Composer 2.5 Bad Request

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Why when I try to use Composer 2.5 do I get this error message: This model does not support custom API keys. Request ID: 75a7ac3e-5499-4f0f-9055-985a9b7a38a7

I am using API keys for OpenAI and Google…thats it.

6

Composer models are Cursor’s own proprietary models, so they don’t work with custom API keys. When you have an OpenAI or Google API key enabled and explicitly select a Composer model, the backend rejects the request with that error.

Two workarounds:

  • Use Auto mode – it automatically routes through Cursor’s infrastructure for Composer models without triggering the error

  • Disable the custom API key in Cursor Settings > Models when you want to use Composer models directly

More details and context in this thread: Bug: Composer 2.5 explicitly selected requests blocked when OpenAI BYOK key is active