On iOS 27, a Live Activity's activityBackgroundTint and activitySystemActionForegroundColor are sometimes resolved with their light-appearance variants while the Lock Screen is dark. The activity's own content correctly uses dark at the same time. This is corrected the next time the activity is updated.
If the tint's light variant is near-white, the system replaces it with its default blue. The Live Activity background and the "Allow Live Activities" prompt turn bright blue. The "Allow"/"Don't Allow" labels also use the action colour's light variant (black instead of white).
Observed on the following:
- iPhone Duo, iOS 27.1: start an activity on a dark wallpaper when the extension's first render is slow. Adding
Thread.sleep(forTimeInterval: 1)to the body reproduces it reliably. In a real app, a heavier first render (custom font registration, larger layouts) triggers it some of the time. - iPhone 18 Pro, iOS 27.0: start an activity on a light wallpaper, then switch to a dark wallpaper.
I have tried an asset catalogue colour, a dynamic UIColor, switching on colorScheme, and an identical update straight after requesting the activity, but all still show blue. Only a fixed dark tint with a fixed white action colour avoids it.
I've filed FB25019357 with a sample project attached.
Are there any known workarounds?