Sandbox SDK

Build secure, isolated code execution environments on Cloudflare Workers.

When to Use

• running LLM-generated code in isolation
• executing user-submitted scripts safely
• needing sandboxed compute with file access on edge
• building an AI code interpreter / dev environment

Core Rules

• Do NOT use internal clients (CommandClient, FileClient) - use standard sandbox.* wrapper methods.
• The Worker entrypoint script MUST explicitly include export { Sandbox } from '@cloudflare/sandbox'.
• Do not skip destroy() calls on temporary sandboxes to avoid resource leaks.
• Keep container images lean in the Dockerfile to optimize startup and prevent cold start latency.
• Always set explicit resource limits including timeout_ms (up to 30,000 ms), memory_mb, and cpu_ms on every sandbox invocation to prevent unbounded execution.
• Manage network isolation by routing necessary sandboxed network requests through the Worker's allowed callback pattern using the env.SANDBOX binding.
• Adhere to overarching policy core/policies/execution-sandbox.md (Tier 4 Managed Cloud Sandbox) for universal resource quotas and containment standards.