Sandbox SDK — stable package skill

Sandbox SDK — stable package

Isolated Linux environments on Cloudflare Containers, driven from Workers.

Prefer the main Sandbox docs and installed stable types over memory. This skill is a gate, a contract, and a retrieval map—not a full manual.

This line is the current stable default npm package. The main Sandbox documentation describes it. Existing apps can stay here and keep shipping.

We recommend new projects on @cloudflare/sandbox@next with sandbox-next. When you can, plan a move with sandbox-migrate-to-next so you are ready when 1.0 becomes the stable release. Do not force that port unless the user asks.

1. Gate — confirm the package line

Before writing code, inspect the app:

Check	Must match
npm dependency	Default @cloudflare/sandbox (not @next / preview tags)
Container image	Matching stable image (not cloudflare/sandbox:next)

If you find…	Action
@cloudflare/sandbox@next or a next image	Stop. Load sandbox-next.
User wants to port to 1.0 / @next	Stop. Load sandbox-migrate-to-next. Do not half-apply preview APIs on a stable package.
Only cleaning deprecated stable APIs	Stay here; use the 2026 deprecation guide. That is not a move to @next.

Never mix a stable Worker package with an @next container image (or the reverse).

Skills install: Agent setup · cloudflare/skills

2. Contract — non-negotiables

• await sandbox.exec(command) takes a command string and resolves when the command finishes, with buffered stdout / stderr / exitCode (and related fields).
• Long-running and streaming work use the stable command APIs (startProcess, execStream, and related helpers)—not the @next single-handle model. Open the Commands docs; do not invent @next output() handles on stable.
• Sessions can preserve working directory and environment across commands (default session / enableDefaultSession, createSession). See Sessions docs when state must carry across calls.
• Interactive browser terminals often use sandbox.terminal(request) and session/xterm helpers on stable—not preview createTerminal unless the package is @next.
• Prefer RPC transport when using tunnels or large/binary streaming. HTTP/WebSocket transports are deprecated (cleanup guide below).
• Files, mounts, ports, tunnels, backups, lifecycle, and interpreter: use main docs for signatures; trust installed stable types.
• Non-secret config in sandbox env; live credentials in the Worker. Use outbound handlers when processes call external APIs.
• Production preview hostnames need wildcard DNS on a custom domain when using those URL patterns.
• Do not apply @next argv/process.output() APIs while the dependency is still stable.
• Self-deployed bridge stays on the stable package and image. Bridge

Minimal shape:

import { getSandbox, proxyToSandbox, Sandbox } from "@cloudflare/sandbox";

export { Sandbox };

const sandbox = getSandbox(env.Sandbox, "user-123");
const result = await sandbox.exec('python3 -c "print(2 + 2)"');
// result.stdout, result.exitCode, result.success

3. Retrieve — open the doc for the task

Fetch the page before implementing. Installed stable types win over guesses.

You need to…	Open
Orient	Sandbox overview
First Worker, template, Docker	Get started
exec, streaming, background processes	Commands API · Execute commands · Background processes · Streaming output
Sessions / shell state across commands	Sessions concept · Sessions API
getSandbox options, sleep, destroy	Lifecycle API · Sandbox options
Env vars	Environment variables
Files	Files API · Manage files · File watching
Buckets / mounts	Storage API · Mount buckets
Backups	Backups API · Backup and restore
Ports, preview URLs, expose	Ports API · Expose services
Tunnels	Tunnels API
Proxy / Workers connections	Proxy requests · Workers connections
Browser / PTY terminal	Terminal API · Terminal concept · Browser terminals
Code interpreter	Interpreter API · Code execution
Git in the sandbox	Git workflows
Secrets / egress	Outbound traffic
WebSockets	WebSocket connections
Docker-in-Docker	Docker in Docker
Production deploy	Production deployment
Containers concept	Containers
How-to index	Guides
API index	API reference
Deprecated APIs while staying on stable	2026 deprecation guide
Self-deployed bridge	Bridge · Bridge HTTP API
Examples (stable/main)	examples on GitHub
New work on 1.0 preview	sandbox-next · 1.0 preview
Port existing app to @next	sandbox-migrate-to-next · Migrate

Deprecated-API cleanup (stay on stable)

Update package + matching image first, then follow the guide. Typical search:

rg 'SANDBOX_TRANSPORT|transport:|exposePort\(|enableDefaultSession|execStream\(|readFileStream|writeFileStream'

This path does not switch you to @next.

4. Before you ship

• Worker package and container image on the same stable line
• Typecheck against installed stable types
• No live secrets in sandbox env
• If using deprecated transports/helpers, finish or track 2026 deprecation cleanup
• When the team is ready for 1.0, use sandbox-migrate-to-next—do not force cutover unprompted