Completely regardless of how the code was written or even if anyone understands it thoroughly, they replaced the entire running codebase in a week. The entire project was one thing and is now something different.
There are countless reasons that this is a very bad thing for consumers of Bun. First and foremost you've instantly lost any and all assurance that it works the way it's supposed to. Every project has load-bearing bugs that may or may not still exist. Can you trust the core behavior is the same?
If the Bun maintainers are willing to completely replace their core product over the span of a week, how is anyone supposed to rely on it? What's preventing another rewrite in a few more weeks?
If you want to position your product as a dependency, it needs to be stable and reliable. Throwing away a million lines of code and replacing the entire product overnight is pretty much the polar opposite of stable and reliable.
It has nothing to do with AI rewriting the code, it's the reckless abandon and wild disregard for consumers that is the problem. It's literally a rug pull.
I don’t think changing from zig to rust suddenly means that don’t know what a certain file contains or how it works or how it relates to other files.
It’s all the same just different syntax. Which, by the way, is why it looks ugly to rust developers. The devs wanted the code to look familiar to them.
I do think they should have called this 2.0 though. Would not feel such a rush (1.3.14 has a few regressions, and no one really cares because there are lots of small rust fires now).
Overall, the bigger issue is that bun chases shiny objects. But never finishes. Just look at test stuff. Most of vistest, but not all. Most of jest, but not all. Most of pnpm, but not all. Now we have image stuff, so most of sharp, but not all. dev server? Most of vite, but you guessed it… not all. Long running process… mostly like node but with memory leaks (and a motivation for rust I’m sure).
When I saw them posting about the Image routines my heart sank. Another shiny object. Coincided with test bugs so I moved to vitest completely.
> I don’t think changing from zig to rust suddenly means that don’t know what a certain file contains or how it works or how it relates to other files.
What if there was some malicious code within the 1 million lines?
Pretty normal in many corporate cultures especially ones with high turnover. You get assigned to a team that's "maintaining" a 10 year old code base with few million LoC. The most senior person on the team has been there for a year or 2 and it's just business as usual. You don't know what those 1M+ lines are doing. No one does. It's not a passion of anyone to work on it. You just get a bunch of requirements handed to you, you blackbox everything but the surface areas you need to touch. It's why there are 14 implementations of a background service 8 dependencies that do the same thing, 6 overlapping frameworks, a complete mismatch in style, approaches, etc. It doesn't really matter.
It does matter, that's why those people quit because it's such a shitshow, progress happens at a glacial pace, more and more defects and slowdowns keep being created even if they have a big QA department/teams and the users are probably trapped because the software is the only thing in town, the bosses are the ones that makes the purchase decisions, or the it comes attached to big and/or expensive machines and they can't just buy another one for another X years.
Right. I now have responsibility for rather large codebases where the person who generated it with agentic tools (I'd say it's better than pure 'vibe coding') barely understands how it works. This is okay for unimportant parts of the codebase, but completely unacceptable for a critical piece of infrastructure where it really needs to be well thought out.
So it was possible to write ~2 million lines of (mostly) zig, but it's not possible to review ~1 million lines of rust, even though the same test suite included in those 2 million lines of zig can still be used? I'm not convinced the rewrite is a good idea and will work out, but I'm equally unconvinced by your argument.
A project that's 2/5/10/30/100m LoC is obviously not going to be understandable entirely in someone's head. Documentation is critical. But if I'm reading your code, and I come across something confusing or you wrote something in a weird way and I want to understand, then I just... Come and ask you. "Hey, why did you do this this way? Did you consider x?" With an AI you can't do that. IMO this point is especially important if your code base is widely deployed to the point that people use it as a learning resource or a good source to learn good practices.
> in many aspects of human history, we have traded understanding for convenience—that's the reason why we buy food at the supermarket instead of hunting for our meal.
You could always take a job on a cattle ranch or an abattoir or meat-packing plant, or watch a How It's Made documentary, and get some understanding of how the sausage gets made and put on the supermarket shelf for your convenience. This was also true as we built abstractions in computer technology: you could start off learning a high level language, then learn a lower level one, then study or build an operating system kernel, a compiler, an assembler, machine code, and then crack some books on microprocessor architecture and signal processing. You could always "go deeper" if you wanted to. And there is a payoff: understanding at a deeper level helps you get things done better at the higher levels (e.g.: understanding the concept of memory hierarchy helps you lay out data structures to make code faster).
There is no such step for slop-coded codebases: you become entirely dependent on a context-limited LLM to have a shot at even approximating some understanding. The proponents of this style will tell you, don't look at the code. It's the antithesis of every other abstraction we've built in computing.
Perhaps more productively, you treat the slop as a black box and build something understandable around it.
This is also why the notion that developers in the future will be committing LLM prompts in English to repositories instead of code written in a programming language is so foolish. I am saying this as someone who uses LLMs quite a lot to help with generating and understanding code.
>How could the maintainers understand their codebase if most of it was not directly written by them?
Counterpoint: I look back at code I wrote a few years ago and just take it on faith that I knew what I was doing at some point. That's still better than never knowing, but it requires faith--faith in a human, vs. faith in an LLM.
Yep. These days, simplicity is a massive part of my development style. I don't want to be looking at a codebase, even my own, and thinking "shit, this guy was way smarter than me".
It's a bit harder to avoid windows than it is to avoid Bun.
More importantly, it's not the same thing at all. All the code in windows (at least until recently) was written by humans, understood by humans and reviewed by humans. And that code has stood the test of time, proven its value and stability in the wild, on billions of systems. The fact that the current maintainers haven't needed to understand or replace the code is some indication of the code's quality.
Almost none of Bun's rust code has been even seen by a human, and it's only about two weeks old.
I'm somewhat willing to accept vibe-coded code if it's either absolutely non-critical, well reviewed, or maybe in the long term if it's proven itself. But not two week old code.
> They support Windows, which is many millions of lines of code not written by the current maintainers.
All of which was battle-tested on millions, if not billions, of devices over 40 years. The new Bun is effectively a different project than it was a month ago, with next to no prod use.
I have no problem having a dependency on a 40 year/billions of use software, I do have misgivings about a dependency on a project that has never been used in prod, and was only written last week.
> I'm very skeptic that they read the entire codebase of Bun prior.
Well, they didn't really need to. A complete rewrite is effectively a different project. You may feel comfortable using a new project in prod, but most people are not.
Project A: used in production for 3 years - high trust.
Project B: Has yet to be used in production - low trust.
IDGAF about automated tests, let other users shake out the inevitable bugs that show up in prod and after a few years of stability, then we'll see.
To me, it's not about whether humans reviewed the code or not (they didn't), it's more about "here's this brand-new shiny codebase of ~1m Sloc, of which exactly zero lines has been used in prod".
It's not impossible, or even that hard to review the entire rewritten codebase.
10 engineers each reviewing 5,000 LoC a day for 20 days can do it.
And that is being highly conservative with the estimate. A good chunk of the the code is probably highly trivial boilerplate one can easily skim over in minutes.
And five engineers reviewing 20 thousand LoCs would get the job done in ten days, but both numbers are just as BS when it comes to actually understanding the codebase. No one is comprehensively reading 5k lines per day for a month straight.
Just because we don't understand or know about compilers or able to read their output does not make them fungible.
In old days we chose between Turbo/Borland C, Quick C and GCC. We didn't think them same or trust blindly even if we didn't know how they worked.
The best developers hand optimized assembly for sub routines which they knew compilers were not good at, the rest of us sure didn't understand how any of it worked, but nonetheless felt the differences and chose with dollars and usage .
I'm certain that the maintainers of Bun have excellent understanding of their codebase. What makes you think that they don't? They wrote the code in the first place. They know the architecture. They know what pieces do what functions.
They did not write the rust code. AI wrote that code. Your response is side stepping the primary issue people have with the rewrite: no human has read and understood all the code AI wrote.
It’s not like they are discriminating on someone’s race or religion. If they don’t want a major vibe coded surface, do they even have to defend that? It’s part their “artistic” license as developers.
Or did we forget software inherently is opinionated
You don't even have to leave this site: when the original Bun rewrite posts were made, an incredible number of comments were focused, not on Bun, but on Jarred, who I'm assured is a complete rockstar and would never harm Bun.
Unfortunately, his followers don't realize that something like a batteries-included runtime is a huge commitment to build on top of, and governance you can trust matters as much, if not more, than the lines of code.
The way this has been handled is just baffling. A Rust rewrite is supposed to be a freebie for hype, and even an AI rewrite could have been interesting if approached more scientifically and transparently... but instead the opposite of that happened.
exactly... and it's not like it's hard to fork and just raise the minimum version. It will probably be just one number somewhere (I haven't actually looked.)
if it works, it will keep working. they just don't want to support and maintain it and solve issues.
Yes, it’s actually similar to discriminating based on race or religion, in the sense that it’s an arbitrary, meaningless criterion to discriminate on. If the Rust Bun port is better in every measurable way — passes all tests, has the same performance or better, and fixes existing bugs — then who cares what language it’s written in or how it was implemented? The point is that it’s higher quality. If you don’t trust the Bun team when they release a Rust version and give it their stamp of approval, why did you trust them when they released the Zig version two weeks ago? It makes no logical sense, and it makes the yt-dlp devs look foolish.
> If you don’t trust the Bun team when they release a Rust version and give it their stamp of approval, why did you trust them when they released the Zig version two weeks ago?
I think you cannot make this comparison because Rust version wasn’t in fact written by the Bun team. It wasn’t even read by them.
Yt-dlp devs made a good call. If Claude is good enough to rewrite millions of lines of Bun, it is good enough to maintain Bun fork of yt-dlp. And since Bun is part of Anthropic, they can afford it too.
people don’t care if it’s good. they only care it’s made with AI so they can signal their moral superiority. hence the derogatory term slop that is paraded around like it’s the way to win an argument
It's just more reactionary "AI bad." The tech world is rapidly splitting into people that "get" AI and people that bizarrely still resist it because they are stuck with a 2024 understanding of what AI can do (and never bothered to update their priors in earnest.)
Oh well, I really like using Bun and I get kinda sad about the turn they are taking after the Anthropic acquisition. I really want a good Node with batteries included, but I don't want it vibe coded.
Have there been any significant issues caused by the vibecoded translation?
To be clear, I'm not implying support for the merge. I am against this whole YOLO approach to engineering. Just curious how the switch is going since I haven't seen any news since the merge announcement.
IMO the source of the new code is less important than the sheer volume of it. Bun does not need to be entirely rewritten; certainly not over a period of a week, possibly not even over a period of a year. Stability is hard-fought and battle-tested. Everyone has a plan until they get punched in the face; and every repository has passing tests until it runs production code.
Epistemically: if it can be so easily vibecoded to rust, why can't it be vibecoded to be reparted? Isn't the great and Almight AI unable to parse and repair Zig? Identify it's weak points and route around it?
I think it's hilarious how hopeful people were at the acquisition that Bun would be able to continue on mostly as it had been but then that all got completely thrown away and trashed.
(Hilarious in the way that's terribly sad, of course.)
Not necessarily, but I don't trust Anthropic in making sure it doesn't become worse. They are already doing a terrible job with their own Claude Code CLI.
Unless specific issues have been identified that were introduced by it being "vibe coded", isn't a reaction to reject it outright without actually checking the ground truth just exhibiting the behavior you are criticizing?
It's just a trust issue. Have you seen the absolute state of the Claude Code CLI development? I don't want that to suddenly happen to Bun after I've already used it for production stuff.
I don't see any hypocrisy in the comment you are criticizing. The behavior they are criticizing appears to be vibe coding. How is rejecting something for being vibe coding "exhibiting the behavior" of vibe coding?
The ground truth is that the new maintainers can’t possibly have a good understanding of the many millions of lines of vibe-translated code. Even assuming that the code happens to work okay in its current state, the lack of understanding means a high risk that its continuing maintenance won’t result in a satisfactory level of reliability.
I'm not sure what "exhibiting the behavior you are criticizing" would even mean here.
BUT.
"Ignore anything but actual problems" is a terrible stance to take generally for software and dependency selection. Incidents are fairly sparse, process is much easier to observe. So if you can find connections between process and incident possibility, that's a very reasonable heuristic. And it's easy to find examples of overaggressive LLM usage introducing problems into software.
This is about the rust conversion but that has not been released.
> Due to foreseeable compatibility and security issues
Hmm, Zig bun crashes plenty.
I wish yt-dlp linked to detail on why there are foreseeable compatibility issues. Both projects have test suites, in an ideal world they would allow fast rewrites.
Maybe they want to limit inflaming the situation, but if they have spotted some specific issues it would be good to see.
I hope Bun.rs is 1.4 or even 2.0 and not a minor release, with some alpha/beta releases.
Yep, it's one thing if there was some project that saw severe regressions in Bun.rs and actually showed data about regressions.
But it's been available for a week. And so far, seems like crickets on actual data on any regressions. It's more "I just don't like this!" style grumbling.
They could at least wait a bit, test the new Bun for some weeks/months, have people read big chunks of the codebase.
It should be a major release indeed, and communicated as such, with full accountability of the migration beyond an “all tests pass”. A major tool should move slower, be tested longer, more thoroughly, since it’s used my millions.
It’s reminiscent of JavaScript world, where something is in beta for mere days (e.g. Expo’s short release cycle).
Why are some people so pressed about this decision? From my point of view, if you're truly a vibe code enthusiast wouldn't you be able to just vibe code your own better yt-dlp (or fork the existing one and do whatever you need to do with it)?
Indeed. I've heard a lot of words about how trivially easy vibe coding makes building software, and how just about anyone can build something in no time at all anymore. Even stuff about how people will vibe code one-off private software for everything at all times, and such.
There really shouldn't be a reason for vibe coders to complain about any software decisions. Vibe coding a personal fork you better agree with should be a piece of cake. Isn't that part of the vibe code promise?
What's more is yt-dlp already has plugin support for 3rd party interpreters. They're just saying they don't want to deal with supporting bun themselves and the infrastructure for anyone else do use whatever they want is already there.
This is just the standard misguided entitlement people feel towards other people's projects supported by other people's time and effort. It's continually outrageous to me how people feel they can just volunteer other people's time and effort to support their own wants. The people who do the work are entitled to make their decisions and if you don't like it fork it yourself. This has been the way of this ecosystem since it started.
Because for a lot of AI fans (not all, I know), it's like a religion. They aren't content to live and let live and let history show whose approach to building software is better, they insist that everyone has to agree with them. I have that situation at my job and it drives me insane that honest technical disagreement isn't allowed when it comes to AI.
I speculate that I could indeed "vibe code" a better JS build integration because what they have does not make sense at a first look.
It appears they mixed JS building into their python project, aiming to support multiple package managers which are executed from their python script.
