Files
claude-engineering-plugin/plugins/compound-engineering/skills/agent-browser/SKILL.md
Trevin Chow 24860ec3f1 feat: sync agent-browser skill with upstream vercel-labs/agent-browser
Update SKILL.md to match the latest upstream skill from
vercel-labs/agent-browser, adding substantial new capabilities:

- Authentication (auth vault, profiles, session persistence, state files)
- Command chaining, annotated screenshots, diffing
- Security features (content boundaries, domain allowlist, action policy)
- iOS Simulator support, Lightpanda engine, downloads, clipboard
- JS eval improvements (--stdin, -b for shell safety)
- Timeout guidance, config files, session cleanup

Add 7 reference docs (commands, authentication, snapshot-refs,
session-management, video-recording, profiling, proxy-support) and
3 ready-to-use shell templates.

Kept our YAML frontmatter, setup check section, and Playwright MCP
comparison table which are unique to our plugin context.
2026-03-14 20:08:27 -07:00

666 lines
25 KiB
Markdown

---
name: agent-browser
description: Browser automation using Vercel's agent-browser CLI. Use when you need to interact with web pages, fill forms, take screenshots, or scrape data. Alternative to Playwright MCP - uses Bash commands with ref-based element selection. Triggers on "browse website", "fill form", "click button", "take screenshot", "scrape page", "web automation".
---
# Browser Automation with agent-browser
The CLI uses Chrome/Chromium via CDP directly. Install via `npm i -g agent-browser`, `brew install agent-browser`, or `cargo install agent-browser`. Run `agent-browser install` to download Chrome.
## Setup Check
```bash
# Check installation
command -v agent-browser >/dev/null 2>&1 && echo "Installed" || echo "NOT INSTALLED - run: npm install -g agent-browser && agent-browser install"
```
### Install if needed
```bash
npm install -g agent-browser
agent-browser install # Downloads Chromium
```
## Core Workflow
Every browser automation follows this pattern:
1. **Navigate**: `agent-browser open <url>`
2. **Snapshot**: `agent-browser snapshot -i` (get element refs like `@e1`, `@e2`)
3. **Interact**: Use refs to click, fill, select
4. **Re-snapshot**: After navigation or DOM changes, get fresh refs
```bash
agent-browser open https://example.com/form
agent-browser snapshot -i
# Output: @e1 [input type="email"], @e2 [input type="password"], @e3 [button] "Submit"
agent-browser fill @e1 "user@example.com"
agent-browser fill @e2 "password123"
agent-browser click @e3
agent-browser wait --load networkidle
agent-browser snapshot -i # Check result
```
## Command Chaining
Commands can be chained with `&&` in a single shell invocation. The browser persists between commands via a background daemon, so chaining is safe and more efficient than separate calls.
```bash
# Chain open + wait + snapshot in one call
agent-browser open https://example.com && agent-browser wait --load networkidle && agent-browser snapshot -i
# Chain multiple interactions
agent-browser fill @e1 "user@example.com" && agent-browser fill @e2 "password123" && agent-browser click @e3
# Navigate and capture
agent-browser open https://example.com && agent-browser wait --load networkidle && agent-browser screenshot page.png
```
**When to chain:** Use `&&` when you don't need to read the output of an intermediate command before proceeding (e.g., open + wait + screenshot). Run commands separately when you need to parse the output first (e.g., snapshot to discover refs, then interact using those refs).
## Handling Authentication
When automating a site that requires login, choose the approach that fits:
**Option 1: Import auth from the user's browser (fastest for one-off tasks)**
```bash
# Connect to the user's running Chrome (they're already logged in)
agent-browser --auto-connect state save ./auth.json
# Use that auth state
agent-browser --state ./auth.json open https://app.example.com/dashboard
```
State files contain session tokens in plaintext -- add to `.gitignore` and delete when no longer needed. Set `AGENT_BROWSER_ENCRYPTION_KEY` for encryption at rest.
