The gateway's thinking-block handling was designed for Anthropic's strict
semantics (drop blocks with missing/invalid signature), but third-party
Anthropic-compatible upstreams have INVERTED semantics:
* DeepSeek `/anthropic`, Kimi `/coding`, GLM, Moonshot, qwen-*-thinking
require ALL historical thinking blocks to round-trip verbatim.
* Stripping any of them produces:
400 "The content[].thinking in the thinking mode must be passed back
to the API"
Without this fix, every multi-turn request from a thinking-capable client
(Claude Code, pi, etc.) to such upstreams loses its thinking blocks and
fails. This becomes especially painful when an account's model_mapping
maps `claude-sonnet-4-6 → deepseek-v4-pro` — `reqModel` looks Anthropic
but the upstream contract is the opposite.
Approach
--------
Branch all thinking-block transforms by the *mapped* model id (after
account model_mapping is applied), classifying into three families:
* `anthropic-strict` claude-/opus-/sonnet-/haiku- → existing behaviour
* `passback-required` deepseek-/kimi-/moonshot-/glm-/ → preserve verbatim
qwen-*-thinking
* `unknown` other models → conservative
(preserve, no retry)
Affected entry points (all guarded):
* Pre-filter on outbound: `FilterThinkingBlocks`
Previously dropped blocks with missing/invalid signature; now skips
entirely for non-strict families. Pre-filter is needed because the
post-error retry path can run out of budget on long conversations
(maxRetryElapsed = 10 s).
* 400 retry rectifier: `FilterThinkingBlocksForRetry`
Disables top-level thinking and converts thinking → text. Now skips
for passback-required (those 400s aren't signature errors and any
transformation breaks the round-trip contract).
* 400 retry rectifier (tools): `FilterSignatureSensitiveBlocksForRetry`
Same family-aware short-circuit.
* 400 detector: `shouldRectifySignatureError`
Returns false for passback-required, so the retry path doesn't even
fire.
Tests
-----
* `thinking_protocol_test.go` — classifier across all known vendor
prefixes plus edge cases (empty, case, qwen non-thinking).
* `thinking_protocol_filter_integration_test.go` — locks in that the
three filter entry points return the body byte-for-byte unchanged
when the model id is passback-required or unknown, and still strip
invalid blocks for anthropic-strict.
This PR supersedes #1350 (which only added the pre-filter without the
upstream-family awareness, and would have made third-party upstreams
worse). Once merged, please close#1350.
Reference issues:
- NousResearch/hermes-agent#16748 — DeepSeek /anthropic strip behaviour
- NousResearch/hermes-agent#15700 — DeepSeek thinking:disabled requirement
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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