Google Image generation support

[OreOreDa]

Closes GH-2133

• MR updated with the latest GenAI sdk, and the new options for image generation
• Use of the new generate content API
• Documentation and tests updated
• Tested with "gemini-2.5-flash-image" in my project

Thanks !

[sdeleuze]

@ddobrin Could you please review this PR?

[OreOreDa]

@ddobrin @sdeleuze

I added the image editing feature of GenAI - the medias have been added in ImageMessage, as for UserMessage
Thanks !

[ddobrin]

Thanks for this PR, @OreOreDa — it's a substantial contribution.
Basic aspects are solid: the google-genai 1.58.0 SDK usage is almost the latest and can be easily replaced with 1.60.0, retry/observation follow the current conventions, and making ImageMessage implement MediaContent is the right way to carry image input.

I'd like to make a few notes, some in code and some in docs: for example using professional names as in replace "Nano Banana", "Nano Banana Pro", and "Nano Banana 2" with professional descriptions, such as "Gemini 2.5 Flash Image Model", "Gemini 3 Pro Image Model", and "Gemini 3.1 Flash Image Model".

🔴 Fix before merge

1. Per-request options silently override a model-level configured model. Because the GoogleGenAiImageOptions constructor always bakes in a non-null default model and buildImagePrompt then applies from(googleOptions) unconditionally, a user who configures e.g. gemini-3-pro-image on the model bean and passes a per-request options object that didn't call .model(...) is silently downgraded to the default. See inline on GoogleGenAiImageModel.java and GoogleGenAiImageOptions.java.

2. Vertex AI credentials-uri is silently ignored. The GoogleCredentials are loaded and then never passed to the connection builder (so they never reach the Client), meaning the URI a user supplies has no effect — and it's documented as working. See inline on GoogleGenAiImageConnectionAutoConfiguration.java.

3. A unit test should lock in the merge fix — there's currently no test that exercises option merge with a model-level default present, which is exactly why Fix errors and omissions in docs #1 slipped through.

🟠 Should fix

• Response text parts are silently dropped — a refusal/finish-reason returned as text yields an empty result with no explanation.
• ImageMessage.equals/hashCode/toString ignore the new media/metadata fields, and media is non-final with getMedia() exposing the internal list — diverges from UserMessage/AssistantMessage.
• Two @ConfigurationProperties classes bind the same prefix spring.ai.google.genai.image.
• Docs: the page is not registered in nav.adoc/imageclient.adoc; the property table uses a .options. prefix that won't bind; and the Manual Configuration samples call imageModel.call("..."), which doesn't compile.
• Test: imageModelActivation is gated behind GOOGLE_API_KEY it doesn't actually use, so this wiring check is skipped in CI.

🟡 Check (minor issues)

Metadata is effectively always empty (gcsUri/enhancedPrompt/raiFilteredReason always null; empty ImageResponseMetadata); n → candidateCount doesn't reliably yield N images; PERSON_GENERATION_UNSPECIFIED is sent unguarded while the safety UNSPECIFIED is correctly suppressed; Builder.from() is a conditional copy and copies labels by reference; getResponseFormat() is repurposed to carry a MIME type; GoogleGenAiImageOptions has no equals/hashCode/toString; connection autoconfig isn't gated by spring.ai.model.image; a few stale doc values (n default, broken GitHub source link, SAFETY_FILTER_LEVEL_UNSPECIFIED), and the BOM lost its trailing newline. Details inline / happy to expand on any.

What's good

Correct SDK type bindings (verified against 1.58.0, should upgrade to 1.60.0), the four BLOCK_* levels match the SDK enum and ..._UNSPECIFIED is guarded, retry via org.springframework.core.retry.RetryTemplate matches the chat module, observation parity with OpenAI, a backward/binary-compatible core change, clean and correctly-sorted BOM/starter/module wiring, and good branch-level retry/media unit coverage.

[ddobrin]

Part II - code comments

models/.../image/GoogleGenAiImageModel.java — lines 193–200 (buildImagePrompt)

🔴 Merge precedence bug. builder.from(this.options) (L193) seeds the model-level config, but builder.from(googleOptions) (L200) then re-applies the per-request options unconditionally. Combined with the constructor below always baking in a default model, a request whose options didn't set .model(...) clobbers the model-level model. Suggest the OpenAI pattern: a single full copy of this.options followed by a single null-guarded merge(runtimeOptions); drop the second from() and the duplicated explicit model/n/outputMimeType lines.

models/.../image/GoogleGenAiImageOptions.java — line 132 (constructor)

