How I Reverse-Engineered Cursor IDE to Run on GitHub Copilot (A Proxy Architecture Deep Dive)

I love Cursor IDE. It is arguably the most advanced AI code editor on the market today. But I hate closed ecosystems. And I absolutely refuse to pay for two AI subscriptions when one should do the job. I already have a GitHub Copilot license. I wanted Cursor’s UI (the Composer, the terminal execution, the MCP tools) to be powered by the Copilot backend I already pay for. But Cursor is a walled garden. If you try to use their "Agent" features with your own API keys, it actively blocks you. It hardcodes its internal router to force models like claude-3.5-sonnet through their proprietary billing backend. So, I decided to build a local Man-in-the-Middle (MITM) proxy. I wanted to trick the smartest IDE in the world into thinking it was talking to its own servers, while secretly tunneling everything to GitHub. Here is the deep technical breakdown of how I reverse-engineered the handshake, bypassed the router, and mutated the Abstract Syntax Trees (AST) in real-time to make it happen. 🏗️ The