Zig is a moving target. 0.15 -> 0.16 includes some massive structural changes concerning IO and async/threading.

Claude has absolutely no idea what it's doing with bleeding edge zig unless you feed it source and guide it closely (in which case it's useful for focused work) - I'm building a game engine & tcp/udp servers with it and it requires a hands-on approach and actually understanding what's being built.

I imagine these are not really concerns with rust at this point.

In my ideal world the team behind bun would be putting in the work to keep up with modern zig, but it's starting to look like they are running mostly on vibes in which case rust might be a better choice.

Contributors and maintainers will also be easier to find in Rust than Zig.

Zig is a great language and I want to see it succeed, but this is a prudent move for Bun.

I would expect all LLMs are going to be better at Rust than Zig - a strong, thorough compiler will simply prevent more mistakes, and the benefits of a "simple" language decreases the larger the code base gets. The more abstractions exist, the less valuable "no hidden control flow" or "no hidden allocations" from the standard library get, and that's before you add the mother of all abstractions of vibe coding.