Nine Days, One Rewrite, Zero Understanding

Bun's nine-day LLM-assisted rewrite from Zig to Rust demonstrates a critical risk: AI-generated code can pass tests and run in production while remaining fundamentally opaque to the team maintaining it. For runtime systems—among the most complex software—this lack of understanding becomes catastrophic when production bugs demand deep knowledge of implementation logic. As startups and enterprises follow this pattern, a dangerous precedent emerges: prioritizing velocity over comprehension could ship critical infrastructure nobody truly understands.