A lot of people seem confused about this acquisition because they think of Bun as a node.js compatible bundler / runtime and just compare it to Deno / npm. But I think its a really smart move if you think of where Bun has been pushing into lately which is a kind of cloud-native self contained runtime (S3 API, SQL, streaming, etc). For an agent like Claude Code this trajectory is really interesting as you are creating a runtime where your agent can work inside of cloud services as fluently as it currently does with a local filesystem. Claude will be able to leverage these capabilities to extend its reach across the cloud and add more value in enterprise use cases
They discussed how running generated code is better for context management in many cases. The AI can generate code to retrieve, process, and filter the data it needs rather than doing it in-context, thus reducing context needs. Furthermore, if you can run the code right next to the server where the data is, it's all that much faster.
I see Bun like a Skynet: if it can run anywhere, the AI can run anywhere.
Yea - if you want a paranoidly-sandboxed, instant-start, high-concurrency environment, not just on beefy servers but on resource-constrained/client devices as well, you need experts in V8 integration shenanigans.
Cloudflare Workers had Kenton Varda, who had been looking at lightweight serverless architecture at Sandstorm years ago. Anthropic needs this too, for all the reasons above. Makes all the sense in the world.
> Yea - if you want a paranoidly-sandboxed, instant-start, high-concurrency environment, not just on beefy servers but on resource-constrained/client devices as well, you need experts in V8 integration shenanigans.
To be honest, that sounds more like a pitch for deno than for bun, especially the “paranoidly sandboxed” part.
JS has the fastest, most robust and widely deployed sandboxing engines (V8, followed closely by JavaScriptCore which is what Bun uses). It also has TypeScript which pairs well with agentic coding loops, and compiles to the aforementioned JavaScript which can run pretty much anywhere.
TS is enormous, has endless training data, and can interact with virtually anything on the Internet these days.
Also, strong typing is very very useful for AI coding context.
The answer is typescript is a much simpler and more pleasant developer experience than any other language. These are products they need to, and often originate from, fast churn of code/features.
Otherwise they’d be building these types of things in Rust.
I'm not confused about the acquisition but about the investment. What were the investors thinking? This is an open source development tool with (to date), 0$ of revenue and not even the beginnings of a plan for getting such a thing.
The acquisition makes more sense. A few observations:
- no acquisition amount was announced. That indicates some kind of share swap where the investors change shares for one company into another. Presumably the founder now has some shares in Anthropic and a nice salary and vesting structure that will keep him on board for a while.
- The main investor was Kleiner Perkins. They are also an investor in Anthropic. 100M in the last round, apparently.
Everything else is a loosely buzzword compatible thingy for Anthropic's AI coding thingy and some fresh talent for their team. All good. But it's beside the point. This was an investor bailout. They put in quite a bit of money in Bun with exactly 0 remaining chance of that turning into the next unicorn. Whatever flaky plan there once might have been for revenue that caused them to invest, clearly wasn't happening. So, they liquidated their investment through an acquihire via one of their other investments.
Kind of shocking how easy it was to raise that kind of money with essentially no plan whatsoever for revenue. Where I live (Berlin), you get laughed away by investors (in a quite smug way typically) unless you have a solid plan for making them money. This wouldn't survive initial contact with due diligence. Apparently money still grows on trees in Silicon Valley.
I like Bun and have used it but from where I'm sitting there was no unicorn lurking there, ever.
They don't need Bun to make revenue, but they need Bun to continue existing and growing for their products to make revenue. Now they can ensure its survival, push for growth, and provide resources so that Bun can build the best product rather than focus on making money.
Could also be a way to expand the customer for Claude Code from coding assistant to vibe coding, a la Replit creating a hosted app. CC working more closely with Bun could make all that happen much faster:
> Our default answer was always some version of "we'll eventually build a cloud hosting product.", vertically integrated with Bun’s runtime & bundler.
The writeup makes it sound like an acquihire, especially the "what changes" part.
ChatGPT is feeling the pressure of Gemini [0]. So it's a bit strange for Anthropic to be focusing hard on its javascript game. Perhaps they see that as part of their advantage right now.
>Claude will be able to leverage these capabilities to extend its reach across the cloud and add more value in enterprise use cases
100%. even more robust if paired with an overlay network which provides identity based s3 access (rather than ip address/network based). else server may not have access to s3/cloud resource, at least for many enterprises with s3 behind vpn/direct connect.
ditto for cases when want agent/client side to hit s3 directly, bypassing the server, and agent/client may not have permitted IP in FW ACL, or be on vpn/wan.
Java was doing "cloud-native, stripped down (jlink) image, self-contained runtime with batteries included" long before Bun existed. There's also GraalVM for one executable binary if one's ambitious.
if I would guess Anthropic is (rightly) frustrated with the state of the js ecosystem and is taking the best attempt so far to make the js experience much more streamlined for their developers. Convention over configuration might finally be coming to the js ecosystem?
That's a really cool use case and seems super helpful. working cloud native is a chore sometimes. having to fiddle with internal apis, acl/permissions issues.
They want to make sure the runtime they depend on continues to be maintained. It's still niche and new, so its continued existence isn't as sure as something like Go.
This matches some previous comments around LLMs driving adoption of programming languages or frameworks. If you ask Claude to write a web app, why not have it use your own framework, that it was trained on, by default?
Currently Claude etc. can interact with services (including AWS) via MCPs.
What the user you're replying to is saying the Bun acquisition looks silly as a dev tool for Node. However if you look at their binding work for services like s3[0], the LLM will be able to interact directly with cloud services directly (lower latency, tighter integration, simplified deployment).
As a commandline end user who prefers to retreive data from the www as text-only, I see deno and bun as potential replacements (for me, not necessarily for anyone else) for the so-called "modern" browser in those rare cases where I need to interpret Javascript^1
At present the browser monstrosity is used to (automatically, indiscriminantly) download into memory and run Javascripts from around the web. At least with a commandline web-capable JS runtime monstrosity the user could in theory exercise more control over what scripts are downloaded and if and when to run them. Perhaps more user control over permissions to access system resources as well (cf. corporate control)
1. One can already see an approach something like this being used in the case of
> At the time of writing, Bun's monthly downloads grew 25% last month (October, 2025), passing 7.2 million monthly downloads. We had over 4 years of runway to figure out monetization. We didn't have to join Anthropic.
I believe this completely. They didn't have to join, which means they got a solid valuation.
> Instead of putting our users & community through "Bun, the VC-backed startups tries to figure out monetization" – thanks to Anthropic, we can skip that chapter entirely and focus on building the best JavaScript tooling.
I believe this a bit less. It'll be nice to not have some weird monetization shoved into bun, but their focus will likely shift a bit.
> They didn't have to join, which means they got a solid valuation.
Did they? I see a $7MM seed round in 2022. Now to be clear that's a great seed round and it looks like they had plenty of traction. But it's unclear to me how they were going to monetize enough to justify their $7MM investment. If they continued with the consultancy model, they would need to pay back investors from contracts they negotiate with other companies, but this is a fraught way to get early cashflow going.
Though if I'm not mistaken, Confluent did the same thing?
> They didn't have to join, which means they got a solid valuation.
This isn't really true. It's more about who wanted them to join. Maybe it was Anthropic who really wanted to take over Bun/hire Jarred, or it was Jarred who got sick of Bun and wanted to work on AI.
I don't really know any details about this acquisition, and I assume it's the former, but acquihires are also done for other reasons than "it was the only way".
Given the worries about LLM focused companies reaching profitability I have concerns that Bun's runway will be hijacked... I'd hate for them to go down with the ship when the bubble pops.
At least Anthropic itself has the stated goal of creating ethical AI that benefits humanity. That’s more than can be said for any other AI companies. Time will tell though. Google‘s motto used to be “don’t be evil” and now it’s basically the opposite.
Yeah, now they are part of Anthropic, who haven't figured out monetization themselves. Shikes!
I'm a user of Bun and an Anthropic customer. Claude Code is great and it's definitely where their models shine. Outside of that Anthropic sucks,their apps and web are complete crap, borderline unusable and the models are just meh. I get it, CC's head got probably a powerplay here given his department is towing the company and his secret sauce, according to marketing from Oven, was Bun. In fact VSCode's claude backend is distributed in bun-compiled binary exe, and the guy is featured on the front page of the Bun website since at least a week or so. So they bought the kid the toy he asked for.
Anthropic needs urgently, instead, to acquire a good team behind a good chatbot and make something minimally decent. Then make their models work for everything else as well as they do with code.
> Yeah, now they are part of Anthropic, who haven't figured out monetization themselves.
Anthropic are on track to reach $9BN in annualised revenue by the end of the year, and the six-month-old Claude Code already accounts for $1BN of that.
How is their Web app any different than any other AI? I feel like it’s on par with all of them. It works great for me. Although I mostly use Claude code.
I am more shocked about the origin story compared to the acquisition.
> Almost five years ago, I was building a Minecraft-y voxel game in the browser. The codebase got kind of large, and the iteration cycle time took 45 seconds to test if changes worked. Most of that time was spent waiting for the Next.js dev server to hot reload.
Why in the hell would anyone be using Next.js to make a 3D game... Jarred has always seemed pretty smart, but this makes no sense. He could've saved so much time and avoided building a whole new runtime by simply not using the completely wrong tool for the job.
These are completely different. Agents (aside from the model inference) are not CPU bound. You gain much more by having a wider user base than whatever marginal CPU cycles you would gain in Rust/Go.
My thinking is that they’re trying to capture that market for JavaScript before another AI company does. To put it bluntly they want to capture the revenue generated by writing JavaScript code, which is currently being captured by independent JavaScript developers. The reason for a JavaScript is that is the most ubiquitous language, and id guess there are more jobs available for JS/node than any other language.
Of course, as a JavaScript developer, this may just be my paranoia. <sweats profusely>
I’m guessing he was probably a JavaScript developer that wanted to make a game. He began building it using what he knew and then he hit the limitations of it. Rather than switching to something else, he tried to figure out why fast compile times weren’t possible and determined that they were possible and started to build a solution for it.
This take is interesting given we're all here congratulating Jarred for seeing that there was no tool to solve x so made it, and is now enjoying a likely nice payday. Be the change you want to see in the world?
It kinda reads like a case of survivorship bias. He is the one in a million to reach the good ending, despite starting with the wrong choice; though in this case, the wrong choice brought him on the road to the good ending.
Now the real question is, does the game loads significant better now, or does the performance still suck? In which case it might be more an excessive case of yak-shaving. And if yes, when can we except the release?
That’s kind of the opposite though. I guess if you’re saying that there’s an art to building things using the least efficient means possible just as there’s an art to being maximally efficient (like the 4k demo scene) then your point stands.
That's super strange since React by its nature assumes that controls are stateless - which games definitely are not. If you render your game inside a canvas then React decides it wants to recreate your control, then your whole game restarts.
He may have been serving a game in a canvas hosted in a Next.js app, but have done all the actual game (rendering, simulation, etc.) in something else. That’s a decent approach - Next can handle the header of the webpage and the marketing blog or whatever just fine.
But like... so can an index.html with a script tag? Am I missing something, where did you read that there was a lot of work involving the header or an attached marketing blog?
I'm sort of surprised to see that you used Claude Code so much. I had a vague idea that "Zig people" were generally "Software You Can Love" or "Handmade Software Movement" types, about small programs, exquisitely hand-written, etc, etc. And I know Bun started with an extreme attention to detail around performance.
I would have thought LLM-generated code would run a bit counter to both of those. I had sort of carved the world into "vibe coders" who care about the eventual product but don't care so much about the "craft" of code, and people who get joy out of the actual process of coding and designing beautiful abstractions and data structures and all that, which I didn't really think worked with LLM code.
But I guess not, and this definitely causes me to update my understanding of what LLM-generated code can look like (in my day to day, I mostly see what I would consider as not very good code when it comes from an LLM).
Would you say your usage of Claude Code was more "around the edges", doing things like writing tests and documentation and such? Or did it actually help in real, crunchy problems in the depths of low level Zig code?
I am not your target with this question (I don't write Zig) but there is a spectrum of LLM usage for coding. It is possible to use LLMs extensively but almost never ship LLM generated code, except for tiny trivial functions. One can use them for ideation, quick research, or prototypes/starting places, and then build on that. That is how I use them, anyway
Culturally I see pure vibe coders as intersecting more with entrepreneurfluencer types who are non-technical but trying to extend their capabilities. Most technical folks I know are fairly disillusioned with pure vibe coding, but that's my corner of the world, YMMV
> I had a vague idea that "Zig people" were generally "Software You Can Love" or "Handmade Software Movement" types, about small programs, exquisitely hand-written, etc, etc.
I feel like an important step for a language is when people outside of the mainline language culture start using it in anger. In that respect, Zig has very much "made it."
That said, if I were to put on my cynical hat, I do wonder how much of that Anthropic money will be donated to the Zig Software Foundation itself. After all, throwing money at maintaining and promoting the language that powers a critical part of their infrastructure seems like a mutually beneficial arrangement.
We never associated with Bun other than extending an invitation to rent a job booth at a conference: this was years ago when I had a Twitter account, so it's fair if Jarred doesn't remember.
If Handmade Cities had the opportunity to collaborate with Bun today, we would not take it, even prior to this acquisition. HMC wants to level up systems while remaining performant, snappy and buttery smooth. Notable examples include File Pilot [0] or my own Terminal Click (still early days) [1], both coming from bootstrapped indie devs.
I'll finish with a quote from a blog post [2]:
> Serious Handmade projects, like my own Terminal Click, don’t gain from AI. It does help at the margins: I’ve delegated website work since last year, and I enjoy seamless CI/CD for my builds. This is meaningful.
However, it fails at novel problems and isn’t practical for my systems programming work.
All that said, I congratulate Bun even as we disagree on philosophy. I imagine it's no small feat getting acquired!
> I had a vague idea that "Zig people" were generally "Software You Can Love" or "Handmade Software Movement" types, about small programs, exquisitely hand-written, etc, etc.
In my experience, the extreme anti-LLM people and extreme pro-vibecoding people are a vocal online minority.
If you get away from the internet yelling match, the typical use case for LLMs is in the middle. Experienced developers use them for some small tasks and also write their own code. They know when to switch between modes and how to make the most of LLMs without deferring completely to their output.
Most of all: They don't go around yelling about their LLM use (or anti-use) because they're not interesting in the online LLM wars. They just want to build things with the tools available.
It goes completely contrary to a lot of what I think is good software engineering. There is very little reuse, everything is ad-hoc, NIH-heavy, verbose, seemingly fragile (there's a lot of memory manipulation interwoven with business logic!), with relatively few tests or assurances.
And yet it works on many levels: as a piece of software, as a project, as a business. Therefore, how can it be anything but good engineering? It fulfils its purpose.
I can also see why it's a very good fit for LLM-heavy workflows.
I love zig, in my experience claude code is extremely good with the language if you invest lots of time on design sessions, to the point where I spend >90% of my time only discussing design with claude. The fact it has easy access to sources of the whole stdlib by just downloading the zig tarball makes it really simple to have a feedback loop where it implement most of the boilerplate on its own. The quality of AI code is really something that can be well controlled with clear guidelines, strict reviews, comprehensive design sessions, and a great test infrastructure
I interviewed for the Bun guys and totally flopped because I was not prepared for the interview format. It was "here's a task, do whatever you need to including AI to get it done". From that, I'd infer that the usage is pretty substantial.
Thanks, Jarred. Seeing what you built with Bun has been a real inspiration, the way one focused engineer can shift an entire ecosystem. It pushed me back into caring about the lower-level side of things again, and I’m grateful for that spark. Congrats on the acquisition, and excited to see what’s next
This is an interesting question; not to be too naive, but are there examples in the wild about this scenario? First I’ve heard of private APIs for something open source like this and my interest is piqued!
Amazing news, congrats! Been using Bun for a long while now and I love it.
Is there anything I could do to improve this PR/get a review? I understand you are def very busy right now with the acquisition, but wanted to give my PR the best shot:
You said elsewhere that there were many suitors. What is the single most important thing about Anthropic that leads you to believe they will be dominant in the coming years?
No idea about his feelings but believing that they will be dominant wouldn't have to be the reason he chose them. I could easily imagine that someone would decide based on (1) they offered enough money and (2) values alignment.
I love Bun and use it daily, but I'm still very frustrated by all the configuration that one needs ATM when working in the js ecosystem. Do you guys see yourself integrating more and more, and moving more and more towards a "convention over configuration", to bring a more streamlined dev experience (that languages like Golang and Rust have, for example)
on Bun's website, the runtime section features HTTP, networking, storage -- all are very web-focused. any plans to start expanding into native ML support? (e.g. GPUs, RDMA-type networking, cluster management, NFS)
Probably not. When we add new APIs in Bun, we generally base the interface off of popular existing packages. The bar is very high for a runtime to include libraries because the expectation is to support those APIs ~forever. And I can’t think of popular existing JS libraries for these things.
I've never personally used Bun. I use node.js I guess. What makes Bun fundamentally better at AI than, say, bundling a node.js app that can run anywhere?
If the answer is performance, how does Bun achieve things quicker than Node?
How much of your day-to-day is spent contributing code to the Bun codebase and do you expect it to decrease as Anthropic assigns more people to work on Bun?
I contributed to Bun one time for SQLite. I've a question about the licensing.
Will each contributor continue to retain their copyright, or will a CLA be introduced?
With Bun's existing OSS license and contribution model, all contributors retain their copyright and Bun retains the license to use those contributions. An acquisition of this kind cannot change the terms under which prior contributions were made without explicit agreement from all contributors. If Bun did switch to a CLA in the future, just like with any OSS project, that would only impact future contributions made after that CLA went into effect and it depends entirely on the terms established in that hypothetical CLA.
I know that one thing you guys are working on or are at least aware of is the size of single-file executables. From a technical perspective, is there a path forward on this?
I'm not familiar with Bun's internals, but in order to get the size down, it seems like you'd have to somehow split up/modularize Bun itself and potentially JavaScriptCore as well (not sure how big the latter is). That way only the things that are actually being used by the bundled code are included in the executable.
Is this even possible? Is the difficulty on the Bun/Zig side of things, or JSC, or something else? Seems like a very interesting (and very difficult) technical problem.
I have a PR that’s been sitting for awhile that exposes the extra options from the renameat2 and renameatx_np syscalls which is a good way to implement self-updaters that work even when multiple processes are updating the same path on disk at the same time. These syscalls are supported on Linux & macOS but I don’t think there’s an equivalent on Windows. We use these syscalls internally for `bun install` to make adding packages into the global install cache work when multiple `bun install` processes are running simultaneously
No high-level self updater api is planned right now, but yes for at least the low level parts needed to make a good one
I wonder if this is a sign of AI companies trying to pivot?
