frontpage.
newsnewestaskshowjobs

Open Source @Github

fp.

Open in hackernews

How is the Bun Rewrite in Rust going?

https://lockwood.dev/ai/2026/07/27/how-is-the-bun-rewrite-in-rust-going.html
128•tomlockwood•1h ago

Comments

brap•1h ago
If you’ve ever worked at a tech company you already know the answer without reading any further
raincole•1h ago
Yeah, the answer is that it's gonna working fine for most users.
tomlockwood•1h ago
Author here: An apology on the graphs, they just count rust files touched in commits, not total commits. So if there were two commits and one touched 3 .rs files and another touched 2, it'd be counted as 5 for the purposes of the graphs. I may fix this later but, yeah.
alienbaby•1h ago
what kind of difference from the actual numbers does it result in?
tomlockwood•59m ago
Not sure! I cludged together a counter using git log. I could go back and redo it but I think the number would serve my point either way.
hahahaa•36m ago
Hope you find that job :) nice work experience, looks very ethical focused.
abalashov•1h ago
I did suspect that the triumphalist pronouncements, and even the seemingly honest and forthright deep dive, were a little premature.

This is a key problem with LLM exuberance: it's very tempting to trade on decades of experience in software using LLMs, because one is tired of typing and manual figuring-out, it seems to work if you're competent, and the payoff is essentially immediate. The real bill comes in the mail much later.

reliabilityguy•1h ago
Many repeat the point of “$165k is cheaper than team of multiple engineers working on the rewrite for a year”, which I think is flawed — the team of engineers would have produced idiomatic rust, and it would take probably 100k+ of tokens more to make the bun in rust idiomatic rust.
Tinkeringz•51m ago
I feel your estimate of tokens is a few orders of magnitude off, it’s on the low side.

I use more (albeit cached) when centering a div.

Hasnep•46m ago
I think they missed a $ sign, i.e. they meant $100k of tokens
reactordev•45m ago
100k tokens is your pre-prompt and your CLAUDE.md as well as a few files from your root.
rezonant•37m ago
This is where we've come to where people proudly proclaim using an AI to do what is a single line of CSS.
moralestapia•24m ago
What a great joke.

I will have to steal it for an upcoming AI tools meeting I have at work.

Also, pretty clever as centering a div w/ CSS has been notoriously difficult to achieve.

muglug•1h ago
This post doesn’t make sense. It was rewritten in Rust. The rewrite itself is complete (no more Zig).

Various people have claimed that Bun in Zig had a lot of tech debt. If they’re to be believed, it seems natural to assume the rewrite does, too. Perhaps all this activity is paying down some of that debt.

abalashov•1h ago
> Perhaps all this activity is paying down some of that debt.

Perhaps. But were that the case, one would think they'd be quite eager to say so.

muglug•54m ago
Maybe they will!

Are you expecting them to live-tweet their work or something?

tough•44m ago
jared was OK making this rewrite as an experiment branch in the public

why shouldnt upcoming work be as public as the rewrite itself was?

rk06•57m ago
bun in zig was used by many companies. some were using it in prod. how many of those are using it in prod? none, because bun in rust is not released yet.

Hence, the author concludes that rust rewrite is not complete as bun in rust is not released yet.

I agree with author's POV.

davidgtonge•48m ago
vortegne•1h ago
I didn't follow the thing too closely when it happened. Sure, I was aware of the big picture. But wow, I didn't expect that after all this noise there still hasn't been a release? That's just crazy to me.

I shouldn't be surprised though, of course. Giving any credit or slack to a high-valuation LLM company is a silly endeavor.

jeltz•40m ago
It was expected. These LLM rewrites seem to work amazingly at first and then you realize there is a ton of work remaining.
yearesadpeople•58m ago
> _"...Canny..."_

What a time to be alive

rob74•50m ago
Yeah, I noticed that too and kept wondering who this Canny was that the author wants to be? Felt a bit un-Canny...
tomlockwood•30m ago
More proof that it was written by a human!!!
SquareWheel•50m ago
I'm not sure how much insight we can glean from looking at the number of commits and release cadence here. In the aftermath of such a major refactor/rewrite, I would expect it to take some time to get back up to their usual development speed.

