Kernel Agent Browser

Agent-Browser with Kernel Cloud Browsers

This skill documents best practices for using agent-browser's built-in Kernel provider (-p kernel) for cloud browser automation.

When to Use This Skill

Use this skill when you need to:

• Automate websites using agent-browser -p kernel commands
• Handle bot detection on sites with aggressive anti-bot measures
• Persist login sessions across automation runs using profiles
• Work with iframes including cross-origin payment forms
• Get live view URLs for debugging or manual intervention
• Find the underlying Kernel session ID for advanced Playwright scripting
• Create site-specific automation skills for new websites

References

• Creating Site-Specific Skills - Guide for building automation skills for specific websites

Prerequisites

Load the kernel-cli skill for Kernel CLI installation and authentication.

Environment Variables

Set these before your first agent-browser -p kernel call. The CLI holds state between invocations.

Recommended Configuration

export KERNEL_API_KEY="your-api-key"
export KERNEL_TIMEOUT_SECONDS=600     # 10-minute timeout for complex workflows
export KERNEL_STEALTH=true            # Avoid bot detection (default)
export KERNEL_PROFILE_NAME=mysite     # Persist login sessions across runs

Profile Persistence

When KERNEL_PROFILE_NAME is set:

• The profile is created if it doesn't exist
• Cookies, logins, and session data are automatically saved when the browser session ends
• Future sessions with the same profile name restore the saved state

This is especially useful for sites requiring login—authenticate once, reuse across sessions.

Basic Usage

agent-browser -p kernel open <url>        # Navigate to page
agent-browser -p kernel snapshot -i       # Get interactive elements with refs
agent-browser -p kernel click @e1         # Click element by ref
agent-browser -p kernel fill @e2 "text"   # Fill input by ref
agent-browser -p kernel close             # Close browser and save profile

Always use the -p kernel flag with each command.

Semantic Selectors (Recommended)

Instead of ephemeral @e refs that change on every page load, use semantic selectors via the find command for more stable, readable automation:

# By ARIA role + accessible name (most stable)
agent-browser -p kernel find role button click --name "Log In"
agent-browser -p kernel find role textbox fill "user@email.com" --name "Email"

# By visible text content
agent-browser -p kernel find text "View Menus" click
agent-browser -p kernel find text "Submit Order" click

# By form label (great for inputs)
agent-browser -p kernel find label "Username" fill "myuser"
agent-browser -p kernel find label "Password" fill "secret123"

# By placeholder text
agent-browser -p kernel find placeholder "Search..." type "query"

# By data-testid (if the site uses them)
agent-browser -p kernel find testid "submit-btn" click

# By position (when needed)
agent-browser -p kernel find first "li.item" click
agent-browser -p kernel find nth 2 ".card" hover

When to Use Which Selector

Recommendation: Use find for production automation. Use @e refs for exploration and quick prototyping, then convert to semantic selectors.

Finding Session ID and Live View URL

agent-browser creates a Kernel browser session under the hood. To get the session ID or live view URL:

# List all Kernel browsers (find yours by profile name or creation time)
kernel browsers list

# Get live view URL for a specific session
kernel browsers view <session-id>

This is useful when:

• You need to execute Playwright scripts directly against the session
• You want to share a live view URL with the user for manual intervention
• You're debugging and want to watch the browser in real-time

Handling Bot Detection

Stealth Mode

Stealth mode (KERNEL_STEALTH=true) is enabled by default and helps avoid detection. However, some sites have aggressive bot detection that still triggers.

Manual Login Fallback

If login automation fails due to bot detection:

1. Get the live view URL:

   kernel browsers list
   # Find your session by profile name
   kernel browsers view <session-id>
   

2. Share the live view URL with the user and ask them to complete the login manually

3. Once logged in, continue automation—the profile will save the authenticated state

JavaScript Fallback for Tricky Elements

Some elements (especially on bot-protected sites) don't respond to standard commands:

# Click by CSS selector
agent-browser -p kernel eval "document.querySelector('.submit-btn').click()"

# Fill by selector (with event dispatch)
agent-browser -p kernel eval "
  const el = document.querySelector('#email');
  el.value = 'user@example.com';
  el.dispatchEvent(new Event('input', {bubbles: true}));
  el.dispatchEvent(new Event('change', {bubbles: true}));
"