> Bun will ship faster.
That'll last until FY 2027. This is an old lie that acquirers encourage the old owner to say because they have no power to enforce it, and they didn't actually say it so they're not on the hook. It's practically a cheesy pickup line, and given the context, it kinda is.
On your first point: It doesn't read like that to me. It seems like they built one of their key products (Claude Code) on top of Bun, and want to have a say in it's development.
> Anthropic has direct incentive to keep Bun excellent.
Huh, this feels very odd to read and buying a company outright is definitely not the only way to push Bun to be excellent. Contributing to Bun from their developers, becoming a sponsor, donating through other means, buying 'consulting services' or similar, or even forking it and keeping it up to date would all be also steps towards keeping the Bun excellent.
This is vendoring a dependency on steroids, and first moment interests of community are not aligned with what Antropic needs, it will be interesting to see how this unfolds. History has thought us that this will end up with claims in the blog post not holding much weight.
since Anthropic is one of the only companies using the Bun Runtime, not just the bundler like most do, they want to make sure the runtime stays the focus. This is good for both companies and us tbh since they wont switch focus to whats popular at the moment
I find it a little sad, that there is almost no pushback on what a few people with deep pockets are trying to sell here. Normaly on HN an article on balcon gardening would be met with more critical thinking than this piece. Maybe instead of staring to the screen all day long take a break, think about what people with lots of money care about. And I don't judge, making money is nothing illegal. But Anthropic would be absolutely NOTHING without OSS. And then to see the kind of this effusive, submissive admiration and gratitude for their js wrapper thing makes me sick to my stomach.
I’ll be honest, while I have my doubts about the match of interests and cohesion between an AI company and a JS runtime company I have to say this is the single best acquisition announcement blog post I’ve seen in 20 years or so.
Very direct, very plain and detailed. They cover all the bases about the why, the how, and what to expect. I really appreciate it.
Best of luck to the team and hopefully the new home will support them well.
But how is another company that is also VC backed and losing money providing stability for Bun?
How long before we hear about “Our Amazing Journey”?
On the other hand, I would rather see someone like Bun have a successful exit where the founders seem to have started out with a passion project, got funding, built something out they were excited about and then exit than yet another AI company by non technical founders who were built with the sole purpose of getting funding and then exit.
Often it happens that VCs buy out companies from funds belonging to a fresh because the selling fund wants to show performance to their investors until "the big one", or move cash one from wealthy pocket to another one.
"You buy me this, next time I save you on that", etc...
"Raised $19 million Series A led by Khosla Ventures + $7 million"
"Today, Bun makes $0 in revenue."
Everything is almost public domain (MIT) and can be forked without paying a single dollar.
Questionable to claim that the technology is the real reason this was bought.
The real risk is not that Anthropic will run out of money, but that they will change their strategy to something that isn't Bun-based, and supporting Bun won't make sense for them any more.
I admit, it is a good acquisition announcement. I can’t remember the last acquisition announcement that was kept for more than 1-2 years. Leadership changes, priorities shift…
One thing I like about this, despite it meaning Bun will be funded, is Anthropic is a registered public benefit corporation. While this doesn't mean Anthropic cant fuck over the users of Bun, it at least puts in some roadblocks. The path of least-resistance here should be to improve Bun for users, not to monetize it to the point where it's no longer valuable.
Bun and Deno's goals seem quite different, I don't expect that to change. Bun is a one stop shop with an ever increasing number of built-in high-level APIs. Deno is focused on low level APIs, security, and building out a standard lib/ecosystem that (mostly) supports all JS environments.
People who like Bun for what it is are probably still going to, and same goes for Deno.
That being said I don't see how Anthropic is really adding long term stability to Bun.
I think Deno's management have been somewhat distracted by their ongoing lawsuits with Oracle over the release of the Javascript trademark.
I started out with Deno and when I discovered Bun, I pivoted. Personally I don't need the NodeJS/NPM compatability. Wish there was a Bun-lite which was freed of the backward compatability.
> Will this make it more or less likely for people to use Bun vs Deno?
I'm not sure it will make much of a difference in the short term.
For those who were drawn to Bun by hype and/or some concerns around speed, they will continue to use Bun.
For me personally, I will continue to use Node for legacy projects and will continue using Deno for current projects.
I'm not interested in Bun for it's hype (since hype is fleeting). I have a reserved interested in Bun's approach to speed but I don't see it being a significant factor since most JS speed concerns come from downloading dependencies (which is a once-off operation) and terrible JS framework practices (which aren't resolved by changing engines anyway).
----------------------------
The two largest problems I see in JS are:
1. Terrible security practices
2. A lack of a standard library which pushes people into dependency hell
Deno fixes both of those problems with a proper permission model and a standard library.
----------------------------
> And now that Bun doesn't need to run a profitable cloud company will they move faster and get ahead of Deno?
I think any predictions between 1-10 years are going to be a little too chaotic. It all depends on how the AI bubble goes away.
But after 10 years, I can see runtimes switching from their current engines to one based on Boa, Kiesel or something similar.
> Deno fixes both of those problems with a proper permission model and a standard library
Bun has a better standard library than Deno. You get a DB driver, S3 client, etc which on Deno are all third party deps. It was the main reason I got interested in Bun. The speed is nice though during dev. Everything feels instant.
As someone who have been using Deno for the last few years, is there anything that Bun does better? Bun seems to use a different runtime (JSC) which is less tested than V8, which makes me assume it might perform worse in real-world tasks (maybe not anymore?). The last time I checked Bun's source code, it was... quite messy and spaghetti-like, plus Zig doesn't really offer many safety features, so it's not that hard to write incorrect code. Zig does force some safety with ReleaseSafe IIRC, but it's still not the same as even modern C++, let alone Rust.
I'll admit I'm somewhat biased against Bun, but I'm honestly interested in knowing why people prefer Bun over Deno.
I haven't used Deno, but I do use Bun purely as a replacement for npm. It does the hard-linking thing that seems to be increasingly common for package managers these days (i.e. it populates your local node_modules with a bunch of hard links to its systemwide cache), which makes it vastly quicker and more disk-efficient than npm for most usage.
Even with a cold cache, `bun install` with a large-ish dependency graph is significantly faster than `npm install` in my experience.
I don't know if Deno does that, but some googling for "deno install performance vs npm install" doesn't turn up much, so I suspect not?
As a runtime, though, I have no opinion. I did test it against Node, but for my use case (build tooling for web projects) it didn't make a noticeable difference, so I decided to stick with Node.
Deno does that. It also refrains from keeping a local node_modules at all until/unless you explicitly ask it to for whatever compatibility reason. There are plugins to things like esbuild to use the Deno resolver and not need a node_modules at all (if you aren't also using the Deno-provided bundler for whatever reason such as it disappeared for a couple versions and is still marked "experimental").
I decided to stick with Node in general. I don't see any compelling reason to change it.
Faster install and less disk space due to hardlink? Not really all that important to me. Npm comes with a cache too, and I have the disk space. I don't need it to be faster.
With the old-school setup I can easily manually edit something in node_modules to quickly test a change.
No more node_modules? It was a cool idea when yarn 2 initially implemented it, but at the end of the day I prefer things to just work rather than debug what is and isn't broken by the new resolver. At the time my DevOps team also wasn't too excited about me proposing to put the dependencies into git for the zero-install.
Search for pointer exceptions or core dumps on Bun's GitHub issues and you'll see why people (should) use Deno over Bun, if only because Rust is a way more safe language than Zig.
This is a non sequitur. Both Rust and Zig and any other language has the ability to end in an exception state. Whether it be kernel exception, pointer exception, or Rust's panic! - these things exist.
The reason why you see so many GitHub issues about it is because that's where the development is. Deno is great. Bun is great. These two things can both be great and we don't have to choose sides. Deno has it's use case. Bun has it's. Deno want's to be secure and require permissions. Bun just wants to make clean, simple, projects. This fight between Rust vs The World is getting old. Rust isn't any "safer" when Deno can panic too.
I haven't verified this, but I would be willing to bet that most of Bun's issues here have more to do with interfacing with JavaScriptCore through the C FFI than Zig itself. this is as much a problem in Rust as it is in Zig. in fact, it has been argued that writing unsafe Zig is safer than writing unsafe Rust: https://zackoverflow.dev/writing/unsafe-rust-vs-zig/
I tried several times to port Node projects to Deno. Each time compatibility had "improved" but I still didn't have a working build after a few days of effort.
I don't know how Deno is today. I switched to Bun and porting went a lot smoother.
Philosophically, I like that Bun sees Node compatibility as an obvious top priority. Deno sees it as a grudging necessity after losing the fight to do things differently.
Which makes sense given that a big impetus for Deno's existence was the creator of Node/Deno (Ryan Dahl) wanting to correct things he viewed as design mistakes in Node.
> Bun seems to use a different runtime (JSC) which is less tested than V8, which makes me assume it might perform worse in real-world tasks (maybe not anymore?).
JSC is still the JS engine for WebKit-based browsers, especially Safari, and per Apple App Store regulations the only JS engine supposedly allowable in all of iOS.
It's more "mature" than V8 in terms of predating it. (V8 was not a fork of it and was started from scratch, but V8 was designed to replace it in the Blink fork from WebKit.)
It has different performance goals and performance characteristics, but "less tested" seems uncharitable and it is certainly used in plenty of "real-world tasks" daily in iOS and macOS.
My team has been using it in prod for about a year now. There were some minor bugs in the runtime's implementation of buffers in 1.22 (?), but that was about the only issue we ran into.
The nice things:
1. It's fast.
2. The standard library is great. (This may be less of an advantage over Deno.)
3. There's a ton of momentum behind it.
4. It's closer to Node.js than Deno is, at least last I tried. There were a bunch of little Node <> Deno papercuts. For example, Deno wanted .ts extensions on all imports.
5. I don't have to think about JSR.
The warts:
1. The package manager has some issues that make it hard for us to use. I've forgotten why now, but this in particular bit us in the ass: https://github.com/oven-sh/bun/issues/6608. We use PNPM and are very happy with it, even if it's not as fast as Bun's package manager.
Overall, Deno felt to me like they were building a parallel ecosystem that I don't have a ton of conviction in, while Bun feels focused on meeting me where I am.
I’ve been using Deno too. Although npm support has improved and it’s fine for me, I think Deno has more of a “rewrite the world” philosophy. For example, they created their own package registry [1] and their own web framework [2]. Bun seems much more focused on preexisting JavaScript projects.
It's interesting that people have directly opposite opinions on whether Deno or Bun are meant to be used with the existing ecosystem - https://news.ycombinator.com/item?id=46125049
As far as I know, modern Node compat in Deno is also quite great - I just import packages via 'npm:package' and they work, even install scripts work. Although I remember that in the past Deno's Node compat was worse, yes.
I really want to like Deno and will likely try it again, but last time I did it was just a bit of a pain anytime I wanted to use something built for npm (which is most packages out there), whereas bun didn't have that problem.
There's certainly an argument to be made that, like any good tool, you have to learn Deno and can't fall back on just reusing node knowledge, and I'd absolutely agree with that, but in that case I wanted to learn the package, not the package manager.
Edit: Also it has a nice standard library, not a huge win because that stuff is also doable in Deno, but again, its just a bit less painless
Looking at Bun's website (the comparison table under "What's different about Bun?") and what people have said here, the only significant benefit of Bun over Node.js seems to be that it's more batteries-included - a bigger standard library, more tools, some convenience features like compiling JSX and stripping TypeScript types on-the-fly, etc.
It's not clear to me why that requires creating a whole new runtime, or why they made the decisions they did, like choosing JSC instead of V8, or using a pre-1.0 language like Zig.
It just works. Whatever JavaScript/TypeScript file or dependencies I throw at it, it will run it without needing to figure out CJS or ESM, tsconfig, etc.
Same. I had a little library I wrote to wrap indexedDB and deno wouldn't even compile it because it referenced those browser apis. I'm sure it's a simple flag or config file property, or x, or y, or z, but the simple fact is, bun didn't fail to compile.
Between that and the discord, I have gotten the distinct impression that deno is for "server javascript" first, rather than just "javascript" first. Which is understandable, but not very catering to me, a frontend-first dev.
Crash. According to my experience trying it many times oves the past years.
It feels like a very unfocused project, every few months they introduce a new feature that is to replace an entire class of tools, while the original promise of "drop in Node replacement" was never fulfilled (or at least, that was the vibe for the past years when I was still paying attention).
We'll see how this works out but speed + lack of scope never works out well in the long term.
I've been using Bun since 2022 just to be trendy for recruitment (it worked, and still works despite it almost being 2026)
Bun is fast, and its worked as a drop in replacement for npm in large legacy projects too.
I only ever encountered one issue, which was pretty dumb, Amazon's CDK has hardcoded references to various package manager's lock files, and Bun wasn't one of them
At this stage I don't think either is better over the other. Deno has inexplicable high memory usage issues in Linux containers. Bun more or less suffers from the same with an added dose of segfaults.
Node.js is a no-brainer for anyone shipping a TS/JS backend. I'd rather deal with poor DX and slightly worse performance than risk fighting runtime related issues on deployment.
Linux needs to be a first class citizen for any runtime/langauge toolchain.
Is JSC less tested? I thought it was used in Safari, which has some market share.
I used bun briefly to run the output of my compiler, because it was the only javascript runtime that did tail calls. But I eventually added a tail call transform to my compiler and switched to node, which runs 40% faster for my test case (the compiler building itself).
Twice as fast at executing JavaScript? There's absolutely zero chance this is true. A JavaScript engine that's twice as fast as V8 in general doesn't exist. There may be 5 or 10 percent difference, but nothing really meaningful.
I find comments like this fascinating, because you're implicitly evaluating a counterfactual where Bun was built with Rust (or some other "interesting" language). Maybe Bun would be better if it were built in Rust. But maybe it would have been slower (either at runtime or development speed) and not gotten far enough along to be acquired by one of the hottest companies in the world. There's no way to know. Why did Anthropic choose Bun instead of Deno, if Deno is written in a better language?
Good question, hard to say, but I think it's mainly because of Zig. At its core Zig is marketed as a competitor to C, not C++/Rust/etc, which makes me think it's harder to write working code that won't leak or crash than in other languages. Zig embraces manual memory management as well.
I always figured Bun was the "enterprise software" choice, where you'd want to use Bun tools and libraries for everything and not need to bring in much from the broader NPM library ecosystem.
Deno seems like the better replacement for Node, but it'd still be at risk of NPM supply chain attacks which seems to be the greater concern for companies these days.
Is it just me, but I don't find npm that slow? Sure it's not a speed demon, but I rarely need to do npm install anyways so it's not a bottleneck for me.
For deploy, usually running the attached terraform script takes more time.
So while a speed increase is welcome, but I don't feel it gives me such a boost.
Hard to say it makes no sense when you don't know how much they were acquired for. I would guess it is a trivial amount relative to Anthropic's war chest.
From the comments here it sounds like most people think the amount Anthropic paid for the company was probably not much more than the VC funding which Bun raised.
How would the payout split work? It wouldn’t seem fair to the investors if the founder profited X million while the investors get their original money returned. I understand VC has the expectation that 99 out of 100 of investments will net them no money. But what happens in the cases where money is made, it just isn’t profitable for the VC firm.
What’s to stop everyone from doing this? Besides integrity, why shouldn’t every founder just cash out when the payout is life-changing?
Is there usually some clause in the agreements like “if you do not return X% profit, the founder forfeits his or her equity back to the shareholders”?
Anthropic has been trying to win the developer marketshare, and has been quite successful with Claude Code. While I understand the argument that this acquisition is to protect their usage in CC or even just to acquire the team, I do hope that part of their goal is to use this to strengthen their brand. Being good stewards of open source projects is a huge part of how positively I view a company.
I think because their models are open (e.g. CC can send any instruction and it’ll use your max plan), they need to keep the code obfuscated to prevent people from sending everybody and their mother through that API.
Codex has the opposite issue. It has an open client, which is relatively pointless, because it will accept only one system prompt and one prompt only.
Well, if they suddenly changed the license, we'd get a new Redis --> Valkey situation.
Or even more recently, look at minio no longer maintaining their core open source project!
I mean if you're getting X number of users per day and you don't need to pay for bandwidth or anything, there's gotta be SOME way to monetize down the line.
If your userbase or the current CEO likes it or not.
I've seen a few of these seemingly random acquisitions lately, and I congratulate the companies and individuals that are acquired during this gold rush, but it definitely feels awkwardly artificial.
Quote from the CEO of Anthropic in March 2025:
"I think we'll be there in three to six months where AI is writing 90% of the code and then in 12 months we may be in a world where AI is writing essentially all of the code"
From the article, Claude Code is being used extensively to develop Bun already.
> Over the last several months, the GitHub username with the most merged PRs in Bun's repo is now a Claude Code bot. We have it set up in our internal Discord and we mostly use it to help fix bugs. It opens PRs with tests that fail in the earlier system-installed version of Bun before the fix and pass in the fixed debug build of Bun. It responds to review comments. It does the whole thing.
You do still need people to make all the decisions about how Bun is developed, and to use Claude Code.
"Wasting" is doing a lot of work in that sentence.
They're effectively bringing on a team that's been focused on building a runtime for years. The models they could throw at the problem can't be tapped on the shoulder, and there's no guarantee they'd do a better job at building something like Bun.
I think this wound up being close enough to true, it's just that it actually says less than what people assumed at the time.
It's basically the Jevons paradox for code. The price of lines of code (in human engineer-hours) has decreased a lot, so there is a bunch of code that is now economically justifiable which wouldn't have been written before. For example, I can prompt several ad-hoc benchmarking scripts in 1-2 minutes to troubleshoot an issue which might have taken 10-20 minutes each by myself, allowing me to investigate many performance angles. Not everything gets committed to source control.
Put another way, at least in my workflow and at my workplace, the volume of code has increased, and most of that increase comes from new code that would not have been written if not for AI, and a smaller portion is code that I would have written before AI but now let the AI write so I can focus on harder tasks. Of course, it's uneven penetration, AI helps more with tasks that are well-described in the training set (webapps, data science, Linux admin...) compared to e.g. issues arising from quirky internal architecture, Rust, etc.
Maybe he was correct in the extremely literal sense of AI producing more new lines of code than humans, because AI is no doubt very good at producing huge volumes of Stuff very quickly, but how much of that Stuff actually justifies its existence is another question entirely.
Why do people always stop this quote at the breath? The rest of it says that he still thinks they need tech employees.
> .... and in 12 months, we might be in a world where the ai is writing essentially all of the code. But the programmer still needs to specify what are the conditions of what you're doing. What is the overall design decision. How we collaborate with other code that has been written. How do we have some common sense with whether this is a secure design or an insecure design. So as long as there are these small pieces that a programmer has to do, then I think human productivity will actually be enhanced
(He then said it would continue improving, but this was not in the 12 month prediction.)
I actually like claude code, but that was always a risky thing to say (actually I recall him saying their software is 90% AI produced) considering their cli tool is literally infested with bugs. (Or it least it was last time I used it heavily. Maybe they've improved it since.)
I'm curious what people think of quotes like these. Obviously it makes an explicit, falsifiable prediction. That prediction is false. There are so many reasons why someone could predict that it would be false. Is it just optimistic marketing speech, or do they really believe it themselves?
Curious about the deal value/price — any clues whether it was just to make existing investors even (so say up to $30M) or are we talking some multiple? But if it's a multiple, even 2x sounds a bit crazy.
One option is that the current Bun shareholders didn't see a profitable future and didn't even care if they were made even and a return of the remaining cash was adequate.
Another option is that this was an equity deal where Bun shareholders believe there is still a large multiple worth up potential upside in the current Anthropic valuation.
i don’t get it either - bun being the foundation of tons of AI tools is like a best possible outcome, what were they hoping for when they raised the money? Or is this just an admission of “hey, that was silly, we need to land this however we can”? Or do they share major investors and the therefore this is just a consolidation? (Edit: indeed, KP did indeed invest $100M in Anthropic this year. I’m also confused - article states Bun raised 26M but the KP seed round was 7, did they do the A too but unannounced? Notably, the seed was summer 2022 and chatgpt was Nov 30, so the world is different, did the hypothesis change?)
it boils down to - we didn't have full conviction that over the long run we will prove superior to node.js, however a.i company burning a lot of cash, has invested in us by basing their toolchain on us - so they have no option to acquire-hire us.
I don't really see how Bun fits as an acquisition for an AI company. This seems more like "we have tons of capital and we want to buy something great" than "Bun is essential to our core business model".
If Anthropic wants to own code development in the future, owning the full platform (including the runtime) makes sense.
Programming languages all are a balance between performance/etc and making it easy for a human to interact with. This balance is going to shit as AI writes more code (and I assume Anthropic wants a future where humans might not even see the code, but rather an abstraction of it... after all, all code we look at is an abstraction on some level).
Claude Code running on Bun is an obvious justification, but Buns features (high performance runtime, fast starts, native TS) are also important for training and inference. For instance, in inference you develop a logical model in code that maps to a reasoning sequence, and then execute the code to validate and refine the model, then use this to inform further reasoning. Bun, which is highly integrated and highly focused on performance, is an ideal fit for this. Having Bun in house means that you can use the feedback from all of automation driven execution of Bun to drive improvements to its core.
oh, I really dislike that. I don't want AI companies encroaching more in my development workflow. Used to really enjoy Bun, but don't want support Anthropic at all. Will switch back to another runtime.
Yeah, I really get that. I’ve been a fan of zig and bun since their inception, but, AI corp deep in the dev chain? I feel uncomfortable, because no one knows when they’ll start steering things into weird directions.
Bun is pretty cool.
I maintain a Node.js library and updated my Node.js engine version and my library just didn't work on the latest version... In frustration, I decided to try Bun for the first time... I had never used it before but my library worked straight away, no warnings, no errors. I have never seen that level of compatibility before when a library works better with an alternative engine than the one it was designed for.
I did end up fixing Node.js compatibility later but it was extra work. Felt like they just created busy-work. Node.js maintainers should stop deprecating perfectly good features and complicating their modules.
I use Claude Code CLI daily - it's genuinely changed how I work. The $1B number sounds crazy but honestly tracks with how good the tool is. Curious how Bun integration will show up in practice beyond the native installer.
Doesn’t sound crazy at all? My Max subscription costs me more than all the other netflix/spotify etc combined, but I pay it happily, and spotify would go before Claude does.
Anyone know how much Anthropic paid for Bun? I assume it was at least $26M, so Bun could break even and pay back its own investors, but I didn't see a number in the announcements from Anthropic or Bun.
It's more honest than the Replicate answer but I think inevitably if you can't raise the next round and you get distracted by the shiny AI that this is the path taken by many teams. There is absolutely nothing wrong with that. There was an exuberant time when all the OSS things were getting funded, and now all AI things get funded. For many engineer founders, it's a better fit to go build deep technical stuff inside a bigger company. If I had that chance I would probably have taken it too. Good luck to the Bun team!
Why not something like c#: native, fast, crossplatform, strongly-typed, great tooling, supports both scripting (ie single file-based) and compiled to a binary with no dependency whatsoever (nativeAOT), great errors and error stacks, list goes on.
All great for AI to recover during its iterations of generating something useful.
AI are good at JS because basically there is a ton of JS code available publicly without usage restriction: the JS code published to be executed in your browser. Most of JS code attached to web pages has no explicit license, but the implicit license is that anyone can download it and run it. Same for HTML and CSS. So using that public code to train models is a no brainer.
Sadly, this will be the trend with things moving forward. JS is perceived as a good language and LLMs are meant to make them even easier to write. It is not about the mertis of a language. It's about which languages LLMs are "good" at.
You could make a better argument for Go (compiles to native for multiple targets, zero actual dependencies (no need for a platform or virtual machine on the target)
Same reason AIs also use Python and DBMSes offer JS or Py UDFs easily, interpreted languages take no build time and are more portable. JS is also very popular.
Might also be a context window thing. Idk how much boilerplate C# has, but others like Java spam it.
There’s like 100x more JS developers than C# developers. JS can also run code very quickly, where with an AOT language, you need to AOT compile it. For tool calls, eval-as-a-service, running in browser JS is far ahead of C#.
One other angle yet mentioned: JS is browser native. No matter how slow it is, browser is now the LCD. Similar server-client codebase, while ugly, is another plus.
Hahaha congratulations. This is amazing. The most unlikely outcome for a devtools team. Fascinating stuff.
This is promising for Astral et al who I really like but worried about their sustainability. It does point to being as close to the user as possible mattering.
Extrapolating and wildly guessing, we could end up with using all that mostly idle CPU/RAM (the non-VRAM) on the beefy GPUs doing inference on agentic loops where the AI runs small JS scripts in a sandbox (which Bun is the best at, with its faster startup times and lower RAM use, not to mention its extensive native bindings that Node.js/V8 do not have) essentially allowing multiple turns to happen before yielding to the API caller. It would also go well with Anthropic's advanced tool use that they recently announced. This would be a big competitive advantage in the age of agents.
This decision is honestly very confusing to me as a constant user of Claude Code (I have 3 of them open at the moment.)
So many of the issues with it seem to be because ... they wrote the damn thing in JavaScript?
Claude is pretty good at a constrained task with tests -- couldn't you just port it to a different language? With Claude?
And then just ... the huge claude.json which gets written on every message, like ... SQLite exists! Please, please use it! The scrollback! The Keyboard handling! Just write a simple Rust or Go or whatever CLI app with an actual database and reasonable TUI toolkit? Why double down and buy a whole JavaScript runtime?
Ink (and modern alternatives) probably are the best TUI toolkit. If you want to write a UI that's genuinely good, you need e.g. HTML, or some way to express divs and flex box. There isn't really another way to build professional grade UIs; I love immediate mode UI for games, but the breadth of features handled by the browser UI ecosystem is astonishing. It is a genuinely hard problem.
And if you're expressing hierarchical UI, the best way to do it is HTML and CSS. It has the richest ecosystem, and it is one of the most mature technologies in existence. JS / TS are the native languages for those tools. Everything is informed by this.
Of course, there are other options. You could jam HTML and CSS into (as you mention) Rust, or C, or whatever. But then the ecosystem is extremely lacking, and you're reinventing the wheel. You could use something simpler, like QML or handrolled. But then you lose the aforementioned breadth of features and compatibilities with all the browser code ever written.
TypeScript is genuinely, for my money, the best option. The big problem is that the terminal backends aren't mature (as you said, scrollback, etc). But, given time and money, that'll get sorted out. It's much easier to fix the terminal stuff than to rewrite all of the browser.
I have to admit this was my first thought, too. I'm pretty obsessed with Claude Code, but the actual app is so incredibly poorly engineered for something that doesn't even do that much.
Rust, Go, whatever -- writing a good TUI isn't that hard of a problem. Buying an entire VC funded JS runtime company isn't how you solve it.
“Port it to a different language” a language that’s more out of distribution? Bad devex. Store data as an unreadable binary file? Bad devex.
Stay in distribution and in the wave as much as possible.
Good devex is all you need. Claude code team iterates and ships fast, and these decisions make total sense when you realize that dev velocity is the point.
All vendors will have to implement test time code execution, solution exploration, etc. as it's a low hanging fruit with huge gains, so I see it as a great hire.
Love Bun, happy for you guys!
I'm wondering if Bun would be a good embedded runtime for Claude to think in. If it does sandboxing, or if they can add sandboxing, then they can standardize on a language and runtime for Claude Code and Claude Desktop and bake it into training like they do with other agentic things like tool calls. It'd be too risky to do unless they owned the runtime.
So many comments about reasoning here, yet none about the very obvious one, it's not stability of the infrastructure, it's future direction of a product like Claude Code. They need to know how to continue their optimisation machine to fit developers needs the best way possible (for good or for worse).
I guess we should wait for some opt-out telemetry some time soon. It'll be nothing too crazy at first, but we'll see how hungry they are for the data.
This explains why Claude started transpiling & running JavaScript code! Yesterday, when I asked it to generate a document for me in JavaScript, it generated the JavaScript and then ran it to generate a document. I had never actually seen it compile and run any code before. It only would ever output code and either use the shell (Claude code) to run it on my local computer or allow me to copy and paste it.
There's no reason to run agents on expensive AI platforms or on GPUs - when you can have the AI create an agent in JS and thus runs with very high performance and perfect repeatability on far less expensive CPUs.
At the very least there must be some part of the agent tasks that can be run in JS, such as REST APIs, fetching web results, parsing CSV into a table, etc.
Considering that 1) Bun is written in Zig, 2) Zig has a strict no-AI policy [1], and 3) Bun has joined Claude, it seems that Bun and Zig are increasingly culturally apart.
You’re reading a code of conduct for contributing to the zig project. I don’t think everything there is guidance for everything written in zig, eg ‘English is encouraged’ is something one might not want for a project written in zig by native French-speakers, and I don’t think that’s something zig would want to suggest to them. I read the AI part is much more motivated by the asymmetries of open source project contribution than any statement about the language itself. Fly-by AI contributions are bad because they make particularly poor use of maintainer time. Similar to the rule on proposing language changes, which can suck up lots of reading/thinking/discussion time. When you have people regularly working together (eg those people in anthropic working on bun) the incentives are different because there is a higher cost to wasting your colleague’s time.
Nothing I found says anything about Zig folks being inherently against AI. It just looks like they don’t want to deal with “AI Slop” in contributions to their project, which is very understandable.
Since when is a CLI tool like this a sufficiently demanding technical project that it needs to buy the runtime just to get sufficient support?
This just isn't the hard part of the product.
Like if I was building a Claude Code competitor and I acquired bun, I wouldn't feel like I had an advantage because I could get more support with like fs.read?
Has CC always used Bun? When it tries it out many months ago it was an npm install not bun install in their instructions (although I did use bun install myself). Just odd that if they were using bun, why the installation wasn’t specifically a “bun install” (I suppose they were trying to keep it vanilla for the npm masses?)
What matters: it's staying open source and MIT licensed. I sincerely hope it stays that way. Congrats to the Bun team on making a great tool and getting the recognition they deserve.
> Being part of Anthropic gives Bun: Long-term stability.
Let's see. I don't want to always be the downer but the AI industry is in a state of rapid flux with some very strong economic headwinds. I wouldn't confidently say that hitching your wagon to AI gives you long term stability. But as long as the rest of us keep the ability to fork an open source project I won't complain too much.
(for those who are disappointed: this is why you stick with Node. Deno and Bun are both VC funded projects, there's only one way that goes. The only question is timeline)
Nothing gives you long term stability in tech. You have to constantly work at staying stable, and it isn't always up to anything the company is in control of, no matter what ownership they have.
Owning your runtime is not about developer experience at the scale of Claude Code, it’s about your execution-surface area and the control you have over it.
Agentic systems are no longer just model-driven — they are increasingly runtime-driven through tools, sandboxes, and orchestration layers. When agents are writing code, executing tests, calling external tools, and validating outcomes, the reliability of the entire system becomes a function of the runtime and environment, not just the model.
Controlling the runtime gives Anthropic vertical control across:
- Packaging and distribution
- Execution semantics
- Performance characteristics
- Security surface area
- Operational stability
Of course, owning a JavaScript runtime does not magically make runtime deterministic. The dominant sources of variability still sit lower in the stack: OS behaviour, native dependencies, filesystem semantics, scheduling, hardware differences, and network effects. Runtime ownership is necessary, but not sufficient, for true runtime determinism.
What this does signal is a strategic shift in where value is being captured.
Model capability is no longer the only critical layer.
The execution plane is becoming just as strategic too, can see this in ChatGPT 5’s dynamic model routing capability as well as ecosystem wide Tool Calling and MCP adoption, which are all aimed at increasing LLM determinism through traditional software stacks.
Vertical integration here looks far less like a tooling move and far more like a control-plane strategy: consolidate the stack, reduce dependency entropy, and shrink the surface area where behaviour can diverge.
Intelligence may live in the model, but reliability, scalability, and trust are increasingly properties of the system that executes it.
Look Bun is a great product but something hilarious about the company that is “going to replace all software developers with AI” BUYING software. You are building a product that is supposed to make software cost 0 right? Why wouldn’t you just “vibe” code yourself Bun?
Those aren't your customers. The people that want to build things with bun are. The problem with people who already know how to code is that they have opinions if they actually read the generated code. If you sell to people who don't (for whatever reason), you face less criticism.
This reads more like Anthropic wanted to hire Jarred and Jarred wants to work with AI rather than build a Saas product around bun. I doubt it has anything to do with what is best for bun the project. Considering bun always seemed to value performance more than all else, the only real way for them to continue pursuing that value would be to move into the actual js engine design. This seems like a good pivot for Jarred personally and likely a loss for bun.
It doesn't read like that to me at all. This reads to me like Anthropic realizing that they have $1bn in annual revenue from Claude Code that's dependent on Bun, and acquiring Bun is a great and comparatively cheap way to remove any risk from that dependency.
Nah, it reads like the normal logic behind the consulting model for open source monetization, except that Bun was able to make it work with just one customer. Good for them, though it comes with some risks, especially when structured as an acquisition.
> Long-term stability. a home and resources so people can safely bet their stack on Bun.
Isn't it the opposite? Now we've tied Bun to "AI" and if the AI bubble or hype or whatever bursts or dies down it'd impact Bun.
> We had over 4 years of runway to figure out monetization. We didn't have to join Anthropic.
There's honestly a higher chance of Bun sticking out that runway than the current AI hype still being around.
Nothing against Anthropic but with the circular financing, all the debt, OpenAI's spending and over-valuations "AI" is the riskier bet than Bun and hosting.
Yeah that’s the main part that puzzled me, super happy for the team that they got a successful exit, but I wouldn’t really consider Anthropic’s situation to be stable…
Yeah, no reader of tech news will take an acquisition of a company with four years of runway as anything but decreasing the odds their product will still be around (and useful to the same audience…) in four years. Even without being tied to a company with lots of exposure to a probable bubble.
Wondering to what degree this was done to support Anthropic’s web crawler. Would assume that having a whole JS runtime rather than just a HTTP client could be rather useful. Just hypothesising here, no clue what they use for their crawler.
So Anthropic sees its CLI (in TypeScript) as the first-class product and maybe planning to expand the claude code with more JS based agents / ecosystem? Especially owning the runtime gives a lot of control over developer experience.
Congratulations to the team. Knowing some of the folks on the Bun team I can not say I am surprised. They are the top 0,001% of engineers, writing code out of love. I’m hugely bullish on Anthropic, this is a great first acquisition.
Godspeed. Seems like a good pairing. Bun is sort of the only part of the JS ecosystem I like, and Code has become such an important tool for my work, that I think good things will come out of this match. Go Bundler as well.
I think this acquisition in reality has more to do with developer goodwill? And a little to do with the shell game of making these AI companies hard to value because they collect assets like this.
I’m curious to what the acquisition price was. Bun said they’ve raised $26 million so I’m assuming the price tag has to be a lot higher than that for investors to agree to an acquisition.
Congrats. This is the first time I remember reading a genuine, authentic story about a sale. Much preferred over “this is about continuing the mission until my earn-out is complete.”
So, what if Claude Code starts using Bun in all applicable situations? If model providers train their models to use a tech stack beneficial to their business interests?
Wouldn’t it make more sense to write the same functionality using a more performant, no-gc language? Aren’t competitors praised for their CLIs being faster for that reason?
With AI tooling, we are in the era where rapid iteration on product matters more than optimal runtime performance. Given that, implementing your AI tooling in a language that maximizes engineer productivity makes sense, and I believe GC does that.
Bun has completely changed my outlook on the JS ecosystem. Prior to Bun, there was little focus on performance. Now the entire space rallies around it.
> Prior to Bun, there was little focus on performance.
This is just completely insane. We went through more than a decade of performance competition in the JS VM space, and the _only_ justification that Google had for creating V8 was performance.
> The V8 engine was first introduced by Google in 2008, coinciding with the launch of the Google Chrome web browser. At the time, web applications were becoming increasingly complex, and there was a growing need for a faster, more efficient JavaScript engine. Google recognized this need and set out to create an engine that could significantly improve JavaScript performance.
I guess this is the time we live in. Vibe-coded projects get bought by vibe-coded companies and are congratulated in vibe-coded comments.
I don't know for sure, but it's definitely the first tool of that value to have a persistent strobing (scroll position) bug so bad that passersby ask me if I'm okay when they see it.
Terraform gets to $600mm if you squint really hard make up stuff. Kubectl though. Whatever you want to say about kubernetes complexity, it does get a bunch of money run through it. We could also look at aws-cli, gcloud and az, and if we assign cloud budgets that get run through there, I'm sure it's in the hundreds of millions. Then there's git. Across the whole ecosystem, there's probably a cool couple billion floating through there. gh is probably much smaller. Other tools like docker and ansible come to mind, though those are not quite as popular. Cc only hits $1B ARR if you squint really hard in the first place, so I think in this handwavy realm, I'd say aws-cli comes first, then kubectl, then git, with maybe docket and terraform in the mix as well. Nonetheless, Claude is a really awesome cli tool that I use most days, I find.
Sounds like the goal is to bundle up Bun with Claude Code insanely tightly, to the point where it doesn't matter if you have nodejs installed locally, but also they can optimize key things for Claude Code's Bun runtime as needed. It's a brilliant acquisition, and bun stays open source, which allows it to continue to grow, to Anthropics benefit and everyone else's.
on the post they try to reassure the following question
"If I bet my work project or company's tech stack on Bun, will it still be around in five or ten years?"
and the thing is that we don't know if Anthropic itself will be around 5 to ten years
Congrats Jarred and team! You have saved humanity many hours already, and I'm sure with Anthropic's backing, you will spare us many more. Farewell would-be headaches from Node & NPM tooling and waiting for builds and tests and package updates. Exciting times ahead!
Using bun on a side project reinvigorated my love of software development during a relatively dark time in my life, and part of me wonders if I would have taken the leap onto my current path if it weren't for the joy and feeling of speed that came from working with bun!
i really think this is part of the pitch deck for bun's funding. that a bigger company would acquire it for the technology. the only reason an AI company or any company for that matter would acquire it would be to:
So far, someone from the bun team has left a bunch of comments like
> Poor quality code
...and all the tests still seem to be failing. I looked through the code that the bot had generated and to me (who to be fair is not familiar with the bun codebase) it looks like total dogshit.
But hey, maybe it'll get there eventually. I don't envy "taylordotfish" and the other bot-herders working at Oven though, and I hope they get a nice payout as part of this sale.
So you pushed a PR that breaks a bunch of tests, added a 5 layer nested if branch block that mixes concerns all over the place, then ignored the reviewer for three weeks, and you’re surprised they didn’t approve it?
(1) Bun is what technical startups should be. Consistently excellent decisions, hyper focused on user experience, and a truly excellent technical product.
(2) We live in a world where TUIs are causing billion dollar acquisitions. Think about that. Obviously, Bun itself is largely orthogonal to the TUIs. Just another use case. But also obviously, they wouldn't have been acquired like this without this use case.
(3) There's been questions of whether startups like Bun can exist. How will they make money? When will they have to sell out one of the three principles in (1) to do so? The answer seems to be that they don't; at least, not like we expected, and in my opinion not in a sinister way.
A sinister or corrupting sell out would be e.g. like Conan. What started as an excellent tool became a bloated, versioned mess as they were forced to implement features to support the corporate customers that sustained them.
This feels different. Of course, there will be some selling out. But largely the interests of Anthropic seem aligned with "build the best JS runtime", since Anthropic themselves must be laser focused on user experience with Claude Code. And just look at Opencode [^1] if you want to see what leaning all the way into Bun gets you. Single file binary distribution, absurdly fast, gorgeous. Their backend, OpenTUI [^2], is a large part of this, and was built in close correspondence with the Bun folks. It's not something that could exist without Bun, in my opinion.
(4) Anthropic could have certainly let Bun be a third party to which they contributed. They did not have to purchase them. But they did. There is a strange not-quite altruism in this; at worst, a casting off of the exploitation of open source we often see from the biggest companies. Things change; what seems almost altruistic now could be revealed to be sinister, or could morph into such. But for now, at least, it feels good and right.
Can anyone provide some color around this: "I started porting esbuild's JSX & TypeScript transpiler from Go to Zig"? Hypothetical benefits include monolanguage for development, better interoperability with C and C++, no garbage collection, and better performance. What turned out to be realized and relevant here? Please, no speculation or language flames or wars.
Interesting. Looking through a strategic lens, I feel like this is related to the $1,000 free credit for Claude Code Web (I used a few hundred). What the heck are they aiming for? CodeAct? (https://arxiv.org/abs/2402.01030)
Good luck, always worried about stuff like that because it happened so many times and the product got worse eventually. At the same time, ai understand how much effort went into building something like Bun and people need to fund their life's somehow, so there's that.
Look, if a terminal emulator can raise $67 million by riding the AI hypewave then a Javscript runtime can do the same. Nobody ever said that AI investments and acquisitions have to make any sense.
A lot of people seem confused about this acquisition because they think of Bun as a node.js compatible bundler / runtime and just compare it to Deno / npm. But I think its a really smart move if you think of where Bun has been pushing into lately which is a kind of cloud-native self contained runtime (S3 API, SQL, streaming, etc). For an agent like Claude Code this trajectory is really interesting as you are creating a runtime where your agent can work inside of cloud services as fluently as it currently does with a local filesystem. Claude will be able to leverage these capabilities to extend its reach across the cloud and add more value in enterprise use cases
Yea, they just posted this a few days ago:
https://www.anthropic.com/engineering/advanced-tool-use
They discussed how running generated code is better for context management in many cases. The AI can generate code to retrieve, process, and filter the data it needs rather than doing it in-context, thus reducing context needs. Furthermore, if you can run the code right next to the server where the data is, it's all that much faster.
I see Bun like a Skynet: if it can run anywhere, the AI can run anywhere.
Java can run anywhere too
What do you mean by "context" here?
Jesus wept, for the nerds joyfully want skyney
Yea - if you want a paranoidly-sandboxed, instant-start, high-concurrency environment, not just on beefy servers but on resource-constrained/client devices as well, you need experts in V8 integration shenanigans.
Cloudflare Workers had Kenton Varda, who had been looking at lightweight serverless architecture at Sandstorm years ago. Anthropic needs this too, for all the reasons above. Makes all the sense in the world.
Bun isn't based on V8, it's JavaScriptCore, but your point still stands.
you left out the best part...what happened to Kenton? He looked at lightweight serverless architecture..and then what?
> Yea - if you want a paranoidly-sandboxed, instant-start, high-concurrency environment, not just on beefy servers but on resource-constrained/client devices as well, you need experts in V8 integration shenanigans.
To be honest, that sounds more like a pitch for deno than for bun, especially the “paranoidly sandboxed” part.
It's fine but why is Js a good language for agents? I mean sure its faster than python but wouldn't something that compiles to native be much better?
JS has the fastest, most robust and widely deployed sandboxing engines (V8, followed closely by JavaScriptCore which is what Bun uses). It also has TypeScript which pairs well with agentic coding loops, and compiles to the aforementioned JavaScript which can run pretty much anywhere.
It's widespread and good enough. The language just doesn't matter that much in most cases
TS is enormous, has endless training data, and can interact with virtually anything on the Internet these days. Also, strong typing is very very useful for AI coding context.
The answer is typescript is a much simpler and more pleasant developer experience than any other language. These are products they need to, and often originate from, fast churn of code/features.
Otherwise they’d be building these types of things in Rust.
Isn't what you're describing just a set of APIs with native bindings that the LLM can call?
I'm not sure I understand why it's necessary to even couple this to a runtime, let alone own the runtime?
Can't you just do it as a library and train/instruct the LLM to prefer using that library?
Mostly, just Jarred Sumner makes it worth it for Anthropic.
I'm not confused about the acquisition but about the investment. What were the investors thinking? This is an open source development tool with (to date), 0$ of revenue and not even the beginnings of a plan for getting such a thing.
The acquisition makes more sense. A few observations:
- no acquisition amount was announced. That indicates some kind of share swap where the investors change shares for one company into another. Presumably the founder now has some shares in Anthropic and a nice salary and vesting structure that will keep him on board for a while.
- The main investor was Kleiner Perkins. They are also an investor in Anthropic. 100M in the last round, apparently.
Everything else is a loosely buzzword compatible thingy for Anthropic's AI coding thingy and some fresh talent for their team. All good. But it's beside the point. This was an investor bailout. They put in quite a bit of money in Bun with exactly 0 remaining chance of that turning into the next unicorn. Whatever flaky plan there once might have been for revenue that caused them to invest, clearly wasn't happening. So, they liquidated their investment through an acquihire via one of their other investments.
Kind of shocking how easy it was to raise that kind of money with essentially no plan whatsoever for revenue. Where I live (Berlin), you get laughed away by investors (in a quite smug way typically) unless you have a solid plan for making them money. This wouldn't survive initial contact with due diligence. Apparently money still grows on trees in Silicon Valley.
I like Bun and have used it but from where I'm sitting there was no unicorn lurking there, ever.
They don't need Bun to make revenue, but they need Bun to continue existing and growing for their products to make revenue. Now they can ensure its survival, push for growth, and provide resources so that Bun can build the best product rather than focus on making money.
Investors are really bad at predicting up front what can become a unicorn and what can’t.
Could also be a way to expand the customer for Claude Code from coding assistant to vibe coding, a la Replit creating a hosted app. CC working more closely with Bun could make all that happen much faster:
> Our default answer was always some version of "we'll eventually build a cloud hosting product.", vertically integrated with Bun’s runtime & bundler.
The writeup makes it sound like an acquihire, especially the "what changes" part.
ChatGPT is feeling the pressure of Gemini [0]. So it's a bit strange for Anthropic to be focusing hard on its javascript game. Perhaps they see that as part of their advantage right now.
[0] https://timesofindia.indiatimes.com/technology/tech-news/goo...
>Claude will be able to leverage these capabilities to extend its reach across the cloud and add more value in enterprise use cases
100%. even more robust if paired with an overlay network which provides identity based s3 access (rather than ip address/network based). else server may not have access to s3/cloud resource, at least for many enterprises with s3 behind vpn/direct connect.
ditto for cases when want agent/client side to hit s3 directly, bypassing the server, and agent/client may not have permitted IP in FW ACL, or be on vpn/wan.
Java was doing "cloud-native, stripped down (jlink) image, self-contained runtime with batteries included" long before Bun existed. There's also GraalVM for one executable binary if one's ambitious.
I don't get the whole 'cloud' thing for AI agents. It feels forced. Who is actually using these services?
Non-developers usually prefer them to IDE or terminal based tools.
if I would guess Anthropic is (rightly) frustrated with the state of the js ecosystem and is taking the best attempt so far to make the js experience much more streamlined for their developers. Convention over configuration might finally be coming to the js ecosystem?
That's a really cool use case and seems super helpful. working cloud native is a chore sometimes. having to fiddle with internal apis, acl/permissions issues.
I'm also confused.. Why does a generic AI company that helps coding as one of main offering get deeply in bed with one tech stack
I mean would it have made sense to acquire golang if it were on sale?
They want to make sure the runtime they depend on continues to be maintained. It's still niche and new, so its continued existence isn't as sure as something like Go.
[flagged]
This matches some previous comments around LLMs driving adoption of programming languages or frameworks. If you ask Claude to write a web app, why not have it use your own framework, that it was trained on, by default?
Currently Claude etc. can interact with services (including AWS) via MCPs.
What the user you're replying to is saying the Bun acquisition looks silly as a dev tool for Node. However if you look at their binding work for services like s3[0], the LLM will be able to interact directly with cloud services directly (lower latency, tighter integration, simplified deployment).
0: https://bun.com/docs/runtime/s3
This is an insanely good take I never thought of.
As a commandline end user who prefers to retreive data from the www as text-only, I see deno and bun as potential replacements (for me, not necessarily for anyone else) for the so-called "modern" browser in those rare cases where I need to interpret Javascript^1
At present the browser monstrosity is used to (automatically, indiscriminantly) download into memory and run Javascripts from around the web. At least with a commandline web-capable JS runtime monstrosity the user could in theory exercise more control over what scripts are downloaded and if and when to run them. Perhaps more user control over permissions to access system resources as well (cf. corporate control)
1. One can already see an approach something like this being used in the case of
https://github.com/yt-dlp/yt-dlp/wiki/EJS
where a commandline JS runtime is used without the need for any graphics layer (advertising display layer)
Why do Apple, Microsoft, Google, Meta, OpenAI, AWS and other so-called "tech" companies advertise on TV
What about people who do not own a TV
Is this something I’d have to own a tv to understand?
> At the time of writing, Bun's monthly downloads grew 25% last month (October, 2025), passing 7.2 million monthly downloads. We had over 4 years of runway to figure out monetization. We didn't have to join Anthropic.
I believe this completely. They didn't have to join, which means they got a solid valuation.
> Instead of putting our users & community through "Bun, the VC-backed startups tries to figure out monetization" – thanks to Anthropic, we can skip that chapter entirely and focus on building the best JavaScript tooling.
I believe this a bit less. It'll be nice to not have some weird monetization shoved into bun, but their focus will likely shift a bit.
> They didn't have to join, which means they got a solid valuation.
Did they? I see a $7MM seed round in 2022. Now to be clear that's a great seed round and it looks like they had plenty of traction. But it's unclear to me how they were going to monetize enough to justify their $7MM investment. If they continued with the consultancy model, they would need to pay back investors from contracts they negotiate with other companies, but this is a fraught way to get early cashflow going.
Though if I'm not mistaken, Confluent did the same thing?
They had a second round that was $19m in late 2023. I don't doubt for a second that they had a long runway given the small team.
Good thing they got acquired by a company that also has a snowballs chance in hell of ever paying back their investment
I don't really know any details about this acquisition, and I assume it's the former, but acquihires are also done for other reasons than "it was the only way".
Can't edit my comment anymore but Bun posted a pretty detailed explanation of their motivation here: https://bun.com/blog/bun-joins-anthropic
Sounds like "monetizing Bun is a distraction, so we're letting a deep-pocketed buyer finance Bun moving forward".
Anthropic is still a new company and so far they seem "friendly". That being said, I still feel this can go either way.
Yep. Remember when "Open"AI took a bunch of grant money and then turned for-profit?
And kept their fraudulent name.
> I believe this a bit less.
They weren’t acquired and got paid just to build tooling as before and now completely ignoring monetization until the end of times.
Maybe they were though. Maybe Anthropic just wanted to bring a key piece of the stack in-house.
Good for them, could be bad for actual users.
Given the worries about LLM focused companies reaching profitability I have concerns that Bun's runway will be hijacked... I'd hate for them to go down with the ship when the bubble pops.
This is my fear. It's one thing to lose a major sponsor. It's another to get cut due to a focus on profitability later down the line.
At least Anthropic itself has the stated goal of creating ethical AI that benefits humanity. That’s more than can be said for any other AI companies. Time will tell though. Google‘s motto used to be “don’t be evil” and now it’s basically the opposite.
Yeah, now they are part of Anthropic, who haven't figured out monetization themselves. Shikes!
I'm a user of Bun and an Anthropic customer. Claude Code is great and it's definitely where their models shine. Outside of that Anthropic sucks,their apps and web are complete crap, borderline unusable and the models are just meh. I get it, CC's head got probably a powerplay here given his department is towing the company and his secret sauce, according to marketing from Oven, was Bun. In fact VSCode's claude backend is distributed in bun-compiled binary exe, and the guy is featured on the front page of the Bun website since at least a week or so. So they bought the kid the toy he asked for.
Anthropic needs urgently, instead, to acquire a good team behind a good chatbot and make something minimally decent. Then make their models work for everything else as well as they do with code.
> Yeah, now they are part of Anthropic, who haven't figured out monetization themselves.
Anthropic are on track to reach $9BN in annualised revenue by the end of the year, and the six-month-old Claude Code already accounts for $1BN of that.
How is their Web app any different than any other AI? I feel like it’s on par with all of them. It works great for me. Although I mostly use Claude code.
"We were maybe gonna fuck ya, buy now we promise we wont"
apart from the unfortunate typo, this is accurate.
like when a political leader says they have full faith in one of their ministers, you know said minister will be gone by next week.
I am more shocked about the origin story compared to the acquisition.
> Almost five years ago, I was building a Minecraft-y voxel game in the browser. The codebase got kind of large, and the iteration cycle time took 45 seconds to test if changes worked. Most of that time was spent waiting for the Next.js dev server to hot reload.
Why in the hell would anyone be using Next.js to make a 3D game... Jarred has always seemed pretty smart, but this makes no sense. He could've saved so much time and avoided building a whole new runtime by simply not using the completely wrong tool for the job.
Maybe same for anthropic, they can simply write agent using Rust/Go. Instead they decide to buy and develop a JavaScript runtime.
If anything this seems to be a huge victory for Zig, since Bun is mostly written in Zig.
These are completely different. Agents (aside from the model inference) are not CPU bound. You gain much more by having a wider user base than whatever marginal CPU cycles you would gain in Rust/Go.
Video games are of course a different story.
My thinking is that they’re trying to capture that market for JavaScript before another AI company does. To put it bluntly they want to capture the revenue generated by writing JavaScript code, which is currently being captured by independent JavaScript developers. The reason for a JavaScript is that is the most ubiquitous language, and id guess there are more jobs available for JS/node than any other language. Of course, as a JavaScript developer, this may just be my paranoia. <sweats profusely>
> He could've saved so much time and avoided building a whole new runtime by simply not using the completely wrong tool for the job.
True, but where is the fun in that?
Where is the fun in next.js?
I’m guessing he was probably a JavaScript developer that wanted to make a game. He began building it using what he knew and then he hit the limitations of it. Rather than switching to something else, he tried to figure out why fast compile times weren’t possible and determined that they were possible and started to build a solution for it.
This take is interesting given we're all here congratulating Jarred for seeing that there was no tool to solve x so made it, and is now enjoying a likely nice payday. Be the change you want to see in the world?
It kinda reads like a case of survivorship bias. He is the one in a million to reach the good ending, despite starting with the wrong choice; though in this case, the wrong choice brought him on the road to the good ending.
Now the real question is, does the game loads significant better now, or does the performance still suck? In which case it might be more an excessive case of yak-shaving. And if yes, when can we except the release?
First time I see it being a net positive that someone didn't know about Vite: Bun wouldn't exist otherwise.
Because he wanted to? Do you also berate the choices of people in the 4K demo scene for using too little memory?
That’s kind of the opposite though. I guess if you’re saying that there’s an art to building things using the least efficient means possible just as there’s an art to being maximally efficient (like the 4k demo scene) then your point stands.
Most people use what they know. You start out that way, and if it turns out to be good, you can always do a v2
Yes, but there are obvious limits to that. This is like someone who knows how to bake wanting to build a car, so they start making it out of dough.
