alii13/Antigravity-cursor-proxy — reverse-engineered prompt

Build me a small local proxy I can start with npm that lets Cursor talk to Google Gemini 3 and Claude 4.5 like they are normal OpenAI models. I want it to support the agent style stuff people use in Cursor, including Composer, tool use, and vision, and it should handle the protocol translation in the background so I do not have to mess with it.

It should automatically use my local Google Cloud Code or Antigravity login session, so there is no manual API key setup. When it starts, run a local server and also open a secure HTTPS tunnel, then print a very clear base URL I can paste into Cursor settings. Give me a few easy model choices for Pro, Flash, Sonnet, Opus, and Lite. If the tunnel URL changes, expires, or port 3000 is already in use, show helpful messages that tell me what to do next. Keep the setup simple, basically install then start, and make the terminal output obvious and friendly. Look up current docs online if you need to.