What is a Bridge OS T2-initiated shutdown?

Does anyone know what a Bridge OS T2-initiated shutdown is? I was sitting at my desk playing video games with my cousin when I saw my Mac Mini suddenly restart. Curious I tried to search the logs for a previous shutdown cause and got a “-20” code.

BridgeOS is the operating system that runs on the T2 chip. The T2 starts before the main Intel CPU and is best known for dealing with hardware security, but it also does some other functions dealing with low-level hardware including power and thermals.

I’m not sure what that error message is for, but it must’ve have noticed some inconsistencies or errors and forced a full system restart.

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Is this a 24/7 running Mac, or are you shouting the Mac down (not SleepMode) daily?

I do not shut it down daily. I usually just let it sleep.

Thank you! This is helpful.

Yes, that was my bet.
I made the experience, that shutdowns like this increase with the time the system is continuously running.
I therefore have a recurring point on my GTD List every 3 days, to restart my Macs, which is quickly done, and prevents for me uncontrolled shutdowns like this, since I do so.

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Ah thank you. Not sure why it is doing this but this is a helpful resolution.

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I’ve had hardware problems (bad memory in both cases, I think) that would result in random crashes/restarts and show up in the logs with all kinds of messages about BridgeOS. If it happens repeatedly and the machine is still covered by Apple Care, you may want to have that checked out.

For more trivia fun BridgeOS is a stripped down version of WatchOS and the T2 is an A7 respin with additional security features.

I see these too on my iMac Pro. It’s always when the system enters sleep mode. They’re typically at least a week apart (sometimes months) so I guess the more frequent restarts would address the symptom, but I’d still like to know the cause. This machine was, unfortunately, purchased long enough ago that it wasn’t possible to get Apple Care extended, so taking it in isn’t really a viable option.

I do not know the reason, but it might be from the same type, as it is a good advise to have a run of FirstAid on your Drives from time to time, to sort out some failures that might add on there, too.

I startet this “Restart-Thing” with all of my 24/7 electronic devices some time ago.
This included my NAS, my HomeControl, my Phones and so on, and I have way less problems with all of those devices since I startet that, so it is not an Apple-Alone-Thing, but seems to be valid for all kind of computer operated devices.
Maybe there is some kind of “Electronic-Plaque” building up during operation hours, that is removed thru a restart, but results into problems if it is building up too much over a period of time.