Bun's AI-Generated Rewrite from Zig to Rust: 1 Million Lines, 10,000+ Unsafe Blocks
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By dreamreal|June 3, 2026|Updated 12:14pm ET
Fresh out the oven, still warm. Top of the tray.
Summary
Bun, the JavaScript runtime, has been rewritten from Zig to Rust through an AI-driven process. Anthropic (which acquired Bun in December) supplied Claude Code agents that generated over a million lines of Rust code across 6,755 commits in nine days. The rewrite passed 99.8% of existing tests but introduced more than 10,000 unsafe blocks, raising questions about whether the memory safety goals of Rust were actually achieved. The article explores the implications of AI-generated codebases, the irony of unsafe Rust blocks in a memory-safe language, and what this means for the future of software development.
Key quotes
· 5 pulledwe haven't been typing code ourselves for many months now
a little over a million lines of Rust, 6,755 commits, generated almost entirely by Claude Code agents over nine days
The Rust rewrite passed 99.8% of the existing tests
Memory safety is the main reason you'd pick Rust. So what did the rewrite actually accomplish?
the PR itself split almost evenly between thumbs-up and thumbs-down
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