On Runtime, a sandbox is a remote development environment. SSH, VS Code and JetBrains connect to it through the API. It costs $0.03125 an hour at 2 vCPU and 4 GiB while you read and type. Runtime bills measured CPU. An open editor is not billed as two busy cores (pricing).
Why it matters for AI agents
When a coding agent edits and tests in a sandbox, a person often wants to open that exact machine. They read what changed, run the failing test and take over. If the agent's environment is also a remote development environment, nothing has to be copied back to a laptop for inspection. The reverse works too. An agent can be given a person's environment to finish a task in. The person's own machine never runs the agent's commands.
Remote development in facts
| Property | What it means | On Runtime |
|---|---|---|
| Editor connection | The editor's server side runs on the remote machine | VS Code Remote - SSH and JetBrains Gateway via <id>.runtime |
| Shell | A login on the remote machine | runtime sandboxes ssh <id>, as the user runtime, with sudo |
| Ports | A dev server reached from the local browser | runtime sandboxes port-forward <id> 3000, any TCP port |
| Isolation | The remote machine is not your laptop | A Firecracker microVM with its own kernel |
| Idle time | What happens while nobody types | Pause keeps files, memory and processes while you have credit |
| Always on | A machine that does not stop | persistent: true keeps a paid sandbox running until stopped |
| Base system | What is installed | Ubuntu 24.04, Python 3.12, Node.js 24, Bun, git, gcc |
VS Code describes Remote - SSH as a way to "open a remote folder on any remote machine, virtual machine, or container with a running SSH server". Its extensions run on that remote machine.
Connect your editor
Install the SSH entry once. After that, each sandbox is a host. Its host name is its id or its name:
Terminalruntime sandboxes ssh config --installruntime sandboxes ssh my-env # a shellssh my-env.runtime # plain OpenSSH, scp and rsync tooruntime sandboxes port-forward my-env 5173In VS Code, run Remote-SSH: Connect to Host and enter my-env.runtime. The
sandbox opens no port to the internet. Each connection is a WebSocket through
Runtime's API, authenticated with your key
(SSH and editors).
To create the environment in code, and find it again by name:
TypeScriptimport { Runtime } from "withruntime";const runtime = new Runtime();const env = await runtime.sandboxes.create({ name: "my-env", getOrCreate: true, idlePauseSeconds: 1800,});console.log(env.id, env.state);getOrCreate returns the sandbox that already has the name. If the sandbox was
paused, it wakes it. idlePauseSeconds pauses the sandbox after half an hour
with no request.
Keep it running while you work
An open SSH connection keeps a sandbox running. There is no time limit by
default, so a long session needs no setup. For a machine that never pauses,
even with nobody connected, create a paid sandbox with persistent: true. It
runs while credit lasts. Connecting to a paused sandbox wakes it, as any command
does.
Related
- How to give every user their own cloud dev environment
- GitHub Codespaces vs an agent sandbox
- How to pause and resume a sandbox
- SSH and editors
Sources
- VS Code: Remote Development using SSH, read 25 October 2026
Facts on this page were checked on 25 October 2026.