17 ms·

Claude Code uses Bun written in Rust now

608 points by tosh 3mo ago

embedding-shape 3mo ago
> 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 to it. What is the governance structure for Bun by the way? Couldn't find any documents/explanations about how it's supposed to work. I'm guessing it's essentially just "Anthropic decides what gets done and accepted" today?
- minraws 3mo ago
  It's largely just what jarred is willing to accept this week afaik or not, and they did put the bun 1.4.0 version bump in the changelogs for claude code a while ago, over a month almost. Though most will be forgiven to not reading it since well it's all AI anyways. I don't know how I feel about all this yet, maybe someday.. ooof
  - jdiff 3mo ago
    > they did put the bun 1.4.0 version bump in the changelogs for claude code a while ago, over a month almost. Where? Is see no CHANGELOG in the root. I do see LATEST, last modified 2 months ago, and it says 1.3.14
    - simonw 3mo ago
      The Claude Code release notes. Not the Bun release notes: https://github.com/anthropics/claude-code/releases/tag/v2.1.181 https://github.com/anthropics/claude-code/releases/tag/v2.1.... > Upgraded the bundled Bun runtime to 1.4 (Though that doesn't clarify that this is the Rust rewrite)
- junon 3mo ago
  Why does changing to Rust kill the project? I don't understand the point here.
  - pjmlp 3mo ago
    Definitely, it was a possible reason why Zig actually matters in the industry. Now it is a Deno clone, both without anything enticing over node.js.
  - Cthulhu_ 3mo ago
    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).
    - gipp 3mo ago
      I don't think the GP had anything to do with the language change itself. More that it marks a clear point of Anthropic taking ownership and governance of the project in a less open direction.
    - flohofwoe 3mo ago
      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 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).
      - realo 3mo ago
        I read your link, written by Bun's author and totally get his thinking. In the current world of cyber weaknesses everywhere, infrastructure must be solid and rust is a better choice than zig for something like bun. In other words, bun is not a demo of zig programming that happens to do useful things. Bun does useful things, and must do them securely. That is its number one priority, language is secondary, inasmuch as it helps doing useful things securely.
- deleted 3mo ago
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- ranguna 3mo ago
  The PR is public, you can build and use it as well. The anthropic team just decided to use it, and you can as well.
  - embedding-shape 3mo ago
    > The PR is public I'm talking about the 1.4.0 release: > Claude supports them shipping a preview of a not-yet-released Bun version Maybe Bun/Anthropic fixed this after Simon's initial release of the blog post, but seemingly when we both looked, it wasn't public.
    - thevinter 3mo ago
      > Update: The Rust version has been released as Bun canary - running bun upgrade --canary will install this release.)
      - embedding-shape 3mo ago
        Yeah, of course Anthropic making the version publicly available AFTER people notice it wasn't public, completely solves the issue ;)
        simonw 3mo ago
        Anthropic changed nothing since I wrote published this post a few hours ago - I updated my post to mention Bun canary since it was a point of confusion here on Hacker News.
        nicce 3mo ago
        Claude Code has shipped Bun 1.4. already more than month ago: https://github.com/anthropics/claude-code/releases?q=bun&expanded=true https://github.com/anthropics/claude-code/releases?q=bun&exp... Version was changed in Bun in May 18 https://github.com/oven-sh/bun/commit/b18bf6d1d0a92238f240bfd125f0e3b3461b9243 https://github.com/oven-sh/bun/commit/b18bf6d1d0a92238f240bf... So it has been canary since then, most likely, if docs are accurate that latest main is canary.
- TheRoque 3mo ago
  I had "investigate if bun is worth it" too, and decided not to use it, but instability was one of the reasons. So it feels it was the right move.
baq 3mo ago
Turns out it was just a build step after all.
kburman 3mo ago
Honestly, I initially thought rewriting an entire codebase with AI would be a huge mistake. After reading this, I'm starting to think I was wrong. 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. Today's AI-generated rewrites may not produce code that humans would consider high quality or maintainable. But I'm beginning to wonder whether that will even matter in a few months. If AI is the primary consumer, maintainer, and refactorer of code, human readability becomes far less important than correctness, performance, and the ability to iterate. This feels like a shift where software may no longer exist as a long-lived artifact in its current form. Instead of writing and maintaining applications for years, we may generate, adapt, and discard them continuously for each use case.
- sdevonoes 3mo ago
  We are the ones to get to decide. Do we want that? I don’t. But im just a single data point
- rho138 3mo ago
  That sounds like a massive waste of finite energy and compute resources.
  - CrimsonRain 3mo ago
    That's like saying let's stay with horses. We'll develop faster and better tech. We'll find resources to feed that. Use that to build better. Access better resources. We'll mine asteroids. We'll harness much more from the sun. The factory must grow.
    - rho138 3mo ago
      Is that before or after the earths atmosphere acidifies for humans and our bodies can’t hold enough phosphorus or calcium for basic metabolic tasks? You have until 2050: https://doi.org/10.1007/s11869-026-01918-5 https://doi.org/10.1007/s11869-026-01918-5
gabrieledarrigo 3mo ago
Bah. Personally my take on the entire affair is quite negative, whatever Jarred or Simonw says about it. I think Bun owned by Anthropic and the entire rewrite with AI is not the real point (even if it's quite interesting, though). My take is that Jarred, and Bun,didn't demonstrate a serious, adult approach, from "this is my branch, you are overreacting" message to just proceeding with a 1mil+ PR merged in less than month. The communication is the issue, and it was handled very badly, in a way that impacted trust and divisions. Was it so difficult to adopt the approach that the TS team adopted for 7.0?
- baq 3mo ago
  I guess the point is none of it matters, CC users didn't notice or don't care except an exceptionally small minority.
  - deleted 3mo ago
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  - ai_fry_ur_brain 3mo ago
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  - snemvalts 3mo ago
    The lowest of the bars
    - drodgers 3mo ago
      But the only one that matters? Seems like this is delivering business value.
- conartist6 3mo ago
  Haha TS7 is the next biggest example of, "Let's just do a line by line port to another language instead of seriously examining our architecture"
  - 3mo ago
bel8 3mo ago
Contrary to many, I have high hopes that Jarred and team will lapidate the ported codebase and it will continue to flourish as an open source project.
znpy 3mo ago
> 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.
- IshKebab 3mo ago
  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.
- ifwinterco 3mo ago
  It was already written in a very performant language so no significant performance improvements should be expected. The benefit of a rust rewrite is memory safety improvements, but currently they've just rewritten zig to unsafe rust so they don't have that either yet
- voiper1 3mo ago
  The blog claims rust chosen mainly to address memory issues, which rust is a better language for. So, success would simply be less new memory errors / easier to patch old ones.
  - marcindulak 3mo ago
    Claude installer/updater had a high memory usage problem (Gigabytes of resident memory used during a fresh installation of Clade with it's native install.sh script, or during a claude update). This was reported as early as December 2025, see https://github.com/anthropics/claude-code/issues/12327#issuecomment-3614767879 https://github.com/anthropics/claude-code/issues/12327#issue.... The latest Claude installer (2.1.215) possibly does not have it anymore https://github.com/anthropics/claude-code/issues/4953#issuecomment-5015922958 https://github.com/anthropics/claude-code/issues/4953#issuec..., but more tries on various machines are needed to confirm that.
ooofydoofy 3mo ago
bun upgrade --canary you are welcome
- deleted 3mo ago
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reddalo 3mo ago
Damn, I should have not migrated to Bun. Should I revert back to Npm?
- cromka 3mo ago
  I am getting into the frontend dev and one thing that I don't understand is why people use bun in the first place? It's not much better preforming, it's not much safer, it's still not 100% compliant. Some tests show it's actually slower than node. Why bother switching, then?
  - johnny22 3mo ago
    i assume it's because of all the built in tooling that node doesn't ship with.
  - awestroke 3mo ago
    Faster package manager Faster startup Typescript support out of the box Better stdlib than node Stdlib includes yaml, sqlite etc so you need to pull in fewer deps, so you can avoid the left-pad/is-even node_modules explosion problem to a greater extent
    - fg137 3mo ago
      Can't comment on others, but new Node.js also has typescript out of the box and works pretty well.
  - vips7L 3mo ago
