I recently upgraded to a macOS 15 and was excited to use iPhone Mirroring. Then the macOS 15.1 betas started coming out and I was too excited to not give Apple Intelligence a try. Unfortunately, the upgrade broke iPhone Mirroring for me. After fifteen minutes to looking, I finally found a solution that worked for me.
TLDR: run defaults delete com.apple.ScreenContinuity onenessPairedDeviceID at your own risk.
In my case, the iPhone Mirroring app would ask me to log in and unlock, but then it would give, what seems to be a relatively common, “Timed Out” error (“Timed out starting iPhone Mirroring. Please try again.”). Many online posts suggest signing out of the macOS, but given I use iCloud and many other Apple services, the warning when signing out looked daunting.
I knew that this would start working again if I could reset the iPhone Mirroring settings. When I tried to “Revoke Access to iPhone” in iPhone Mirroring that also failed. So, I knew I had to drop down to Finder or the command line. After searching for a little bit, I stumbled onto this reddit post. Running the following command mentioned in that post and restarting iPhone Mirroring asked me to setup iPhone Mirroring again and then it started working!
defaults delete com.apple.ScreenContinuity onenessPairedDeviceID
Since iPhone Mirroring wasn’t working for me anyways, I didn’t even bother backing up the settings like it was suggested in the post. Give it a try!