Set RUNTIME_API_KEY from your secret manager (create a key at https://withruntime.com/account/keys). Never put a key in browser code, a URL or a command-line argument.

import { Sandbox } from "@withruntime/cloud";

await using sbx = await Sandbox.create();
const result = await sbx.exec("python3 -c 'print(6 * 7)'");
console.log(result.exitCode, result.stdout);

Sandbox.create() needs no arguments and returns once the sandbox is running; await using stops it when the block ends. With no arguments you get the free trial while it lasts (20 hours, up to three sandboxes at once), 2 vCPU, 4 GiB of memory and a 4 GiB disk.

The sandbox object does the rest:

exec, execStream, spawn and processes for commands and background work, with cwd, env (the place for secrets), stdin and timeoutMs;
terminal() for an interactive terminal over a WebSocket;
files to read, write, list, glob, stat, move and remove, and to copy whole directories with upload and download;
pause, wake, extend, fork and snapshot;
interpreter, network, previews and desktop for the other products.

The client has sandboxes, images, volumes, snapshots, feedback and support. Every write carries an idempotency key, made for you, so the SDK's own retries (timeouts, 429, 503) never do anything twice. Errors are typed and carry a code, a hint and a requestId.

CLI

npx @withruntime/cloud login        # connect once in your browser; no key to copy
npx @withruntime/cloud sandbox create
npx @withruntime/cloud help

Installed globally, the command is runtime (also runtime-cloud): runtime sandbox exec <id> -- ls, runtime sandbox shell <id>, runtime image build --pip pandas, and --json on every command.

MCP

runtime mcp serves Runtime's MCP tools on stdio for agents that want a local command, over the saved connection. Remote agents use https://api.withruntime.com/mcp with a bearer key.

Docs: https://withruntime.com/docs/javascript and https://withruntime.com/docs/cli.