    I don’t think you would use Bun for front end.
    - frollogaston 3mo ago
      That's what Claude Code does at least
    - cromka 3mo ago
      I mean, Astro on Bun?
IshKebab 3mo ago
This post is just "they didn't lie"...
deleted 3mo ago
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marsven_422 3mo ago
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thrance 3mo ago
Yeah, I noticed. I had Claude write a quick JS script for me a few days ago, it then tried to use Bun to run it. When it couldn't find it, it tried to install it with `sudo pacman`. I had to fucking tell it to use Node instead.
maverickaayush 3mo ago
I've been using Claude Code daily for a fairly large FastAPI project and didn't notice anything unusual around that timeframe. If this really was the Rust runtime underneath, "boring is good" seems like the right outcome.
rs_rs_rs_rs_rs 3mo ago
It is absolutely amazing to me that this ai rewrite work so well, maybe claude is not really that much of a complicated tool to stress the bun runtime but still...
- jqbd 3mo ago
  It works well because they had tests, they could compare before and after. Likelihood of issues especially if you transpile to a safer language should be minimal.
luciana1u 3mo ago
[flagged]
feverzsj 3mo ago
It's a transpile. And not even a good one. The generated code is far from idiomatic rust. Some may consider it an abomination.
- alexandra_au 3mo ago
  grep -nr 'unsafe' . Is all you need to know to consider how much of an abomination it is
  - simonw 3mo ago
    This comment inspired me to take a look at the trend of "unsafe" in the Bun code over time since the rewrite PR first landed - here are the commits where that number changed by at least 10: 2026-05-14 23427db 13907 2026-05-14 19d8ade 13861 2026-05-15 4d443e5 13840 2026-05-17 172afa5 13803 2026-05-17 80a06a8 13849 2026-05-18 fba43af 14026 2026-05-19 303cd28 14052 2026-05-20 21db682 14243 2026-05-22 a06a00a 14239 2026-05-23 49c97de 14090 2026-05-28 472a06a 14076 2026-06-01 a0d1472 14071 2026-06-04 8553428 14032 2026-06-09 717542f 14053 2026-06-10 1c90e5a 14043 2026-06-11 6e91d24 14031 2026-06-16 bd8edc7 14086 2026-06-17 6ef5977 14104 2026-06-20 315ed50 14106 2026-06-22 c6be834 14120 2026-06-23 ea7e44f 14108 2026-06-23 03042ab 14128 2026-06-29 86d32c8 14046 2026-07-01 6640fcf 14077 2026-07-04 51074e3 14099 2026-07-06 9d0e93d 14186 2026-07-08 ab6eb2d 13953 2026-07-09 86caf6e 13936 2026-07-10 91675d0 13930 2026-07-13 73b6c14 13951 2026-07-16 4bbe075 13978 2026-07-16 57e30a5 13995 So not as much cleanup as I had expected! ChatGPT written script for counting here: https://gist.github.com/simonw/b1015bcadcedd1a781cedb7af9cbb2d0 https://gist.github.com/simonw/b1015bcadcedd1a781cedb7af9cbb...
  - rwz 3mo ago
    The original code was one giant unsafe block with almost no tangible way to find or debug all the subtle memory bugs and leaks they had. Now it's smaller, faster and has fewer bugs. Also its every potential memory issue is neatly annotated by an unsafe block so you can go and refactor them out one by one with confidence. All this seems like a pretty huge improvement to me. Why is this an abomination in your eyes?
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aureate 3mo ago
The port of Bun, which has >5000 open github issues, is used in Claude Code, which has >11000 open github issues. Do people use Bun in things that are expected to work reliably? Have any such projects tried the upgrade yet?
- ivanjermakov 3mo ago
  11k in two years vs 5k in two weeks? You're right, numbers speak for themself.
  - entrope 3mo ago
    Did Bun mass-close issues that predated the rewrite? It doesn't look like they did, as the oldest open issue is from 2021 and there are many from 2022, but maybe they did something that killed most of the old issues.
    - endospore 3mo ago
      Their (public) project management is horrible, you can find fixed issues unclosed and unfixed issues closed. Not really surprising when that part of the work is completely taken over by LLM agents though.
- zahlman 3mo ago
  To be fair, https://github.com/python/cpython https://github.com/python/cpython has over 5k open github issues, and that's still generally considered fairly reliably technology even if a lot of HN users seem to hate it.
  - aureate 3mo ago
    It's not a great way of inferring software quality, but I think the numbers for both Bun and Claude Code are pretty bad. cpython has ~7,000 open issues, but ~70,000 closed ones, a 1:10 ratio. Bun's ratio is above 1:2.5, while for Claude Code it's slightly over 1:6. Much more importantly, though, Bun's oldest issue is from Sep 2021, while Claude Code's is Feb 2025. cpython's oldest issue dates from June 2000 (presumably migrated from an older tracker). Claude Code has very nearly the same total number of issues (open + closed) as cpython at around 77,000, but Claude Code has done it in a year an a half whereas cpython has taken 26 years to get there. It's a good comparison to pick, as it can't be explained by popularity. For all the real-world use Claude Code sees, it's nowhere near what cpython sees, even over the year and a half in question. Bun, meanwhile, is hitting these numbers while not even being the mainstream choice for what it does (node still holds that crown afaik).
witx 3mo ago
What is the actual contribution and motivation of this post?
- simonw 3mo ago
  I thought it was interesting. I didn't write this with Hacker News in mind. (I was actually half way through writing about something related, when I thought it would be interesting to see if I could prove that I had the Rust version of Bun on my laptop already.)
- owebmaster 3mo ago
  [flagged]
  - deleted 3mo ago
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  - tomhow 3mo ago
    Please don't attack people on HN, even with vague insinuations. The guidelines ask: Please don't post insinuations about astroturfing, shilling, brigading, foreign agents, and the like. It degrades discussion and is usually mistaken. If you're worried about abuse, email hn@ycombinator.com and we'll look at the data. https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html
- softwaredoug 3mo ago
  People shouldn’t overthink blog posts. Just write what’s on your mind and have fun.
  - rvz 3mo ago
    The motivation is obviously clear. No-one would be doing that for fun 24/7, only covering about AI and nothing else without getting paid for it. If anyone else did that on HN, they would be accused of slop with their domain blacklisted.
tappaseater 3mo ago
Anthropic bought Bun, so they kinda, sorta had to make this work. I am sure the cost at $145,000 in Claude time will get some attention. I am curious how this will work going forward from FOSS perspective. Will humans be allowed to modify the generated code? Only the .md prompts for the agents? Or what?
codethief 3mo ago
Incidentally, Claude Code has been very buggy for me lately (much more so than before). Lots of TUI rendering issues causing, e.g., the conversation history to be garbled etc.
- PsylentKnight 3mo ago
  Every time I resize my window now, the output is completely garbled. I often have to ask it to repeat itself just so I can see what it just said. This isn’t a new thing, but it feels like it’s gotten worse. This is on Windows
  - LambdaComplex 3mo ago
    Does exiting following by resuming the session fix it?
  - anematode 3mo ago
    Same observation. One thing you can do is close out the session and `claude --resume`
- kilroy123 3mo ago
  I'm far from being anti-AI, but these guys take it way too far IMO. It's straight-up AI slop. Like a real engineer still needs to be in the loop and drive the tool. Anthropic seems to be all in on 100% AI code.
- NateEag 3mo ago
  I've been (grudgingly) using Claude since February. When I started, I discovered to my shock that it was by far the worst TUI I had ever touched. Rendering glitches, keyboard input screwups, and just all-around jankiness. Despite that awful baseline, I have to agree that it's gotten noticably worse in the past week or so. It's started mangling my terminal sessions somehow, so that not all characters I input are visible in the UI. Backgrounding it, doing a 'reset', then re-foregrounding seems to fix it. Of course when I asked it to diagnose the problem, it assured me that Claude has no such big and it must be something else I'm running. All I'm running is tmux and Claude, though, and the behavior surfaced while I was running Claude. So, yeah - if they just recently updated Claude to use the Rust rewrite, this increased crappiness might actually be due to that. It does seem to at least roughly correlate.
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lazzlazzlazz 3mo ago
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nottorp 3mo ago
So does that make Claude Code any better? Can you select text with shift + arrow keys now in the command line client? :)
softwaredoug 3mo ago
Whatever the headaches of the internals, I haven’t heard any substantive outcomes in hacker news that have been impacted by this change. Yes if we had a Zig->Rust transpiler maybe it would produce similar output. But I can’t find one. We’d have to use an agent to build one first :)
nirui 3mo ago
