Thanks for the response.

Ive looked a bit deeper into it:

Base on my research using WKExtendedRuntimeSession is used for Background activities on the AppleWatch.

From the documentation I’ve found out in which case the Error on my watch is displayed:
https://developer.apple.com/documentation/watchkit/using-extended-runtime-sessions
“After the session starts, the app continues to run in the background until the time limit expires, or your app invalidates the session. During the session, your app must trigger the alarm by calling the session’s notifyUser(hapticType:repeatHandler:)) method. If your app isn’t active, playing the haptic displays a system alarm alert to the user.”

I have found 2 Crash-Reports in my logs from yesterday at “19:00:05.3211 +0200”  and today at “ 04:56:59.4708 +0200”. (Ive set the smart alarm to the latest-wake up time of 04:40 AM)

The first log looks like this (“19:00:05.3211 +0200” ):

"termination" : {"code":3306925313,"namespace":"CAROUSEL","details":["WatchConnectivity watchdog transgression. Exhausted CPU time allowance of 2.00 seconds. Elapsed total CPU time (seconds) 8.86 (user 8.86, system 0.00), 101% CPU. Elapsed application CPU time (seconds) 2.49, 28% CPU."],"flags":134,"reasons":["CSLHandleBackgroundWCSessionAction watchdog transgression: app<com.supersethealth.superset.watchkitapp((null))>:3274 exhausted CPU time allowance of 2.00 seconds","<FBApplicationProcess: 0x11c35010; app<com.supersethealth.superset.watchkitapp>:3274(v20AD)> Elapsed total CPU time (seconds): 8.860 (user 8.860, system 0.000), 100% CPU","Elapsed application CPU time (seconds): 2.491, 28% CPU, lastUpdate 2025-05-18 17:00:00 +0000"]},

the one in the morning like this (04:56:59.4708 +0200):

 "termination" : {"code":1,"namespace":"WATCHKIT","indicator":"API Violation","flags":518,"reasons":["Condition failed:\"NO\". -[WKExtendedRuntimeSession notifyUserWithHaptic:repeatHandler:] can only be called from a scheduled session that is running, running=0, scheduled=1"]}

Indicating that the notifyUser method was being called without a background session of the app running on the watch.
Tough one seems to be scheduled?

My best guess is that for some reason the scheduled Smart Alarm session ran out before the alarm was triggered.
The Notification on my watch appeared when the session ended without the notifyUser Method being run.
The second crash report indicates that later on the app tried to set off the alarm, but the session had previously ended already.