Bun's recent Rust rewrite via an AI-generated PR of 6,755 commits merged in six days raises serious maintainability concerns. The author argues that Zig deserves credit for enabling Bun's early success, and that the switch to Rust is a business decision rather than evidence of Zig's inadequacy. The core concern is that no human has fully read the new codebase — it was written by Claude and reviewed by Claude — meaning global invariants and subtle concurrency or memory bugs may go undetected until a production incident. Passing tests validate known paths but not edge cases, boundary conditions, or cross-function design constraints. The author concludes the real bet is whether AI-generated, unreviewed code can be maintained long-term in production.
