[catgirlinspace]

Could’ve been the built in optimized battery charging where it stays at 80% until about when it think it’ll be needed (based off of previous usage on battery tmk, but i wouldn’t be surprised if it also looks at the native calendar app or something too) at which point it charges to 100%. Apple has been doing it for years on iPhones and i think it was introduced on Mac when Apple silicon happened.

For me my MacBook stays at 80% through the evening and night before charging to 100% in the morning when I typically unplug it and put it in my bag. If you open the battery thing in the menu bar it shows when it’s doing this, the time it’s scheduled to be finished charging by, and has a little button to charge to 100% immediately.