Build sandboxed applications for secure code execution. Load when building AI code execution, code interpreters, CI/CD systems, interactive dev environments, or executing untrusted code. Covers Sandbox SDK lifecycle, commands, files, code interpreter, and preview URLs. Biases towards retrieval from Cloudflare docs over pre-trained knowledge.
Creates secure, isolated code execution environments on Cloudflare Workers for running untrusted code.
npx claudepluginhub cloudflare/skillsThis skill inherits all available tools. When active, it can use any tool Claude has access to.
references/api-quick-ref.mdreferences/examples.mdBuild secure, isolated code execution environments on Cloudflare Workers.
npm install @cloudflare/sandbox
docker info # Must succeed - Docker required for local dev
Your knowledge of the Sandbox SDK may be outdated. Prefer retrieval over pre-training for any Sandbox SDK task.
When implementing features, fetch the relevant doc page or example first.
wrangler.jsonc (exact - do not modify structure):
{
"containers": [{
"class_name": "Sandbox",
"image": "./Dockerfile",
"instance_type": "lite",
"max_instances": 1
}],
"durable_objects": {
"bindings": [{ "class_name": "Sandbox", "name": "Sandbox" }]
},
"migrations": [{ "new_sqlite_classes": ["Sandbox"], "tag": "v1" }]
}
Worker entry - must re-export Sandbox class:
import { getSandbox } from '@cloudflare/sandbox';
export { Sandbox } from '@cloudflare/sandbox'; // Required export
| Task | Method |
|---|---|
| Get sandbox | getSandbox(env.Sandbox, 'user-123') |
| Run command | await sandbox.exec('python script.py') |
| Run code (interpreter) | await sandbox.runCode(code, { language: 'python' }) |
| Write file | await sandbox.writeFile('/workspace/app.py', content) |
| Read file | await sandbox.readFile('/workspace/app.py') |
| Create directory | await sandbox.mkdir('/workspace/src', { recursive: true }) |
| List files | await sandbox.listFiles('/workspace') |
| Expose port | await sandbox.exposePort(8080) |
| Destroy | await sandbox.destroy() |
const sandbox = getSandbox(env.Sandbox, 'user-123');
const result = await sandbox.exec('python --version');
// result: { stdout, stderr, exitCode, success }
Use runCode() for executing LLM-generated code with rich outputs:
const ctx = await sandbox.createCodeContext({ language: 'python' });
await sandbox.runCode('import pandas as pd; data = [1,2,3]', { context: ctx });
const result = await sandbox.runCode('sum(data)', { context: ctx });
// result.results[0].text = "6"
Languages: python, javascript, typescript
State persists within context. Create explicit contexts for production.
await sandbox.mkdir('/workspace/project', { recursive: true });
await sandbox.writeFile('/workspace/project/main.py', code);
const file = await sandbox.readFile('/workspace/project/main.py');
const files = await sandbox.listFiles('/workspace/project');
| Need | Use | Why |
|---|---|---|
| Shell commands, scripts | exec() | Direct control, streaming |
| LLM-generated code | runCode() | Rich outputs, state persistence |
| Build/test pipelines | exec() | Exit codes, stderr capture |
| Data analysis | runCode() | Charts, tables, pandas |
Base image (docker.io/cloudflare/sandbox:0.7.0) includes Python 3.11, Node.js 20, and common tools.
Add dependencies by extending the Dockerfile:
FROM docker.io/cloudflare/sandbox:0.7.0
# Python packages
RUN pip install requests beautifulsoup4
# Node packages (global)
RUN npm install -g typescript
# System packages
RUN apt-get update && apt-get install -y ffmpeg && rm -rf /var/lib/apt/lists/*
EXPOSE 8080 # Required for local dev port exposure
Keep images lean - affects cold start time.
Expose HTTP services running in sandboxes:
const { url } = await sandbox.exposePort(8080);
// Returns preview URL for the service
Production requirement: Preview URLs need a custom domain with wildcard DNS (*.yourdomain.com). The .workers.dev domain does not support preview URL subdomains.
See: https://developers.cloudflare.com/sandbox/guides/expose-services/
The SDK provides helpers for OpenAI Agents at @cloudflare/sandbox/openai:
import { Shell, Editor } from '@cloudflare/sandbox/openai';
See examples/openai-agents for complete integration pattern.
getSandbox() returns immediately - container starts lazily on first operationsleepAfter)destroy() to immediately free resourcessandboxId always returns same sandbox instanceCommandClient, FileClient) - use sandbox.* methodsexport { Sandbox }destroy() for temporary sandboxesActivates when the user asks about AI prompts, needs prompt templates, wants to search for prompts, or mentions prompts.chat. Use for discovering, retrieving, and improving prompts.
Search, retrieve, and install Agent Skills from the prompts.chat registry using MCP tools. Use when the user asks to find skills, browse skill catalogs, install a skill for Claude, or extend Claude's capabilities with reusable AI agent components.
This skill should be used when the user asks to "create an agent", "add an agent", "write a subagent", "agent frontmatter", "when to use description", "agent examples", "agent tools", "agent colors", "autonomous agent", or needs guidance on agent structure, system prompts, triggering conditions, or agent development best practices for Claude Code plugins.