diff --git a/app/src/main/java/de/jeanlucmakiola/clockula/alarm/AlarmEngine.kt b/app/src/main/java/de/jeanlucmakiola/clockula/alarm/AlarmEngine.kt
index 9acaedc..fc09bc8 100644
--- a/app/src/main/java/de/jeanlucmakiola/clockula/alarm/AlarmEngine.kt
+++ b/app/src/main/java/de/jeanlucmakiola/clockula/alarm/AlarmEngine.kt
@@ -29,6 +29,7 @@ import kotlinx.coroutines.flow.flowOf
 import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.sync.Mutex
 import kotlinx.coroutines.sync.withLock
+import kotlin.time.Duration
 import kotlin.time.Duration.Companion.minutes
 import kotlin.time.Instant
 import javax.inject.Inject
@@ -80,13 +81,42 @@ class AlarmEngine @Inject constructor(
 
     suspend fun onAutoSilence(alarmId: Long): Unit = lock.withLock {
         val state = states.state(alarmId)
-        if (state.ringingSince == null) return@withLock
+        val since = state.ringingSince ?: return@withLock
+
+        // A backstop armed for a shorter window than the one now chosen ("Silence
+        // after" was raised mid-ring, and the re-arm below has not run yet): the
+        // ring still has time, so the backstop moves rather than firing early. A
+        // negative age is a clock moved backwards, and closes as it always did.
+        val age = wallClock.now() - since
+        val silenceAfter = settings.currentDefaults().alarmSilenceAfter
+        if (age >= Duration.ZERO && age < silenceAfter) {
+            scheduler.scheduleAutoSilence(since + silenceAfter, alarmId)
+            return@withLock
+        }
 
         // Missed, not snoozed: the ring stops, the cycle closes, the next
         // occurrence is scheduled. There is no missed-alarm notification in v1.
         closeCycleLocked(alarmId, state)
     }
 
+    /**
+     * "Silence after" changed. A ring in progress is measured against the new
+     * window at once: one already past it closes as missed, exactly as the
+     * backstop would close it, and one still inside it has its backstop moved
+     * to the new end. Measured from when the ring started, so changing the
+     * setting back and forth cannot buy a ring a fresh window.
+     */
+    suspend fun onSilenceAfterChanged(): Unit = lock.withLock {
+        val state = states.ringing() ?: return@withLock
+        val since = state.ringingSince ?: return@withLock
+        val silenceAfter = settings.currentDefaults().alarmSilenceAfter
+        if (wallClock.now() - since >= silenceAfter) {
+            closeCycleLocked(state.alarmId, state)
+        } else {
+            scheduler.scheduleAutoSilence(since + silenceAfter, state.alarmId)
+        }
+    }
+
     /** [minutesOverride] is a one-off, already clamped; it is never persisted anywhere (M9 D15). */
     suspend fun snooze(alarmId: Long, minutesOverride: Int? = null): SnoozeOutcome =
         lock.withLock { snoozeLocked(alarmId, minutesOverride) }
@@ -247,7 +277,7 @@ class AlarmEngine @Inject constructor(
         // A snooze is kept for as long as the resolver keeps it pending, so one
         // delivered late (after a reboot, or by Doze) still rings. Rejecting it
         // here would only re-register the same past instant and fire again.
-        val lateBy = if (isSnoozeFire) silenceAfter else AlarmRing.FIRE_GRACE
+        val lateBy = if (isSnoozeFire) AlarmRing.snoozeGrace(silenceAfter) else AlarmRing.FIRE_GRACE
         // Deleted, switched off, or a PendingIntent so stale the moment has gone:
         // re-resolve the slot and stay quiet.
         if (alarm == null || !alarm.enabled || now - scheduledFor > lateBy) {
diff --git a/app/src/main/java/de/jeanlucmakiola/clockula/alarm/ring/AlarmRingService.kt b/app/src/main/java/de/jeanlucmakiola/clockula/alarm/ring/AlarmRingService.kt
index 11d71a2..1b18bd8 100644
--- a/app/src/main/java/de/jeanlucmakiola/clockula/alarm/ring/AlarmRingService.kt
+++ b/app/src/main/java/de/jeanlucmakiola/clockula/alarm/ring/AlarmRingService.kt
@@ -26,7 +26,6 @@ import kotlinx.coroutines.Job
 import kotlinx.coroutines.SupervisorJob
 import kotlinx.coroutines.cancel
 import kotlinx.coroutines.launch
-import kotlin.time.Duration.Companion.minutes
 import javax.inject.Inject
 
 /**
@@ -200,11 +199,8 @@ class AlarmRingService : Service() {
         private const val ACTION_REPOST = AlarmIntents.ACTION_DISMISS + ".SERVICE_REPOST"
         private const val WAKE_LOCK_TAG = "clockula:alarm-ring"
 
-        /**
-         * A backstop on the backstop: past the longest ring window any "Silence
-         * after" choice allows, so a ring is never cut short by its own wake lock.
-         */
-        private val WAKE_LOCK_TIMEOUT_MILLIS = (SilenceAfter.HARD_STOP + 5.minutes).inWholeMilliseconds
+        /** A backstop on the backstop, shared with the other ring service. */
+        private val WAKE_LOCK_TIMEOUT_MILLIS = SilenceAfter.WAKE_LOCK_TIMEOUT.inWholeMilliseconds
 
         fun start(context: Context) {
             context.startForegroundService(Intent(context, AlarmRingService::class.java))
diff --git a/app/src/main/java/de/jeanlucmakiola/clockula/data/prefs/ClockPrefs.kt b/app/src/main/java/de/jeanlucmakiola/clockula/data/prefs/ClockPrefs.kt
index a14e002..080a367 100644
--- a/app/src/main/java/de/jeanlucmakiola/clockula/data/prefs/ClockPrefs.kt
+++ b/app/src/main/java/de/jeanlucmakiola/clockula/data/prefs/ClockPrefs.kt
@@ -34,16 +34,17 @@ object ClockPrefs {
 