Jared and the other developers are new to the Rust codebase, even if the structure is largely familiar. They're also likely focusing on other priorities right now such as tracking down instances of 'unsafe', rather than making user-facing changes (which might encourage a release).

Bugfixes could encourage rapid new releases, but perhaps the rewrite simply hasn't been very buggy? As far as I know, those on the canary channel haven't reported any major issues, or even really noticed the change. So perhaps there's little reason for new releases right now, as the team slowly churns through the backlog.

> P.S. Anthropic’s C compiler and Cursor’s FastRender web browser haven’t had any commits for months.

I always assumed those were just experiments in capability, and weren't meant to be ongoing projects. I would hope that nobody is using them directly today.

usef-•46m ago
They also have made a release, in a sense, since they moved all Claude code users to it. (And apparently no one noticed).

I think they're taking things "gradually" as they are under a lot of scrutiny and no rush for full release.

flohofwoe•15m ago
Claude Code most likely only uses a tiny fraction of Bun/Node features, so Claude Code switching to the Rust rewrite doesn't mean all that much.
tomlockwood•45m ago
Author here: I'm also not sure how much we can glean from any of that!!! I look forward to Anthropic or Bun releasing a retrospective after their next release that fully outlines the cost.
eelke•48m ago
While the Rust rewrite branch might not be officially released, Anthropic and (I assume) the Bun team considered it good enough to ship to millions of Claude Code users (since v2.1.181) for over a month now!
losvedir•43m ago
I'm not sure Anthropic even cares about "releasing" the next version. The rust one has been in use in Claude Code for more than a month now, used by millions of people, and that's as far as they probably really worry about it. They bought Bun for Claude Code and I doubt the open source project matters to them otherwise.
usef-•41m ago
I very much doubt they would want to abandon the wider community. They do benefit from others using it.

To the contrary, I think any problem with this release would be jumped on harshly so they're being more careful than usual. There's not a rush for the community to move to 1.4 and any issues could poison the community trust.

rienbdj•35m ago
Anyone know why? Can’t CC run on any JS runtime?
jFriedensreich•12m ago
because their js code is so bad and slow that they need the bun performance hacks and optimisations.
amazingamazing•43m ago
Why did they buy an open source project anyway? If is not “officially” supported why not fork and use? Claude code is probably the most used anyway
jeltz•38m ago
They bought the maintainers, not the code.
amazingamazing•16m ago
Why though? Isn't AI supposed to take care of such things?
quikoa•35m ago
To me it just looks like a marketing stunt.
benjiro29•36m ago
I really do not understand how software developer think anymore. Using a LLM to translate a project in a short time, is by itself incredible. Just like one-shot whatever office clone.

But what makes software is not the fast creation of a "product" but that actual development of its features. Figuring out how everything needs to work together, fixing the bugs, and the o so boring UI work.

I have used LLMs to create stuff like word clones just for fun. It was a disaster. Sure, it had the basic functionality. But the moment you started with page structure (harder then one non-stop scrolling page), tables, images, rotating, and so many details that make up just the basics of word. Not even the extended functionality. You see every LLM just fall on its face.

Sure, i can clone sqlite from c to rust. Hell, i may even get it to do all the tests 100%. But there is a 99% chance that the clone will be slower, as it lacks the years of optimizations from the original language. There will be new bugs because of the language changeover. There is a need for future support and fixes.

People threat software like its something it is not. But unlike the past where your clients question your sanity for charging 100k for a piece of software. Not understanding its not just about writing the code. Now those expectation are even more pushed forwards, because of articles like this.

I constantly see software being published on reddit that does X, Y, Z only for the authors to abandon it as fast as they vibe coded it. Because fixing bugs is NOT sexy. Even with a LLM at your fingertips. Dealing with nagging users, is not sexy. Dealing with security issues, is NOT sexy. Dealing with data structure / databases, especially as your system changes ... you get the point.

Not understanding to the core the software you wrote, is going to exploded in your face.

This is why these stupid "we rewrote X into Z with a LLM in Y days" mean nothing. Its one thing to get a head start using this trick, its another to actually learn the code of your rewrite. And dedicated the time into maintaining the port, growing it, fixing it. This is where a lot of software fails. But now this crap is out there, instead of the maintained version of Zig, now we have a unmaintained Rust version that clouded the airwaves because if people now search for it, those articles "X in Z days" will pop up.

