Anthropic Cowork feature creates 10GB VM bundle on macOS without warning

Hi, Felix from Anthropic here. I work on Claude Cowork and Claude Code.

Claude Cowork uses the Claude Code agent harness running inside a Linux VM (with additional sandboxing, network controls, and filesystem mounts). We run that through Apple's virtualization framework or Microsoft's Host Compute System. This buys us three things we like a lot:

(1) A computer for Claude to write software in, because so many user problems can be solved really well by first writing custom-tailored scripts against whatever task you throw at it. We'd like that computer to not be _your_ computer so that Claude is free to configure it in the moment.

(2) Hard guarantees at the boundary: Other sandboxing solutions exist, but for a few reasons, none of them satisfy as much and allow us to make similarly sound guarantees about what Claude will be able to do and not to.

(3) As a product of 1+2, more safety for non-technical users. If you're reading this, you're probably equipped to evaluate whether or not a particular script or command is safe to run - but most humans aren't, and even the ones who are so often experience "approval fatigue". Not having to ask for approval is valuable.

It's a real trade-off though and I'm thankful for any feedback, including this one. We're reading all the comments and have some ideas on how to maybe make this better - for people who don't want to use Cowork at all, who don't want it inside a VM, or who just want a little bit more control. Thank you!

It's incredible how many applications abuse disk access.

In a similar fashion, Apple Podcasts app decided to download 120GB of podcasts for random reason and never deleted them. It even showed up as "System Data" and made me look for external drive solutions.

The vibe coding giveth and the the vibe coding taketh away, blessed be the vibe coding

I guess it could warn about it but the VM sandbox is the best part of Cowork. The sandbox itself is necessary to balance the power you get with generating code (that's hidden-to-user) with the security you need for non-technical users. I'd go even further and make user grant host filesystem access only to specific folders, and warn about anything with write access: can think of lots of easy-to-use UIs for this.

Arguably, even without LLM, you too should be dev-ing inside a VM...

https://developer.hashicorp.com/vagrant is still a thing.

The market for Cowork is normals, getting to tap into a executive assistant who can code. Pros are running their consumer "claws" on a separate Mac Mini. Normals aren't going to do that, and offices aren't going to provision two machines to everyone.

The VM is an obvious answer for this early stage of scaled-up research into collaborative computing.

I believe that employees in Anthropocs use CC to develop CC now.

AI really give much user ability to develop a completed product, but the quality is decreasing. Professional developers will be in demand when the products/features become popular.

First batch of users of new products need to take more responsibility to test the product like a rats in lab

Yup it uses Apple Virtualization framework for virtualization. It makes it so I can't use the Claude Cowork within my VMs and that's when I found out it was running a VM, because it caused a nested VM error. All it does is limit functionality, add extra space and cause lag. A better sandbox environment would be Apple seatbelt, which is what OpenAI uses, but even that isn't perfect: https://news.ycombinator.com/item?id=44283454

I literally spent the last 30 mins with DaisyDisk cleaning up stuff in my laptop, I feel HN is reading my mind :)

I also noticed this 10GB VM from CoWork. And was also surprised at just how much space various things seem to use for no particular reason. There doesn't seem to be any sort of cleanup process in most apps that actually slims down their storage, judging by all the cruft.

Even Xcode. The command line tools installs and keeps around SDKs for a bunch of different OS's, even though I haven't launched Xcode in months. Or it keeps a copy of the iOS simulator even though I haven't launched one in over a year.

As much as an inconvenience this may be, this is exactly what "agents" should be doing. If your tool doesn't have a builtin sandbox that is intended to be used at all times, you're using something downright hazardous and WILL end up suffering data loss.

I imagined someone at Anthropic prompted "improve app performance", and this was the result.

On a similar tangent, but on the opposite end of the spectrum, check out this month-old discussion on HN: https://news.ycombinator.com/item?id=46772003

ChatGPT's code execution container contains 56 vCPUs!! Back then, simonw mentioned:

> It appears to have 4GB of RAM and 56 (!?) CPU cores https://chatgpt.com/share/6977e1f8-0f94-8006-9973-e9fab6d244...

I'm seeing something similar on a free account too: https://chatgpt.com/share/69a5bbc8-7110-8005-8622-682d5943dc...

On my paid account, I was able to verify this. I was also able to get a CPU-bound workload running on all cores. Interestingly, it was not able to fully saturate them, though - despite trying for 20-odd minutes. I asked it to test with stress-ng, but it looks like it had no outbound connectivity to install the tool: https://chatgpt.com/share/69a5c698-28bc-8005-96b6-9c089b0cc5...

Anyways, that's a lot of compute. Not quite sure why its necessary for a plus account. Would love to get some thoughts on this?

Sure it uses a few GB just like everything else these days, but some of the comments also mention it being slow?

