The Guard screen shows the shared policy; two Android facilities enforce it.
An accessibility service reads the browser's URL bar (no /etc/hosts exists,
and the VPN slot belongs to the user's always-on VPN), sends blocked pages
home and records the attempt; UsageStatsManager spots blocked apps in front
and the service presses home — 'kill' cannot mean force-stop, and the KDoc
says so.
Masks mean what they mean on every client: a bare '*' in the expansion list
makes '*.site' cover every subdomain, and masks no hosts file can express
are matched as ordinary globs against every URL, so they work here even
where the desktop cannot route them. Offline, the kept blocker settings are
re-evaluated with :core's evaluatePolicy, so losing signal does not lose the
guard. Two limits are documented rather than papered over: in-app WebViews
are invisible to the URL-bar reader, and blocking degrades to reporting
without the service.
Core keeps the policy/matcher semantics testable on a plain JVM: 190 core
and 44 app tests. The screen's copy says junk labels are ignored, a '*' is
kept, and unroutable masks are enforced on this phone only.
