Agents – Interactive browser terminals in Sandboxes

9 February 20262 minutesAgents, Cloudflare Modern Workspace Pro

The Sandbox SDK now supports PTY (pseudo-terminal) passthrough, enabling browser-based terminal UIs to connect to sandbox shells via WebSocket.

`sandbox.terminal(request)`

The new terminal() method proxies a WebSocket upgrade to the container’s PTY endpoint, with output buffering for replay on reconnect.

JavaScript

// Worker: proxy WebSocket to container terminal
return sandbox.terminal(request, { cols: 80, rows: 24 });

TypeScript

// Worker: proxy WebSocket to container terminal
return sandbox.terminal(request, { cols: 80, rows: 24 });

Multiple terminals per sandbox

Each session can have its own terminal with an isolated working directory and environment, so users can run separate shells side-by-side in the same container.

JavaScript

// Multiple isolated terminals in the same sandbox
const dev = await sandbox.getSession("dev");
return dev.terminal(request);

TypeScript

// Multiple isolated terminals in the same sandbox
const dev = await sandbox.getSession("dev");
return dev.terminal(request);

xterm.js addon

The new @cloudflare/sandbox/xterm export provides a SandboxAddon for xterm.js with automatic reconnection (exponential backoff + jitter), buffered output replay, and resize forwarding.

JavaScript

import { SandboxAddon } from "@cloudflare/sandbox/xterm";

const addon = new SandboxAddon({
  getWebSocketUrl: ({ sandboxId, origin }) =>
    `${origin}/ws/terminal?id=${sandboxId}`,
  onStateChange: (state, error) => updateUI(state),
});
terminal.loadAddon(addon);
addon.connect({ sandboxId: "my-sandbox" });

TypeScript

import { SandboxAddon } from "@cloudflare/sandbox/xterm";

const addon = new SandboxAddon({
  getWebSocketUrl: ({ sandboxId, origin }) =>
    `${origin}/ws/terminal?id=${sandboxId}`,
  onStateChange: (state, error) => updateUI(state),
});
terminal.loadAddon(addon);
addon.connect({ sandboxId: "my-sandbox" });