A core component of GitHub's AI assistant tool has been migrated to the Rust programming language to improve performance. Engineers used the GitHub Copilot app to rewrite more than 800,000 lines of code across 128 pull requests, running existing end-to-end tests against the new code at every step. The transition to the new agent runtime was executed incrementally to maintain functionality during the port.

The project focused on the runtime responsible for executing tasks within the Copilot ecosystem and provides a direct performance impact. Stephen Toub detailed the technical approach to the rewrite to demonstrate the scale of ambitious projects now possible through agent-assisted refactoring.