🔴 Root cause of the merge bug. this.model = (model != null ? model : DEFAULT_MODEL_NAME) forces a non-null model into every options instance, so "unset" becomes indistinguishable from "set to the default" and null-skip merge can't tell which layer should win. Either don't bake the default here, or ensure only one merge path applies it.

auto-configurations/.../image/GoogleGenAiImageConnectionAutoConfiguration.java — lines 64–66

🔴 Dead credentials / silent failure. The GoogleCredentials loaded here are never passed to the GoogleGenAiImageConnectionDetails builder (only apiKey/projectId/location are), so they never reach the Client and credentials-uri has no effect. Add credentials(GoogleCredentials) to GoogleGenAiImageConnectionDetails.Builder, thread it into Client.Builder.credentials(...) (available in 1.58.0), and load via try-with-resources as the chat autoconfig does. Please also remove the misleading comment on L66 and apply the same fix to the embedding sibling for parity.

models/.../image/GoogleGenAiImageModel.java — lines 156, 216

🟠 Text parts silently discarded. responseModalities("TEXT","IMAGE") (L216) requests text, but only Part::inlineData parts are mapped (L156). When the model returns a refusal/finish-reason as text and no image, the caller gets an empty result with no signal. Either request IMAGE only, or surface the text into ImageResponseMetadata/per-generation metadata.

models/.../image/GoogleGenAiImageModel.java — lines 163, 165, 172

🟡 Metadata always empty. new Image(null, b64Json) (L163) then feeding image.getUrl() into the metadata (L165) means gcsUri (and enhancedPrompt/raiFilteredReason) are always null, and ImageResponseMetadata (L172) is empty. Consider populating what the SDK exposes (model name, etc.).

models/.../image/GoogleGenAiImageModel.java — line 132

🟡 Uses the original prompt, not the built one. call() builds imagePrompt (L111) but L132 iterates prompt.getInstructions() (the original arg). Harmless today since instructions are copied through, but fragile — prefer imagePrompt.getInstructions().

spring-ai-model/.../image/ImageMessage.java — lines 37, 80–94

🟠 equals/hashCode/toString ignore the new state, and media is mutable. equals (L80) / hashCode (L91) use only text+weight, and toString (L75) omits media/metadata, so two messages differing only in attached media compare equal. The media field (L37) is non-final and getMedia() returns the internal list. Suggest including both fields in equals/hashCode/toString and making media final, to match AssistantMessage. Also missing @since/Javadoc on the new public API (4-arg ctor, getMedia, getMetadata).

auto-configurations/.../image/GoogleGenAiImageConnectionProperties.java — line 33 & GoogleGenAiImageProperties.java — line 35

🟠 Duplicate prefix. Both classes declare CONFIG_PREFIX = "spring.ai.google.genai.image". Two @ConfigurationProperties on the same namespace is ambiguous — follow the embedding precedent and nest the model options (e.g. spring.ai.google.genai.image.options) or split connection onto the shared spring.ai.google.genai prefix. (Note vertexAi at ConnectionProperties:59 is bound but never read.)

spring-ai-docs/.../nav.adoc — after line 54

🟠 Page is orphaned. Image entries live at L52–54 but Google GenAI isn't listed (nor in imageclient.adoc "Available Implementations", L158–163), so it won't appear in the docs nav.

**** xref:api/image/stabilityai-image.adoc[Stability]
**** xref:api/image/google-genai-image.adoc[Google GenAI]

spring-ai-docs/.../api/image/google-genai-image.adoc — line 116 (and the whole table, L116–129)

🟠 Property prefix won't bind. The model-options table uses a .options. segment, but the binding is flat (spring.ai.google.genai.image.n, matching your own Sample Controller). Remove .options. from every row. Example for L116:

| spring.ai.google.genai.image.n | The number of images to generate. | -

spring-ai-docs/.../api/image/google-genai-image.adoc — lines 223–224 (and 243–244)

🟠 Sample doesn't compile. ImageModel only declares call(ImagePrompt) (no call(String)).

ImageResponse imageResponse = imageModel
	.call(new ImagePrompt("A painting of a sunset over a mountain", options));

spring-ai-docs/.../api/image/google-genai-image.adoc — line 183

🟡 Broken source link. The GitHub URL omits the /image/ package segment, so it 404s. Should point to .../org/springframework/ai/google/genai/image/GoogleGenAiImageModel.java.

auto-configurations/.../image/GoogleGenAiImageAutoConfigurationIT.java — lines 80–81

🟠 Wiring test skipped in CI. imageModelActivation only uses a fake test-key (L83) but is gated by @EnabledIfEnvironmentVariable(GOOGLE_API_KEY) (L80), so this conditional-bean check never runs without real credentials. Remove the gate (or split it out) so it runs as a plain context test.