Claude Code uses Bun written in Rust now

Post by jeremyjh » Sun, Jul 19, 2026, 4:43 PM UTC

GuB-42 wrote: post #209

Why all the mess with Bun? Couldn't they have rewritten Claude Code in Rust directly? No more need for a JS runtime, better performance, etc... If their agents can do Zig to Rust, why not JS to Rust?

Post by amoss » Sun, Jul 19, 2026, 4:47 PM UTC

fny wrote: post #290

weakfish wrote: post #212

Maybe I’m taking crazy pills, but I’m still stuck on “why the hell does a TUI need to run in terminal React by way of JavaScript” The fact that Anthropic felt the need to buy a runtime so they could make their TUI better speaks more to the quality of engineering than anything else IMO. If rewrites are so easy, why not rewrite CC in a native language? Would’ve been a hell of a lot cheaper.

JavaScript is dynamic and supports live reload which means iterations are far faster than would be in a compiled language--even for LLMs. This is especially useful when you're trying to evaluate behaviors while changing state surgically.

Post by AndrewKemendo » Sun, Jul 19, 2026, 4:47 PM UTC

weakfish wrote: post #304

AndrewKemendo wrote: post #267

Earlier quoted context omitted.

>Because I’ve been told that Fable can do anything I hear some version of this anecdote constantly yet despite using all these prompting tools since 2019 I have never once heard a lab or professional say “x model can do anything” Can you provide me whatever specific source you heard for this?

It’s hyperbolic and intended to generalize the sentiment I perceive from others. Dario Amodei said in January that he expected software engineers to be replaced [0], so I suppose the quote should be extended to “can do anything… a software engineer can do” And I think we can all agree that SWE is on the more complex end of all white collar jobs. So, my thinking is that if SWE can hypothetically be replaced, so can ma…

Post by AndrewKemendo » Sun, Jul 19, 2026, 4:50 PM UTC

coldtea wrote: post #315

AndrewKemendo wrote: post #267

Earlier quoted context omitted.

>Because I’ve been told that Fable can do anything I hear some version of this anecdote constantly yet despite using all these prompting tools since 2019 I have never once heard a lab or professional say “x model can do anything” Can you provide me whatever specific source you heard for this?

> I have never once heard a lab or professional say “x model can do anything” Yeah, they "merely" say that they're about to break the singularity in a couple of years, that it's too capable to be safe to release, that it's going to take 50% (or all, depening on the day and audience) of programmers out of work, that it's smarter than Nobel prize winners, that their programmers don't write anything themselves anymore,…

Post by weakfish » Sun, Jul 19, 2026, 4:51 PM UTC

coldtea wrote: post #295

switz wrote: post #236

Earlier quoted context omitted.

It largely works and it's a massive business success. This is the classic engineer asking the 'why this technology?' to what amounts to a business question. They chose it early on, it works, and it makes obscene amounts of revenue. End of story. That doesn't mean it was the "greatest" choice, or has a perfect technical architecture. Rewrites are never easy, even the bun rewrite. But a non-UI developer tool with a rig…

> It largely works and it's a massive business success. This is the classic engineer asking the 'why this technology?' to what amounts to a business question. Your counter argument would be valid for a 2000 or a 2020 business decision about some tech stack. But the whole point of their product is that it supposedly nullifies such "business" concerns around the use of technology, by making it cheap and fast to build w…