iPhone Duo + CarPlay: How can we prevent a second app window when UIApplicationSupportsMultipleScenes is required?

Hello,

Summary: Navigation apps that support the CarPlay Dashboard and Instrument Cluster set UIApplicationSupportsMultipleScenes = true, which allows users to open a second app window on iPhone Duo. However, the app cannot close that window, because requestSceneSessionDestruction returns "This functionality is not supported for this device idiom." We would greatly appreciate your advice on the recommended approach.

Our navigation app supports CarPlay, including the Dashboard and Instrument Cluster scenes. Following the example in the CarPlay Developer Guide, our scene manifest sets UIApplicationSupportsMultipleScenes to true.

On the inner display of iPhone Duo, this setting also allows users to open a second window of our app (for example, via "Open in Split View"). Since our app is designed around a single main window, we would like to allow only one UIWindowSceneSessionRoleApplication scene while keeping all CarPlay scenes working.

Here is what we have found so far (tested on the iPhone Duo simulator running iOS 27.1; we have not yet tested on a physical device):

• In a test app with UIApplicationSupportsMultipleScenes = false, a second window cannot be opened, as expected.
• With true, we detect the additional window scene in scene(_:willConnectTo:options:) and display a notice instead of the app UI. However, requestSceneSessionDestruction(_:options:errorHandler:) fails with the error "This functionality is not supported for this device idiom." As a result, we are unable to close the additional window programmatically.

We would be grateful if you could help us with the following questions:

1. Is UIApplicationSupportsMultipleScenes = true required for the CarPlay Dashboard and Instrument Cluster scenes, or can these scenes connect when it is set to false?
2. If it is required, is there a supported way to keep the CarPlay scenes while limiting the app to a single phone window?
3. If there is no such way, could you please advise on the recommended way to handle an unwanted second window scene on iPhone Duo, given that apps cannot destroy scene sessions there?

Thank you very much for your time and help.