All the emotion of speculations aside, how it runs? It boots faster yeah, but what about RAM and CPU usage? Weird dead loop or dead locks? If it run as good as before or even better, then that's kinda impressive. I'm a developer so I really don't like it when AI might took my job, but if everyone on this planet could create a software for themselves exactly as how they wanted with just a few simple demands, that will change the world for the better. Think of it as a democratization of technology. You don't want Microsoft stealing your data? Just ask a AI to write an OS for you. You don't want Google to listen to what you're saying? Just ask a AI to design a phone for you. If one day the AI ended up doing that, it will be the ultimate technology self-sufficient. In front of that, your job security is insignificant. It is also why keeping the tech open source is that much important. Otherwise, it's still the same old shit again and again, and, you lose your job too.
- phinnaeus 3mo ago
  > I'm a developer Then you must know that the hardest part of software development is getting clear requirements... > everyone on this planet could create a software for themselves exactly as how they wanted Even with perfect AGI this will never happen because people will never be able to express clear requirements
  - William_BB 3mo ago
    It's not even about requirements. It's about responsibility. Someone has to take responsibility for the code and the product. Someone has to hotfix a bug that's costing millions of dollars an hour and someone has to be blamed for a bug that's consting millions of dollars an hour.
    - godwinson__4-8 3mo ago
      Not really. The secret of our society is it wouldn't work if people with a controlling interest in things ever faced personal responsibility. Who got blamed for the Iraq war? How much did that cost? The theory is if you tried to blame someone then some future president wouldn't be able to declare war. You don't know how the law works apparently. Corporate law is pretty much the same. The economy doesn't boom if CEOs can actually be blamed for things. You don't blame a "someone" that's what incorporation does. If some code does a booboo just put a $ amount on it, withdraw the funds and move on. The media will focus on the humans because of the drama, but they are largely irrelevant. It doesn't come out of their pockets. A human is already window dressing in this status quo. A LLM has no reason to do the sorts of things that violate such legal protections, be it of a president (none really apply) or a CEO (good luck getting a CEO to take personal responsibility for anything short of outright fraud). If it suddenly goes haywire the law already has a concept of vis major. The secret is individual humans are already largely irrelevant to our society. That's how we got here. The trend will only continue.
hkclawrence 3mo ago
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Aeveus 3mo ago
Anecdotal, but I’ve been getting segfaults in Claude Code. I run inside Kitty tabs, and the entire tab becomes unusable when this happens. No response to inputs at all from that point. When this happens, a link shows up to report the issue. It’s not clickable (likely due to the segfault), and perhaps more important: it’s encoded, so you can’t see what you would be sending in your report. Hope it gets better.
- mort96 3mo ago
  What makes you think it's a segfault? Does your shell print "Segmentation fault"? If so, you should be back at your shell and you should be able to recover the tab by typing 'reset' + enter (even if you can't see anything as you're typing it). If nothing prints "Segmentation fault", this just sounds like a hang
  - javawizard 3mo ago
    I just had this happen today. It was indeed a segfault. From what I could tell it looked like it was in JS code that had been JIT compiled. I haven't attempted to troubleshoot further beyond setting all my future Claude Code instances to pipe their stderr to disk so that I don't lose the stack trace next time.
    - kccqzy 3mo ago
      Bun does not have its own JIT compiler. Bun uses JSC made by Apple. So your blame should be directed to Apple. And I can believe you because I’ve seen JavaScript-heavy Safari tabs crash.
- MitziMoto 3mo ago
  Something similar has been happening to me with Ghostty, but there is no error message or link and it only happens when Claude uses it's interactive questions interface. It becomes completely unresponsive to any input except scrolling. I can't select options or even cancel out. (I am in no way implying this is related to Bun)
- 3mo ago
bikeshedpelicun 3mo ago
[flagged]
- simonw 3mo ago
  Did you create a burner account just to accuse me of bikeshedding Bun's release tag process?
roundabout-host 3mo ago
I have a better idea: convert it to a prompt and commit the prompt to the repository. Then Mythos will be your compiler.
- iririririr 3mo ago
  the whole Ai skit is anthropomorphing the compiler as a coworker.
GuB-42 3mo 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?
- jeremyjh 3mo ago
  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.
  - 59nadir 3mo ago
    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.
- tbrockman 3mo ago
  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.
  - ozozozd 3mo ago
    So they had to rewrite Bun instead of Claud Code because they “already had bought Bun.” This thread is filled with non-sequiturs.
weakfish 3mo ago
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.
- deadbabe 3mo ago
  Should have done it in C++ with SDL3.
- ljm 3mo ago
  I never knew that running an interactive program in my terminal would absolutely rinse my CPU and battery but that's what Claude, OpenCode and Ghostty have colluded to achieve. Even when the laptop is asleep overnight it's practically melting. I'm sure there was some logical reason for shoehorning web technology into this stack given that we have a good 40 years or so of experience with interactive terminal programs that use curses/ncurses, alongside emacs, vim, almost the entirety of MS-DOS, and so on.
  - deleted 3mo ago
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  - senderista 3mo ago
    Why are you implicating ghostty? Have you compared its CPU usage to any other terminal?
    - agrippanux 3mo ago
      I don't know if its still the case anymore since 1.3 but Ghostty did have a documented issue with Claude causing resource issues.
    - tdhz77 3mo ago
      I think the author is saying everything that touches llm.
preommr 3mo ago
I love bun - although disliked how Jarred did the conversion. Project-wise, nothing has changed. Bun was always great because of the fantastic dx - it was just really easy to use , with stuff like out of the box typescript (unreal that it took so long for node, and it's behind a super long flag, wtf...). And it didnt have the weirdness of deno, it maintained backwards compatability with node api, and it just worked. But it was never stable. You'd have to be fool to believe that a single project could stably do everything bun covers. It's always been an insane project. It was built on top of zig, a langauge that hasn't reached 1.0, and is constantly changing, and throw in how he was rewriting his own custom zig stuff. Like c'mon, let's apply some common sense here. For me, little has changed. I am still going to use bun as a nice dev tool, and use node for production.
hmokiguess 3mo ago
pi runs in TypeScript and I like it, the target language of the tool, for me, matters only such that I can extend it. I like writing extensions, plugins, things, in TypeScript so I'm cool with that! Claude Code is closed source, doesn't let me extend it beyond hooks, and these I write in bash anyways. That all said, why should I bother about this change? Feels like a nothing burger to me, as an end user. This should matter more for those that are internal to Claude Code and Bun developing it.
marsven_422 3mo ago
[dead]
delegate 3mo ago
I'm looking at this situation strictly as 'What's possible today'. If a 1M lines code rewrite from one language to another goes into production in 1 month, that's a very strong signal that the models are now insanely capable. My anxiety before merging a 2K lines PR is greatly reduced after 3 frontier models (Fable, 5.6 and kimi K3) finds no issues in it. Just 6 months ago (Opus 4.6) this was not true, a big PR would have countless number of issues. Aside from the human drama, the message to all of us is - these things are ready for whatever your imagination can throw at them. I think that's exactly what Anthropic wanted to communicate.
- rzmmm 3mo ago
  It was not really a traditional rewrite. More like transpilation. Still impressive
- dgellow 3mo ago
  > Aside from the human drama, the message to all of us is - these things are ready for whatever your imagination can throw at them. …if you have the compute and capital to run that whole agentic system
throwatdem12311 3mo ago
I despise this era we live in. Pushing rewrites like this upon millions of users, when the Bun rewrite has countless known issues and is likely a security nightmare. Every time I ‘brew outdated’ and I see a wall of updates I die a little inside knowing that most of this code has not been verified or even looked at. Yet we hear about massive supply chain attacks pretty much every week now and we’re still full steam ahead on this vibe coded nightmare. God help us. Claude Code in particular updates sometimes multiple times per day. Like I’m sorry but there is no way all this nonsense is safe.
zuzululu 3mo ago
as it always should've been Rust was the right move
larodi 3mo ago
