Hey, this is a known bug with BYOK for DeepSeek v4. In multi-turn requests with tool calls like reading project files, the reasoning_content field isn’t passed back to the API, so the provider rejects the request. Simple questions without tool calls work, but anything that needs reading code fails.
We’re tracking the issue, but there’s no ETA for a fix yet. The main discussion and updates are here: The deepseek-v4-pro api cannot be used normally. Subscribe to the thread to get notified when there’s news. I’m going to close this as a duplicate.