Jarred Sumner reports 99.8% of Bun’s existing test suite passing on Linux x64 glibc in an experimental Rust rewrite, completed in roughly 6 days.
Key Takeaways
The rewrite targets Linux x64 glibc first; no production release announced.
99.8% pass rate was achieved against Bun’s pre-existing, comprehensive test suite, not a new one.
Jarred confirmed the branch started with 16,000+ cargo check errors and could not run JavaScript just days earlier.
The project remains experimental; Bun team has not committed to shipping the Rust rewrite.
Hacker News Comment Review
Commenters credit the speed largely to Bun’s unusually comprehensive test suite, which gave LLMs clear acceptance criteria and a full reference implementation to translate against.
Skepticism centers on heavy unsafe usage in the generated Rust code, which undermines memory-safety guarantees and makes the rewrite less of a stability improvement over Zig than headlines suggest.
The Zig-to-Rust pivot generated pointed criticism about Bun’s strategic consistency, while others noted it demonstrates compute-as-competitive-advantage: teams with more LLM tokens can execute language migrations in days.
Notable Comments
@ksec: High pass rate is downstream of the test suite quality, not just the rewrite speed.
@perlgeek: Raises unresolved copyright question: LLM-translated code from a Zig source may carry original ownership claims despite being machine-generated.
