Requests are sent to incorrect endpoint when using base URL override

Hey everyone, and thanks for your patience. I know this has taken longer than expected.

Can you double check on the latest version of Cursor if the issue still repros? If requests with “Override OpenAI Base URL” + an OpenAI API Key are still failing with missing_required_parameter: 'messages', please send:

  • the model you selected (GPT-4x / GPT-5x)
  • the Request ID from the error (with Privacy Mode turned off)

That way I can verify the current status using fresh data.

@kx_w about user-agent based routing, yep, you’re on the right track. As a temporary workaround, you can set up a proxy that accepts a Response API payload on the chat/completions endpoint and converts it to the right format. This was discussed here: Cursor is sending Response API requests to Chat Completion API - #3 by Greendam_Lyngo. Cursor can’t distinguish it from its side, but the proxy can.

I’ll follow up in the thread once I have something concrete.