Browser Extension Builder

Browser Extension Builder

Overview

This public intake copy packages plugins/antigravity-awesome-skills-claude/skills/browser-extension-builder from https://github.com/sickn33/antigravity-awesome-skills into the native Omni Skills editorial shape without hiding its origin.

Use it when the operator needs the upstream workflow, support files, and repository context to stay intact while the public validator and private enhancer continue their normal downstream flow.

This intake keeps the copied upstream files intact and uses the external_source block in metadata.json plus ORIGIN.md as the provenance anchor for review.

Browser Extension Builder Expert in building browser extensions that solve real problems - Chrome, Firefox, and cross-browser extensions. Covers extension architecture, manifest v3, content scripts, popup UIs, monetization strategies, and Chrome Web Store publishing. Role: Browser Extension Architect You extend the browser to give users superpowers. You understand the unique constraints of extension development - permissions, security, store policies. You build extensions that people install and actually use daily. You know the difference between a toy and a tool. ### Expertise - Chrome extension APIs - Manifest v3 - Content scripts - Service workers - Extension UX - Store publishing

Imported source sections that did not map cleanly to the public headings are still preserved below or in the support files. Notable imported sections: Capabilities, Patterns, Extension Architecture, Content Scripts, Storage and State, Extension Monetization.

When to Use This Skill

Use this section as the trigger filter. It should make the activation boundary explicit before the operator loads files, runs commands, or opens a pull request.

• User mentions or implies: browser extension
• User mentions or implies: chrome extension
• User mentions or implies: firefox addon
• User mentions or implies: extension
• User mentions or implies: manifest v3
• Use when the request clearly matches the imported source intent: Expert in building browser extensions that solve real problems -.

Operating Table

Workflow

This workflow is intentionally editorial and operational at the same time. It keeps the imported source useful to the operator while still satisfying the public intake standards that feed the downstream enhancer flow.

1. Confirm the user goal, the scope of the imported workflow, and whether this skill is still the right router for the task.
2. Read the overview and provenance files before loading any copied upstream support files.
3. Load only the references, examples, prompts, or scripts that materially change the outcome for the current request.
4. Execute the upstream workflow while keeping provenance and source boundaries explicit in the working notes.
5. Validate the result against the upstream expectations and the evidence you can point to in the copied files.
6. Escalate or hand off to a related skill when the work moves out of this imported workflow's center of gravity.
7. Before merge or closure, record what was used, what changed, and what the reviewer still needs to verify.

Imported Workflow Notes

Imported: Capabilities

• Extension architecture
• Manifest v3 (MV3)
• Content scripts
• Background workers
• Popup interfaces
• Extension monetization
• Chrome Web Store publishing
• Cross-browser support

Examples

Example 1: Ask for the upstream workflow directly

Use @browser-extension-builder to handle <task>. Start from the copied upstream workflow, load only the files that change the outcome, and keep provenance visible in the answer.

Explanation: This is the safest starting point when the operator needs the imported workflow, but not the entire repository.

Example 2: Ask for a provenance-grounded review

Review @browser-extension-builder against metadata.json and ORIGIN.md, then explain which copied upstream files you would load first and why.

Explanation: Use this before review or troubleshooting when you need a precise, auditable explanation of origin and file selection.

Example 3: Narrow the copied support files before execution

Use @browser-extension-builder for <task>. Load only the copied references, examples, or scripts that change the outcome, and name the files explicitly before proceeding.

Explanation: This keeps the skill aligned with progressive disclosure instead of loading the whole copied package by default.

Example 4: Build a reviewer packet

Review @browser-extension-builder using the copied upstream files plus provenance, then summarize any gaps before merge.

Explanation: This is useful when the PR is waiting for human review and you want a repeatable audit packet.

Best Practices

Treat the generated public skill as a reviewable packaging layer around the upstream repository. The goal is to keep provenance explicit and load only the copied source material that materially improves execution.

• Keep the imported skill grounded in the upstream repository; do not invent steps that the source material cannot support.
• Prefer the smallest useful set of support files so the workflow stays auditable and fast to review.
• Keep provenance, source commit, and imported file paths visible in notes and PR descriptions.
• Point directly at the copied upstream files that justify the workflow instead of relying on generic review boilerplate.
• Treat generated examples as scaffolding; adapt them to the concrete task before execution.
• Route to a stronger native skill when architecture, debugging, design, or security concerns become dominant.

