Watchdog not biting. What is the default RuntimeWatchdogSec in HAOS 14.1?

I’m experiencing random lockups of one of my nodes. It’s a Pi4 running HAOS 14.1 and 2024.12.5. Looking at the backend journal, it just stops. The watchdog doesn’t bite and reboot the Pi as it should after this commit Enable watchdog control in systemd by sbyx · Pull Request #2628 · home-assistant/operating-system · GitHub

The watchdog is configured in /usr/lib/systemd/system.conf.d/watchdog.conf which contains:

[Manager]
RuntimeWatchdogSec=default
WatchdogDevice=/dev/watchdog

Running systemctl show | grep watchdog gets

WatchdogDevice=/dev/watchdog0

but nothing about the timeout. The help: systemd-system.conf shows that RuntimeWatchdogSec needs to be non-zero for the watchdog to be enabled and that its default is defined at compilation time of the kernel.

So, what default is configured in the kernel? And why is the watchdog not biting?

Bump.
I really want to have the watchdog working on my Pi. Something is preventing it and the only thing I can think of is the way buildroot is built.