Bun rebuilt runtime in Rust in 11 days, spending $165K on AI
Jarred Sumner chronicled how Bun’s JavaScript runtime was ported from Go/Zig to Rust in a single 11‑day sprint, driven by Claude Fable 5 and other LLMs for $165 K in token costs. The AI‑augmented effort matched a year‑long team’s output, showing how large‑scale runtimes can be rebuilt at unprecedented speed.