atr-browser

Companion skill — atr-computer controls the OS desktop (mouse, keyboard, screen, windows, app launch, plus an in-process LLM agent via atr computer ask). Load both when:

• The browser action needs an OS file picker, drag from the file manager, or anything outside the page (e.g. authentication via 1Password desktop app).
• You want a single high-level instruction to span web + desktop — atr computer ask "<instruction>" can call atr browser along the way.

Browser daemon listens on port 9333; computer daemon on 9334. Both can run simultaneously.

ATR Browser Automation Skill

This skill provides browser automation capabilities through ATR's browser server mode. The browser server runs as a daemon process and accepts CLI commands for browser control.

Architecture

Claude Code --> atr CLI (client) --> ATR Server + Browser

The browser runs in visible (non-headless) mode by default for debugging and verification.

Getting Started

Step 1: Check Browser Status and Start if Needed

Before any browser operations, verify the browser server is running:

atr browser status

If the server is not running, start it:

atr browser start

The server stores state at ~/.atr/browser.state which allows subsequent commands to discover the endpoint automatically.

Step 2: Navigate and Interact

Once running, use navigation and interaction commands to control the browser.

Command Categories

Lifecycle Commands

Command	Description
atr browser start [--port PORT]	Start browser daemon (default port: 9333)
atr browser stop	Stop browser daemon
atr browser status	Check if browser is running

Navigation Commands

Command	Description
atr browser navigate <url>	Navigate to URL
atr browser back	Go back in history
atr browser forward	Go forward in history
atr browser reload	Reload current page

Page Management Commands

Command	Description
atr browser new-page [url]	Open new tab
atr browser list-pages	List all tabs
atr browser select-page <index>	Switch to tab (0-based)
atr browser close-page <index>	Close tab

Interaction Commands

Command	Description
atr browser click <target> [--double]	Click element (use --double for double-click)
atr browser fill <target> <value>	Type into input field
atr browser hover <target>	Hover over element
atr browser press-key <key>	Press keyboard key (e.g., Enter, Tab, Control+A)
atr browser drag <from> <to>	Drag element
atr browser wait <selector> [--timeout] [--visible]	Wait for element to appear
atr browser scroll --selector "<sel>" [--y N] [--to-bottom]	Scroll inside an element
atr browser download-images "<sel>" [--output-dir] [--fallback-screenshot]	Download/screenshot images within elements
atr browser viewport [W H] [--preset mobile|tablet|desktop|wide]	Get or set viewport size
atr browser batch [--file F] [--on-error stop|continue|retry:N]	Execute multiple commands from stdin/file

Recording Commands

Command	Description
atr browser record [--url URL] [-o FILE]	Record browser interactions as a behavior test

Inspection Commands

Command	Description
atr browser snapshot [--verbose]	Get page elements with UIDs
atr browser screenshot --file [--full] [-s SELECTOR]	Capture screenshot (saves to /tmp/)
atr browser screenshot --file --selector-all "<sel>"	Screenshot all matching elements
atr browser computed-styles "<selector>" [--properties]	Get computed CSS styles for single element
atr browser computed-styles --selector-all "<sel>"	Get computed CSS styles for all matching elements
atr browser computed-styles-diff "<sel>" --against N	Compare styles between pages
atr browser text "<selector>" [--flat|--links|--headings]	Extract text content
atr browser font-check "<font-family>"	Check if font is loaded and rendering
atr browser clean-snapshot "<selector>" [--depth N] [--max-length N]	Get cleaned DOM subtree (no noise/tracking attrs)
atr browser computed-styles --selector "h1" --selector "p"	Batch computed styles for multiple selectors
atr browser computed-styles-diff --selector "h1" --selector "p" --against 0	Batch style diff with overall score
atr browser html	Get page HTML
atr browser url	Get current URL
atr browser title	Get page title
atr browser eval <script>	Execute JavaScript
atr browser ask "<question>"	Ask a question about the current page

Screenshot Note: Use --file to save screenshots to /tmp/ with a timestamped filename (e.g., /tmp/atr-screenshot-20240105-103045.png). Add --full for full-page screenshots. Use --selector / -s to screenshot a specific element by CSS selector (e.g., -s "header", -s "#nav", -s "main > section:nth-child(2)"). Combine --selector with --full to capture an element's full scrollable height. Use --selector-all to screenshot every matching element as numbered PNGs — elements that fail or timeout are skipped (use --timeout <ms> to control per-element timeout, default 30s). Without --file, returns base64-encoded image data.

Debugging Commands

Command	Description
atr browser console [--limit N]	Get console messages (default: 50)
atr browser network [--limit N]	Get network requests (default: 50)
atr browser errors	Get failed requests

Workflow Pattern

Follow this workflow for browser automation tasks:

1. Ensure Server Running

   atr browser status || atr browser start
   

2. Navigate to Target

   atr browser navigate https://example.com
   

3. Inspect Page Elements

   atr browser snapshot
   

   This returns elements with unique IDs (UIDs) like e0, e1, etc.

4. Interact with Elements Target elements by:

   • Text content: "Sign In"
   • UID from snapshot: e5
   • CSS selector: .submit-button

5. Verify Results

   atr browser url
   atr browser title
   atr browser screenshot --file
   

6. Cleanup When Done

   atr browser stop
   

Asking Questions About a Page

Use atr browser ask when you need specific information from a page without flooding your context with raw HTML or snapshot data. A lightweight sub-agent inspects the page using multiple tools and returns a concise text answer.

atr browser ask "What is the main heading on this page?"
atr browser ask "How many items are in the navigation menu?"
atr browser ask "Is there a login form on this page?"

Prefer ask over html or snapshot when:

• You need a specific fact, not the full page structure
• You want to keep your context clean for subsequent reasoning
• The answer can be expressed as a short text response

Recording Browser Interactions

Use atr browser record to capture user interactions and output a .test.txt behavior test file. A floating overlay appears in the browser showing recorded steps in real time.

# Record interactions on a page
atr browser record --url https://example.com -o repro-steps.test.txt

# Record on the already-open page
atr browser record -o flow.test.txt

Stop recording with Ctrl+C in the terminal or the "Stop" button in the browser overlay.

The recorder captures clicks, form fills, keyboard shortcuts, navigation, scrolling, and select changes. It handles shadow DOM (web components) and generates stable CSS selectors. Password fields are automatically masked.

The output .test.txt file can be replayed with atr run --behavior repro-steps.test.txt.

Using JSON Output

Add --json flag for structured output when parsing is needed:

atr browser snapshot --json
atr browser list-pages --json
atr browser network --json

Element Targeting

The <target> parameter in click, fill, hover, and drag commands accepts:

1. Element UID: e0, e5 (from snapshot output)
2. Visible text: "Sign In", "Submit Form"
3. aria-label: Elements with matching aria-label attribute
4. data-testid: Elements with matching data-testid attribute
5. CSS selector: #login-button, .nav-link, header, footer, nav, main > section, div.hero, li:nth-child(2)

Best practice: Use atr browser snapshot first to see available elements and their UIDs.

Keyboard Keys

For press-key command:

• Named keys: Enter, Tab, Escape, Backspace
• Modifiers: Control+a, Shift+Tab, Alt+Enter
• Arrow keys: ArrowUp, ArrowDown, ArrowLeft, ArrowRight

Troubleshooting

Browser won't start:

atr browser status
rm ~/.atr/browser.state  # If stale state
atr browser start

Port already in use:

atr browser start --port 9334

Element not found:

atr browser snapshot --verbose --json

Additional Resources

For complete command reference with all flags, see references/commands-reference.md.