This explains the otherwise non-sensical explanation about bun < v2 ignoring the lockfile: they use a separate lockfile for each package manager. They did not check in one for bun v1, which they claimed to support, consequently it is not using a lockfile.
That's not how JS packaging normally works. I would set up a separate folder for the JS project, and use one package manager to build the project, like anyone else does.
Publish the package to npm, or bundle the tarball with your python program.
I guess the permission model of the JS runtime could be another topic, but at least they would have their build fixed without worrying about Node dependency resolution and package managers in their Python code.
We desperately need some new terminology to describe using LLMs to support development work. "Vibe code" has a strict definition but no one really cares. I have a really hard time believing that the Rust port was 100% "vibed" the way the original definition was laid out.
It's a big slushy of emotions that I understand (both positive and negative) but it makes it so hard to actually tells what problem someone actually has when they just use "vibe coding" as a general LLM usage slur.
I'm using LLMs to assist my development and I'm measurably (in all the ways we engineers could possibly care about) doing better work faster.
I'm using LLMs to assist my development and I'm measurably (in all the ways we
engineers could possibly care about) doing better work faster.
Studies suggest you aren't any faster and may in fact be slower. It's difficult to study such a new tech, but even optimistically, empirical evidence is only showing a ~3% gain in some domains.
Writing code is rarely the limiting factor in our work.
I think those studies have framing or methodological issue.
I agree the maintenance burden is probably being undervalued by developers in general, but there's just no way the work I do isn't faster. I just categorically couldn't have achieved the outputs I do now in the time windows I have. The software just wouldn't have existed in the world of 3 years ago and I did enough coding back then to say that with certainty.
In the past 18 months I've seen experienced developers turn out incredible work using llm-assisted tools, over and over again. With the right harnesses, processes and result-oriented testing, you can simply produce so much more high-quality work.
I know it's anecdotal, but I have so much data from my own experiences and those of my peers that I know these new tools are here to stay. It also makes me believe that those studies are either flawed or out of date.
There's no uncertainty here. Every day I ask myself how long something I did would have taken without it. The answer is always crystal clear. It's not hard or difficult at all.
studies suggest nothing. i've released a massive number of features in the last year for several projects that i estimate would have taken me multiple years to put together in a much more mentally exhausting way.
This decision seems to based more in politics than engineering. Have you observed Bun have more segfaults, OOMs, etc, since the Rust rewrite? Have you noticed more security vulnerabilities? Have you seen more bugs? (Of course you haven't, the rewrite hasn't even landed yet.) It seems that you are making this decision because you get a bad feeling when thinking about AI involvement.
I don't select my engineering tools because they give me a bad feeling - I select them because they do the thing I want them to. If Bun starts having more bugs and feeling like worse software, I'll stop using it. But I will base that on data -- not a feeling I have. Jarred has done a lot of impressive stuff with Bun, and it seems unlikely he would ship this rewrite if it didn't meet his quality bar - I am willing to see him out here.
> Have you observed Bun have more segfaults, OOMs, etc, since the Rust rewrite? Have you noticed more security vulnerabilities? Have you seen more bugs? (Of course you haven't, the rewrite hasn't even landed yet.)
On the flip side it's not on the yt-dlp authors to test Bun's new development process and see if it results in more segfaults, OOMs, security vulnerabilities, etc. In fact it would arguably be negligent to experiment on your users if you thought there was a reasonable probability of increased security vulnerabilities.
I think there's a good argument that the responsible thing to say would be "we aren't going to immediately support running our software on a new bun release cut from main right now".
It seems a bit unfortunate to me that they've apparently already intending to never support future releases instead of planning on re-evaluating in the future. On the other hand the yt-dlp developers definitely don't owe anyone anything.
> It seems a bit unfortunate to me that they've apparently already intending to never support future releases instead of planning on re-evaluating in the future. On the other hand the yt-dlp developers definitely don't owe anyone anything.
I think your final comment gets at it. If they said "OK, I am skeptical, so we're going to pause on updating to see how this Rust thing plays out" -- that sounds like a reasonable engineering decision. Saying "because they vibe coded we are dropping support for Bun" sounds political.
> It seems a bit unfortunate to me that they've apparently already intending to never support future releases instead of planning on re-evaluating in the future. On the other hand the yt-dlp developers definitely don't owe anyone anything.
The other side of this is that as far as I'm aware, Bun support in yt-dlp was always experimental. They mainly use Deno.
It's not really political. Or let me rephrase possibly yt-dl is being political. VUT the concept of 'not adopting a core dependency until it has been widely used in production for 6 months - a year.', is not a political on general. A full rewrite of 1 million loc is essentially a new runtime that has the same ABI as the previous and for many downstream consumers it's not something they are comfortable taking a production dependency on. If for sale of argument BUn was fully rewritten by hand would be the same situation. I personally think this kind of decision is pretty standard, I also personally think the Bun LLM rewrite will be of good quality overall, but I certainly would not bet my product/company on it. I want to be the one making the risky changes on my software not being forced into it by downstream deps.
I think your stance is more reasonable than the one in the article, TBH. If yt-dlp said something like "We're going to wait 6 months on the Rust rewrite", that would be reasonable. But instead it says something more like we think that Bun is vibe-coded, so we don't want to use it any more. That seems less reasonable.
Even re-written by hand isn't the same because a hand re-write proceeds slower over a longer period of time with more smaller updates that get tested somewhat along the way.
Also I don't think it's wrong to use an action as an input to judging engineering character. That could be read as judging yt-dlp or judging bun but in this case I mean it's reasonable to judge bun's developers.
IDK if i'd personally judge this action quite so badly though. It depends how they went about it and what they proffessed to get out of it.
I am very much against letting llms think and decide for you, but I don't think it's so wrong for an actual coder to employ automation.
But if they are acting like it's magic and everything will be so much better after the magic llm uses the magic safe language... yeah that definitely gets the side eye. Or no eye. Just no longer interested in or concerned with their output.
Since this is being offered as the next release version while still being new and stuffed with unsafe, looks like it's the latter. So I'm with yt-dlp in this case.
It doesn't matter if the new code happens to be ok or not, it's still a problem that they got there by hoping a black box does the right thing. A black box that that no one wrote and no one understands, not just themselves.
gcc is a black box to me, but I know that someone wrote it and understands it (or some people collectively understand all it's parts), and I know that any time I want, I can choose to understand any part of it, and satisfy myself that it is doing something both sane and deterministic.
So a developer choosing to use gcc when it's a black box to them does not reflect badly on them to me.
But no one can say that about any llm or ai. So yeah, a developer choosing to use them, depending on exactly how, may reflect badly on them.
The same was true for cheap off-shore gig coding by humans too. I have tried to use them myself in the past, hire out for small generic programming jobs using those web sites where you put up some escrow money and post a job and people bid for it, you choose one, they do it and get paid from the escrow. I only tried about 3 times for the same small job and every time I git ridiculously shit (but technically functional) results.
These were humans 15-20 years ago, no possibility of hidden ai usage like today, and it's essentially the same dynamic of just hoping some magic will get you something good for cheap, and accepting any result that appears good as good.
If someone said that that's how they made their product, I would decide that product is probably pretty crap inside and no way should I buy it or invest in it as a dependency if I have any choice.
And that's humans not ai. The problem isn't really the ai, it's the judgement to use an ai that way.
If you wait for more segfaults, OOMs and other issues, than you have failed to avoid the problem. In my opinion this direction is correct and history will show who's right.
When expressed, sounds like a trivial principle. It's surprising how rare it is to see people actually do this.
Not only with tech stack: choosing cars, laptops, staying in a toxic relation, the list goes on
Notably, they aren't (yet) dropping support for older, pre-rewrite versions of Bun. They also could be leaving the door open to support Bun in the future, if the rewrite proves successful. I think waiting and seeing is the right, conservative move.
A key element of engineering is projecting a current trajectory. Given that, it absolutely makes sense to avoid tools that give you a bad feeling. The easiest time to move away from a tool that will become a train wreck is before you've integrated it.
But what exactly are you projecting? Typically when people have said they have a bad feeling about something (imagine Next.js) it's because they are running into more bugs or they are seeing more production incidents. In this case there has been no chance to observe these things.
> This decision seems to based more in politics than engineering.
Project governance is very important on a project; the fact that Bun's authors bent the knee to their new owner shows where their priorities lie.
> Have you observed Bun have more segfaults, OOMs, etc, since the Rust rewrite? Have you noticed more security vulnerabilities? Have you seen more bugs?
I - them - are not going to sit around waiting for bugs to start crashing everything
> I don't select my engineering tools because they give me a bad feeling - I select them because they do the thing I want them to
Good thing that you don't run an open source project then, I would remove anyone's project from my dependencies who thinks like that.
It really is amazing to me how many developers do not understand that governance is important. If I have a dependency and a maintainer of that dependency has a process I can’t trust, it’s perfectly valid to remove that dependency based on that lack of trust.
Not caring about governance is how we end up with repeated supply chain attacks.
Then Bun's rewrite is also political. They couldn't upstream their vibe coded "improvements" so in spite they decided to vibe a rewrite in Rust. The arguments for the rewrite were not backed by any data.
> They couldn't upstream their vibe coded "improvements"
What are you talking about? There is no upstream rejecting contributions here. It's the original bun developers who vibe-ported it to rust and they absolutely could and did upstream their vibe coded changes because they are the upstream.
Every single macOS update the top comments are about giving it six months to stabilize, but when a program’s biggest ever rewrite involves a lot of AI, the top comment is calling you irrational if you don’t YOLO it, and probably a jerk, too.
But this also isn't a fair comparison. The article doesn't say "let's wait 6 months", it says they are fully deprecating Bun. Those are two very different statements. I would have had no issue with the first.
And FWIW I think my viewpoint is the uncommon one. Look at all the responses to a previous thread about it [1] and see how many of them are negative. It's certainly a majority.
YOLO? Bun has an extensive test suite and this implementation passed the test suite.
Can we at least try to be a bit more accurate and less hyperbolic?
I will continue to use Bun because the same people that made bun have made this decision. I trusted them one week ago. I have used bun for the past 2 years, and so have many others.
I'm not about to just assume they've become immature idiots yolo'ing stuff overnight. They're still the same people they were a week ago. Or two weeks ago.
I don't think refactoring 1M lines of code into another language within 7 days and merging it to master is responsible. I won't make my code depend on it.
Every decision is made with imperfect information about the tool, its future, and your current/future needs. This is a normal type of engineering decision.
Bun being replaced entirely with stochastically generated code is red flag (regardless of whether it was or not). But Bun was also acquired by a huge corporation, which has been classically a huge red flag. Both of these are plenty of reason for yt-dlp not to support Bun.
In either case, this seems like a niche use case. I've used yt-dlp for years and I've never used Bun with it. If Anthropic really wants their recent acquisition to be supported in yt-dlp, it can fork it and support it itself.
FYI in case you aren't aware, the rewrite was shipped, and then had to be reverted due to issues being discovered. That's "Jarred's high quality bar" you're so confident in.
Reading and understanding code is more difficult than writing code.
It is significantly easier to modify code that you personally wrote, or code that you have read and understood to fix an issue in previously. This is why the maintainers of a project change slowly over time and it takes a long time for new ones to get up to speed.
All of Bun has been rewritten by a tool. In a different language that maintainers may not be fully proficient in.
Even though the rewrite was done well, and even if we assume it's functionally equivalent to the old Zig code, there will still be future issues. And ALl of the maintainers are essentially now new hires who have never seen that code in their lives.
It's not "politics" to have an ounce of sense to foresee problems in such a project as a dependency.
Jared has shipped a lot of things that have impressed me. His software is measurably faster than the alternatives, and I have measured it. It runs code that Node et al can't run, and I have tried. These are normal, everyday experiences with software - based in fact, not vibes. I'm not going to argue every decision he's ever made is amazing, but his decisions have historically tracked above average.
When deciding to support a given thing, you have to make a determination as to whether it's worth the effort or not.
You don't simply ignore unknowns. That effectively means assigning the unknowns zero cost, which is unlikely to turn out to be true. Generally, the more unknowns, the higher the risk, and the higher the risk, the higher the estimated cost.
There are a lot of unknowns about vibe bun right now.
One effective strategy for dealing with unknowns is to turn them into knowns if you can. Here, that probably means waiting to see how vibe bun turns out.
If it turns out to be stable and highly compatible, at some point in the future, they can always pick up support then.
> it seems unlikely he would ship this rewrite if it didn't meet his quality bar
What happened to
> don't select my engineering tools because they give me a bad feeling
Who cares if you have a good feeling about this dude? There are obvious and clear conflicts of interest at play here. If you care at all about quality, you'll wait before adopting new releases until bugs get discovered/ironed out. Don't adopt based on some dude's reputation when that reputation was built under a very different incentive environment.
> I don't select my engineering tools because they give me a bad feeling - I select them because they do the thing I want them to. If Bun starts having more bugs and feeling like worse software, I'll stop using it. But I will base that on data -- not a feeling I have.
being reactive is fine if you can tolerate issues. otherwise, you need to be proactive -- don't wait for the train to hit you before you move off the tracks
I wouldn't call it politics. I've seen enough people aim a gun at their foot and pull the trigger. They'll never thank you for stopping them, they just want to be left alone while they do it.
So, great, if this dude wants to regress through the workforce to a level of engineering maturity I associate with a high school student, I don't wish to try to be the one to stop him. Doesn't mean I'm gonna follow him. It's possible to be smart enough to just not walk into the tarpit. He's going in, I'm not.
> I don't select my engineering tools because they give me a bad feeling - I select them because they do the thing I want them to.
With that in mind, is there anything that yt-dlp uses the Bun runtime for which it can not use the other supported runtimes for? Similarly, perhaps the yt-dlp maintainers shouldn't keep supporting Bun just because it gives them a good feeling when every runtime incurs a maintenance cost.
That said, as a developer I skim over so much bullshit simply based on "bad feelings". I don't have time to evaluate every potentially useful technology in terms of whether it does what I want it to do, and no one else does either. It's clear to me that Bun is in an experimental phase of development and I think that's a good enough reason to move on if your use case is not.
This is a good example of what many private companies are doing, and the rude awakening they’re in for with token price hikes and vendor lock in. It’s like Oracle all over again
You can’t really tell if you got sick from dirty hands, a week old egg, or the cheeseburger you had for lunch, but if Shake Shack had also just announced they’ve moved over to vibe-cleaning their kitchens then it’s reasonable to only eat at Five Guys from now on. Let someone else iron out the kinks.
Seems reasonable to preemptively drop support and let someone else either suffer the fallout, or get proven wrong and just pick up support again. It's not for a lack of people motivated by IA. Unless the motivation is more "use my IA generated content" than "actually consume IA generated content", of course.
