@Vision Pro Engineer Hi, thanks for the additional information. This is also the workaround I am currently using.
However I don't think this is ideal. My expectation as a user would be that I can start SharePlay from everywhere. Even when already in an immersive space.
The information forwarded from the SharePlay team also seems to contradict with this WWDC Session: https://developer.apple.com/videos/play/wwdc2025/318?time=489
There it says:
[…]Now people can start sharing my app directly from the share menu. That covers apps that are windowed or volumetric, but if your shared experience uses an immersive space, then there are extra considerations you’ll need to make to ensure the share menu is always accessible. For example, I want to turn my windowed experience into a full-size board game table placed on the floor of my room, with themed 3D objects around me to make the game feel more real. To do that, I need to put it in an ImmersiveSpace. But now I have a problem. How do people share my app since there’s no window bar in an immersive space? To solve this, I can offer my own button to let people start sharing without needing to use a window or volume. When someone presses that button, my app calls the activate method on my BoardGameActivity. New in visionOS 26, calling activate on an activity automatically prompts the share menu, even outside of FaceTime. This works with windows and immersive spaces. From there, you can select nearby people or create a new FaceTime session to start sharing directly from your app."
And this actually works when running my app locally. Just not in TestFlight (and potentially also not when released). So I am still hoping for a fix. Thank you!