iOS Observe Call State Logs via heard daemon (accessibility service) - ios

Question

I am doing some iPhone automation and want to observe call states of ongoing calls. I implemented a listener to read the idevicesyslog and fetch log output of com.apple.accessibility.heard, which is printing each state change similar to the following lines (stat=Sending and stat=Active):
ay 13 02:14:02 heard(HearingUtilities)[11392] <Notice>: -[HUComfortSoundsController callStatusDidChange:]:415 Phone call holding 0 [pending = 1, active = 0, avc = 0, endpoint = 1] - NSConcreteNotification 0x102f173f0 {name = TUCallCenterCallStatusChangedNotification: object = <TUProxyCall 0x102f47080 p=com.apple.coretelephony aPI=(null) svc=Telephony hdl=<TUHandle 0x103407870 type=PhoneNumber, value=+4912345, normalizedValue=+4912345, isoCountryCode=de> isoCC=de stat=Sending tStat=0 dR=0 fR=0 supportsR=1 uPI=57FCA1D2-D09F-4E23-A08A-3AD4B18B570D grp=(null) lSIUUID=00000000-0000-0000-0000-000000000001 lSIAccountUUID=AA1FC9E6-068E-4D86-B3B9-C1074658AFB2 hosted=1 endpt=1 callerNFN=(null) srcID=(null) aC=(null) aM=(null) iUB=1 vm=0 connStat=00 nMICS=0 sR=0 iSA=0 iSV=0 iSS=0 wHM=0 hSI=0 vST=0 iapST=0 oapST=0 vCA=<TUVideoCallAttributes 0x102f17330 remoteCameraOrientation=0 localVideoContextSlotIdentifier=0 remoteVideoContextSlotIdentifier=0> model=<TUCallModel 0x102f3e380 hold=1 grp=1 ungrp=1 DTMF=1 uMPS=1 aC=1 sTV=0> em=0 iFE=0 sos=0 sSR=1 sSUI=0 mX=0<\M-b\M^#\M-&>
May 13 02:14:14 heard(HearingUtilities)[11392] <Notice>: -[HUComfortSoundsController callStatusDidChange:]:415 Phone call holding 0 [pending = 0, active = 1, avc = 1, endpoint = 1] - NSConcreteNotification 0x10321ab80 {name = TUCallCenterCallStatusChangedNotification: object = <TUProxyCall 0x102f47080 p=com.apple.coretelephony aPI=(null) svc=Telephony hdl=<TUHandle 0x103330670 type=PhoneNumber, value=+4912345, normalizedValue=+4912345, isoCountryCode=de> isoCC=de stat=Active tStat=0 dR=0 fR=0 supportsR=1 uPI=57FCA1D2-D09F-4E23-A08A-3AD4B18B570D grp=(null) lSIUUID=00000000-0000-0000-0000-000000000001 lSIAccountUUID=AA1FC9E6-068E-4D86-B3B9-C1074658AFB2 hosted=1 endpt=1 callerNFN=(null) srcID=(null) aC=AVAudioSessionCategoryPhoneCall aM=(null) iUB=1 vm=0 connStat=11 nMICS=0 sR=0 iSA=0 iSV=0 iSS=0 wHM=0 hSI=1 vST=0 iapST=0 oapST=0 vCA=<TUVideoCallAttributes 0x102f17330 remoteCameraOrientation=0 localVideoContextSlotIdentifier=0 remoteVideoContextSlotIdentifier=0> model=<TUCallModel 0x1032596b0 hold=1 grp=1 ungrp=1 DTMF=1 uMPS=1 aC=1 sTV=1> em=0 iFE=0<\M-b\M^#\M-&>
Unfortunately, starting from newer iOS versions (maybe 15.4 or 15.x already, don't know exactly), the heard service is killing itself after 3 minutes:
May 13 02:28:03 heard(Accounts)[11501] <Notice>: "The connection to ACDAccountStore was invalidated."
May 13 02:28:03 heard(Accounts)[11501] <Notice>: "The connection to ACDAccountStore was invalidated."
May 13 02:30:21 heard(HearingUtilities)[11501] <Notice>: -[AXHeardController shutdownIfPossible]:355 heard still shouldn't be running. Shutting down.
It is restarting after i am opening the settings-> accessibility settings via phone menu. Does anybody have an idea what I can do about this? I thought about following things:
Include heard service / accessibility in an own app, so that it will stay online when app is active
Get call states in another way? I tried an observer inside an app, but when it is running in background, it will not react anymore.
Some iOS setting to enable it permanently
Will this be fixed in an upcoming version?
The com.apple.accessibility.heard seems to be an internal service, does anybody know how to deal with it now?
Otherwise i would also be happy for a hint how to solve this without observing logs. As I said, CallObserver in my swift app is problematic, as it is not working in background.