Ok, so let me wrap this for everyone: While everyone here in this forum kept arguing (and fighting and yelling at each other) whether tis moral/right/secure/cheap for ppl to rewrite and ship a major software package with LLMs/agents, one of the main drivers behind AI actually did it, without consulting your opinion, and most same everyone actually slurped this decision without paying a a notice. Boring is good, but this boring is super massive major thing that happened, and precisely because security is still intact.
- deleted 3mo ago
  [deleted]
luciana1u 3mo ago
[flagged]
jason_s 3mo ago
TIL about Bun.
lykahb 3mo ago
Is it easier to rewrite Bun than it is to rewrite Claude?
mrothroc 3mo ago
Drilling into the original article where Jarred explained the reasoning behind the change, It's pretty clear that under zig the team was doing things by hand that are automatic in rust. Humans and agents share one thing: they are both non-deterministic. He talks about the issue of tracking memory lifecycles manually in zig so it can be explicitly freed. As expected, this leads to a long list of bugs where people missed things. Rust does this automatically. It removes an entire class of errors from his backlog. From an engineering management perspective, this looks like a pretty good trade. The bonus here is that compiler errors are exactly the kind of deterministic guardrail you need to put around coding agents. Claude works really well if you give it a way to test for correctness and "make it compile" is a pretty good target. There's a general version of this: the artifact you expose plus the test you run on it. Deterministic tests turn stochastic output into a hard guarantee. Wrote it up here if useful: https://michael.roth.rocks/blog/verification-surface/ https://michael.roth.rocks/blog/verification-surface/
- awesan 3mo ago
  Zig (like C) is simply not a good language to use if you're going to do many small allocations with uncorrelated lifetimes. To write robust Zig (or C) code, you must manage lifetimes yourself, for example by grouping allocations on an arena or by having fixed buffers of "things". You can just do that, and then Zig is really no less robust than Rust. But if you want to do "managed language" style allocation patterns (like what llms generally prefer), it doesn't make sense to use it.
  - mrothroc 3mo ago
    [dead]
  - hugmynutus 3mo ago
    This reads like cope because you're re-inventing RAII from first principles. I cannot take this seriously as tutorials on robust Zig Allocation Pools will store a deinit method for each item within the pool, so when the pool deinits, all internal objects can be deinit'd. That is just RAII & dtors from first principles, except with extra overhead of manually storing fat pointers yourself (and the bugs that come with this). Instead of using a language with builtin guarantees & optimizations around handling this so your object pools don't need to carry around a bunch of function pointers. C++ has aggressive de-virtualization passes so at runtime a lot of the 'complex object hierarchies' can be flattened to purely static function calls.
23951276 3mo ago
Basically Anthropic can ship any trojan in underhanded Rust to any target because it is not possible to audit 1M lines of slop. And the crowd is cheering.
rekttrader 3mo ago
They’re just wildly successful terrible engineers who can describe problems well and have unlimited token budgets. If they were paying for their own token use, the software would be better, they simply don’t have financial incentive to be more performant. A dirty secret of AI data centers are that they’re only getting 40-60% efficiency out of their GPU clusters and because the moneygun go brrrrr they just buy more. You wonder why they’re so afraid of the Chinese competition… they can’t afford to be as wasteful
- DWe1 3mo ago
  Describing problems well may be one of the most important skills an engineer can have.
dranan 3mo ago
[flagged]
steveiliop56 3mo ago
Ah so that's why it has been crashing constantly for me.
harrisi 3mo ago
Maybe I'm taking crazy pills, but I swore there have been very similar comments I've seen as the current top post by weakfish: > 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. It turns out, there's some similar sentiments in the last year ish: https://news.ycombinator.com/item?id=47043325 https://news.ycombinator.com/item?id=47043325 https://news.ycombinator.com/item?id=47105720 https://news.ycombinator.com/item?id=47105720 https://news.ycombinator.com/item?id=48001113 https://news.ycombinator.com/item?id=48001113 https://news.ycombinator.com/item?id=46134570 https://news.ycombinator.com/item?id=46134570 https://news.ycombinator.com/item?id=46124596 https://news.ycombinator.com/item?id=46124596 I'm not a fan of any of the technologies, companies, or people related to this. I just couldn't shake the feeling that I've seen similar comments. September and all.
- harrisi 3mo ago
  I don't want to edit this to change the narrative, but I wanted to clarify that I'm not not a fan of all of the technologies or people related to this. As far as compan{y,ies} go, though, well..
- vdfs 3mo ago
  Maybe because the 1st thing any experienced technical person would think about? It's like rebuilding and optimizing the racing track to make F1 run faster.
  - harrisi 3mo ago
    Perhaps. The thing I was trying to highlight more is comments (particularly disapproving ones) about the intersection of JavaScript (especially React, apparently), TUIs, and LLMs. I just thought it was interesting. I'm a fan of TUIs, both positive and negative about JavaScript (the modern language is quite nice, given you avoid the historical warts, in my opinion - the ecosystem is unfortunate), and I think the best description for how I feel about LLMs is that I'm bearish. Also Simon is a fantastically prolific and intelligent person though, even though LLMs are not my cup of tea. https://news.ycombinator.com/item?id=48960912 https://news.ycombinator.com/item?id=48960912 is a recent comment by someone I also respect related to how LLMs recreate human-like content (Widgets, really), making actual human-created content feel fake. Sometimes it sure does feel like ELIZA is the main news source these days.
molmos 3mo ago
[flagged]
Debo_Jolaosho 3mo ago
For real
LAC-Tech 3mo ago
Has all of this drama turned anyone else a bit sour on bun? I have a long running side project I migrated to bun, and I'm starting to regret it. I don't want to build on top of this much churn.
forrestthewoods 3mo ago
It’s interesting that Bun was a human rewrite from Go to Zig. (I think?). Then rewritten from Zig to Rust. AI is pretty good at rewrites and ports. Quite good infact.
effnorwood 3mo ago
My perl re-write is not very good.
deleted 3mo ago
[deleted]
globalnode 3mo ago
at this point im declaring any "rewritten in X" articles as trolling lol.
jgbuddy 3mo ago
Why even write Claude code in JavaScript at that point, assuming they write the application logic in node and also include the interpreter in the application?
- snek_case 3mo ago
  Probably because the team lead is a web developer, and whatever he says goes. Companies are typically very hierarchical, even if they like to claim otherwise.
512colors 3mo ago
you know what i hate? i hate that each update, to codex or claude code, it seems like they're always trying to "hide stuff" , reminds me of the 80s and 90s when tech assumes normal people are too stupid to see 'raw' stuff like terminal commands being run, its always been like that, less so now, but i get so mad when its doing stuff, and i can't see if its deleting files or just screwing something up. btw this is totally free tool buttonscli.com that is a full UI terminal app but its got a button for agent control. You click that, paste into claude code or w/e/any agent, and it'll use that for the terminal commands instead of the built in one so you can see everything (and it can open 10 tabs if it wants, you see them all)
NodesHub 3mo ago
[flagged]
the_black_hand 3mo ago
I'm stupid and clearly too stupid to google too. Is bun simply a better nodejs? Assuming it true that all of Claude code is now written by AI, why would AI care about using bun over node?
psyclobe 3mo ago
[flagged]
- tomhow 3mo ago
  Please don't. We detached this comment from https://news.ycombinator.com/item?id=48970444 https://news.ycombinator.com/item?id=48970444 and marked it off topic.
arikrahman 3mo ago
Why not just use Deno that's made in Rust and also has safety in mind?
- quikoa 3mo ago
  How will Anthropic be able to rewrite that in Rust and use it for marketing?
- IshKebab 3mo ago
  Yeah I'm also wondering what the point of Bun is when Deno already exists. Especially since it added Node compatibility. Genuine question, why should anyone use Bun if they're already using Deno?
m_bashirzadeh 3mo ago
[flagged]
skumar5190 3mo ago
[flagged]
Saba-Ba 3mo ago
It was an intersting case. Watched a youtube video about this and discussion from zig founder and bun was a little weird.
deleted 3mo ago
[deleted]
feiz45607 3mo ago
[flagged]
foldr 3mo ago
Is anyone else failing to understand all the internet drama surrounding this? The rewrite may work out on a technical level or it may not. Let's wait and see. The Bun project did not swear a blood oath to use Zig forever, and it's ultimately their choice to switch to a different programming language. Beyond that, people seem to be incredibly emotionally involved with this, for reasons that entirely escape me.
silverlemontea 3mo ago
[flagged]
overgard 3mo ago
Oh good, the vibe coded prompt injection vector that casually accesses things in my home directory without permission is running on a vibe coded prerelease runtime using lots unsafe rust. What could go wrong?
Unified-Mentor 3mo ago
[dead]

