[BUG] InlinedResponse missing metadata field - batch API responses don't include request metadata

[imohitkr]

Summary

InlinedResponse is missing the metadata field that is documented in the REST API and present in InlinedRequest. This prevents users from tracking custom identifiers through batch processing. The metadata is accepted when submitting requests but cannot be retrieved from responses.

Environment details

• Programming language: Python
• OS: macOS (also reproducible on Linux)
• Language runtime version: Python 3.12.9
• Package version: google-genai 1.56.0

Steps to reproduce

1. Create a batch job with metadata attached to inline requests:

from google import genai

client = genai.Client(api_key="...")

inline_requests = [
    {
        "contents": [{"parts": [{"text": "Hello"}], "role": "user"}],
        "config": {"temperature": 0.5},
        "metadata": {"request_id": "req-001", "batch_idx": "0"}
    }
]

batch_job = client.batches.create(model="gemini-2.0-flash", src=inline_requests)

2. Wait for batch to complete, then retrieve results:

batch_job = client.batches.get(name=batch_job.name)

for resp in batch_job.dest.inlined_responses:
    print(resp.metadata)  # AttributeError: 'InlinedResponse' object has no attribute 'metadata'

3. Expected: resp.metadata returns {"request_id": "req-001", "batch_idx": "0"}

4. Actual: AttributeError - the metadata field is not defined on InlinedResponse

Additional context

The REST API documentation shows InlinedResponse should include a metadata field:

{
  "metadata": { object },
  "response": { object (GenerateContentResponse) },
  "error": { object (Status) }
}

However, InlinedResponse in types.py only defines response and error. Additionally, _InlinedResponse_from_mldev in batches.py doesn't copy the metadata field from the raw API response.

Note: InlinedRequest correctly includes the metadata field - it's only missing from InlinedResponse.

[janasangeetha]

Hey @imohitkr
Thank you for bringing this to our attention. We truly appreciate you flagging this issue, we will file a bug internally.

[TCatshoek]

Hi @imohitkr, thanks for flagging this issue!

I was dealing with the same thing and was about to open one myself but you beat me to it. The reason I was looking into this is because I was dealing with sporadic request response mismatches and was looking for a way to detect this.