# Sandbox / Dev Mode

Live development environments with hot reload.

Sandboxes are live development environments with hot reload. Changes apply instantly without a full rebuild — much faster for iterating.

## CLI: `berth dev`

```
berth dev              # Start dev sandbox with file watcher
berth dev App.jsx      # Single-file dev with hot reload
berth dev --attach id  # Reattach to existing sandbox
```

The CLI watches your local files and pushes changes to the sandbox as you edit. For Node/Vite projects, changes appear via HMR (Hot Module Replacement). For Go, the sandbox automatically rebuilds the binary.

## MCP: sandbox tools

AI tools use these MCP tools for the same workflow:

1. `berth_sandbox_create` — create the sandbox with initial files
2. `berth_sandbox_push` — push file changes (instant, no rebuild)
3. `berth_sandbox_install` — add or remove packages
4. `berth_sandbox_exec` — run commands inside the container
5. `berth_sandbox_logs` — check logs for errors
6. `berth_sandbox_promote` — ship it to production when ready

## HTTP API

| Endpoint                     | Description                               |
| ---------------------------- | ----------------------------------------- |
| `POST /api/sandbox`         | Create a sandbox (JSON body with files) |
| `POST /api/sandbox/{id}/push`  | Push file changes                       |
| `POST /api/sandbox/{id}/install` | Install packages                       |
| `POST /api/sandbox/{id}/exec`    | Run a command                          |
| `GET /api/sandbox/{id}/logs`      | Get logs                               |
| `DELETE /api/sandbox/{id}`        | Destroy sandbox                        |
| `POST /api/sandbox/{id}/promote`  | Promote to production                   |

## Promote to production

When you’re happy with your sandbox, promote it. This stops the dev server, runs a full optimized build, and starts a production runtime. The URL stays the same.

```
berth promote abc123
```