608 points by tosh 3mo ago

> 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 to it. What is the governance structure for Bun by the way? Couldn't find any documents/explanations about how it's supposed to work. I'm guessing it's essentially just "Anthropic decides what gets done and accepted" today?

minraws 3mo ago
It's largely just what jarred is willing to accept this week afaik or not, and they did put the bun 1.4.0 version bump in the changelogs for claude code a while ago, over a month almost. Though most will be forgiven to not reading it since well it's all AI anyways. I don't know how I feel about all this yet, maybe someday.. ooof
- jdiff 3mo ago
  > they did put the bun 1.4.0 version bump in the changelogs for claude code a while ago, over a month almost. Where? Is see no CHANGELOG in the root. I do see LATEST, last modified 2 months ago, and it says 1.3.14
  - simonw 3mo ago
    The Claude Code release notes. Not the Bun release notes: https://github.com/anthropics/claude-code/releases/tag/v2.1.181 https://github.com/anthropics/claude-code/releases/tag/v2.1.... > Upgraded the bundled Bun runtime to 1.4 (Though that doesn't clarify that this is the Rust rewrite)
junon 3mo ago
Why does changing to Rust kill the project? I don't understand the point here.
- pjmlp 3mo ago
  Definitely, it was a possible reason why Zig actually matters in the industry. Now it is a Deno clone, both without anything enticing over node.js.
- Cthulhu_ 3mo ago
  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).
  - gipp 3mo ago
    I don't think the GP had anything to do with the language change itself. More that it marks a clear point of Anthropic taking ownership and governance of the project in a less open direction.
  - flohofwoe 3mo ago
    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 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).
    - realo 3mo ago
      I read your link, written by Bun's author and totally get his thinking. In the current world of cyber weaknesses everywhere, infrastructure must be solid and rust is a better choice than zig for something like bun. In other words, bun is not a demo of zig programming that happens to do useful things. Bun does useful things, and must do them securely. That is its number one priority, language is secondary, inasmuch as it helps doing useful things securely.
deleted 3mo ago
[deleted]
ranguna 3mo ago
The PR is public, you can build and use it as well. The anthropic team just decided to use it, and you can as well.
- embedding-shape 3mo ago
  > The PR is public I'm talking about the 1.4.0 release: > Claude supports them shipping a preview of a not-yet-released Bun version Maybe Bun/Anthropic fixed this after Simon's initial release of the blog post, but seemingly when we both looked, it wasn't public.
  - thevinter 3mo ago
    > Update: The Rust version has been released as Bun canary - running bun upgrade --canary will install this release.)
    - embedding-shape 3mo ago
      Yeah, of course Anthropic making the version publicly available AFTER people notice it wasn't public, completely solves the issue ;)
      - simonw 3mo ago
        Anthropic changed nothing since I wrote published this post a few hours ago - I updated my post to mention Bun canary since it was a point of confusion here on Hacker News.
        nicce 3mo ago
        Claude Code has shipped Bun 1.4. already more than month ago: https://github.com/anthropics/claude-code/releases?q=bun&expanded=true https://github.com/anthropics/claude-code/releases?q=bun&exp... Version was changed in Bun in May 18 https://github.com/oven-sh/bun/commit/b18bf6d1d0a92238f240bfd125f0e3b3461b9243 https://github.com/oven-sh/bun/commit/b18bf6d1d0a92238f240bf... So it has been canary since then, most likely, if docs are accurate that latest main is canary.
TheRoque 3mo ago
I had "investigate if bun is worth it" too, and decided not to use it, but instability was one of the reasons. So it feels it was the right move.

baq 3mo ago

Turns out it was just a build step after all.

kburman 3mo ago

Honestly, I initially thought rewriting an entire codebase with AI would be a huge mistake. After reading this, I'm starting to think I was wrong. 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. Today's AI-generated rewrites may not produce code that humans would consider high quality or maintainable. But I'm beginning to wonder whether that will even matter in a few months. If AI is the primary consumer, maintainer, and refactorer of code, human readability becomes far less important than correctness, performance, and the ability to iterate. This feels like a shift where software may no longer exist as a long-lived artifact in its current form. Instead of writing and maintaining applications for years, we may generate, adapt, and discard them continuously for each use case.

sdevonoes 3mo ago
We are the ones to get to decide. Do we want that? I don’t. But im just a single data point
rho138 3mo ago
That sounds like a massive waste of finite energy and compute resources.
- CrimsonRain 3mo ago
  That's like saying let's stay with horses. We'll develop faster and better tech. We'll find resources to feed that. Use that to build better. Access better resources. We'll mine asteroids. We'll harness much more from the sun. The factory must grow.
  - rho138 3mo ago
    Is that before or after the earths atmosphere acidifies for humans and our bodies can’t hold enough phosphorus or calcium for basic metabolic tasks? You have until 2050: https://doi.org/10.1007/s11869-026-01918-5 https://doi.org/10.1007/s11869-026-01918-5

gabrieledarrigo 3mo ago

Bah. Personally my take on the entire affair is quite negative, whatever Jarred or Simonw says about it. I think Bun owned by Anthropic and the entire rewrite with AI is not the real point (even if it's quite interesting, though). My take is that Jarred, and Bun,didn't demonstrate a serious, adult approach, from "this is my branch, you are overreacting" message to just proceeding with a 1mil+ PR merged in less than month. The communication is the issue, and it was handled very badly, in a way that impacted trust and divisions. Was it so difficult to adopt the approach that the TS team adopted for 7.0?

baq 3mo ago
I guess the point is none of it matters, CC users didn't notice or don't care except an exceptionally small minority.
- deleted 3mo ago
  [deleted]
- ai_fry_ur_brain 3mo ago
  [dead]
- snemvalts 3mo ago
  The lowest of the bars
  - drodgers 3mo ago
    But the only one that matters? Seems like this is delivering business value.
conartist6 3mo ago
Haha TS7 is the next biggest example of, "Let's just do a line by line port to another language instead of seriously examining our architecture"
- 3mo ago

bel8 3mo ago

Contrary to many, I have high hopes that Jarred and team will lapidate the ported codebase and it will continue to flourish as an open source project.

znpy 3mo ago

> 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.

IshKebab 3mo ago
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.
ifwinterco 3mo ago
It was already written in a very performant language so no significant performance improvements should be expected. The benefit of a rust rewrite is memory safety improvements, but currently they've just rewritten zig to unsafe rust so they don't have that either yet
voiper1 3mo ago
The blog claims rust chosen mainly to address memory issues, which rust is a better language for. So, success would simply be less new memory errors / easier to patch old ones.
- marcindulak 3mo ago
  Claude installer/updater had a high memory usage problem (Gigabytes of resident memory used during a fresh installation of Clade with it's native install.sh script, or during a claude update). This was reported as early as December 2025, see https://github.com/anthropics/claude-code/issues/12327#issuecomment-3614767879 https://github.com/anthropics/claude-code/issues/12327#issue.... The latest Claude installer (2.1.215) possibly does not have it anymore https://github.com/anthropics/claude-code/issues/4953#issuecomment-5015922958 https://github.com/anthropics/claude-code/issues/4953#issuec..., but more tries on various machines are needed to confirm that.

ooofydoofy 3mo ago

bun upgrade --canary you are welcome

deleted 3mo ago
[deleted]

reddalo 3mo ago

Damn, I should have not migrated to Bun. Should I revert back to Npm?

cromka 3mo ago
I am getting into the frontend dev and one thing that I don't understand is why people use bun in the first place? It's not much better preforming, it's not much safer, it's still not 100% compliant. Some tests show it's actually slower than node. Why bother switching, then?
- johnny22 3mo ago
  i assume it's because of all the built in tooling that node doesn't ship with.
- awestroke 3mo ago
  Faster package manager Faster startup Typescript support out of the box Better stdlib than node Stdlib includes yaml, sqlite etc so you need to pull in fewer deps, so you can avoid the left-pad/is-even node_modules explosion problem to a greater extent
  - fg137 3mo ago
    Can't comment on others, but new Node.js also has typescript out of the box and works pretty well.
- vips7L 3mo ago
  I don’t think you would use Bun for front end.
  - frollogaston 3mo ago
    That's what Claude Code does at least
  - cromka 3mo ago
    I mean, Astro on Bun?

