v0.3.3 causes illegal argument exception in Google GenAi - Only one system message is allowed in the prompt

[LiveNathan]

All tests were passing. I upgraded from 0.3.2 to 0.3.3 and now they are all failing for the same reason: java.lang.IllegalArgumentException: Only one system message is allowed in the prompt

Here's an example usage:

ClassifiedIntents classifyIntent(String userMessage, Ai ai) {
        return ai.withLlm(LlmOptions.withFirstAvailableLlmOf(ModelRole.BALANCED.preferredModels()).withTemperature(0.1))
                .withId("classify-intent")
                .creating(ClassifiedIntents.class)
                .withExample("Request example: Where's the lead vocal? Send it to the vocal buss.", createIndependentRequestsExample())
                .withExample("Request example: Rename channels 1-4 to RF 1-4 then change the color to red and then disable routes to main.", createCompoundRequestExample())
                .withExample("Request example: Hello there!", createOtherRequestExample())
                .fromPrompt(createClassifyIntentPrompt(userMessage));
    }

It fails:

09:53:05.428 [ForkJoinPool-1-worker-1] INFO Embabel - [strange_hopper] (classify-intent) using LLM gemini-2.5-flash, creating ClassifiedIntents: LlmOptions(modelSelectionCriteria=FallbackByNameModelSelectionCriteria(names=[gemini-2.5-flash, gemini-2.5-pro, gemini-2.0-flash, llama3.2:latest, llama3.1:8b, llama3.2:1b]), model=null, role=null, temperature=0.1, frequencyPenalty=null, maxTokens=null, presencePenalty=null, topK=null, topP=null, thinking=null, timeout=null)
09:53:05.429 [ForkJoinPool-1-worker-1] INFO RetryProperties - Operation googlegenai-gemini-2.5-flash: Retry error. Retry count: 1
java.lang.IllegalArgumentException: Only one system message is allowed in the prompt
at org.springframework.util.Assert.isTrue(Assert.java:116)
at org.springframework.ai.google.genai.GoogleGenAiChatModel.createGeminiRequest(GoogleGenAiChatModel.java:823)
at org.springframework.ai.google.genai.GoogleGenAiChatModel.lambda$internalCall$3(GoogleGenAiChatModel.java:439)
at org.springframework.retry.support.RetryTemplate.doExecute(RetryTemplate.java:357)
at org.springframework.retry.support.RetryTemplate.execute(RetryTemplate.java:230)
at org.springframework.ai.google.genai.GoogleGenAiChatModel.lambda$internalCall$4(GoogleGenAiChatModel.java:437)
at io.micrometer.observation.Observation.observe(Observation.java:564)
at org.springframework.ai.google.genai.GoogleGenAiChatModel.internalCall(GoogleGenAiChatModel.java:437)

I tried removing all of the examples. Same result. I tried removing withId. Same result. I will have to downgrade back to 0.3.2 until this is resolve.

Thanks!

[johnsonr]

Please try with 0.3.4-SNAPSHOT. System messages should be consolidated as a result of another change.

[azanux]

@LiveNathan I tried the code that looks like yours and it works on gemini 2.5 with embabel version 0.3.4 like @johnsonr said

But I noticed another issue with the tools when migrating from 0.3.2 to 0.3.4. I've created an issue and also a fix that I'm going to push. Just need to check if it doesn't cause any other problems.

#1383

import com.embabel.agent.api.annotation.AchievesGoal;
import com.embabel.agent.api.annotation.Action;
import com.embabel.agent.api.annotation.Agent;
import com.embabel.agent.api.common.Ai;
import com.embabel.agent.domain.io.UserInput;
import com.embabel.common.ai.model.LlmOptions;

import java.util.List;

@Agent(description = "Classify user messages into intents")
public class IntentClassifierAgent {

    public record Intent(String type, String summary) {}

    public record ClassifiedIntents(List<Intent> intents, String rawMessage) {}

    private static ClassifiedIntents singleIntentExample() {
        return new ClassifiedIntents(
                List.of(new Intent("QUESTION", "How to reset password")),
                "Hi, how do I reset my password?"
        );
    }

    private static ClassifiedIntents multipleIntentsExample() {
        return new ClassifiedIntents(
                List.of(
                        new Intent("BUG_REPORT", "Charts not loading"),
                        new Intent("FEATURE_REQUEST", "Add CSV export")
                ),
                "The charts don't load anymore. Also I'd like CSV export."
        );
    }

    private static ClassifiedIntents otherExample() {
        return new ClassifiedIntents(
                List.of(new Intent("OTHER", "Greeting")),
                "Hello there!"
        );
    }

    @AchievesGoal(description = "User message has been classified into intents")
    @Action
    public ClassifiedIntents classifyIntent(UserInput userInput, Ai ai) {
        return ai
                .withLlm(LlmOptions.withAutoLlm().withTemperature(0.1))
                .withId("classify-intent")
                .creating(ClassifiedIntents.class)
                .withExample("Single question", singleIntentExample())
                .withExample("Multiple intents in one message", multipleIntentsExample())
                .withExample("Other / greeting", otherExample())
                .fromPrompt(String.format("""
                        Classify the following message into intents.
                        Type must be one of: BUG_REPORT, FEATURE_REQUEST, QUESTION, COMPLAINT, OTHER.

