I set iOS 26 to install overnight, put my iPhone 16 Pro on the MagSafe charger, watched it charge just fine, and went to sleep. When I woke up the iPhone showed the “plug into power” dead battery screen. I took it off MagSafe and put it back on. A half hour later the phone was warm but still wouldn’t power on, just showed the battery screen with a little red in it. I took it off MagSafe and plugged it into my iPad charging brick with USB cable to give it more power, still it did not turn on. I tried holding all the buttons to try to force a restart but didn’t work.
For anyone else encountering this, do this to enter DFU mode and restore it. I had to do it a few times before I got the timing right.
Plug into your Mac and open Finder (or apparently a PC with Apple Devices or iTunes)
Press and quickly release volume up
Press and quickly release volume down
Press and hold right side button
When the battery disappears and screen goes black, hold volume down and continue holding side button
After a couple seconds release the side button and continue holding volume down
A prompt to allow connecting to the iPhone should appear after a couple seconds, click Allow, and it’ll say the iPhone entered DFU mode - proceed to restore the firmware