Ok, so a lot of this boils down to the fact that this sort of software really wants to be running on linux. For both windows and mac, the only way to (really) do that is creating a VM.

It seems to me that the main issue here is painful disconnects between the VM and the host system. The kernel in the VM wants to manage memory and disk usage and that management ultimately means the host needs to grant the guest OS large blocks of disk and memory.

Is anyone thinking about or working on narrowing that requirement? Like, I may want the 99% of what a VM does, but I really want my host system to ultimately manage both memory and disk. I'd love it if in the linux VM I had a bridge for file IO which interacted directly with the host file system and a bridge in the memory management system which ultimately called the host system's memory allocation API directly and disabled the kernels memory management system.

containers and cgroups are basically how linux does this. But that's a pretty big surface area that I doubt any non-linux system could adopt.

I see this as a feature. The cost of isolation

macbook pro m4 bought last year. worked on so many codes and projects. never hot after closing lid. installed electron claude. closed lid and went to sleep and woke up to macbook that has been hot all night. uninstall claude. problem went away.

i kept telling myself this BUT NEVER ELECTRON AGAIN.

In the meantime, I deleted the virtual machine and the Claude application. I simply created a web app through Safari. It works very well.

I really love Anthropic's models, but, every single product/feature I've used other than the Claude Code CLI has been terrible... The CLI just "sticked" for me and I've never needed (or arguably looked in depth) any other features. This for my professional dayjob.

For personal use, where I have a Pro subscription and adventure into exploring all the other features/products they have... I mean, the experience outside of Claude Code and the terminal has been... bad.

A better UX would be to prompt the user, asking "Would you like to use the app in a sandbox for enhanced safety?" and only then download the Ubuntu linux image used in the VM

Aren't most these people recommending random tools in the github chat for this entry just attempting to exploit naive users? Why would anyone in this day and age follow advice of new users to download new repos or click at random websites when they already attempt to use claude code or cowork?

Same thing on Windows. The VM bundle is at %AppData%\Claude\vm_bundles

Way slower, but way better than chat mode. Nothing beats Claude Code CLI imo.

This GitHub issue itself is clearly AI slop. If you’ve been dealing with GitHub issues in the past months it will be obvious, but it’s confirmed at the end:

> Filed via Claude Code

I assume part of it is true, but determining which part is true is the hard part. I’ve lost a lot of time chasing AI-written bug reports that were actually something else wrong with the user’s computer. I’m assuming the claims of “75% faster” and other numbers are just AI junk, but at least someone could verify if the 10GB VM exists.

Yeah, that's why I do not install these tools on my personal devices anymore and instead play with them on a VPS.

Try this if you have claude code -- ls -a your home dir and see all the garbage claude creates.

Mac Problems...

so crazy on a windows desktop I at most complain if it is hardcoded to the system drive (looking at you ollama)

This is exactly the kind of issues we will see more and more frequently with vibe-coding.

The amount of bad things this companies software does is staggering. The models are amazing, the code sucks.

Hey, they did admit that they vibed this in a week and released it to everyone.

That seems somewhat reasonable.

Storage should be cheaper, complain about Apple making you pay a premium.

Its just another example and just a detail in the broader story: We cannot trust any model provider with any tooling or other non model layer on our machines or our servers. No browsers, no cli, no apps no whatever. There may not be alternatives to frontier models yet, but everything else we need to own as true open source trustable layer that works in our interest. This is the battle we can win.

What's funny is interacting with it in claude code. Claude-desktop-cowork can't do anything about the VM. It creates this 10 GiB VM, but the disk image starts off with something like 6-7 GiB full already, which means any of the cowork stuff you try to do has to fit into the remaining couple of gigs. It's possible to fill it up, and then claude cowork stops working. Because the disk is full. Claude cowork isn't able to fix this problem. It can't even run basic shell commands in the VM, and Opus4.6 is able to tell the user that, but isn't smart enough/empowered to do anything about it.

So contrary to the github issue, my problem is that it's not enough space. So the fix is to navigate to ~/Library/Application\ Support/Claude/vm_bundles, and then ask Claude Code to upsize the disk to a sparse 60 GiB file, giving cowork much more space to work in while not immediately taking up 60 GiB.

Bigger picture, what this teaches me though, is that my knowledge is still useful in guiding the AI to be able to do things, so I'm not obsolete yet!

Are we sure that this isn't a sparse image? It will report as the full size in finder, but it won't actually be consuming that much space if it's a sparse image

Just write a Claude OS already.

All code in Claude™ is written by Claude™

Also apparently eating 2 GB RAM or so to run an entire virtual machine even if you've disabled Cowork. Not sure which of this is worse. Absolute garbage.

The software seems to get into more and more and communicate about what it's doing less and less. That's the crux.

Pondering... Noodling... Some other nonsense...

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labelled "high priority" a month ago. No actual activity by Anthropic despite it being their repo. I'm starting to get the feeling they're not actually very good at this?