How it works
The model never runs code itself. It writes a command, such as "install pandas and run report.py", and sends it to the sandbox through an API. The sandbox runs the command and sends back the output. The agent reads it and picks the next step.
agent → run: pip install pandas sandbox → ok agent → run: python report.py sandbox → wrote report.csv agent → read: report.csv
This matters because agent-written code is code you did not read. A wrong command, a deleted folder or a web page that tricks the agent into something odd then hurts a throwaway computer. Your laptop, your keys and your data stay outside. Keep real secrets out of the sandbox too: isolation limits the damage, it does not remove it.
Three kinds of isolation
"Sandbox" is a goal, not a technology. Services reach it in three ways, and they trade start-up speed against how much the agent can do inside.
| Container | gVisor | microVM | |
|---|---|---|---|
| What stands between the agent and the host | Namespaces on the host's own kernel | A kernel written in user space that handles the agent's system calls | A separate guest kernel behind a hypervisor |
| Own kernel for the agent | no | no | yes |
| Who uses it | Many app platforms | Modal: gVisor by default; a full VM runtime is an option | E2B (Firecracker) and Uno |
Sandbox services and an Uno computer
Most services are built for one job: start a fresh sandbox, run something short, delete it. Limits on a session follow from that. An Uno computer is built the other way round: one machine per agent that lives for months and sleeps between jobs.
| E2B | Modal Sandboxes | Uno computer | |
|---|---|---|---|
| Longest session | 1 hour on Hobby, 24 hours on Pro | 5 minutes by default, up to 24 hours | No session time limit |
| When idle | Memory kept: paused indefinitely, $0 | Ends at its time limit; state is saved with filesystem snapshots | Asleep, memory and running programs saved |
| Back to work | Resume ~1 s | A new sandbox, from a snapshot if you made one | Median 118 ms through the console |
| Price floor | $150 a month on Pro, plus usage | Billed by usage | $5 a month on Small |
Keeping one sandbox available for a month
About 1 vCPU and 1 GB, in $ per month. The range covers the cheapest and the dearest of E2B, Morph, Fly Sprites and CodeSandbox when memory is kept.
Show as a table
| Option | $ per month | Shape |
|---|---|---|
| Uno Small | 5 | 1 vCPU · 1 GB · sleeps when idle, keeps memory |
| Sandboxes with live memory | 44–199 | E2B, Morph, Fly Sprites, CodeSandbox, kept available all month |
| E2B Pro, the monthly floor | 150 | Before any usage is added |
Do you need one?
Use a sandbox when
- The agent has a shell. It can install, delete and overwrite things, so give it a place where that is harmless.
- It runs code you did not write. Generated scripts, a stranger's repository, a downloaded tool.
- It must not touch your laptop. Your files, browser logins and SSH keys stay out of reach.
Skip it when
- The agent only talks. If it answers questions and never runs a command, nothing needs fencing in.
- You read every command first. Fine for a short task; it stops scaling after the tenth command.
- It builds a static page. A folder published to a site needs no machine at all.
Pick by how long the agent lives. Thousands of short runs a minute: a sandbox service. One agent per project, working for days and remembering its tools and logins: a computer of its own.
Where Uno is worse
- For thousands of throwaway runs a minute through an SDK, sandbox services are the better tool. Uno is built for computers that live for months.
- The smallest Uno computer is 1 vCPU and 1 GB. There are no fractions of a core.
- Our vCPU are shared, not dedicated, and there is one region for paid plans today: the Netherlands.
- We have not tested wake times side by side. Vendors quote their own; we measured ours once in production.
Your agent gets a clean address of its own
Your computer runs in the Netherlands. Its traffic can leave through a static address of a regular internet provider in one of 8 countries. Only your account works from that address.
- From a data-center address
- Sites see a server range shared with thousands of strangers. The agent's browser hits more captchas and blocks.
- From your Clean exit IP
- Sites see a regular internet provider's address in the country you picked. Fewer captchas, and less reason for Claude or ChatGPT to flag your account: nobody else works from it.
The short way: a sandbox that remembers
On Uno an agent gets a microVM with root. It keeps its tools, logins and open sessions while it sleeps, and your files in cloud storage outlive it. Create one by API or MCP.
Small: $5 a month
One agent, one computer, from $5 a month
Every plan is a Linux microVM with root and Docker. Pick the size; move up or down any time, your files come with you.
Small
A Telegram bot, a VPN, a small backend
$5/ month
- 1 vCPU · 1 GB
- 15 GB disk
- 25 GB cloud storage
- 5 boosts a month
Plus
Agents that work with your laptop closed
$20/ month
- 4 vCPU · 4 GB
- 40 GB disk
- 100 GB cloud storage
- Uno Work in the cloud
Pro
A product in production, a second MacBook
$70/ month
- 16 vCPU · 16 GB
- 120 GB disk
- 300 GB cloud storage
- Speed of a MacBook Air M4
Max
A team and many agents at once
$200/ month
- 32 vCPU · 48 GB
- 300 GB disk
- 1,024 GB cloud storage
- 5 public IPv4
Add Uno AI to any plan: 40 h of AI work a month on Small, 100 h on Plus, unlimited on Max. Today: GLM-5.3 Flash and MiMo v2.6 Pro. Or sign in with your own Claude or ChatGPT.