Hey, this is a known limitation for BYOK with DeepSeek V4 and Kimi in thinking mode. Cursor currently doesn’t pass reasoning_content back in a multi-turn flow with tool calls, so the provider rejects the follow-up request. One tool call usually works, and the second step fails with the same 400.
Megathread on this: Compatibility with DeepSeek model’s design to return reasoning content after tool calls? Compatibility with DeepSeek model's design to return reasoning content after tool calls?
I’ll close your thread as a duplicate so the discussion stays in one place.
We’ve reported the issue internally, but I can’t share an ETA for a fix yet. We’ll post updates in the megathread.