Bun Rewrites from Zig to Rust — Why a Fast Runtime Is Starting Over | StartupXO

Zig was a deliberate choice in 2022. Its comptime evaluation and zero-runtime design minimized overhead when calling JavaScriptCore’s C++ interfaces. But Zig’s ecosystem remains narrow: no central package registry comparable to crates.io, a small hiring pool, and slow open-source contributor growth.

Rust is now the practical standard for systems programming. AWS Firecracker, Cloudflare’s Workers runtime (workerd), and Linux kernel drivers are built in Rust. The White House ONCD and NSA have formally recommended Rust for memory safety. As of 2026, choosing Rust means choosing a contributor pool orders of magnitude larger than Zig’s.

Bun’s Rust move is about ecosystem integration, not raw performance gains. More contributors, better security tooling, and more hireable engineers.