**Option 2: Persistent profile (simplest for recurring tasks)**
```bash
# First run: login manually or via automation
agent-browser --profile ~/.myapp open https://app.example.com/login
# ... fill credentials, submit ...
# All future runs: already authenticated
agent-browser --profile ~/.myapp open https://app.example.com/dashboard
```
**Option 3: Session name (auto-save/restore cookies + localStorage)**
```bash
agent-browser --session-name myapp open https://app.example.com/login
# ... login flow ...
agent-browser close # State auto-saved
# Next time: state auto-restored
agent-browser --session-name myapp open https://app.example.com/dashboard
```
**Option 4: Auth vault (credentials stored encrypted, login by name)**
```bash
echo "$PASSWORD" | agent-browser auth save myapp --url https://app.example.com/login --username user --password-stdin
agent-browser auth login myapp
```
**Option 5: State file (manual save/load)**
```bash
# After logging in:
agent-browser state save ./auth.json
# In a future session:
agent-browser state load ./auth.json
agent-browser open https://app.example.com/dashboard
```
See [references/authentication.md](references/authentication.md) for OAuth, 2FA, cookie-based auth, and token refresh patterns.
## Essential Commands
```bash
# Navigation
agent-browser open <url> # Navigate (aliases: goto, navigate)
agent-browser close # Close browser
# Snapshot
agent-browser snapshot -i # Interactive elements with refs (recommended)
agent-browser snapshot -i -C # Include cursor-interactive elements (divs with onclick, cursor:pointer)
agent-browser snapshot -s "#selector" # Scope to CSS selector
# Interaction (use @refs from snapshot)
agent-browser click @e1 # Click element
agent-browser click @e1 --new-tab # Click and open in new tab
agent-browser fill @e2 "text" # Clear and type text
agent-browser type @e2 "text" # Type without clearing
agent-browser select @e1 "option" # Select dropdown option
agent-browser check @e1 # Check checkbox
agent-browser press Enter # Press key
agent-browser keyboard type "text" # Type at current focus (no selector)
agent-browser keyboard inserttext "text" # Insert without key events
agent-browser scroll down 500 # Scroll page
agent-browser scroll down 500 --selector "div.content" # Scroll within a specific container
# Get information
agent-browser get text @e1 # Get element text
agent-browser get url # Get current URL
agent-browser get title # Get page title
agent-browser get cdp-url # Get CDP WebSocket URL
# Wait
agent-browser wait @e1 # Wait for element
agent-browser wait --load networkidle # Wait for network idle
agent-browser wait --url "**/page" # Wait for URL pattern
agent-browser wait 2000 # Wait milliseconds
agent-browser wait --text "Welcome" # Wait for text to appear (substring match)
agent-browser wait --fn "!document.body.innerText.includes('Loading...')" # Wait for text to disappear
agent-browser wait "#spinner" --state hidden # Wait for element to disappear
# Downloads
agent-browser download @e1 ./file.pdf # Click element to trigger download
agent-browser wait --download ./output.zip # Wait for any download to complete
agent-browser --download-path ./downloads open <url> # Set default download directory
# Viewport & Device Emulation
agent-browser set viewport 1920 1080 # Set viewport size (default: 1280x720)
agent-browser set viewport 1920 1080 2 # 2x retina (same CSS size, higher res screenshots)
agent-browser set device "iPhone 14" # Emulate device (viewport + user agent)
# Capture
agent-browser screenshot # Screenshot to temp dir
agent-browser screenshot --full # Full page screenshot
agent-browser screenshot --annotate # Annotated screenshot with numbered element labels
agent-browser screenshot --screenshot-dir ./shots # Save to custom directory
agent-browser screenshot --screenshot-format jpeg --screenshot-quality 80
agent-browser pdf output.pdf # Save as PDF
# Clipboard
agent-browser clipboard read # Read text from clipboard
agent-browser clipboard write "Hello, World!" # Write text to clipboard
agent-browser clipboard copy # Copy current selection
agent-browser clipboard paste # Paste from clipboard
# Diff (compare page states)
agent-browser diff snapshot # Compare current vs last snapshot
