Theres thousands of PRs from claude agents or whatever.

Yeah really feels like a worthwhile place to contribute lol.

I feel weird having to defend reality; reality being that it was merged nearly 2 months ago and tons of people have had their pitchforks out without a shred of actual evidence that this made bun worse in any measurable way. But they still insist it was a mistake.

I’ve never met Jared or the bun team but I don’t understand all the personal attacks, I just feel the need to correct the facts. Literally who cares what language a JS toolset is written in?

It’s not like they ported JavaScriptCore (the actual JS runtime) to rust even. All that stuff is largely untouched.

I'm concerned that the complete rewrite in an entirely different language is not a sound technical decision and instead is a ploy to shed copyright claims from past contributors.

Now, based on comments from this thread, the formerly FLOSS project is somehow granting special access to a corporation that apparently is invested in going way out of their way to push implementations that consume the complete rewrite before the world has access to it.

I for one won't be touching Bun. This doesn't pass the smell test. It feels like a bait-and-switch in progress.

Now it is a Deno clone, both without anything enticing over node.js.

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 funny experiment I did" and then taking that into production with barely any announcement is what kills off the interest to me.

Bun has been a great ad for whatever LLM they were using but the cool factor is gone now, and that's really what set it apart from basic NodeJS in my mind.

“bun the JavaScript runtime ” is not dead though.

It's not about making the dev experience better than node, that use-case is now secondary.

Nevertheless, the principles of open source never demanded more than providing the source upon request.

That’s patently false, just read Jarred’s own blog post describing how that was the first stage only, they went through many more to get the amount of non idiomatic, unsafe Rust code to an acceptable level.

> If projects like Bun can be substantially rewritten and shipped to millions of users, it suggests we're entering a very different phase of software development.

exactly. this wasn't a technical project. this was a marketing stunt that worked on you.

It's not just typechecking, the typescript library is also the reference parser for TypeScript and reference emit. Emitting JS from TypeScript is non-trivial and non-local.

It's not just in browsers, you might want to run the typescript library on the edge or in some restricted environment where JS/WASM is OK but native code is not.

You may want to use the typescript library as a dependency in your own package. TypeScript becoming non-pure JS means that your library also becomes non-pure JS.

Secondly, WASM isn't the right target for the browser anyway, JS and the DOM have to be what you consider "native", for the most rigorous UI projects at least (which building an IDE is). If you want to build a cross-platform UI product that doesn't require installation and has Emacs-like levels of extensibility, JS is the end of the line in terms of language selection. There are no other candidates.

True.

> has fewer bugs

Nope, this is demonstrably false because Rust has its own invariants around its types and the codebase is violating a lot of them.

> every potential memory issue is neatly annotated by an unsafe block

"Potential memory issue" can originate in unsafe blocks and safe code that are able to alternate the input condition of these unsafe blocks. Guess what? That still counts towards 100% in this code base, hence the abomination remark.

> refactor them out one by one

Not as easy as it sounds. They are like threads in a yarn ball, if there are one or two ends visible it's easier to sort them out. The actual situation is more like we have tens of thousands of ends (all the raw pointer code that comes with every shared object), to fix them it's basically a requirement to unwind the whole thing (rewrite all the callees and reorder the data flow as needed, redesigning all the APIs during that).

It's too early to declare it as anything remotely close to a win, optimistically saying.

who claimed that? Are you suggesting that the rewrite did not introduce any new bugs? The correct answer is, by the way, that no one knows since it's millions of lines of code no one has properly read.

> smaller, faster

I thought this has already been debunked. You could just write better zig and make it smaller, faster (and have fewer bugs!)

And like, this is just the beginning of the port. They did a mechanical port basically line by line, next step is to make it idiomatic rust.

I thought by now people would’ve learned to stop betting against this rewrite.

It would have made far more sense, for reliability, efficiency, cost, etc., every metric really, to use or write a source to source translator that preserves as much structure from the original code as possible. Typically if you do a rewrite there are lessons learned from the existing code base that you want to take into account when doing the rewrite; using a bunch of agents to do the porting file-by-file buys you none of that. In either case the code will be an unidiomatic translation, just with LLMs you get an added source of indeterminism and a huge bill at the end of the month.

The "ai" tagged posts (2,100+) significantly outnumber "sighting" posts by orders of magnitude. Even searching HN, this post is the very first mention of it.

Perhaps that is why everyone here (except you) overlooks that or why we don't see much more of those sightings posts here either.

The same tool, in the hands of someone that doesn't know how to handle it? I'll let you finish that

Basically, a good developer can handle the tool better by asking the proper questions, setting good guardrails and tweaking the output where needed

You could test this by running "yes > /dev/null" in Ghostty. In Activity Monitor on my Macbook it shows `yes` using 100% and Ghostty using 0.5% of cpu.

With js you get 1 thread at 100% utilization. Power usage and heat scale non-linearly with cpu utilization and 100% utilization on a single threaded js app means you will have ui lag. Other languages like golang would split work across 8 threads and have 8 threads at 20% utilization and this would result in less power usage. Claude Code would have been better off performance wise being an electron app because it would be offloading rendering to the browser and gpu.

Also, the architecture of Open Code is actually a lot better here than Claude Code. ClaudeCode does everything, including rendering in a single thread and it's all in js. OpenCode has a zig based tui renderer it offloads that work onto.

But I will also say these coding agent tuis do get unfairly maligned because they launch subprocesses and those subprocesses tend to be expensive. If you are using Rust analyzer with claude code, it's rust analyzer that's causing the majority of your problems.

I have been trying to keep away in the last couple weeks and it was all win for me. I still come down here sometimes when I am stressed with real work since it is a strong addiction to see “how terrible the plebs are doing”.

