diff --git a/CHANGELOG.md b/CHANGELOG.md
index c9f12e6..9caee90 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -33,6 +33,60 @@ are no binary releases; "version" tracks the shared `version` in the root build
 - **`components`** — `StepNumber` is public, with a `done` flag that swaps the
   numeral for a check, for numbered steps an app builds from its own
   `GroupedRow`s (e.g. rows that open a setting).
+- **`core-prefs`** — `Preferences[pref]` and `MutablePreferences[pref] = value`,
+  so an app can read several prefs out of one `PrefStore.data` snapshot and
+  write several in one `PrefStore.edit` without dropping to raw keys. Plus
+  `nullableBooleanPref`, for a tri-state flag where unset differs from `false`.
+- **`components`** — picker-row helpers lifted from Calendula's pickers and
+  settings, all additive. `GroupedRow` takes `checked` (default `false`): it
+  implies `selected` and fills an empty trailing slot with `SelectedCheck`,
+  replacing the hand-written `if (selected) { { SelectedCheck() } } else null`.
+  `OptionPicker` takes `dismissOnSelect` (default `true`, today's behaviour) for
+  preview pickers that stay open, and its rows are public as `OptionRows` for a
+  picker that composes its own `FullScreenPicker`. `CustomExpandRow` is the
+  "Custom…" row of a presets-plus-custom picker, revealing its editor
+  (typically `CustomAmountEditor`) as one connected container.
+  `GroupedSwitchRow` is the settings toggle row where the whole row flips the
+  switch. `GroupedHint` is the muted text beside the cards (settings hints,
+  picker descriptions), and `ExpandIcon` the turning chevron, now also used by
+  `InstructionSteps`.
+- **`components`** — `IconInfoCard`, the tonal icon-plus-content card behind
+  Calendula's event detail and edit screens (optionally clickable, a top-aligned
+  icon for multi-line fields, a `header` line the icon centres on).
+- **`components`** — `OnboardingScaffold` takes `headline` and `supporting`,
+  the centred title and muted explanation most steps open `body` with; `body`
+  now defaults to empty. `OnboardingPrimaryButton` is the full-width 56dp
+  call-to-action, with an optional trailing icon. Existing calls are unchanged.
+- **`components`** — `LanguagePickerRow` takes `header` and `predictiveBack`,
+  forwarded to its `OptionPicker`, so an app with a "help translate" row above
+  the languages can drop its own copy of the row. Both default to today's
+  behaviour.
+- **`core-locale`** — `relativeTimeAgo(epochMillis, nowMillis, minResolution)`,
+  the platform-localised "5 minutes ago" Calendula's backup and special-dates
+  status lines build through `DateUtils.getRelativeTimeSpanString`.
+- **`core-reminders`** — `ReminderOverride.minutesOrEmpty()`, the lead times of
+  a `Minutes` override and empty for `Inherit`/`None`.
+- **`core-android`** (new module) — the small Android plumbing Calendula's data
+  layer writes over and over, in an Android library with no Compose and no DI:
+  `Context.broadcastTicks(vararg actions)` (a Flow that ticks once on
+  collection and again on each broadcast, behind its `TodaySource` and
+  `ZoneSource`), `BroadcastReceiver.goAsync(context) { }` (the
+  `goAsync()` + one-off scope + `finish()` dance), `Context.hasPermission`,
+  `AlarmManager.canScheduleExactCompat()` and `AlarmManager.setWakeup(…)`
+  (exact and allow-while-idle when the capability is held, the inexact
+  allow-while-idle alarm otherwise), and
+  `Flow.stateWhileSubscribed(scope, initialValue, stopTimeoutMillis = 5_000)`.
+
+- **`identity`** — a pure-black (AMOLED) dark theme. `ColorScheme.toPureBlack()`
+  sets `background`, `surface`, `surfaceDim` and `surfaceContainerLowest` to
+  #000 and pulls the other containers down towards black, keeping their hue
+  tint, so grid tiles drawn as containers over `surface` still show their
+  gaps. `FloretExpressiveTheme` gains `pureBlack` (default `false`), which
+  applies it to the dark scheme, dynamic or app-supplied.
+- **`core-prefs`** — `ThemeMode.BLACK`, dark with pure-black surfaces.
+  `isDark` treats it as dark, and the new `ThemeMode.isPureBlack` is what an
+  app passes to the theme's `pureBlack`. It's stored as `"BLACK"` under the
+  same `theme_mode` key; a build without it reads that as `SYSTEM`.
 
 - **`glance`** (new module) — the family's shared home-screen-widget plumbing
   and M3 Expressive widget vocabulary, built on Jetpack Glance:
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 684959a..94fcd76 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -38,6 +38,7 @@ practical how.