     /**
      * How long a ringing alarm, and a finished timer, keep going before they
-     * stop on their own (#17): minutes, or [SilenceAfter.NEVER]. An absent key
-     * reads as v1's fixed ten minutes, so an upgrade changes nothing.
+     * stop on their own (#17): minutes, or [SilenceAfter.NEVER], sanitised both
+     * ways through [SilenceAfter.sanitise]. An absent key reads as v1's fixed
+     * ten minutes, so an upgrade changes nothing.
      */
     val alarmSilenceAfterMinutes: Pref<Int> =
         intPref("default_alarm_silence_after_minutes", SilenceAfter.DEFAULT_MINUTES)
-            .clampedTo(ClockLimits.SILENCE_AFTER_MINUTES)
+            .map(decode = SilenceAfter::sanitise, encode = SilenceAfter::sanitise)
 
     val timerSilenceAfterMinutes: Pref<Int> =
         intPref("default_timer_silence_after_minutes", SilenceAfter.DEFAULT_MINUTES)
-            .clampedTo(ClockLimits.SILENCE_AFTER_MINUTES)
+            .map(decode = SilenceAfter::sanitise, encode = SilenceAfter::sanitise)
 
     /** Normalised through [Zones] both ways, so a zone the device dropped reads as absent. */
     val homeZoneId: Pref<String?> = nullableStringPref("home_zone_id")
diff --git a/app/src/main/java/de/jeanlucmakiola/clockula/domain/ClockDefaults.kt b/app/src/main/java/de/jeanlucmakiola/clockula/domain/ClockDefaults.kt
index 20b2dd2..8f37066 100644
--- a/app/src/main/java/de/jeanlucmakiola/clockula/domain/ClockDefaults.kt
+++ b/app/src/main/java/de/jeanlucmakiola/clockula/domain/ClockDefaults.kt
@@ -39,5 +39,4 @@ object ClockLimits {
     val SNOOZE_MINUTES: IntRange = 1..60
     val SNOOZE_LIMIT: IntRange = 0..10
     val VOLUME_RAMP_SECONDS: IntRange = 0..60
-    val SILENCE_AFTER_MINUTES: IntRange = SilenceAfter.MINUTES
 }
diff --git a/app/src/main/java/de/jeanlucmakiola/clockula/domain/alarm/AlarmResolver.kt b/app/src/main/java/de/jeanlucmakiola/clockula/domain/alarm/AlarmResolver.kt
index 7109ba4..c188d16 100644
--- a/app/src/main/java/de/jeanlucmakiola/clockula/domain/alarm/AlarmResolver.kt
+++ b/app/src/main/java/de/jeanlucmakiola/clockula/domain/alarm/AlarmResolver.kt
@@ -72,8 +72,11 @@ object AlarmResolver {
 
         // 3. Snooze. A snooze promised before a reboot is kept, even if it came
         // due while the device was off; one older than the ring window is gone.
+        // Never sooner than SNOOZE_GRACE, so a short "Silence after" cannot make
+        // a snooze easier to lose than it was in v1.
         val snoozedUntil = working.snoozedUntil
-        val snoozePending = snoozedUntil != null && now - snoozedUntil < autoSilenceAfter
+        val snoozeGrace = AlarmRing.snoozeGrace(autoSilenceAfter)
+        val snoozePending = snoozedUntil != null && now - snoozedUntil < snoozeGrace
         if (snoozedUntil != null && !snoozePending) {
             working = working.copy(snoozedUntil = null, snoozeCount = 0)
         }
@@ -93,6 +96,21 @@ object AlarmResolver {
             }
         }
 
+        // A cycle that has just closed as missed (a ring past its window, or a
+        // snooze that never fired) closes a one-shot alarm for good, exactly as
+        // the engine's own close does. Falling through would hand it the same
+        // time tomorrow.
+        val closedAsMissed = ringingSince != null || snoozedUntil != null
+        if (closedAsMissed && !alarm.repeatDays.isRepeating) {
+            return AlarmResolution(
+                alarmId = alarm.id,
+                nextFire = null,
+                source = FireSource.NONE,
+                state = working.copy(skippedOccurrence = null),
+                disableAlarm = true,
+            )
+        }
+
         // 4. The natural occurrence, with the skip watermark on top.
         if (!alarm.skipNextOccurrence) {
             return AlarmResolution(
diff --git a/app/src/main/java/de/jeanlucmakiola/clockula/domain/alarm/AlarmRing.kt b/app/src/main/java/de/jeanlucmakiola/clockula/domain/alarm/AlarmRing.kt
index 061b57c..6d11d99 100644
--- a/app/src/main/java/de/jeanlucmakiola/clockula/domain/alarm/AlarmRing.kt
+++ b/app/src/main/java/de/jeanlucmakiola/clockula/domain/alarm/AlarmRing.kt
@@ -16,4 +16,15 @@ object AlarmRing {
      * boot or a `TIME_SET` nudge still rings; one missed by hours does not.
      */
     val FIRE_GRACE: Duration = 2.minutes
+
+    /**
+     * The least time a late snooze is still kept: v1's fixed ring window. A
+     * snooze delayed by a reboot or by Doze is kept for the "Silence after"
+     * window or this, whichever is longer, so a short window never makes a
+     * promised snooze easier to lose.
+     */
+    val SNOOZE_GRACE: Duration = 10.minutes
+
+    /** How late a snooze may come due and still ring, given the ring window. */
+    fun snoozeGrace(silenceAfter: Duration): Duration = maxOf(silenceAfter, SNOOZE_GRACE)
 }
diff --git a/app/src/main/java/de/jeanlucmakiola/clockula/domain/ring/SilenceAfter.kt b/app/src/main/java/de/jeanlucmakiola/clockula/domain/ring/SilenceAfter.kt
index 5312037..2982b15 100644
--- a/app/src/main/java/de/jeanlucmakiola/clockula/domain/ring/SilenceAfter.kt
+++ b/app/src/main/java/de/jeanlucmakiola/clockula/domain/ring/SilenceAfter.kt
@@ -18,27 +18,45 @@ object SilenceAfter {
     /** The stored value for "Never". Zero, because no window can be zero minutes long. */
     const val NEVER: Int = 0
 
