_manage_thinking_signatures treated every Kimi-family endpoint with the
#13848-era contract: strip signed Anthropic thinking blocks from replayed
history, assuming the upstream cannot validate Anthropic signatures.
Live probing shows that contract is outdated for the whole Kimi family:
- Kimi For Coding (api.kimi.com/coding) issues AND validates its own
thinking signatures (K3+): both verbatim and content-mutated signed
blocks replay with HTTP 200;
- Moonshot's Anthropic surface (api.moonshot.cn/anthropic) accepts signed
blocks the same way (200 on both verbatim and mutated);
- every other harness that replays signed blocks to KFC (Claude Code, pi,
Kilo Code) round-trips fine.
Stripping signed blocks there silently discarded the model's prior
chain-of-thought in multi-turn conversations — e.g. a two-turn recall
probe loses the reasoning between turns while the text answer survives
(agent.log: turn-2 input ≈ turn-1 input + a few dozen tokens instead of
+thinking). With this change, the same probe recalls the exact hidden
values from turn-1 thinking (+230 tokens on turn 2).
So: on _is_kimi_family_endpoint, keep signed and unsigned thinking blocks
unchanged on replay — one uniform rule for the whole Kimi family, no
/coding-vs-Moonshot split. DeepSeek keeps the #16748 contract (strip
signed, preserve unsigned). Third-party and direct-Anthropic behavior is
untouched.
Add tests/agent/test_anthropic_kimi_signed_thinking_replay.py pinning the
unified behavior (Kimi /coding + Moonshot keep signed and unsigned) and
the unchanged neighbors (DeepSeek strips, direct Anthropic keeps).
fanyu
ddd81e9352