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Retry instead of error when Google response is empty with MALFORMED_FUNCTION_CALL or other recoverable finish reason #3300

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Merged
merged 8 commits into from
Oct 31, 2025
Merged

Retry instead of error when Google response is empty with MALFORMED_FUNCTION_CALL or other recoverable finish reason #3300

merged 8 commits into from
Oct 31, 2025

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@ArneZsng
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@ArneZsng ArneZsng commented Oct 30, 2025 •
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Reopening #3095

Original Description

Using Gemini, we are frequently running into the MALFORMED_FUNCTION_CALL as the finish reason.
Google seemingly does not provide any context in the response for the reason of the MALFORMED_FUNCTION_CALL.

In these cases, the agent can continue retrying which I why I suggest to simply continue in the case of a MALFORMED_FUNCTION_CALL.

Closes #631

The issue is most prevalent when using Gemini 2.5 Flash (compared to Gemini 2.5 Pro where it also happens but less frequently).

Example chunk:

sdk_http_response=HttpResponse(
  headers=<dict len=11>
) candidates=[Candidate(
  finish_reason=<FinishReason.MALFORMED_FUNCTION_CALL: 'MALFORMED_FUNCTION_CALL'>,
  index=0
)] create_time=None model_version=None prompt_feedback=None response_id=None usage_metadata=GenerateContentResponseUsageMetadata(
  prompt_token_count=2595,
  prompt_tokens_details=[
    ModalityTokenCount(
      modality=<MediaModality.TEXT: 'TEXT'>,
      token_count=2595
    ),
  ],
  total_token_count=2595
) automatic_function_calling_history=None parsed=None

Newly added changes

Refactored Gemini response handling in GoogleModel and GeminiStreamedResponse to treat missing or malformed function call content uniformly, avoiding unnecessary exceptions.

@ArneZsng
Update google.py
6166f3d
@ArneZsng
Add tests for Gemini MALFORMED_FUNCTION_CALL error
86b3cf3
@ArneZsng
Handle MALFORMED_FUNCTION_CALL in GoogleModel and add tests
2997f66 
Updated GoogleModel to handle 'MALFORMED_FUNCTION_CALL' finish reason by initializing parts as an empty list. Added and extended tests to cover retry logic for both streaming and non-streaming responses when a malformed function call is encountered.
@ArneZsng ArneZsng marked this pull request as draft October 30, 2025 21:02
@ArneZsng ArneZsng force-pushed the fix/google-continue-on-malformed-function-call branch from 168bc8d to 2997f66 Compare October 30, 2025 21:13
DouweM
DouweM requested changes Oct 30, 2025
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@DouweM DouweM self-assigned this Oct 30, 2025
@ArneZsng
Simplify Gemini response handling and remove unused tests
a68b631 
Refactored Gemini response handling in GoogleModel and GeminiStreamedResponse to treat missing or malformed function call content uniformly, avoiding unnecessary exceptions. Removed obsolete or redundant test helpers and tests related to malformed function call streaming and retry logic.
@ArneZsng
Update test assertions in test_google.py
25e971d 
Removed a redundant PartDeltaEvent assertion and updated the expected identifier in the BinaryImage snapshot assertion to 'b037a4' in the image generation test.
@ArneZsng ArneZsng changed the title Google: Continue on MALFORMED_FUNCTION_CALL Google: Continue on MALFORMED_FUNCTION_CALL and other errors and empty response Oct 30, 2025
DouweM
DouweM requested changes Oct 30, 2025
View reviewed changes
pydantic_ai_slim/pydantic_ai/models/google.py
)
continue

parts = candidate.content.parts
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Note that we could get here if candidate.content is None

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@ArneZsng ArneZsng Oct 30, 2025

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Wouldn't that call continue and thus let us proceed with the next chunk? I am not sure I can follow you right now.

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You're quite right, I think I had been at my desk for too long when I reviewed this :)

pydantic_ai_slim/pydantic_ai/models/google.py
parts = candidate.content.parts or []
parts = []
else:
parts = candidate.content.parts or []
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Note that we could get here if candidate.content is None

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@ArneZsng ArneZsng Oct 30, 2025

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If candidate.content is None, parts would be [] and we would continue with that, no?

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Ah, you're totally right, I wasn't reading right

@ArneZsng ArneZsng marked this pull request as ready for review October 30, 2025 22:08
@ArneZsng
Add coverage pragma to empty parts assignment
bd61d88 
Marked the assignment of an empty list to 'parts' with 'pragma: no cover' to exclude it from test coverage analysis, as this branch is likely not expected to be covered.
@ArneZsng
Merge branch 'main' into fix/google-continue-on-malformed-function-call
2c14f87
@ArneZsng ArneZsng requested a review from DouweM October 30, 2025 23:38
DouweM
DouweM approved these changes Oct 31, 2025
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pydantic_ai_slim/pydantic_ai/models/google.py
parts = candidate.content.parts or []
parts = []
else:
parts = candidate.content.parts or []
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@DouweM DouweM Oct 31, 2025

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Ah, you're totally right, I wasn't reading right

pydantic_ai_slim/pydantic_ai/models/google.py
)
continue

parts = candidate.content.parts
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@DouweM DouweM Oct 31, 2025

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You're quite right, I think I had been at my desk for too long when I reviewed this :)

@DouweM DouweM changed the title Google: Continue on MALFORMED_FUNCTION_CALL and other errors and empty response Retry instead of error when Google response fails with MALFORMED_FUNCTION_CALL or other recoverable finish reason Oct 31, 2025
@DouweM DouweM changed the title Retry instead of error when Google response fails with MALFORMED_FUNCTION_CALL or other recoverable finish reason Retry instead of error when Google response is empty with MALFORMED_FUNCTION_CALL or other recoverable finish reason Oct 31, 2025
@DouweM DouweM merged commit 1f3b100 into pydantic:main Oct 31, 2025
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@amiyapatanaik amiyapatanaik mentioned this pull request Nov 3, 2025
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MALFORMED_FUNCTION finishReason in Gemini candidate

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