Bun’s Rust rewrite shipped in Claude Code over a month ago and barely anyone noticed. Claude Code is widely used. The Rust rewrite is going well overall.
In the Bun v1.4 video, I promised a certain number of newly passing Node.js tests were added to force us to improve compatibility, and that number is not true yet. The release is delayed until it is true. The PRs to make it true are up but not merged yet. Most likely next Tuesday we’ll do the release of 1.4.
Take as long as you need to ensure software quality. A month without a release isn't a big deal and whomever needs a specific feature can offer to contribute or build themselves.
Node has 4-6 weeks without a meaningful release (other than security stuff) pretty much every December. I think the criticism in the article is unfounded and whomever needed/wanted a release should have asked first instead of writing an "angry" blog post.
(I'm a Node.js maintainer)
What is Node getting every 4-6 weeks that makes it noteworthy when it doesn't?
Text imports (experimental), native addon ESM support, blob textStream(), ReadableStreamTee, byob for readFile, better event loop monitoring and lots of security fixes as well as more minor bug fixes and improvements. (Last 4-6 weeks)
Author here: I don't need or want another Bun release or an NPM release or anything like that. Like I very clearly say in the article I just got chatting with a peer about the Bun rewrite and I decided to take a look.
I'm consistently skeptical about new tech whether it is NoSQL or Blockchain or Serverless. Some of the things I'm skeptical about fail and some succeed.
The bun Port is a phenomenal engineering achievement that would have taken a team of people over a year or two to deliver previously - look at the TypeScript port for example (and they had llms).
The fact it's taking a while to release is still insanely fast. I'm sure they may be some bumps.
Being skeptical is good and some stuff succeeds and some doesn't - but building tools is still fun and cool, whether it's useful or widely adopted or not :)
The initial "10 days and $165k" was still a tad optimistic dontchathink?
That’s a great approach. No matter what you will always find a reason to be positively surprised!
What are some of your favorite tools or services that you adopted in the past few years?
uv
That's not surprising. Claude code is buggy enough, and releases break things often enough, that I wouldn't expect users to distinguish bugs introduced by switching to rust-based-bun from the normal garden variety bugs.
Claude Code is quite buggy but doesn't generally crash, which is what you would expect if it shipped an immature backend for a month. Maybe the rewrite is full of bugs and they happened to result in the UI glitches or trashed settings files or whatever other application-level bugs that Claude Code has routinely rather than crashes but that would be pretty surprising.
I can count the number of times an @ file reference doesn't autocomplete on a hundred hands. Or how a rewind won't reset the "is this file Read" marker. Or how a Branch (forking a convo) takes literally 5+secs to run. Or how a slashcommand that's user-only will not work if its in the middle of a prompt. Or how ctrl-r search will match results that don't include any search terms. Or how you can't resume a branch given its session id.
Yes Boris, tell me more about how "coding is solved".
Edit: literally just now, while writing a claude code hook, opus5 gave me this LOC because apparently the changelog and what's in the transcripts _differs_; great docs d00ds.
I’ve come to just expect that my CC instance will randomly “blank” and that I have to resize my terminal / use page up/page down to get it to show again.
Supposedly they used a game engine to render their TUI but I’ve never had an FPS game do that.
They drive the TUI from the same thread that actual does stuff.. causing frequent freezes.
No GUI developer would ever put this on the same thread.
[dead]
I noticed, I started getting memory leaks suddenly and it restarted the process in long sessions because of limitation of environment limit.
Any comment on the costs estimated in the article? especially the buildkite costs?
CI has always been expensive for Bun including before the acquisition. We build for [macOS, Linux, FreeBSD, Android, Windows] x [ARM64, x64] and then run tests on multiple Linux distros with multiple shards, multiple macOS versions and Windows for each architecture.
We recently started cross-compiling all the builds on Linux arm64 and that made it a little faster (I wrote a CLI tool to download the correct macOS headers for cross-compilation). We also have a daily cron job that asks claude to make the slowest tests faster while adding more assertions.
So are the "$800k + CI" estimates accurate? And your team works weekends just to make tests faster?
I think the question for CI costs is still out there. While I do not think it should be in tunes of thousands a day but thats the skepticism presented in the article. True costs are really important to make a good decision in situations like this. One has to consider the fact that lots of people are going to use these numbers to justify the rewrite in future.
How come Bun uses Buildkite instead of self-hosting the CI infra?
It spawns ephemeral EC2/Azure instances, which is a lot cheaper than the GitHub actions runners we used before that.
We shard to a lot of machines for tests and I’d be worried about running out if we used dedicated servers.
BuildKite is fine but I wouldn’t be that surprised if we move off of BuildKite to a custom thing at some point. Months ago, we switched from CMake to a handrolled typescript build system and it made our builds faster and simpler.
Thanks for answering!
