If the machine can fork itself, it could allow for some really neat auto-forking workflows where you fuzz the UI testing of a website by forking at every decision point. I forget the name of the recent model that used only video as its latent space to control computers and cars, but they had an impressive demo where they fuzzed a bank interface by doing this, and it ended up with an impressive number of permutations of reachable UI states.

One gap I'm noticing in these comments and in the current sandbox landscape is Windows. Every platform mentioned in these comments like E2B, Daytona, Fly Sprites, Sandflare appears Linux-native. Makes sense for coding agents targeting Debian environments, but a real category exists to automate Windows-specific workflows: enterprise software, ERP systems, anything that runs only on Windows.

If anyone wants to run agents in Mac or Linux and need to access Windows for computer use, Dexbox could be helpful. [github.com/getdexbox/dexbox]

I launched an open source developer tool called Dexbox to run agent workloads that quickly provision and run Windows desktops. It's a CLI and MCP experience that's different from Freestyle, but slightly closer to our Windows-specific production infra, Nen. I like Freestyle's cool UI that shows off the unique technical approach and developer friendliness. Nen's a bit closer to that experience.

However, 50 concurrent VMs is not a lot. Similar limits exists on all cloud providers, except perhaps in AWS where the cost is prohibitive and it is slow.

Earlier this year, we ended up rolling out own. It is nothing special. We keep X number of machines in a warm pool. Everything is backed by a cluster of firecracker vms. There is no boot time that we care about. Every new sandbox gets vm instantaneously as long as the pool is healthy.

When I’m thinking of sandboxes, I’m thinking of isolated execution environments.

What does forking sandboxes bring me? What do your sandboxes in general bring me?

Please take this in the best possible way: I’m missing a use case example that’s not abstract and/or small. What’s the end goal here(

We run upwards of a thousand sandboxes for coding agents - but these are all standard VM's that we buy off the shelf from Azure, GCP, Akamai and AWS. I am not sure why we should use this instead of the standard VM's? Pricing could be one part, but not sure if the other features resonate.

Forking is interesting, but I would need to know how it works and if it is in the blast radius of the agent execution. If we need to modify the agent to be cognizant of forking, then that is a complexity which could be very expensive to handle in terms of context. If not, then I am not sure what is the use for it.

Sandbox start time at 500ms is definitely interesting. But its something we already are on track to reproduce with a pooled batch of VM's. So not sure if that in itself is worth paying for the premium.

My two cents on the space is that agents are rapidly becoming more capable to just use the tooling developed for humans. All clouds provide a CLI which agents can already use to orchestrate - they should just use the VM's designed for humans through the CLI. Our agent can already 'login' to any VM on the cloud and use the shell exactly like a human would. No software harness is required for this capability. The agent working on a VM is indistinguishable from humans.

We ended up creating localsandbox [0] with that in mind by using AgentFS for filesystem snapshotting, but our solution is meant for a different use case than Freestyle - simpler FS + code execution for agents all done locally. Since we're not running a full OS it's much less capable but also simpler for lots of use cases where we want the agent execution to happen locally.

The ability to fork is really interesting - the main use case I could imagine is for conversations that the user forks or parallel sub-agents. Have you seen other use cases?

[0] https://github.com/coplane/localsandbox

The memory forking seems like a cool technical achievement, but I don't understand how it benefits me as a user. If I'm delegating the whole thing to the AI anyway, I care more about deterministic builds so that the AI can tackle the problem.

The cost argument for owning the hardware for this specific use case also makes sense, considering the scale these agent environments will demand. Also worth noting, sandboxes are effectively an open attack surface; architecting them not to be in your main VPC is a sound security decision from the start.

    > we mean forking the whole memory of it

So best of luck with your vision for it!

edit: just saw the pr for freestyle. something seems to be blocking, but curious how it compares: https://github.com/computesdk/benchmarks/pull/41

One thing:

>Freestyle is the only sandbox provider with built-in multi-tenant git hosting — create thousands of repos via API and pair them directly with sandboxes for seamless code management.

Maybe I’m just stupid, but I don’t know what this means. I initially thought I’m your target audience but after failing to understand this part I’m thinking maybe I’m not? I honestly don’t know.

If so, we'd very much like to test this. We make extensive use of Claude Code web but it can't effectively test our product inside the sandbox without running a K8s cluster

"Unlimited" as in 8vCPU and then I am billed for it on consumption?

We're working on a similar solution at UnixShells.com [1]. We built a VMM that forks, and boots, in < 20ms and is live, serving customers! We have a lot of great tools available, via MIT, on our github repo [2] as well!

[1] https://unixshells.com

[2] https://github.com/unixshells

Another question: How hard do you think it'll be to integrate this with something like Claude Code. ie: /resume in claude code both return your session and wake up your vm. Or even better /resume from freestyle and have your claude code session open where you left it.

Yes! And good on you, well-tuned bare metal performance is hard to beat.

Congrats on the launch. This is cool tech

> Freestyle is the only sandbox provider with built-in multi-tenant git hosting — create thousands of repos via API and pair them directly with sandboxes for seamless code management. On top of that, Freestyle VMs are full Linux virtual machines with nested virtualization, systemd, and a complete networking stack, not containers.

It makes me think of the git automation around rigs in Gas Town: https://steve-yegge.medium.com/welcome-to-gas-town-4f25ee16d...

Edit: I realize the Loom is a way to look at it. Loom interrupted me twice and I almost skipped it. However it gave me a better idea of what it does, it "invents" snapshotting and restoring of VMs in a way that appears faster. That actually makes sense and I know it isn't that hard to do with how VMs work and that it greatly benefits from having only part of the VM writable and having little memory used (maybe it has read-only memory too?).