-    /**
-     * Everything a stored value is clamped into, on read, on write and from a
-     * backup. Any value in it means something: [NEVER], or that many minutes.
-     */
-    val MINUTES: IntRange = NEVER..60
-
-    /**
-     * The longest a ring ever lasts, and what "Never" means in practice. The
-     * settings hints say "an hour" in words; change them with it.
-     */
-    val HARD_STOP: Duration = MINUTES.last.minutes
-
     /** The default, for alarms and timers alike: AOSP DeskClock's, and v1's fixed value. */
     const val DEFAULT_MINUTES: Int = 10
 
+    /**
+     * The longest a ring ever lasts, in minutes, and what "Never" means in
+     * practice. The settings hints say "an hour" in words; change them with it.
+     */
+    const val HARD_STOP_MINUTES: Int = 60
+
+    val HARD_STOP: Duration = HARD_STOP_MINUTES.minutes
+
+    /**
+     * How long the ring services hold their wake locks: a backstop on the
+     * backstop, past the longest window there is, so a ring is never cut
+     * short by its own wake lock.
+     */
+    val WAKE_LOCK_TIMEOUT: Duration = HARD_STOP + 5.minutes
+
+    /** Every value [sanitise] lets through: [NEVER], or that many minutes up to the hard stop. */
+    val MINUTES: IntRange = NEVER..HARD_STOP_MINUTES
+
     /** The choices the pickers offer, in order: Google Clock's, so nothing here surprises. */
     val CHOICES: List<Int> = listOf(1, 5, 10, 15, 20, 25, NEVER)
 
-    /** The ring window [minutes] stands for, clamped first so the engines never see an unofferable value. */
+    /**
+     * What a stored value is read and written as, from a picker, a hand-edited
+     * file or a backup. Too long is the hard stop, which is what it would ring
+     * for anyway. Negative is nothing anyone chose, so it is the default rather
+     * than the clamp's floor, which would be "Never".
+     */
+    fun sanitise(minutes: Int): Int = when {
+        minutes < NEVER -> DEFAULT_MINUTES
+        minutes > HARD_STOP_MINUTES -> HARD_STOP_MINUTES
+        else -> minutes
+    }
+
+    /** The ring window [minutes] stands for, sanitised first so the engines never see an unofferable value. */
     fun window(minutes: Int): Duration {
-        val clamped = minutes.coerceIn(MINUTES)
-        return if (clamped == NEVER) HARD_STOP else clamped.minutes
+        val sane = sanitise(minutes)
+        return if (sane == NEVER) HARD_STOP else sane.minutes
     }
 }
diff --git a/app/src/main/java/de/jeanlucmakiola/clockula/domain/timer/TimerRingPolicy.kt b/app/src/main/java/de/jeanlucmakiola/clockula/domain/timer/TimerRingPolicy.kt
index 478747d..f9bce4f 100644
--- a/app/src/main/java/de/jeanlucmakiola/clockula/domain/timer/TimerRingPolicy.kt
+++ b/app/src/main/java/de/jeanlucmakiola/clockula/domain/timer/TimerRingPolicy.kt
@@ -1,6 +1,7 @@
 package de.jeanlucmakiola.clockula.domain.timer
 
 import de.jeanlucmakiola.clockula.domain.ClockDefaults
+import de.jeanlucmakiola.clockula.domain.ring.SilenceAfter
 import kotlin.time.Instant
 
 sealed interface TimerRingDecision {
@@ -18,6 +19,11 @@ sealed interface TimerRingDecision {
         val settings: TimerSettings,
         /** When the window closes: the session anchor + [ClockDefaults.timerSilenceAfter]. */
         val silenceAt: Instant,
+        /**
+         * The session anchor: when its audio opened. The session's identity
+         * (D10), which [silenceAt] is not, since "Silence after" can move it.
+         */
+        val openedAt: Instant,
     ) : TimerRingDecision
 }
 
@@ -53,7 +59,10 @@ object TimerRingPolicy {
         if (soundingSince != null && now - soundingSince >= window) {
             return TimerRingOutcome(
                 TimerRingDecision.AutoSilenced(subject.timer.id),
-                soundingSince = soundingSince,
+                // Stays run out whatever "Silence after" becomes: the anchor is
+                // moved back past the longest window there is, so raising the
+                // setting later cannot start a silenced timer ringing again.
+                soundingSince = minOf(soundingSince, now - SilenceAfter.HARD_STOP),
             )
         }
 
@@ -75,6 +84,7 @@ object TimerRingPolicy {
                 subjectId = subject.timer.id,
                 settings = subject.timer.resolveSettings(defaults),
                 silenceAt = anchor + window,
+                openedAt = anchor,
             ),
             soundingSince = anchor,
         )
diff --git a/app/src/main/java/de/jeanlucmakiola/clockula/timer/service/TimerService.kt b/app/src/main/java/de/jeanlucmakiola/clockula/timer/service/TimerService.kt
index 0775b6a..6c666d1 100644
--- a/app/src/main/java/de/jeanlucmakiola/clockula/timer/service/TimerService.kt
+++ b/app/src/main/java/de/jeanlucmakiola/clockula/timer/service/TimerService.kt
@@ -35,7 +35,6 @@ import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.merge
 import kotlinx.coroutines.launch
-import kotlin.time.Duration.Companion.minutes
 import kotlin.time.Instant
 import javax.inject.Inject
 
@@ -97,11 +96,11 @@ class TimerService : Service() {
     private var alreadyAlerted: Boolean = false
 
     /**
-     * The auto-silence window the heads-up above was spent inside. A window is
-     * one ring session (D10), so a *new* session is a new event and gets its
-     * own one heads-up — even while an earlier timer stays EXPIRED.
+     * The anchor of the ring session the heads-up above was spent inside. A
+     * *new* session is a new event and gets its own one heads-up (D10) — even
+     * while an earlier timer stays EXPIRED.
      */
-    private var alertedWindow: Instant? = null
+    private var alertedSession: Instant? = null
 
     /**
      * `startForeground` is for going foreground, not for posting: every engine
@@ -206,8 +205,10 @@ class TimerService : Service() {
     }
 