No one says that? Of course Bun rewrite is political. And if you deprecate Bun support due to they did something political, obviously this decision itself is political too.
Every accusation is an admission, isn't it? As always with these cases, the rhetorical contrast is staggering compared to the thread about Bun deprecating Zig.
Bun made a snap decision to merge 1M lines of unreviewed code within a week, including code generated moments before the merge. AI or not, that forces downstream users to cope with total unpredictability. This process bears no resemblance to science or engineering.
All the QA work you're demanding of yt-dlp is work Bun should've done. Trying to flip that responsibility proves your argument isn't grounded in engineering principles. And you sure made your feelings known in your comments for someone who claims not to let emotions affect technical decisions.
yt-dlp made a sane technical decision to drop a high-risk dependency. Not only is the Bun code now unpredictable, but the maintainer is too. The maintainer called the rewrite "experimental," then merged it within a week. If direct statements can flip overnight without warning or explanation, it's no wonder downstream projects want out. Especially when yt-dlp already supports alternative JS runtimes.
> This decision seems to based more in politics than engineering.
I'm glad some engineers realize that technology is inseparable from politics. It always has been. All evil came from engineers who beleived they were above politics. Selecting the tool which got the job done/made the number go up/paid a paycheck is how we got Facebook, Google, Palantir, crypto, AI, techno-fascism and neo-feudalism. None of it would've have happened without engineers blindly applying their knowledge to achieve "purely" technical results, while ignoring the social consequences. With the hindsight of the last 20 years, anyone who still advocates for an irresponsible adoption of technology should be considered automatically suspect
> I don't select my engineering tools because they give me a bad feeling - I select them because they do the thing I want them to
Among tools that meet a technical expectation—especially for (often) superfluous activities like downloading videos—I pick one that feels right and costs the right amount, and that's the one that wins. Free + works + usable is an unbeatable combination.
However, I'd argue their decision is related to a peer dependency than it is itself one about an engineering tool, which is an assessment of the risk surface and potential cost associated with doing so. I already wasn't using bun at all, but if they stopped supporting whichever runtime I do use, I can either adapt or stop using yt-dlp, which I won't because this isn't a technical thing worth wasting much time on. This mild, recent change to recently introduced peer dependency integration is largely inconsequential, and I support the call to not waste time providing extra support if it hypothetically became necessary.
> I don't select my engineering tools because they give me a bad feeling - I select them because they do the thing I want them to. If Bun starts having more bugs and feeling like worse software, I'll stop using it. But I will base that on data -- not a feeling I have. Jarred has done a lot of impressive stuff with Bun, and it seems unlikely he would ship this rewrite if it didn't meet his quality bar - I am willing to see him out here.
I have a t-shirt signed by THE Jarred himself, how much are you willing to pay for it? Comes with a month of free Claude max subscription.
the bun team has recently demonstrated a lack of agency over their project. making massive structural changes with unclear and misleading communication. There is nothing political about seeing that as a red flag and deciding to rely on more stable projects.
I have no idea how that’s what you get from this. I don’t want my project using any tech that decides to take 6 days to rewrite the entire library with AI. That is at its core an engineering decision.
No healthy engineering team is going to do that. And I’d want to distance myself as far as I could from a project that behaves like that.
> I select them because they do the thing I want them to.
Regardless of the other aspects, this is a joke in any context I have been in since I started working in this field about 9 years ago.
Even as pure logic, you know they do what you want it to do only after you chose them. You can’t possibly be trying every option to the fullest capacity of your application.
You also converge on the “Jarred” aspect and the guy that made the decision in the title post has the opposite sentiment
> Have you observed Bun have more segfaults, OOMs, etc, since the Rust rewrite? Have you noticed more security vulnerabilities? Have you seen more bugs? (Of course you haven't, the rewrite hasn't even landed yet.)
Your argument could go other way too. Why haven't they landed if they're so confident with the change?
> I don't select my engineering tools because they give me a bad feeling
I do, for example when I see constant behavior of lying, or negligence for security issues or not considering valid PRs and rewriting it to fit their paid plan and so on.
> I select them because they do the thing I want them to.
This is one of the dimensions when I pick the tools, I know Oracle produces nice products, but I don't want to get sued if I do something accidentally their lawyers dislike.
So, let's see here. Here we have a program, that is used to install scripts from source that has been targeted, and breached multiple times last few months, can run arbitrary code on millions or billions of user computer, servers. And, it was ported to another programming language, resulting in 1m LOC, in 7 days for publicity stunt of a LLM company
Even multiple people can not go through 1m lines of code for any kind of vulnerability in 7 days, let alone 'observe' more segfaults, OOMS, unsafe behavior, on who knows how many possible ways things can go wrong in this new condition.
Only guaranty is 99% tests passed, and the engineer who is paid by the same LLM company.
How in the world, any sane engineer would agree, this would be remotely a good idea to continue using this tool, for a chance that such a expensive change won't actually land in production?
As far as I'm concerned Bun has been extremely irresponsible with this entire rewrite, and it calls into question their entire development philosophy. Any project that cares about stability and reliability should steer clear of Bun for a while.
> I will base that on data -- not a feeling I have.
and yet...
> If Bun starts having more bugs and feeling like worse software, I'll stop using it.
Is it not possible to judge that certain approach is more likely to bring unforseen controlable problems than another by analyzing how it works without assessing it's output? No "feeling" is needed
Yeah this is a cringe way to weigh in on something completely unrelated to your project. Who cares if some random package supports Bun? Compat was always on Bun, anyway.
I believe you contradicted your first point by following it with "If Bun starts having more bugs and feeling like worse software"
...so you do use feelings in your calculation? To be clear, I have no problem with that and think there is some level of speculation you need to do when deciding what to rely on.
As a hypothetical, pretend that Bun added obfuscated binary blobs that get executed at build time. Well, your code still works and no effects show up at runtime. Are you going to keep using it or dump it based on the "feeling" that something isn't right?
A merge to main itself is pretty substantial, especially a week after saying, "[This] code that does not work. We haven’t committed to rewriting. There’s a very high chance all this code gets thrown out completely."
> This decision seems to based more in politics than engineering.
You are 100% right. This is a decision made on VIBES and not evidence. The proof is here:
> Bun was recently rewritten in Rust using Claude, and its development seems to have taken a turn towards being fully vibe-coded. This is alarming and disappointing for a number of reasons, and frankly it seems like a future headache that we'd prefer to avoid.
They haven't tested it, they haven't found a single problem. They just don't like AI code and they're clearly saying "the fact that the project tested every line of code and it passes all tests doesn't matter to us. The fact that it's vide coded by people who literally make coding LLMs also doesn't matter."
> They haven't tested it, they haven't found a single problem. They just don't like AI code and they're clearly saying "the fact that the project tested every line of code and it passes all tests doesn't matter to us. The fact that it's vide coded by people who literally make coding LLMs also doesn't matter."
Pure ego, no data.
So an OSS project now owes testing to hyperscalers? Lol!
So many people in the comments here are making assertions about the quality of the rust re-write but the point largely remains the same. There is no way you've read all million LOC in the time and reviewed to make sure it really is transpiled. It's not a criticism of the method, but the time and review process.
To be honest, I share primeagen's view that LLMs handle translating code from one language to another quite well. As far as I know, they converted the languages file by file. This is what led to such a high volume of `unsafe` code. Although, in any case let's be honest, this is causing, and will continue to cause, various issues. I find it easier to live with this point of view.
He was a software engineer at Netflix before turning to content creation. It is also clear watching his videos that he knows his thing. As an experienced programmer myself, I find his commentary to be way too relatable to be just bluff.
He may not be Don Knuth, Linus Torvalds, John Carmack or Fabrice Bellard. But he is definitely a serious programmer. That he livestreams doesn't make him less of a programmer.
Identifying where code is unsafe, is a qualitative improvement. Not guaranteed to be complete, but more complete than a language that does not focus on that concern. Moving forward, the benefits of Rust compound. The concern about AI is orthogonal to the concern about moving to Rust.
Now there are 2 versions[1] that can be instrumented, regardless of the misgivings about AI.
[1] Bun v1.3.14, released on May 13, 2026 (commit 0d9b296af) and current.
I see Bun’s Rust rewrite (esp the style how it was done) as a form of massive internet trolling for PR reasons. By making a bigger fuss about it, we’re feeding the troll
This doesn't really have anything to do with the merits of the languages themselves, but rather with the rewrite being entirely vibe coded. If it had been from Rust to Zig instead of from Zig to Rust, I expect the exact same response would have happened.
On one hand, it seems very scary to me, having most of your codebase unreviewed.
On the other hand, it passes their tests with few regressions from what I heard.
Maybe it's just because I don't have enough experience there, but I wouldn't trust my tests to this degree and completely rely on them without reading the code.
bun was never the recommended js runtime when they first announced its need for yt support [1]. in fact they recommended deno over all, even regular node.
depending on the environment of choice, these runtimes are only used to bypass certain blockers. it is not that deep.
There's literally nothing that LLMs can build that humans cannot. The only factor influencing people to use AI is time. They trade off a small amount of quality for a large amount of time savings. The tortoise and the hare parable comes to mind.
They used to have their own "youtube script interpreter" that was kind of fascinating.
But yeah as you said they switched to proper js runtimes recently.
What they don't need is hardcoding support for five JS package managers in their python files.
In the post the maintainer says that an older version of bun "results in the ejs lockfile being ignored".
The reason is that they never committed the necessary lockfile despite listing "support" for that bun version.
They have separate lockfiles for other package manager versions: bun.lock, deno.lock, package-lock.json, pnpm-lock.yaml.
This part of the comment is also interesting: "which is a significant security concern for users when considering all of the recent npm supply chain attacks".
If you would set up a proper build for the JS artifact instead of committing four lockfiles to your repository, users would not be as exposed to npm supply chain attacks.
Has bun really shipped using a million line vibecoded PR. I know they merged it, but merging something in a new dir doesn’t mean anything compared to what code is actually running for customers. It’s crazy if the vibecoded rust version is what’s running for customers and not just some experimental hack.
Except it's not vibecoded, it's litteraly the best prompt an LLM can ever get - literal code. If the whole thing ends up as a failure, then it will show that the king is naked.
Maintaining compatibility with multiple runtimes adds too much friction for a core tool like yt-dlp. Dropping Bun seems like the right call to keep development focused.
I think this HN submission provides little value and a lot more headache to the maintainers of FOSS project (you can already see a lot of brigading in the GitHub comments). IMHO HN shouldn’t allow submissions like this.
I can’t help but read the logic as not being too far off from: “libfoo switched to being developed using emacs instead of vim so we can’t trust it anymore”
It’s not the same obviously, but here’s why I can’t help but view it analogously:
The only truth in software is whether it works or not for whatever your use case is. Even before AI, we couldn’t have known if the author of a piece of software was proceeding with rigor or just trying random stuff until it seemed to work.
In other words, we didn’t judge someone’s software by inspecting their methodology or what tools they used. Heck, we often ended up using software that had no test suite or where the test suite was junk! And so many of us who are fans of memory safety use tools written in C, and vice versa (I’m no Rust fan but I use plenty of tools written in Rust).
So yeah, the logic that goes, “I won’t use your stuff because I don’t approve of your use of AI” is about as believable to me as if you stopped using something because you didn’t like the authors choice of editor
I don't know how to tell you this, but people actually can and do, in fact, worry about the methods things come to be made with, and make decisions based on if they approve of that process or not. Otherwise the idea of free trade chocolate/coffee/other shit would not exist.
>I can’t help but read the logic as not being too far off from: “libfoo switched to being developed using emacs instead of vim so we can’t trust it anymore”
That's wild. You should read it as being nowhere in the same ballpark nor adjacent ballparks as that.
> I can’t help but read the logic as not being too far off from: “libfoo switched to being developed using emacs instead of vim so we can’t trust it anymore”
So let's say they up the ante and set up a cron job to rewrite the entire codebase in a new language on the first Monday of every month: from Rust to C++ to Go to Swift and back again.
For customers using the product, that's basically the same as a maintainer switching editors? Irrelevant detail?
Most people probably think the text editor used would have no meaningful effect on the code written.
I don't think many would say the same for LLMs.
Maybe vibe bun is just as good or better than old bun, but how would we know at this point?
> ...we couldn’t have known if the author of a piece of software was proceeding with rigor...we didn’t judge someone’s software by inspecting their methodology...
That's not true. First, some people do directly check whether a project has a level of rigor they are comfortable with before adopting it (or when deciding whether to continue using it). I personally do it, where it matters. Many more use reputation signals, which, while certainly not perfect, correlate, may be good enough, and are a lot easier than direct, manual reviews.
There is no generic “JavaScript runtime” interface that runtimes would implement, therefore support must be tailored to the specific interfaces of existing runtimes.
Google did something similar with golang. Of course it was a tool based rewrite and they did lots of tests but some bugs still emerged. People should stop being mad about a company that delivers a tool that is about shipping software faster. The world does not resolve around high quality software, the world resolves around things that might need a reboot every other day, that was never touched for over 2 years. Things that somebody did once and it worked but most people do not understand it because of the aweful code.
Yes of course we still need high quality code in some parts, but most parts of the world is already running on software that is way worse than modern vibe coded things
Lol! Fuck around and find out. There were dozens, “well, if you don’t like it – don’t use it”, “they don’t owe you anything”, “it’s their project”, etc., etc. Nice to see the consequences.
zig is barely adopted relative to rust. totally reasonable to move to Rust, which isn't as risky of a bet. and you're not the guy having to find their zig memory leaks.
I don't use Bun, but we (and many others) depend heavily on numpy. It's been around for decades and heavily battle tested. If someone came out with a new version of numpy vibe-code rewritten in a week, with assurances that "all tests pass", do you think we would adopt it? Absolutely not. We would have no confidence that there aren't some latent bugs or that we can fully trust the results.
It has nothing to do with AI having rewritten it, it has to do with being battle tested over time. If a team of humans had rewritten it in a week, I wouldn't trust or use it either. Maybe after a year of it being widely adopted. Not before.
I assume they need to do a bunch of WebAPI bullshit to get around Youtube's draconian policies, but maybe one day https://txikijs.org/ will solve all problems with embedding javascript. I believe, and maybe the strength of my belief will be enough.
Bun was just one of multiple JS runtimes supported, so dropping them doesn't have user-facing consequences. The people posting militant comments here and harassing the maintainer on GitHub are fighting for Anthropic instead of trying to raise any legitimate concerns about yt-dlp.
Bun’s source code rewrite from Zig to Rust was executed primarily through AI-assisted development using Anthropic’s Claude agents, specifically within a branch named claude/phase-a-port. The project creator, Jarred Sumner, merged the massive pull request (PR #30412) on May 14, 2026, which involved over 1 million lines of code added and 6,755 commits completed in roughly one week.
