Anthropic's Claude Code agents converted Bun from Zig to Rust over nine days, generating more than one million lines of code across 6,755 commits. The project passed 99.8% of existing tests while reducing binary size and improving benchmarks. Jarred Sumner revealed the team hasn't manually coded for months, sparking intense discussion across developer communities.

The conversion used a faithful porting strategy that maintained the original architecture but introduced 10,000+ unsafe blocks. This approach preserved behavior but undermined the primary justification for switching to Rust—memory safety. The unsafe count represents two orders of magnitude more than comparable projects like uv.

The core challenge lies in verification. Generation scales rapidly while verification remains painstakingly manual. This asymmetry creates a fundamental gap between code production and safety assurance, leaving even well-tested AI-generated code with significant unverified risks that humans cannot audit at production speed.