Bun Creator Uses Claude AI to Rewrite Core Code From Zig to Rust, Sparking Backlash

Bun’s creator, Jarred Sumner, triggered a significant open-source backlash by using Anthropic’s AI assistant Claude to rewrite millions of lines of Bun’s core infrastructure from Zig to Rust, sparking heated debates about AI-generated code maintainability and open-source stewardship. Although the rewrite has been merged into the main branch with 99.8% of tests passing, Sumner clarified the project remains an experimental side-by-side comparison to evaluate Rust’s memory safety and stability against Zig, noting there is a high chance the Rust code will be discarded if it fails to outperform the original. This incident marks one of the first major public demonstrations of AI-driven code migration on a large scale, directly challenging Zig’s no-AI policy and raising concerns among developers about the long-term structural risks of relying on AI agents for critical infrastructure code.