Image generation with AiService using Gemini

[zbhavyai]

I am using quarkus-langchain4j version 1.1.1 and trying to write a service that generates images based on the given prompt using Gemini API. My service is like this:

@RegisterAiService
@ApplicationScoped
public interface ImageGenerator {

  @UserMessage(
      """
      Generate an image that visually represents the following quote:
      "{quoteText}"
      """)
  Image generateImage(String quoteText);
}

I have quarkus-langchain4j-ai-gemini dependency in my pom.xml. My application.properties is like this:

quarkus.langchain4j.ai.gemini.api-key=XXXXXXXXXXXX
quarkus.langchain4j.ai.gemini.chat-model.enabled=true
quarkus.langchain4j.ai.gemini.chat-model.model-id=gemini-2.5-flash
quarkus.langchain4j.image-model.provider=ai-gemini
quarkus.langchain4j.ai.gemini.log-requests=true
quarkus.langchain4j.ai.gemini.log-responses=false
quarkus.langchain4j.ai.gemini.timeout=30s

When running the app in dev mode, I get this error:

2025-08-25 00:46:08,014 ERROR [io.qua.dep.dev.IsolatedDevModeMain] (main) Failed to start quarkus: java.lang.RuntimeException: io.quarkus.builder.BuildException: Build failure: Build failed due to errors
	[error]: Build step io.quarkiverse.langchain4j.deployment.BeansProcessor#handleProviders threw an exception: io.quarkus.runtime.configuration.ConfigurationException: A ImageModel bean was requested, but no langchain4j providers were configured. Consider adding an extension like 'quarkus-langchain4j-openai'
	at io.quarkiverse.langchain4j.deployment.BeansProcessor.selectProvider(BeansProcessor.java:498)
	at io.quarkiverse.langchain4j.deployment.BeansProcessor.handleProviders(BeansProcessor.java:314)
	at java.base/java.lang.invoke.MethodHandle.invokeWithArguments(MethodHandle.java:733)
	at io.quarkus.deployment.ExtensionLoader$3.execute(ExtensionLoader.java:856)
	at io.quarkus.builder.BuildContext.run(BuildContext.java:255)
	at org.jboss.threads.ContextHandler$1.runWith(ContextHandler.java:18)
	at org.jboss.threads.EnhancedQueueExecutor$Task.doRunWith(EnhancedQueueExecutor.java:2651)
	at org.jboss.threads.EnhancedQueueExecutor$Task.run(EnhancedQueueExecutor.java:2630)
	at org.jboss.threads.EnhancedQueueExecutor.runThreadBody(EnhancedQueueExecutor.java:1622)
	at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.run(EnhancedQueueExecutor.java:1589)
	at java.base/java.lang.Thread.run(Thread.java:1583)
	at org.jboss.threads.JBossThread.run(JBossThread.java:501)

So, is the Image generation supported for Gemini, or are there plans for it? I don't see image related properties listed in the documentation, but looking at the PR #1325 I thought its supported.

Thank you in advance!

[geoand]

Thanks for reporting!

Indeed there is no implementation of ImageModel for Google Gemini. @glaforge is that something on your radar for upstream LangChain4j?

#1325 was about being able to describe an image or video, not generate them. Sorry for the confusion.