Bun rewrote 1M lines of code in 11 days — and it's faster than ever
anthropic's claude fable 5 rewrote bun from zig to rust in 11 days, generating over a million lines of code. it signals a massive shift in developer productivity.
bun developer jarred sumner utilized a pre-release version of anthropic's claude fable 5 to completely rewrite the bun javascript runtime from zig to rust in just 11 days. running 64 instances in parallel, the ai generated over 1 million lines of code for an api cost of $165,000, a task estimated to take a human team a year. the new rust-based bun v1.4.0 canary build fixes 128 memory errors, runs 2-5% faster, and offers improved reliability. this acceleration highlights how advanced models are poised to fundamentally disrupt traditional software development workflows.