agent-browser diff snapshot --baseline before.txt # Compare current vs saved file
agent-browser diff screenshot --baseline before.png # Visual pixel diff
agent-browser diff url <url1> <url2> # Compare two pages
agent-browser diff url <url1> <url2> --wait-until networkidle # Custom wait strategy
agent-browser diff url <url1> <url2> --selector "#main" # Scope to element
```
## Common Patterns
### Form Submission
```bash
agent-browser open https://example.com/signup
agent-browser snapshot -i
agent-browser fill @e1 "Jane Doe"
agent-browser fill @e2 "jane@example.com"
agent-browser select @e3 "California"
agent-browser check @e4
agent-browser click @e5
agent-browser wait --load networkidle
```
### Authentication with Auth Vault (Recommended)
```bash
# Save credentials once (encrypted with AGENT_BROWSER_ENCRYPTION_KEY)
# Recommended: pipe password via stdin to avoid shell history exposure
echo "pass" | agent-browser auth save github --url https://github.com/login --username user --password-stdin
# Login using saved profile (LLM never sees password)
agent-browser auth login github
# List/show/delete profiles
agent-browser auth list
agent-browser auth show github
agent-browser auth delete github
```
### Authentication with State Persistence
```bash
# Login once and save state
agent-browser open https://app.example.com/login
agent-browser snapshot -i
agent-browser fill @e1 "$USERNAME"
agent-browser fill @e2 "$PASSWORD"
agent-browser click @e3
agent-browser wait --url "**/dashboard"
agent-browser state save auth.json
# Reuse in future sessions
agent-browser state load auth.json
agent-browser open https://app.example.com/dashboard
```
### Session Persistence
```bash
# Auto-save/restore cookies and localStorage across browser restarts
agent-browser --session-name myapp open https://app.example.com/login
# ... login flow ...
agent-browser close # State auto-saved to ~/.agent-browser/sessions/
# Next time, state is auto-loaded
agent-browser --session-name myapp open https://app.example.com/dashboard
# Encrypt state at rest
export AGENT_BROWSER_ENCRYPTION_KEY=$(openssl rand -hex 32)
agent-browser --session-name secure open https://app.example.com
# Manage saved states
agent-browser state list
agent-browser state show myapp-default.json
agent-browser state clear myapp
agent-browser state clean --older-than 7
```
### Data Extraction
```bash
agent-browser open https://example.com/products
agent-browser snapshot -i
agent-browser get text @e5 # Get specific element text
agent-browser get text body > page.txt # Get all page text
# JSON output for parsing
agent-browser snapshot -i --json
agent-browser get text @e1 --json
```
### Parallel Sessions
```bash
agent-browser --session site1 open https://site-a.com
agent-browser --session site2 open https://site-b.com
agent-browser --session site1 snapshot -i
agent-browser --session site2 snapshot -i
agent-browser session list
```
### Connect to Existing Chrome
```bash
# Auto-discover running Chrome with remote debugging enabled
agent-browser --auto-connect open https://example.com
agent-browser --auto-connect snapshot
# Or with explicit CDP port
agent-browser --cdp 9222 snapshot
```
### Color Scheme (Dark Mode)
```bash
# Persistent dark mode via flag (applies to all pages and new tabs)
agent-browser --color-scheme dark open https://example.com
# Or via environment variable
AGENT_BROWSER_COLOR_SCHEME=dark agent-browser open https://example.com
# Or set during session (persists for subsequent commands)
agent-browser set media dark
```
### Viewport & Responsive Testing
```bash
# Set a custom viewport size (default is 1280x720)
agent-browser set viewport 1920 1080
agent-browser screenshot desktop.png
# Test mobile-width layout
agent-browser set viewport 375 812
agent-browser screenshot mobile.png
# Retina/HiDPI: same CSS layout at 2x pixel density
# Screenshots stay at logical viewport size, but content renders at higher DPI
agent-browser set viewport 1920 1080 2
agent-browser screenshot retina.png
# Device emulation (sets viewport + user agent in one step)
agent-browser set device "iPhone 14"
agent-browser screenshot device.png
```
The `scale` parameter (3rd argument) sets `window.devicePixelRatio` without changing CSS layout. Use it when testing retina rendering or capturing higher-resolution screenshots.
