fix: thought signature handling in anthropic

[TejasGhatte]

Summary

Improve handling of reasoning messages in Anthropic provider by emitting them immediately rather than collecting and emitting them at the end.

Changes

• Modified convertAnthropicContentBlocksToResponsesMessagesGrouped to emit reasoning messages immediately when encountered instead of collecting and emitting them at the end
• Added proper role assignment to reasoning messages
• Added signature support for reasoning messages in both directions (Anthropic to Bifrost and Bifrost to Anthropic)
• Removed the collection of reasoning blocks in a separate array since they're now emitted inline

Type of change

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

Affected areas

• Core (Go)
• Transports (HTTP)
• Providers/Integrations
• Plugins
• UI (Next.js)
• Docs

How to test

Test the Anthropic provider with models that support reasoning:

# Core/Transports
go version
go test ./core/providers/anthropic/...

Verify that reasoning messages are properly emitted in the correct order and contain the appropriate signature information.

Breaking changes

• Yes
• No

Related issues

Improves message handling for Anthropic models with reasoning capabilities.

Security considerations

No security implications.

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]

Caution

Review failed

The pull request is closed.

📝 Walkthrough

Summary by CodeRabbit

• New Features

  • Reasoning (thinking) blocks now emit as standalone messages immediately, each with a generated identifier and signature.

• Refactor

  • Reasoning messages are emitted independently from text/tool content, changing ordering and grouping.
  • Signature preservation for reasoning content has been improved across conversion and delta flows.
  • Removed legacy compatibility pathway that previously combined reasoning with other blocks.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

Walkthrough

Thinking/reasoning blocks are emitted immediately as standalone reasoning messages (with generated rs_... IDs) containing a Reasoning content block with Text and Signature. The in-memory batching and the Bedrock compatibility path that combined reasoning with text/tool blocks were removed.

Changes

Cohort / File(s)	Summary
Anthropic response processing core/providers/anthropic/responses.go	Emit Thinking blocks immediately as separate reasoning messages (rs_... IDs) containing a Reasoning content block with Text and Signature. Removed in-memory aggregation and Bedrock compatibility branch that previously emitted combined reasoning blocks. Signature propagation added to reasoning content/deltas and Bifrost→Anthropic conversions.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Poem

🐰 I hopped through code with nimble paws,
Reasoning now speaks without a pause,
Signatures snug on every thought,
Messages spring the way they ought,
A rabbit cheers for tidy laws 🥕✨

Pre-merge checks and finishing touches

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'fix: thought signature handling in anthropic' clearly and specifically describes the main change: improving thought/reasoning signature handling in the Anthropic provider.
Description check	✅ Passed	The PR description is comprehensive, covering all major template sections including summary, detailed changes, type of change, affected areas, testing instructions, breaking changes, and checklist completion.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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📜 Recent review details

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between b827d5b and d13d811.

📒 Files selected for processing (1)

• core/providers/anthropic/responses.go

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[github-actions]

🧪 Test Suite Available

This PR can be tested by a repository admin.

Run tests for PR #1162

[TejasGhatte]

• fix: max tokens nil check in bedrock #1167
• fix: thought signature handling in anthropic #1162 👈 (View in Graphite)
• fix: pass reasoning max tokens key to reasoning struct in chat compltion request #1166
• main

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

[Pratham-Mishra04]

Merge activity

• Dec 23, 4:35 PM UTC: A user started a stack merge that includes this pull request via Graphite.
• Dec 23, 4:37 PM UTC: Graphite rebased this pull request as part of a merge.
• Dec 23, 4:38 PM UTC: @Pratham-Mishra04 merged this pull request with Graphite.