"There’s a new “feature” in Sonoma, and no one besides Apple is quite sure what it is."

No worries, I am pretty sure what it is. It is an error code to notify the user (or more likely a developer testing their software with the beta for the updated OS, as that is who/what the beta is intended for) that there is still a deprecated API used. Apple used the following slogan in the updated notes: "Update your apps to use new features, and test your apps against API changes."

This was introduced in MacOS 14 beta 3: "Starting macOS 14 Sonoma, whenever the OS detects the usage of ATS or ATSUI APIs, the user will be presented a dialog stating that the application needs to be updated. Once the dialog is dismissed by the user, the application will exit. (100521621)" - https://developer.apple.com/documentation/macos-release-note...