Pragmatic Engineer· 11 min read· Jul 16, 2026
The Pulse: What can we learn from Bun’s rapid Rust rewrite with AI?
The creator of JavaScript runtime Bun, Jarred Sumner, has rewritten the project from Zig to Rust using the tool Fable, eliminating memory-related bugs and improving stability. Bun is a complex project with 22 million monthly downloads, and its dependencies include software like Claude Code and hosting providers like Vercel. The rewrite was necessary due to Zig's lack of memory safety, which caused continuous memory leaks and crashes. Rust's memory-safe features, such as compiler errors and automatic cleanup with Drop, have improved the project's stability. The use of Fable has made the rewrite process significantly faster than traditional methods.
