Provider returned error: {“error”:{“message”:“The reasoning_content in the thinking mode must be passed back to the API.”,“type”:“invalid_request_error”,“param”:null,“code”:“invalid_request_error”}}
Steps to Reproduce
set deepseek-v4-pro api.
set deepseek-v4-pro api key.
prompt: Ask him to write a plan proposal document.
Hey, yeah, I’ve seen this issue. DeepSeek V4, same as R1 and Kimi K2.5, requires reasoning_content from previous assistant responses to be sent back to the API in multi-turn requests that include tool calls. On the BYOK path, Cursor currently doesn’t store this field for the DeepSeek API directly, so DeepSeek returns 400.
After integrating deepseek v4 pro into cursor, simple questions can be asked, but asking it to read project code will result in an error. However, integrating v4 pro into TRAE works without any issues.
Steps to Reproduce
After integrating deepseek v4 pro, you will encounter errors when reading project code
Hey, an update on this. We took another look at the case, and we’re not planning to add a built-in fix anytime soon for DeepSeek’s requirement to return reasoning_content when using your own API key BYOK. This is backend behavior of the BYOK proxy, so updating the client won’t change anything here.
If anything changes on DeepSeek’s side, or the proxy stops working, please start a new thread with fresh details Request ID, version, and steps, and we’ll take another look.
