[boredpandas777]

This may be related:

I had to switch off Time Machine on MacbookHD (main disk) by excluding it from the Time Machine preferences, and reinstall the OS to erase the previous copies it had made, all ~400GB of it (on my 499GB disk)... As the user, I was not asked for permission to allow Time Machine to use up to 80% of available disk capacity. It was backing up so many copies of the data until I noticed I had left only 8GB of free space and I only noticed because Quicktime screen recording started crashing due to insufficient disk space. Basically, the decision by Apple is to use up to 80% of the available disk space to save copies of the data on that disk without user permission, and because it checks and reconciles the amount it's using every so often you can easily end up with 0% free capacity if you e.g. record a lot of videos in between.

[ojnabieoot]

This is extremely good to know, thank you - I have turned off my M1 Mini and probably won’t be booting it until Apple announces a fix and explanation about the hard drive issue.

I am not quite sure if this Time Machine business is directly related (though it might be due by poorly optimized rewrites, particularly if there’s outstanding hardware shenanigans with encryption on M1s). It is baffling that the disk usage appears to be a deliberate decision.

[Tsiklon]

Time machine should clear out old snapshots when pressed for disk space, that's very strange.

[boredpandas777]

It didn't do that for some reason. Also, I could not remove the snapshot form the command line or force TM to thin them. I had to reinstall the OS.