### Visual Browser (Debugging)
```bash
agent-browser --headed open https://example.com
agent-browser highlight @e1 # Highlight element
agent-browser inspect # Open Chrome DevTools for the active page
agent-browser record start demo.webm # Record session
agent-browser profiler start # Start Chrome DevTools profiling
agent-browser profiler stop trace.json # Stop and save profile (path optional)
```
Use `AGENT_BROWSER_HEADED=1` to enable headed mode via environment variable. Browser extensions work in both headed and headless mode.
### Local Files (PDFs, HTML)
```bash
# Open local files with file:// URLs
agent-browser --allow-file-access open file:///path/to/document.pdf
agent-browser --allow-file-access open file:///path/to/page.html
agent-browser screenshot output.png
```
### iOS Simulator (Mobile Safari)
```bash
# List available iOS simulators
agent-browser device list
# Launch Safari on a specific device
agent-browser -p ios --device "iPhone 16 Pro" open https://example.com
# Same workflow as desktop - snapshot, interact, re-snapshot
agent-browser -p ios snapshot -i
agent-browser -p ios tap @e1 # Tap (alias for click)
agent-browser -p ios fill @e2 "text"
agent-browser -p ios swipe up # Mobile-specific gesture
# Take screenshot
agent-browser -p ios screenshot mobile.png
# Close session (shuts down simulator)
agent-browser -p ios close
```
**Requirements:** macOS with Xcode, Appium (`npm install -g appium && appium driver install xcuitest`)
**Real devices:** Works with physical iOS devices if pre-configured. Use `--device "<UDID>"` where UDID is from `xcrun xctrace list devices`.
## Security
All security features are opt-in. By default, agent-browser imposes no restrictions on navigation, actions, or output.
### Content Boundaries (Recommended for AI Agents)
Enable `--content-boundaries` to wrap page-sourced output in markers that help LLMs distinguish tool output from untrusted page content:
```bash
export AGENT_BROWSER_CONTENT_BOUNDARIES=1
agent-browser snapshot
# Output:
# --- AGENT_BROWSER_PAGE_CONTENT nonce=<hex> origin=https://example.com ---
# [accessibility tree]
# --- END_AGENT_BROWSER_PAGE_CONTENT nonce=<hex> ---
```
### Domain Allowlist
Restrict navigation to trusted domains. Wildcards like `*.example.com` also match the bare domain `example.com`. Sub-resource requests, WebSocket, and EventSource connections to non-allowed domains are also blocked. Include CDN domains your target pages depend on:
```bash
export AGENT_BROWSER_ALLOWED_DOMAINS="example.com,*.example.com"
agent-browser open https://example.com # OK
agent-browser open https://malicious.com # Blocked
```
### Action Policy
Use a policy file to gate destructive actions:
```bash
export AGENT_BROWSER_ACTION_POLICY=./policy.json
```
Example `policy.json`:
```json
{ "default": "deny", "allow": ["navigate", "snapshot", "click", "scroll", "wait", "get"] }
```
Auth vault operations (`auth login`, etc.) bypass action policy but domain allowlist still applies.
### Output Limits
Prevent context flooding from large pages:
```bash
export AGENT_BROWSER_MAX_OUTPUT=50000
```
## Diffing (Verifying Changes)
Use `diff snapshot` after performing an action to verify it had the intended effect. This compares the current accessibility tree against the last snapshot taken in the session.
```bash
# Typical workflow: snapshot -> action -> diff
agent-browser snapshot -i # Take baseline snapshot
agent-browser click @e2 # Perform action
agent-browser diff snapshot # See what changed (auto-compares to last snapshot)
```
For visual regression testing or monitoring:
```bash
# Save a baseline screenshot, then compare later
agent-browser screenshot baseline.png
# ... time passes or changes are made ...
agent-browser diff screenshot --baseline baseline.png
# Compare staging vs production
agent-browser diff url https://staging.example.com https://prod.example.com --screenshot
```
`diff snapshot` output uses `+` for additions and `-` for removals, similar to git diff. `diff screenshot` produces a diff image with changed pixels highlighted in red, plus a mismatch percentage.
