Zig’s creator calls the rewritten Bun “untested garbage”

Last week Jarred Sumner said he ported Bun’s runtime and toolchain from Zig to Rust in 11 days by running about 50 parallel Claude Code workflows. Output peaked around 1,300 lines of code per minute and topped a million lines of Rust in total, at a cost of roughly $165,000 in API pricing.

The trigger was a pile of accumulated bugs, including a bundler flaw that leaked 512,000 lines of Anthropic’s source in March. The rewritten Bun passed 100% of its test suite, more than a million checks across every platform.

Zig creator Andrew Kelley pushed back in a post titled “My Thoughts on the Bun Rust Rewrite.” His question: if the tests didn’t catch the bugs in the Zig code, how are they going to catch them in a million lines of untested Rust? The Zig project had earlier rejected Bun’s patches, citing a policy against AI-generated contributions.