# Click by test ID
agent-browser -p kernel eval "document.querySelector('[data-testid=\"submit\"]').click()"

Anti-Bot Form Fields

Some payment processors (e.g., Point and Pay) use decoy form fields. Only fill fields matching specific patterns:

agent-browser -p kernel eval "
  const realInputs = Array.from(document.querySelectorAll('input'))
    .filter(el => el.name && el.name.startsWith('xeiinput'));
  // Fill only these inputs
"

Handling Iframes

Same-Origin Iframes

Use the frame command to switch context:

agent-browser -p kernel frame "#iframe-id"   # Switch to iframe
agent-browser -p kernel snapshot -i          # Snapshot within iframe
agent-browser -p kernel click @e1            # Interact within iframe
agent-browser -p kernel frame main           # Return to main frame

Cross-Origin Iframes

Cross-origin iframes require executing a Playwright script directly against the Kernel session:

1. Find the session ID:

   kernel browsers list
   

2. Execute a Playwright script:

   kernel browsers exec <session-id> --code "
     const frame = page.frameLocator('#payment-iframe');
     await frame.locator('#card-number').fill('4111111111111111');
     await frame.locator('#submit').click();
   "
   

See the kernel-cli skill for more details on executing Playwright code.

Waiting Strategies

Smart waits are critical for fast, reliable automation. Using condition-based waits instead of fixed timeouts can reduce execution time by 50%+ while improving reliability.

Smart Waits (Recommended)

# Wait for page load states
agent-browser -p kernel wait --load domcontentloaded  # DOM ready
agent-browser -p kernel wait --load networkidle       # Network settled

# Wait for specific URL pattern (great for redirects after login)
agent-browser -p kernel wait --url "**/dashboard"
agent-browser -p kernel wait --url "**/order-confirmation"

# Wait for text to appear (great for dynamic content)
agent-browser -p kernel wait --text "Password"        # Field appeared
agent-browser -p kernel wait --text "Order confirmed" # Success message

# Wait for JavaScript condition
agent-browser -p kernel wait --fn "window.appReady === true"
agent-browser -p kernel wait --fn "document.querySelector('.spinner') === null"

# Wait for element by CSS selector
agent-browser -p kernel wait "#login-form"
agent-browser -p kernel wait ".results-loaded"

Fixed Waits (Last Resort)

# Only when no condition is available
agent-browser -p kernel wait 2000

Element Refs Best Practices

Element refs (@e1, @e2, etc.) are ephemeral and change:

• After page navigation
• After significant DOM updates
• Between browser sessions

Always take a fresh snapshot before interacting:

agent-browser -p kernel snapshot -i
# Now use the refs from this snapshot
agent-browser -p kernel click @e5

Filtering Snapshots

# Filter for specific elements
agent-browser -p kernel snapshot -i | grep -i "button\|submit"

# Scope to a specific area
agent-browser -p kernel snapshot -s "#main-content" -i

Login Patterns

Single-Page Form (Optimized)

Username and password on the same page:

agent-browser -p kernel open https://example.com/login
agent-browser -p kernel wait --load domcontentloaded

# Use semantic selectors for stability
agent-browser -p kernel find label "Email" fill "user@example.com"
agent-browser -p kernel find label "Password" fill "secret123"
agent-browser -p kernel find role button click --name "Sign In"

# Wait for actual redirect, not arbitrary timeout
agent-browser -p kernel wait --url "**/dashboard"

Two-Step Form (Optimized)

Username first, then password on a second screen:

agent-browser -p kernel open https://example.com/login
agent-browser -p kernel wait --load domcontentloaded

# Step 1: Username
agent-browser -p kernel find label "Username" fill "myuser"
agent-browser -p kernel press Enter

# Wait for password field to appear (not a fixed sleep!)
agent-browser -p kernel wait --text "Password"

# Step 2: Password
agent-browser -p kernel find label "Password" fill "secret123"
agent-browser -p kernel press Enter

# Wait for successful redirect
agent-browser -p kernel wait --url "**/home"

Comparison: Old vs Optimized

# OLD (slow, fragile):
agent-browser -p kernel wait 2000
agent-browser -p kernel fill @e1 "username"
agent-browser -p kernel wait 2000
agent-browser -p kernel fill @e3 "password"
agent-browser -p kernel wait 5000

