Get started with stateless mode

Deploy a runtime Worker and call it directly with the free runCode function — no sandbox, no code context, no files.

1. Deploy a runtime Worker per language

Deploy one runtime Worker for each language you need. This guide deploys Python first.

Open Deploy a runtime Worker and choose Python. In Cloudflare, select your account and a unique Worker name. Keep the detected build and deploy commands. The templates require a Paid Workers plan for their configured CPU allowance.

Record the deployed name, such as sandbox-python. A successful runtime deployment has no public URL; this is intentional.

Open Deploy a runtime Worker again and repeat for JavaScript as a second runtime Worker, recording that name too, such as sandbox-javascript — the example below calls both.

2. Install the typed client

pnpm add @sandbox-workers/core

3. Add a services entry per runtime Worker

Stateless mode needs only a Service Binding to each runtime Worker you deployed — no durable_objects, no migrations, and no Sandbox export in your entry point:

{
  "services": [
    { "binding": "PYTHON", "service": "sandbox-python" },
    { "binding": "JAVASCRIPT", "service": "sandbox-javascript" },
  ],
}

One entry per runtime Worker; the binding names are yours to choose. Each service value must exactly match the name you selected when deploying, and every bound Worker must belong to the same Cloudflare account.

4. Call runCode

import { runCode } from "@sandbox-workers/core";

export default {
  async fetch(request, env) {
    const result = await runCode(
      env.PYTHON,
      "print('Hello!')\nimport os\nint(os.environ['X']) ** 2",
      { envVars: { X: "12" } },
    );
    return Response.json(result);
  },
};

Deploy your caller after the runtime Worker. env.PYTHON names the Service Binding from step 3 — that’s what selects the language, never a language option. runCode(target, code, options?) sends the request over the binding only, so nothing leaves your account — no sandbox, no code context, just a fresh Wasm instance for this one call.

The result has no error, results: [{ text: "144" }], and the captured greeting in logs.stdout. Nothing about this call persists — the next call starts from scratch.

Calling a second runtime Worker is the same function again, against the other binding:

const jsResult = await runCode(env.JAVASCRIPT, "1 + 1");

The binding you pass is the only thing that selects the language — call as many runtime Workers as you have bound.

Next steps

• Execute code: read results, logs, and error, and use one binding per runtime for multiple languages.
• Security: before exposing a caller that accepts arbitrary code, configure its authentication and rate limits.
• API: the free runCode() function: the full signature and result shape.

Need state or files? See Get started with stateful mode.