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Claude Code uses Bun written in Rust now

simonwillison.net

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Re: Claude Code uses Bun written in Rust now

#32
post #5

Earlier quoted context omitted.

Why does changing to Rust kill the project? I don't understand the point here.

My personal feelings about the matter is that having an LLM rewrite the entire thing as an experiment and then just going with it a few weeks later kills any incentive for a community to build up around it. It's a clear signal that every basic aspect of the runtime can change on a whim. I don't care about meh Zig being rewritten to bad Rust if it does the same thing, but taking what is presented as" look at this funn…

The language an application is authored in does not matter to me, as a user. I care that it is widely-used (safety in numbers), that it works, and that it is fast.

It's cool that the Zig project exists, but I'm unlikely to ever use Zig so that’s sort of orthogonal to my interests.

Re: Claude Code uses Bun written in Rust now

#33
post #19

> Startup got 10% faster on Linux but otherwise, barely anyone noticed. Just that? I was expecting more from that rewrite. Maybe Rust is not so worth it after all.

I don't think their motivation was primarily user-visible stuff. They backed themselves into a corner by forking Zig, and also were fed up with fixing memory errors.

You wouldn't notice either of those if you were a user, unless you happened to hit one of those bugs.

Re: Claude Code uses Bun written in Rust now

#35
post #5

Earlier quoted context omitted.

Why does changing to Rust kill the project? I don't understand the point here.

My personal feelings about the matter is that having an LLM rewrite the entire thing as an experiment and then just going with it a few weeks later kills any incentive for a community to build up around it. It's a clear signal that every basic aspect of the runtime can change on a whim. I don't care about meh Zig being rewritten to bad Rust if it does the same thing, but taking what is presented as" look at this funn…

Which community specifically though? The overwhelming “user” community would be web developers and people writing JS/TS, right? Not zig/rust developers.

Re: Claude Code uses Bun written in Rust now

#37
post #22
post #5

Earlier quoted context omitted.

Why does changing to Rust kill the project? I don't understand the point here.

Emphasis on the FOSS project. The v1.4 mentioned is not (yet?) open source, Claude Code is essentially using a proprietary fork, was GP's point.

You can install it now we with bun upgrade —-canary it something along those lines.

Re: Claude Code uses Bun written in Rust now

#38
post #7
post #5

Earlier quoted context omitted.

Why does changing to Rust kill the project? I don't understand the point here.

Yeah same, according to one of the Zig team members, the original source code wasn't all that anyway. But this is HN, a subsection of which places a high importance on what language something is written in, moreso than what it does (feels like).

An interesting tidbit is that large parts of the original Bun source code was a line-by-line port of esbuild from Go to Zig (mentioned here: https://bun.com/blog/bun-in-rust), tbh this lowered my respect for the project a bit (a line-by-line port simply isn't as interesting as original work), and it might also explain the subpar Zig code quality (a line-by-line port from Go to Zig simply won't result in idiomatic Zig). It also might explain why porting from Zig to Rust was done 'on a whim', the actual source code (and the idea of 'original work') never seemed to be all that important to the author (and I wouldn't be surprised if the project does more language-hopping in the future heh).

Re: Claude Code uses Bun written in Rust now

#40
post #5

> For me this outputs Bun v1.4.0 (macOS arm64). The most recent release of Bun on GitHub is currently v1.3.14 from May 12th, so that v1.4.0 version number in Claude supports them shipping a preview of a not-yet-released Bun version. And so, the FOSS project "Bun" silently dies in darkness and is now something completely else. I'm glad I still had "Investigate if Bun is worth it" on my TODO list and hadn't yet gotten…

Why does changing to Rust kill the project? I don't understand the point here.

Rust as a language is irrelevant to this discussion, the problem is that bun was vibe coded by a single dude without any open source community involvement. “bun the open source project” is basically dead at that point: don't expect any of the zig enthusiasts who had their code being forcibly rewritten in a language they don't like to follow Jared.

“bun the JavaScript runtime ” is not dead though.

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