Upgraded my M3 iMac (16GB/1TB) to Tahoe 26.0.1 yesterday. Used it early this morning for a couple of hours then put it to sleep by pressing the Touch ID button. Woke it up 4 hours later and saw an error message I've never seen before... somehow my Messages app was using 47GB (!!!) and everything had "paused" as a result. I did a hard restart and everything seems fine again. A half-hour later Messages is happy at 186MB. Not necessarily blaming this on Tahoe 26.0.1 but I've been using Macs since 2003 and this is the first time this has ever happened -- barely 24 hours after installing the update. Just sayin'.
PS -- The error is "Your system has run out of application memory."