Troubleshooting

Problem: The operator skipped the imported context and answered too generically

Symptoms: The result ignores the upstream workflow in plugins/antigravity-awesome-skills-claude/skills/browser-extension-builder, fails to mention provenance, or does not use any copied source files at all. Solution: Re-open metadata.json, ORIGIN.md, and the most relevant copied upstream files. Check the external_source block first, then restate the provenance before continuing.

Problem: The imported workflow feels incomplete during review

Symptoms: Reviewers can see the generated SKILL.md, but they cannot quickly tell which references, examples, or scripts matter for the current task. Solution: Point at the exact copied references, examples, scripts, or assets that justify the path you took. If the gap is still real, record it in the PR instead of hiding it.

Problem: The task drifted into a different specialization

Symptoms: The imported skill starts in the right place, but the work turns into debugging, architecture, design, security, or release orchestration that a native skill handles better. Solution: Use the related skills section to hand off deliberately. Keep the imported provenance visible so the next skill inherits the right context instead of starting blind.

Related Skills

• @00-andruia-consultant - Use when the work is better handled by that native specialization after this imported skill establishes context.
• @00-andruia-consultant-v2 - Use when the work is better handled by that native specialization after this imported skill establishes context.
• @10-andruia-skill-smith - Use when the work is better handled by that native specialization after this imported skill establishes context.
• @10-andruia-skill-smith-v2 - Use when the work is better handled by that native specialization after this imported skill establishes context.

Additional Resources

Use this support matrix and the linked files below as the operator packet for this imported skill. They should reflect real copied source material, not generic scaffolding.

Imported Reference Notes

Imported: Patterns

Extension Architecture

Structure for modern browser extensions

When to use: When starting a new extension

Imported: Extension Architecture

Project Structure

extension/
├── manifest.json      # Extension config
├── popup/
│   ├── popup.html     # Popup UI
│   ├── popup.css
│   └── popup.js
├── content/
│   └── content.js     # Runs on web pages
├── background/
│   └── service-worker.js  # Background logic
├── options/
│   ├── options.html   # Settings page
│   └── options.js
└── icons/
    ├── icon16.png
    ├── icon48.png
    └── icon128.png

Manifest V3 Template

{
  "manifest_version": 3,
  "name": "My Extension",
  "version": "1.0.0",
  "description": "What it does",
  "permissions": ["storage", "activeTab"],
  "action": {
    "default_popup": "popup/popup.html",
    "default_icon": {
      "16": "icons/icon16.png",
      "48": "icons/icon48.png",
      "128": "icons/icon128.png"
    }
  },
  "content_scripts": [{
    "matches": ["<all_urls>"],
    "js": ["content/content.js"]
  }],
  "background": {
    "service_worker": "background/service-worker.js"
  },
  "options_page": "options/options.html"
}

Communication Pattern

Popup ←→ Background (Service Worker) ←→ Content Script
              ↓
        chrome.storage

Content Scripts

Code that runs on web pages

When to use: When modifying or reading page content

Imported: Content Scripts

Basic Content Script

// content.js - Runs on every matched page

// Wait for page to load
document.addEventListener('DOMContentLoaded', () => {
  // Modify the page
  const element = document.querySelector('.target');
  if (element) {
    element.style.backgroundColor = 'yellow';
  }
});

// Listen for messages from popup/background
chrome.runtime.onMessage.addListener((message, sender, sendResponse) => {
  if (message.action === 'getData') {
    const data = document.querySelector('.data')?.textContent;
    sendResponse({ data });
  }
  return true; // Keep channel open for async
});

Injecting UI

// Create floating UI on page
function injectUI() {
  const container = document.createElement('div');
  container.id = 'my-extension-ui';
  container.innerHTML = `
    <div style="position: fixed; bottom: 20px; right: 20px;
                background: white; padding: 16px; border-radius: 8px;
                box-shadow: 0 4px 12px rgba(0,0,0,0.15); z-index: 10000;">
      <h3>My Extension</h3>
      <button id="my-extension-btn">Click me</button>
    </div>
  `;
  document.body.appendChild(container);

  document.getElementById('my-extension-btn').addEventListener('click', () => {
    // Handle click
  });
}

injectUI();

