A rewrite of Bun in Rust has been merged, marking a significant architectural shift for the JavaScript and TypeScript runtime. The move brings Bun's core closer to Rust's performance and safety guarantees, replacing components originally written in other languages with Rust-based implementations.

Bun has positioned itself as a faster alternative to Node.js since its launch, and adopting Rust aligns with that performance-first philosophy. Rust offers memory safety without garbage collection, which should reduce overhead in Bun's runtime and improve startup times and throughput for server-side workloads.

Merging a Rust rewrite into production is no small engineering feat. The Rust community's rigorous code review standards and strict ownership model mean the rewritten components have been vetted for correctness and thread safety. For developers already using Bun, the transition should be seamless, but the long-term implications matter more: this deepens the trend of JavaScript tooling embracing systems-level languages for core infrastructure.

With the merge complete, Bun joins a growing wave of runtimes and dev tools betting on Rust for foundational performance gains.