Get started with Runtime Cloud

Paste this into your coding agent:

Move this project to Runtime Cloud: read https://withruntime.com/llms.txt and follow it.

The agent connects. If the project uses another sandbox provider, the agent moves every call to Runtime and keeps going until your real job runs there. It reports what passed, what you save each month and what is left for you to go live. You approve one link in your browser. There is nothing to copy.

In the browser: sign in and press Start a sandbox on Home. It opens with a shell running in the page, on your free hours. It pauses itself after 300 seconds with nothing happening in it.

From your code: Home offers a prompt for your coding agent. The prompt does the whole setup. Or, by hand, make your first key in one click. The key is shown once. The page then shows the install and a first sandbox in Python or JavaScript. If you signed up from a page comparing Runtime with E2B, Daytona, Vercel Sandbox or Blaxel, Home opens on that switch instead. By hand, the switch is the key, the install and the one import that changes.

Run a file, with Node 22.12 or later:

Terminalprintf '%s\n' 'print(sum([125, 250, 375]))' > invoice.pynpx withruntime sandboxes run -- python3 - < invoice.py

The first time, it connects this machine:

1. Your browser opens a Runtime page, or the command prints a link and a code.
2. You sign in with Google or by email (type the six-digit code the email gives you, or click its link if you already have an account), check the code and choose Connect agent.
3. A fresh sandbox runs the command, prints the invoice total, 750, and is deleted.

Exit code zero means the command succeeded. Nothing is left behind to pay for. npx withruntime sandboxes ls --json no longer lists the test sandbox. An older CLI only stopped it. If it is still listed, delete it with npx withruntime sandboxes rm <id>. Later commands reuse the connection.

An agent running it shows you the link and code. If you approve after the command stopped waiting (50 seconds when no one is at a terminal), the agent runs it again and it finishes, with no new link.

For several commands in one sandbox, this shell block deletes it on exit:

Terminal(  id=$(npx withruntime sandboxes create) || exit  trap 'npx withruntime sandboxes rm "${id}"' EXIT  npx withruntime sandboxes exec "${id}" -- python3 -c 'print(sum([125, 250, 375]))')

Installed with npm install --global withruntime, the command is runtime: runtime sandboxes run -- ls, runtime sandboxes create. See the CLI.

Add Runtime's MCP server to your agent with one command:

Terminalclaude mcp add --scope user runtime -- npx -y withruntime mcp   # Claude Codecodex mcp add runtime -- npx -y withruntime mcp                 # Codex

Cursor: add this to ~/.cursor/mcp.json (or .cursor/mcp.json in a project):

JSON{ "mcpServers": { "runtime": { "command": "npx", "args": ["-y", "withruntime", "mcp"] } } }

If this machine is not connected yet, the agent sees one tool, runtime_connect. It gives the agent a link for you to approve. Then every Runtime tool appears. See MCP for other clients and the remote endpoint.

TypeScriptimport { Sandbox } from "withruntime";const sbx = await Sandbox.create();try {  await sbx.files.write("/workspace/invoice.py", "print(sum([125, 250, 375]))\n");  const result = await sbx.exec("python3 /workspace/invoice.py", { check: true });  console.log(result.stdout);} finally {  await sbx.delete();}

Pythonfrom withruntime import Sandboxsbx = Sandbox.create()try:    sbx.files.write("/workspace/invoice.py", "print(sum([125, 250, 375]))\n")    print(sbx.exec("python3 /workspace/invoice.py", check=True).stdout)finally:    sbx.delete()

• Install with npm install withruntime or pip install withruntime.
• The SDKs use RUNTIME_API_KEY when it is set. Otherwise they use the key this machine saved when it connected. After the one line above, they need no setup.
• On a server, create a key at https://withruntime.com/account/keys and give it as RUNTIME_API_KEY from your secret manager.
• create() needs no arguments. It waits until the sandbox is ready, and raises start_failed if it stops first.
• The examples check the command's result, and delete the sandbox even after an error. A stopped sandbox keeps its disk, which is billed until it is deleted. Export anything you need before deleting.

One approval gives this machine its own key. It is encrypted for this machine alone and saved outside your project. The CLI receives and saves its own credential automatically. You do not copy an API key.

• Each connection can use everything the account can, including its prepaid credit. Approve only connections you started.
• Browser sign-out does not revoke one. npx withruntime logout or the API keys page does. See security.
• On a machine with no browser, npx withruntime login --no-browser prints the link to open on another device.
• To use a key you already have, npx withruntime login --with-key reads it from standard input, never from the command line.
• An agent with no person to approve can open its own account and pay in USDC instead: npx withruntime billing topup 20 --new-account --accept-terms --wait. No free trial on that path. The key comes once the payment lands. See pay with stablecoins.

There is nothing to choose between free usage and credit. The free usage is spent first, then prepaid credit. funding in a request is ignored. Once the account holds credit, its sandboxes have paid limits.

Most sandbox code moves over call for call. The switch guide maps E2B, Daytona, Vercel, Modal, Cloudflare, Fly and Blaxel calls to Runtime's. It shows how to work out your monthly saving from measured usage. Code written for E2B, Daytona, Vercel Sandbox, Blaxel or Modal Sandboxes runs after you change one import to withruntime/e2b, withruntime/daytona, withruntime/vercel, withruntime/blaxel or withruntime/modal. Morph's TypeScript client moves to withruntime/morph. A Worker written for Cloudflare's Sandbox SDK moves to withruntime/cloudflare, with its containers block deleted and a RUNTIME_API_KEY secret. Code that calls Fly's Machines API works after you point it at npx withruntime fly-api (withruntime/fly). npx withruntime compare --from <provider> prints what you save. Credit you add within 30 days of signing up is matched, up to $1,000 in total.

Keep the error code, request ID and sandbox ID. A lost response is not proof that nothing ran. Inspect the original resource before trying another create.

See troubleshooting for safe retries and cleanup.

Keep important results outside the sandbox. A sandbox is not a backup.