Claude is a model provider: they have many models. It would be interesting to learn if the models used were Sonnet, Opus, Mythos, some other internal unreleased model, or some mixture of them.
Do you also install pre-alpha revisions of operating systems on your main work pc? No, you do not. Why? Because of the "foreseeable compatibility and security issues".
"Well, why don't you install and only then resolve issues if you have those difficulties?" most comments here are asking, in effect
Cause you're sane, that's why!
Same here. yt-dlp does not owe it to anyone to beta test things. Maybe this bun rewrite will be the best thing since sex, and maybe it won't be. Not wanting to alpha test someone else's shit is sane. And the bugs (if any) would go to yt-dlp, forcing them to debug someone else's alpha software. This is a sane response.
I don't think it matters how code is produced -- it matters what it achieves. Is there evidence that there is something wrong with recent Bun releases?
I think one of the big disconnects here are the competing views about "what it achieves" means on a fundamental level.
There's the "what it achieves" today; software x works as intended as of right now.
And then there's "what it achieves" long term.
Those with significant experience with sprawling, LLM-generated, codebases, often built by those who don't understand the code produced, can attest to things being good today, unworkable tomorrow.
While this isn't true across the board, and my own experience should be considered anecdotal at best, those who consider "what it achieves" to also include long term viability as a success metric, are skeptical of these types of changes.
Personally, success for dependencies isn't just "does it work today" but "can I trust it to work long term."
I don't use Bun. I don't care about Bun. But my opinion is that how code is produced will have some effect on what it achieves, if the goalpost includes more than "it works today."
Deno's LLM contributions have been smaller in scope, so they're more likely to be reviewed by a human, and the codebase remains understood by its contributors. Can the same be said of Bun, which switched to an entirely different language in a single, million-line PR?[0]
I see a lot of commentators in this thread who are aggressively critical of volunteer maintainers for making a decision about how to maximize the value of the free labor they donate to the world.
And yet none have offered to volunteer their time to maintain a downstream fork or otherwise rectify the perceived problem.
All dependency management is speculative. You've got to hedge your bets that the dependency is reliable and fit for purpose. It is reasonable to view Bun's recent choices as increasing the risk associated with depending on it.
Very much agree. Until the vibe-coded version has been fully audited and profiled to perform, within reasonable tolerances, as well as the original code base, it feels like a bad idea to support it downstream or use it in production.
Really?? So you base your engineer in "speculation". The Bun team has a deep track record of delivering a high quality product. What makes you think that is going to stop?
In this case, the speculation ostensibly is that in future, there will be a release version of Bun that has is buggier or otherwise lower quality than the current stable version.
There's literally no basis for believing that. The actual basis is "I don't like how they're approaching the development of their next version."
If that's a valid basis for "dependency management", then using a Ouija board would be just as valid.
It's a common fallacy among tech folks to believe that every decision can be made from 100% deterministic grounds ("X decision will result in Y percent change"). In reality, successful decision-making often involves speculation. The speculation in question is within the bounds of reason. You may disagree, but the fact that it is speculative isn't the problem.
And not acting while doing the whole analysis to reach close to 100% deterministic grounds mis a decision in itself! It’s perfectly reasonable to drop support for bun, and potentially revisit later on when more details come up
What part of the recent history of vibe coded projects has not resulted in low quality, bug laden code? Dismissing this a "purely speculative" is just like dismissing the weather report as "purely speculative" when deciding what to wear in the morning.
Low quality, bug laden code has existed long before LLMs and it'll continue to exist long after. Their rationale about avoiding future headaches could literally apply to any open source project they have a dependency on.
Vibe coding from scratch is far from translating an existing app to another language.
I don't know any bad stories about ai-translated apps. Partially because it's a relatively new trend, but also because a big amount of usual vibe code fail modes are not applicable here.
It's a reasonable decision to not take a dependency which doesn't meet your own engineering standards. People in the JS community could learn something from that.
bun is still supported for specific versions so nothing is being thrown away. in any case the actual code is the same, since it's all javascript. it's more a matter of the wrapper code that calls the different runtimes and maybe some edgecases where the runtimes are not 100% compatible.
Honestly I hope agentic AI ushers in a new age of minimal-SBOM software. I myself am moving all of my projects towards nearly 100% vanilla where possible. For example, golang. Why use [insert web framework] when you can just use vanilla for 99% of web apps?
There's something really satisfying about a go binary with minimal dependencies running in a busybox docker container.
"A little copying is better than a little dependency." - Go Proverbs [1]
Most complexity is unnecessary. Adding dependencies to your project exponentially increases your project's surface area, which in turn increases its regulatory/cybersecurity burden, especially if your software is a medical device, munition, etc. Why is Echo/Gin/Gorilla/etc better/more secure than vanilla Go's mux? Just anecdotal, but we use the Echo web framework for Go and it's caused nothing but headaches. It does magical XML parsing by default even though we don't deal with XML which gets us flagged in pen tests. Updating from v4 to v5 broke production for us because they made an undocumented server config change that makes all requests have a 30 second timeout. Meanwhile vanilla go has the ability to register routes and middlewares, so what value is Echo bringing to the table? Ditto for lots of other unnecessary dependencies. A lot of times we just need one little thing out of the whole package, and in those cases a little copying (or a little AI generation) is better than a little dependency.
A static go binary with minimal dependencies running in a busybox container has a tiny CVE footprint when run through grype/snyk, etc. Do the same for a NodeJS app with zillions of dependencies running in an ubuntu container and you'll spend all day triaging CVEs.
I'm not saying "roll your own crypto" but I am saying "axios-like packages don't make sense to use any more in a world where AI+vanilla accomplishes the same thing"
Wouldn't that be worse? With dependencies, it's at least possible that someone else has audited the code, but with a vibe-coded from scratch app, it's definitely totally unreviewed.
I never said AI code should be "unreviewed". I'm saying that instead of pulling in axios or requests (as a contrived example) to make HTTP requests, just use AI to generate some vanilla JS/Python that has the exact subset of functionality you need. Your code has fewer dependencies, CVE surface area, etc, wins all around.
> There's something really satisfying about a go binary with minimal dependencies running in a busybox docker container.
Go binaries are immensely satisfying, but I don't follow your logic here. The vast vast majority of dependencies in Go do not depend on the outside world, so the binary would remain self-contained whether it has 1 or 100 dependencies, no?
Assuming you disable CGO, yes, the binary is always self-contained. However, I want to clarify a few things.
The "self contained" part is only important in that it lets you use busybox or "from scratch" as your container runtime environment which has a very tiny cybersecurity surface area compared to, say, ubuntu or even alpine which has a bunch of system libraries your go binary isn't using, but which could still get flagged for having vulnerabilities.
Minimizing dependencies of the go binary is a separate, but equally important task that reduces the cybersecurity surface area of your go binary itself to just "the go standard library" instead of "go stdlib + a dozen github packages"
Whenever I am working with a NodeJS project I pity the fool who has to do SCA because the CVE surface area is enormous compared to go, which has a fairly batteries-included stdlib
That must be why so many vibe-coded UIs have awful UX (terrible contrast, too small fonts, everything gets its own colors, no attempts at standardized behaviour)
To me it feels more like the old "this site only supports IE6". Instead of checking which JS engine the user has, check for specific api support and fail gracefully.
I understand their decision. How could the maintainers understand their codebase if most of it was not directly written by them?
It is impossible to review the entire rewritten codebase. There are just too many lines of code, 1 million lines to be exact [1].
[1]: https://github.com/oven-sh/bun/pull/30412
Completely regardless of how the code was written or even if anyone understands it thoroughly, they replaced the entire running codebase in a week. The entire project was one thing and is now something different.
There are countless reasons that this is a very bad thing for consumers of Bun. First and foremost you've instantly lost any and all assurance that it works the way it's supposed to. Every project has load-bearing bugs that may or may not still exist. Can you trust the core behavior is the same?
If the Bun maintainers are willing to completely replace their core product over the span of a week, how is anyone supposed to rely on it? What's preventing another rewrite in a few more weeks?
If you want to position your product as a dependency, it needs to be stable and reliable. Throwing away a million lines of code and replacing the entire product overnight is pretty much the polar opposite of stable and reliable.
It has nothing to do with AI rewriting the code, it's the reckless abandon and wild disregard for consumers that is the problem. It's literally a rug pull.
I don’t think changing from zig to rust suddenly means that don’t know what a certain file contains or how it works or how it relates to other files.
It’s all the same just different syntax. Which, by the way, is why it looks ugly to rust developers. The devs wanted the code to look familiar to them.
I do think they should have called this 2.0 though. Would not feel such a rush (1.3.14 has a few regressions, and no one really cares because there are lots of small rust fires now).
Overall, the bigger issue is that bun chases shiny objects. But never finishes. Just look at test stuff. Most of vistest, but not all. Most of jest, but not all. Most of pnpm, but not all. Now we have image stuff, so most of sharp, but not all. dev server? Most of vite, but you guessed it… not all. Long running process… mostly like node but with memory leaks (and a motivation for rust I’m sure).
When I saw them posting about the Image routines my heart sank. Another shiny object. Coincided with test bugs so I moved to vitest completely.
> It’s all the same just different syntax.
That reminds me of Chris Reigrut's story from https://thedailywtf.com/articles/Holiday_Smorgasbord
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I assume most of the complaints about the massive rewrite are in regards to AI, not Rust.
As lots of large and small companies have shown, test suites can only find what you test for. Vibe coded test suites can find?
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> Image routines my heart sank. Another shiny object
With quite a peculiar set of supported formats different between operating systems.
Heh, that would include the tests where the content is just replaced with a single sleep.
> I don’t think changing from zig to rust suddenly means that don’t know what a certain file contains or how it works or how it relates to other files.
What if there was some malicious code within the 1 million lines?
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Pretty normal in many corporate cultures especially ones with high turnover. You get assigned to a team that's "maintaining" a 10 year old code base with few million LoC. The most senior person on the team has been there for a year or 2 and it's just business as usual. You don't know what those 1M+ lines are doing. No one does. It's not a passion of anyone to work on it. You just get a bunch of requirements handed to you, you blackbox everything but the surface areas you need to touch. It's why there are 14 implementations of a background service 8 dependencies that do the same thing, 6 overlapping frameworks, a complete mismatch in style, approaches, etc. It doesn't really matter.
> It doesn't really matter.
It does matter, that's why those people quit because it's such a shitshow, progress happens at a glacial pace, more and more defects and slowdowns keep being created even if they have a big QA department/teams and the users are probably trapped because the software is the only thing in town, the bosses are the ones that makes the purchase decisions, or the it comes attached to big and/or expensive machines and they can't just buy another one for another X years.
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Sounds like a great explanation of why it does matter!
Human-written code is theoretically surmountable.
Large LLM-written code is called slop for a reason. It's hard to understand because oftentimes it does not follow human logic.
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Right. I now have responsibility for rather large codebases where the person who generated it with agentic tools (I'd say it's better than pure 'vibe coding') barely understands how it works. This is okay for unimportant parts of the codebase, but completely unacceptable for a critical piece of infrastructure where it really needs to be well thought out.
> This is okay for unimportant parts of the codebase
Not really. At some point the technical debt accumulates and the only option is to trash it all and start over.
The only party that profits here are the cloud token providers.
So it was possible to write ~2 million lines of (mostly) zig, but it's not possible to review ~1 million lines of rust, even though the same test suite included in those 2 million lines of zig can still be used? I'm not convinced the rewrite is a good idea and will work out, but I'm equally unconvinced by your argument.
Its possible to do that over a period of a few years. Sadly, the Rust rewrite happened in (checks notes) 8 days.
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It should go without saying that the 2 million lines of zig wasn't generated and shat out into the Bun repo as a single PR within a week.
In a week?
How much of the windows code has been written by its current maintainers? Little.
I feel this argument is not valid, especially for large code bases.
Documentation and code quality is what is important, not who wrote the code.
A project that's 2/5/10/30/100m LoC is obviously not going to be understandable entirely in someone's head. Documentation is critical. But if I'm reading your code, and I come across something confusing or you wrote something in a weird way and I want to understand, then I just... Come and ask you. "Hey, why did you do this this way? Did you consider x?" With an AI you can't do that. IMO this point is especially important if your code base is widely deployed to the point that people use it as a learning resource or a good source to learn good practices.
Isn't windows notoriously shoddy right now, so much so that Microsoft is making a big public effort to try to improve its quality?
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it's funny how the readme still says "written in Zig"
If Claude isn't even able to correct the readme, I don't know how one can have hope it produces decent results.
Maybe it should say "designed in Zig" because most of the work & thinking was done using that language. The rewrite has no such history.
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I don't use Node.js or Bun, so I'm little out of touch. But what need 1 millions lines of code as the js engine itself is a library ?
I've been wondering the same.
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> in many aspects of human history, we have traded understanding for convenience—that's the reason why we buy food at the supermarket instead of hunting for our meal.
You could always take a job on a cattle ranch or an abattoir or meat-packing plant, or watch a How It's Made documentary, and get some understanding of how the sausage gets made and put on the supermarket shelf for your convenience. This was also true as we built abstractions in computer technology: you could start off learning a high level language, then learn a lower level one, then study or build an operating system kernel, a compiler, an assembler, machine code, and then crack some books on microprocessor architecture and signal processing. You could always "go deeper" if you wanted to. And there is a payoff: understanding at a deeper level helps you get things done better at the higher levels (e.g.: understanding the concept of memory hierarchy helps you lay out data structures to make code faster).
There is no such step for slop-coded codebases: you become entirely dependent on a context-limited LLM to have a shot at even approximating some understanding. The proponents of this style will tell you, don't look at the code. It's the antithesis of every other abstraction we've built in computing.
Perhaps more productively, you treat the slop as a black box and build something understandable around it.
This is also why the notion that developers in the future will be committing LLM prompts in English to repositories instead of code written in a programming language is so foolish. I am saying this as someone who uses LLMs quite a lot to help with generating and understanding code.
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What are you talking about? How do you think food get to the supermarket? People put it there.
The entire chain from farm to table is managed and operated by humans.
Every automatization effort ever always had human oversight.
Its not the same thing as entrusting the entire codebase to overachieving markov-chain who has no concept of correctness over anything of sounding ok.
Honestly, saying the humans understanding codebase is a dead concept is the most techbro-ish I heard today.
THIS time it’s different.
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>How could the maintainers understand their codebase if most of it was not directly written by them?
Counterpoint: I look back at code I wrote a few years ago and just take it on faith that I knew what I was doing at some point. That's still better than never knowing, but it requires faith--faith in a human, vs. faith in an LLM.
