Rewriting Bun in Rust
5 hours ago
- #bun-rust-rewrite
- #ai-assisted-development
- #performance-optimization
- Bun started as a Zig port of esbuild's JavaScript/TypeScript transpiler and grew into a large-scope project including a package manager, test runner, and Node.js APIs.
- Stability issues like memory leaks and crashes in Zig led the team to rewrite Bun in Rust using Claude AI, completing the port in 11 days with extensive automated workflows and adversarial reviews.
- The Rust rewrite fixed 128 bugs, reduced memory usage, decreased binary size by ~20%, improved performance by 2-5%, and enhanced maintainability with Rust's safety features.
- Key challenges included mapping Zig patterns to Rust, handling compiler errors, and ensuring zero regressions through a comprehensive test suite and adversarial code review processes.
- The project used 64 Claude AI agents at peak, processed billions of tokens, and resulted in 6,778 commits, demonstrating the scale of AI-assisted code rewriting.
- Future improvements will leverage Rust's borrow checker, Miri, LeakSanitizer, and continuous fuzzing to further enhance stability and performance.