/cloudflare-sandbox

name: cloudflare-sandbox
description: "Cloudflare Sandboxes SDK for secure code execution in Linux containers at edge. Use for untrusted code, Python/Node.js scripts, AI code interpreters, git operations."

metadata:
  keywords:
    - cloudflare sandbox
    - container execution
    - code execution
    - isolated environment
    - durable objects
    - linux container
    - python execution
    - node execution
    - git operations
    - code interpreter
    - AI agents
    - session management
    - ephemeral container
    - workspace
    - sandbox SDK
    - "@cloudflare/sandbox"
    - exec()
    - getSandbox()
    - runCode()
    - gitCheckout()
    - ubuntu container

license: MIT

Cloudflare Sandboxes SDK

**Status**: Production Ready (Open Beta) **Last Updated**: 2025-12-10 **Dependencies**: `cloudflare-worker-base`, `cloudflare-durable-objects` (recommended for understanding) **Latest Versions**: `@cloudflare/sandbox@0.6.3`, Docker image: `cloudflare/sandbox:0.6.3-python`

**⚠️ BREAKING CHANGE (v0.6.0):** Python is no longer included in the default image. Use `cloudflare/sandbox:<version>-python` for Python support (~1.3GB with data science packages). The lean variant (~600-800MB) excludes Python.

---

Quick Start (15 Minutes)

1. Install SDK and Setup Wrangler

bun add @cloudflare/sandbox@latest  # preferred
# or: bun add @cloudflare/sandbox@latest

**wrangler.jsonc:**

{
  "name": "my-sandbox-worker",
  "main": "src/index.ts",
  "compatibility_flags": ["nodejs_compat"],
  "containers": [{
    "class_name": "Sandbox",
    "image": "cloudflare/sandbox:0.6.3-python",
    "instance_type": "lite"
  }],
  "durable_objects": {
    "bindings": [{
      "class_name": "Sandbox",
      "name": "Sandbox"
    }]
  },
  "migrations": [{
    "tag": "v1",
    "new_sqlite_classes": ["Sandbox"]
  }]
}

**Why this matters:**

• `nodejs_compat` enables Node.js APIs required by SDK
• `containers` defines the Ubuntu container image
• `durable_objects` binding enables persistent routing
• `migrations` registers the Sandbox class

2. Create Your First Sandbox Worker

import { getSandbox, type Sandbox } from '@cloudflare/sandbox';
export { Sandbox } from '@cloudflare/sandbox';

type Env = {
  Sandbox: DurableObjectNamespace<Sandbox>;
};

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    // Get sandbox instance (creates if doesn't exist)
    const sandbox = getSandbox(env.Sandbox, 'my-first-sandbox');

    // Execute Python code
    const result = await sandbox.exec('python3 -c "print(2 + 2)"');

    return Response.json({
      output: result.stdout,
      success: result.success,
      exitCode: result.exitCode
    });
  }
};

**CRITICAL:**

• **MUST export** `{ Sandbox }` from `@cloudflare/sandbox` in your Worker
• Sandbox ID determines routing (same ID = same container)
• First request creates container (~2-3 min cold start)
• Subsequent requests are fast (<1s)

3. Deploy and Test

npm run deploy
curl https://your-worker.workers.dev

Expected output:

{
  "output": "4\n",
  "success": true,
  "exitCode": 0
}

Secure Installation

Sandbox SDK packages grant container access — verify before installing to prevent unauthorized code execution. Follow supply chain security best practices:

• **Block post-install scripts** — `npm config set ignore-scripts true` (or Bun: disabled by default)
• **Cooldown period** — Wait 7 days for new package versions to be vetted by the community
• **Audit before installing** — Run `socket package score npm <pkg>` or use `socket npm install <pkg>` to check packages

Load the `dependency-upgrade` skill for full security configuration including Socket CLI integration, cooldown setup, lockfile validation, and CI enforcement.

---

Architecture (Understanding the 3-Layer Model)

How Sandboxes Work

┌─────────────────────────────────────────┐
│  Your Worker (Layer 1)                  │
│  - Handles HTTP requests                │
│  - Calls getSandbox()                   │
│  - Uses sandbox.exec(), writeFile(), etc│
└──────────────┬──────────────────────────┘
               │ RPC via Durable Object
┌──────────────▼──────────────────────────┐
│  Durable Object (Layer 2)               │
│  - Routes by sandbox ID                 │
│  - Maintains persistent identity        │
│  - Geographic stickiness                │
└──────────────┬──────────────────────────┘
               │ Container API
┌──────────────▼──────────────────────────┐
│  Ubuntu Container (Layer 3)             │
│  - Full Linux environment               │
│  - Python 3.11, Node 20, Git, etc.      │
│  - Filesystem: /workspace, /tmp, /home  │
│  - Process isolation (VM-based)         │
└─────────────────────────────────────────┘

**Key Insight**: Workers handle API logic (fast), Durable Objects route requests (persistent identity), Containers execute code (full capabilities).

---

Critical Container Lifecycle (Most Important Section!)

Container States

┌─────────┐  First request  ┌────────┐  ~10 min idle  ┌──────┐
│ Not     │ ───────────────>│ Active │ ─────────────> │ Idle │
│ Created │                 │        │                │      │
└─────────┘                 └───┬────┘                └──┬───┘
                                │ ^                      │
                                │ │ New request          │
                                │ └──────────────────────┘
                                │                         │
                                ▼                         ▼
                            Files persist          ALL FILES DELETED
                            Processes run          ALL PROCESSES KILLED
                            State maintained       ALL STATE RESET

The #1 Gotcha: Ephemeral by Default

**While Container is Active** (~10 min after last request):

• ✅ Files in `/workspace`, `/tmp`, `/home` persist
• ✅ Background proce