[BOT ISSUE] Google GenAI (Gemini) streaming calls are not instrumented

Bắt đầu với BraintrustApiClient.java ở các dòng 186–312 và kiểm tra các phương thức streaming của ApiClient upstream được generateContentStream sử dụng. So sánh cách xử lý SSE và việc tích lũy các chunk trong các triển khai TracingHttpClient của OpenAI và Anthropic, sau đó xem lại BraintrustGenAITest.java. Hoàn tất nghĩa là các lệnh gọi Gemini streaming tạo ra spans, thu thập đầu ra và các chỉ số sử dụng token.

Summary

The Google GenAI instrumentation wraps ApiClient.request() and ApiClient.asyncRequest() for synchronous and asynchronous non-streaming calls, but does not override any streaming methods. Calls to client.models.generateContentStream() and similar streaming APIs bypass the instrumentation entirely, producing no spans, no output capture, and no token usage metrics.

What is missing

BraintrustApiClient.java overrides 4 methods:

• request(String, String, String, Optional) (line 186)
• request(String, String, byte[], Optional) (line 210)
• asyncRequest(String, String, String, Optional) (line 239)
• asyncRequest(String, String, byte[], Optional) (line 277)

The upstream ApiClient class in the Google GenAI SDK also has streaming request methods (used internally by generateContentStream) that are not overridden. This means streaming Gemini calls — a common pattern for chat applications — are completely invisible to Braintrust tracing.

For comparison, both the OpenAI and Anthropic instrumentations in this repo handle streaming via SSE detection and chunk accumulation in their respective TracingHttpClient implementations.

Upstream sources

• Google GenAI Java SDK: https://github.com/googleapis/java-genai — streaming is a core feature, with generateContentStream available since early versions. The SDK is now at v1.46.0 (this repo pins to v1.18.0).
• Gemini API streaming docs: https://ai.google.dev/gemini-api/docs/text-generation#generate-a-text-stream

Braintrust docs status

• not_found — braintrust.dev/docs does not reference Google GenAI streaming instrumentation for Java. The Java SDK docs page redirects to the GitHub repo.

Local files inspected

• braintrust-sdk/instrumentation/genai_1_18_0/src/main/java/com/google/genai/BraintrustApiClient.java — lines 186–312 (only non-streaming request/asyncRequest overridden; no streaming method override)
• braintrust-sdk/instrumentation/genai_1_18_0/src/main/java/com/google/genai/BraintrustInstrumentation.java — wraps ApiClient in Client and service fields, no streaming awareness
• braintrust-sdk/instrumentation/genai_1_18_0/src/main/java/dev/braintrust/instrumentation/genai/v1_18_0/BraintrustGenAI.java — thin wrapper, delegates to BraintrustInstrumentation
• braintrust-sdk/instrumentation/genai_1_18_0/src/test/java/dev/braintrust/instrumentation/genai/v1_18_0/BraintrustGenAITest.java — only tests sync and async non-streaming; no streaming tests exist