Burning $160,000, Frenziedly Coding 1 Million Lines: Bun's Creator Rewrites the Foundation with Claude
**The Bun creator used Claude to rewrite its core in Rust in under two weeks for $165,000.**
Jarred Sumner, the creator of the Bun JavaScript runtime, leveraged Claude Code to migrate the project's entire codebase from Zig to Rust—generating 1 million lines of code in less than two weeks. This cost approximately $165,000 in API tokens, a fraction of the estimated $3 million and 4 years a manual rewrite might have required. The new Rust-based version passed all existing tests and was quietly released in June.
Inspired by this, Instagram co-founder Mike Krieger also used Claude to migrate a Python library to 165,000 lines of TypeScript over a weekend, slashing build times dramatically.
Anthropic, the creator of Claude, formalized the process into a six-step framework for large-scale AI-assisted migrations. The core principle is to "fix the loop, not the code": the system uses existing code as specification, automated tests as judges, and iterates through generation, review, and repair cycles without constant human intervention. This approach makes large-scale migrations, once a daunting and costly task, a feasible and cost-effective automated process.
marsbit07/17 08:20