Yep. These days, simplicity is a massive part of my development style. I don't want to be looking at a codebase, even my own, and thinking "shit, this guy was way smarter than me".
They support Windows, which is many millions of lines of code not written by the current maintainers.
It's a bit harder to avoid windows than it is to avoid Bun.
More importantly, it's not the same thing at all. All the code in windows (at least until recently) was written by humans, understood by humans and reviewed by humans. And that code has stood the test of time, proven its value and stability in the wild, on billions of systems. The fact that the current maintainers haven't needed to understand or replace the code is some indication of the code's quality.
Almost none of Bun's rust code has been even seen by a human, and it's only about two weeks old.
I'm somewhat willing to accept vibe-coded code if it's either absolutely non-critical, well reviewed, or maybe in the long term if it's proven itself. But not two week old code.
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> They support Windows, which is many millions of lines of code not written by the current maintainers.
All of which was battle-tested on millions, if not billions, of devices over 40 years. The new Bun is effectively a different project than it was a month ago, with next to no prod use.
I have no problem having a dependency on a 40 year/billions of use software, I do have misgivings about a dependency on a project that has never been used in prod, and was only written last week.
Windows have a incredible degree of architectural coherence and design intentionality.
It is far easier to understand some part of the various NT source code leaks than it is to understand Claude code leak
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I'm very skeptic that they read the entire codebase of Bun prior.
> I'm very skeptic that they read the entire codebase of Bun prior.
Well, they didn't really need to. A complete rewrite is effectively a different project. You may feel comfortable using a new project in prod, but most people are not.
Project A: used in production for 3 years - high trust.
Project B: Has yet to be used in production - low trust.
IDGAF about automated tests, let other users shake out the inevitable bugs that show up in prod and after a few years of stability, then we'll see.
To me, it's not about whether humans reviewed the code or not (they didn't), it's more about "here's this brand-new shiny codebase of ~1m Sloc, of which exactly zero lines has been used in prod".
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yeah this just feels like an attention stunt tbh
It's not impossible, or even that hard to review the entire rewritten codebase.
10 engineers each reviewing 5,000 LoC a day for 20 days can do it.
And that is being highly conservative with the estimate. A good chunk of the the code is probably highly trivial boilerplate one can easily skim over in minutes.
And five engineers reviewing 20 thousand LoCs would get the job done in ten days, but both numbers are just as BS when it comes to actually understanding the codebase. No one is comprehensively reading 5k lines per day for a month straight.
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20 days is rookie numbers. I can get a million engineers to each review a single line and finish code reviewing the entire code base in a minute.
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5k LoC review every day is absolutely absurd, nobody who has actually worked as a software engineer would suggest that is reasonable
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This is why I require all my software to have bespoke compilers otherwise how can I trust the devs know what their code is actually running!?
Just because we don't understand or know about compilers or able to read their output does not make them fungible.
In old days we chose between Turbo/Borland C, Quick C and GCC. We didn't think them same or trust blindly even if we didn't know how they worked.
The best developers hand optimized assembly for sub routines which they knew compilers were not good at, the rest of us sure didn't understand how any of it worked, but nonetheless felt the differences and chose with dollars and usage .
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I'm certain that the maintainers of Bun have excellent understanding of their codebase. What makes you think that they don't? They wrote the code in the first place. They know the architecture. They know what pieces do what functions.
They did not write the rust code. AI wrote that code. Your response is side stepping the primary issue people have with the rewrite: no human has read and understood all the code AI wrote.
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It’s not like they are discriminating on someone’s race or religion. If they don’t want a major vibe coded surface, do they even have to defend that? It’s part their “artistic” license as developers.
Or did we forget software inherently is opinionated
Given some posters on the GitHub issue, I get the sense some people feel their religion is being violated.
You don't even have to leave this site: when the original Bun rewrite posts were made, an incredible number of comments were focused, not on Bun, but on Jarred, who I'm assured is a complete rockstar and would never harm Bun.
Unfortunately, his followers don't realize that something like a batteries-included runtime is a huge commitment to build on top of, and governance you can trust matters as much, if not more, than the lines of code.
The way this has been handled is just baffling. A Rust rewrite is supposed to be a freebie for hype, and even an AI rewrite could have been interesting if approached more scientifically and transparently... but instead the opposite of that happened.
I don't think they have to defend it, but I don't think there's any issue questioning the validity of the approach.
If you don't like a decision don't harass, fork.
Based on the comments I think a lot of people assume the headline pertains to Bun itself.
exactly... and it's not like it's hard to fork and just raise the minimum version. It will probably be just one number somewhere (I haven't actually looked.)
if it works, it will keep working. they just don't want to support and maintain it and solve issues.
This stuff brings bad vibes.
Yes, it’s actually similar to discriminating based on race or religion, in the sense that it’s an arbitrary, meaningless criterion to discriminate on. If the Rust Bun port is better in every measurable way — passes all tests, has the same performance or better, and fixes existing bugs — then who cares what language it’s written in or how it was implemented? The point is that it’s higher quality. If you don’t trust the Bun team when they release a Rust version and give it their stamp of approval, why did you trust them when they released the Zig version two weeks ago? It makes no logical sense, and it makes the yt-dlp devs look foolish.
> If you don’t trust the Bun team when they release a Rust version and give it their stamp of approval, why did you trust them when they released the Zig version two weeks ago?
I think you cannot make this comparison because Rust version wasn’t in fact written by the Bun team. It wasn’t even read by them.
“All runtimes matter”
Yt-dlp devs made a good call. If Claude is good enough to rewrite millions of lines of Bun, it is good enough to maintain Bun fork of yt-dlp. And since Bun is part of Anthropic, they can afford it too.
people don’t care if it’s good. they only care it’s made with AI so they can signal their moral superiority. hence the derogatory term slop that is paraded around like it’s the way to win an argument
It's just more reactionary "AI bad." The tech world is rapidly splitting into people that "get" AI and people that bizarrely still resist it because they are stuck with a 2024 understanding of what AI can do (and never bothered to update their priors in earnest.)
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Oh well, I really like using Bun and I get kinda sad about the turn they are taking after the Anthropic acquisition. I really want a good Node with batteries included, but I don't want it vibe coded.
Have there been any significant issues caused by the vibecoded translation?
To be clear, I'm not implying support for the merge. I am against this whole YOLO approach to engineering. Just curious how the switch is going since I haven't seen any news since the merge announcement.
IMO the source of the new code is less important than the sheer volume of it. Bun does not need to be entirely rewritten; certainly not over a period of a week, possibly not even over a period of a year. Stability is hard-fought and battle-tested. Everyone has a plan until they get punched in the face; and every repository has passing tests until it runs production code.
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It's too early. It might be too early forever.
Epistemically: if it can be so easily vibecoded to rust, why can't it be vibecoded to be reparted? Isn't the great and Almight AI unable to parse and repair Zig? Identify it's weak points and route around it?
According to the bun team, it was already vibecoded for months before the Anthropic acquisition.
vibe coding on top of an existing battle-tested codebase is very different than merging a 1 million LoC pull request that is a week old
Probably a lie tbh
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I think it's hilarious how hopeful people were at the acquisition that Bun would be able to continue on mostly as it had been but then that all got completely thrown away and trashed.
(Hilarious in the way that's terribly sad, of course.)
It usually takes years for someone's values to be thrown out the window! How long was this one?
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How has it been trashed? Does the Bun software not work anymore?
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Why dont you want it vibe coded? Does that make it worse?
Not necessarily, but I don't trust Anthropic in making sure it doesn't become worse. They are already doing a terrible job with their own Claude Code CLI.
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Unless specific issues have been identified that were introduced by it being "vibe coded", isn't a reaction to reject it outright without actually checking the ground truth just exhibiting the behavior you are criticizing?
It's just a trust issue. Have you seen the absolute state of the Claude Code CLI development? I don't want that to suddenly happen to Bun after I've already used it for production stuff.
I don't see any hypocrisy in the comment you are criticizing. The behavior they are criticizing appears to be vibe coding. How is rejecting something for being vibe coding "exhibiting the behavior" of vibe coding?
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The ground truth is that the new maintainers can’t possibly have a good understanding of the many millions of lines of vibe-translated code. Even assuming that the code happens to work okay in its current state, the lack of understanding means a high risk that its continuing maintenance won’t result in a satisfactory level of reliability.
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You want the yt-dlp authors to review the entire post-migration Bun codebase?
And what are you referring to as "behavior"?
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No, would you use a proudly vibe-coded banking app?
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I'm not sure what "exhibiting the behavior you are criticizing" would even mean here.
BUT.
"Ignore anything but actual problems" is a terrible stance to take generally for software and dependency selection. Incidents are fairly sparse, process is much easier to observe. So if you can find connections between process and incident possibility, that's a very reasonable heuristic. And it's easy to find examples of overaggressive LLM usage introducing problems into software.
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ITS NOT VIBE CODED , JUST TRANSLATED .
Nondeterministically translated
It is vibe coded with a very good prompt.
This is about the rust conversion but that has not been released.
> Due to foreseeable compatibility and security issues
Hmm, Zig bun crashes plenty.
I wish yt-dlp linked to detail on why there are foreseeable compatibility issues. Both projects have test suites, in an ideal world they would allow fast rewrites. Maybe they want to limit inflaming the situation, but if they have spotted some specific issues it would be good to see.
I hope Bun.rs is 1.4 or even 2.0 and not a minor release, with some alpha/beta releases.
Yep, it's one thing if there was some project that saw severe regressions in Bun.rs and actually showed data about regressions.
But it's been available for a week. And so far, seems like crickets on actual data on any regressions. It's more "I just don't like this!" style grumbling.
They could at least wait a bit, test the new Bun for some weeks/months, have people read big chunks of the codebase.
It should be a major release indeed, and communicated as such, with full accountability of the migration beyond an “all tests pass”. A major tool should move slower, be tested longer, more thoroughly, since it’s used my millions.
It’s reminiscent of JavaScript world, where something is in beta for mere days (e.g. Expo’s short release cycle).
I found this:
...will install a very recent build, with version 1.4.0
I still hope there is a beta release.
Why are some people so pressed about this decision? From my point of view, if you're truly a vibe code enthusiast wouldn't you be able to just vibe code your own better yt-dlp (or fork the existing one and do whatever you need to do with it)?
Indeed. I've heard a lot of words about how trivially easy vibe coding makes building software, and how just about anyone can build something in no time at all anymore. Even stuff about how people will vibe code one-off private software for everything at all times, and such.
There really shouldn't be a reason for vibe coders to complain about any software decisions. Vibe coding a personal fork you better agree with should be a piece of cake. Isn't that part of the vibe code promise?
What's more is yt-dlp already has plugin support for 3rd party interpreters. They're just saying they don't want to deal with supporting bun themselves and the infrastructure for anyone else do use whatever they want is already there.
This is just the standard misguided entitlement people feel towards other people's projects supported by other people's time and effort. It's continually outrageous to me how people feel they can just volunteer other people's time and effort to support their own wants. The people who do the work are entitled to make their decisions and if you don't like it fork it yourself. This has been the way of this ecosystem since it started.
yt-dlp is surprisingly hackable as is.
Because for a lot of AI fans (not all, I know), it's like a religion. They aren't content to live and let live and let history show whose approach to building software is better, they insist that everyone has to agree with them. I have that situation at my job and it drives me insane that honest technical disagreement isn't allowed when it comes to AI.
I speculate that I could indeed "vibe code" a better JS build integration because what they have does not make sense at a first look.
It appears they mixed JS building into their python project, aiming to support multiple package managers which are executed from their python script.
This explains the otherwise non-sensical explanation about bun < v2 ignoring the lockfile: they use a separate lockfile for each package manager. They did not check in one for bun v1, which they claimed to support, consequently it is not using a lockfile.
That's not how JS packaging normally works. I would set up a separate folder for the JS project, and use one package manager to build the project, like anyone else does.
Publish the package to npm, or bundle the tarball with your python program.
I guess the permission model of the JS runtime could be another topic, but at least they would have their build fixed without worrying about Node dependency resolution and package managers in their Python code.
We desperately need some new terminology to describe using LLMs to support development work. "Vibe code" has a strict definition but no one really cares. I have a really hard time believing that the Rust port was 100% "vibed" the way the original definition was laid out.
It's a big slushy of emotions that I understand (both positive and negative) but it makes it so hard to actually tells what problem someone actually has when they just use "vibe coding" as a general LLM usage slur.
I'm using LLMs to assist my development and I'm measurably (in all the ways we engineers could possibly care about) doing better work faster.
Vibe coding indeed originally meant "give in to the vibes [...] and forget that the code even exists."
https://news.ycombinator.com/item?id=48239790
Studies suggest you aren't any faster and may in fact be slower. It's difficult to study such a new tech, but even optimistically, empirical evidence is only showing a ~3% gain in some domains.
Writing code is rarely the limiting factor in our work.
I think those studies have framing or methodological issue.
I agree the maintenance burden is probably being undervalued by developers in general, but there's just no way the work I do isn't faster. I just categorically couldn't have achieved the outputs I do now in the time windows I have. The software just wouldn't have existed in the world of 3 years ago and I did enough coding back then to say that with certainty.
In the past 18 months I've seen experienced developers turn out incredible work using llm-assisted tools, over and over again. With the right harnesses, processes and result-oriented testing, you can simply produce so much more high-quality work.
I know it's anecdotal, but I have so much data from my own experiences and those of my peers that I know these new tools are here to stay. It also makes me believe that those studies are either flawed or out of date.
Surely that argument is dead once someone has migrated a million lines of code in eight days.
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There's no uncertainty here. Every day I ask myself how long something I did would have taken without it. The answer is always crystal clear. It's not hard or difficult at all.
Those studies have well known flaws. I'm measuring my output so I happen to know I'm not only going faster, but the quality is better.
I'm not vibe-measuring my output ;)
studies suggest nothing. i've released a massive number of features in the last year for several projects that i estimate would have taken me multiple years to put together in a much more mentally exhausting way.
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This decision seems to based more in politics than engineering. Have you observed Bun have more segfaults, OOMs, etc, since the Rust rewrite? Have you noticed more security vulnerabilities? Have you seen more bugs? (Of course you haven't, the rewrite hasn't even landed yet.) It seems that you are making this decision because you get a bad feeling when thinking about AI involvement.
I don't select my engineering tools because they give me a bad feeling - I select them because they do the thing I want them to. If Bun starts having more bugs and feeling like worse software, I'll stop using it. But I will base that on data -- not a feeling I have. Jarred has done a lot of impressive stuff with Bun, and it seems unlikely he would ship this rewrite if it didn't meet his quality bar - I am willing to see him out here.
