Using OpenAI api issues

Support Bug Reports
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1

Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

I have activated openAPI with key under /Models and now every internal model I try including composer 2.5 is trying to route via that openAI api.

Steps to Reproduce

  1. add openai api key, activate it
  2. try using composer model in chat

Screenshots / Screen Recordings

Screenshot_3.png
Screenshot_3.png2040×1312 79 KB

Operating System

Windows 10/11

Version Information

Version: 3.16.29 (user setup)
VS Code Extension API: 1.128.0
Commit: 6246455961129c32969845e00aa25d87ae926ec0
Date: 2026-08-18T01:26:26.285Z
Layout: Agent Window
Build Type: Stable
Release Track: Default
Electron: 40.10.3
Chromium: 144.0.7559.236
Node.js: 24.15.0
V8: 14.4.258.32-electron.0
xterm.js: 6.1.0-beta.291
OS: Windows_NT x64 10.0.26200

For AI issues: which model did you use?

spark, composer

For AI issues: add Request ID with privacy disabled

Request ID: 57ddb746-9d16-4e24-b2ad-f45d5e53ca40

Does this stop you from using Cursor

Yes - Cursor is unusable

4

Hey, thanks for the detailed report and the request ID. I’ll look into what’s happening. This isn’t a problem with your setup, it’s how BYOK works right now.

When your OpenAI API key is enabled in Settings > Models, Cursor attaches that key to all models except Claude and Gemini, including Cursor-hosted models like Composer 2.5 and Spark. But those models always run on Cursor infrastructure and can’t be billed to a custom key, so the request gets rejected with This model does not support custom API keys. Important: nothing is sent to OpenAI, the request is rejected before the provider is called.

What to do:

  • If you want to use Composer 2.5, Spark, Grok, or other Cursor models, turn off the OpenAI key toggle in Settings > Models. You can keep the key saved and turn it back on when you want to use OpenAI models.
  • As an alternative, use Auto mode. It won’t send BYOK creds when routing to internal models.

We hear you that switching the key on and off is annoying. This is a limitation of the current BYOK implementation, and I’ve shared this feedback with the team. I can’t share an ETA yet.

Let me know if turning off the toggle fixed it.

6

Yes it does work however super inconvenient. Thank you for the quick reply.

7

Hello! any status updates on this, it’s super inconvenient atm

9

Hey, there’s no timeline update yet. Like I mentioned above, this is a current limitation of how BYOK works: when the OpenAI API key toggle is enabled in Settings > Models, that key gets attached to every model except Claude and Gemini, including Cursor-hosted models like Composer 2.5, Spark, and Grok. Those models always run on Cursor infrastructure and can’t be billed to a custom key, so the request gets rejected. Nothing is sent to OpenAI, the request is rejected before the provider is called.

For now, the simplest workaround is:

  • If you need Composer 2.5, Spark, Grok, or other Cursor models, turn off the OpenAI key toggle in Settings > Models. You can keep the key saved and turn it back on when you’re using OpenAI models.
  • Alternatively, use Auto mode. It doesn’t send BYOK creds when routing to internal models.

I know switching the key on and off is annoying. We’re tracking this limitation, but I can’t share an ETA yet. If there’s an update, I’ll reply in this thread.