I don't think his goal was to get the fastest voxel engine. Most projects just start with "That's stupid... but what if I did it anyway?"
That's super strange since React by its nature assumes that controls are stateless - which games definitely are not. If you render your game inside a canvas then React decides it wants to recreate your control, then your whole game restarts.
He may have been serving a game in a canvas hosted in a Next.js app, but have done all the actual game (rendering, simulation, etc.) in something else. That’s a decent approach - Next can handle the header of the webpage and the marketing blog or whatever just fine.
But like... so can an index.html with a script tag? Am I missing something, where did you read that there was a lot of work involving the header or an attached marketing blog?
I work on Bun.
Happy to answer any questions
I'm sort of surprised to see that you used Claude Code so much. I had a vague idea that "Zig people" were generally "Software You Can Love" or "Handmade Software Movement" types, about small programs, exquisitely hand-written, etc, etc. And I know Bun started with an extreme attention to detail around performance.
I would have thought LLM-generated code would run a bit counter to both of those. I had sort of carved the world into "vibe coders" who care about the eventual product but don't care so much about the "craft" of code, and people who get joy out of the actual process of coding and designing beautiful abstractions and data structures and all that, which I didn't really think worked with LLM code.
But I guess not, and this definitely causes me to update my understanding of what LLM-generated code can look like (in my day to day, I mostly see what I would consider as not very good code when it comes from an LLM).
Would you say your usage of Claude Code was more "around the edges", doing things like writing tests and documentation and such? Or did it actually help in real, crunchy problems in the depths of low level Zig code?
I am not your target with this question (I don't write Zig) but there is a spectrum of LLM usage for coding. It is possible to use LLMs extensively but almost never ship LLM generated code, except for tiny trivial functions. One can use them for ideation, quick research, or prototypes/starting places, and then build on that. That is how I use them, anyway
Culturally I see pure vibe coders as intersecting more with entrepreneurfluencer types who are non-technical but trying to extend their capabilities. Most technical folks I know are fairly disillusioned with pure vibe coding, but that's my corner of the world, YMMV
> I had a vague idea that "Zig people" were generally "Software You Can Love" or "Handmade Software Movement" types, about small programs, exquisitely hand-written, etc, etc.
I feel like an important step for a language is when people outside of the mainline language culture start using it in anger. In that respect, Zig has very much "made it."
That said, if I were to put on my cynical hat, I do wonder how much of that Anthropic money will be donated to the Zig Software Foundation itself. After all, throwing money at maintaining and promoting the language that powers a critical part of their infrastructure seems like a mutually beneficial arrangement.
Handmade Cities founder here.
We never associated with Bun other than extending an invitation to rent a job booth at a conference: this was years ago when I had a Twitter account, so it's fair if Jarred doesn't remember.
If Handmade Cities had the opportunity to collaborate with Bun today, we would not take it, even prior to this acquisition. HMC wants to level up systems while remaining performant, snappy and buttery smooth. Notable examples include File Pilot [0] or my own Terminal Click (still early days) [1], both coming from bootstrapped indie devs.
I'll finish with a quote from a blog post [2]:
> Serious Handmade projects, like my own Terminal Click, don’t gain from AI. It does help at the margins: I’ve delegated website work since last year, and I enjoy seamless CI/CD for my builds. This is meaningful. However, it fails at novel problems and isn’t practical for my systems programming work.
All that said, I congratulate Bun even as we disagree on philosophy. I imagine it's no small feat getting acquired!
[0] https://filepilot.tech
[1] https://terminal.click
[2] https://handmadecities.com/news/summer-update-2025/
"exquisitely hand-written"
This sounds so cringe. We are talking about computer code here lol
> I had a vague idea that "Zig people" were generally "Software You Can Love" or "Handmade Software Movement" types, about small programs, exquisitely hand-written, etc, etc.
In my experience, the extreme anti-LLM people and extreme pro-vibecoding people are a vocal online minority.
If you get away from the internet yelling match, the typical use case for LLMs is in the middle. Experienced developers use them for some small tasks and also write their own code. They know when to switch between modes and how to make the most of LLMs without deferring completely to their output.
Most of all: They don't go around yelling about their LLM use (or anti-use) because they're not interesting in the online LLM wars. They just want to build things with the tools available.
I'm not sure about exquisite and small.
Bun genuinely made me doubt my understanding of what good software engineering is. Just take a look at their code, here are a few examples:
- this hand-rolled JS parser of 24k dense, memory-unsafe lines: https://github.com/oven-sh/bun/blob/c42539b0bf5c067e3d085646... (this is a version from quite a while ago to exclude LLM impact)
- hand-rolled re-implementation of S3 directory listing that includes "parsing" XML via hard-coded substrings https://github.com/oven-sh/bun/blob/main/src/s3/list_objects...
- MIME parsing https://github.com/oven-sh/bun/blob/main/src/http/MimeType.z...
It goes completely contrary to a lot of what I think is good software engineering. There is very little reuse, everything is ad-hoc, NIH-heavy, verbose, seemingly fragile (there's a lot of memory manipulation interwoven with business logic!), with relatively few tests or assurances.
And yet it works on many levels: as a piece of software, as a project, as a business. Therefore, how can it be anything but good engineering? It fulfils its purpose.
I can also see why it's a very good fit for LLM-heavy workflows.
I love zig, in my experience claude code is extremely good with the language if you invest lots of time on design sessions, to the point where I spend >90% of my time only discussing design with claude. The fact it has easy access to sources of the whole stdlib by just downloading the zig tarball makes it really simple to have a feedback loop where it implement most of the boilerplate on its own. The quality of AI code is really something that can be well controlled with clear guidelines, strict reviews, comprehensive design sessions, and a great test infrastructure
I interviewed for the Bun guys and totally flopped because I was not prepared for the interview format. It was "here's a task, do whatever you need to including AI to get it done". From that, I'd infer that the usage is pretty substantial.
Are you at liberty to divulge how much Anthropic paid for Bun?
Thanks, Jarred. Seeing what you built with Bun has been a real inspiration, the way one focused engineer can shift an entire ecosystem. It pushed me back into caring about the lower-level side of things again, and I’m grateful for that spark. Congrats on the acquisition, and excited to see what’s next
Congrats on the payday :)
Do you think Anthropic might request you implement private APIs?
This is an interesting question; not to be too naive, but are there examples in the wild about this scenario? First I’ve heard of private APIs for something open source like this and my interest is piqued!
Is this acquihiring?
No. Anthropic need Bun to be healthy because they use it for Claude Code.
I consider this more of a strategic acquisition.
Amazing news, congrats! Been using Bun for a long while now and I love it.
Is there anything I could do to improve this PR/get a review? I understand you are def very busy right now with the acquisition, but wanted to give my PR the best shot:
https://github.com/oven-sh/bun/pull/24514
You said elsewhere that there were many suitors. What is the single most important thing about Anthropic that leads you to believe they will be dominant in the coming years?
No idea about his feelings but believing that they will be dominant wouldn't have to be the reason he chose them. I could easily imagine that someone would decide based on (1) they offered enough money and (2) values alignment.
I love Bun and use it daily, but I'm still very frustrated by all the configuration that one needs ATM when working in the js ecosystem. Do you guys see yourself integrating more and more, and moving more and more towards a "convention over configuration", to bring a more streamlined dev experience (that languages like Golang and Rust have, for example)
Why can't you make CLI autocompletions work? It's so basic, but the ticket has languished for almost as long as bun has existed!
Because nobody (including you, apparently) cares enough to implement it?
What happened to the voxel game that kickstarted the idea of bun? Was it ever finished? How much did it benefit from bun?
What are your thoughts on using AI generated cartoons as your primary marketing material on social media? For instance https://xcancel.com/bunjavascript/status/1955893818529866055...
Hi Jarred. Congratulations on the acquisition! Did (or will) your investors make any profit on what they put into Bun?
Are contributors getting cash or Anthropic equity as part of the acquisition?
on Bun's website, the runtime section features HTTP, networking, storage -- all are very web-focused. any plans to start expanding into native ML support? (e.g. GPUs, RDMA-type networking, cluster management, NFS)
Probably not. When we add new APIs in Bun, we generally base the interface off of popular existing packages. The bar is very high for a runtime to include libraries because the expectation is to support those APIs ~forever. And I can’t think of popular existing JS libraries for these things.
I've never personally used Bun. I use node.js I guess. What makes Bun fundamentally better at AI than, say, bundling a node.js app that can run anywhere?
If the answer is performance, how does Bun achieve things quicker than Node?
Easier deployment, you may generate a single binary.
What happens to Bun in a scenario where Anthropic goes under?
How much of your day-to-day is spent contributing code to the Bun codebase and do you expect it to decrease as Anthropic assigns more people to work on Bun?
Hi Jarred,
I contributed to Bun one time for SQLite. I've a question about the licensing. Will each contributor continue to retain their copyright, or will a CLA be introduced?
Thanks
With Bun's existing OSS license and contribution model, all contributors retain their copyright and Bun retains the license to use those contributions. An acquisition of this kind cannot change the terms under which prior contributions were made without explicit agreement from all contributors. If Bun did switch to a CLA in the future, just like with any OSS project, that would only impact future contributions made after that CLA went into effect and it depends entirely on the terms established in that hypothetical CLA.
Does this acquisition preclude implementing an s3 style integration for AWS bedrock? Also is IMDSv2 auth on the roadmap?
Hi Jarred, thanks for all your work on Bun.
I know that one thing you guys are working on or are at least aware of is the size of single-file executables. From a technical perspective, is there a path forward on this?
I'm not familiar with Bun's internals, but in order to get the size down, it seems like you'd have to somehow split up/modularize Bun itself and potentially JavaScriptCore as well (not sure how big the latter is). That way only the things that are actually being used by the bundled code are included in the executable.
Is this even possible? Is the difficulty on the Bun/Zig side of things, or JSC, or something else? Seems like a very interesting (and very difficult) technical problem.
Any chance there will be some kind of updating mechanism for 'compiled' bun executables?
I have a PR that’s been sitting for awhile that exposes the extra options from the renameat2 and renameatx_np syscalls which is a good way to implement self-updaters that work even when multiple processes are updating the same path on disk at the same time. These syscalls are supported on Linux & macOS but I don’t think there’s an equivalent on Windows. We use these syscalls internally for `bun install` to make adding packages into the global install cache work when multiple `bun install` processes are running simultaneously
No high-level self updater api is planned right now, but yes for at least the low level parts needed to make a good one
One more thing I hope doesn't change, is the fun Release videos :-) I really enjoy them. They're very apple-y, and for just a programming tool.
Yeah why are you not out on a boat somewhere enjoying this moment? Go have fun please.
Acq's typically have additional stips you have to follow - they probably have new deadlines and some temporary stress for the next few months.
how the helldid you got that og name here in hn
asking the real questions
"work on Bun." LOL.
Congratulations.
how can you sleep at night?
The money was too good to pass up.
my wife and i call each other bun all the time, and it's really weird to see an article full of Buns
Any thoughts on the claude "soul document" that was leaked this week?
I wonder if this is a sign of AI companies trying to pivot?
> Bun will ship faster.
That'll last until FY 2027. This is an old lie that acquirers encourage the old owner to say because they have no power to enforce it, and they didn't actually say it so they're not on the hook. It's practically a cheesy pickup line, and given the context, it kinda is.
On your first point: It doesn't read like that to me. It seems like they built one of their key products (Claude Code) on top of Bun, and want to have a say in it's development.
This is why we can't have nice things
I would like to clarify that I wish I weren't right but I probably am.
"Insanity Is Doing the Same Thing Over and Over Again and Expecting Different Results"
> Anthropic has direct incentive to keep Bun excellent.
Huh, this feels very odd to read and buying a company outright is definitely not the only way to push Bun to be excellent. Contributing to Bun from their developers, becoming a sponsor, donating through other means, buying 'consulting services' or similar, or even forking it and keeping it up to date would all be also steps towards keeping the Bun excellent.
This is vendoring a dependency on steroids, and first moment interests of community are not aligned with what Antropic needs, it will be interesting to see how this unfolds. History has thought us that this will end up with claims in the blog post not holding much weight.
since Anthropic is one of the only companies using the Bun Runtime, not just the bundler like most do, they want to make sure the runtime stays the focus. This is good for both companies and us tbh since they wont switch focus to whats popular at the moment
I find it a little sad, that there is almost no pushback on what a few people with deep pockets are trying to sell here. Normaly on HN an article on balcon gardening would be met with more critical thinking than this piece. Maybe instead of staring to the screen all day long take a break, think about what people with lots of money care about. And I don't judge, making money is nothing illegal. But Anthropic would be absolutely NOTHING without OSS. And then to see the kind of this effusive, submissive admiration and gratitude for their js wrapper thing makes me sick to my stomach.
I’ll be honest, while I have my doubts about the match of interests and cohesion between an AI company and a JS runtime company I have to say this is the single best acquisition announcement blog post I’ve seen in 20 years or so.
Very direct, very plain and detailed. They cover all the bases about the why, the how, and what to expect. I really appreciate it.
Best of luck to the team and hopefully the new home will support them well.
But how is another company that is also VC backed and losing money providing stability for Bun?
How long before we hear about “Our Amazing Journey”?
On the other hand, I would rather see someone like Bun have a successful exit where the founders seem to have started out with a passion project, got funding, built something out they were excited about and then exit than yet another AI company by non technical founders who were built with the sole purpose of getting funding and then exit.
Anthropic may be losing money, but a company with $7bn revenue run rate (https://www.anthropic.com/news/statement-dario-amodei-americ...) is a whole lot healthier than a company with a revenue of 0.
Often it happens that VCs buy out companies from funds belonging to a fresh because the selling fund wants to show performance to their investors until "the big one", or move cash one from wealthy pocket to another one.
"You buy me this, next time I save you on that", etc...
"Raised $19 million Series A led by Khosla Ventures + $7 million"
"Today, Bun makes $0 in revenue."
Everything is almost public domain (MIT) and can be forked without paying a single dollar.
Questionable to claim that the technology is the real reason this was bought.
The real risk is not that Anthropic will run out of money, but that they will change their strategy to something that isn't Bun-based, and supporting Bun won't make sense for them any more.
> But how is another company that is also VC backed and losing money providing stability for Bun?
Reminds me of when Tron, the crypto company, bought BitTorrent.
I misread Amazon, implying that Amazon might buy Anthropic, and I think that's what will end up happening.
Ditto, and I got to know Bun via HN. It seemed intriguing, but also "why another JS runtime" etc.
If Bun embraces the sweet spot around edge computing, modern JS/TS and AI services, I think their future ahead looks bright.
Bun seems more alive than Deno, FWIW.
I admit, it is a good acquisition announcement. I can’t remember the last acquisition announcement that was kept for more than 1-2 years. Leadership changes, priorities shift…
One thing I like about this, despite it meaning Bun will be funded, is Anthropic is a registered public benefit corporation. While this doesn't mean Anthropic cant fuck over the users of Bun, it at least puts in some roadblocks. The path of least-resistance here should be to improve Bun for users, not to monetize it to the point where it's no longer valuable.
> Anthropic is a registered public benefit corporation
Does that mean anything at all?
OpenAI is a public benefit corporation.
I had the same impression: bottom line up front, didn’t bury the lede, no weasel language.
I wonder what this means for Deno.
Will this make it more or less likely for people to use Bun vs Deno?
And now that Bun doesn't need to run a profitable cloud company will they move faster and get ahead of Deno?
Bun and Deno's goals seem quite different, I don't expect that to change. Bun is a one stop shop with an ever increasing number of built-in high-level APIs. Deno is focused on low level APIs, security, and building out a standard lib/ecosystem that (mostly) supports all JS environments.
People who like Bun for what it is are probably still going to, and same goes for Deno.
That being said I don't see how Anthropic is really adding long term stability to Bun.
I think Deno's management have been somewhat distracted by their ongoing lawsuits with Oracle over the release of the Javascript trademark.
I started out with Deno and when I discovered Bun, I pivoted. Personally I don't need the NodeJS/NPM compatability. Wish there was a Bun-lite which was freed of the backward compatability.
Ironically, this was early Deno - but then adoption required backwards compatibility.
I'm in a similar position.
I use Hono, Zod, and Drizzle which AFAIK don't need Node compat.
IIRC I've only used Node compat once to delete a folder recursively with rm.
In regards to Deno, to me that means their business is not really flying and they need this kind of distractions instead.
Amount of people at big corps that care about their lawsuit, and would switch their IT guidelines from node to Deno due to such heroic efforts?
Zero.
What do you dislike about having node compatibility?
> Will this make it more or less likely for people to use Bun vs Deno?
I'm not sure it will make much of a difference in the short term.
For those who were drawn to Bun by hype and/or some concerns around speed, they will continue to use Bun.
For me personally, I will continue to use Node for legacy projects and will continue using Deno for current projects.
I'm not interested in Bun for it's hype (since hype is fleeting). I have a reserved interested in Bun's approach to speed but I don't see it being a significant factor since most JS speed concerns come from downloading dependencies (which is a once-off operation) and terrible JS framework practices (which aren't resolved by changing engines anyway).
----------------------------
The two largest problems I see in JS are:
1. Terrible security practices
2. A lack of a standard library which pushes people into dependency hell
Deno fixes both of those problems with a proper permission model and a standard library.
----------------------------
> And now that Bun doesn't need to run a profitable cloud company will they move faster and get ahead of Deno?
I think any predictions between 1-10 years are going to be a little too chaotic. It all depends on how the AI bubble goes away.
But after 10 years, I can see runtimes switching from their current engines to one based on Boa, Kiesel or something similar.
> Deno fixes both of those problems with a proper permission model and a standard library
Bun has a better standard library than Deno. You get a DB driver, S3 client, etc which on Deno are all third party deps. It was the main reason I got interested in Bun. The speed is nice though during dev. Everything feels instant.
Prediction Bun is absorbed in house and used by Anthropic to have faster/cheaper places for Claude to run code.
It fades away as a direct to developer tool.
This is a good thing for Deno.
Deno is dead. Seems like there haven't been very relevant or user-informed changes on their roadmap for year(s) now.
> Deno is dead.
Not yet; similar concerns were addressed by Dahl 6mo ago: https://deno.com/blog/greatly-exaggerated / https://archive.vn/L6His
My first thought went to how openai used Rust to build their CLI tool and Anthropic's CEO bought influence over Zig as a reaction.
Jarred just tweeted a few days ago about how little influence over zig he has, funnily enough.
https://x.com/jarredsumner/status/1994950394955665486?s=20
That would require them to hire/buy Zig team. Which is not the case.
