[fix]: Gemini - truncated responses report finishReason MAX_TOKENS instead of OTHER

[AdityaPainuli]

Summary

The IncompleteDetails fallback in ToGeminiResponsesResponse switched on the literal "max_tokens", but IncompleteDetails.Reason never holds that value - the schema constant is "max_output_tokens" and every writer in the codebase mints it. The truncation arm was unreachable, so every truncated response reaching the Gemini egress reported finishReason OTHER instead of MAX_TOKENS, and client keying on MAX_TOKENS (raise limit and retry, truncation UX) misclassified the stop as anomalous failure. Present since the Gemini native converters. (#1018)

Changes

• The switch now matches the schema constants (ResponsesResponseIncompleteReasonMaxOutputTokens → MAX_TOKENS, ResponsesResponseIncompleteReasonContentFilter → SAFETY) so the vocabulary cannot drift again; unknown reasons still fall back to OTHER
• Regression test covering all three arms; the truncation case fails on current dev

Type of change

• Bug fix

Affected areas

• Core (Go)

How to test

cd core && go test ./providers/gemini/ -run TestGeminiIncompleteReasonFinishReason -v

Fails on dev (truncation reports OTHER), passes with the fix. Full ./providers/gemini/ green.

Breaking changes

• No

Related issues

Closes #5978

Security considerations

None.

Checklist

• I read docs/contributing/README.md and followed the guidelines
• I added/updated tests where appropriate
• I updated documentation where needed
• I verified builds succeed (Go and UI)
• I verified the CI pipeline passes locally if applicable

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: 1bebc58f-d4b0-4d2b-b86e-a1ec17ff9408

📥 Commits

Reviewing files that changed from the base of the PR and between 2e91d16 and a4b247a.

📒 Files selected for processing (2)

• core/providers/gemini/incompletefinishreason_test.go
• core/providers/gemini/responses.go

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📝 Walkthrough

Summary by CodeRabbit

• Bug Fixes

  • Improved Gemini response status mapping for truncated outputs and content-filtered responses.
  • Unknown incomplete-response reasons are now categorized consistently.

• Tests

  • Added coverage to verify finish-reason mappings and ensure candidate responses are returned correctly.

Walkthrough

Gemini response conversion now maps max_output_tokens to MAX_TOKENS. It continues to map content filtering to SAFETY and unknown reasons to OTHER. A table-driven test covers all three mappings.

Changes

Gemini finish-reason mapping

Layer / File(s)	Summary
Reason mapping and regression test core/providers/gemini/responses.go, core/providers/gemini/incompletefinishreason_test.go	The converter uses schema constants for incomplete reasons. Table-driven tests verify MAX_TOKENS, SAFETY, and OTHER mappings and confirm that a candidate response is produced.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• maximhq/bifrost#5937: Maps provider-specific incomplete response reasons and adds regression tests for another provider.

Suggested reviewers: tejasghatte, akshaydeo

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the Gemini finish-reason correction for truncated responses.
Description check	✅ Passed	The description covers the purpose, implementation, testing, affected area, issue link, security, breaking changes, and checklist.
Linked Issues check	✅ Passed	The changes satisfy #5978 by mapping max_output_tokens to MAX_TOKENS, preserving content_filter as SAFETY, and retaining OTHER for unknown reasons.
Out of Scope Changes check	✅ Passed	The implementation and regression test are directly related to the linked issue and stated pull request objectives.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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