> Have you observed Bun have more segfaults, OOMs, etc, since the Rust rewrite? Have you noticed more security vulnerabilities? Have you seen more bugs? (Of course you haven't, the rewrite hasn't even landed yet.)
On the flip side it's not on the yt-dlp authors to test Bun's new development process and see if it results in more segfaults, OOMs, security vulnerabilities, etc. In fact it would arguably be negligent to experiment on your users if you thought there was a reasonable probability of increased security vulnerabilities.
I think there's a good argument that the responsible thing to say would be "we aren't going to immediately support running our software on a new bun release cut from main right now".
It seems a bit unfortunate to me that they've apparently already intending to never support future releases instead of planning on re-evaluating in the future. On the other hand the yt-dlp developers definitely don't owe anyone anything.
> It seems a bit unfortunate to me that they've apparently already intending to never support future releases instead of planning on re-evaluating in the future. On the other hand the yt-dlp developers definitely don't owe anyone anything.
I think your final comment gets at it. If they said "OK, I am skeptical, so we're going to pause on updating to see how this Rust thing plays out" -- that sounds like a reasonable engineering decision. Saying "because they vibe coded we are dropping support for Bun" sounds political.
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> It seems a bit unfortunate to me that they've apparently already intending to never support future releases instead of planning on re-evaluating in the future. On the other hand the yt-dlp developers definitely don't owe anyone anything.
The other side of this is that as far as I'm aware, Bun support in yt-dlp was always experimental. They mainly use Deno.
It's not really political. Or let me rephrase possibly yt-dl is being political. VUT the concept of 'not adopting a core dependency until it has been widely used in production for 6 months - a year.', is not a political on general. A full rewrite of 1 million loc is essentially a new runtime that has the same ABI as the previous and for many downstream consumers it's not something they are comfortable taking a production dependency on. If for sale of argument BUn was fully rewritten by hand would be the same situation. I personally think this kind of decision is pretty standard, I also personally think the Bun LLM rewrite will be of good quality overall, but I certainly would not bet my product/company on it. I want to be the one making the risky changes on my software not being forced into it by downstream deps.
> A full rewrite of 1 million loc is essentially a new runtime
It's not a rewrite exactly. Nobody wrote anything. Not a single human has even seen, much less understood those 1m lines.
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I think your stance is more reasonable than the one in the article, TBH. If yt-dlp said something like "We're going to wait 6 months on the Rust rewrite", that would be reasonable. But instead it says something more like we think that Bun is vibe-coded, so we don't want to use it any more. That seems less reasonable.
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Even re-written by hand isn't the same because a hand re-write proceeds slower over a longer period of time with more smaller updates that get tested somewhat along the way.
Also I don't think it's wrong to use an action as an input to judging engineering character. That could be read as judging yt-dlp or judging bun but in this case I mean it's reasonable to judge bun's developers.
IDK if i'd personally judge this action quite so badly though. It depends how they went about it and what they proffessed to get out of it.
I am very much against letting llms think and decide for you, but I don't think it's so wrong for an actual coder to employ automation.
But if they are acting like it's magic and everything will be so much better after the magic llm uses the magic safe language... yeah that definitely gets the side eye. Or no eye. Just no longer interested in or concerned with their output.
Since this is being offered as the next release version while still being new and stuffed with unsafe, looks like it's the latter. So I'm with yt-dlp in this case.
It doesn't matter if the new code happens to be ok or not, it's still a problem that they got there by hoping a black box does the right thing. A black box that that no one wrote and no one understands, not just themselves.
gcc is a black box to me, but I know that someone wrote it and understands it (or some people collectively understand all it's parts), and I know that any time I want, I can choose to understand any part of it, and satisfy myself that it is doing something both sane and deterministic.
So a developer choosing to use gcc when it's a black box to them does not reflect badly on them to me.
But no one can say that about any llm or ai. So yeah, a developer choosing to use them, depending on exactly how, may reflect badly on them.
The same was true for cheap off-shore gig coding by humans too. I have tried to use them myself in the past, hire out for small generic programming jobs using those web sites where you put up some escrow money and post a job and people bid for it, you choose one, they do it and get paid from the escrow. I only tried about 3 times for the same small job and every time I git ridiculously shit (but technically functional) results.
These were humans 15-20 years ago, no possibility of hidden ai usage like today, and it's essentially the same dynamic of just hoping some magic will get you something good for cheap, and accepting any result that appears good as good.
If someone said that that's how they made their product, I would decide that product is probably pretty crap inside and no way should I buy it or invest in it as a dependency if I have any choice.
And that's humans not ai. The problem isn't really the ai, it's the judgement to use an ai that way.
If you wait for more segfaults, OOMs and other issues, than you have failed to avoid the problem. In my opinion this direction is correct and history will show who's right.
When expressed, sounds like a trivial principle. It's surprising how rare it is to see people actually do this. Not only with tech stack: choosing cars, laptops, staying in a toxic relation, the list goes on
Notably, they aren't (yet) dropping support for older, pre-rewrite versions of Bun. They also could be leaving the door open to support Bun in the future, if the rewrite proves successful. I think waiting and seeing is the right, conservative move.
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A key element of engineering is projecting a current trajectory. Given that, it absolutely makes sense to avoid tools that give you a bad feeling. The easiest time to move away from a tool that will become a train wreck is before you've integrated it.
But what exactly are you projecting? Typically when people have said they have a bad feeling about something (imagine Next.js) it's because they are running into more bugs or they are seeing more production incidents. In this case there has been no chance to observe these things.
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> This decision seems to based more in politics than engineering.
Project governance is very important on a project; the fact that Bun's authors bent the knee to their new owner shows where their priorities lie.
> Have you observed Bun have more segfaults, OOMs, etc, since the Rust rewrite? Have you noticed more security vulnerabilities? Have you seen more bugs?
I - them - are not going to sit around waiting for bugs to start crashing everything
> I don't select my engineering tools because they give me a bad feeling - I select them because they do the thing I want them to
Good thing that you don't run an open source project then, I would remove anyone's project from my dependencies who thinks like that.
It really is amazing to me how many developers do not understand that governance is important. If I have a dependency and a maintainer of that dependency has a process I can’t trust, it’s perfectly valid to remove that dependency based on that lack of trust.
Not caring about governance is how we end up with repeated supply chain attacks.
Then Bun's rewrite is also political. They couldn't upstream their vibe coded "improvements" so in spite they decided to vibe a rewrite in Rust. The arguments for the rewrite were not backed by any data.
> They couldn't upstream their vibe coded "improvements"
What are you talking about? There is no upstream rejecting contributions here. It's the original bun developers who vibe-ported it to rust and they absolutely could and did upstream their vibe coded changes because they are the upstream.
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Every single macOS update the top comments are about giving it six months to stabilize, but when a program’s biggest ever rewrite involves a lot of AI, the top comment is calling you irrational if you don’t YOLO it, and probably a jerk, too.
I didn't say you were irrational or a jerk.
But this also isn't a fair comparison. The article doesn't say "let's wait 6 months", it says they are fully deprecating Bun. Those are two very different statements. I would have had no issue with the first.
And FWIW I think my viewpoint is the uncommon one. Look at all the responses to a previous thread about it [1] and see how many of them are negative. It's certainly a majority.
https://news.ycombinator.com/item?id=48133519
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YOLO? Bun has an extensive test suite and this implementation passed the test suite.
Can we at least try to be a bit more accurate and less hyperbolic?
I will continue to use Bun because the same people that made bun have made this decision. I trusted them one week ago. I have used bun for the past 2 years, and so have many others.
I'm not about to just assume they've become immature idiots yolo'ing stuff overnight. They're still the same people they were a week ago. Or two weeks ago.
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I don't think refactoring 1M lines of code into another language within 7 days and merging it to master is responsible. I won't make my code depend on it.
It's not refactoring. It's LLM transpiled.
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Every decision is made with imperfect information about the tool, its future, and your current/future needs. This is a normal type of engineering decision.
Bun being replaced entirely with stochastically generated code is red flag (regardless of whether it was or not). But Bun was also acquired by a huge corporation, which has been classically a huge red flag. Both of these are plenty of reason for yt-dlp not to support Bun.
In either case, this seems like a niche use case. I've used yt-dlp for years and I've never used Bun with it. If Anthropic really wants their recent acquisition to be supported in yt-dlp, it can fork it and support it itself.
FYI in case you aren't aware, the rewrite was shipped, and then had to be reverted due to issues being discovered. That's "Jarred's high quality bar" you're so confident in.
The whole point of having canary builds is that they're unstable. That's why they're called canary. Rockets failing in test flights isn't a bad thing.
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Can you link me a source that says that the rewrite shipped to a point release (not canary)? I'm not seeing this.
News to me… share a link?
Reading and understanding code is more difficult than writing code.
It is significantly easier to modify code that you personally wrote, or code that you have read and understood to fix an issue in previously. This is why the maintainers of a project change slowly over time and it takes a long time for new ones to get up to speed.
All of Bun has been rewritten by a tool. In a different language that maintainers may not be fully proficient in.
Even though the rewrite was done well, and even if we assume it's functionally equivalent to the old Zig code, there will still be future issues. And ALl of the maintainers are essentially now new hires who have never seen that code in their lives.
It's not "politics" to have an ounce of sense to foresee problems in such a project as a dependency.
“... it seems unlikely he would ship this rewrite if it didn’t meet his quality bar” is every bit as vibes-based as the decision you are critiquing.
Jared has shipped a lot of things that have impressed me. His software is measurably faster than the alternatives, and I have measured it. It runs code that Node et al can't run, and I have tried. These are normal, everyday experiences with software - based in fact, not vibes. I'm not going to argue every decision he's ever made is amazing, but his decisions have historically tracked above average.
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Not sure what seems "political" about this.
When deciding to support a given thing, you have to make a determination as to whether it's worth the effort or not.
You don't simply ignore unknowns. That effectively means assigning the unknowns zero cost, which is unlikely to turn out to be true. Generally, the more unknowns, the higher the risk, and the higher the risk, the higher the estimated cost.
There are a lot of unknowns about vibe bun right now.
One effective strategy for dealing with unknowns is to turn them into knowns if you can. Here, that probably means waiting to see how vibe bun turns out.
If it turns out to be stable and highly compatible, at some point in the future, they can always pick up support then.
> it seems unlikely he would ship this rewrite if it didn't meet his quality bar
What happened to
> don't select my engineering tools because they give me a bad feeling
Who cares if you have a good feeling about this dude? There are obvious and clear conflicts of interest at play here. If you care at all about quality, you'll wait before adopting new releases until bugs get discovered/ironed out. Don't adopt based on some dude's reputation when that reputation was built under a very different incentive environment.
> I don't select my engineering tools because they give me a bad feeling - I select them because they do the thing I want them to. If Bun starts having more bugs and feeling like worse software, I'll stop using it. But I will base that on data -- not a feeling I have.
being reactive is fine if you can tolerate issues. otherwise, you need to be proactive -- don't wait for the train to hit you before you move off the tracks
I wouldn't call it politics. I've seen enough people aim a gun at their foot and pull the trigger. They'll never thank you for stopping them, they just want to be left alone while they do it.
So, great, if this dude wants to regress through the workforce to a level of engineering maturity I associate with a high school student, I don't wish to try to be the one to stop him. Doesn't mean I'm gonna follow him. It's possible to be smart enough to just not walk into the tarpit. He's going in, I'm not.
> I don't select my engineering tools because they give me a bad feeling - I select them because they do the thing I want them to.
With that in mind, is there anything that yt-dlp uses the Bun runtime for which it can not use the other supported runtimes for? Similarly, perhaps the yt-dlp maintainers shouldn't keep supporting Bun just because it gives them a good feeling when every runtime incurs a maintenance cost.
That said, as a developer I skim over so much bullshit simply based on "bad feelings". I don't have time to evaluate every potentially useful technology in terms of whether it does what I want it to do, and no one else does either. It's clear to me that Bun is in an experimental phase of development and I think that's a good enough reason to move on if your use case is not.
Anyone who merges such a huge PR of ai generated code doesn’t deserve trust. This is a real black box now, even for the developer himself.
This is a good example of what many private companies are doing, and the rude awakening they’re in for with token price hikes and vendor lock in. It’s like Oracle all over again
You can’t really tell if you got sick from dirty hands, a week old egg, or the cheeseburger you had for lunch, but if Shake Shack had also just announced they’ve moved over to vibe-cleaning their kitchens then it’s reasonable to only eat at Five Guys from now on. Let someone else iron out the kinks.
Why wait?
Seems reasonable to preemptively drop support and let someone else either suffer the fallout, or get proven wrong and just pick up support again. It's not for a lack of people motivated by IA. Unless the motivation is more "use my IA generated content" than "actually consume IA generated content", of course.
a vibecoded rewrite right after being acquired is not political?
Is it so unthinkable to people on "hacker" news that someone might want to try a cool experiment like rewriting an entire repo into Rust?
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No one says that? Of course Bun rewrite is political. And if you deprecate Bun support due to they did something political, obviously this decision itself is political too.
Every accusation is an admission, isn't it? As always with these cases, the rhetorical contrast is staggering compared to the thread about Bun deprecating Zig.
Bun made a snap decision to merge 1M lines of unreviewed code within a week, including code generated moments before the merge. AI or not, that forces downstream users to cope with total unpredictability. This process bears no resemblance to science or engineering.
All the QA work you're demanding of yt-dlp is work Bun should've done. Trying to flip that responsibility proves your argument isn't grounded in engineering principles. And you sure made your feelings known in your comments for someone who claims not to let emotions affect technical decisions.
yt-dlp made a sane technical decision to drop a high-risk dependency. Not only is the Bun code now unpredictable, but the maintainer is too. The maintainer called the rewrite "experimental," then merged it within a week. If direct statements can flip overnight without warning or explanation, it's no wonder downstream projects want out. Especially when yt-dlp already supports alternative JS runtimes.
> This decision seems to based more in politics than engineering.
I'm glad some engineers realize that technology is inseparable from politics. It always has been. All evil came from engineers who beleived they were above politics. Selecting the tool which got the job done/made the number go up/paid a paycheck is how we got Facebook, Google, Palantir, crypto, AI, techno-fascism and neo-feudalism. None of it would've have happened without engineers blindly applying their knowledge to achieve "purely" technical results, while ignoring the social consequences. With the hindsight of the last 20 years, anyone who still advocates for an irresponsible adoption of technology should be considered automatically suspect
> I don't select my engineering tools because they give me a bad feeling - I select them because they do the thing I want them to
Among tools that meet a technical expectation—especially for (often) superfluous activities like downloading videos—I pick one that feels right and costs the right amount, and that's the one that wins. Free + works + usable is an unbeatable combination.