IshKebab 3mo ago

This post is just "they didn't lie"...

deleted 3mo ago

[deleted]

marsven_422 3mo ago

[dead]

thrance 3mo ago

Yeah, I noticed. I had Claude write a quick JS script for me a few days ago, it then tried to use Bun to run it. When it couldn't find it, it tried to install it with `sudo pacman`. I had to fucking tell it to use Node instead.

maverickaayush 3mo ago

I've been using Claude Code daily for a fairly large FastAPI project and didn't notice anything unusual around that timeframe. If this really was the Rust runtime underneath, "boring is good" seems like the right outcome.

rs_rs_rs_rs_rs 3mo ago

It is absolutely amazing to me that this ai rewrite work so well, maybe claude is not really that much of a complicated tool to stress the bun runtime but still...

jqbd 3mo ago
It works well because they had tests, they could compare before and after. Likelihood of issues especially if you transpile to a safer language should be minimal.

luciana1u 3mo ago

[flagged]

feverzsj 3mo ago

It's a transpile. And not even a good one. The generated code is far from idiomatic rust. Some may consider it an abomination.

alexandra_au 3mo ago
grep -nr 'unsafe' . Is all you need to know to consider how much of an abomination it is
- simonw 3mo ago
  This comment inspired me to take a look at the trend of "unsafe" in the Bun code over time since the rewrite PR first landed - here are the commits where that number changed by at least 10: 2026-05-14 23427db 13907 2026-05-14 19d8ade 13861 2026-05-15 4d443e5 13840 2026-05-17 172afa5 13803 2026-05-17 80a06a8 13849 2026-05-18 fba43af 14026 2026-05-19 303cd28 14052 2026-05-20 21db682 14243 2026-05-22 a06a00a 14239 2026-05-23 49c97de 14090 2026-05-28 472a06a 14076 2026-06-01 a0d1472 14071 2026-06-04 8553428 14032 2026-06-09 717542f 14053 2026-06-10 1c90e5a 14043 2026-06-11 6e91d24 14031 2026-06-16 bd8edc7 14086 2026-06-17 6ef5977 14104 2026-06-20 315ed50 14106 2026-06-22 c6be834 14120 2026-06-23 ea7e44f 14108 2026-06-23 03042ab 14128 2026-06-29 86d32c8 14046 2026-07-01 6640fcf 14077 2026-07-04 51074e3 14099 2026-07-06 9d0e93d 14186 2026-07-08 ab6eb2d 13953 2026-07-09 86caf6e 13936 2026-07-10 91675d0 13930 2026-07-13 73b6c14 13951 2026-07-16 4bbe075 13978 2026-07-16 57e30a5 13995 So not as much cleanup as I had expected! ChatGPT written script for counting here: https://gist.github.com/simonw/b1015bcadcedd1a781cedb7af9cbb2d0 https://gist.github.com/simonw/b1015bcadcedd1a781cedb7af9cbb...
- rwz 3mo ago
  The original code was one giant unsafe block with almost no tangible way to find or debug all the subtle memory bugs and leaks they had. Now it's smaller, faster and has fewer bugs. Also its every potential memory issue is neatly annotated by an unsafe block so you can go and refactor them out one by one with confidence. All this seems like a pretty huge improvement to me. Why is this an abomination in your eyes?

deleted 3mo ago

[deleted]

deleted 3mo ago
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aureate 3mo ago

The port of Bun, which has >5000 open github issues, is used in Claude Code, which has >11000 open github issues. Do people use Bun in things that are expected to work reliably? Have any such projects tried the upgrade yet?

ivanjermakov 3mo ago
11k in two years vs 5k in two weeks? You're right, numbers speak for themself.
- entrope 3mo ago
  Did Bun mass-close issues that predated the rewrite? It doesn't look like they did, as the oldest open issue is from 2021 and there are many from 2022, but maybe they did something that killed most of the old issues.
  - endospore 3mo ago
    Their (public) project management is horrible, you can find fixed issues unclosed and unfixed issues closed. Not really surprising when that part of the work is completely taken over by LLM agents though.
zahlman 3mo ago
To be fair, https://github.com/python/cpython https://github.com/python/cpython has over 5k open github issues, and that's still generally considered fairly reliably technology even if a lot of HN users seem to hate it.
- aureate 3mo ago
  It's not a great way of inferring software quality, but I think the numbers for both Bun and Claude Code are pretty bad. cpython has ~7,000 open issues, but ~70,000 closed ones, a 1:10 ratio. Bun's ratio is above 1:2.5, while for Claude Code it's slightly over 1:6. Much more importantly, though, Bun's oldest issue is from Sep 2021, while Claude Code's is Feb 2025. cpython's oldest issue dates from June 2000 (presumably migrated from an older tracker). Claude Code has very nearly the same total number of issues (open + closed) as cpython at around 77,000, but Claude Code has done it in a year an a half whereas cpython has taken 26 years to get there. It's a good comparison to pick, as it can't be explained by popularity. For all the real-world use Claude Code sees, it's nowhere near what cpython sees, even over the year and a half in question. Bun, meanwhile, is hitting these numbers while not even being the mainstream choice for what it does (node still holds that crown afaik).

witx 3mo ago

What is the actual contribution and motivation of this post?

simonw 3mo ago
I thought it was interesting. I didn't write this with Hacker News in mind. (I was actually half way through writing about something related, when I thought it would be interesting to see if I could prove that I had the Rust version of Bun on my laptop already.)
owebmaster 3mo ago
[flagged]
- deleted 3mo ago
  [deleted]
- tomhow 3mo ago
  Please don't attack people on HN, even with vague insinuations. The guidelines ask: Please don't post insinuations about astroturfing, shilling, brigading, foreign agents, and the like. It degrades discussion and is usually mistaken. If you're worried about abuse, email hn@ycombinator.com and we'll look at the data. https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html
softwaredoug 3mo ago
People shouldn’t overthink blog posts. Just write what’s on your mind and have fun.
- rvz 3mo ago
  The motivation is obviously clear. No-one would be doing that for fun 24/7, only covering about AI and nothing else without getting paid for it. If anyone else did that on HN, they would be accused of slop with their domain blacklisted.

tappaseater 3mo ago

Anthropic bought Bun, so they kinda, sorta had to make this work. I am sure the cost at $145,000 in Claude time will get some attention. I am curious how this will work going forward from FOSS perspective. Will humans be allowed to modify the generated code? Only the .md prompts for the agents? Or what?

codethief 3mo ago

Incidentally, Claude Code has been very buggy for me lately (much more so than before). Lots of TUI rendering issues causing, e.g., the conversation history to be garbled etc.

PsylentKnight 3mo ago
Every time I resize my window now, the output is completely garbled. I often have to ask it to repeat itself just so I can see what it just said. This isn’t a new thing, but it feels like it’s gotten worse. This is on Windows
- LambdaComplex 3mo ago
  Does exiting following by resuming the session fix it?
- anematode 3mo ago
  Same observation. One thing you can do is close out the session and `claude --resume`
kilroy123 3mo ago
I'm far from being anti-AI, but these guys take it way too far IMO. It's straight-up AI slop. Like a real engineer still needs to be in the loop and drive the tool. Anthropic seems to be all in on 100% AI code.
NateEag 3mo ago
I've been (grudgingly) using Claude since February. When I started, I discovered to my shock that it was by far the worst TUI I had ever touched. Rendering glitches, keyboard input screwups, and just all-around jankiness. Despite that awful baseline, I have to agree that it's gotten noticably worse in the past week or so. It's started mangling my terminal sessions somehow, so that not all characters I input are visible in the UI. Backgrounding it, doing a 'reset', then re-foregrounding seems to fix it. Of course when I asked it to diagnose the problem, it assured me that Claude has no such big and it must be something else I'm running. All I'm running is tmux and Claude, though, and the behavior surfaced while I was running Claude. So, yeah - if they just recently updated Claude to use the Rust rewrite, this increased crappiness might actually be due to that. It does seem to at least roughly correlate.

