Where does the bug appear (feature/product)? Cursor IDE Describe the Bug Can not use Cursor’s proprietary models with activated API keys for other vendors. I expect the reply to this report may follow the template used on that thread, roughly: Composer 2 is a Cursor proprietary model, so it won’…

Hey, thanks for the detailed report, and yep, you’re right. A generic “by design” answer doesn’t fit here, because you’re talking about routing logic, not whether Composer 2 can run on the OpenAI endpoint. Confirmed on the substance: The current behavior is a routing choice, not a technical limit…

"Bad request: This model does not support custom APIs" when using Composer 2 with an OpenAI key configured

Support Bug Reports

Topic		Replies	Views
Composer 2 broken when custom OpenAI API Key is enabled Bug Reports byok , openai , composer	10	588	June 16, 2026
Bug: Composer 2.5 explicitly selected requests blocked when OpenAI BYOK key is active Bug Reports byok , openai , composer , linear-linked	7	185	July 3, 2026
Composer 2.5 fails with BYOK Bug Reports byok , composer , linear-linked	4	95	July 3, 2026
First Calss support for Openrouter (BYOK feature for Premium Members) Feature Requests byok , openai , composer	2	269	May 25, 2026
Composer 2.5 error "This model does not support custom API keys" Bug Reports byok , composer	2	145	June 16, 2026

"Bad request: This model does not support custom APIs" when using Composer 2 with an OpenAI key configured

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