fix: strip thinking block if signature is empty

[TejasGhatte]

Summary

StripEmptyThinkingBlocks previously only stripped thinking blocks where the thinking field was empty. This missed a critical cross-provider case: when a thinking block originates from a non-Anthropic upstream (e.g. OpenAI, Gemini), it will have a non-empty thinking field but an empty signature field. Anthropic always emits a signature; OpenAI never does. Replaying such blocks to Anthropic causes a 400 rejection. This PR extends the stripping logic to also remove thinking blocks with an empty signature, and moves the StripEmptyThinkingBlocks call to after all other request body transformations so it applies to the fully-built body.

Changes

• StripEmptyThinkingBlocks now strips thinking blocks where either thinking or signature is empty, covering both the original Anthropic-empty-thinking case and the cross-provider replay case where a signature is absent.
• The StripEmptyThinkingBlocks call was moved from inside the initial marshal block to after all subsequent transformations (tool version remapping, etc.), ensuring it operates on the final request body.
• Tests were added covering: empty thinking + empty signature, non-empty thinking but empty signature (OpenAI/Gemini replay), valid Anthropic blocks, mixed valid/invalid blocks, redacted_thinking blocks (unaffected), multi-message bodies, string content, and bodies with no messages field.

Type of change

• Bug fix
• Feature
• Refactor
• Documentation
• Chore/CI

Affected areas

• Core (Go)
• Transports (HTTP)
• Providers/Integrations
• Plugins
• UI (React)
• Docs

How to test

go test ./core/providers/anthropic/... -run TestStripEmptyThinkingBlocks -v
go test ./...

The new TestStripEmptyThinkingBlocks table-driven test covers all relevant cases. Pay particular attention to the "strips block with non-empty thinking but empty signature (OpenAI/Gemini cross-provider replay)" case, which validates the core fix.

Screenshots/Recordings

N/A

Breaking changes

• No

Related issues

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

Summary by CodeRabbit

• Bug Fixes

  • More consistent removal of empty "thinking" blocks: blocks are now stripped when either the thinking content or its signature is empty, and this cleaning runs for all request payload paths.

• Tests

  • Added comprehensive tests covering multiple request shapes to validate thinking-block filtering behavior.

[coderabbitai]

Caution

Review failed

An error occurred during the review process. Please try again later.

📝 Walkthrough

Walkthrough

StripEmptyThinkingBlocks now removes Anthropic "thinking" blocks when either thinking or signature is empty; the call is moved later in BuildAnthropicResponsesRequestBody so it runs for both raw and typed request bodies. Tests added to validate multiple input shapes and behaviors.

Changes

Anthropic Empty Thinking Block Handling

Layer / File(s)	Summary
Enhanced empty thinking block stripping logic core/providers/anthropic/utils.go	StripEmptyThinkingBlocks now strips thinking blocks when either thinking is empty or signature is empty; docstring updated and deletion flow unchanged.
Request builder pipeline refactoring core/providers/anthropic/requestbuilder.go	The early raw-body StripEmptyThinkingBlocks call was removed and a single StripEmptyThinkingBlocks(jsonBody) invocation was added after raw/typed branches converge, with marshal/error handling at that point.
Comprehensive test suite for thinking block stripping core/providers/anthropic/utils_test.go	TestStripEmptyThinkingBlocks (table-driven) verifies removal when thinking or signature is empty, preservation when both present, non-array content skipping, and unaffected non-thinking block types.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Suggested reviewers

• danpiths
• akshaydeo

Poem

I munch on bytes and hop through code,
I trim blank thoughts where signatures erode,
I moved the snip to where branches meet,
Tests now prove the message is neat,
Hooray — clean payloads, light and stowed 🐇✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change: extending the stripping logic to remove thinking blocks with empty signatures.
Description check	✅ Passed	The description covers all required sections with detailed explanations of the problem, solution, type of change, affected areas, testing instructions, and checklist items.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch 06-05-fix_strip_thinking_block_if_signature_is_empty

Warning

There were issues while running some tools. Please review the errors and either fix the tool's configuration or disable the tool if it's a critical failure.

🔧 golangci-lint (2.12.2)

level=error msg="[linters_context] typechecking error: pattern ./...: directory prefix . does not contain main module or its selected dependencies"

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[TejasGhatte]

• fix: strip thinking block if signature is empty #4079 👈 (View in Graphite)
• fix: remove usage from responses.created event in openai stream #4080
• dev

This stack of pull requests is managed by Graphite. Learn more about stacking.

[greptile-apps]

Confidence Score: 5/5

Safe to merge — targeted, well-tested bug fix with no regressions on existing paths.

The logic change is minimal and correct: extending the strip condition to also check for empty signature precisely matches the failure mode. Moving the call outside the if/else ensures both raw-body and schema-converted paths are covered. The test suite covers all meaningful input states.

No files require special attention.

Important Files Changed

Filename	Overview
core/providers/anthropic/utils.go	Extends StripEmptyThinkingBlocks to also strip thinking blocks with an empty "signature" field, covering the cross-provider replay case.
core/providers/anthropic/requestbuilder.go	Moves StripEmptyThinkingBlocks call to after both raw-body and converted-body branches so it applies uniformly to the final JSON regardless of input path.
core/providers/anthropic/utils_test.go	Adds comprehensive table-driven tests for StripEmptyThinkingBlocks covering all relevant cases including the new empty-signature path.

_{Reviews (2): Last reviewed commit: "fix: strip thinking block if signature i..." | Re-trigger Greptile}

[akshaydeo]

Merge activity

• Jun 5, 1:39 PM UTC: A user started a stack merge that includes this pull request via Graphite.
• Jun 5, 1:41 PM UTC: @akshaydeo merged this pull request with Graphite.