deleted 3mo ago

[deleted]

lazzlazzlazz 3mo ago

[flagged]

nottorp 3mo ago

So does that make Claude Code any better? Can you select text with shift + arrow keys now in the command line client? :)

softwaredoug 3mo ago

Whatever the headaches of the internals, I haven’t heard any substantive outcomes in hacker news that have been impacted by this change. Yes if we had a Zig->Rust transpiler maybe it would produce similar output. But I can’t find one. We’d have to use an agent to build one first :)

nirui 3mo ago

All the emotion of speculations aside, how it runs? It boots faster yeah, but what about RAM and CPU usage? Weird dead loop or dead locks? If it run as good as before or even better, then that's kinda impressive. I'm a developer so I really don't like it when AI might took my job, but if everyone on this planet could create a software for themselves exactly as how they wanted with just a few simple demands, that will change the world for the better. Think of it as a democratization of technology. You don't want Microsoft stealing your data? Just ask a AI to write an OS for you. You don't want Google to listen to what you're saying? Just ask a AI to design a phone for you. If one day the AI ended up doing that, it will be the ultimate technology self-sufficient. In front of that, your job security is insignificant. It is also why keeping the tech open source is that much important. Otherwise, it's still the same old shit again and again, and, you lose your job too.

phinnaeus 3mo ago
> I'm a developer Then you must know that the hardest part of software development is getting clear requirements... > everyone on this planet could create a software for themselves exactly as how they wanted Even with perfect AGI this will never happen because people will never be able to express clear requirements
- William_BB 3mo ago
  It's not even about requirements. It's about responsibility. Someone has to take responsibility for the code and the product. Someone has to hotfix a bug that's costing millions of dollars an hour and someone has to be blamed for a bug that's consting millions of dollars an hour.
  - godwinson__4-8 3mo ago
    Not really. The secret of our society is it wouldn't work if people with a controlling interest in things ever faced personal responsibility. Who got blamed for the Iraq war? How much did that cost? The theory is if you tried to blame someone then some future president wouldn't be able to declare war. You don't know how the law works apparently. Corporate law is pretty much the same. The economy doesn't boom if CEOs can actually be blamed for things. You don't blame a "someone" that's what incorporation does. If some code does a booboo just put a $ amount on it, withdraw the funds and move on. The media will focus on the humans because of the drama, but they are largely irrelevant. It doesn't come out of their pockets. A human is already window dressing in this status quo. A LLM has no reason to do the sorts of things that violate such legal protections, be it of a president (none really apply) or a CEO (good luck getting a CEO to take personal responsibility for anything short of outright fraud). If it suddenly goes haywire the law already has a concept of vis major. The secret is individual humans are already largely irrelevant to our society. That's how we got here. The trend will only continue.

hkclawrence 3mo ago

[dead]

Aeveus 3mo ago

Anecdotal, but I’ve been getting segfaults in Claude Code. I run inside Kitty tabs, and the entire tab becomes unusable when this happens. No response to inputs at all from that point. When this happens, a link shows up to report the issue. It’s not clickable (likely due to the segfault), and perhaps more important: it’s encoded, so you can’t see what you would be sending in your report. Hope it gets better.

mort96 3mo ago
What makes you think it's a segfault? Does your shell print "Segmentation fault"? If so, you should be back at your shell and you should be able to recover the tab by typing 'reset' + enter (even if you can't see anything as you're typing it). If nothing prints "Segmentation fault", this just sounds like a hang
- javawizard 3mo ago
  I just had this happen today. It was indeed a segfault. From what I could tell it looked like it was in JS code that had been JIT compiled. I haven't attempted to troubleshoot further beyond setting all my future Claude Code instances to pipe their stderr to disk so that I don't lose the stack trace next time.
  - kccqzy 3mo ago
    Bun does not have its own JIT compiler. Bun uses JSC made by Apple. So your blame should be directed to Apple. And I can believe you because I’ve seen JavaScript-heavy Safari tabs crash.
MitziMoto 3mo ago
Something similar has been happening to me with Ghostty, but there is no error message or link and it only happens when Claude uses it's interactive questions interface. It becomes completely unresponsive to any input except scrolling. I can't select options or even cancel out. (I am in no way implying this is related to Bun)
3mo ago

bikeshedpelicun 3mo ago

[flagged]

simonw 3mo ago
Did you create a burner account just to accuse me of bikeshedding Bun's release tag process?

roundabout-host 3mo ago

I have a better idea: convert it to a prompt and commit the prompt to the repository. Then Mythos will be your compiler.

iririririr 3mo ago
the whole Ai skit is anthropomorphing the compiler as a coworker.

GuB-42 3mo 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?

jeremyjh 3mo ago
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.
- 59nadir 3mo ago
  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.
tbrockman 3mo ago
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.
- ozozozd 3mo ago
  So they had to rewrite Bun instead of Claud Code because they “already had bought Bun.” This thread is filled with non-sequiturs.

weakfish 3mo ago

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.

deadbabe 3mo ago
Should have done it in C++ with SDL3.
ljm 3mo ago
I never knew that running an interactive program in my terminal would absolutely rinse my CPU and battery but that's what Claude, OpenCode and Ghostty have colluded to achieve. Even when the laptop is asleep overnight it's practically melting. I'm sure there was some logical reason for shoehorning web technology into this stack given that we have a good 40 years or so of experience with interactive terminal programs that use curses/ncurses, alongside emacs, vim, almost the entirety of MS-DOS, and so on.
- deleted 3mo ago
  [deleted]
- senderista 3mo ago
  Why are you implicating ghostty? Have you compared its CPU usage to any other terminal?
  - agrippanux 3mo ago
    I don't know if its still the case anymore since 1.3 but Ghostty did have a documented issue with Claude causing resource issues.
  - tdhz77 3mo ago
    I think the author is saying everything that touches llm.

preommr 3mo ago

I love bun - although disliked how Jarred did the conversion. Project-wise, nothing has changed. Bun was always great because of the fantastic dx - it was just really easy to use , with stuff like out of the box typescript (unreal that it took so long for node, and it's behind a super long flag, wtf...). And it didnt have the weirdness of deno, it maintained backwards compatability with node api, and it just worked. But it was never stable. You'd have to be fool to believe that a single project could stably do everything bun covers. It's always been an insane project. It was built on top of zig, a langauge that hasn't reached 1.0, and is constantly changing, and throw in how he was rewriting his own custom zig stuff. Like c'mon, let's apply some common sense here. For me, little has changed. I am still going to use bun as a nice dev tool, and use node for production.

hmokiguess 3mo ago

pi runs in TypeScript and I like it, the target language of the tool, for me, matters only such that I can extend it. I like writing extensions, plugins, things, in TypeScript so I'm cool with that! Claude Code is closed source, doesn't let me extend it beyond hooks, and these I write in bash anyways. That all said, why should I bother about this change? Feels like a nothing burger to me, as an end user. This should matter more for those that are internal to Claude Code and Bun developing it.

marsven_422 3mo ago

[dead]

delegate 3mo ago

I'm looking at this situation strictly as 'What's possible today'. If a 1M lines code rewrite from one language to another goes into production in 1 month, that's a very strong signal that the models are now insanely capable. My anxiety before merging a 2K lines PR is greatly reduced after 3 frontier models (Fable, 5.6 and kimi K3) finds no issues in it. Just 6 months ago (Opus 4.6) this was not true, a big PR would have countless number of issues. Aside from the human drama, the message to all of us is - these things are ready for whatever your imagination can throw at them. I think that's exactly what Anthropic wanted to communicate.

rzmmm 3mo ago
It was not really a traditional rewrite. More like transpilation. Still impressive
dgellow 3mo ago
> Aside from the human drama, the message to all of us is - these things are ready for whatever your imagination can throw at them. …if you have the compute and capital to run that whole agentic system

throwatdem12311 3mo ago

I despise this era we live in. Pushing rewrites like this upon millions of users, when the Bun rewrite has countless known issues and is likely a security nightmare. Every time I ‘brew outdated’ and I see a wall of updates I die a little inside knowing that most of this code has not been verified or even looked at. Yet we hear about massive supply chain attacks pretty much every week now and we’re still full steam ahead on this vibe coded nightmare. God help us. Claude Code in particular updates sometimes multiple times per day. Like I’m sorry but there is no way all this nonsense is safe.

zuzululu 3mo ago

as it always should've been Rust was the right move

larodi 3mo ago

Ok, so let me wrap this for everyone: While everyone here in this forum kept arguing (and fighting and yelling at each other) whether tis moral/right/secure/cheap for ppl to rewrite and ship a major software package with LLMs/agents, one of the main drivers behind AI actually did it, without consulting your opinion, and most same everyone actually slurped this decision without paying a a notice. Boring is good, but this boring is super massive major thing that happened, and precisely because security is still intact.

