The Bun author himself writes that the port is not idiomatic Rust:

    Do the rewrite that looks like we transpiled our Zig code to Rust. We can gradually refactor it to reduce unsafe usage and look more like idiomatic Rust after Bun v1.4 ships.

The original version of Bun was already a line-by-line (manual) port of esbuild from Go to Zig (also mentioned in this post), so the Zig code already wasn't "Zig-idiomatic" and apparently riddled with problems. That doesn't inspire much confidence in the LLM-translated Rust version tbh.

> That doesn't inspire much confidence in the LLM-translated Rust version tbh.

And yet Claude Code, which is the primary consumer, continues to chug away without any issue (that I, as a fairly heavy user, have encountered).