                        Message: %s
                        """, userInput.getContent()).trim());
    }
}

[LiveNathan]

Please try with 0.3.4-SNAPSHOT. System messages should be consolidated as a result of another change.

That did it. All tests are passing again. Should I close the issue?

[LiveNathan]

Ah, I spoke too soon. Today the app will not start due to compilation error:

[ERROR] COMPILATION ERROR :
[INFO] -------------------------------------------------------------
[ERROR] /Users/nathanlively/dev/personal/console-whisperer-desktop/src/test/java/dev/nathanlively/adapter/out/ai/DummyChatbot.java:[10,7] error: DummyChatbot is not abstract and does not override abstract method createSession-xFKS4ws(User,OutputChannel,String,String) in Chatbot
[INFO] 1 error
[INFO] -------------------------------------------------------------
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 5.163 s
[INFO] Finished at: 2026-02-07T12:14:02-06:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.14.1:testCompile (default-testCompile) on project console-whisperer-desktop: Compilation failure
[ERROR] /Users/nathanlively/dev/personal/console-whisperer-desktop/src/test/java/dev/nathanlively/adapter/out/ai/DummyChatbot.java:[10,7] error: DummyChatbot is not abstract and does not override abstract method createSession-xFKS4ws(User,OutputChannel,String,String) in Chatbot

public class DummyChatbot implements Chatbot {

    @Override
//    public @NonNull ChatSession createSession(@Nullable User user, @NonNull OutputChannel outputChannel,@Nullable String systemMessage) {
    public @NonNull ChatSession createSession(@Nullable User user, @NonNull OutputChannel outputChannel, @NonNull String conversationId, @Nullable String systemMessage) {
        throw new UnsupportedOperationException("DummyChatbot should not be used");
    }

    @Override
    public @Nullable ChatSession findSession(@NonNull String conversationId) {
        throw new UnsupportedOperationException("DummyChatbot should not be used");
    }
}

Class 'DummyChatbot' must either be declared abstract or implement abstract method 'createSession-xFKS4ws(User, OutputChannel, String, String)' in 'Chatbot'

But If I try to implement this method with Intellij, nothing happens.

[LiveNathan]

Claude suggested a proxy workaround. Seems to work:

final class DummyChatbot {

    private DummyChatbot() {
    }

    static Chatbot create() {
        return (Chatbot) Proxy.newProxyInstance(
                Chatbot.class.getClassLoader(),
                new Class<?>[]{Chatbot.class},
                (proxy, method, args) -> {
                    throw new UnsupportedOperationException("DummyChatbot should not be used");
                });
    }
}

[azanux]

Claude suggested a proxy workaround. Seems to work:

final class DummyChatbot {

private DummyChatbot() {
}

static Chatbot create() {
    return (Chatbot) Proxy.newProxyInstance(
            Chatbot.class.getClassLoader(),
            new Class<?>[]{Chatbot.class},
            (proxy, method, args) -> {
                throw new UnsupportedOperationException("DummyChatbot should not be used");
            });
}

}

@LiveNathan, maybe you should create a new issue, because this new error doesn't match the title anymore. It will also prevent others with the same problem from being confused by the title.

[johnsonr]

There was a signature change in the Chatbot interface yesterday.

A ContextId param was added. It is now:

/**
     * Create a new chat session.
     * If user is provided, the session will be associated with that user.
     * If contextId is provided, the session will load objects from that context
     * into the blackboard (e.g., user preferences, prior state).
     * Optionally, a system message can be provided to set the context for the session.
     * @param user the user to associate the session with, or null for anonymous
     * @param outputChannel the output channel to send messages to
     * @param contextId optional context ID to load prior state from
     * @param systemMessage optional system message to set the context for the session
     */
    fun createSession(
        user: User?,
        outputChannel: OutputChannel,
        contextId: ContextId? = null,
        systemMessage: String? = null,
    ): ChatSession

I think the problem may be that ContextId is a value type and Java doesn't like it. Will try to reproduce.

Agree with azanux re issue hygiene but this time I'll look at this right now so let's resolve it here.