     /**
-     * A ring session's window is its identity (D10), so when the window moves the
-     * flag that spends the session's one heads-up moves with it. The state is
+     * A ring session's anchor is its identity (D10), so when a new session opens
+     * the flag that spends the session's one heads-up moves with it. The anchor
+     * rather than the window's end, which a "Silence after" edit can move
+     * mid-session without making it a new one. The state is
      * asked for again, because it was computed from the answer that has just
      * changed — a second pass rather than a notification that says the right
      * thing one trigger too late.
@@ -216,9 +217,9 @@ class TimerService : Service() {
         // Only a sounding decision carries a window; a suppressed or silenced one
         // must not clear the record, or an alarm ringing across a session would
         // buy it a second heads-up (D9).
-        val window = (state.ring as? TimerRingDecision.Sound)?.silenceAt ?: return state
-        val reopened = alreadyAlerted && window != alertedWindow
-        alertedWindow = window
+        val session = (state.ring as? TimerRingDecision.Sound)?.openedAt ?: return state
+        val reopened = alreadyAlerted && session != alertedSession
+        alertedSession = session
         if (!reopened) return state
         alreadyAlerted = false
         return engine.serviceState(alreadyAlerted)
@@ -365,11 +366,8 @@ class TimerService : Service() {
     companion object {
         private const val WAKE_LOCK_TAG = "clockula:timer-ring"
 
-        /**
-         * A backstop on the backstop: past the longest ring window any "Silence
-         * after" choice allows, so a ring is never cut short by its own wake lock.
-         */
-        private val WAKE_LOCK_TIMEOUT_MILLIS = (SilenceAfter.HARD_STOP + 5.minutes).inWholeMilliseconds
+        /** A backstop on the backstop, shared with the other ring service. */
+        private val WAKE_LOCK_TIMEOUT_MILLIS = SilenceAfter.WAKE_LOCK_TIMEOUT.inWholeMilliseconds
 
         fun start(context: Context) {
             context.startForegroundService(Intent(context, TimerService::class.java))
diff --git a/app/src/main/java/de/jeanlucmakiola/clockula/ui/alarms/AlarmsViewModel.kt b/app/src/main/java/de/jeanlucmakiola/clockula/ui/alarms/AlarmsViewModel.kt
index d17e9fe..b0f608c 100644
--- a/app/src/main/java/de/jeanlucmakiola/clockula/ui/alarms/AlarmsViewModel.kt
+++ b/app/src/main/java/de/jeanlucmakiola/clockula/ui/alarms/AlarmsViewModel.kt
@@ -86,11 +86,12 @@ class AlarmsViewModel @Inject internal constructor(
     }
 
     /**
-     * The ring service is a single global slot the resolver cannot reach, and
-     * its auto-silence backstop disarms itself once `ringingSince` is null — so
-     * switching off a *ringing* alarm has to go through the engine first, or it
-     * sounds until the wake lock expires. Conditional, because dismissing a
-     * merely snoozed alarm would drop a snooze it should keep (M5 D11).
+     * Switching off a *ringing* alarm goes through the engine first, so the ring
+     * closes as a dismissal: the snooze notification cleared and the cycle
+     * closed under the engine's lock. (Since #17 the engine would also stop the
+     * sound when the next resolution sees the alarm disabled, but that is a
+     * backstop, not the path.) Conditional, because dismissing a merely
+     * snoozed alarm would drop a snooze it should keep (M5 D11).
      */
     private suspend fun stopRingIfRinging(alarmId: Long) {
         if (engine.ringSession()?.alarm?.id == alarmId) engine.dismiss(alarmId)
diff --git a/app/src/main/java/de/jeanlucmakiola/clockula/ui/alarms/OverridePickers.kt b/app/src/main/java/de/jeanlucmakiola/clockula/ui/alarms/OverridePickers.kt
index d93d58c..6046147 100644
--- a/app/src/main/java/de/jeanlucmakiola/clockula/ui/alarms/OverridePickers.kt
+++ b/app/src/main/java/de/jeanlucmakiola/clockula/ui/alarms/OverridePickers.kt
@@ -78,24 +78,26 @@ internal fun silenceAfterText(minutes: Int): String = if (minutes == SilenceAfte
 
 /**
  * "Silence after" is app-wide only (#17): no alarm or timer overrides it, so
- * this picker never offers "App default". It shares the overrides' shape so
- * the settings screens' pickers all look and behave alike.
+ * this picker has no "App default" rung. A stored value no choice matches (a
+ * backup can carry any minute up to the hard stop) is offered too, in its
+ * place, so the picker always shows what is selected and can put it back.
  */
 @Composable
 internal fun SilenceAfterPicker(
     selected: Int,
     onSelect: (Int) -> Unit,
     onDismiss: () -> Unit,
-) = OverridePicker(
-    title = stringResource(R.string.settings_silence_after),
-    options = SilenceAfter.CHOICES,
-    stored = selected,
-    default = selected,
-    text = { silenceAfterText(it) },
-    onSelect = { it?.let(onSelect) },
-    onDismiss = onDismiss,
-    includeAppDefault = false,
-)
+) {
+    val finite = (SilenceAfter.CHOICES + selected).filter { it != SilenceAfter.NEVER }.distinct().sorted()
+    OptionPicker(
+        title = stringResource(R.string.settings_silence_after),
+        options = finite + SilenceAfter.NEVER,
+        selected = selected,
+        label = { silenceAfterText(it) },
+        onSelect = onSelect,
+        onDismiss = onDismiss,
+    )
+}
 
 @Composable
 internal fun VibratePicker(
diff --git a/app/src/main/java/de/jeanlucmakiola/clockula/ui/settings/SettingsViewModel.kt b/app/src/main/java/de/jeanlucmakiola/clockula/ui/settings/SettingsViewModel.kt
index 224d8b2..213ac9c 100644
--- a/app/src/main/java/de/jeanlucmakiola/clockula/ui/settings/SettingsViewModel.kt
+++ b/app/src/main/java/de/jeanlucmakiola/clockula/ui/settings/SettingsViewModel.kt
@@ -3,6 +3,7 @@ package de.jeanlucmakiola.clockula.ui.settings
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import dagger.hilt.android.lifecycle.HiltViewModel
+import de.jeanlucmakiola.clockula.alarm.AlarmEngine
 import de.jeanlucmakiola.clockula.alarm.DeviceStateReader
 import de.jeanlucmakiola.clockula.data.appicon.LauncherIcon
 import de.jeanlucmakiola.clockula.data.appicon.LauncherIconManager
@@ -48,6 +49,7 @@ import javax.inject.Inject
 @HiltViewModel
 class SettingsViewModel @Inject internal constructor(
     private val settings: SettingsPrefs,
+    private val alarmEngine: AlarmEngine,
     private val ringtones: RingtoneCatalog,
     private val preview: RingtonePreviewer,
     private val worldClocks: WorldClockSource,
@@ -142,8 +144,11 @@ class SettingsViewModel @Inject internal constructor(
     fun onDismissChallengeChanged(value: DismissChallenge) =
         viewModelScope.launch { settings.setDismissChallenge(value) }
 
