Jesse Josiah

stackshift.cloud StackShift Computers: engineering notes | StackShift How a StackShift Computer works: one Firecracker microVM per machine, warm starts in under a second, computer use for agents, CI runners and pricing.

Jesse Josiah @_fusionTech · 5h

We're launching StackShift Computers: a whole Linux machine for every AI agent.

Root, Docker and a desktop with Chromium. Ready in under a second, pauses with memory kept, forks mid-task. Watch it work, take over any time.

npx stackshift@latest sh

stackshift.cloud/computers

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Larsen Cundric Verified account @larsencc · 2d

I was wrong about agent sandboxes.

In my article I said pattern 1, where the agent runs on your infra and only calls a sandbox for tools, doesn't work at scale. I moved everything to pattern 2 and put the whole agent inside a VM.

At the time that made sense but today I'd pick pattern 1.

For your own personal agent, a coding agent, or a small project, isolating the whole agent in a VM is still a great default. I would keep doing it.

At real multi-tenant scale it falls apart.

There will be more agents than humans. Every human gets one computer. Giving every agent its own VM running 24/7 means billions of CPU-hungry machines, and we're already short on compute.

Most of what an agent does doesn't need a machine at all. It thinks, calls APIs, reads pages, and waits. Nobody needs a 4 CPU VM sitting idle so an agent can run a simple JS script once an hour.

What I'd build now:
> the agent loop runs on shared infra that scales
> it gets a sandbox only when it has to run untrusted code
> sandboxes spin up in seconds and die right after
> zero state on the machine, everything lives outside it

VMs are a tool the agent calls, but they shouldn't be where it lives.

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