Permissions for Content Scripts

{
  "content_scripts": [{
    "matches": ["https://specific-site.com/*"],
    "js": ["content.js"],
    "run_at": "document_end"
  }]
}

Storage and State

Persisting extension data

When to use: When saving user settings or data

Imported: Storage and State

Chrome Storage API

// Save data
chrome.storage.local.set({ key: 'value' }, () => {
  console.log('Saved');
});

// Get data
chrome.storage.local.get(['key'], (result) => {
  console.log(result.key);
});

// Sync storage (syncs across devices)
chrome.storage.sync.set({ setting: true });

// Watch for changes
chrome.storage.onChanged.addListener((changes, area) => {
  if (changes.key) {
    console.log('key changed:', changes.key.newValue);
  }
});

Storage Limits

Async/Await Pattern

// Modern async wrapper
async function getStorage(keys) {
  return new Promise((resolve) => {
    chrome.storage.local.get(keys, resolve);
  });
}

async function setStorage(data) {
  return new Promise((resolve) => {
    chrome.storage.local.set(data, resolve);
  });
}

// Usage
const { settings } = await getStorage(['settings']);
await setStorage({ settings: { ...settings, theme: 'dark' } });

Extension Monetization

Making money from extensions

When to use: When planning extension revenue

Imported: Extension Monetization

Revenue Models

Payment Integration

// Use your backend for payments
// Extension can't directly use Stripe

// 1. User clicks "Upgrade" in popup
// 2. Open your website with user ID
chrome.tabs.create({
  url: `https://your-site.com/upgrade?user=${userId}`
});

// 3. After payment, sync status
async function checkPremium() {
  const { userId } = await getStorage(['userId']);
  const response = await fetch(
    `https://your-api.com/premium/${userId}`
  );
  const { isPremium } = await response.json();
  await setStorage({ isPremium });
  return isPremium;
}

Feature Gating

async function usePremiumFeature() {
  const { isPremium } = await getStorage(['isPremium']);
  if (!isPremium) {
    showUpgradeModal();
    return;
  }
  // Run premium feature
}

Chrome Web Store Payments

• Chrome discontinued built-in payments
• Use your own payment system
• Link to external checkout page

Imported: Validation Checks

Using Deprecated Manifest V2

Severity: HIGH

Message: Using Manifest V2 - Chrome requires V3 for new extensions.

Fix action: Migrate to Manifest V3 with service worker

Excessive Permissions Requested

Severity: HIGH

Message: Requesting broad permissions - may cause store rejection.

Fix action: Use specific host_permissions and optional_permissions

No Error Handling in Extension

Severity: MEDIUM

Message: Not checking chrome.runtime.lastError for errors.

Fix action: Check chrome.runtime.lastError after API calls

Hardcoded URLs in Extension

Severity: MEDIUM

Message: Hardcoded URLs may cause issues in production.

Fix action: Use chrome.storage or manifest for configuration

Missing Extension Icons

Severity: LOW

Message: Missing extension icons - affects store listing.

Fix action: Add icons in 16, 48, and 128 pixel sizes

Imported: Collaboration

Delegation Triggers

• react|vue|svelte -> frontend (Extension popup framework)
• monetization|payment|subscription -> micro-saas-launcher (Extension business model)
• personal tool|just for me -> personal-tool-builder (Personal extension)
• AI|LLM|GPT -> ai-wrapper-product (AI-powered extension)

Productivity Extension

Skills: browser-extension-builder, frontend, micro-saas-launcher

Workflow:

1. Define extension functionality
2. Build popup UI with React
3. Implement content scripts
4. Add premium features
5. Publish to Chrome Web Store
6. Market and iterate

AI Browser Assistant

Skills: browser-extension-builder, ai-wrapper-product, frontend

Workflow:

1. Design AI features for browser
2. Build extension architecture
3. Integrate AI API
4. Create popup interface
5. Handle usage limits/payments
6. Publish and grow

Imported: Limitations

• Use this skill only when the task clearly matches the scope described above.
• Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
• Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.