> bought influence over Zig as a reaction
Elaborate? I believe Zig's donors don't get any influence and decision making power.
As someone who have been using Deno for the last few years, is there anything that Bun does better? Bun seems to use a different runtime (JSC) which is less tested than V8, which makes me assume it might perform worse in real-world tasks (maybe not anymore?). The last time I checked Bun's source code, it was... quite messy and spaghetti-like, plus Zig doesn't really offer many safety features, so it's not that hard to write incorrect code. Zig does force some safety with ReleaseSafe IIRC, but it's still not the same as even modern C++, let alone Rust.
I'll admit I'm somewhat biased against Bun, but I'm honestly interested in knowing why people prefer Bun over Deno.
I haven't used Deno, but I do use Bun purely as a replacement for npm. It does the hard-linking thing that seems to be increasingly common for package managers these days (i.e. it populates your local node_modules with a bunch of hard links to its systemwide cache), which makes it vastly quicker and more disk-efficient than npm for most usage.
Even with a cold cache, `bun install` with a large-ish dependency graph is significantly faster than `npm install` in my experience.
I don't know if Deno does that, but some googling for "deno install performance vs npm install" doesn't turn up much, so I suspect not?
As a runtime, though, I have no opinion. I did test it against Node, but for my use case (build tooling for web projects) it didn't make a noticeable difference, so I decided to stick with Node.
Deno does all that. Hell, yarn does too, or pnpm as the sibling mentioned.
Deno does that. It also refrains from keeping a local node_modules at all until/unless you explicitly ask it to for whatever compatibility reason. There are plugins to things like esbuild to use the Deno resolver and not need a node_modules at all (if you aren't also using the Deno-provided bundler for whatever reason such as it disappeared for a couple versions and is still marked "experimental").
pnpm does all that on top of node. Also disables postinstall scripts by default, making the recent security incidents we've seen a non-issue.
IIRC bun zig code base has a lot of fine optimization too. I think the lead did a conference explaining his work. Or maybe i'm confused.
I decided to stick with Node in general. I don't see any compelling reason to change it.
Faster install and less disk space due to hardlink? Not really all that important to me. Npm comes with a cache too, and I have the disk space. I don't need it to be faster.
With the old-school setup I can easily manually edit something in node_modules to quickly test a change.
No more node_modules? It was a cool idea when yarn 2 initially implemented it, but at the end of the day I prefer things to just work rather than debug what is and isn't broken by the new resolver. At the time my DevOps team also wasn't too excited about me proposing to put the dependencies into git for the zero-install.
Search for pointer exceptions or core dumps on Bun's GitHub issues and you'll see why people (should) use Deno over Bun, if only because Rust is a way more safe language than Zig.
This is a non sequitur. Both Rust and Zig and any other language has the ability to end in an exception state. Whether it be kernel exception, pointer exception, or Rust's panic! - these things exist.
The reason why you see so many GitHub issues about it is because that's where the development is. Deno is great. Bun is great. These two things can both be great and we don't have to choose sides. Deno has it's use case. Bun has it's. Deno want's to be secure and require permissions. Bun just wants to make clean, simple, projects. This fight between Rust vs The World is getting old. Rust isn't any "safer" when Deno can panic too.
I haven't verified this, but I would be willing to bet that most of Bun's issues here have more to do with interfacing with JavaScriptCore through the C FFI than Zig itself. this is as much a problem in Rust as it is in Zig. in fact, it has been argued that writing unsafe Zig is safer than writing unsafe Rust: https://zackoverflow.dev/writing/unsafe-rust-vs-zig/
Easily bundling and serving frontend code from your backend code is very appealing: https://bun.com/docs/bundler/fullstack
Despite the page title being "Fullstack dev server", it's also useful in production (Ctrl-F "Production Mode").
I tried several times to port Node projects to Deno. Each time compatibility had "improved" but I still didn't have a working build after a few days of effort.
I don't know how Deno is today. I switched to Bun and porting went a lot smoother.
Philosophically, I like that Bun sees Node compatibility as an obvious top priority. Deno sees it as a grudging necessity after losing the fight to do things differently.
Which makes sense given that a big impetus for Deno's existence was the creator of Node/Deno (Ryan Dahl) wanting to correct things he viewed as design mistakes in Node.
> Bun seems to use a different runtime (JSC) which is less tested than V8, which makes me assume it might perform worse in real-world tasks (maybe not anymore?).
JSC is still the JS engine for WebKit-based browsers, especially Safari, and per Apple App Store regulations the only JS engine supposedly allowable in all of iOS.
It's more "mature" than V8 in terms of predating it. (V8 was not a fork of it and was started from scratch, but V8 was designed to replace it in the Blink fork from WebKit.)
It has different performance goals and performance characteristics, but "less tested" seems uncharitable and it is certainly used in plenty of "real-world tasks" daily in iOS and macOS.
My team has been using it in prod for about a year now. There were some minor bugs in the runtime's implementation of buffers in 1.22 (?), but that was about the only issue we ran into.
The nice things:
1. It's fast.
2. The standard library is great. (This may be less of an advantage over Deno.)
3. There's a ton of momentum behind it.
4. It's closer to Node.js than Deno is, at least last I tried. There were a bunch of little Node <> Deno papercuts. For example, Deno wanted .ts extensions on all imports.
5. I don't have to think about JSR.
The warts:
1. The package manager has some issues that make it hard for us to use. I've forgotten why now, but this in particular bit us in the ass: https://github.com/oven-sh/bun/issues/6608. We use PNPM and are very happy with it, even if it's not as fast as Bun's package manager.
Overall, Deno felt to me like they were building a parallel ecosystem that I don't have a ton of conviction in, while Bun feels focused on meeting me where I am.
I’ve been using Deno too. Although npm support has improved and it’s fine for me, I think Deno has more of a “rewrite the world” philosophy. For example, they created their own package registry [1] and their own web framework [2]. Bun seems much more focused on preexisting JavaScript projects.
[1] https://jsr.io/ [2] https://fresh.deno.dev/
It's interesting that people have directly opposite opinions on whether Deno or Bun are meant to be used with the existing ecosystem - https://news.ycombinator.com/item?id=46125049
[dead]
It has wayyyyy better nodejs compatibility (day 1 goal)
As far as I know, modern Node compat in Deno is also quite great - I just import packages via 'npm:package' and they work, even install scripts work. Although I remember that in the past Deno's Node compat was worse, yes.
Pretty sure one of the Deno day 1 goals was to correct mistakes made during the early days of Node.js.
I had memory leaks in bun and not in deno or node for the same code. ymmv
I really want to like Deno and will likely try it again, but last time I did it was just a bit of a pain anytime I wanted to use something built for npm (which is most packages out there), whereas bun didn't have that problem.
There's certainly an argument to be made that, like any good tool, you have to learn Deno and can't fall back on just reusing node knowledge, and I'd absolutely agree with that, but in that case I wanted to learn the package, not the package manager.
Edit: Also it has a nice standard library, not a huge win because that stuff is also doable in Deno, but again, its just a bit less painless
Looking at Bun's website (the comparison table under "What's different about Bun?") and what people have said here, the only significant benefit of Bun over Node.js seems to be that it's more batteries-included - a bigger standard library, more tools, some convenience features like compiling JSX and stripping TypeScript types on-the-fly, etc.
It's not clear to me why that requires creating a whole new runtime, or why they made the decisions they did, like choosing JSC instead of V8, or using a pre-1.0 language like Zig.
It just works. Whatever JavaScript/TypeScript file or dependencies I throw at it, it will run it without needing to figure out CJS or ESM, tsconfig, etc.
I haven't had that experience with deno (or node)
Same. I had a little library I wrote to wrap indexedDB and deno wouldn't even compile it because it referenced those browser apis. I'm sure it's a simple flag or config file property, or x, or y, or z, but the simple fact is, bun didn't fail to compile.
Between that and the discord, I have gotten the distinct impression that deno is for "server javascript" first, rather than just "javascript" first. Which is understandable, but not very catering to me, a frontend-first dev.
Crash. According to my experience trying it many times oves the past years.
It feels like a very unfocused project, every few months they introduce a new feature that is to replace an entire class of tools, while the original promise of "drop in Node replacement" was never fulfilled (or at least, that was the vibe for the past years when I was still paying attention).
We'll see how this works out but speed + lack of scope never works out well in the long term.
I've been using Bun since 2022 just to be trendy for recruitment (it worked, and still works despite it almost being 2026)
Bun is fast, and its worked as a drop in replacement for npm in large legacy projects too.
I only ever encountered one issue, which was pretty dumb, Amazon's CDK has hardcoded references to various package manager's lock files, and Bun wasn't one of them
https://github.com/aws/aws-cdk/issues/31753
This wasn't fixed till the end of 2024 and as you can see, only accidentally merged in but tolerated. It was promptly broken by a bun breaking change
https://github.com/aws/aws-cdk/issues/33464
but don't let Amazon's own incompetency be the confirmation bias you were looking for about using a different package manager in production
you can use SST to deploy cloud resources on AWS and any cloud, and that package works with bun
At this stage I don't think either is better over the other. Deno has inexplicable high memory usage issues in Linux containers. Bun more or less suffers from the same with an added dose of segfaults.
1. https://github.com/denoland/deno/issues?q=is%3Aissue%20state... 2. https://github.com/oven-sh/bun/issues?q=is%3Aissue%20state%3...
Node.js is a no-brainer for anyone shipping a TS/JS backend. I'd rather deal with poor DX and slightly worse performance than risk fighting runtime related issues on deployment.
Linux needs to be a first class citizen for any runtime/langauge toolchain.
Is JSC less tested? I thought it was used in Safari, which has some market share.
I used bun briefly to run the output of my compiler, because it was the only javascript runtime that did tail calls. But I eventually added a tail call transform to my compiler and switched to node, which runs 40% faster for my test case (the compiler building itself).
I've found it to be at least twice as fast with practically no compat issues.
Twice as fast at executing JavaScript? There's absolutely zero chance this is true. A JavaScript engine that's twice as fast as V8 in general doesn't exist. There may be 5 or 10 percent difference, but nothing really meaningful.
Agreed, the language would be interesting during the 1990's, nowadays not so much.
The tools that the language offers to handle use after free is hardly any different from using Purify, Insure++ back in 2000.
I find comments like this fascinating, because you're implicitly evaluating a counterfactual where Bun was built with Rust (or some other "interesting" language). Maybe Bun would be better if it were built in Rust. But maybe it would have been slower (either at runtime or development speed) and not gotten far enough along to be acquired by one of the hottest companies in the world. There's no way to know. Why did Anthropic choose Bun instead of Deno, if Deno is written in a better language?
> I'll admit I'm somewhat biased against Bun?
Why? Genuine question, sorry if it was said/implied in your original message and I missed it.
Good question, hard to say, but I think it's mainly because of Zig. At its core Zig is marketed as a competitor to C, not C++/Rust/etc, which makes me think it's harder to write working code that won't leak or crash than in other languages. Zig embraces manual memory management as well.
I mean, they said they looked at the source code and thought it was gross, so there’s a justification for their concern, at least.
I always figured Bun was the "enterprise software" choice, where you'd want to use Bun tools and libraries for everything and not need to bring in much from the broader NPM library ecosystem.
Deno seems like the better replacement for Node, but it'd still be at risk of NPM supply chain attacks which seems to be the greater concern for companies these days.
If you want to download open source libraries to be used in your Bun project then they will come from npm, at least by default. [1].
So it seems odd to say that Bun is less dependent on the npm library ecosystem.
[1] It’s possible to use jsr.io instead: https://jsr.io/docs/using-packages
Stopped following Deno while they were rejecting the need for a package management solution. Used Bun instead.
Isn’t because packages are one of the problems deno tried to fix?
Is it just me, but I don't find npm that slow? Sure it's not a speed demon, but I rarely need to do npm install anyways so it's not a bottleneck for me.
For deploy, usually running the attached terraform script takes more time.
So while a speed increase is welcome, but I don't feel it gives me such a boost.
The speed shows up for large projects. Especially if you end up with multiple node_modules directories in your dev sandbox.
> is there anything that Bun does better?
Telling prospective employees that if you're not ready to work 60-hour weeks, then what the fuck are you doing here? for one.
> Zig does force some safety with ReleaseSafe IIRC
which Bun doesn't use, choosing to go with `ReleaseFast` instead.
This acquisition makes no sense.
Investors must be happy because Bun never had to find out how to become profitable.
It’s enough Anthropic finds it profitable to run Claude Code on it.
Hard to say it makes no sense when you don't know how much they were acquired for. I would guess it is a trivial amount relative to Anthropic's war chest.
> This acquisition makes no sense.
except this sense:
> Investors must be happy because Bun never had to find out how to become profitable.
But what is the upside for anthropic?
From the comments here it sounds like most people think the amount Anthropic paid for the company was probably not much more than the VC funding which Bun raised.
How would the payout split work? It wouldn’t seem fair to the investors if the founder profited X million while the investors get their original money returned. I understand VC has the expectation that 99 out of 100 of investments will net them no money. But what happens in the cases where money is made, it just isn’t profitable for the VC firm.
What’s to stop everyone from doing this? Besides integrity, why shouldn’t every founder just cash out when the payout is life-changing?
Is there usually some clause in the agreements like “if you do not return X% profit, the founder forfeits his or her equity back to the shareholders”?
All VC's have preferred shares, meaning in case of liquation like now, they get their investment back, and then the remainder gets shared.
Additionally, depending on round, they also have multiples, like 2x meaning they get at least 2x their investment before anyone else gets anything
Probably not much more than their valuation, which is the key difference since the investor will still get a net return.
Anthropic has been trying to win the developer marketshare, and has been quite successful with Claude Code. While I understand the argument that this acquisition is to protect their usage in CC or even just to acquire the team, I do hope that part of their goal is to use this to strengthen their brand. Being good stewards of open source projects is a huge part of how positively I view a company.
> Being good stewards of open source projects is a huge part of how positively I view a company.
Maybe an easier first step would be to open source Claude Code...?
I think because their models are open (e.g. CC can send any instruction and it’ll use your max plan), they need to keep the code obfuscated to prevent people from sending everybody and their mother through that API.
Codex has the opposite issue. It has an open client, which is relatively pointless, because it will accept only one system prompt and one prompt only.
What is the business model behind open source projects like bun? How can a company "aquire" it and why does it do that?
In the article they write about the early days
Why do investors invest into people who build something that they give away for free?The post mentions why - Bun eventually wanted to provide some sort of cloud-hosting saas product.
Everyone could offer a cloud-hosted saas product that involves bun, right?
Why invest into a company that has the additional burden of developing bun, why not in a company that does only the hosting?
Except Amazon would beat them to it
Free now isn't free forever. If something has inherent value then folks will be willing to pay for it.
Well, if they suddenly changed the license, we'd get a new Redis --> Valkey situation. Or even more recently, look at minio no longer maintaining their core open source project!
I mean if you're getting X number of users per day and you don't need to pay for bandwidth or anything, there's gotta be SOME way to monetize down the line.
If your userbase or the current CEO likes it or not.
Ads. Have you seen the dotenv JavaScript package?
Either for a modest return when it sells or as a tax write off when it fails.
VCs do not invest for a modest return.
I've seen a few of these seemingly random acquisitions lately, and I congratulate the companies and individuals that are acquired during this gold rush, but it definitely feels awkwardly artificial.
Quote from the CEO of Anthropic in March 2025: "I think we'll be there in three to six months where AI is writing 90% of the code and then in 12 months we may be in a world where AI is writing essentially all of the code"
Why didn't they just use AI to write their own Bun instead of wasting 8-9 figures on this company? Makes no sense.
From the article, Claude Code is being used extensively to develop Bun already.
> Over the last several months, the GitHub username with the most merged PRs in Bun's repo is now a Claude Code bot. We have it set up in our internal Discord and we mostly use it to help fix bugs. It opens PRs with tests that fail in the earlier system-installed version of Bun before the fix and pass in the fixed debug build of Bun. It responds to review comments. It does the whole thing.
You do still need people to make all the decisions about how Bun is developed, and to use Claude Code.
"Wasting" is doing a lot of work in that sentence.
They're effectively bringing on a team that's been focused on building a runtime for years. The models they could throw at the problem can't be tapped on the shoulder, and there's no guarantee they'd do a better job at building something like Bun.
Because 90% is not 100%.
Deciding what to Implement
and
Implementing the Decisions
are complementary, one of these is being commoditised.
And, in fact, decimated.
Personally I am benefitting almost beyond measure because I can spend my time as the architect rather than the builder.
I think this wound up being close enough to true, it's just that it actually says less than what people assumed at the time.
It's basically the Jevons paradox for code. The price of lines of code (in human engineer-hours) has decreased a lot, so there is a bunch of code that is now economically justifiable which wouldn't have been written before. For example, I can prompt several ad-hoc benchmarking scripts in 1-2 minutes to troubleshoot an issue which might have taken 10-20 minutes each by myself, allowing me to investigate many performance angles. Not everything gets committed to source control.
Put another way, at least in my workflow and at my workplace, the volume of code has increased, and most of that increase comes from new code that would not have been written if not for AI, and a smaller portion is code that I would have written before AI but now let the AI write so I can focus on harder tasks. Of course, it's uneven penetration, AI helps more with tasks that are well-described in the training set (webapps, data science, Linux admin...) compared to e.g. issues arising from quirky internal architecture, Rust, etc.
That's ridiculous. Not it isn't even close.
Maybe he was correct in the extremely literal sense of AI producing more new lines of code than humans, because AI is no doubt very good at producing huge volumes of Stuff very quickly, but how much of that Stuff actually justifies its existence is another question entirely.
Why do people always stop this quote at the breath? The rest of it says that he still thinks they need tech employees.
> .... and in 12 months, we might be in a world where the ai is writing essentially all of the code. But the programmer still needs to specify what are the conditions of what you're doing. What is the overall design decision. How we collaborate with other code that has been written. How do we have some common sense with whether this is a secure design or an insecure design. So as long as there are these small pieces that a programmer has to do, then I think human productivity will actually be enhanced
(He then said it would continue improving, but this was not in the 12 month prediction.)
Source interview: https://www.youtube.com/live/esCSpbDPJik?si=kYt9oSD5bZxNE-Mn
I actually like claude code, but that was always a risky thing to say (actually I recall him saying their software is 90% AI produced) considering their cli tool is literally infested with bugs. (Or it least it was last time I used it heavily. Maybe they've improved it since.)
