Migrating the GitHub Copilot runtime to Rust, using Copilot
Source
github.blog
Author
Stephen Toub
Date
Context
GitHub's Copilot runtime migration illustrates how AI-assisted rewrites can proceed while a product keeps shipping. The team replaced TypeScript components incrementally with Rust, using temporary connections between the languages and running existing end-to-end tests against each replacement. This kept individual changes reviewable and exposed them to real use throughout the migration. The engineering account identifies a crucial weakness: missing behavioral tests allowed regressions through. It recommends protecting those tests from agents weakening them, so translating the implementation does not also redefine what counts as correct.
Terms in this piece · Glossary
AI agent — An AI system that doesn't just answer once but works toward a goal in a loop — taking actions, reading the results, and deciding what to do next.