# OPTIMIZED (fast, stable):
agent-browser -p kernel wait --load domcontentloaded
agent-browser -p kernel find label "Username" fill "username"
agent-browser -p kernel wait --text "Password"
agent-browser -p kernel find label "Password" fill "password"
agent-browser -p kernel wait --url "**/dashboard"

Modal Login

Login form appears in a modal overlay:

# Click login link to open modal
agent-browser -p kernel find text "Log In" click
agent-browser -p kernel wait --text "Password"  # Wait for modal

# Fill modal fields
agent-browser -p kernel find label "Email" fill "user@example.com"
agent-browser -p kernel find label "Password" fill "password123"
agent-browser -p kernel find role button click --name "Sign In"
agent-browser -p kernel wait --url "**/dashboard"

Fallback: JavaScript for Tricky Modals

Some modals don't expose accessible labels:

agent-browser -p kernel eval "document.querySelector('.login-link').click()"
agent-browser -p kernel wait 1000

agent-browser -p kernel eval "
  document.getElementById('username').value = 'user@example.com';
  document.getElementById('username').dispatchEvent(new Event('input', {bubbles: true}));
  document.getElementById('password').value = 'password123';
  document.getElementById('password').dispatchEvent(new Event('input', {bubbles: true}));
  document.querySelector('button[type=submit]').click();
"
agent-browser -p kernel wait --url "**/dashboard"

Handling New Tabs

Some links open in new tabs:

# Click link that opens new tab
agent-browser -p kernel click @e38
agent-browser -p kernel tab 1           # Switch to new tab (0-indexed)
agent-browser -p kernel wait 2000
agent-browser -p kernel snapshot -i     # Interact with new tab

Screenshots and Debugging

# Take screenshot
agent-browser -p kernel screenshot ~/Downloads/page.png

# Full page screenshot
agent-browser -p kernel screenshot ~/Downloads/full.png --full

# View console messages
agent-browser -p kernel console

# View page errors
agent-browser -p kernel errors

# Get current URL
agent-browser -p kernel get url

Session Management

Cleanup

Always close the browser when done to save the profile:

agent-browser -p kernel close

Multiple Sessions

Run parallel browser sessions with named sessions:

agent-browser -p kernel --session site1 open https://site1.com
agent-browser -p kernel --session site2 open https://site2.com
agent-browser -p kernel session list

Common Gotchas

1. Refs change after navigation: Always re-snapshot after clicking links or submitting forms.

2. Wait after actions: Add waits after clicks/submits that trigger page loads or AJAX.

3. Profile not saving: Make sure to run agent-browser -p kernel close to save the profile state.

4. Timeout too short: Increase KERNEL_TIMEOUT_SECONDS for workflows with user pauses or slow pages.

5. Stealth not working: Some sites detect bots despite stealth. Use manual login fallback.

6. eval for stubborn elements: If fill or click don't work, try eval with direct DOM manipulation.

7. Cross-origin iframes: Can't interact via agent-browser commands. Use Kernel's Playwright execution.

Quick Reference

# Start session with profile persistence
export KERNEL_PROFILE_NAME=mysite
export KERNEL_TIMEOUT_SECONDS=600
agent-browser -p kernel open https://example.com

# Basic interaction with semantic selectors (recommended)
agent-browser -p kernel wait --load domcontentloaded
agent-browser -p kernel find label "Email" fill "user@example.com"
agent-browser -p kernel find label "Password" fill "secret"
agent-browser -p kernel find role button click --name "Submit"
agent-browser -p kernel wait --url "**/success"

# Alternative: snapshot + refs (for exploration)
agent-browser -p kernel snapshot -i
agent-browser -p kernel fill @eN "text"
agent-browser -p kernel click @eM

# Get session info for manual intervention
kernel browsers list
kernel browsers view <session-id>

# Cleanup
agent-browser -p kernel close

Selector Cheat Sheet

# Buttons and links
agent-browser -p kernel find role button click --name "Submit"
agent-browser -p kernel find role link click --name "Next"
agent-browser -p kernel find text "Click here" click

# Form inputs
agent-browser -p kernel find label "Email" fill "user@example.com"
agent-browser -p kernel find placeholder "Search" type "query"
agent-browser -p kernel find testid "username-input" fill "myuser"

# Smart waits
agent-browser -p kernel wait --load domcontentloaded
agent-browser -p kernel wait --text "Success"
agent-browser -p kernel wait --url "**/dashboard"
agent-browser -p kernel wait --fn "window.loaded === true"

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