What have we become ...

furyofantares•28m ago
> I have used LLMs to create stuff like word clones just for fun. It was a disaster. Sure, it had the basic functionality. But the moment you started with page structure (harder then one non-stop scrolling page), tables, images, rotating, and so many details that make up just the basics of word. Not even the extended functionality. You see every LLM just fall on its face.

What do you think of https://scramblequest.app and https://wordpeek.app ?

I have never looked at any of the code for them

edit: Yeesh, misread your comment as "word games" not "word clones" and was very confused about the claim. Probably should have noted my confusion and re-read.

xiphias2•24m ago
Everybody who has rewritten software understands the current phase: it mostly works, but there are always things to fix to make sure that there are no regressions, and the pressure is huge for any release.

I still believe it was the good decision, but I also know that I wouldn't be the first person to run the release in prod.

I think Jarred should start making release candidates instead of releases to take some of the pressure off.

IshKebab•21m ago
This doesn't answer the question posed in the title unfortunately. I am none the wiser about how it's going. The author just speculates that the rewrite isn't actually complete.
tomlockwood•14m ago
> I am none the wiser about how it's going.

You and me both friend!

internet2000•21m ago
I don't get it. Because they haven't cut a new arbitrary version number, we're denying it got done (in their perspective) and being used in a massive product already?

If you're being pedantic, no it's not "done," but nothing ever is.

skydhash•16m ago
> and being used in a massive product already?

One single product, AFAIK, and one ladden with bugs and issue too.

pu_pe•13m ago
I am fascinated by the discourse around this Bun rewrite. I read a lot of drama and personal accusations, there are pieces like this one trying to extract clues, and it seems everyone has a deeper ideological concern behind whatever they are trying to say. For this article, it seems to be skepticism towards AI and how successfully it can be at replacing programmers. Other takes, like the one from the Zig maintainer, were also along those lines but more about the open source ethics and the future of that in a LLM world.

I am mostly bullish on AI capabilities, so from my perspective I don't see why we should be skeptical that frontier LLMs guided by experienced devs can translate whole libraries like that. Good follow-up questions would be how expensive it currently is to do so, and whether we will see people branching into all-in on AI versus no-AI camps as happened in this case.

CrzyLngPwd•5m ago
Just a couple more 100hr weeks of debugging, and the last 80% will be done :-)
irishcoffee•37m ago
> produced idiomatic rust

I keep seeing this. What is "un-idiomatic" rust?

vessenes•33m ago
Presumably lots of stuff wrapped in 'unsafe'. I'm not a rust guy or a rust fan, and the last time I wrote something with Rust was like 7 years ago, but to my memory, because of how Rust manages mutability there are many access patterns that are Rust-specific; idiomatic Rust is going to use this patterns but they would be unlikely to show up in a language with a different type system / borrow checker / etc. etc.
irishcoffee•28m ago
So "unidiomatic" rust means, 'don't use these parts of the language even though they're first-class citizens?'

How odd. Lot of mental gymnastics going on there.

tribaal•13m ago
It's mostly the same in any general purpose programming language though, parts of the language features are meant (or became seens as) tools to be used in very narrow cases, which people less familiar with the language tend to "overuse".

Eg. goto/jump, bare "except" statements in python, etc... In Rust, unsafe has its uses and is a first class language feature, but it certainly isn't idiomatic to use it to mimic access patterns from other languages (unless absolutely necessary).

flohofwoe•6m ago
The Bun author himself writes that the Rust port is not idiomatic Rust:

    Do the rewrite that looks like we transpiled our Zig code to Rust. We can gradually refactor it to reduce unsafe usage and look more like idiomatic Rust after Bun v1.4 ships.
(from: https://bun.com/blog/bun-in-rust)
TazeTSchnitzel•12m ago
Rust contains the ability to do everything that C can, if you use `unsafe`. And a file-by-file rewrite in Rust from another language usually involves keeping the ABI and API between files very C-like (and unsafe). In practice this means that the result of a first pass this way has all the memory safety of C code, but with worse readability because Rust makes unsafe things less ergonomic.

