# Chrome CDP Launch Procedure

## Chrome 151+ Breaking Change

Chrome 151+ requires `--remote-allow-origins=*` for WebSocket connections to CDP.
Without it: `Handshake status 403 Forbidden - Rejected an incoming WebSocket connection`.

## Full Launch Command (Windows)

```bash
# Kill existing Chrome instances
taskkill /F /IM chrome.exe 2>/dev/null

# Launch with CDP enabled
"C:\Program Files\Google\Chrome\Application\chrome.exe" \
  --remote-debugging-port=9222 \
  --remote-allow-origins=* \
  --user-data-dir=%USERPROFILE%/.chrome-cdp-profile \
  --no-first-run \
  --no-default-browser-check
```

## Verify CDP is alive

```bash
curl -s http://127.0.0.1:9222/json/version
# Expected: {"Browser": "Chrome/151.0.7922.109", ...}
```

## Python: kill + launch

```python
import subprocess, time, os

subprocess.run(['taskkill', '/F', '/IM', 'chrome.exe'], capture_output=True)
time.sleep(2)

user_data = os.path.expanduser("~/.chrome-cdp-profile")
os.makedirs(user_data, exist_ok=True)

subprocess.Popen([
    r"C:\Program Files\Google\Chrome\Application\chrome.exe",
    f'--user-data-dir={user_data}',
    '--remote-debugging-port=9222',
    '--remote-allow-origins=*',
    '--no-first-run',
    '--no-default-browser-check',
], stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
```

## Python: health check

```python
import urllib.request, json

try:
    resp = urllib.request.urlopen("http://127.0.0.1:9222/json/version", timeout=3)
    data = json.loads(resp.read())
    print(f"CDP OK: {data.get('Browser', 'unknown')}")
except Exception as e:
    print(f"CDP DEAD: {e}")
```

## Common Errors

| Error | Cause | Fix |
|-------|-------|-----|
| `403 Forbidden` on WebSocket | Chrome 151+ without `--remote-allow-origins` | Add `--remote-allow-origins=*` |
| `Connection refused` on :9222 | Chrome not launched with `--remote-debugging-port` | Kill all Chrome, relaunch with flag |
| `user-data-dir is already in use` | Another Chrome instance using same profile | Use unique `--user-data-dir` path |
| `taskkill` not finding Chrome | Chrome running as background process | Check with `tasklist /FI "IMAGENAME eq chrome.exe"` |