The latest macOS developer beta has a new feature to better manage the charge level of recent MacBooks (ones with T3 ports) in order to better preserve battery health.
Basically, if you're plugged in and doing something that generates a lot of heat, like rendering content, it'll ramp down charging to preserve battery health.
The feature will roll out to the public beta soon and to everyone when macOS 15.5.5 ships.
🔌 If you stay plugged in to render a ton of content, leave it on.
🔋 If you’re going on a long plane ride, turn it off
Jason Snell has a good write-up on it, of course: