IDEAS, DECISIONS & LESSONS

Journal

Notes on AI, architecture and building useful products.

2 articles

10 Oct 2026 · 5 min read

developer-tools

GitHub Rewrote the Copilot Runtime in Rust. The Interesting Part Is How Slowly They Did It.

GitHub ported its Copilot language-server runtime from Node.js to Rust over roughly 128 pull requests. The incremental path, not the language choice, is the part worth studying.

21 Sep 2026 · 6 min read

agents

One Engineer, 832,000 Lines of Rust, 14.5 Weeks — What GitHub's Copilot Rewrite Actually Teaches

GitHub let Copilot rewrite its own runtime from TypeScript to Rust: 832K lines, 128 PRs, 135 releases, one human in the loop. The regression taxonomy and the incident where two agent sessions overruled each other are worth more than the headline number.