AlarmKit alarm shows as Live Activity but never opens full-screen. What triggers the full-screen alarm UI?

I’m debugging an iOS AlarmKit / Live Activity issue and can’t tell if this is an API limitation, entitlement issue, or something wrong in my implementation.

What works:

- alarm schedules successfully

- Live Activity / lock screen state appears

- alarm-related state updates correctly

What does not work:

- when the alarm fires, I do not get the full-screen alarm-style UI I expected

- it stays closer to a Live Activity / lock screen surface instead of taking over the screen

Things I’m trying to understand:

- Does AlarmKit actually allow third-party apps to trigger a full-screen alarm UI?

- Are there specific entitlements, Focus/notification settings, critical alert settings, or device states required?

- Is full-screen behavior only available in certain iOS versions or only for Apple’s system alarm behavior?

- Has anyone shipped this successfully?

If useful, I can share a small code snippet, but I’m mostly trying to understand the platform rules/limitations first.