diff --git a/app/src/main/java/de/jeanlucmakiola/clockula/ui/worldclock/WorldClockSource.kt b/app/src/main/java/de/jeanlucmakiola/clockula/ui/worldclock/WorldClockSource.kt
index 4511f61..f250453 100644
--- a/app/src/main/java/de/jeanlucmakiola/clockula/ui/worldclock/WorldClockSource.kt
+++ b/app/src/main/java/de/jeanlucmakiola/clockula/ui/worldclock/WorldClockSource.kt
@@ -15,7 +15,6 @@ import kotlinx.coroutines.ExperimentalCoroutinesApi
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.distinctUntilChanged
-import kotlinx.coroutines.flow.emptyFlow
 import kotlinx.coroutines.flow.flatMapLatest
 import kotlinx.coroutines.flow.flow
 import kotlinx.coroutines.flow.map
@@ -64,7 +63,7 @@ internal class WorldClockSource @Inject constructor(
      * state and `distinctUntilChanged` only drops the odd early wake (D18).
      */
     @OptIn(ExperimentalCoroutinesApi::class)
-    fun state(refreshes: Flow<Unit> = emptyFlow()): Flow<WorldClockUiState.Loaded> =
+    fun state(refreshes: Flow<Unit>): Flow<WorldClockUiState.Loaded> =
         combine(
             worldClocks.worldClocks(),
             storedHomeZoneId,
diff --git a/app/src/test/java/de/jeanlucmakiola/clockula/data/prefs/ClockPrefsTest.kt b/app/src/test/java/de/jeanlucmakiola/clockula/data/prefs/ClockPrefsTest.kt
index 43225db..c11a2c6 100644
--- a/app/src/test/java/de/jeanlucmakiola/clockula/data/prefs/ClockPrefsTest.kt
+++ b/app/src/test/java/de/jeanlucmakiola/clockula/data/prefs/ClockPrefsTest.kt
@@ -90,6 +90,9 @@ class ClockPrefsTest {
             assertThat(awaitItem()).isEqualTo(ClockDefaults())
 
             prefs.setWorldClockSeconds(true)
+            // Wait until the write is visible to a reader, so a re-emission of
+            // the defaults would have had its chance to arrive.
+            prefs.worldClockSeconds.first { it }
 
             expectNoEvents()
             cancel()
diff --git a/app/src/test/java/de/jeanlucmakiola/clockula/ui/settings/SettingsViewModelTest.kt b/app/src/test/java/de/jeanlucmakiola/clockula/ui/settings/SettingsViewModelTest.kt
index 2dd8c52..4391896 100644
--- a/app/src/test/java/de/jeanlucmakiola/clockula/ui/settings/SettingsViewModelTest.kt
+++ b/app/src/test/java/de/jeanlucmakiola/clockula/ui/settings/SettingsViewModelTest.kt
@@ -119,7 +119,6 @@ class SettingsViewModelTest {
         viewModel.onSnoozeLimitChanged(2)
         viewModel.onVolumeRampChanged(30)
         viewModel.onDismissChallengeChanged(DismissChallenge.MATH)
-        viewModel.onWorldClockSecondsChanged(true)
         advanceUntilIdle()
 
         val defaults = (viewModel.state.value as SettingsUiState.Loaded).defaults
@@ -128,9 +127,23 @@ class SettingsViewModelTest {
         assertThat(defaults.snoozeLimit).isEqualTo(2)
         assertThat(defaults.volumeRampSeconds).isEqualTo(30)
         assertThat(defaults.dismissChallenge).isEqualTo(DismissChallenge.MATH)
-        assertThat((viewModel.state.value as SettingsUiState.Loaded).worldClockSeconds).isTrue()
     }
 
+    @Test
+    fun `the world clock's seconds switch writes through, apart from the defaults`(@TempDir tempDir: Path) =
+        runTest(main.dispatcher) {
+            val viewModel = collecting(newViewModel(tempDir))
+            advanceUntilIdle()
+            val defaultsBefore = (viewModel.state.value as SettingsUiState.Loaded).defaults
+
+            viewModel.onWorldClockSecondsChanged(true)
+            advanceUntilIdle()
+
+            val loaded = viewModel.state.value as SettingsUiState.Loaded
+            assertThat(loaded.worldClockSeconds).isTrue()
+            assertThat(loaded.defaults).isEqualTo(defaultsBefore)
+        }
+
     @Test
     fun `choosing a default alarm ringtone writes through and closes the picker`(@TempDir tempDir: Path) =
         runTest(main.dispatcher) {
diff --git a/docs/ARCHITECTURE.md b/docs/ARCHITECTURE.md
index 86f1f56..09a9585 100644
--- a/docs/ARCHITECTURE.md
+++ b/docs/ARCHITECTURE.md
@@ -592,7 +592,7 @@ one anywhere under `domain/` or `ui/`.
 ## 6. Preferences
 
 One DataStore file, `clockula_prefs`, behind floret-kit's typed `PrefStore`.
-Four slices:
+Six slices:
 
 | Slice | Keys | Owner |
 |---|---|---|
@@ -1429,9 +1429,11 @@ nothing but `delay`, which makes it testable under `runTest`'s virtual clock.
 `alignedTicks(unit)` is the same seam for a readout of whole wall-clock units:
 after the immediate emission it waits `WallBoundaries.untilNext(now, unit)`,
 re-measured against `WallClock` after every wake, so it fires on the second or
-minute boundary itself and a long `delay` or a set clock does not accumulate.
-The world clock is its one caller (§16, "The cadence"), and it merges in
-`ClockChanges`, the system's own word that the clock or zone moved, so a long
+minute boundary itself and a `delay` that ran long does not accumulate. A
+clock set mid-wait is only caught up once that wait ends, so a caller on a
+long cadence restarts the flow on `ClockChanges`, the system's own word that
+the clock or zone moved. The world clock is its one caller (§16, "The
+cadence"), and does exactly that, so a long
 cadence never means a long wait for those.
 
 ### The dismiss challenge, and why it cannot strand anyone