Rewriting Bun in Rust

This article by Jarred Sumner describes the extensive process of rewriting the Bun runtime from Zig to Rust, driven by persistent memory management bugs like use-after-free and double-free. The rewrite was accomplished in 11 days using advanced AI coding agents (Mythos/Fable) and a TypeScript test suite acting as a conformance suite. The post covers dynamic workflows, adversarial code review, and the philosophy of fixing the code generation process rather than individual bugs. The Rust port is now live in Claude Code, offering 10% faster startup on Linux with minimal user disruption. The article is a detailed technical case study on leveraging LLMs for large-scale software rewrites.