Rewriting Bun in Rust

This article by Jarred Sumner describes the ambitious rewrite of the Bun JavaScript runtime from Zig to Rust, accomplished in 11 days with the help of AI coding agents. It explains the motivation behind the switch, primarily memory safety issues like use-after-free and double-free errors that plagued the Zig version. The post details how a TypeScript test suite served as a conformance suite, enabling automated porting via an agent harness. It covers the engineering workflow, including adversarial code review and process-level fixes, and notes that the Rust port is now live in Claude Code, with minimal user-visible changes.