To actually get the safety benefits of Rust in a real way you have to rework those files to not treat eachother as C code. This is the interesting and the difficult part of a rewrite in Rust, and one that an unsupervised LLM rewrite is probably not even going to attempt.

I don't think this latter stage has actually happened with Bun's codebase. The result of the Rust rewrite in Bun's case is actually less safe than the Zig it is replacing, especially because (I am told) a lot of the new Rust code is unsound (introducing UB).

furyofantares•26m ago
They also would have produced a team of engineers that knows the Rust codebase.
tcfhgj•6m ago
I doubt file by file rewriting takes as much work as rewriting and refactoring the code - especially at this scale.
The rust version is being used by Claude Code though - which is a fairly large product!

I was hoping for more push back against https://bun.com/blog/bun-in-rust - which is pretty thorough and has some decent arguments and reasoning for why they did the rewrite.

reactordev•46m ago
I think they meant “released and available for use” rather than just out in the wild.
thevinter•6m ago
It is available for use: `bun upgrade --canary`
nullsanity•45m ago
Yeah, but it's a TUI that has more bugs and worse performance than any other TUI in history. It's not like we'd notice a user after free.
flohofwoe•9m ago
How much of the Bun/Node API surface does Claude Code actually use though? Conceptually it's a relatively simple TUI application.
virajk_31•56m ago
Author kept "going" in title because there has been no minor/major release in last two months which unusual for this project if you review the older releases.
muglug•33m ago
A major rewrite in another language is also unusual for this project.

It took TypeScript a year to go from announcing tsgo to releasing TypeScript 7.0. That work was done in parallel; here the work is being done serially — and it’s likely to take much less than a year for a new release.

virajk_31•25m ago
Yes, its because Anthropic took over and wanted to showcase their LLM capabilities by porting such a complex codebas.
taormina•5m ago
Everyone’s point is “they have everything to gain by lying about being more done then they are” and “the claims seem at least a bit full of shit”.
cowl•52m ago
tech dept is not a problem. to paraphrase captain Jack sparrow. "even if it were the most indepted working software project, IT WORKED". On the other side of the medal we have a rewritten software that although it's trumpeted for it's rewrite speed, it is not showing the same Release speed as the manualy written, "tech dept ridden" old one.
pizza234•4m ago
> This post doesn’t make sense

The author's assumption is that a rewrite is not just a mechanical translation of code - it's also a state of stability. And no release, for the author (I agree) means no stability.

It's like a developer who says that after a week of work, a feature is 90% ready, but the other 10% is still not ready (for release) after months.

jeltz•35m ago
Given their history with previous other marketing stunts I do not expect any retrospective. The technology is real but I have little faith in open and honest communication from Anthropic.
rurban•22m ago
Nonsense. Provide/create proper tests for all features, and let the LLM test and fix everything.

In case of ccc (claudes C compiler) they just did not use any tests, though they are many existing C testsuite. They just stopped, when it finished compiling the kernel, still failing hundreds of tests.

oblio•15m ago
Are you comparing 2 relatively simple games with... Word?

Word is basically an operating system. Unix people like to make fun of Emacs for being one, but Word is basically one, too. And all the features in there otherwise Microsoft wouldn't keep them.

furyofantares•12m ago
Haha, I misread as "word games" and was very confused about the claim.
TaLiTr•15m ago
I think they might mean Word as in Microsoft Word. Just based on the feature list they were describing.

How is the Bun Rewrite in Rust going?

https://lockwood.dev/ai/2026/07/27/how-is-the-bun-rewrite-in-rust-going.html
133•tomlockwood•1h ago•74 comments

Kimi-K3 Releases on HuggingFace 7/27

https://huggingface.co/moonshotai/Kimi-K3
533•nateb2022•6h ago•245 comments

Elevated errors on Claude Opus 5

https://status.claude.com/incidents/mfdtrknpxghq
20•croemer•1h ago•17 comments

PGSimCity - How PostgreSQL Works

https://nikolays.github.io/PGSimCity/
719•jonbaer•12h ago•68 comments

AI companies are shredding rare books

https://xcancel.com/HedgieMarkets/status/2081534588485296565
65•anon373839•27m ago•18 comments