-    fun onAlarmSilenceAfterChanged(minutes: Int) =
-        viewModelScope.launch { settings.setAlarmSilenceAfterMinutes(minutes) }
+    /** The engine re-measures a ring in progress against the new window at once. */
+    fun onAlarmSilenceAfterChanged(minutes: Int) = viewModelScope.launch {
+        settings.setAlarmSilenceAfterMinutes(minutes)
+        alarmEngine.onSilenceAfterChanged()
+    }
 
     fun onTimerSilenceAfterChanged(minutes: Int) =
         viewModelScope.launch { settings.setTimerSilenceAfterMinutes(minutes) }
diff --git a/app/src/test/java/de/jeanlucmakiola/clockula/alarm/AlarmEngineTest.kt b/app/src/test/java/de/jeanlucmakiola/clockula/alarm/AlarmEngineTest.kt
index bb87cb9..50f13cd 100644
--- a/app/src/test/java/de/jeanlucmakiola/clockula/alarm/AlarmEngineTest.kt
+++ b/app/src/test/java/de/jeanlucmakiola/clockula/alarm/AlarmEngineTest.kt
@@ -911,6 +911,85 @@ class AlarmEngineTest {
         assertThat(entry.source).isEqualTo(FireSource.RESUMED_RING)
     }
 
+    @Test
+    fun `a backstop armed for a shorter window moves rather than firing early`(@TempDir dir: Path) = runTest {
+        givenAlarm(repeatDays = RepeatDays.EVERY_DAY)
+        wallClock.instant = sevenToday
+        val settings = settings(dir)
+        val engine = engineOver(settings)
+        engine.onFire(alarmId = 1L, scheduledFor = sevenToday)
+        settings.setAlarmSilenceAfterMinutes(25)
+        wallClock.instant = sevenToday + 10.minutes
+
+        engine.onAutoSilence(1L)
+
+        assertThat(ring.ringing.value).isEqualTo(1L)
+        assertThat(states.state(1L).ringingSince).isEqualTo(sevenToday)
+        assertThat(scheduler.autoSilence).isEqualTo(Registration(sevenToday + 25.minutes, 1L))
+    }
+
+    @Test
+    fun `raising silence-after mid-ring moves the backstop at once`(@TempDir dir: Path) = runTest {
+        givenAlarm(repeatDays = RepeatDays.EVERY_DAY)
+        wallClock.instant = sevenToday
+        val settings = settings(dir)
+        val engine = engineOver(settings)
+        engine.onFire(alarmId = 1L, scheduledFor = sevenToday)
+        wallClock.instant = sevenToday + 3.minutes
+
+        settings.setAlarmSilenceAfterMinutes(SilenceAfter.NEVER)
+        engine.onSilenceAfterChanged()
+
+        assertThat(ring.ringing.value).isEqualTo(1L)
+        assertThat(scheduler.autoSilence).isEqualTo(Registration(sevenToday + SilenceAfter.HARD_STOP, 1L))
+    }
+
+    @Test
+    fun `lowering silence-after below a ring's age closes it as missed at once`(@TempDir dir: Path) = runTest {
+        givenAlarm()
+        wallClock.instant = sevenToday
+        val settings = settings(dir)
+        val engine = engineOver(settings)
+        engine.onFire(alarmId = 1L, scheduledFor = sevenToday)
+        wallClock.instant = sevenToday + 5.minutes
+
+        settings.setAlarmSilenceAfterMinutes(1)
+        engine.onSilenceAfterChanged()
+
+        assertThat(ring.ringing.value).isNull()
+        assertThat(states.state(1L).ringingSince).isNull()
+        assertThat(scheduler.autoSilence).isNull()
+        // A one-shot alarm's cycle has closed, so it is off, not armed for tomorrow.
+        assertThat(alarms.find(1L)?.enabled).isFalse()
+    }
+
+    @Test
+    fun `changing silence-after with nothing ringing touches nothing`(@TempDir dir: Path) = runTest {
+        givenAlarm()
+        val settings = settings(dir)
+        val engine = engineOver(settings)
+
+        settings.setAlarmSilenceAfterMinutes(1)
+        engine.onSilenceAfterChanged()
+
+        assertThat(ring.events).isEmpty()
+        assertThat(scheduler.autoSilence).isNull()
+    }
+
+    @Test
+    fun `a one-shot ring missed across a reboot is disabled, not re-armed for tomorrow`(@TempDir dir: Path) =
+        runTest {
+            givenAlarm()
+            wallClock.instant = sevenToday + 40.minutes
+            givenRingingAt(alarmId = 1L, occurrence = sevenToday, since = sevenToday)
+            val engine = engine(dir)
+
+            engine.onBootCompleted()
+
+            assertThat(alarms.find(1L)?.enabled).isFalse()
+            assertThat(scheduler.next).isNull()
+        }
+
     // --- upcoming() ---
 