Do you have a source for the quote?
https://www.youtube.com/watch?v=9Shl1-ZJI6E
Why didn't they have the AI write a JS runtime instead of this acquisition?
The big picture of “build a runtime” is an easier idea than “what would make this runtime better and how should the parts interact”.
I'm curious what people think of quotes like these. Obviously it makes an explicit, falsifiable prediction. That prediction is false. There are so many reasons why someone could predict that it would be false. Is it just optimistic marketing speech, or do they really believe it themselves?
Accurate for me. Accurate for basically every startup from the past 12 months. Prob not for legacy codebases, though.
Given the horrible stability of Windows this year, it seems like Microsoft went all in on that
It’s writing 90% of my code now but it’s 100% reliant on me to do that effectively.
AI writes about 90% of my code.
Curious about the deal value/price — any clues whether it was just to make existing investors even (so say up to $30M) or are we talking some multiple? But if it's a multiple, even 2x sounds a bit crazy.
One option is that the current Bun shareholders didn't see a profitable future and didn't even care if they were made even and a return of the remaining cash was adequate.
Another option is that this was an equity deal where Bun shareholders believe there is still a large multiple worth up potential upside in the current Anthropic valuation.
Plus many other scenarios.
i don’t get it either - bun being the foundation of tons of AI tools is like a best possible outcome, what were they hoping for when they raised the money? Or is this just an admission of “hey, that was silly, we need to land this however we can”? Or do they share major investors and the therefore this is just a consolidation? (Edit: indeed, KP did indeed invest $100M in Anthropic this year. I’m also confused - article states Bun raised 26M but the KP seed round was 7, did they do the A too but unannounced? Notably, the seed was summer 2022 and chatgpt was Nov 30, so the world is different, did the hypothesis change?)
it boils down to - we didn't have full conviction that over the long run we will prove superior to node.js, however a.i company burning a lot of cash, has invested in us by basing their toolchain on us - so they have no option to acquire-hire us.
quite the uncharitable take.
On the opposite spectrum it's just that Claude and Bun are great technologies that joined forces.
I don't really see how Bun fits as an acquisition for an AI company. This seems more like "we have tons of capital and we want to buy something great" than "Bun is essential to our core business model".
If Anthropic wants to own code development in the future, owning the full platform (including the runtime) makes sense.
Programming languages all are a balance between performance/etc and making it easy for a human to interact with. This balance is going to shit as AI writes more code (and I assume Anthropic wants a future where humans might not even see the code, but rather an abstraction of it... after all, all code we look at is an abstraction on some level).
It does actually.
Claude Code is a 1B+ cash machine and Anthropic directly uses Bun for it.
Acquiring Bun lowers the risk of the software being unmaintained as Bun made $0 and relied on VC money.
Makes sense, but this is just another day in San Francisco of a $0 revenue startup being bought out.
Claude Code running on Bun is an obvious justification, but Buns features (high performance runtime, fast starts, native TS) are also important for training and inference. For instance, in inference you develop a logical model in code that maps to a reasoning sequence, and then execute the code to validate and refine the model, then use this to inform further reasoning. Bun, which is highly integrated and highly focused on performance, is an ideal fit for this. Having Bun in house means that you can use the feedback from all of automation driven execution of Bun to drive improvements to its core.
Looks like they are acquiring the team rather than the product
Does this acquisition mean Claude Code the CLI is more valuable than entiriety of Bun?
oh, I really dislike that. I don't want AI companies encroaching more in my development workflow. Used to really enjoy Bun, but don't want support Anthropic at all. Will switch back to another runtime.
Yeah, I really get that. I’ve been a fan of zig and bun since their inception, but, AI corp deep in the dev chain? I feel uncomfortable, because no one knows when they’ll start steering things into weird directions.
Why don't they use their self-acclaimed SE-replacing AI coding bot to fork Bun and called it AnthroBun instead of hiring actual engineers behind Bun?
Bun is pretty cool. I maintain a Node.js library and updated my Node.js engine version and my library just didn't work on the latest version... In frustration, I decided to try Bun for the first time... I had never used it before but my library worked straight away, no warnings, no errors. I have never seen that level of compatibility before when a library works better with an alternative engine than the one it was designed for.
I did end up fixing Node.js compatibility later but it was extra work. Felt like they just created busy-work. Node.js maintainers should stop deprecating perfectly good features and complicating their modules.
>If most new code is going to be written, tested, and deployed by AI agents
That perspective following “in two-three years” makes me shudder, honestly.
I use Claude Code CLI daily - it's genuinely changed how I work. The $1B number sounds crazy but honestly tracks with how good the tool is. Curious how Bun integration will show up in practice beyond the native installer.
Doesn’t sound crazy at all? My Max subscription costs me more than all the other netflix/spotify etc combined, but I pay it happily, and spotify would go before Claude does.
Anyone know how much Anthropic paid for Bun? I assume it was at least $26M, so Bun could break even and pay back its own investors, but I didn't see a number in the announcements from Anthropic or Bun.
Claude said $187M
We're meant to all be 100x more productive with Claude Code but
- Anthropic can't write its TUI app in anything else more suitable than Javascript
- They feel the need to buy a portion of their software supply chain
It's more honest than the Replicate answer but I think inevitably if you can't raise the next round and you get distracted by the shiny AI that this is the path taken by many teams. There is absolutely nothing wrong with that. There was an exuberant time when all the OSS things were getting funded, and now all AI things get funded. For many engineer founders, it's a better fit to go build deep technical stuff inside a bigger company. If I had that chance I would probably have taken it too. Good luck to the Bun team!
Genuine question: why js?
Why not something like c#: native, fast, crossplatform, strongly-typed, great tooling, supports both scripting (ie single file-based) and compiled to a binary with no dependency whatsoever (nativeAOT), great errors and error stacks, list goes on.
All great for AI to recover during its iterations of generating something useful.
Genuinely perplexed.
AI are good at JS because basically there is a ton of JS code available publicly without usage restriction: the JS code published to be executed in your browser. Most of JS code attached to web pages has no explicit license, but the implicit license is that anyone can download it and run it. Same for HTML and CSS. So using that public code to train models is a no brainer.
If I was to pick a language, I'd pick the one all developers agree is the best.
Sadly, this will be the trend with things moving forward. JS is perceived as a good language and LLMs are meant to make them even easier to write. It is not about the mertis of a language. It's about which languages LLMs are "good" at.
You could make a better argument for Go (compiles to native for multiple targets, zero actual dependencies (no need for a platform or virtual machine on the target)
Because js became an everything language that everyone can write and its the only language you ever need.
I dislike it also..
Same reason AIs also use Python and DBMSes offer JS or Py UDFs easily, interpreted languages take no build time and are more portable. JS is also very popular.
Might also be a context window thing. Idk how much boilerplate C# has, but others like Java spam it.
There’s like 100x more JS developers than C# developers. JS can also run code very quickly, where with an AOT language, you need to AOT compile it. For tool calls, eval-as-a-service, running in browser JS is far ahead of C#.
One other angle yet mentioned: JS is browser native. No matter how slow it is, browser is now the LCD. Similar server-client codebase, while ugly, is another plus.
Atwood’s Law
I thought c# was a dead language at this point?
When I saw the headline I was ready to be mad, but after reading the post, I'm cautiously on board with this.
This somewhat answers the question of "how on earth is a JS runtime company going to profit?"
Associated Anthropic post: https://www.anthropic.com/news/anthropic-acquires-bun-as-cla...
Hahaha congratulations. This is amazing. The most unlikely outcome for a devtools team. Fascinating stuff.
This is promising for Astral et al who I really like but worried about their sustainability. It does point to being as close to the user as possible mattering.
Extrapolating and wildly guessing, we could end up with using all that mostly idle CPU/RAM (the non-VRAM) on the beefy GPUs doing inference on agentic loops where the AI runs small JS scripts in a sandbox (which Bun is the best at, with its faster startup times and lower RAM use, not to mention its extensive native bindings that Node.js/V8 do not have) essentially allowing multiple turns to happen before yielding to the API caller. It would also go well with Anthropic's advanced tool use that they recently announced. This would be a big competitive advantage in the age of agents.
I almost read this as anthropic will be using our idle CPU/GPU resources for their own training tasks ;)
This decision is honestly very confusing to me as a constant user of Claude Code (I have 3 of them open at the moment.)
So many of the issues with it seem to be because ... they wrote the damn thing in JavaScript?
Claude is pretty good at a constrained task with tests -- couldn't you just port it to a different language? With Claude?
And then just ... the huge claude.json which gets written on every message, like ... SQLite exists! Please, please use it! The scrollback! The Keyboard handling! Just write a simple Rust or Go or whatever CLI app with an actual database and reasonable TUI toolkit? Why double down and buy a whole JavaScript runtime?
Ink (and modern alternatives) probably are the best TUI toolkit. If you want to write a UI that's genuinely good, you need e.g. HTML, or some way to express divs and flex box. There isn't really another way to build professional grade UIs; I love immediate mode UI for games, but the breadth of features handled by the browser UI ecosystem is astonishing. It is a genuinely hard problem.
And if you're expressing hierarchical UI, the best way to do it is HTML and CSS. It has the richest ecosystem, and it is one of the most mature technologies in existence. JS / TS are the native languages for those tools. Everything is informed by this.
Of course, there are other options. You could jam HTML and CSS into (as you mention) Rust, or C, or whatever. But then the ecosystem is extremely lacking, and you're reinventing the wheel. You could use something simpler, like QML or handrolled. But then you lose the aforementioned breadth of features and compatibilities with all the browser code ever written.
TypeScript is genuinely, for my money, the best option. The big problem is that the terminal backends aren't mature (as you said, scrollback, etc). But, given time and money, that'll get sorted out. It's much easier to fix the terminal stuff than to rewrite all of the browser.
I have to admit this was my first thought, too. I'm pretty obsessed with Claude Code, but the actual app is so incredibly poorly engineered for something that doesn't even do that much.
Rust, Go, whatever -- writing a good TUI isn't that hard of a problem. Buying an entire VC funded JS runtime company isn't how you solve it.
“Port it to a different language” a language that’s more out of distribution? Bad devex. Store data as an unreadable binary file? Bad devex.
Stay in distribution and in the wave as much as possible.
Good devex is all you need. Claude code team iterates and ships fast, and these decisions make total sense when you realize that dev velocity is the point.
Boggles the mind.
they acquihired the team and derisked their investment in building claude code on top of bun. makes sense to me.
moreover, now they can make investments in order to make it an an even more efficient and secure runtime for model workspaces.
All vendors will have to implement test time code execution, solution exploration, etc. as it's a low hanging fruit with huge gains, so I see it as a great hire. Love Bun, happy for you guys!
Do you mean train time?
Oh no ... unfortunately this likely means a Bun.AI API in my JS runtime.
I don't get it. Why would Anthropic need to own a JS runtime?
Because they have a product that makes $1bn+ a year that depends on having a good, stable, cross-platform JS runtime.
I'm wondering if Bun would be a good embedded runtime for Claude to think in. If it does sandboxing, or if they can add sandboxing, then they can standardize on a language and runtime for Claude Code and Claude Desktop and bake it into training like they do with other agentic things like tool calls. It'd be too risky to do unless they owned the runtime.
Why would Sun then Oracle own Java? Why would Microsoft own .net? Why would Apple own swift?
IOW look where the puck is going.
So many comments about reasoning here, yet none about the very obvious one, it's not stability of the infrastructure, it's future direction of a product like Claude Code. They need to know how to continue their optimisation machine to fit developers needs the best way possible (for good or for worse).
I guess we should wait for some opt-out telemetry some time soon. It'll be nothing too crazy at first, but we'll see how hungry they are for the data.
Don't they already have a ton of telemetry from Claude Code itself? I'd be shocked and expect an instant fork if Anthropic telemetry was added to Bun.
Aham, tx. Good to know - I'll switch my projects to Deno.
you know Deno is VC backed right
This explains why Claude started transpiling & running JavaScript code! Yesterday, when I asked it to generate a document for me in JavaScript, it generated the JavaScript and then ran it to generate a document. I had never actually seen it compile and run any code before. It only would ever output code and either use the shell (Claude code) to run it on my local computer or allow me to copy and paste it.
Maybe they want to catch up the steps of Antigravity.
Running code is absolutely going to happen for coding assistant.
Shopify should buy Ruby on Rails because they depends on it
didn't they try a hostile takeover of the ruby gems thing (forgot the name)?
"Node.js compatibility & replacing Node.js as the default server-side runtime for JavaScript"
Except Node's author already wrote its replacement: Deno.
Hope nobody buys Astral or Python is f*cked.
Our entire business runs on Python without a drop of Astral in the mix. No one would even notice.
Then it would probably be back to Poetry. Or some other newcomer, or maybe a fork of uv.
I don't want to even think about it. uv has been a revelation!
#1, uv is open-source and it could easily be forked and kept up to date.
#2, if you don't like uv, you can switch to something else.
uv probably has the least moat around it of anything. Truly a meritocracy: people use it because it's good, not because they're stuck with it.
Never used any of their tools.
Python is doing great, other than still doing baby steps into having a JIT in CPython.
Finally, an event capable of killing the Python demon!
Congratulations to the bun team!
There's no reason to run agents on expensive AI platforms or on GPUs - when you can have the AI create an agent in JS and thus runs with very high performance and perfect repeatability on far less expensive CPUs.
At the very least there must be some part of the agent tasks that can be run in JS, such as REST APIs, fetching web results, parsing CSV into a table, etc.
Am I missing something - I thought that GPUs are for training the weights
Being able to create an agent in any language to run on any hardware has always been possible hasn't it?
Agents already do this exact thing, except that the go-to language for Claude to write one-off scripts in is usually Python.
Considering that 1) Bun is written in Zig, 2) Zig has a strict no-AI policy [1], and 3) Bun has joined Claude, it seems that Bun and Zig are increasingly culturally apart.
[1] https://ziglang.org/code-of-conduct/#strict-no-llm-no-ai-pol...
You’re reading a code of conduct for contributing to the zig project. I don’t think everything there is guidance for everything written in zig, eg ‘English is encouraged’ is something one might not want for a project written in zig by native French-speakers, and I don’t think that’s something zig would want to suggest to them. I read the AI part is much more motivated by the asymmetries of open source project contribution than any statement about the language itself. Fly-by AI contributions are bad because they make particularly poor use of maintainer time. Similar to the rule on proposing language changes, which can suck up lots of reading/thinking/discussion time. When you have people regularly working together (eg those people in anthropic working on bun) the incentives are different because there is a higher cost to wasting your colleague’s time.
> Bun and Zig are increasingly culturally apart
That's like saying GCC and NodeJS are culturally apart, as if that has significant bearing on either?
Nothing I found says anything about Zig folks being inherently against AI. It just looks like they don’t want to deal with “AI Slop” in contributions to their project, which is very understandable.
Since when is a CLI tool like this a sufficiently demanding technical project that it needs to buy the runtime just to get sufficient support?
This just isn't the hard part of the product.
Like if I was building a Claude Code competitor and I acquired bun, I wouldn't feel like I had an advantage because I could get more support with like fs.read?
Has CC always used Bun? When it tries it out many months ago it was an npm install not bun install in their instructions (although I did use bun install myself). Just odd that if they were using bun, why the installation wasn’t specifically a “bun install” (I suppose they were trying to keep it vanilla for the npm masses?)
What matters: it's staying open source and MIT licensed. I sincerely hope it stays that way. Congrats to the Bun team on making a great tool and getting the recognition they deserve.
> Being part of Anthropic gives Bun: Long-term stability.
Let's see. I don't want to always be the downer but the AI industry is in a state of rapid flux with some very strong economic headwinds. I wouldn't confidently say that hitching your wagon to AI gives you long term stability. But as long as the rest of us keep the ability to fork an open source project I won't complain too much.
(for those who are disappointed: this is why you stick with Node. Deno and Bun are both VC funded projects, there's only one way that goes. The only question is timeline)
Nothing gives you long term stability in tech. You have to constantly work at staying stable, and it isn't always up to anything the company is in control of, no matter what ownership they have.
Owning your runtime is not about developer experience at the scale of Claude Code, it’s about your execution-surface area and the control you have over it.
Agentic systems are no longer just model-driven — they are increasingly runtime-driven through tools, sandboxes, and orchestration layers. When agents are writing code, executing tests, calling external tools, and validating outcomes, the reliability of the entire system becomes a function of the runtime and environment, not just the model.
Controlling the runtime gives Anthropic vertical control across:
- Packaging and distribution - Execution semantics - Performance characteristics - Security surface area - Operational stability
Of course, owning a JavaScript runtime does not magically make runtime deterministic. The dominant sources of variability still sit lower in the stack: OS behaviour, native dependencies, filesystem semantics, scheduling, hardware differences, and network effects. Runtime ownership is necessary, but not sufficient, for true runtime determinism.
What this does signal is a strategic shift in where value is being captured.
Model capability is no longer the only critical layer.
The execution plane is becoming just as strategic too, can see this in ChatGPT 5’s dynamic model routing capability as well as ecosystem wide Tool Calling and MCP adoption, which are all aimed at increasing LLM determinism through traditional software stacks.
Vertical integration here looks far less like a tooling move and far more like a control-plane strategy: consolidate the stack, reduce dependency entropy, and shrink the surface area where behaviour can diverge.
Intelligence may live in the model, but reliability, scalability, and trust are increasingly properties of the system that executes it.
So you're saying Anthropic is making it's own AI-based AWS, like OpenAI is trying to do AI social media?
> I started porting esbuild's JSX & TypeScript transpiler from Go to Zig
How was Go involved there before Zig?
esbuild is still a Go app today: https://github.com/evanw/esbuild
The first hints of what become Bun were when Jared experimented at porting that to Zig.
Look Bun is a great product but something hilarious about the company that is “going to replace all software developers with AI” BUYING software. You are building a product that is supposed to make software cost 0 right? Why wouldn’t you just “vibe” code yourself Bun?
Those aren't your customers. The people that want to build things with bun are. The problem with people who already know how to code is that they have opinions if they actually read the generated code. If you sell to people who don't (for whatever reason), you face less criticism.
I think you’re confused.
> going to replace all software developers with AI
No?
> building a product that is supposed to make software cost 0 right
No?
This reads more like Anthropic wanted to hire Jarred and Jarred wants to work with AI rather than build a Saas product around bun. I doubt it has anything to do with what is best for bun the project. Considering bun always seemed to value performance more than all else, the only real way for them to continue pursuing that value would be to move into the actual js engine design. This seems like a good pivot for Jarred personally and likely a loss for bun.
