Apple Watch notifications replace previous ones of same conversation if Watch app installed

[manuch1176]

Checklist

• I am reporting an issue in existing functionality that does not work as intended
• I've searched for existing GitHub issues

Description

If the Apple Watch app is installed, when receiving several notifications for the same conversation, the latest notification always replaces all previous ones on the Apple Watch. The consequence is that it's not possible to tap on a notification to open a stack and scroll back to see the older notifications of that same conversation.

Expected Behavior

The expected behavior is that if I get several notifications for one conversation on the Apple Watch while the Apple Watch app is installed, it should be possible to tap on the latest notification to open a stack and scroll through all the previous notifications as well.

Actual Behavior

The actual behavior is that if I get several notifications for one conversation on the Apple Watch while the Apple Watch app is installed, I can only see the latest notification of a conversation. If I tap on it, it will open that notification (not a stack of notifications). If I tap on it again, the Apple Watch app opens.

Steps to Reproduce

1. Install Apple Watch app
2. send yourself 2 or more messages from another account
3. let the notifications go to the Apple Watch
4. after all notifications arrived, swipe down to show the Watch notification center, and tap on the latest notification: observe how the previous ones are not visible and no stack opens

Environment

Device: iPhone 17 Pro Max

iOS version: 26.5.1

App version: 12.8

[manuch1176]

I assume you are using apns-collapse-id in the APNs payload to distinguish notifications of different conversations on the watch. If instead you use thread-id I think they would be stacked instead (the same way as it works if the Apple Watch app is not installed).