If you already have a Claude or ChatGPT subscription, using those models in Cursor usually means paying twice: once for the subscription and once for API tokens. Subscriptions don’t provide an API endpoint, and Cursor routes requests through its own backend, so a plain localhost proxy doesn’t work.
I made an open-source Cursor extension called Ungate to bridge this gap. You log in via OAuth in your browser, and the extension runs a local proxy with an automatic Cloudflare tunnel. Setup takes about a minute, and you can switch between Claude and ChatGPT inside the same chat. A $20 ChatGPT subscription covers roughly $1,000 of API tokens, while $100 for Claude covers about $2,000.
I wrote a detailed guide covering the setup, limits, and common fixes: How to use Claude and ChatGPT subscriptions in Cursor instead of paying for API tokens - DEV Community
The extension is open source: