I have a Document based app. It supports different document types.
One document type my app supports conforms to another document type that my app also supports.
In my app these two UTIs are designated to open different NSDocument subclasses / window controllers.
So say we have these two UTIs:
com.DocumentType.SuperType
com.DocumentType.SubType.
Now I just noticed on Tahoe 26.4, the system is launching my app using NSDocument/window controller that is designated for com.DocumentType.SuperType, when I double click a file with the com.DocumentType.SubType UTI.
I haven't changed the NSDocument configuration in many years but it looks like something changed recently.
Looks like Apple or maybe another app on my system decided to remap the file extension to a different UTI, I'll have to dig further to find out. Whoever is responsible doesn't own the type (I don't own it either but I'm also not trying to hijack the file extension).
in any case NSDocument/NSDocumentController doesn't appear to be responsible and is in the clear.