     @Test
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 bdfe100..11817ca 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
@@ -162,7 +162,7 @@ class ClockPrefsTest {
         prefs.setAlarmSilenceAfterMinutes(999)
         prefs.setTimerSilenceAfterMinutes(-3)
         assertThat(prefs.defaults.first().alarmSilenceAfterMinutes).isEqualTo(60)
-        assertThat(prefs.defaults.first().timerSilenceAfterMinutes).isEqualTo(SilenceAfter.NEVER)
+        assertThat(prefs.defaults.first().timerSilenceAfterMinutes).isEqualTo(SilenceAfter.DEFAULT_MINUTES)
 
         dataStore.updateData { stored ->
             stored.toMutablePreferences()
diff --git a/app/src/test/java/de/jeanlucmakiola/clockula/domain/alarm/AlarmResolverTest.kt b/app/src/test/java/de/jeanlucmakiola/clockula/domain/alarm/AlarmResolverTest.kt
index e963c99..fb67163 100644
--- a/app/src/test/java/de/jeanlucmakiola/clockula/domain/alarm/AlarmResolverTest.kt
+++ b/app/src/test/java/de/jeanlucmakiola/clockula/domain/alarm/AlarmResolverTest.kt
@@ -409,4 +409,39 @@ class AlarmResolverTest {
         assertThat(kept.nextFire to kept.source).isEqualTo(snoozedUntil to FireSource.SNOOZE)
         assertThat(dropped.state.snoozedUntil).isNull()
     }
+
+    @Test
+    fun `a one-shot ring closed as missed disables the alarm rather than ringing tomorrow`() {
+        val alarm = alarmAt(hour = 7)
+        val state = ringState(ringingSince = morning - 2.minutes, handledOccurrence = morning - 2.minutes)
+
+        val resolution = resolve(alarm, state, silenceAfter = SilenceAfter.window(1))
+
+        assertThat(resolution.disableAlarm).isTrue()
+        assertThat(resolution.nextFire).isNull()
+        assertThat(resolution.state.ringingSince).isNull()
+    }
+
+    @Test
+    fun `a one-shot snooze that never fired disables the alarm rather than ringing tomorrow`() {
+        val alarm = alarmAt(hour = 7)
+        val state = ringState(snoozedUntil = morning - 11.minutes, snoozeCount = 1)
+
+        val resolution = resolve(alarm, state)
+
+        assertThat(resolution.disableAlarm).isTrue()
+        assertThat(resolution.nextFire).isNull()
+        assertThat(resolution.state.snoozedUntil).isNull()
+    }
+
+    @Test
+    fun `a short window never makes a late snooze easier to lose than v1's ten minutes`() {
+        val alarm = alarmAt(hour = 7, repeatDays = RepeatDays.EVERY_DAY)
+        val snoozedUntil = morning - 8.minutes
+        val state = ringState(snoozedUntil = snoozedUntil, snoozeCount = 1)
+
+        val resolution = resolve(alarm, state, silenceAfter = SilenceAfter.window(1))
+
+        assertThat(resolution.nextFire to resolution.source).isEqualTo(snoozedUntil to FireSource.SNOOZE)
+    }
 }
diff --git a/app/src/test/java/de/jeanlucmakiola/clockula/domain/ring/SilenceAfterTest.kt b/app/src/test/java/de/jeanlucmakiola/clockula/domain/ring/SilenceAfterTest.kt
index e977bbb..a484e83 100644
--- a/app/src/test/java/de/jeanlucmakiola/clockula/domain/ring/SilenceAfterTest.kt
+++ b/app/src/test/java/de/jeanlucmakiola/clockula/domain/ring/SilenceAfterTest.kt
@@ -27,13 +27,18 @@ class SilenceAfterTest {
     fun `Never is the hard stop, an hour`() {
         assertThat(SilenceAfter.window(SilenceAfter.NEVER)).isEqualTo(SilenceAfter.HARD_STOP)
         assertThat(SilenceAfter.HARD_STOP).isEqualTo(1.hours)
+        assertThat(SilenceAfter.WAKE_LOCK_TIMEOUT).isGreaterThan(SilenceAfter.HARD_STOP)
     }
 
     @Test
     fun `no value reaches the engines as a window longer than the hard stop`() {
         assertThat(SilenceAfter.window(24 * 60)).isEqualTo(SilenceAfter.HARD_STOP)
-        // Negative is clamped to Never rather than read as an instant silence.
-        assertThat(SilenceAfter.window(-5)).isEqualTo(SilenceAfter.HARD_STOP)
+    }
+
+    @Test
+    fun `a negative value is the default, not Never`() {
+        assertThat(SilenceAfter.sanitise(-1)).isEqualTo(SilenceAfter.DEFAULT_MINUTES)
+        assertThat(SilenceAfter.window(-5)).isEqualTo(10.minutes)
     }
 
     @Test
diff --git a/app/src/test/java/de/jeanlucmakiola/clockula/domain/timer/TimerRingPolicyTest.kt b/app/src/test/java/de/jeanlucmakiola/clockula/domain/timer/TimerRingPolicyTest.kt
index 70f4c8f..5019802 100644
--- a/app/src/test/java/de/jeanlucmakiola/clockula/domain/timer/TimerRingPolicyTest.kt
+++ b/app/src/test/java/de/jeanlucmakiola/clockula/domain/timer/TimerRingPolicyTest.kt
@@ -156,6 +156,7 @@ class TimerRingPolicyTest {
                     subjectId = 7L,
                     settings = released.sound().settings,
                     silenceAt = now + ClockDefaults().timerSilenceAfter,
+                    openedAt = now,
                 ),
                 soundingSince = now,
             ),
@@ -179,8 +180,10 @@ class TimerRingPolicyTest {
 
         val outcome = decide(soundingSince = opened)
 
-        assertThat(outcome)
-            .isEqualTo(TimerRingOutcome(TimerRingDecision.AutoSilenced(7L), soundingSince = opened))
+        // The anchor moves back past the longest window, so the session stays run out (#17).
+        assertThat(outcome).isEqualTo(
+            TimerRingOutcome(TimerRingDecision.AutoSilenced(7L), soundingSince = now - SilenceAfter.HARD_STOP),
+        )
     }
 
     /** §5.4 #15 */
@@ -196,12 +199,13 @@ class TimerRingPolicyTest {
     /** §5.4 #16 */
     @Test
     fun `an auto-silenced session does not restart a minute later`() {
-        val opened = now - ClockDefaults().timerSilenceAfter
+        val silenced = decide(soundingSince = now - ClockDefaults().timerSilenceAfter)
 
-        val outcome = decide(soundingSince = opened, at = now + 1.minutes)
+        val outcome = decide(soundingSince = silenced.soundingSince, at = now + 1.minutes)
 
-        assertThat(outcome)
-            .isEqualTo(TimerRingOutcome(TimerRingDecision.AutoSilenced(7L), soundingSince = opened))
+        assertThat(outcome).isEqualTo(
+            TimerRingOutcome(TimerRingDecision.AutoSilenced(7L), soundingSince = silenced.soundingSince),
+        )
     }
 