It doesn't read like that to me at all. This reads to me like Anthropic realizing that they have $1bn in annual revenue from Claude Code that's dependent on Bun, and acquiring Bun is a great and comparatively cheap way to remove any risk from that dependency.
Nah, it reads like the normal logic behind the consulting model for open source monetization, except that Bun was able to make it work with just one customer. Good for them, though it comes with some risks, especially when structured as an acquisition.
Congrats...
> Long-term stability. a home and resources so people can safely bet their stack on Bun.
Isn't it the opposite? Now we've tied Bun to "AI" and if the AI bubble or hype or whatever bursts or dies down it'd impact Bun.
> We had over 4 years of runway to figure out monetization. We didn't have to join Anthropic.
There's honestly a higher chance of Bun sticking out that runway than the current AI hype still being around.
Nothing against Anthropic but with the circular financing, all the debt, OpenAI's spending and over-valuations "AI" is the riskier bet than Bun and hosting.
Yeah that’s the main part that puzzled me, super happy for the team that they got a successful exit, but I wouldn’t really consider Anthropic’s situation to be stable…
Yeah, no reader of tech news will take an acquisition of a company with four years of runway as anything but decreasing the odds their product will still be around (and useful to the same audience…) in four years. Even without being tied to a company with lots of exposure to a probable bubble.
I say don't muddy the water with the public panic over "will it won't it" bubble burst predictions.
The effective demand for Opus 4.5 is bottomless; the models will only get better.
People will always want a code model as good as we have now, let alone better.
Bun securing default status in the best coding model is a win-win-win
Wondering to what degree this was done to support Anthropic’s web crawler. Would assume that having a whole JS runtime rather than just a HTTP client could be rather useful. Just hypothesising here, no clue what they use for their crawler.
So Anthropic sees its CLI (in TypeScript) as the first-class product and maybe planning to expand the claude code with more JS based agents / ecosystem? Especially owning the runtime gives a lot of control over developer experience.
Congratulations to the team. Knowing some of the folks on the Bun team I can not say I am surprised. They are the top 0,001% of engineers, writing code out of love. I’m hugely bullish on Anthropic, this is a great first acquisition.
Godspeed. Seems like a good pairing. Bun is sort of the only part of the JS ecosystem I like, and Code has become such an important tool for my work, that I think good things will come out of this match. Go Bundler as well.
I'm confused. I installed claude code with:
I thought claude code just used Nodejs? I didn't realise the recommended install used a different runtime.They switched to recommending this as the installation method back in July:
That install script gives you a single binary which is created using Bun.It is remembers to me to Arduino buy for Qualcomm. And it was not good news.
Interesting that this announcement is tied in with one for Claude Code revenue.
Feels like maybe AI companies are starting to feel the questions on their capital spending? They wanna show that this is a responsible acquisition.
I think this acquisition in reality has more to do with developer goodwill? And a little to do with the shell game of making these AI companies hard to value because they collect assets like this.
I’m curious to what the acquisition price was. Bun said they’ve raised $26 million so I’m assuming the price tag has to be a lot higher than that for investors to agree to an acquisition.
I'm only surprised that it wasn't Vercel who bought them.
Congrats. This is the first time I remember reading a genuine, authentic story about a sale. Much preferred over “this is about continuing the mission until my earn-out is complete.”
This morning I found myself muttering something I won't repeat as a reaction to Claude Code's remarkably slow startup time.
Put the Bun folks directly on that please and nothing else.
So, what if Claude Code starts using Bun in all applicable situations? If model providers train their models to use a tech stack beneficial to their business interests?
Wouldn’t it make more sense to write the same functionality using a more performant, no-gc language? Aren’t competitors praised for their CLIs being faster for that reason?
With AI tooling, we are in the era where rapid iteration on product matters more than optimal runtime performance. Given that, implementing your AI tooling in a language that maximizes engineer productivity makes sense, and I believe GC does that.
Codex is written in Rust
My long-term bet on Node being "boring" and "stable" continues to pay major dividends. So glad I never invested any time and effort on this ecosystem…
That is the way, when one is long time around, there are these alternatives coming and going, while the reference platforms keep going.
must be nice to have a 1gb node_modules folder for hello world
Bun has completely changed my outlook on the JS ecosystem. Prior to Bun, there was little focus on performance. Now the entire space rallies around it.
Congrats to Jarred and the team!
> Prior to Bun, there was little focus on performance.
This is just completely insane. We went through more than a decade of performance competition in the JS VM space, and the _only_ justification that Google had for creating V8 was performance.
> The V8 engine was first introduced by Google in 2008, coinciding with the launch of the Google Chrome web browser. At the time, web applications were becoming increasingly complex, and there was a growing need for a faster, more efficient JavaScript engine. Google recognized this need and set out to create an engine that could significantly improve JavaScript performance.
I guess this is the time we live in. Vibe-coded projects get bought by vibe-coded companies and are congratulated in vibe-coded comments.
One important original point of node was that v8 made JS very fast by compiling to machine code, plus it’s had multithreading built in for a decade.
That is the most absurd thing I've heard in 20 years. Chrome literally was launched on performance, for JS and beyond.
The reality is that the insane "JS ecosystem" will rally around whatever is the latest hotness.
> Prior to Bun, there was little focus on performance
v8 is one of the most advanced JIT runtimes in the world. A lot of people have spent a lot of time focusing on its performance.
That's because it's not written in JS at all but a compiled systems language, no wonder it's gonna be fast.
Genuine question, why acquisition when anthropic could simply sponsor, contribute and influence instead?
Acquisition seems like a large overhead and maybe a slight pivot to me.
I use bun in a project but Claude Code always uses node to run throwaway scripts. Maybe they can persuade it to use bun as part of this acquisition?
I bet CC will become a binary with bun included and it'll use it's internal JS engine to run most scripts.
Oddly I saw it try to use bun the other day, and was confused because everything in the project is in node.
I always tell it to use Bun and it works? Am I misunderstanding?
Neat. I just started using bun as my default "batteries included" JavaScript engine, so it's nice they're getting this boost.
Is Claude Code the first CLI tool to have a $1BN ARR?
I don't know for sure, but it's definitely the first tool of that value to have a persistent strobing (scroll position) bug so bad that passersby ask me if I'm okay when they see it.
Terraform gets to $600mm if you squint really hard make up stuff. Kubectl though. Whatever you want to say about kubernetes complexity, it does get a bunch of money run through it. We could also look at aws-cli, gcloud and az, and if we assign cloud budgets that get run through there, I'm sure it's in the hundreds of millions. Then there's git. Across the whole ecosystem, there's probably a cool couple billion floating through there. gh is probably much smaller. Other tools like docker and ansible come to mind, though those are not quite as popular. Cc only hits $1B ARR if you squint really hard in the first place, so I think in this handwavy realm, I'd say aws-cli comes first, then kubectl, then git, with maybe docket and terraform in the mix as well. Nonetheless, Claude is a really awesome cli tool that I use most days, I find.
This graph from the SemiAnalysis blog suggests that GitHub Copilot reached it earlier this year: https://substackcdn.com/image/fetch/$s_!BGEe!,f_auto,q_auto:...
That's good news. I hope this will encourage the industry to use the Zig language (and its creators to release version 1.0).
So, we can anticipate that the new Anthropic browser will now have the interpreter Ken Thompson previewed for us 41-odd years ago?
:(
The Bun team works hard, glad to see it pay off.
I'm sure the Bun team will get Claude Code straightened out. Weird acquisition, but TBH Anthropic needed to fill this hole.
So this is a rug pull we were afraid of? Bun got me into javascript ecosystem after years of hating on it. This sucks.
This wasn’t very high up on my list for acquisitions but props to the bun team for cashing in on the AI hype somehow!
To be honest, I never thought of Bun as something that someone would buy or invest in. What product do they sell?
Makes sense, I had idea how else the investors would have made money on a javascript bundler/jsc frontend
A single bun? Is that really newsworthy?
Oh you silly goose.
Sounds like the goal is to bundle up Bun with Claude Code insanely tightly, to the point where it doesn't matter if you have nodejs installed locally, but also they can optimize key things for Claude Code's Bun runtime as needed. It's a brilliant acquisition, and bun stays open source, which allows it to continue to grow, to Anthropics benefit and everyone else's.
A nice start would probably be for Claude Code to stop trying to use npm when it detects a bun lockfile and vice versa...
Proper tail calls for the win! Hopefully Google, now in its AI race, decides to give V8 its due.
Congratulations to Jared. He and the team are Real Ziggers. Looking forward to a faster Claude Code!
on the post they try to reassure the following question "If I bet my work project or company's tech stack on Bun, will it still be around in five or ten years?" and the thing is that we don't know if Anthropic itself will be around 5 to ten years
I love bun but for a cli tool: why they don’t write Claude Code in Go and call it a day?
First major success story for Zig language? (Not trying to diminish Bun's team success)
I'd say Ghostty is a pretty big success story as well.
Congrats to the Bun team, what a wild ride! Is that the first major zig acquisition?
Congrats Jarred and team! You have saved humanity many hours already, and I'm sure with Anthropic's backing, you will spare us many more. Farewell would-be headaches from Node & NPM tooling and waiting for builds and tests and package updates. Exciting times ahead!
Using bun on a side project reinvigorated my love of software development during a relatively dark time in my life, and part of me wonders if I would have taken the leap onto my current path if it weren't for the joy and feeling of speed that came from working with bun!
No strategic roadmap is ever going to tell you: "Build a $0-revenue JavaScript runtime and one day an AI company will acquire you"
It reminds me of hearing that music majors often do well in medical school. Want to go to medical school? Just major in music, duh.
Lots of strategists will tell you something like: "Build something that's useful and then there will be money".
That's 100% what happened to Bun. It's useful (like really useful) and now they're getting rewarded
Honestly that's probably the best play. Monetizing dev tools directly is a nightmare.
i really think this is part of the pitch deck for bun's funding. that a bigger company would acquire it for the technology. the only reason an AI company or any company for that matter would acquire it would be to:
1. acquire talent.
2. control the future roadmap of bun.
i think it's really 1.
I had the same thought when openai acquired rockset.
Well, that was the playbook in the 1999-2001 dotcom days.
why couldn't Anthropic simply use Claude Code to write Bun over the weekend??
It is open source (MIT license), Claude should have a pretty good start on it already.
Hopefully it doesn't push other LLM companies to go the same route.
It absolutely will.
Who is expects Anthropic to migrate all their code to Codeberg.
Should we be porting our Python projects over to Javascript?
That's nothing. I just bought four buns yesterday!
I finally hope Bun will start to support and work on WSL1
RIP Bun. I guess a bet on deno was the right bet.
deno is VC funded which means enshitification is expected.
It would be ironic if deno ended up having more builtin AI bloat despite Bun being the one owned by an AI company. But I wouldn't be surprised.
Looks like a good time to try learning Zig again
But will they fix command line autocompletions?
Maybe they just like to work together *shrug*.
Shouts out to the fellow who half-broke the news in this submission that was presumably killed because of the aggressive paywall: https://news.ycombinator.com/item?id=46123627
And apparently the submission's source for being the only org I can tell that anticipated this: https://www.theinformation.com/articles/anthropic-advanced-t...
Reminds me of Atlassian buying an AI browser.
What a trip. Love both, so all good I guess.
This announcement made me check in on the arbitrary code execution bug I reported that the Bun Claude bot created a PR for about 3 weeks ago:
https://github.com/oven-sh/bun/pull/24578
So far, someone from the bun team has left a bunch of comments like
> Poor quality code
...and all the tests still seem to be failing. I looked through the code that the bot had generated and to me (who to be fair is not familiar with the bun codebase) it looks like total dogshit.
But hey, maybe it'll get there eventually. I don't envy "taylordotfish" and the other bot-herders working at Oven though, and I hope they get a nice payout as part of this sale.
So you pushed a PR that breaks a bunch of tests, added a 5 layer nested if branch block that mixes concerns all over the place, then ignored the reviewer for three weeks, and you’re surprised they didn’t approve it?
Bun is such a great runtime. If you haven't tried it, try it. It's got bells and whistles.
This will make sure Bun is around for many, many, years to come. Thanks Anthropic.
Why Bun?
Easy to setup and go. bun run <something.ts>
Bells and whistles. (SQL, Router, SPA, JSX, Bundling, Binaries, Streams, Sockets, S3)
Typescript Supported. (No need to tsc, bun can transpile for you)
Binary builds. (single executables for easy deployment)
Full Node.js Support. (The whole API)
Full NPM Support. (All the packages)
Native modules. (90% and getting better thanks to Zig's interop)
S3 File / SQL Builtin. (Blazingly Fast!)
You should try it. Yes, others do these things too, but we're talking about Bun.
Its not 100% nodejs compatible. I see enough non-green dots in their own official report https://bun.com/docs/runtime/nodejs-compat
And even in packages with full support you can find many github issues that bun behaves directly which leads to some bugs.
> This will make sure Bun is around for many, many, years to come.
Well, until the bubble bursts and Anthropic fizzles out or gets acquired themselves.
Does it have permission flags yet like deno has?
It'll be around until they realize it makes 0$, and costs them millions per year in salaries/stock. then it will quietly die
Incredible news on so, so many levels!
(1) Bun is what technical startups should be. Consistently excellent decisions, hyper focused on user experience, and a truly excellent technical product.
(2) We live in a world where TUIs are causing billion dollar acquisitions. Think about that. Obviously, Bun itself is largely orthogonal to the TUIs. Just another use case. But also obviously, they wouldn't have been acquired like this without this use case.
(3) There's been questions of whether startups like Bun can exist. How will they make money? When will they have to sell out one of the three principles in (1) to do so? The answer seems to be that they don't; at least, not like we expected, and in my opinion not in a sinister way.
A sinister or corrupting sell out would be e.g. like Conan. What started as an excellent tool became a bloated, versioned mess as they were forced to implement features to support the corporate customers that sustained them.
This feels different. Of course, there will be some selling out. But largely the interests of Anthropic seem aligned with "build the best JS runtime", since Anthropic themselves must be laser focused on user experience with Claude Code. And just look at Opencode [^1] if you want to see what leaning all the way into Bun gets you. Single file binary distribution, absurdly fast, gorgeous. Their backend, OpenTUI [^2], is a large part of this, and was built in close correspondence with the Bun folks. It's not something that could exist without Bun, in my opinion.
(4) Anthropic could have certainly let Bun be a third party to which they contributed. They did not have to purchase them. But they did. There is a strange not-quite altruism in this; at worst, a casting off of the exploitation of open source we often see from the biggest companies. Things change; what seems almost altruistic now could be revealed to be sinister, or could morph into such. But for now, at least, it feels good and right.
[^1]: https://github.com/sst/opencode [^2]: https://github.com/sst/opentui
Well, Bun is MIT-licensed. So once they change the license and/or kill the project, the community can fork it easily.
The point of this deal is that they do not need to change the license. Nobody will ever pay for Bun and now they don't have to force it.
If claude code starts having ads for bun in the code it generates, I am never using it again.
To some degree have “opinionated views on tech stacks” is unavoidable in LLMs, but this seems like it moves us towards a horrible future.
Imagine if claude (or gemini) let you as a business pay to “prefer” certain tech in generated code?
Its google ads all over again.
The thing is, if they own bun, and they want people to use bun, how can they justify not preferencing it on the server side?
…and once one team does it… game on!
It just seems like a sucky future, that is now going to be unavoidable.
It makes total sense to me.
Love bun! Congratulations!
Can anyone provide some color around this: "I started porting esbuild's JSX & TypeScript transpiler from Go to Zig"? Hypothetical benefits include monolanguage for development, better interoperability with C and C++, no garbage collection, and better performance. What turned out to be realized and relevant here? Please, no speculation or language flames or wars.
Interesting. Looking through a strategic lens, I feel like this is related to the $1,000 free credit for Claude Code Web (I used a few hundred). What the heck are they aiming for? CodeAct? (https://arxiv.org/abs/2402.01030)
Curious, how did he pay the bills when spending these years developing Bun?
Bun was VC funded.
Good luck, always worried about stuff like that because it happened so many times and the product got worse eventually. At the same time, ai understand how much effort went into building something like Bun and people need to fund their life's somehow, so there's that.
okay so does that mean openai buys deno?
video covering it
https://www.youtube.com/watch?v=6hEiUq8jWIg
So will Bun devs now be obliged to stop coding and only manage ai-driven code, like Anthropic devs say they are?
Or perhaps they have in their agreement that Anthropic's own rules don't apply to them?
Serious question, in all this madness
bullish for js, bearish for python?
In other news - Amp Code is a separate company now - https://ampcode.com/news/amp-inc
who's going to buy deno ?
Wow.
> If Bun breaks, Claude Code breaks. Anthropic has direct incentive to keep Bun excellent.
and when this bubble pops down goes bun
Not really, we can just fork it?
Anthropic? The AI people?
Look, if a terminal emulator can raise $67 million by riding the AI hypewave then a Javscript runtime can do the same. Nobody ever said that AI investments and acquisitions have to make any sense.
Well this just created a lot of work for me. Everything’s turning to shit at an alarming rate.
Maybe now Claude will not assume that I use npm, and actually start using bun?
wow !
> Bun will ship faster.
What? Oh, lots of slop code?
AI slop lovers both of them.
Not to be confused with Bunn [1], the coffee maker makers.
[1] www.bunn.com
What?
Why?
Hahahahahhaahhahahahahahhahahahahahhahahaha.
Regards.
Classic - brand new blog post:
> We’re hiring engineers.
Careers page:
> Sorry, no job openings at the moment.
It's the Anthropic careers page that you're likely looking for now:
https://www.anthropic.com/jobs?team=4050633008
Maybe the engineers are Claude agents.
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why not Antrophic just fork or make a clone Bun themselves????
/s
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deno won, rust won
oh well. it was cool while it lasted! I guess I'll figure out how to make deno do what I want, now.
anthropic wont win, and will just get bought out by an ibm or oracle in the end...time to migrate from bun now
If Bun ends up at either IBM or Oracle, then it's a pretty safe platform, it could stay around for 50 years.
Well not gonna use Bun anymore I guess
Why not?
Why the hell is a CLI coding agent built in JavaScript?
It’s wild what happens when a generation of programmers doesn’t know anything except webdev. How far from grace we have fallen.
The big advantage of a language like JavaScript of Python for a CLI tool of this nature is that they naturally support adding extensions or plugins.
That's quite a bit harder if your tool is built using a compiled language like Go.