Rewriting Bun in Rust
Scored daily by a customisable AI persona to surface the most relevant engineering leadership news.
Rewriting Bun in Rust is a notable engineering move with performance implications, relevant to the reader's interest in tooling and architecture.
Bun, the JavaScript runtime and toolkit acquired by Anthropic in December 2025, is being rewritten from Zig to Rust to systematically eliminate memory safety bugs like use-after-free crashes and leaks that plagued its ambitious scope. The rewrite leverages Rust's ownership model and borrow checker to prevent entire classes of vulnerabilities that required constant one-off fixes, despite existing mitigations like ASAN, fuzzing, and leak tests. The project, which now sees 22 million monthly CLI downloads and powers tools like Claude Code, aims to deliver a more stable foundation for its bundled transpiler, package manager, test runner, and Node.js API implementations.
Jarred Sumner