Comment by GuB-42
8 days ago
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?
8 days ago
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?
I know, its so confusing. Its almost as if the bun rewrite to Rust has absolutely fuck all nothing to do with Anthropic's product strategy.
Well, yeah, it's just good marketing and Bun ultimately doesn't matter anyway, not to the wider ecosystem and especially not to Anthropic. The only purpose Bun had for Anthropic was as a way of getting attention, so that's what they used it for.
In isolation, yes, that does seem like it would have been the better decision for Claude Code, but it also would have severely diminished the value of their Bun/oven.sh acquisition.
Claude Code isn't the only user of Bun (it's probably not even the only user of it internally at Anthropic), and this way they get to keep the Javascript runtime (and other tooling) that their coding models may one day, if not already, prefer to use when given the opportunity. For those kind of apps, you'll probably also eventually find that--what do you know!--Anthropic also has their own cloud offering (instead of Bun being the one to build one) that specializes in running and managing those applications for you. Even if all they get is a community of developers that choose to use Bun over other options, that gives them power and seats at tables they wouldn't have if they just rewrote Claude Code in Rust.
That'd be my best guess, anyhow.
So they had to rewrite Bun instead of Claud Code because they “already had bought Bun.”
This thread is filled with non-sequiturs.
Is Claude Code bottlenecked by performance?
I think a JS runtime is fine because the ecosystem of tools is very large and plugins are easy.
People widely report very high memory and CPU usage.
Not all of the memory usage is the fault of Bun/JS. Some of it is likely memory leaks (holding on to data it shouldn't). However, some of the blame does go to using JS. In Rust you can tightly pack your data if you want to, but in JS you can't have nested structs for example. Every object referencing another object is two separate chunks of memory, each with a header, and a pointer from one object to the other. GCs also use more memory. The overhead adds up.
Building a CLI program in JS is a bad choice, and nobody should be defending this decision. Especially since Claude Code is very much able to write Rust code, and they've shown it can port code. Just port Claude Code to Rust directly.
Why is ecosystem of tools and plugins a bottle neck when they literally own Claude models and as per their boss, code is so cheap that anything us just an English sentence away?
I knew this was going to be the first reply.
The answer is because you still need at least one human to develop and test any tool, integration, feature.
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it does seem to be very much bottlenecked by performance, yes. very slow to start up, for example.