GitHub and Anthropic used their own agents for major Rust rewrites — with very different playbooks

GitHub fully rewrote the Copilot runtime from TypeScript/Node.js to more than 800,000 lines of Rust using its own Copilot AI agents. The work took about 14.5 weeks and 128 pull requests; Anthropic previously ported Bun from Zig to Rust in 11 days with Claude.

• GitHub rewrote the Copilot runtime into 800,000+ lines of Rust
• The migration took 14.5 weeks and 128 pull requests
• Anthropic ported 535,496 lines of Zig in Bun to Rust in 11 days
• OpenAI rewrote the Habitat service from Python to Rust using Codex