sandbox-next

---
name: sandbox-next
description: Build or maintain Cloudflare Sandbox apps on @cloudflare/sandbox@next (SDK 1.0 preview). Use sandbox-migrate-to-next when porting a stable app.
---

# Sandbox SDK — `@next` (1.0 preview)

Isolated Linux environments on [Cloudflare Containers](https://developers.cloudflare.com/containers/index.md), driven from Workers.

**Prefer preview docs and installed `@next` types over memory.** APIs change; this skill is a gate, a contract, and a retrieval map—not a full manual.

We recommend **new projects** on this line. Apps still on the default package use **`sandbox-stable`**. Port only when asked, via **`sandbox-migrate-to-next`**.

## 1. Gate — confirm the package line

Before writing code, inspect the app:

| Check | Must match |
| ----- | ---------- |
| npm dependency | `@cloudflare/sandbox@next` (or another preview tag) |
| Container image | Same line (e.g. `cloudflare/sandbox:next`, `next-python`) |

| If you find… | Action |
| ------------ | ------ |
| Default `@cloudflare/sandbox` (no `@next`) | **Stop.** Load **`sandbox-stable`**. Do not apply this skill’s APIs. |
| User wants to port stable → `@next` | **Stop.** Load **`sandbox-migrate-to-next`**. |
| Self-deployed **bridge** only | Bridge is **not** on the 1.0 preview line yet. Keep bridge on stable package + image. [Bridge (stable)](https://developers.cloudflare.com/sandbox/sdk/bridge/index.md) |

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

Skills install: [Agent setup](https://developers.cloudflare.com/agent-setup/index.md) · [cloudflare/skills](https://github.com/cloudflare/skills)

## 2. Contract — non-negotiables

- `sandbox.exec(argv)` takes an **argv** list and resolves when the process **starts**. It returns a **handle**, not a finished command result.
- Collect results with handle methods: `output()`, `logs()`, `waitForExit()`, `waitForPort()`, `waitForLog()`, `kill(signal?)`.
- No implicit shell. Shell syntax needs an explicit shell, e.g. `["/bin/bash", "-lc", script]`.
- Each launch is independent. A `cd` / `export` in one `exec` is not visible to the next. Pass `cwd` and `env` per launch, or one shell script.
- Process handles have **no stdin**. Interactive use → terminals (`createTerminal` + `connect`).
- Local wait `timeout` / `AbortSignal` cancel the **wait only**. They do not kill the process. Use `kill` or `exec`’s remote `timeout`.
- `getProcess` / `listProcesses` / `getTerminal` / `listTerminals` do **not** start a container; they return `null` / `[]` when none is up.
- Process and terminal IDs belong to the **current container**, not forever to a sandbox ID. For work that must survive replace, store the full job (argv, cwd, env, app state)—not only an id.
- Non-secret config only in `setEnvVars` / launch `env`. Live credentials stay in the Worker; use outbound handlers when the sandbox calls external APIs.
- Do **not** invent removed stable APIs (`gitCheckout` on core, string-`exec` completion, session execution, `sandbox.terminal(request)`).
- Do **not** use one retry loop for every error (see Errors docs).

Minimal shape:

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

export { Sandbox };

const sandbox = getSandbox(env.Sandbox, "user-123");
const process = await sandbox.exec(["python3", "-c", "print(2 + 2)"]);
const result = await process.output({ encoding: "utf8" });
// result.stdout, result.exitCode
```

Task-specific API documentation: [references/api-quick-ref.md](references/api-quick-ref.md)

Examples index (`next` branch): [references/examples.md](references/examples.md)

## 3. Retrieve — open the doc for the task

Fetch the page before implementing. Installed `@next` types win over guesses.

| You need to… | Open |
| ------------ | ---- |
| Orient / choose preview | [1.0 preview overview](https://developers.cloudflare.com/sandbox/index.md) |
| First Worker, wrangler, Dockerfile | [Get started](https://developers.cloudflare.com/sandbox/index.md) |
| `exec`, handles, readiness, durability | [Process execution](https://developers.cloudflare.com/sandbox/index.md) |
| Process API signatures | [Processes API](https://developers.cloudflare.com/sandbox/index.md) |
| Sandbox ID vs container vs sleep/destroy | [Lifecycle](https://developers.cloudflare.com/sandbox/index.md) |
| `cwd` / `env` / `setEnvVars` | [Environment](https://developers.cloudflare.com/sandbox/index.md) |
| Interactive PTY / browser terminal | [Terminals](https://developers.cloudflare.com/sandbox/index.md) · [Terminals API](https://developers.cloudflare.com/sandbox/index.md) |
| Python/JS code interpreter | [Interpreter](https://developers.cloudflare.com/sandbox/index.md) · [Interpreter API](https://developers.cloudflare.com/sandbox/index.md) |
| Extensions model | [Extensions](https://developers.cloudflare.com/sandbox/index.md) |
| Error classes and recovery | [Errors](https://developers.cloudflare.com/sandbox/index.md) · [Errors API](https://developers.cloudflare.com/sandbox/index.md) |
| Common failures | [Troubleshooting](https://developers.cloudflare.com/sandbox/index.md) |
| API hub | [API reference](https://developers.cloudflare.com/sandbox/index.md) |
| Files, mounts, backups, ports, tunnels, `proxyToSandbox` | Main docs for shared surfaces (ignore stable-only session/transport/`sandbox.terminal`): [Files](https://developers.cloudflare.com/sandbox/sdk/api/files/index.md) · [Storage / mounts](https://developers.cloudflare.com/sandbox/sdk/api/storage/index.md) · [Ports](https://developers.cloudflare.com/sandbox/sdk/api/ports/index.md) · [Tunnels](https://developers.cloudflare.com/sandbox/sdk/api/tunnels/index.md) · [Backups](https://developers.cloudflare.com/sandbox/sdk/api/backups/index.md) · [Outbound traffic](https://developers.cloudflare.com/sandbox/sdk/guides/outbound-traffic/index.md) · [Expose services](https://developers.cloudflare.com/sandbox/sdk/guides/expose-services/index.md) · [Production](https://developers.cloudflare.com/sandbox/sdk/guides/preview-urls-custom-domain/index.md) |
| Example apps | [examples on `next`](https://github.com/cloudflare/sandbox-sdk/tree/next/examples) |
| Still on stable package | **`sandbox-stable`** · [Main Sandbox docs](https://developers.cloudflare.com/sandbox/index.md) |
| Porting an existing stable app | **`sandbox-migrate-to-next`** · [Migrate](https://developers.cloudflare.com/sandbox/sdk/migrate/index.md) |

## 4. Before you ship

- Lockfile and Dockerfile on the **same** `@next` line  
- Typecheck against installed `@next` types  
- No live secrets in sandbox env  
- Production preview hostnames need wildcard DNS on a custom domain when using those URL patterns