## Timeouts and Slow Pages
The default timeout is 25 seconds. This can be overridden with the `AGENT_BROWSER_DEFAULT_TIMEOUT` environment variable (value in milliseconds). For slow websites or large pages, use explicit waits instead of relying on the default timeout:
```bash
# Wait for network activity to settle (best for slow pages)
agent-browser wait --load networkidle
# Wait for a specific element to appear
agent-browser wait "#content"
agent-browser wait @e1
# Wait for a specific URL pattern (useful after redirects)
agent-browser wait --url "**/dashboard"
# Wait for a JavaScript condition
agent-browser wait --fn "document.readyState === 'complete'"
# Wait a fixed duration (milliseconds) as a last resort
agent-browser wait 5000
```
When dealing with consistently slow websites, use `wait --load networkidle` after `open` to ensure the page is fully loaded before taking a snapshot. If a specific element is slow to render, wait for it directly with `wait <selector>` or `wait @ref`.
## Session Management and Cleanup
When running multiple agents or automations concurrently, always use named sessions to avoid conflicts:
```bash
# Each agent gets its own isolated session
agent-browser --session agent1 open site-a.com
agent-browser --session agent2 open site-b.com
# Check active sessions
agent-browser session list
```
Always close your browser session when done to avoid leaked processes:
```bash
agent-browser close # Close default session
agent-browser --session agent1 close # Close specific session
```
If a previous session was not closed properly, the daemon may still be running. Use `agent-browser close` to clean it up before starting new work.
To auto-shutdown the daemon after a period of inactivity (useful for ephemeral/CI environments):
```bash
AGENT_BROWSER_IDLE_TIMEOUT_MS=60000 agent-browser open example.com
```
## Ref Lifecycle (Important)
Refs (`@e1`, `@e2`, etc.) are invalidated when the page changes. Always re-snapshot after:
- Clicking links or buttons that navigate
- Form submissions
- Dynamic content loading (dropdowns, modals)
```bash
agent-browser click @e5 # Navigates to new page
agent-browser snapshot -i # MUST re-snapshot
agent-browser click @e1 # Use new refs
```
## Annotated Screenshots (Vision Mode)
Use `--annotate` to take a screenshot with numbered labels overlaid on interactive elements. Each label `[N]` maps to ref `@eN`. This also caches refs, so you can interact with elements immediately without a separate snapshot.
```bash
agent-browser screenshot --annotate
# Output includes the image path and a legend:
# [1] @e1 button "Submit"
# [2] @e2 link "Home"
# [3] @e3 textbox "Email"
agent-browser click @e2 # Click using ref from annotated screenshot
```
Use annotated screenshots when:
- The page has unlabeled icon buttons or visual-only elements
- You need to verify visual layout or styling
- Canvas or chart elements are present (invisible to text snapshots)
- You need spatial reasoning about element positions
## Semantic Locators (Alternative to Refs)
When refs are unavailable or unreliable, use semantic locators:
```bash
agent-browser find text "Sign In" click
agent-browser find label "Email" fill "user@test.com"
agent-browser find role button click --name "Submit"
agent-browser find placeholder "Search" type "query"
agent-browser find testid "submit-btn" click
```
## JavaScript Evaluation (eval)
Use `eval` to run JavaScript in the browser context. **Shell quoting can corrupt complex expressions** -- use `--stdin` or `-b` to avoid issues.
```bash
# Simple expressions work with regular quoting
agent-browser eval 'document.title'
agent-browser eval 'document.querySelectorAll("img").length'
# Complex JS: use --stdin with heredoc (RECOMMENDED)
agent-browser eval --stdin <<'EVALEOF'
JSON.stringify(
Array.from(document.querySelectorAll("img"))
.filter(i => !i.alt)
.map(i => ({ src: i.src.split("/").pop(), width: i.width }))
)
EVALEOF
# Alternative: base64 encoding (avoids all shell escaping issues)
agent-browser eval -b "$(echo -n 'Array.from(document.querySelectorAll("a")).map(a => a.href)' | base64)"
```
**Why this matters:** When the shell processes your command, inner double quotes, `!` characters (history expansion), backticks, and `$()` can all corrupt the JavaScript before it reaches agent-browser. The `--stdin` and `-b` flags bypass shell interpretation entirely.