However, I'd argue their decision is related to a peer dependency than it is itself one about an engineering tool, which is an assessment of the risk surface and potential cost associated with doing so. I already wasn't using bun at all, but if they stopped supporting whichever runtime I do use, I can either adapt or stop using yt-dlp, which I won't because this isn't a technical thing worth wasting much time on. This mild, recent change to recently introduced peer dependency integration is largely inconsequential, and I support the call to not waste time providing extra support if it hypothetically became necessary.
You may not want to take part in politics, but politics wants to take a part in you.
>I don't select my engineering tools because they give me a bad feeling
But you do select your engineering tools on faith apparently.
> This decision seems to based more in politics than engineering.
Will you use untrustworthy dependencies in your project, which has users? I think, no.
I don't know, but I feel that this is the case with yt-dlp.
And this is absolutely engineering - care about quality and security of your software, which is used by thousands of people
> I don't select my engineering tools because they give me a bad feeling - I select them because they do the thing I want them to. If Bun starts having more bugs and feeling like worse software, I'll stop using it. But I will base that on data -- not a feeling I have. Jarred has done a lot of impressive stuff with Bun, and it seems unlikely he would ship this rewrite if it didn't meet his quality bar - I am willing to see him out here.
I have a t-shirt signed by THE Jarred himself, how much are you willing to pay for it? Comes with a month of free Claude max subscription.
What world do you live in where selecting your dependencies doesn't involve personal judgment calls?
Those judgement calls are driven by things like “oh this is too slow” or “oh this API is a mess”.
the bun team has recently demonstrated a lack of agency over their project. making massive structural changes with unclear and misleading communication. There is nothing political about seeing that as a red flag and deciding to rely on more stable projects.
I have no idea how that’s what you get from this. I don’t want my project using any tech that decides to take 6 days to rewrite the entire library with AI. That is at its core an engineering decision.
No healthy engineering team is going to do that. And I’d want to distance myself as far as I could from a project that behaves like that.
> I select them because they do the thing I want them to.
Regardless of the other aspects, this is a joke in any context I have been in since I started working in this field about 9 years ago.
Even as pure logic, you know they do what you want it to do only after you chose them. You can’t possibly be trying every option to the fullest capacity of your application.
You also converge on the “Jarred” aspect and the guy that made the decision in the title post has the opposite sentiment
I would argue the opposite. The decision to rewrite was based on politics, and the decision to deprecate support was based on actual engineering.
> I don't select my engineering tools because they give me a bad feeling.
Those bad feelings are often your years of experience trying to tell you something.
> Have you observed Bun have more segfaults, OOMs, etc, since the Rust rewrite? Have you noticed more security vulnerabilities? Have you seen more bugs? (Of course you haven't, the rewrite hasn't even landed yet.)
Your argument could go other way too. Why haven't they landed if they're so confident with the change?
> I don't select my engineering tools because they give me a bad feeling
I do, for example when I see constant behavior of lying, or negligence for security issues or not considering valid PRs and rewriting it to fit their paid plan and so on.
> I select them because they do the thing I want them to.
This is one of the dimensions when I pick the tools, I know Oracle produces nice products, but I don't want to get sued if I do something accidentally their lawyers dislike.
So, let's see here. Here we have a program, that is used to install scripts from source that has been targeted, and breached multiple times last few months, can run arbitrary code on millions or billions of user computer, servers. And, it was ported to another programming language, resulting in 1m LOC, in 7 days for publicity stunt of a LLM company
Even multiple people can not go through 1m lines of code for any kind of vulnerability in 7 days, let alone 'observe' more segfaults, OOMS, unsafe behavior, on who knows how many possible ways things can go wrong in this new condition.
Only guaranty is 99% tests passed, and the engineer who is paid by the same LLM company.
How in the world, any sane engineer would agree, this would be remotely a good idea to continue using this tool, for a chance that such a expensive change won't actually land in production?
The first sentence on the linked page is literally: "Due to foreseeable compatibility and security issues"
Everything is politics, sorry to say. Even software engineering try as we might.
> feeling like worse software
Politics ;)
As far as I'm concerned Bun has been extremely irresponsible with this entire rewrite, and it calls into question their entire development philosophy. Any project that cares about stability and reliability should steer clear of Bun for a while.
> I will base that on data -- not a feeling I have.
and yet...
> If Bun starts having more bugs and feeling like worse software, I'll stop using it.
Is it not possible to judge that certain approach is more likely to bring unforseen controlable problems than another by analyzing how it works without assessing it's output? No "feeling" is needed
Yeah this is a cringe way to weigh in on something completely unrelated to your project. Who cares if some random package supports Bun? Compat was always on Bun, anyway.
it’s a way to win supporters and make noise. everyone is taking sides
It is entirely rational to not use a completely new library no one yet confirmed is good. And complete agentic rewrite makes it completely new thing.
The argument that you somehow cant unless you go through trouble of testing it is way more "politics" and way less "engineering".
I believe you contradicted your first point by following it with "If Bun starts having more bugs and feeling like worse software"
...so you do use feelings in your calculation? To be clear, I have no problem with that and think there is some level of speculation you need to do when deciding what to rely on.
As a hypothetical, pretend that Bun added obfuscated binary blobs that get executed at build time. Well, your code still works and no effects show up at runtime. Are you going to keep using it or dump it based on the "feeling" that something isn't right?
Bug counts are numbers. Memory usage and performance are numbers. Eventually those numbers get so bad that you leave.
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The rust rewrite isn’t even out of canary IIUC.
A merge to main itself is pretty substantial, especially a week after saying, "[This] code that does not work. We haven’t committed to rewriting. There’s a very high chance all this code gets thrown out completely."
Isn't that what Bun/Anthropic did? A rewrite based on vibes?
Except "because we can" and the expectation that some kind of bug will be reduced and other metrics will not get worse
All Bun devs are happy to change programming language?
When their competition is already in rust and more mature
While using the LLM that is now paying their salaries. Kind of a conflict of interest
Even a major version upgrade is enough for me not to touch it for 6 months, let alone a full rewrite
Has Bun posted any analysis and shown the data?
> Has Bun posted any analysis and shown the data?
Jarred promised a blog post just like he promised to not merge the slop branch.
absolutely, and `its development seems to have taken a turn towards being fully vibe-coded` ungrounded claim confirms the hysteria, I'm afraid
The whole code base is a vibe coded rewrite, half a year after Bun was acquired by Anthropic.
I see lots of ground for that claim.
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What are you afraid of?
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> This decision seems to based more in politics than engineering.
You are 100% right. This is a decision made on VIBES and not evidence. The proof is here:
> Bun was recently rewritten in Rust using Claude, and its development seems to have taken a turn towards being fully vibe-coded. This is alarming and disappointing for a number of reasons, and frankly it seems like a future headache that we'd prefer to avoid.
They haven't tested it, they haven't found a single problem. They just don't like AI code and they're clearly saying "the fact that the project tested every line of code and it passes all tests doesn't matter to us. The fact that it's vide coded by people who literally make coding LLMs also doesn't matter."
Pure ego, no data.
> They haven't tested it, they haven't found a single problem. They just don't like AI code and they're clearly saying "the fact that the project tested every line of code and it passes all tests doesn't matter to us. The fact that it's vide coded by people who literally make coding LLMs also doesn't matter." Pure ego, no data.
So an OSS project now owes testing to hyperscalers? Lol!
So a vibed decision to reject vibed code. Minus minus equals plus?
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[dead]
So many people in the comments here are making assertions about the quality of the rust re-write but the point largely remains the same. There is no way you've read all million LOC in the time and reviewed to make sure it really is transpiled. It's not a criticism of the method, but the time and review process.
To be honest, I share primeagen's view that LLMs handle translating code from one language to another quite well. As far as I know, they converted the languages file by file. This is what led to such a high volume of `unsafe` code. Although, in any case let's be honest, this is causing, and will continue to cause, various issues. I find it easier to live with this point of view.
He's a content creator on youtube, a celebrity, not a serious programmer.
He was a software engineer at Netflix before turning to content creation. It is also clear watching his videos that he knows his thing. As an experienced programmer myself, I find his commentary to be way too relatable to be just bluff.
He may not be Don Knuth, Linus Torvalds, John Carmack or Fabrice Bellard. But he is definitely a serious programmer. That he livestreams doesn't make him less of a programmer.
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Who cares what you think of someone else’s qualifications?
It’s just someone quoting someone to help ground their position.
What if it was a journalist writing about a security vulnerability then a programmer quoting them, would that count then?
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Its Safe by Zig standard.
> This is what led to such a high volume of `unsafe` code
Which defeats the purpose of having it in rust.
That is incorrect.
Identifying where code is unsafe, is a qualitative improvement. Not guaranteed to be complete, but more complete than a language that does not focus on that concern. Moving forward, the benefits of Rust compound. The concern about AI is orthogonal to the concern about moving to Rust.
Now there are 2 versions[1] that can be instrumented, regardless of the misgivings about AI.
[1] Bun v1.3.14, released on May 13, 2026 (commit 0d9b296af) and current.
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I see Bun’s Rust rewrite (esp the style how it was done) as a form of massive internet trolling for PR reasons. By making a bigger fuss about it, we’re feeding the troll
They are. Just wait until Jarred releases his blogpost and Anthropic marketing machine kicks in.
He promised the blog post just like he (almost) promised to not merge the slop branch
Say what you will about Rust vs Zig as languages, the Zig toolchain is definitely the easier of the two to integrate into another project.
This doesn't really have anything to do with the merits of the languages themselves, but rather with the rewrite being entirely vibe coded. If it had been from Rust to Zig instead of from Zig to Rust, I expect the exact same response would have happened.
Mostly unfounded in my opinion. They took the _exact_ same strategy that go did when they moved from C Go to a Go based compiler.
First they essentially wrote a translator that preserved the C idioms (so it wasn't idiomatic go) until they had byte for byte output.
Then they started changing code one by one to be more Go-based.
Bun is doing the same. Right now it is mostly a one for one translation of the zig code. Over time they'll make it more idiomatic Rust.
I think this is fine with the caveat that if it does turn out the rust rewrite works just as well as before they should start supporting it again.
I don't know how to feel about the Bun rewrite.
On one hand, it seems very scary to me, having most of your codebase unreviewed.
On the other hand, it passes their tests with few regressions from what I heard.
Maybe it's just because I don't have enough experience there, but I wouldn't trust my tests to this degree and completely rely on them without reading the code.
congratulations, in a sea of politics and ideology you have a sensible take. i think a wait and see approach is reasonable here
bun was never the recommended js runtime when they first announced its need for yt support [1]. in fact they recommended deno over all, even regular node.
depending on the environment of choice, these runtimes are only used to bypass certain blockers. it is not that deep.
[1] https://news.ycombinator.com/item?id=45898407
Bun is pretty much doomed. No one except anthropic will use it.
They foresee potential issues in the future, so they deprecate now? I mean, whatever lol do as you like, but that's an odd choice.
Your bank has vibe coded their entire codebase into rust in a week.
The test suites passed so it's all good.
Can't be worse than COBOL
There is an implicit assumption that the other supported runtimes aren't being vibe-coded. Looking at commit metadata tells a different story.
The "to vibe code or not to vibe code" holy war is now in full swing.
war implies "not vibe code" could win. that's impossible
There's literally nothing that LLMs can build that humans cannot. The only factor influencing people to use AI is time. They trade off a small amount of quality for a large amount of time savings. The tortoise and the hare parable comes to mind.
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What does this use bun for? I thought this was a python project?
They need a JavaScript runtime to execute some challenges that certain pages present (like YouTube)
They used to have their own "youtube script interpreter" that was kind of fascinating. But yeah as you said they switched to proper js runtimes recently.
What they don't need is hardcoding support for five JS package managers in their python files.
In the post the maintainer says that an older version of bun "results in the ejs lockfile being ignored".
The reason is that they never committed the necessary lockfile despite listing "support" for that bun version.
They have separate lockfiles for other package manager versions: bun.lock, deno.lock, package-lock.json, pnpm-lock.yaml.
This part of the comment is also interesting: "which is a significant security concern for users when considering all of the recent npm supply chain attacks".
If you would set up a proper build for the JS artifact instead of committing four lockfiles to your repository, users would not be as exposed to npm supply chain attacks.
Most people who use/used bun have never read bun's code. Then why does it matter who/what wrote the code?
And to be honest bun's zig codebase (especially in the early days) was neither "clean" nor "idiomatic" but the tool worked and people used it.
> Then why does it matter who/what wrote the code?
You trust for someones expertice.
like the one of Jarred-Sumner, whos responsible for the rewrite?
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Being conservative with technology choices and only using Node LTS has paid dividends lol
Has bun really shipped using a million line vibecoded PR. I know they merged it, but merging something in a new dir doesn’t mean anything compared to what code is actually running for customers. It’s crazy if the vibecoded rust version is what’s running for customers and not just some experimental hack.
Except it's not vibecoded, it's litteraly the best prompt an LLM can ever get - literal code. If the whole thing ends up as a failure, then it will show that the king is naked.
Maintaining compatibility with multiple runtimes adds too much friction for a core tool like yt-dlp. Dropping Bun seems like the right call to keep development focused.
I think this HN submission provides little value and a lot more headache to the maintainers of FOSS project (you can already see a lot of brigading in the GitHub comments). IMHO HN shouldn’t allow submissions like this.
This title is wrong. It makes it sounds like Anthropic dropped support for and deprecated Bun.
I can’t help but read the logic as not being too far off from: “libfoo switched to being developed using emacs instead of vim so we can’t trust it anymore”
It’s not the same obviously, but here’s why I can’t help but view it analogously:
The only truth in software is whether it works or not for whatever your use case is. Even before AI, we couldn’t have known if the author of a piece of software was proceeding with rigor or just trying random stuff until it seemed to work.
In other words, we didn’t judge someone’s software by inspecting their methodology or what tools they used. Heck, we often ended up using software that had no test suite or where the test suite was junk! And so many of us who are fans of memory safety use tools written in C, and vice versa (I’m no Rust fan but I use plenty of tools written in Rust).
So yeah, the logic that goes, “I won’t use your stuff because I don’t approve of your use of AI” is about as believable to me as if you stopped using something because you didn’t like the authors choice of editor
I don't know how to tell you this, but people actually can and do, in fact, worry about the methods things come to be made with, and make decisions based on if they approve of that process or not. Otherwise the idea of free trade chocolate/coffee/other shit would not exist.
>I can’t help but read the logic as not being too far off from: “libfoo switched to being developed using emacs instead of vim so we can’t trust it anymore”
That's wild. You should read it as being nowhere in the same ballpark nor adjacent ballparks as that.
Yea for real. Like how is it possible to even formulate that as anywhere near the subject matter in any way, shape or form :S
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> I can’t help but read the logic as not being too far off from: “libfoo switched to being developed using emacs instead of vim so we can’t trust it anymore”
So let's say they up the ante and set up a cron job to rewrite the entire codebase in a new language on the first Monday of every month: from Rust to C++ to Go to Swift and back again.
