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# 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/browse). BrowserViewer launches Chrome via Playwright, exposes a Chrome DevTools Protocol (CDP) URL, and automatically injects it into CLI commands run through [sandbox tools](https://mastra.ai/docs/sandbox/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/integrations/browsers/agent-browser) or [Stagehand](https://mastra.ai/integrations/browsers/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/sandbox/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 { Memory } from '@mastra/memory'
import { LibSQLStore } from '@mastra/libsql'
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-5.6-sol',
  workspace,
  instructions: `You are a web automation assistant.
Use browser-use commands to navigate and interact with websites.`,
  memory: new Memory(),
})

export const mastra = new Mastra({
  agents: { browserAgent },
  storage: new LibSQLStore({
    id: 'mastra-storage',
    url: 'file:./mastra.db',
  }),
})
```

When the agent runs a browser CLI command, Mastra automatically launches Chrome, passes the CDP connection to the CLI, and starts streaming the screencast to Studio. For Browser Use, the agent can pass Python through stdin:

```bash
browser-use <<'PY'
print("Connected to the managed browser")
PY
```

## 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/sandbox/skills) that teaches the agent its commands and workflows.

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

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

### `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
```

For direct stdin invocations (`browser-use`, `browseruse`, `browser`, or `bu`, optionally followed by `<` redirection or a heredoc), Mastra sets `BU_CDP_WS` to the managed browser's CDP URL and `BU_NAME` to a stable daemon name. The name is unique to the thread and browser endpoint, so repeated calls reuse the same daemon while different threads or endpoints stay isolated. Mastra preserves the stdin script without adding CLI arguments.

Legacy subcommands retain `--cdp-url` and `--session` injection for compatibility. These flags aren't added to stdin invocations.

### `browse`

```bash
npm install -g browse
browse skills install
```

CDP flag: `--ws` 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)
- [AgentBrowser](https://mastra.ai/integrations/browsers/agent-browser)
- [Stagehand](https://mastra.ai/integrations/browsers/stagehand)
- [Sandbox](https://mastra.ai/docs/sandbox/overview)
- [Workspace skills](https://mastra.ai/docs/sandbox/skills)