Chrome cdp setup

Chrome CDP Setup (macOS Dock launcher)

Makes the Dock's Chrome icon launch Chrome with --remote-debugging-port so any local agent can connect over CDP. Chrome 136+ silently ignores that flag on the default profile directory, so the launcher points Chrome at a one-time APFS clone of the real profile — all logins, bookmarks, and extensions carry over at near-zero disk cost.

Scripts live in this skill's scripts/ dir; run them with absolute paths (~/.claude/skills/chrome-cdp-setup/scripts/...).

Quick start

scripts/setup_chrome_cdp.sh              # full setup (default port 9222)
scripts/verify_cdp.sh                    # endpoint + loopback + flags health check
uv run --with playwright python scripts/cdp_agent_test.py   # external-agent smoke test

Setup workflow

1. Preflight: confirm /Applications/Google Chrome.app exists and /Applications is writable; note profile size with du -sh ~/Library/Application\ Support/Google/Chrome.
2. Run scripts/setup_chrome_cdp.sh [port]. It is idempotent and:
   • quits Chrome cleanly (session restores on relaunch)
   • clones ~/Library/Application Support/Google/Chrome → Chrome-CDP (cp -Rc; skipped if the clone already exists)
   • builds /Applications/Google Chrome CDP.app (Chrome's own icon, ad-hoc signed)
   • swaps the Dock's Chrome tile for the wrapper (Dock prefs backed up first) and restarts the Dock
   • launches the wrapper and waits for http://127.0.0.1:<port>/json/version
3. Confirm with scripts/verify_cdp.sh [port] — expect version JSON plus a 127.0.0.1:<port> (LISTEN) line.
4. Prove end-to-end with cdp_agent_test.py — it connects from an independent process, lists the real tabs, opens its own tab, rewrites the DOM, screenshots, and disconnects leaving Chrome running.

Connecting agents

• Playwright: chromium.connect_over_cdp("http://127.0.0.1:9222")
• Puppeteer: puppeteer.connect({ browserURL: "http://127.0.0.1:9222" })
• Raw WS: re-fetch webSocketDebuggerUrl from /json/version each launch (it rotates).
• Python agents need only pip install playwright or uv run --with playwright — no playwright install browser download, since they attach to the running Chrome.

Rules that prevent breakage

• Always start Chrome from the Dock icon. Spotlight, Chrome's "Relaunch to update", or a link click while Chrome is closed all launch the non-CDP default-profile instance — quit it and relaunch from the Dock.
• Never run both instances at once (session divergence, duplicate extension connections).
• The CDP server takes a few seconds after launch: poll with curl --retry 30 --retry-delay 1 --retry-all-errors.
• The active profile may be Profile N, not Default — read profile.last_used from the clone's Local State before asserting the clone is broken.
• Loopback only: never add --remote-debugging-address. Any local process can drive the browser and read that profile's cookies — the machine is the trust boundary.

Details

Gotchas, troubleshooting, raw-CDP notes, and revert steps: see REFERENCE.md.