feat(anthropic-adapter): preserve unsigned thinking blocks on MiniMax round-trip

[nagyminyo-cmyk]

Summary

MiniMax's Anthropic-compatible endpoints require unsigned thinking blocks derived from reasoning_content to round-trip in replayed assistant tool-call history. Hermes already synthesizes those blocks, but the generic third-party signature-management path removed them on subsequent turns.

This PR updates _manage_thinking_signatures to reuse the existing _is_minimax_anthropic_endpoint predicate. For both supported MiniMax Anthropic endpoints, Hermes now:

• preserves unsigned thinking blocks synthesized from reasoning_content;
• strips Anthropic-signed thinking blocks that MiniMax cannot validate; and
• continues stripping cache_control from retained thinking blocks through the shared cleanup path.

Azure remains on the generic third-party strip-all path, preventing the broader Bearer-auth matcher from accidentally opting Azure into MiniMax behavior.

Endpoints covered

• https://api.minimax.io/anthropic
• https://api.minimaxi.com/anthropic

Tests

Added direct regression coverage showing that both MiniMax hosts:

• preserve unsigned thinking blocks during replay; and
• strip Anthropic-signed thinking blocks.

The previous MiniMax strip-all assertion was replaced with an Azure negative case.

Validation completed:

• scripts/run_tests.sh -j 2 tests/agent/test_minimax_anthropic_thinking.py tests/agent/test_deepseek_anthropic_thinking.py — 13 passed
• ruff check agent/anthropic_adapter.py tests/agent/test_deepseek_anthropic_thinking.py tests/agent/test_minimax_anthropic_thinking.py — passed
• python -m py_compile agent/anthropic_adapter.py tests/agent/test_deepseek_anthropic_thinking.py tests/agent/test_minimax_anthropic_thinking.py — passed

Review note

The branch has been rebased onto current main. The upstream CI workflow is awaiting maintainer approval before jobs can start.

[teknium1]

Thanks for identifying the MiniMax replay path. Current main still strips its unsigned thinking blocks, but this stale patch needs a narrow rework before salvage.

Problems

• agent/anthropic_adapter.py:557-569 already defines _is_minimax_anthropic_endpoint; the PR adds the same symbol, so it will conflict on current main.
• The PR’s proposed _requires_bearer_auth delegation is now too broad: that matcher also recognizes Azure at agent/anthropic_adapter.py:531-546. The existing MiniMax-only helper should remain the predicate.
• No regression test accompanies the change. Current tests/agent/test_deepseek_anthropic_thinking.py:210-241 explicitly expects MiniMax to strip unsigned blocks, so the changed provider contract needs direct coverage.

Suggested changes

• Reuse the existing MiniMax-only helper in the preserve gate at agent/anthropic_adapter.py:2275-2278.
• Add tests for both MiniMax hosts preserving unsigned blocks while stripping signed blocks, and retain a negative Azure case.

Automated hermes-sweeper review.

[nagyminyo-cmyk]

Thanks for the detailed review. You're right that the branch is stale. I'll rework it against current main, reuse the existing MiniMax-only helper in the preserve gate, and add regression coverage for both MiniMax hosts plus a negative Azure case before requesting another review.

[nagyminyo-cmyk]

Reworked and pushed in 04aab9700. The branch is now rebased on current main, reuses the existing MiniMax-only endpoint helper, preserves unsigned and strips signed thinking blocks for both MiniMax hosts, and keeps Azure on the generic strip-all path. The repository’s canonical focused test run passes all 13 tests, and Ruff plus py_compile pass. CI is currently awaiting maintainer approval to start. Could you take another look when convenient?