In my experience using iPhones and Macs running the current OS, the state of the Messages inbox syncs well, but the Unread indicator on the app icon does not. This would necessitate activating ‘Sync messages’ in Messages>Settings>iMessages on a Mac or recovering a deleted message on an iPhone and deleting it again.
However, I recently discovered the bug causing the issue and the obvious method to squash it. If you delete a message without reading it, Apple considers it read and deleted on that device but does not update the Unread status on any synced device. You must force the message’s status to be Read and then delete it for the synced devices to update the status indicator. You can do this by opening the conversation and then deleting it from the index. On an iPhone, via the circled ellipsis, you can quickly select mark all messages as read, then delete them.
If I read a message on one device, I naturally want the indicator to update on my other devices.
But if I delete it on that device without reading it, who’s to say why I deleted it? Maybe I want to deal with it on iPhone, or on my desktop. In that case I do not want the messages indicator to update.
Since it is an explicit “Unread Messages” count, it is performing exactly as designed.
But when I delete a message on one device, it is deleted everywhere. So, if I wanted to read it on another device, I would first need to recover it and then read it. It makes no sense to delete it everywhere but not change the message indicator everywhere.
I misunderstood, Alan. So the unread message is gone on all your devices if you deleted it on one, but the indicator on other devices is still counting as though that message was unread AND undeleted.
Subtle. And now you mention it, I think I’ve seen that too. I’m in the habit of deleting obvious spam when I’m viewing Messages on my Mac, by right-clicking on the summary rather than opening the thread. That may explain why a red count circle still shows up on iPhone and iPad Messages.
Just a slight correction on your take on my take: on the other device, the message is deleted, but the read indicator on the app icon does not change. When you open the app, the message does not show up. To clear the indicator, you must force a full sync. On Macs, there is a ‘Sync Now’ button in the iMessage setting in the Messages app, but on mobile devices, you must recover a deleted message and then delete it to force a sync.
I have noticed this with messages on my phone and iPad. I think that if I wait a little bit (to let the system sync?) after I read a message before I delete it, the indicator does not occur in the other device.