400 error: reasoning_content must be passed back for DeepSeek-family models on direct OpenAI-compatible endpoints #815

Problem

Multi-turn sessions against DeepSeek-family models served by direct OpenAI-compatible profiles (no OpenRouter provider features — e.g. OpenCode Zen, opencode.ai/zen/v1) fail on the second request with:

400 The `reasoning_content` in the thinking mode must be passed back to the API.

The endpoint runs server-managed thinking mode and requires the assistant reasoning_content to be replayed on follow-up requests. jcode stores it (stores_reasoning_content_for_context) but drops it at request-build time for these profiles, because reasoning passback is only unlocked when OpenRouter provider features are enabled or the endpoint is the Kimi coding endpoint (#322).

Repro

• Any model in the DeepSeek family (e.g. deepseek-v4-flash-free on OpenCode Zen) via a direct OpenAI-compatible profile
• Start a session, let the model emit a tool call (which carries a stored reasoning block), then send a follow-up request
• 400 error above

Workaround (verified): set allow_provider_pinning = true on the named profile so provider features are treated as enabled, which unlocks the reasoning passback path.

Related

• Kimi API fails with tool calls when thinking mode is enabled #322 — same mechanism for the Kimi coding endpoint (fixed)
• After jcode is actually doing something, gets interrupted, and then executes another task, it returns a 400 error #321, Deepseek models: deepseek-ai/deepseek-v4-flash, deepseek-ai/deepseek-v4-pro for Nvidia Nim provider not working #341 — neighboring DeepSeek/Kimi thinking-mode 400s