Byte-level reasoning models (xiaomi/mimo-v2-pro, kimi, glm) can emit lone
surrogates in reasoning output. The proactive sanitizer walked content/
name/tool_calls but not extra fields like reasoning or the nested
reasoning_details array. Surrogates in those fields survived the
proactive pass, crashed json.dumps() in the OpenAI SDK, and the recovery
block's _sanitize_messages_surrogates(messages) call also didn't check
those fields — so 'found' was False, no retry happened, and after 3
attempts the user saw:
API call failed after 3 retries. 'utf-8' codec can't encode characters
in position N-M: surrogates not allowed
Changes:
- _sanitize_messages_surrogates: walk any extra string fields (reasoning,
reasoning_content, etc.) and recurse into nested dict/list values
(reasoning_details). Mirrors _sanitize_messages_non_ascii coverage
added in PR #10537.
- _sanitize_structure_surrogates: new recursive walker, mirror of
_sanitize_structure_non_ascii but for surrogate recovery.
- UnicodeEncodeError recovery block: also sanitize api_messages,
api_kwargs, and prefill_messages (not just the canonical messages
list — the API-copy carries reasoning_content transformed from
reasoning and that's what the SDK actually serializes). Always
retry on detected surrogate errors, not only when we found
something to strip — gate on error type per PR #10537's pattern.
Tests: extended tests/cli/test_surrogate_sanitization.py with
coverage for reasoning, reasoning_content, reasoning_details (flat
and deeply nested), structure walker, and an integration case that
reproduces the exact api_messages shape that was crashing.
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