For customers using the product, that's basically the same as a maintainer switching editors? Irrelevant detail?
Most people probably think the text editor used would have no meaningful effect on the code written.
I don't think many would say the same for LLMs.
Maybe vibe bun is just as good or better than old bun, but how would we know at this point?
> ...we couldn’t have known if the author of a piece of software was proceeding with rigor...we didn’t judge someone’s software by inspecting their methodology...
That's not true. First, some people do directly check whether a project has a level of rigor they are comfortable with before adopting it (or when deciding whether to continue using it). I personally do it, where it matters. Many more use reputation signals, which, while certainly not perfect, correlate, may be good enough, and are a lot easier than direct, manual reviews.
> Maybe vibe bun is just as good or better than old bun, but how would we know at this point?
By considering objective facts like efficiency, performance, error rates, security vulns etc. like we always do?
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there could be recommended runtimes, but shouldn’t the runtime be user-configurable anyway?
There is no generic “JavaScript runtime” interface that runtimes would implement, therefore support must be tailored to the specific interfaces of existing runtimes.
At one point we had UMD[0], which effectively provided runtime-agnostic interface, but ES modules were incompatible with that.
Deno and Bun have decent Node compatibility, so couldn't Node APIs be used as the generic runtime interface?
[0]: https://github.com/umdjs/umd
There is another by Meta for react native. Forgot the name.
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Google did something similar with golang. Of course it was a tool based rewrite and they did lots of tests but some bugs still emerged. People should stop being mad about a company that delivers a tool that is about shipping software faster. The world does not resolve around high quality software, the world resolves around things that might need a reboot every other day, that was never touched for over 2 years. Things that somebody did once and it worked but most people do not understand it because of the aweful code. Yes of course we still need high quality code in some parts, but most parts of the world is already running on software that is way worse than modern vibe coded things
Do not vote on this comment! I am a server! :)
tl;dr: give up, stop trying. just approve the juniors' PR without comment so you have more time to proompt.
This is such a knee jerk reaction.
Lol! Fuck around and find out. There were dozens, “well, if you don’t like it – don’t use it”, “they don’t owe you anything”, “it’s their project”, etc., etc. Nice to see the consequences.
And now those people are berating yt-dlp maintainers. Turns out their real demand was blind loyalty, not acceptance of any fair principle.
Why even use bun or anything else if everything is getting slapped together with LLMs? May as well use them to build native
Someone should fork yt-dlp and rewrite it in Rust...and have it use bun exclusively
zig is barely adopted relative to rust. totally reasonable to move to Rust, which isn't as risky of a bet. and you're not the guy having to find their zig memory leaks.
Can anyone explain why bun was used to begin with?
Processing the YouTube-scripts to get to the video addresses. It was never the default option for that purpose, which is deno.
but isn't this just javascript?? Where is the standard interpreter?
Or better yet, can someone explain why they build JS from python scripts with manual support for each package manager and a lockfile for each?
Obviously the JS build should happen outside of Python and use one package manager instead of attempting to support them all.
Who was actually using yt-dlp with bun? The primary use is to solve JavaScript challenges sent by YouTube, which uses Deno by default.
To be fair, I'm not quite sure why it would prefer either Deno or Bun when it's far more likely that a user has Node on their system.
https://github.com/yt-dlp/yt-dlp/wiki/EJS
Read the "Notes" sections for details.
This makes a lot of sense.
I don't use Bun, but we (and many others) depend heavily on numpy. It's been around for decades and heavily battle tested. If someone came out with a new version of numpy vibe-code rewritten in a week, with assurances that "all tests pass", do you think we would adopt it? Absolutely not. We would have no confidence that there aren't some latent bugs or that we can fully trust the results.
It has nothing to do with AI having rewritten it, it has to do with being battle tested over time. If a team of humans had rewritten it in a week, I wouldn't trust or use it either. Maybe after a year of it being widely adopted. Not before.
I assume they need to do a bunch of WebAPI bullshit to get around Youtube's draconian policies, but maybe one day https://txikijs.org/ will solve all problems with embedding javascript. I believe, and maybe the strength of my belief will be enough.
Bun was just one of multiple JS runtimes supported, so dropping them doesn't have user-facing consequences. The people posting militant comments here and harassing the maintainer on GitHub are fighting for Anthropic instead of trying to raise any legitimate concerns about yt-dlp.
Do we know which model was used for the rewrite?
Claude
Bun’s source code rewrite from Zig to Rust was executed primarily through AI-assisted development using Anthropic’s Claude agents, specifically within a branch named claude/phase-a-port. The project creator, Jarred Sumner, merged the massive pull request (PR #30412) on May 14, 2026, which involved over 1 million lines of code added and 6,755 commits completed in roughly one week.
Claude is a model provider: they have many models. It would be interesting to learn if the models used were Sonnet, Opus, Mythos, some other internal unreleased model, or some mixture of them.
Gemini, obviously.
Do you also install pre-alpha revisions of operating systems on your main work pc? No, you do not. Why? Because of the "foreseeable compatibility and security issues".
"Well, why don't you install and only then resolve issues if you have those difficulties?" most comments here are asking, in effect
Cause you're sane, that's why!
Same here. yt-dlp does not owe it to anyone to beta test things. Maybe this bun rewrite will be the best thing since sex, and maybe it won't be. Not wanting to alpha test someone else's shit is sane. And the bugs (if any) would go to yt-dlp, forcing them to debug someone else's alpha software. This is a sane response.
I don't think it matters how code is produced -- it matters what it achieves. Is there evidence that there is something wrong with recent Bun releases?
I think one of the big disconnects here are the competing views about "what it achieves" means on a fundamental level.
There's the "what it achieves" today; software x works as intended as of right now.
And then there's "what it achieves" long term.
Those with significant experience with sprawling, LLM-generated, codebases, often built by those who don't understand the code produced, can attest to things being good today, unworkable tomorrow.
While this isn't true across the board, and my own experience should be considered anecdotal at best, those who consider "what it achieves" to also include long term viability as a success metric, are skeptical of these types of changes.
Personally, success for dependencies isn't just "does it work today" but "can I trust it to work long term."
I don't use Bun. I don't care about Bun. But my opinion is that how code is produced will have some effect on what it achieves, if the goalpost includes more than "it works today."
Bun alert!
Good news!
I already came across some bs bug in claude today due to this stupid rust bun thing, so I absolutely 100% support this decision.
As long as Deno support is still there I'm not sure why you need anything else. It's not vibe coded slop for one.
Well, apparently Deno is also a slop now: https://github.com/yt-dlp/yt-dlp/issues/16766#issuecomment-4...
Deno's LLM contributions have been smaller in scope, so they're more likely to be reviewed by a human, and the codebase remains understood by its contributors. Can the same be said of Bun, which switched to an entirely different language in a single, million-line PR?[0]
[0]: https://github.com/oven-sh/bun/pull/30412
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Using AI to write code is not necessarily vibecoding nor slop.
I see a lot of commentators in this thread who are aggressively critical of volunteer maintainers for making a decision about how to maximize the value of the free labor they donate to the world.
And yet none have offered to volunteer their time to maintain a downstream fork or otherwise rectify the perceived problem.
Strange.
Which "volunteers" are you referring to? Bun? yt-dlp?
yt-dlp, clearly. Bun has no volunteers (as of the rust rewrite at least, it's all highly paid SWEs and GPUs.)
Most developers can’t see AI slop because their level of competence is actually below what an AI can produce.
Technical debt was a reality before vibe coding. Someone was writing all that trash by hand.
I got banned from yt-dlp for stating that Deno is vibe coded and that AIs are responsible for 54% commits since Feb 01. Also see https://news.ycombinator.com/item?id=45034496
I like this clear divide of:
Zig bad, rust good
You bad, ai good
and then some random posts in between that try to create some hot takes for upvotes. What is the internet at this point?
yt-dlp launches propietary software:
https://jxself.org/shifting-the-trap.shtml
You can run a BF and, soon, subleq.
Ah yes, more examples of averse behavioral ai syndrome
Reason #2 is purely speculative. It’s disappointing to see technical decisions being made on such grounds.
All dependency management is speculative. You've got to hedge your bets that the dependency is reliable and fit for purpose. It is reasonable to view Bun's recent choices as increasing the risk associated with depending on it.
Very much agree. Until the vibe-coded version has been fully audited and profiled to perform, within reasonable tolerances, as well as the original code base, it feels like a bad idea to support it downstream or use it in production.
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Really?? So you base your engineer in "speculation". The Bun team has a deep track record of delivering a high quality product. What makes you think that is going to stop?
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> All dependency management is speculative.
What a nonsense generalization.
In this case, the speculation ostensibly is that in future, there will be a release version of Bun that has is buggier or otherwise lower quality than the current stable version.
There's literally no basis for believing that. The actual basis is "I don't like how they're approaching the development of their next version."
If that's a valid basis for "dependency management", then using a Ouija board would be just as valid.
It's a common fallacy among tech folks to believe that every decision can be made from 100% deterministic grounds ("X decision will result in Y percent change"). In reality, successful decision-making often involves speculation. The speculation in question is within the bounds of reason. You may disagree, but the fact that it is speculative isn't the problem.
And not acting while doing the whole analysis to reach close to 100% deterministic grounds mis a decision in itself! It’s perfectly reasonable to drop support for bun, and potentially revisit later on when more details come up
> The speculation in question is within the bounds of reason. Y
I disagree. It seems to be an emotional reaction borne of ignorance and uncharitable assumptions. There's no "reason" involved.
What part of the recent history of vibe coded projects has not resulted in low quality, bug laden code? Dismissing this a "purely speculative" is just like dismissing the weather report as "purely speculative" when deciding what to wear in the morning.
Low quality, bug laden code has existed long before LLMs and it'll continue to exist long after. Their rationale about avoiding future headaches could literally apply to any open source project they have a dependency on.
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There is quite the selection bias going on here... you aren't hearing about the successful projects.
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Doesn’t bun have a massive test suite that the rewrite passes? What else do people want?
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Vibe coding from scratch is far from translating an existing app to another language.
I don't know any bad stories about ai-translated apps. Partially because it's a relatively new trend, but also because a big amount of usual vibe code fail modes are not applicable here.
It's a reasonable decision to not take a dependency which doesn't meet your own engineering standards. People in the JS community could learn something from that.
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When Patty?
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Idiotic. Why do they care what language it's written in? If it works it works.
Wow, bun support was just added in November last year (I think). That's a lot of work to throw away, but you can't argue with their reasoning.
bun is still supported for specific versions so nothing is being thrown away. in any case the actual code is the same, since it's all javascript. it's more a matter of the wrapper code that calls the different runtimes and maybe some edgecases where the runtimes are not 100% compatible.
Honestly I hope agentic AI ushers in a new age of minimal-SBOM software. I myself am moving all of my projects towards nearly 100% vanilla where possible. For example, golang. Why use [insert web framework] when you can just use vanilla for 99% of web apps?
There's something really satisfying about a go binary with minimal dependencies running in a busybox docker container.
Rather than have complexity centralised and managed, let's generate the same vulnerable code across millions of apps. Great plan.
"A little copying is better than a little dependency." - Go Proverbs [1]
Most complexity is unnecessary. Adding dependencies to your project exponentially increases your project's surface area, which in turn increases its regulatory/cybersecurity burden, especially if your software is a medical device, munition, etc. Why is Echo/Gin/Gorilla/etc better/more secure than vanilla Go's mux? Just anecdotal, but we use the Echo web framework for Go and it's caused nothing but headaches. It does magical XML parsing by default even though we don't deal with XML which gets us flagged in pen tests. Updating from v4 to v5 broke production for us because they made an undocumented server config change that makes all requests have a 30 second timeout. Meanwhile vanilla go has the ability to register routes and middlewares, so what value is Echo bringing to the table? Ditto for lots of other unnecessary dependencies. A lot of times we just need one little thing out of the whole package, and in those cases a little copying (or a little AI generation) is better than a little dependency.
A static go binary with minimal dependencies running in a busybox container has a tiny CVE footprint when run through grype/snyk, etc. Do the same for a NodeJS app with zillions of dependencies running in an ubuntu container and you'll spend all day triaging CVEs.
I'm not saying "roll your own crypto" but I am saying "axios-like packages don't make sense to use any more in a world where AI+vanilla accomplishes the same thing"
[1] https://go-proverbs.github.io/
Wouldn't that be worse? With dependencies, it's at least possible that someone else has audited the code, but with a vibe-coded from scratch app, it's definitely totally unreviewed.
I never said AI code should be "unreviewed". I'm saying that instead of pulling in axios or requests (as a contrived example) to make HTTP requests, just use AI to generate some vanilla JS/Python that has the exact subset of functionality you need. Your code has fewer dependencies, CVE surface area, etc, wins all around.
You only add what you need instead of importing some bloated dependency. That means you can actually review the code yourself.
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> There's something really satisfying about a go binary with minimal dependencies running in a busybox docker container.
Go binaries are immensely satisfying, but I don't follow your logic here. The vast vast majority of dependencies in Go do not depend on the outside world, so the binary would remain self-contained whether it has 1 or 100 dependencies, no?
Assuming you disable CGO, yes, the binary is always self-contained. However, I want to clarify a few things.
The "self contained" part is only important in that it lets you use busybox or "from scratch" as your container runtime environment which has a very tiny cybersecurity surface area compared to, say, ubuntu or even alpine which has a bunch of system libraries your go binary isn't using, but which could still get flagged for having vulnerabilities.
Minimizing dependencies of the go binary is a separate, but equally important task that reduces the cybersecurity surface area of your go binary itself to just "the go standard library" instead of "go stdlib + a dozen github packages"
Whenever I am working with a NodeJS project I pity the fool who has to do SCA because the CVE surface area is enormous compared to go, which has a fairly batteries-included stdlib
That must be why so many vibe-coded UIs have awful UX (terrible contrast, too small fonts, everything gets its own colors, no attempts at standardized behaviour)
Frameworks and ORMs were the pre-agentic AI "iron man suit".
I'm quite liking how good Claude Code Opus is at Rust + sqlx (raw SQL with type safety) + actix-web.
This like if BitTorrent cut off Windows support over objections to Microsoft embrace/extend/extinguish. It’s a slightly incoherent position.
This seems like a tenuous analogy, to put it lightly.
Care to explain why, or nah?
Not BitTorrent, but I can see a world where e.g. Transmission dropping Windows support because of Microsoft policies.
To me it feels more like the old "this site only supports IE6". Instead of checking which JS engine the user has, check for specific api support and fail gracefully.
Which company doesn't do that?