# BrowserViewer

The `@mastra/browser-viewer` package provides browser automation for CLI-based tools like [agent-browser](https://www.npmjs.com/package/agent-browser), [browser-use](https://pypi.org/project/browser-use/), and [browse](https://www.npmjs.com/package/@browserbasehq/browse-cli). BrowserViewer launches Chrome via Playwright, exposes a Chrome DevTools Protocol (CDP) URL, and automatically injects it into CLI commands run through [workspace tools](https://mastra.ai/docs/workspace/overview).

## When to use BrowserViewer

Use BrowserViewer when your agent drives a browser through a CLI tool rather than an SDK. BrowserViewer handles:

- Launching and managing Chrome for CLI tools to connect to
- Automatic CDP URL injection into `workspace_execute_command` calls
- Live screencast streaming to Studio
- Thread-scoped browser isolation

For SDK-based browser automation, use [AgentBrowser](https://mastra.ai/docs/browser/agent-browser) or [Stagehand](https://mastra.ai/docs/browser/stagehand) instead.

## Quickstart

Install `@mastra/browser-viewer` and the CLI tool your agent will use. BrowserViewer manages Chrome, but the CLI tool itself must be installed separately.

**npm**:

```bash
npm install @mastra/browser-viewer
```

**pnpm**:

```bash
pnpm add @mastra/browser-viewer
```

**Yarn**:

```bash
yarn add @mastra/browser-viewer
```

**Bun**:

```bash
bun add @mastra/browser-viewer
```

Install the CLI tool in your workspace environment. This example uses `browser-use`:

```bash
pip install browser-use
```

Install the corresponding [skill](https://mastra.ai/docs/workspace/skills) so the agent knows how to use the CLI:

```bash
npx skills add browser-use/browser-use --skill browser-use
```

Create a workspace with BrowserViewer and assign it to an agent:

```typescript
import { Mastra } from '@mastra/core/mastra'
import { Agent } from '@mastra/core/agent'
import { Workspace, LocalSandbox } from '@mastra/core/workspace'
import { BrowserViewer } from '@mastra/browser-viewer'

const workspace = new Workspace({
  sandbox: new LocalSandbox({
    workingDirectory: './workspace',
  }),
  browser: new BrowserViewer({
    cli: 'browser-use',
    headless: false,
  }),
})

const browserAgent = new Agent({
  id: 'browser-agent',
  model: 'openai/gpt-5.5',
  workspace,
  instructions: `You are a web automation assistant.
Use browser-use commands to navigate and interact with websites.`,
})

export const mastra = new Mastra({
  agents: { browserAgent },
})
```

When the agent runs a CLI command like `browser-use open https://example.com`, Mastra automatically launches Chrome, injects the CDP connection, and starts streaming the screencast to Studio.

## How it works

1. The agent calls `workspace_execute_command` with a browser CLI command.
2. Mastra detects the CLI command and launches Chrome via Playwright (if not already running).
3. The CDP URL is injected into the command so the CLI connects to the managed browser.
4. Screencast frames stream from page-level CDP sessions to Studio.

## Supported CLIs

BrowserViewer supports three CLI providers. Each CLI must be installed separately in your workspace environment. Each CLI also publishes a [skill](https://mastra.ai/docs/workspace/skills) that teaches the agent its commands and workflows.

### agent-browser

```bash
npm install -g agent-browser
npx skills add vercel-labs/agent-browser
```

CDP flag: `--cdp`

### browser-use

```bash
pip install browser-use
npx skills add browser-use/browser-use --skill browser-use
```

CDP flag: `--cdp-url`

### browse-cli

```bash
npm install -g @browserbasehq/browse-cli
npx skills add browserbase/skills
```

CDP flag: `--ws`

Set the `cli` option to match the CLI your agent uses:

```typescript
const viewer = new BrowserViewer({
  cli: 'browser-use',
  headless: false,
})
```

> **Note:** See [BrowserViewer reference](https://mastra.ai/reference/browser/browser-viewer) for all configuration options, advanced connection modes, and method details.

## Related

- [Browser overview](https://mastra.ai/docs/browser/overview)
- [AgentBrowser](https://mastra.ai/docs/browser/agent-browser)
- [Stagehand](https://mastra.ai/docs/browser/stagehand)
- [Workspace overview](https://mastra.ai/docs/workspace/overview)
- [Workspace skills](https://mastra.ai/docs/workspace/skills)