Bun Rewritten by AI from Scratch: One Million Lines of Code in 11 Days
64 instances of Claude Fable 5 rewrote Bun — a popular JavaScript runtime — from Zig to Rust in 11 days, generating more than one million lines of code at an API cost of $165,000 (~1 engineer year).
Bun (a JavaScript runtime, i.e. developer tool) has been fully reimplemented from one programming language to another within 11 days. 64 parallel instances of Claude Fable 5 generated over one million lines of code. The API cost was $165,000 (~1 engineer year). The outcome: Bun v1.4.0, which is ~2–5% faster and fixed 128 bugs.
This is the first reported example of a significant real-world developer tool being automated by dozens of AI agents. We have reached the point where full architectural migrations can be automated by AI.
Source: the-decoder.com
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Author
Evgenii Arsentev
PhD · Chief Executive Officer, digital health
Articles · Latest articles