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 rigid API surface contract (and associated tests) will always be easier to trust after a rewrite than a partially tested UI tool with ambiguous functionality.

This is especially useful when you're trying to evaluate behaviors while changing state surgically.

It's hell to maintain for not much gain (for a use case like this at least). As much as it's become a meme, JS and web tech in general has become extremely portable and stable.

I also don't think Anthropic bought bun to make their TUI better. They could have forked it, they bought bun because it incidentally was excellent for the way agents prefer to work and they wanted to capture that audience.

This is close to the same "why Spotify is a chromium embed?" question. Because it works, and users are ok with it.

Is this because Codex is written in Rust and not JS? I dunno. I think it's more just "lighter" in general, or it certainly feels that way. It's probably possible to make something with a similar feel in JS, just perhaps not with the big honking mess they've created.

I suspect user facing/fast moving code (UX layer) will move to dynamic systems with fast iteration times. Infra layer will move towards safe systems level environments like Rust. I'm not sure where Java/C# lands in all of this - it's kind of the middle ground between these two worlds but the tradeoffs change drastically with LLMs - my gut feeling says that TS/Python is good enough for UX work and Rust is better for systems work so it gets less popular going forward.

[1] https://avi.press/posts/2026-07-10-after-7-years-in-producti...

No, you are not crazy. They do crazy things with unlimited budget, and still their chat app flickers when using.

They should just port pi-tui from pi coding agent, since they have no clue.

It's like asking "why does everything run on Windows?" Because everything runs on Windows.

Here I would just like to mention that if you have to rely on "de-virtualization" passes, you're in a miserable situation architecturally. If you have code where the overhead of virtual function calls might be too much to pay, don't do virtual functions then. End of story.

To deconstruct a pool of objects, I don't see what should ever be wrong with a function pointer. The overhead of loading the function pointer will get divided by the number of objects being deconstructed. Care to explain what's the issue here?

A garbage collected language does this automatically. Rust still requires thinking about and tracking memory lifecycles, but the borrow checker will complain and keep you from doing it wrong. That's why LLMs like Rust. It gives immediate feedback on what to fix. By-default constant reference parameters helps prevent major performance problems.

Even with the huge amount of "unsafe" rust currently in bun? https://news.ycombinator.com/item?id=48967630

AT&T was the one doing the Cyclone research.

And then we have a bunch of folks assuming they know better about C that its own authors?

You could! You could not release a “pile of vibe coded slop” onto people’s machines. There don’t even appear to be any particular advantages to Claude upgrading early. If there are no one has been made aware of it.

That might even be the reason why they switched to rust.

Don't worry too much.

I think it's the "infringing usage" question that is more interesting. If the LLM trained on GPL-derived code, what does that mean for the end result?

> These apps are doing real work taking text that is streaming in and doing syntax highlighting, calculating diffs, and rendering markdown.

The first argument is that these are expensive operations. They are not. And the second argument is the assumption that these are desirable things for an agent system to be doing. That's a personal preference but, personally, I don't want them and would appreciate a way to disable all of that to reduce CPU use.

I am 46 y/o and still excited to code and solve problems with code and I still have trouble to admit to myself sometimes that people make dozens of millions with PHP and the tech hardly matters when you can throw bodies at the problem (and when that throwing of bodies at the problem actually solves it, of course).

Tabs vs spaces makes no tradeoffs. Tech choices do

It is rarely the case that technology choice is the make-or-break when it comes to whether a product is successful and achieves widespread adoption. Some choices are less ideal than others, but at the end of the day if you manage to make something that people want, the rest won't matter much.

Why would it be harder and/or more time consuming rather than the opposite? It's like having full specs and a full test-suite to match against the result you want.

Cheaper, but not free (if you don't buy into the marketing promises too much). The bigger the project, the bigger the cost, even with a discount.

At the same time, the early versions weren't very good and you can be sure that any rewrite will also need to be similarly iterated upon until it is also good enough and polished.

If you do that and don't spend enough effort on making it be something polished --> your competitors have a better product and you lose.

If you pause feature development to give enough effort to the initiative, you don't get to add new features quickly enough --> your competitors have a better product and you lose.

Maybe their priorities lay elsewhere, like how I've noticed that the desktop app version of Claude Code has gotten both faster (no 2-4 second lag when switching conversations), more stable and usable over time, to where I enjoy using the models because of it, not in spite of it (though not that they haven't had bumps along the way, like that one cache invalidation issue, or how people didn't like the auto accept timeout thing). I don't doubt that you can get pretty far with gradual patches and improvements, instead of only big rewrites.

Honestly it's really cool for me to see Kimi having their own CLI too, same with OpenCode, Pi, Hermes (well more of an agent than just a coding harness but you get the idea) - there's so many competing solutions out there, each good or bad in unique ways.

Just wish we'd see similarly many GUI solutions, for now OpenCode GUI seems like the one I've settled on (cross platform and supports most models), though it's not exactly ideal either (feels a bit barebones, especially in regards to sub-tasks and progress/plan tracking, even ZCode seems a bit better in that regard, it was actually surprisingly good after they pushed out some updates).

This is a spectrum, it's not just 0% vs 100%. Even Fable frakked up a few things really badly in my professional work (though to its credit after a very detailed 2h chat it self-corrected and fixed all the blunders).

I would also challenge "fast" -- Fable (and I assume Mythos) are wicked fast and efficient and even they can't compensate for f.ex. slow recompilations or test suite reruns or security scans, linters etc.

Reminder that the Bun's Zig-to-Rust rewrite took 11 days with dozens of agents working 24/7 and the author put the cost they'd pay (if they had to pay) at about $168k.

This can be true, while "nullifies such "business" concerns" can be false. Both are not dependent on each other.

Automation doesn't "nullify business concerns", it just changes them.