I suppose my second question would be how much Bun spends on CI per month atm - I'd imagine that robobun would have ramped up the bill a fair bit
you don't need buildkite or blacksmith anymore.
codex trivially built me a self-hosted gh actions runner workflow for ephemeral vm's (just a big bash script that manages the vms with qemu). i even sped up the builds with my own custom base image with everything installed in it that i need too.
it works flawlessly.
fanning that out to starting and stopping instances wouldn't be too much of a stretch.
Does it work with macOS ?
weird question, i don't see why not. osx has a fantastic virtualization story.
https://developer.apple.com/documentation/virtualization/run...
Presumably because they "build for [macOS, Linux, FreeBSD, Android, Windows] x [ARM64, x64]" and self hosting all of that would be time-consuming and expensive.
Probably because they don't want to self-host Windows or MacOS servers when they can pay someone else to do that for them (or Linux ones, I assume that is within their wheelhouse for production but CI is a bit of a different beast to model inference).
Jarred, thank you for working on Bun. Many "vibe coded" :D projects start strong and are later abandoned (like potentially Anthropic C), so I understand why people worry about Bun's future. I hope Bun lasts for many years, like GCC. Bun is fast and great to use.
Anthropic's C compiler was a proof of concept[1], so it makes sense that it was abandoned.
[1] What it actually proved is up for debate.
> What it actually proved is up for debate.
I guess I'm debating, but it seemed clear enough to me? It proved that AI models and their harnesses are to the point where you can give them some work to do and leave them unattended for a long time, and they'll keep doing productive work for quite a while. This was a novel thing, and quite unclear, at the time the experiment was performed.
Obviously, the word "productive" is doing a lot of work there, but in my understanding the intention was nowhere near "commercially viable" or "practically useful", it was more like "not doing stupid shit like writing comments of the form 'This file contains the implementation implementation implementation implementation implementation implementation implementation implementation implementation implementation implementation implementation implementation ...'".
Maybe somewhere in the vicinity of "either passing more tests or generating more valid tests"?
In Dutch there's a saying, "wij van wc eend adviseren wc eend", and it fits perfectly.
I don't see how it does. Claude Code is an extremely widely used product; the preceding comment offered an objective evaluation target, not a "trust me it's good" argument.
I don't see how Claude code being a widely used product is relevant to the person who orchestrated the Rust rewrite of bun saying that the orchestration of the Rust rewrite of bun went well. Wc eend is a widely used product as well, if that helps.
Ah, for context, which I suspect you may be unaware of, Jarred (the person who said the rewrite to rust went well) is the creator of bun, and the guy behind the rewrite.
I think the chain of reasoning is not hard to follow:
1. Assume the Rust rewrite of Bun went badly
2. Then something must be grievously wrong with a released bun runtime based on that code
3. Claude Code uses the released bun runtime based on that code
4. From #2 and #3, something must be grievously wrong with Claude Code
5. If something were grievously wrong with Claude Code, users would reduce use of Claude Code and use alternative tools
6. From #4 and #5, users are reducing use of Claude Code and using alternative tools
7. Claude Code has wide use and use is growing across all software engineering verticals
8. #6 and #7 contradict
9. From the contradiction, the assumption in #1 is false
The parts that are not explicitly spelled out here are an exercise for the reader. It doesn't really matter if the guy who wrote Bun said this or my uncle said this.
Frenchman here, I Google Translated that and it says
"We at WC Duck recommend WC Duck"... I'm left scratching my head, if you'd care to spell out what the saying means for non-Dutch I'd appreciate it :)
It was a commercial slogan for a toilet cleaning agent. An English equivalent would be "mr clean recommends you use mr clean". Today, it is used to point out when someone tells you they themselves delivered good work. Anytime you'd use the meme of Obama giving himself a medal, you could use this phrase.
The Toilet Duck brand exists in English. Canard-WC in French, even.
If actually anyone noticed, then it is a pretty bad move. Also “going well overall “ does not answer the author’s observations either.
Any chance for 1.3.15 with bugfixes for the rest of us?
Yeah, 1.3.14 has some bad regressions. 1.3.11 is ideal for tests CI. Or canary. For production, I don’t have any advice. There will be no 1.3.15.
> The Rust rewrite is going well overall.
I look forward to the postmortem!
https://bun.com/blog/bun-in-rust
This is from July 8, 2026. And while you did link it in your article, what else are you expecting?
The initial post said something like 11 days and $165k in tokens and it's done. The charts in the OP suggest that Something Interesting happened between July 8th and today, burning way more tokens and human labour. Wouldn't you want to know what?
Either you mean retrospective, or you're being unnecessarily mean for something that's been getting quite a lot update reports, just on a social medium you probably don't use =P
I thought it was a fairly common turn of phrase! https://blog.codinghorror.com/the-project-postmortem/
A postmortem is for reflecting on something that went so wrong you had to kill it, and you want to objectively describe what led to that, and what lessons can be learnt from the failure.
