GitHub rewrites Copilot runtime in 800,000 lines of Rust using AI agents; single developer completes year-long project in months, improves performance by orders of magnitude.

Migrating the GitHub Copilot runtime to Rust, using Copilot

The GitHub Copilot CLI, GitHub Copilot app, and GitHub Copilot SDK are all backed by the Copilot agent runtime, an agentic harness that can be embedded into applications and services. It was originally written in TypeScript on Node.js and the V8 JavaScript engine for what is now the GitHub Copilot cloud agent (CCA), and the runtime stayed on that stack as the runtime and its capabilities grew rapidly. That has now changed. Using the GitHub Copilot app and the Copilot CLI, we completely rewrote t...