     /** §5.4 #17 */
@@ -274,4 +278,28 @@ class TimerRingPolicyTest {
         assertThat(sounding.sound().silenceAt).isEqualTo(now - 59.minutes + SilenceAfter.HARD_STOP)
         assertThat(silenced.decision).isEqualTo(TimerRingDecision.AutoSilenced(7L))
     }
+
+    @Test
+    fun `raising silence-after does not restart a session that already went quiet`() {
+        val short = defaults.copy(timerSilenceAfterMinutes = 1)
+        val silenced = decide(defaults = short, soundingSince = now - 1.minutes)
+
+        val raised = decide(
+            defaults = defaults.copy(timerSilenceAfterMinutes = SilenceAfter.NEVER),
+            soundingSince = silenced.soundingSince,
+            at = now + 4.minutes,
+        )
+
+        assertThat(raised.decision).isEqualTo(TimerRingDecision.AutoSilenced(7L))
+    }
+
+    @Test
+    fun `changing silence-after mid-session moves the window but not the session`() {
+        val opened = now - 2.minutes
+
+        val sound = decide(defaults = defaults.copy(timerSilenceAfterMinutes = 25), soundingSince = opened).sound()
+
+        assertThat(sound.openedAt).isEqualTo(opened)
+        assertThat(sound.silenceAt).isEqualTo(opened + 25.minutes)
+    }
 }
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 1af202e..f35a2b0 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
@@ -1,13 +1,30 @@
 package de.jeanlucmakiola.clockula.ui.settings
 
 import com.google.common.truth.Truth.assertThat
+import de.jeanlucmakiola.clockula.alarm.AlarmEngine
+import de.jeanlucmakiola.clockula.data.alarms.AlarmMapper
+import de.jeanlucmakiola.clockula.data.alarms.AlarmRepositoryImpl
+import de.jeanlucmakiola.clockula.data.alarms.AlarmStateRepositoryImpl
 import de.jeanlucmakiola.clockula.data.appicon.LauncherIcon
 import de.jeanlucmakiola.clockula.domain.DismissChallenge
+import de.jeanlucmakiola.clockula.domain.RepeatDays
+import de.jeanlucmakiola.clockula.domain.ring.SilenceAfter
+import de.jeanlucmakiola.clockula.testing.BERLIN
+import de.jeanlucmakiola.clockula.testing.FakeAlarmDao
+import de.jeanlucmakiola.clockula.testing.FakeAlarmNotifier
+import de.jeanlucmakiola.clockula.testing.FakeAlarmScheduler
+import de.jeanlucmakiola.clockula.testing.FakeAlarmStateDao
 import de.jeanlucmakiola.clockula.testing.FakeDeviceStateReader
 import de.jeanlucmakiola.clockula.testing.FakeLauncherIconManager
 import de.jeanlucmakiola.clockula.testing.FakeRingtoneCatalog
+import de.jeanlucmakiola.clockula.testing.FakeRingCoordinator
 import de.jeanlucmakiola.clockula.testing.FakeRingtonePreviewer
+import de.jeanlucmakiola.clockula.testing.FakeWallClock
+import de.jeanlucmakiola.clockula.testing.FakeZoneProvider
 import de.jeanlucmakiola.clockula.testing.MainDispatcherExtension
+import de.jeanlucmakiola.clockula.testing.alarmAt
+import de.jeanlucmakiola.clockula.testing.RecordingRebootRepair
+import de.jeanlucmakiola.clockula.testing.instantAt
 import de.jeanlucmakiola.clockula.testing.worldClockHarness
 import de.jeanlucmakiola.floret.prefs.ThemeMode
 import kotlinx.coroutines.Dispatchers
@@ -21,6 +38,7 @@ import org.junit.jupiter.api.Test
 import org.junit.jupiter.api.extension.RegisterExtension
 import org.junit.jupiter.api.io.TempDir
 import java.nio.file.Path
+import kotlin.time.Duration.Companion.minutes
 
 /**
  * The real [SettingsViewModel] over the real [de.jeanlucmakiola.clockula.data.prefs.SettingsPrefs]
@@ -35,13 +53,33 @@ class SettingsViewModelTest {
     @RegisterExtension
     val main = MainDispatcherExtension()
 
+    // The alarm engine "Silence after" re-measures a ring through, over fakes.
+    private val alarmDao = FakeAlarmDao()
+    private val stateDao = FakeAlarmStateDao(alarms = alarmDao)
+    private val wallClock = FakeWallClock(instantAt(BERLIN, "2026-06-10T07:00"))
+    private val alarmScheduler = FakeAlarmScheduler()
+    private val ring = FakeRingCoordinator()
+    private lateinit var alarmEngine: AlarmEngine
+
     private fun TestScope.newViewModel(
         tempDir: Path,
         launcherIcons: FakeLauncherIconManager = FakeLauncherIconManager(),
     ): SettingsViewModel {
         val harness = worldClockHarness(tempDir)
+        alarmEngine = AlarmEngine(
+            alarms = AlarmRepositoryImpl(alarmDao, wallClock),
+            states = AlarmStateRepositoryImpl(stateDao),
+            settings = harness.settings,
+            scheduler = alarmScheduler,
+            ring = ring,
+            notifier = FakeAlarmNotifier(),
+            rebootRepair = RecordingRebootRepair(),
+            wallClock = wallClock,
+            zones = FakeZoneProvider(BERLIN),
+        )
         return SettingsViewModel(
             settings = harness.settings,
+            alarmEngine = alarmEngine,
             ringtones = FakeRingtoneCatalog(),
             preview = FakeRingtonePreviewer(),
             worldClocks = harness.source,
@@ -119,6 +157,8 @@ class SettingsViewModelTest {
         viewModel.onSnoozeLimitChanged(2)
         viewModel.onVolumeRampChanged(30)
         viewModel.onDismissChallengeChanged(DismissChallenge.MATH)
+        viewModel.onAlarmSilenceAfterChanged(25)
+        viewModel.onTimerSilenceAfterChanged(SilenceAfter.NEVER)
         advanceUntilIdle()
 
         val defaults = (viewModel.state.value as SettingsUiState.Loaded).defaults
@@ -127,8 +167,24 @@ class SettingsViewModelTest {
         assertThat(defaults.snoozeLimit).isEqualTo(2)
         assertThat(defaults.volumeRampSeconds).isEqualTo(30)
         assertThat(defaults.dismissChallenge).isEqualTo(DismissChallenge.MATH)
+        assertThat(defaults.alarmSilenceAfterMinutes).isEqualTo(25)
+        assertThat(defaults.timerSilenceAfterMinutes).isEqualTo(SilenceAfter.NEVER)
     }
 
