Cron Dark Mode Webcam Limitations

Cron Dark Mode Webcam Limitations | Generated by AI

Home 2026.06

Here’s the full picture:

Your crontab:

*/10 * * * * /opt/homebrew/bin/ww appearance smart-auto
0 * * * * /opt/homebrew/bin/ww projects update

What smart-auto does (appearance.py line 96-181):

Captures a webcam photo via imagesnap or ffmpeg
Analyzes average luminance (numpy/PIL)
If brightness < 80/255 → dark mode; otherwise → light mode

When lid is closed — it will FAIL for two reasons:

macOS sleeps by default when lid closes. Cron jobs don’t execute during sleep. The */10 cron simply won’t fire unless you’ve disabled sleep (sudo pmset -a disablesleep 1) or the machine is connected to an external display/keyboard in clamshell mode.
Webcam is physically inaccessible. Even if the machine stays awake (clamshell mode with external display), the built-in FaceTime camera on MacBook Air M2 is disabled when the lid is closed. imagesnap / ffmpeg will fail with a capture error, and the script exits with code 1 at line 158-160:
```
Error capturing webcam: ...
Make sure a webcam is connected and not in use by another app.
```

Bottom line: The cron job will NOT succeed with the lid closed. It needs both an awake machine AND an accessible webcam.

If you want it to work in clamshell mode, you’d need an external webcam connected, and the machine must not sleep. Alternatively, if the goal is just time-based dark/light switching, the built-in ww appearance auto (sunrise/sunset) doesn’t need a webcam at all — you could swap the cron to use that instead.

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