diff --git a/app/src/test/java/de/jeanlucmakiola/clockula/ArchitectureRulesTest.kt b/app/src/test/java/de/jeanlucmakiola/clockula/ArchitectureRulesTest.kt
index e39aa76..d9d8ffc 100644
--- a/app/src/test/java/de/jeanlucmakiola/clockula/ArchitectureRulesTest.kt
+++ b/app/src/test/java/de/jeanlucmakiola/clockula/ArchitectureRulesTest.kt
@@ -260,4 +260,52 @@ class ArchitectureRulesTest {
 
         assertThat(offenders).isEmpty()
     }
+
+    /**
+     * M8 D24: ICU is a seam, not an ambient API. Every localised zone name the
+     * app shows comes through `data/zones/`, so an OEM build with a broken ICU
+     * degrades one caption instead of crashing a tab.
+     */
+    @Test
+    fun `ICU is named only under the zone-names seam`() {
+        val offenders = kotlinSources.usingInCode("android.icu").filterNot {
+            it.contains("de/jeanlucmakiola/clockula/data/zones/")
+        }
+
+        assertThat(offenders).isEmpty()
+    }
+
+    /**
+     * M8 D24: `docs/PLAN.md` §8's "not sprinkled everywhere", made mechanical.
+     * The shape morph is the world clock's one showpiece; the ring screen and
+     * timer progress are sanctioned too, so widening this allowlist is a
+     * deliberate edit rather than a drift.
+     */
+    @Test
+    fun `MaterialShapes is drawn only on the world clock face`() {
+        val offenders = kotlinSources
+            .usingInCode("MaterialShapes", "androidx.graphics.shapes")
+            .filterNot { it.contains("de/jeanlucmakiola/clockula/ui/worldclock/") }
+
+        assertThat(offenders).isEmpty()
+    }
+
+    /**
+     * M8 D24: the zone is a parameter, from `ZoneProvider` — never an ambient
+     * read at a call site. Scoped to `domain/` and `ui/` on purpose:
+     * `alarm/ring/RingNotifications.kt` formats a snooze time with
+     * `systemDefault()` today, and rewriting it is not M8's business.
+     */
+    @Test
+    fun `the domain and the ui read no ambient time zone`() {
+        val domainAndUi = kotlinSources.filter {
+            val path = it.invariantSeparatorsPath
+            path.contains("de/jeanlucmakiola/clockula/domain/") ||
+                path.contains("de/jeanlucmakiola/clockula/ui/")
+        }
+
+        val offenders = domainAndUi.usingInCode("ZoneId.systemDefault()", "TimeZone.getDefault()")
+
+        assertThat(offenders).isEmpty()
+    }
 }
diff --git a/app/src/test/java/de/jeanlucmakiola/clockula/testing/FakeAlarmSeams.kt b/app/src/test/java/de/jeanlucmakiola/clockula/testing/FakeAlarmSeams.kt
index fdcc1db..76708b2 100644
--- a/app/src/test/java/de/jeanlucmakiola/clockula/testing/FakeAlarmSeams.kt
+++ b/app/src/test/java/de/jeanlucmakiola/clockula/testing/FakeAlarmSeams.kt
@@ -138,8 +138,13 @@ class FakeAlarmCapabilities(
 }
 
 /** The device's zone, which a test can change under a scheduled alarm. */
-class FakeZoneProvider(var zone: ZoneId = BERLIN) : ZoneProvider {
+class FakeZoneProvider(
+    var zone: ZoneId = BERLIN,
+    var availableIds: Set<String> = ZoneId.getAvailableZoneIds(),
+) : ZoneProvider {
     override fun current(): ZoneId = zone
+
+    override fun available(): Set<String> = availableIds
 }
 
 class FakeBootIdProvider(