“A rewrite in another language would take a small team of engineers a full year. A year of zero user-facing impact is not a realistic option we could consider.”
Bun converted 535,000 lines from Zig to Rust in 11 days for $165,000 using 64 parallel AI agents. The number sounds cheap until you read the prerequisites. It needed a massive test suite, engineers who already knew every line of the codebase, and someone to babysit 64 agents through 16,000 compiler errors. The AI did the typing. The humans did the hard part first, and that part does not show up on the invoice.