Libsm64: Mario 64 as a library for use in external game engines

https://github.com/libsm64/libsm64
39•klaussilveira•2h ago•8 comments

Magnolias Are So Old That They're Pollinated by Beetles, Not Bees

https://mymodernmet.com/magnolia-ancient-flowers-beetles/
114•speckx•4d ago•47 comments

Removing React.js from the codebase and adapting Htmx for UI interactivity

https://misago-project.org/t/removing-reactjs-from-the-codebase-and-adapting-htmx-for-ui-interact...
29•Ralfp•3h ago•12 comments

Building a Fast Lock-Free Queue in Modern C++ from Scratch

https://blog.jaysmito.dev/blog/04-fast-lockfree-queues/
23•ibobev•4d ago•3 comments

The Birth of the American 12-string Guitar

https://www.harpguitars.net/history/grunewald/12-string.htm
28•bilegeek•2h ago•12 comments

Show HN: Physically accurate black hole you can put in your room

https://blackhole.plav.in
375•aplavin•3d ago•124 comments

Towards a Theory of Bugs: The Ruliology of the Unexpected

https://writings.stephenwolfram.com/2026/07/towards-a-theory-of-bugs-the-ruliology-of-the-unexpec...
10•nsoonhui•3d ago•0 comments

The Proof Machine (2016)

https://incredible.pm/
4•BenoitP•30m ago•0 comments

Shay Locomotives

https://www.shaylocomotives.com/
22•Rygian•3h ago•4 comments

VLC for Unity now supported on Linux

https://code.videolan.org/videolan/vlc-unity
50•martz•3h ago•14 comments

Elevated errors on Claude Opus 5

https://status.claude.com/incidents/lhqp09kxq7pb
31•flyaway123•4h ago•15 comments

Scriptc by Vercel: TypeScript-to-Native compiler, no JavaScript engine in binary

https://github.com/vercel-labs/scriptc
219•maxloh•14h ago•109 comments

Modern email can be built from borrowed parts

https://en.andros.dev/blog/d7ed8b07/modern-email-can-be-built-from-borrowed-parts/
38•andros•4h ago•9 comments

Decker, a platform that builds on the legacy of Hypercard and classic macOS

https://beyondloom.com/decker/
334•tosh•18h ago•76 comments

US citizen charged after GrapheneOS phone wipes during airport search

https://www.techspot.com/news/113236-us-prosecutors-charge-atlanta-man-after-grapheneos-phone.html
927•eecc•14h ago•719 comments

Worse on Purpose

https://ledger.worseonpurpose.com/brands
12•bookofjoe•30m ago•0 comments

We have proof automation now

https://www.imperialviolet.org/2026/07/26/zstd-lean.html
192•zdw•16h ago•74 comments

Chinese chipmaker shares surge 470%

https://www.bbc.com/news/articles/c9q9w3x9qn2o
111•pingou•3h ago•98 comments

I wanted a clock that never needed setting. Things escalated

https://arstechnica.com/gadgets/2026/07/i-wanted-a-clock-that-never-needed-setting-things-escalated/
139•lee_ars•4d ago•115 comments

Google Chrome Arrives on ARM64 Linux, Widevine DRM Included

https://www.omgubuntu.co.uk/2026/07/chrome-arm64-linux-available
14•twapi•1h ago•4 comments

Introduction to Data-Oriented Design [pdf]

https://www.gamedevs.org/uploads/introduction-to-data-oriented-design.pdf
196•tosh•18h ago•53 comments

Measuring developer productivity with the DX Core 4

https://getdx.com/research/measuring-developer-productivity-with-the-dx-core-4/
30•saikatsg•3d ago•25 comments

How Unix spell ran in 64 kB of RAM

https://blog.codingconfessions.com/p/how-unix-spell-ran-in-64kb-ram
57•donw•4h ago•4 comments

Fonts In Use – Find out where a font is used

https://fontsinuse.com/
87•open_•13h ago•10 comments

Simulate cassette tape audio profiles using FFmpeg

https://github.com/AARomanov1985/Audio-Cassette-Simulation
148•xterminal•16h ago•65 comments