Bun begins Zig-to-Rust port with Phase-A guide commit

The Bun JavaScript runtime project has landed an initial commit (46d3bc2) adding a Phase-A porting guide, signaling the start of a migration from Zig to Rust. The change is documentation-only at this stage — 622 lines added across two files — laying out the plan rather than moving runtime code yet.

The shift is significant because Bun has been one of Zig’s highest-profile production showcases, used to argue for Zig’s viability as a systems language for performance-critical tooling. A staged port to Rust suggests the maintainers see ecosystem maturity, contributor pool, or long-term maintenance burden as worth the rewrite cost, even on a codebase explicitly built around Zig’s strengths.

For downstream users, nothing changes immediately — Phase-A is a roadmap, not a rewrite. But the move reframes the Zig-versus-Rust debate in systems tooling: a flagship Zig project choosing to migrate carries more weight than benchmark arguments, and other Zig-based projects will be watching how the transition is sequenced and what tradeoffs surface.