Google GenAI `models.generateImages()` (Imagen) not instrumented (wrapper and auto-instrumentation)

[braintrust-bot]

Summary

The @google/genai SDK provides a stable models.generateImages() method for AI-powered image generation using Imagen models, but neither the wrapper (wrapGoogleGenAI) nor the auto-instrumentation plugin instruments it. Calls to this method produce no Braintrust spans. By contrast, OpenAI's images.generate() is tracked as a gap in #1628, and the Vercel AI SDK's generateImage() in #1626 — this is the Google GenAI equivalent.

What is missing

• Wrapper (js/src/wrappers/google-genai.ts): wrapModels() only proxies generateContent and generateContentStream. generateImages calls pass through untraced.
• Auto-instrumentation config (js/src/auto-instrumentations/configs/google-genai.ts): Only defines configs for generateContentInternal and generateContentStreamInternal. No config for generateImages.
• Channels (js/src/instrumentation/plugins/google-genai-channels.ts): No channel definition for image generation.
• Plugin (js/src/instrumentation/plugins/google-genai-plugin.ts): No handler for image generation calls.
• Vendor types (js/src/vendor-sdk-types/google-genai.ts): GoogleGenAIModels interface only declares generateContent and generateContentStream. No generateImages method.

Upstream reference

• Imagen API docs: https://ai.google.dev/gemini-api/docs/imagen
• SDK method: ai.models.generateImages({ model, prompt, config }) — returns generated image data.
• GA models: imagen-4.0-generate-001, imagen-4.0-ultra-generate-001, imagen-4.0-fast-generate-001.
• Config options: numberOfImages, aspectRatio, imageSize, personGeneration.
• This is a stable, production API — not marked experimental or preview.

Braintrust docs status

The Braintrust Gemini integration page lists generateContent and generateContentStream as supported methods. generateImages / Imagen is not mentioned (not_found).

• https://www.braintrust.dev/docs/integrations/ai-providers/gemini

Precedent in this repo

Image generation instrumentation gaps have been filed for other providers:

• OpenAI images.generate(): OpenAI images.generate() and images.edit() not instrumented (wrapper and auto-instrumentation) #1628
• Vercel AI SDK generateImage(): Vercel AI SDK generateImage not instrumented (wrapper and auto-instrumentation) #1626
• OpenAI Responses API image_generation_call output is already handled with processImagesInOutput converting base64 to Attachment objects — a similar approach could apply here.

Local files inspected

• js/src/wrappers/google-genai.ts
• js/src/auto-instrumentations/configs/google-genai.ts
• js/src/instrumentation/plugins/google-genai-channels.ts
• js/src/instrumentation/plugins/google-genai-plugin.ts
• js/src/vendor-sdk-types/google-genai.ts