+    @Test
+    fun `changing the alarm silence-after re-measures a ring in progress`(@TempDir tempDir: Path) =
+        runTest(main.dispatcher) {
+            val viewModel = collecting(newViewModel(tempDir))
+            alarmDao.insert(AlarmMapper.toEntity(alarmAt(id = 1L, hour = 7, repeatDays = RepeatDays.EVERY_DAY)))
+            alarmEngine.onFire(alarmId = 1L, scheduledFor = wallClock.instant)
+            advanceUntilIdle()
+
+            viewModel.onAlarmSilenceAfterChanged(25)
+            advanceUntilIdle()
+
+            assertThat(alarmScheduler.autoSilence?.fireAt).isEqualTo(wallClock.instant + 25.minutes)
+        }
+
     @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 31868fc..b035745 100644
--- a/docs/ARCHITECTURE.md
+++ b/docs/ARCHITECTURE.md
@@ -1163,26 +1163,37 @@ Never), **10 minutes** by default, AOSP DeskClock's default and v1's fixed
 value, so an upgrade changes nothing. Snoozing keeps it open.
 
 The window is read from `ClockDefaults.alarmSilenceAfter` everywhere a ring is
-measured: the resolver's ringing and late-snooze checks, the backstop `onFire`
-arms, how late a snooze fire may arrive, and whether a ring interrupted by a
-reboot is resumed. `AlarmResolver.resolve` takes it without a default, so no
-caller can measure against a window the user did not choose.
+measured: the resolver's ringing check, the backstop `onFire` arms, and whether
+a ring interrupted by a reboot is resumed. `AlarmResolver.resolve` takes it
+without a default, so no caller can measure against a window the user did not
+choose. How late a snooze may come due and still ring is the window **or
+`AlarmRing.SNOOZE_GRACE` (v1's ten minutes), whichever is longer**: a short
+"Silence after" must not make a promised snooze easier to lose to a reboot.
 
 **"Never" is an hour.** The backstop is also what stops a phone left at home
 from ringing until its battery is flat, what bounds the ring services' wake
 locks, and what keeps a reboot hours later from resuming a ring nobody was
 there for. So "Never" maps to `SilenceAfter.HARD_STOP` (60 minutes), longer
 than any finite choice, and the settings hint says so in words. Stored values
-are clamped to 0..60 on read, on write and from a backup, so no value can make
-a ring outlast it.
+go through `SilenceAfter.sanitise` on read, on write and from a backup: over 60
+is 60, so no value can make a ring outlast the hard stop, and a negative one is
+the default rather than the clamp's floor, which would be "Never".
 
-A ring started under one window keeps the backstop it was armed with. When the
-window is shortened mid-ring, the next re-resolution closes the ring once it is
-past the new window, and `persist` then stops the ring service and cancels the
-backstop with it: storage says nothing rings, so nothing may. The same applies
-to any ring the resolver closes (a clock jumped forward, a ringing alarm
-switched off), which earlier only cleared `ringingSince` and left the sound to
-the backstop.
+Changing the setting mid-ring applies at once. The settings screen calls
+`AlarmEngine.onSilenceAfterChanged()`, which measures the ring in progress
+against the new window from when it *started*: past it, the cycle closes as
+missed through `closeCycleLocked`; inside it, the backstop moves to the new
+end. As a second line, `onAutoSilence` re-arms rather than closes a ring that
+is still inside the current window, so a backstop armed for a shorter one can
+never end a ring early.
+
+Whenever the resolver closes a ring (a clock jumped forward, a ringing alarm
+switched off, a reboot outlasting the window), `persist` stops the ring service
+and cancels the backstop: storage says nothing rings, so nothing may. Earlier
+that path only cleared `ringingSince` and left the sound to the backstop. And a
+cycle the resolver closes as missed (a ring past its window, or a snooze that
+never fired) **disables a one-shot alarm**, exactly as `closeCycleLocked`
+does; falling through would have armed it for the same time tomorrow.
 
 A **non-repeating alarm is disabled when its cycle closes, never when it opens**.
 Disabling it at the start would clear its own snooze and the alarm would vanish
@@ -1924,7 +1935,12 @@ The window is the timer's own **"Silence after"** setting
 default: the same choices as the alarm's and the same one-hour "Never", but a
 separate value, because coupling the two would make one number answer two
 questions. `TimerRingPolicy` reads it from the defaults it already takes, so a
-change applies on the service's next pass. Unlike an alarm's, a timer's
+change applies on the service's next pass. A session that has gone quiet stays
+quiet: on auto-silence the policy moves the stored anchor back past
+`SilenceAfter.HARD_STOP`, so raising the setting afterwards cannot start it
+ringing again. The service's one heads-up is keyed to the session's anchor
+(`Sound.openedAt`) rather than to the window's end, which an edit can move
+without making a new session. Unlike an alarm's, a timer's
 **auto-silence stops the noise and leaves the row `EXPIRED`.** An auto-silenced
 alarm is a *missed* alarm and its cycle closes; an auto-silenced timer has still
 finished, and the user coming back must be able to see that and add a minute
diff --git a/docs/BACKUP.md b/docs/BACKUP.md
index 670499b..c5d7799 100644
--- a/docs/BACKUP.md
+++ b/docs/BACKUP.md
@@ -151,7 +151,8 @@ other unknown field.
 are how long a ringing alarm or a finished timer keeps going before it stops on
 its own: whole minutes, with `0` meaning "Never" (which still stops after an
 hour). A file without them, from before the setting existed, imports as `10`,
-the value it was made with. Out-of-range values clamp to 0..60.
+the value it was made with. A value over 60 reads as 60 (which is what Never
+rings for anyway); a negative one reads as the default, 10.
 
 Every numeric/duration value is clamped on *apply* using the same ranges and encoding
 as the existing preference setters, never on parse.