Xubin Ren 7f1913f619 fix(provider): add DeepSeek thinking toggle; backfill reasoning_content on legacy messages
Two issues with DeepSeek V4 thinking mode support:

1. Missing thinking parameter injection.
   DeepSeek V4 requires `extra_body: {"thinking": {"type": "enabled/disabled"}}`
   — identical to VolcEngine/BytePlus. The code had this for volcengine,
   byteplus, dashscope, minimax, and kimi but not DeepSeek. This means
   `reasoning_effort=minimal` (thinking off) silently has no effect.

   Root cause: the thinking-style→wire-format mapping was an if/elif chain
   on provider *names*. DeepSeek was forgotten.

   Fix: make the mapping declarative via `ProviderSpec.thinking_style`:
   - "thinking_type" → {"thinking": {"type": "..."}} (DeepSeek, Volc, BytePlus)
   - "enable_thinking" → {"enable_thinking": bool} (DashScope)
   - "reasoning_split" → {"reasoning_split": bool} (MiniMax)
   `_build_kwargs` now does a single dict lookup. Adding a new provider
   with an existing wire format requires zero changes to the function.

2. Legacy session messages crash thinking-mode requests.
   When a session was started without thinking mode (or with a different
   model), assistant messages lack reasoning_content. DeepSeek V4 in
   thinking mode rejects these with 400:
   "The reasoning_content in the thinking mode must be passed back to the API."
   This affects ALL assistant messages, not just those with tool_calls
   (despite the docs only mentioning the tool_calls case).

   Fix: `_build_kwargs` backfills `reasoning_content: ""` on every
   assistant message missing it, but only when thinking mode is active.
   This is semantically neutral — the model treats empty reasoning_content
   as "no thinking happened on that turn". The backfill only touches the
   in-memory request copy; session files on disk are untouched.

Tests: +5 (3 thinking toggle, 2 backfill). Full suite: 2377 passed.
Made-with: Cursor
2026-04-24 15:06:39 +08:00
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