey } | null

  // Types
  type OAuthProvider,  // 'anthropic' | 'openai-codex' | 'github-copilot' | 'google-gemini-cli' | 'google-antigravity'
  type OAuthCredentials,
} from '@mariozechner/pi-ai';

Login Flow Example

import { loginGitHubCopilot } from '@mariozechner/pi-ai';
import { writeFileSync } from 'fs';

const credentials = await loginGitHubCopilot({
  onAuth: (url, instructions) => {
    console.log(`Open: ${url}`);
    if (instructions) console.log(instructions);
  },
  onPrompt: async (prompt) => {
    return await getUserInput(prompt.message);
  },
  onProgress: (message) => console.log(message)
});

// Store credentials yourself
const auth = { 'github-copilot': { type: 'oauth', ...credentials } };
writeFileSync('auth.json', JSON.stringify(auth, null, 2));

Using OAuth Tokens

Use getOAuthApiKey() to get an API key, automatically refreshing if expired:

import { getModel, complete, getOAuthApiKey } from '@mariozechner/pi-ai';
import { readFileSync, writeFileSync } from 'fs';

// Load your stored credentials
const auth = JSON.parse(readFileSync('auth.json', 'utf-8'));

// Get API key (refreshes if expired)
const result = await getOAuthApiKey('github-copilot', auth);
if (!result) throw new Error('Not logged in');

// Save refreshed credentials
auth['github-copilot'] = { type: 'oauth', ...result.newCredentials };
writeFileSync('auth.json', JSON.stringify(auth, null, 2));

// Use the API key
const model = getModel('github-copilot', 'gpt-4o');
const response = await complete(model, {
  messages: [{ role: 'user', content: 'Hello!' }]
}, { apiKey: result.apiKey });

Provider Notes

OpenAI Codex: Requires a ChatGPT Plus or Pro subscription. Provides access to GPT-5.x Codex models with extended context windows and reasoning capabilities. The library automatically handles session-based prompt caching when sessionId is provided in stream options. You can set transport in stream options to "sse", "websocket", or "auto" for Codex Responses transport selection. When using WebSocket with a sessionId, connections are reused per session and expire after 5 minutes of inactivity.

Azure OpenAI (Responses): Uses the Responses API only. Set AZURE_OPENAI_API_KEY and either AZURE_OPENAI_BASE_URL or AZURE_OPENAI_RESOURCE_NAME. Use AZURE_OPENAI_API_VERSION (defaults to v1) to override the API version if needed. Deployment names are treated as model IDs by default, override with azureDeploymentName or AZURE_OPENAI_DEPLOYMENT_NAME_MAP using comma-separated model-id=deployment pairs (for example gpt-4o-mini=my-deployment,gpt-4o=prod). Legacy deployment-based URLs are intentionally unsupported.

GitHub Copilot: If you get "The requested model is not supported" error, enable the model manually in VS Code: open Copilot Chat, click the model selector, select the model (warning icon), and click "Enable".

Google Gemini CLI / Antigravity: These use Google Cloud OAuth. The apiKey returned by getOAuthApiKey() is a JSON string containing both the token and project ID, which the library handles automatically.

Development

Adding a New Provider

Adding a new LLM provider requires changes across multiple files. This checklist covers all necessary steps:

1. Core Types (src/types.ts)

• Add the API identifier to KnownApi (for example "bedrock-converse-stream")
• Create an options interface extending StreamOptions (for example BedrockOptions)
• Add the provider name to KnownProvider (for example "amazon-bedrock")

2. Provider Implementation (src/providers/)

Create a new provider file (for example amazon-bedrock.ts) that exports:

• stream<Provider>() function returning AssistantMessageEventStream
• streamSimple<Provider>() for SimpleStreamOptions mapping
• Provider-specific options interface
• Message conversion functions to transform Context to provider format
• Tool conversion if the provider supports tools
• Response parsing to emit standardized events (text, tool_call, thinking, usage, stop)

3. API Registry Integration (src/providers/register-builtins.ts)

• Register the API with registerApiProvider()
• Add credential detection in env-api-keys.ts for the new provider
• Ensure streamSimple handles auth lookup via getEnvApiKey() or provider-specific auth

4. Model Generation (scripts/generate-models.ts)

• Add logic to fetch and parse models from the provider's source (e.g., models.dev API)
• Map provider model data to the standardized Model interface
• Handle provider-specific quirks (pricing format, capability flags, model ID transformations)

5. Tests (test/)

Create or update test files to cover the new provider:

• stream.test.ts - Basic streaming and tool use
• tokens.test.ts - Token usage reporting
• abort.test.ts - Request cancellation
• empty.test.ts - Empty message handling
• context-overflow.test.ts - Context limit errors
• image-limits.test.ts - Image support (if applicable)
• unicode-surrogate.test.ts - Unicode handling
• tool-call-without-result.test.ts - Orphaned tool calls
• image-tool-result.test.ts - Images in tool results
• total-tokens.test.ts - Token counting accuracy
• cross-provider-handoff.test.ts - Cross-provider context replay

For cross-provider-handoff.test.ts, add at least one provider/model pair. If the provider exposes multiple model families (for example GPT and Claude), add at least one pair per family.

For providers with non-standard auth (AWS, Google Vertex), create a utility like bedrock-utils.ts with credential detection helpers.

6. Coding Agent Integration (../coding-agent/)

Update src/core/model-resolver.ts:

• Add a default model ID for the provider in DEFAULT_MODELS

Update src/cli/args.ts:

• Add environment variable documentation in the help text

Update README.md:

• Add the provider to the providers section with setup instructions

7. Documentation

Update packages/ai/README.md:

• Add to the Supported Providers table
• Document any provider-specific options or authentication requirements
• Add environment variable to the Environment Variables section

8. Changelog

Add an entry to packages/ai/CHANGELOG.md under ## [Unreleased]:

### Added
- Added support for [Provider Name] provider ([#PR](link) by [@author](link))

License

MIT