Using Cursor Frontier Models like Composer 2.5 in External Harnesses (e.g. Codex)

Support Help
1

Hi, I have a question regarding the Cursor subscription.

I’d like to use frontier models from Cursor, such as Composer 2.5, inside other harnesses like Codex. To experiment with this, I’ve already built a proxy that allows Cursor’s Composer models to be used from external harnesses such as Codex.

However, I’m not sure whether this approach violates Cursor’s Terms of Service or any usage policies, so I’d like to confirm whether this is allowed.

  1. Is it permitted, under Cursor’s policies, to use subscription models like Composer 2.5 outside of the Cursor IDE (for example, in another harness such as Codex)?
  2. If it is allowed, is there any officially supported API or recommended method for using Cursor models in external tools?
  3. Would using an unofficial proxy like the one I’ve built be considered a violation or otherwise problematic?

I’m planning to subscribe to Cursor based on whether this kind of usage is permitted, so I would really appreciate some clarification.

Thank you.

5

Hey, I’ll answer point by point.

  1. Using subscription models like Composer 2.5 outside Cursor via your own proxy, no, you can’t do that. That kind of proxy calls our private, non public client endpoints, and that goes against the Use Restrictions in the Terms of Service, especially reverse engineering and accessing internal service structure. Also, using a subscription outside official clients can trigger abuse enforcement and may get your account banned.

  2. The official way to use our agent outside the IDE is Cursor CLI cursor-agent and the Agent SDK. They let you run the Cursor agent programmatically, including choosing a model, like Composer. Links:

Important detail: the CLI and SDK always run the Cursor agent harness. They don’t give you the raw model. We don’t currently have an OpenAI compatible /v1/chat/completions endpoint that you can point an external harness like Codex at. There’s a feature request for this, but it’s not a product yet.

  1. Yes, an unofficial proxy is exactly what you shouldn’t do, see point 1. If you want automation outside the IDE, use the CLI or SDK, that’s the supported and safe path.

If you’re planning a workflow around the CLI or SDK and something doesn’t line up, tell me and I’ll help.