While the activityBackgroundTint modifier is intended to set the background color of a Live Activity, it often fails to dynamically update, leaving the activity with an incorrect background. Replacing it with
ZStack { Color(.background) .... }
solves the problem, but this is a workaround. The activityBackgroundTint modifier is still needed, at a minimum, so that the "Allow Live Activity for the app" extension does not have the default color.
If activityBackgroundTint is not behaving as expected, this is something our engineers should take a look at.
We'd greatly appreciate it if you could open a bug report, sample code or models that reproduce the issue, and post the FB number here once you do.
Bug Reporting: How and Why? has tips on creating a successful bug report.
Important: For feedback related to a specific framework or API, select "Developer Technologies & SDKs" as your Topic, then select the specific technology and relevant OS. For feedback related to Xcode, App Store Connect, or other developer tools and resources, select "Developer Tools & Resources" as your Topic, then select the specific tool or resource.
I have submitted a bug report of unexpected behaviour of Live Activities in iOS 26. The Feedback number is: FB20187170 I hope engineers could investigate the problem.