Microsoft Agentically Ports Copilot Runtime to Rust for $120K

Microsoft ported the GitHub Copilot runtime from TypeScript to Rust, delegating the main work to AI agents. The migration cost about $120K in tokens and three weeks of developer work, took 14.5 weeks and 135 releases. Agents converted 430K lines of TypeScript to 800K lines of Rust, speeding up the runtime up to 15.9 times.

• 430K lines of TypeScript turned into 800K lines of Rust
• Speedup up to 15.9x: 120 vs 7.55 lifecycles per second
• Memory reduced from 1383 MB to 126 MB per 10 clients
• Dozens of regressions remained in the code and had to be fixed