BunFrom the builder
Rewriting Bun in Rust
Bun's team described rewriting Bun from Zig to Rust with Claude Code, motivated by memory leaks and crashes from mixing garbage-collected and manually managed memory, and Bun v1.4.0 will be the first Rust release, now available in canary. The rewrite ran from May 3 to its merge on May 14, taking 11 days and 6,778 commits with no tests skipped or deleted, at about $165,000 at API pricing. Compared with v1.3.14, HTTP throughput rose 2.8% to 4.8% and the Linux binary shrank from 88 MB to 70 MB.
Bun v1.3.14 was the last version of Bun written in Zig. Bun v1.4.0 will be the first version of Bun written in Rust.
Saved . A shortened excerpt from the official blog; the original publisher retains authorship.