**Rules of thumb:**
- Single-line, no nested quotes -> regular `eval 'expression'` with single quotes is fine
- Nested quotes, arrow functions, template literals, or multiline -> use `eval --stdin <<'EVALEOF'`
- Programmatic/generated scripts -> use `eval -b` with base64
## Configuration File
Create `agent-browser.json` in the project root for persistent settings:
```json
{
"headed": true,
"proxy": "http://localhost:8080",
"profile": "./browser-data"
}
```
Priority (lowest to highest): `~/.agent-browser/config.json` < `./agent-browser.json` < env vars < CLI flags. Use `--config <path>` or `AGENT_BROWSER_CONFIG` env var for a custom config file (exits with error if missing/invalid). All CLI options map to camelCase keys (e.g., `--executable-path` -> `"executablePath"`). Boolean flags accept `true`/`false` values (e.g., `--headed false` overrides config). Extensions from user and project configs are merged, not replaced.
## Browser Engine Selection
Use `--engine` to choose a local browser engine. The default is `chrome`.
```bash
# Use Lightpanda (fast headless browser, requires separate install)
agent-browser --engine lightpanda open example.com
# Via environment variable
export AGENT_BROWSER_ENGINE=lightpanda
agent-browser open example.com
# With custom binary path
agent-browser --engine lightpanda --executable-path /path/to/lightpanda open example.com
```
Supported engines:
- `chrome` (default) -- Chrome/Chromium via CDP
- `lightpanda` -- Lightpanda headless browser via CDP (10x faster, 10x less memory than Chrome)
Lightpanda does not support `--extension`, `--profile`, `--state`, or `--allow-file-access`. Install Lightpanda from https://lightpanda.io/docs/open-source/installation.
## Deep-Dive Documentation
| Reference | When to Use |
| -------------------------------------------------------------------- | --------------------------------------------------------- |
| [references/commands.md](references/commands.md) | Full command reference with all options |
| [references/snapshot-refs.md](references/snapshot-refs.md) | Ref lifecycle, invalidation rules, troubleshooting |
| [references/session-management.md](references/session-management.md) | Parallel sessions, state persistence, concurrent scraping |
| [references/authentication.md](references/authentication.md) | Login flows, OAuth, 2FA handling, state reuse |
| [references/video-recording.md](references/video-recording.md) | Recording workflows for debugging and documentation |
| [references/profiling.md](references/profiling.md) | Chrome DevTools profiling for performance analysis |
| [references/proxy-support.md](references/proxy-support.md) | Proxy configuration, geo-testing, rotating proxies |
## Ready-to-Use Templates
| Template | Description |
| ------------------------------------------------------------------------ | ----------------------------------- |
| [templates/form-automation.sh](templates/form-automation.sh) | Form filling with validation |
| [templates/authenticated-session.sh](templates/authenticated-session.sh) | Login once, reuse state |
| [templates/capture-workflow.sh](templates/capture-workflow.sh) | Content extraction with screenshots |
```bash
./templates/form-automation.sh https://example.com/form
./templates/authenticated-session.sh https://app.example.com/login
./templates/capture-workflow.sh https://example.com ./output
```
## vs Playwright MCP
| Feature | agent-browser (CLI) | Playwright MCP |
|---------|---------------------|----------------|
| Interface | Bash commands | MCP tools |
| Selection | Refs (@e1) | Refs (e1) |
| Output | Text/JSON | Tool responses |
| Parallel | Sessions | Tabs |
| Best for | Quick automation | Tool integration |
Use agent-browser when:
- You prefer Bash-based workflows
- You want simpler CLI commands
- You need quick one-off automation
Use Playwright MCP when:
- You need deep MCP tool integration
- You want tool-based responses
- You're building complex automation