Hey, thanks for the report with the Request ID. I can see the error in the screenshot, This model does not support custom API keys. Let’s figure out what’s going on.
Grok 4.6 and Composer 2.5 are Cursor-hosted models. They always run on Cursor’s infrastructure and can’t be used with a personal API key. When you add a custom model like qwen3.8-max, the OpenAI API Key toggle becomes available, and right now that key gets attached to every model except Claude and Gemini, including Grok and Composer. The server rejects those requests. This doesn’t affect your included usage.
For now, the workaround is to turn the toggle off when you want Grok or Composer:
- Open Cursor Settings > Models.
- In the OpenAI API Key section, turn the toggle off. You can leave the key and Base URL filled in.
- Go back to chat and select Grok 4.6 or Composer 2.5. They should work again.
- When you need
qwen3.8-maxagain, turn the toggle back on.
Auto mode still works with the key enabled, since Auto never sends your personal key.
I know switching the toggle back and forth is annoying. We’re tracking a fix so Cursor-hosted models automatically ignore the custom key. I’ve shared your case with the team. I can’t promise a timeline yet, but I’ll reply in the thread if there’s an update.