b5495db701
api_messages is built once before the retry loop while the primary provider
is active. When a mid-conversation fallback switches to a require-side thinking
provider (DeepSeek/Kimi/MiMo), assistant turns built under a non-require primary
(e.g. Codex) go out without reasoning_content and the new provider rejects the
request with HTTP 400 ("reasoning_content must be passed back").
Re-apply the echo-back pad against the current provider immediately before
building the request kwargs. Idempotent and a no-op unless the active provider
enforces echo-back, so it covers all fallback paths without affecting normal or
reject-side operation.
Drafted by Claude (Opus 4.7) under human review while fixing a personal deployment.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>