Fix gpt-oss tool call

[sa411022]

Purpose

Fix gpt-oss tool call when Pydantic validates the function call message as dict

Test Plan

Test Result

(Optional) Documentation Update

[gemini-code-assist]

Code Review

This pull request addresses a bug where a tool call from gpt-oss is validated as a dictionary instead of a ResponseFunctionToolCall object. The fix involves adding an elif block to check if the message is a dictionary representing a function call and, if so, converting it into the proper ResponseFunctionToolCall object. This change is crucial for the subsequent logic that needs to find this specific object type to correctly process tool call outputs. The implementation is direct, correct, and safely resolves the issue described in the pull request description.

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[heheda12345]

Can you add a test in https://github.com/vllm-project/vllm/blob/main/tests/entrypoints/openai/test_response_api_with_harmony.py and test it locally?

[sa411022]

@heheda12345

I found the root cause is that some clients (such as LangChain) do not include the status field in the input function_call message.
If status field exists (even if its value is null), the message will be validated as ResponseFunctionToolCall correctly.
On the other hand, if status field does not exists, the message will be validated as dict and thus it will not be appended to the prev_outputs, which cause the "No call message found for call_xxx" error.

However, I am not sure if this should be fixed on the server side (vLLM) or the client side (such as LangChain)?

[sa411022]

#22578 (comment)

[heheda12345]

Would be great if you can parse it correctly in vLLM. My suspicion is ResponseFunctionToolCall is not a standard ResponseInputItemParam so the below hack may have some problem.

ResponseInputOutputItem: TypeAlias = Union[ResponseInputItemParam,
                                           ResponseReasoningItem,
                                           ResponseFunctionToolCall]
class ResponsesRequest(OpenAIBaseModel):
    ....
    input: Union[str, list[ResponseInputOutputItem]]

[heheda12345]

FYI #24158 has a fix.

[github-actions]

This pull request has been automatically marked as stale because it has not had any activity within 90 days. It will be automatically closed if no further activity occurs within 30 days. Leave a comment if you feel this pull request should remain open. Thank you!

[mergify]

Hi @sa411022, the pre-commit checks have failed. Please run:

uv pip install pre-commit
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pre-commit run --all-files

Then, commit the changes and push to your branch.

For future commits, pre-commit will run automatically on changed files before each commit.

[hmellor]

Thanks for investigating this bug! As noted by @heheda12345 in the review, #24158 contains the proper fix for this issue. Closing as superseded.