browser-auth

Chrome DevTools MCP — Browser Authentication Patterns

Use the Chrome DevTools MCP server to interact with authenticated web pages (Buildkite, AWS Console, GitHub, etc.) through the user's existing Chrome browser session.

Prerequisites

• Chrome 144+ installed (check chrome://version)
• Chrome DevTools MCP configured in OpenCode (see Configuration below)
• User logged into target sites in their Chrome browser

Configuration

The MCP server is configured in ~/.config/opencode/opencode.json:

{
  "mcp": {
    "chrome-devtools": {
      "type": "local",
      "command": ["npx", "-y", "chrome-devtools-mcp@latest", "--autoConnect"]
    }
  }
}

Connection Modes

Mode	Config	When to Use
--autoConnect	Connects to running Chrome via DevTools discovery	Recommended. Uses existing browser with cookies/sessions. Requires Chrome 144+ and enabling remote debugging in chrome://inspect/#remote-debugging.
--browserUrl	--browserUrl http://127.0.0.1:9222	When Chrome is launched with --remote-debugging-port=9222. Requires restarting Chrome with the flag.
(default)	No flags	Launches a fresh Chrome instance with no cookies, extensions, or password manager. Not suitable for authenticated pages.

Enabling --autoConnect

1. Open Chrome
2. Navigate to chrome://inspect/#remote-debugging
3. Enable the "Allow remote debugging connections" toggle
4. Restart OpenCode so the MCP server reconnects

Using --browserUrl (Alternative)

If --autoConnect doesn't work, restart Chrome with the debugging port:

# Quit Chrome first, then relaunch:
/Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome \
  --remote-debugging-port=9222 \
  --user-data-dir="$HOME/Library/Application Support/Google/Chrome"

Update the MCP config:

"command": ["npx", "-y", "chrome-devtools-mcp@latest", "--browserUrl", "http://127.0.0.1:9222"]

Note: On macOS, --remote-debugging-port requires --user-data-dir to be explicitly set (even if it's the default path). Without it, Chrome prints "DevTools remote debugging requires a non-default data directory" and the debugging server does not start.