GitHub used Copilot agents to migrate the Copilot runtime from TypeScript to 830K lines of Rust

GitHub 用 Copilot 智能体将 Copilot 运行时从 TypeScript 迁移到 83 万行 Rust

GitHub engineers used Copilot's agent mode to migrate the core Copilot runtime from TypeScript to Rust, producing roughly 830K lines of code. The migration ran in three phases: file-by-file translation by agents, test-driven bug fixing, and performance/security review. After migration, service startup dropped from 30s to 3s, memory usage fell to one-third, and time-to-first-token went from 11s to 1.2s. The team stresses that humans stayed in the loop—agents did the heavy lifting, engineers owned architecture, code review, and test coverage. The post doesn't spell out exact cost savings but states the migration was done 'with a smaller team in less time.'

Why it matters: First-party case study from GitHub: a Copilot agent drove an 830K-line Rust migration with hard performance gains. HKR all hit, but it's a product capability showcase rather than an independent breakthrough, so capped at 82 in the featured tier.