A retrospective is just the reflecting part, without implying you believe it is going to fail and you're looking for some schadenfreude ;)
This might be terminology that's used differently in different places. For instance, in video games it is extremely common to use "postmortem" to mean "post-shipping."
Example: https://blog.codinghorror.com/game-development-postmortems/ Note the dual emphasis on both "what went right" and "what went wrong," not just one or the other.
But postmortem is literally “post death” in Latin. It’s synonymous with autopsy! I know people misuse borrowed words all the time, but come on?!
> is literally “post death” in Latin
Yes; I think what I described matches that meaning?
Post-death, as in: "it's over," "activity has halted," "no more work being done."
Death does not necessarily have a bad/negative connotation. It's just the end of something.
This is in contrast to the original comment: "something that went so wrong you had to kill it." Death does not imply something went wrong or that it happened forcefully.
I guess "autopsy" generally is talking about "finding the cause of death" so maybe that has a more negative connotation ("something (bad) happened, causing death, let's find it").
Ah, words with their fuzzy meanings (:
> Post-death, as in: "it's over," "activity has halted," "no more work being done”
Which makes even less sense as we all know software is never done, unless it truly is dead.
In the context of a game it applies. A game can be "done", as in shipped, no more updates, patches, etc.
The postmortem for many cows is “how did you like your hamburger” so it isn’t all bad (from the user point of view at least).
> But postmortem is literally “post death” in Latin.
Sure, that's true. It's not really relevant to people who don't speak Latin.
> It’s synonymous with autopsy!
This isn't true. I have no idea how you got here. In English an autopsy is a surgical procedure performed on a corpse for the purpose of identifying the cause of death. In particular, it's a noun. "Post-mortem" in the etymologically literal "after death" sense is an adverb or adjective identifying whatever it is as taking place chronologically after some contextually-specified death.
But, you seem to put some weight on the etymology of a word independently of its current meaning. In that case autopsy "literally means" to witness something personally, as opposed to hearing about it from someone else. (It's "self-eye" in Greek just as post mortem is "after death" in Latin.) Somehow I doubt that's what you had in mind...?
An autopsy is an exam that is performed postmortem. And that’s really how people are using postmortem as a noun for the analysis that they perform after the “death” of a company, so it is a synonym at least approximately, if you don’t see that I guess you don’t have a very good imagination.
Try and find me some sentences out there on the internet in which one of the words could be reasonably substituted for the other one.
They don't mean similar things and they aren't used similarly. A postmortem is, as you note in part, a report or a meeting for the purpose of producing or discussing such a report; an autopsy is a surgical procedure. They're as "synonymous" as the words "cigarette" and "cancer".
A post mortem is a very common term in many industries on how something went after you shipped it.
You’re taking it very literally here, it does not involve anything being dead or killed.
We’ve used this in the software, games, film and construction industries for decades at this point.
Substitute Mortem for Ship and that’s how people use it.
From the article:
> The goal of a postmortem is to draw meaningful conclusions to help you learn from your past successes and failures. Despite its grim-sounding name, a postmortem can be an extremely productive method of improving your development practices.
I've been reading people use "postmortem" to describe software retrospectives for like... 15+ years.
Mostly in the opensource, or marketing-blog spaces. The detailed investigation and fix report was a favorite genre of blogpost. And if someone's bragging about the design of an enhancement, or investigating a bug, then the overall product isn't dead. They're (usually) not talking shit to anyone. It's the bug that's dead. Or security indecent that's over. Or a schedule milestone that's "dead and burred".
It's a 1 chili pepper level of spicy to use a slang term that relates to death. I'd never read it as hoping someone fails. I think people let the corpotalk center of the brain overreact to anything that's not couched in euphemism.
In the specific case of ship retrospectives, I prefer to call them “postpartums”.
I guess they’re saying their shipped code is DOA?
We would need to know at least:
- How many people have updated Claude/Bun to the latest version.
- How many subscribers care about reporting issues. Most of them are forced to use the tool against their will and have mentally checked out already. Why report issues if your employer values slop code anyway. Just log the hours and keep your head down. Maybe it is not expedient for the AI narrative to report issues!
- How many subscriptions are real vs. bulk distiller accounts.
- If subscriber numbers are inflated.
Judging by the weird Claude Code Github issues page, there are suspiciously few new issues: about 2 to 3 a day only vs. alleged subscriber numbers of 4 million.
> How many people have updated Claude/Bun to the latest version
By default, Claude Code updates itself all the time without asking for permission, so I'd say most users are on the latest versions.
I do not trust AI agents to run outside sandbox and use them only in dev container. I always use latest version available when I build container (once or twice a month). In my opinion it is to risky to allow auto update for SW which is released several times a week including weekends and is capable of/willing to do script kiddie pranks :-)
I’m really glad I don’t use anything that relies on Bun. What a mess you’ve made of this whole thing.
Jarred thank you for doing the impossible over and over. Bun is such a fun thing to use after years of npm. Good luck with your quests! Have fun