deleted 3mo ago
[deleted]

luciana1u 3mo ago

[flagged]

jason_s 3mo ago

TIL about Bun.

lykahb 3mo ago

Is it easier to rewrite Bun than it is to rewrite Claude?

mrothroc 3mo ago

Drilling into the original article where Jarred explained the reasoning behind the change, It's pretty clear that under zig the team was doing things by hand that are automatic in rust. Humans and agents share one thing: they are both non-deterministic. He talks about the issue of tracking memory lifecycles manually in zig so it can be explicitly freed. As expected, this leads to a long list of bugs where people missed things. Rust does this automatically. It removes an entire class of errors from his backlog. From an engineering management perspective, this looks like a pretty good trade. The bonus here is that compiler errors are exactly the kind of deterministic guardrail you need to put around coding agents. Claude works really well if you give it a way to test for correctness and "make it compile" is a pretty good target. There's a general version of this: the artifact you expose plus the test you run on it. Deterministic tests turn stochastic output into a hard guarantee. Wrote it up here if useful: https://michael.roth.rocks/blog/verification-surface/ https://michael.roth.rocks/blog/verification-surface/

awesan 3mo ago
Zig (like C) is simply not a good language to use if you're going to do many small allocations with uncorrelated lifetimes. To write robust Zig (or C) code, you must manage lifetimes yourself, for example by grouping allocations on an arena or by having fixed buffers of "things". You can just do that, and then Zig is really no less robust than Rust. But if you want to do "managed language" style allocation patterns (like what llms generally prefer), it doesn't make sense to use it.
- mrothroc 3mo ago
  [dead]
- hugmynutus 3mo ago
  This reads like cope because you're re-inventing RAII from first principles. I cannot take this seriously as tutorials on robust Zig Allocation Pools will store a deinit method for each item within the pool, so when the pool deinits, all internal objects can be deinit'd. That is just RAII & dtors from first principles, except with extra overhead of manually storing fat pointers yourself (and the bugs that come with this). Instead of using a language with builtin guarantees & optimizations around handling this so your object pools don't need to carry around a bunch of function pointers. C++ has aggressive de-virtualization passes so at runtime a lot of the 'complex object hierarchies' can be flattened to purely static function calls.

23951276 3mo ago

Basically Anthropic can ship any trojan in underhanded Rust to any target because it is not possible to audit 1M lines of slop. And the crowd is cheering.

rekttrader 3mo ago

They’re just wildly successful terrible engineers who can describe problems well and have unlimited token budgets. If they were paying for their own token use, the software would be better, they simply don’t have financial incentive to be more performant. A dirty secret of AI data centers are that they’re only getting 40-60% efficiency out of their GPU clusters and because the moneygun go brrrrr they just buy more. You wonder why they’re so afraid of the Chinese competition… they can’t afford to be as wasteful

DWe1 3mo ago
Describing problems well may be one of the most important skills an engineer can have.

dranan 3mo ago

[flagged]

steveiliop56 3mo ago

Ah so that's why it has been crashing constantly for me.

harrisi 3mo ago

Maybe I'm taking crazy pills, but I swore there have been very similar comments I've seen as the current top post by weakfish: > 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. It turns out, there's some similar sentiments in the last year ish: https://news.ycombinator.com/item?id=47043325 https://news.ycombinator.com/item?id=47043325 https://news.ycombinator.com/item?id=47105720 https://news.ycombinator.com/item?id=47105720 https://news.ycombinator.com/item?id=48001113 https://news.ycombinator.com/item?id=48001113 https://news.ycombinator.com/item?id=46134570 https://news.ycombinator.com/item?id=46134570 https://news.ycombinator.com/item?id=46124596 https://news.ycombinator.com/item?id=46124596 I'm not a fan of any of the technologies, companies, or people related to this. I just couldn't shake the feeling that I've seen similar comments. September and all.

harrisi 3mo ago
I don't want to edit this to change the narrative, but I wanted to clarify that I'm not not a fan of all of the technologies or people related to this. As far as compan{y,ies} go, though, well..
vdfs 3mo ago
Maybe because the 1st thing any experienced technical person would think about? It's like rebuilding and optimizing the racing track to make F1 run faster.
- harrisi 3mo ago
  Perhaps. The thing I was trying to highlight more is comments (particularly disapproving ones) about the intersection of JavaScript (especially React, apparently), TUIs, and LLMs. I just thought it was interesting. I'm a fan of TUIs, both positive and negative about JavaScript (the modern language is quite nice, given you avoid the historical warts, in my opinion - the ecosystem is unfortunate), and I think the best description for how I feel about LLMs is that I'm bearish. Also Simon is a fantastically prolific and intelligent person though, even though LLMs are not my cup of tea. https://news.ycombinator.com/item?id=48960912 https://news.ycombinator.com/item?id=48960912 is a recent comment by someone I also respect related to how LLMs recreate human-like content (Widgets, really), making actual human-created content feel fake. Sometimes it sure does feel like ELIZA is the main news source these days.

molmos 3mo ago

[flagged]

Debo_Jolaosho 3mo ago

For real

LAC-Tech 3mo ago

Has all of this drama turned anyone else a bit sour on bun? I have a long running side project I migrated to bun, and I'm starting to regret it. I don't want to build on top of this much churn.

forrestthewoods 3mo ago

It’s interesting that Bun was a human rewrite from Go to Zig. (I think?). Then rewritten from Zig to Rust. AI is pretty good at rewrites and ports. Quite good infact.

effnorwood 3mo ago

My perl re-write is not very good.

deleted 3mo ago

[deleted]

globalnode 3mo ago

at this point im declaring any "rewritten in X" articles as trolling lol.

jgbuddy 3mo ago

Why even write Claude code in JavaScript at that point, assuming they write the application logic in node and also include the interpreter in the application?

snek_case 3mo ago
Probably because the team lead is a web developer, and whatever he says goes. Companies are typically very hierarchical, even if they like to claim otherwise.

512colors 3mo ago

you know what i hate? i hate that each update, to codex or claude code, it seems like they're always trying to "hide stuff" , reminds me of the 80s and 90s when tech assumes normal people are too stupid to see 'raw' stuff like terminal commands being run, its always been like that, less so now, but i get so mad when its doing stuff, and i can't see if its deleting files or just screwing something up. btw this is totally free tool buttonscli.com that is a full UI terminal app but its got a button for agent control. You click that, paste into claude code or w/e/any agent, and it'll use that for the terminal commands instead of the built in one so you can see everything (and it can open 10 tabs if it wants, you see them all)

NodesHub 3mo ago

[flagged]

the_black_hand 3mo ago

I'm stupid and clearly too stupid to google too. Is bun simply a better nodejs? Assuming it true that all of Claude code is now written by AI, why would AI care about using bun over node?

psyclobe 3mo ago

[flagged]

tomhow 3mo ago
Please don't. We detached this comment from https://news.ycombinator.com/item?id=48970444 https://news.ycombinator.com/item?id=48970444 and marked it off topic.

arikrahman 3mo ago

Why not just use Deno that's made in Rust and also has safety in mind?

quikoa 3mo ago
How will Anthropic be able to rewrite that in Rust and use it for marketing?
IshKebab 3mo ago
Yeah I'm also wondering what the point of Bun is when Deno already exists. Especially since it added Node compatibility. Genuine question, why should anyone use Bun if they're already using Deno?

m_bashirzadeh 3mo ago

[flagged]

skumar5190 3mo ago

[flagged]

Saba-Ba 3mo ago

It was an intersting case. Watched a youtube video about this and discussion from zig founder and bun was a little weird.

deleted 3mo ago

[deleted]

feiz45607 3mo ago

[flagged]

foldr 3mo ago

Is anyone else failing to understand all the internet drama surrounding this? The rewrite may work out on a technical level or it may not. Let's wait and see. The Bun project did not swear a blood oath to use Zig forever, and it's ultimately their choice to switch to a different programming language. Beyond that, people seem to be incredibly emotionally involved with this, for reasons that entirely escape me.

silverlemontea 3mo ago

[flagged]

overgard 3mo ago

Oh good, the vibe coded prompt injection vector that casually accesses things in my home directory without permission is running on a vibe coded prerelease runtime using lots unsafe rust. What could go wrong?

Unified-Mentor 3mo ago

[dead]