Arc SidePanel Patch

Make chrome.sidePanel extensions work in Arc browser.

Arc never shipped support for the Chrome Side Panel API, so extensions like Claude, Grammarly, and others that use chrome.sidePanel don't work. This project fixes that by injecting a polyfill into every extension at runtime.

Quick Start

# Make sure Arc is running with the debugging port
/Applications/Arc.app/Contents/MacOS/Arc --remote-debugging-port=9222

# Run the patcher (keeps running to catch extension restarts)
npx @dhravya/arc-sidepanel-patcher

Or launch Arc and patch in one command:

npx @dhravya/arc-sidepanel-patcher --launch

Auto-Start on Login

Install globally and set up auto-start so you never have to think about it:

npm install -g @dhravya/arc-sidepanel-patcher

# This creates a macOS LaunchAgent that runs the patcher every time you log in
arc-sidepanel-patcher install

# To remove
arc-sidepanel-patcher uninstall

# Check status
arc-sidepanel-patcher status

How It Works

1. Connects to Arc via Chrome DevTools Protocol (CDP) on port 9222
2. Discovers all extension service workers running in Arc
3. Injects a polyfill that replaces the broken chrome.sidePanel with a working implementation
4. Watches for restarts — when an extension's service worker restarts, the polyfill is re-injected

The polyfill implements the full chrome.sidePanel API surface:

• setOptions() / getOptions()
• setPanelBehavior() / getPanelBehavior()
• open() / close()
• onOpened / onClosed events

Side panels open as popup windows positioned next to the browser window, visually mimicking a sidebar.

For Extension Developers

If you develop a Chrome extension and want it to work in Arc, you can use the polyfill library directly:

npm install @dhravya/chrome-sidepanel-polyfill

import { install } from "@dhravya/chrome-sidepanel-polyfill";

// Only installs if native chrome.sidePanel is missing or broken
install();

// Now use chrome.sidePanel as normal
chrome.sidePanel.setOptions({ path: "sidepanel.html" });

Or load the IIFE bundle in your extension's service worker for zero-config setup:

{
  "background": {
    "service_worker": "service-worker.js",
    "scripts": ["node_modules/@dhravya/chrome-sidepanel-polyfill/dist/index.iife.global.js", "service-worker.js"]
  }
}

CLI Reference

arc-sidepanel-patcher [options]         Run the patcher
arc-sidepanel-patcher install [options] Auto-start on login
arc-sidepanel-patcher uninstall         Remove auto-start
arc-sidepanel-patcher status            Check auto-start status

Options:
  -p, --port <number>  CDP debugging port (default: 9222)
  -l, --launch         Launch Arc with debugging port enabled
  -V, --version        Show version
  -h, --help           Show help

Limitations

• macOS only — Arc is macOS-only
• Requires CDP — Arc must be started with --remote-debugging-port
• Popup windows, not embedded — Side panels open as positioned popup windows rather than embedded iframes (Chrome's internal web_accessible_resources cache prevents the iframe approach for installed extensions)
• Race condition on first inject — The polyfill is injected after the extension's service worker starts, so the initial chrome.sidePanel reference is briefly the broken native one. Works because extensions read chrome.sidePanel lazily at click time, not at init time.

Packages

Development

git clone https://github.com/dhravya/arc-sidepanel-patch
cd arc-sidepanel-patch
pnpm install
pnpm build

License

MIT