Jarred Sumner reports 99.8% of Bun’s existing test suite passes on Linux x64 glibc in an experimental Rust rewrite, achieved in roughly 6 days.
Key Takeaways
Target platform is Linux x64 glibc; other platforms not yet confirmed at this compatibility level.
The rewrite is experimental – Sumner previously stated there is “a very high chance all this code gets thrown out completely.”
99.8% pass rate means the rewrite leverages Bun’s existing comprehensive test suite as the acceptance criterion.
A blog post with performance details is forthcoming from the Bun team.
Hacker News Comment Review
Commenters widely note the test suite itself is the real enabler: 6 days of LLM-assisted porting was only viable because of hundreds of thousands of hours already invested in Bun’s test infrastructure.
The Zig-to-Rust motivation resonates with some: Bun has a reputation for crashes and memory bugs, and Rust’s type system plus unsafe-visibility may reduce them, though heavy use of unsafe would limit gains.
LLM tooling (reportedly Anthropic’s Mythos with large token budgets) is central to the timeline; commenters flag that compute access is becoming a competitive moat, with one parallel TypeScript-to-Rust port (tsz.dev) at 99.6% after 5 months without equivalent resources.
Notable Comments
@Jarred: “cargo check reported over 16,000 compiler errors” at the initial branch stage – performance is already competitive despite the rapid timeline.
