I Alt+Tabbed when playing in campaign on requiem with a buddy online and upon tabbing out game was still running in task manager however the game was not appearing in Windows task bar or other virtual desktops. Friend could not recreate issue under similar circumstances.
Worth noting this entire time game’s audio is functional but i have no way to actually pay the game as well my inputs on mouse and keyboard are seemingly unresponsive.
(Friend is narf001 if more information is required.)
PS if this isn’t the right place to report bugs please let me know.
I have images of proof but don’t see a way to add images so I have linked below a reddit post with said images.

If you are encountering issues during the flight, please refer to the known issues list on https://aka.ms/HaloSupportInsider and submit tickets for issues not present.