LaunchRepoDefinition
The Chrome DevTools Protocol (CDP) is the interface Chrome exposes for tooling: the same channel the built-in developer tools use, made available to other programs over a local WebSocket. With it a program can open tabs, navigate, read the DOM, dispatch input and take screenshots.
Since Chrome 136 the browser ignores the legacy remote-debugging flags for its default user-data directory, so a driven Chrome needs either the remote-debugging control on the inspect page (Chrome 144+) or a dedicated user-data directory with its own port.
Sources: Chrome DevTools Protocol · Chrome for Developers: Changes to remote debugging switches · chrome-devtools-mcp: configuration
Example
You use Chrome 144 or newer. You open chrome://inspect/#remote-debugging, enable remote debugging and start Chrome DevTools MCP with --autoConnect. Chrome asks whether to allow the connection; you approve it in the window you intend to use, and the agent can now list and drive your open tabs.
If you prefer isolation, or your Chrome is older, you start a second Chrome with its own user-data directory on port 9222 and point the MCP server at http://127.0.0.1:9222. The legacy flag alone no longer works on your everyday profile since Chrome 136. Both commands are below.
# Mode A: Chrome 144+, remote debugging enabled on chrome://inspect/#remote-debugging
npx -y chrome-devtools-mcp@latest --autoConnect
# Mode B: dedicated profile on a loopback port
"<path to Chrome>" --remote-debugging-port=9222 --user-data-dir="$PWD/.browser/chrome" about:blank
npx -y chrome-devtools-mcp@latest --browserUrl=http://127.0.0.1:9222Why it matters for a directory launch
CDP is what turns the browser you are signed in to into something an agent can operate. That is also why it deserves care: a debugging port controls the whole browser, including authenticated pages. Keeping it on the loopback address, never tunneling it and closing it after a batch are part of the setup, not optional hardening.
How LaunchRepo handles it
BROWSER-SETUP.md offers two modes. A: enable remote debugging on chrome://inspect in Chrome 144+ and let Chrome DevTools MCP auto-connect, approving the connection prompt in the intended window. B: launch a dedicated Chrome with its own user-data directory on 127.0.0.1:9222 and point the MCP server at that URL. Never both at once, never a public port, and the visible tab has to move before a running process counts as access.
Go deeper
Connect your coding agent to your Chrome
Both connection modes step by step, the smoke check on a public page and how to close the debugging port after a batch.
See the term in the repository
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