Hey, thanks for the report.
Could you please check the following:
- Settings > Models > API Keys: turn off Override OpenAI Base URL, and temporarily disable custom keys if they’re enabled. This is a known issue. Details here: API Keys for ChatGPT and Anthropic Failing
- Settings > MCP: disable all MCP servers and restart Cursor. A workaround is described here: "error_bad_request
- Create a brand new chat and try again there. For a few users, starting a new thread helped: Always show the error:Bad Request
If it still doesn’t work, please send:
- screenshots of Settings > MCP and Settings > Models > API Keys
- a new Request ID after the steps above
- errors from Help > Toggle Developer Tools > Console
- the result of Settings > Network > Run Diagnostics
Let me know which step worked.