 ./gradlew :core-crash:testDebugUnitTest
 ./gradlew :core-prefs:testDebugUnitTest
 ./gradlew :core-di:test
+./gradlew :core-android:testDebugUnitTest
 ./gradlew :identity:assembleDebug
 ./gradlew build                        # everything
 ```
diff --git a/README.md b/README.md
index 821e7ef..6054b1d 100644
--- a/README.md
+++ b/README.md
@@ -37,12 +37,13 @@ See [`docs/ARCHITECTURE.md`](docs/ARCHITECTURE.md) for the full consumption mode
 |--------|------|---------------|
 | `core-time` | JVM | Date/time helpers: `DayWindow` local-day windows, locale/zone-aware `Instant` formatting, `TimeBridge` (millis ↔ `Instant`). No Android, no deps. |
 | `core-reminders` | JVM | Reminder-lead plumbing: the lead-time unit model (`ReminderUnit`, `decomposeReminderMinutes`), the per-target override model (`ReminderOverride` + `reminderLeadFor` / `applyReminderOverride`) and the stored-format codec (`ReminderOverrideCodec`, separators configurable per app). Each app layers its own DataStore + string labels on top. |
-| `core-locale` | Android | Everything "what language are we in". Per-app language plumbing (`AppLanguage`): read the shipped languages from the app's `res/xml/locales_config.xml`, get/set the applied language via `AppCompatDelegate`, render each language's autonym. Plus `currentLocale()` (observes the applied language from Compose) and `localizedDateFormatter(locale, skeleton)` (lays a field skeleton out in the locale's own order). The app passes its own `locales_config`. |
+| `core-locale` | Android | Everything "what language are we in". Per-app language plumbing (`AppLanguage`): read the shipped languages from the app's `res/xml/locales_config.xml`, get/set the applied language via `AppCompatDelegate`, render each language's autonym. Plus `currentLocale()` (observes the applied language from Compose) and `localizedDateFormatter(locale, skeleton)` (lays a field skeleton out in the locale's own order) and `relativeTimeAgo(…)` ("5 minutes ago"). The app passes its own `locales_config`. |
 | `core-prefs` | Android | The typed DataStore layer: `Pref<T>` + `PrefStore` (typed read/write, distinct-until-changed flows), `toEnum()` for values that degrade instead of throwing, and the family's shared appearance prefs (`ThemeMode`, `dynamicColor`). The store's name and construction stay with the app. |
 | `core-di` | JVM | The shared DI vocabulary: `@IoDispatcher`, `@DefaultDispatcher`, `@ApplicationScope` and the Hilt module that provides them. |
+| `core-android` | Android | Small Android plumbing: `broadcastTicks` (a Flow that ticks on system broadcasts), a coroutine `BroadcastReceiver.goAsync { }`, `Context.hasPermission`, `AlarmManager.setWakeup` (exact, or inexact allow-while-idle without the capability) and `Flow.stateWhileSubscribed`. No Compose, no DI. |
 | `core-crash` | Android | Privacy-respecting on-device crash capture + report dialog + issue-tracker hand-off. Parameterized per app via `CrashConfig`. |
 | `identity` | Android | The M3 Expressive theme factory `FloretExpressiveTheme(…)`, `rememberNavSlideSpec()`, the content transitions (`expandEnter`/`collapseExit`/`itemEnter`/…) and the `predictiveBack` peek. Each app supplies its own seed/palette. |
-| `components` | Android | Shared Compose vocabulary + recipes: `GroupedSurface`/`GroupedRow`, `InlineTextField`, `OptionCard`, `CollapsingScaffold`, `OptionPicker`, `ReorderableColumn`, `DebugRibbon`, `pastelize()`, `DialogControls`, `OnboardingScaffold`, `OptionalFormSection`, `AboutCard`, `LanguagePickerRow`, `SnackChip`. |
+| `components` | Android | Shared Compose vocabulary + recipes: `GroupedSurface`/`GroupedRow`/`GroupedSwitchRow`/`GroupedHint`, `IconInfoCard`, `InlineTextField`, `OptionCard`, `CollapsingScaffold`, `OptionPicker`/`OptionRows`/`CustomExpandRow`, `ReorderableColumn`, `DebugRibbon`, `pastelize()`, `DialogControls`, `OnboardingScaffold`, `OptionalFormSection`, `AboutCard`, `LanguagePickerRow`, `SnackChip`. |
 | `glance` | Android | Home-screen-widget plumbing on Jetpack Glance: `FloretGlanceTheme`, the rounded `WidgetSurface` (solid/tinted/transparent backgrounds), `WidgetHeader`/`WidgetActionButton`, the position-aware `WidgetGroupedRow`, `WidgetMessage`, `WidgetRollover` (the midnight-rollover alarm) and `FloretWidgetUpdateReceiver`. App supplies its own colour schemes, data and receiver glue. |
 
 _The principle: the **mechanics** are shared, the **look** stays per-app. See
@@ -63,5 +64,6 @@ See [`docs/`](docs/) — start with [`docs/README.md`](docs/README.md)
 ./gradlew :core-crash:testDebugUnitTest
 ./gradlew :core-prefs:testDebugUnitTest
 ./gradlew :core-di:test
+./gradlew :core-android:testDebugUnitTest
 ./gradlew build                    # everything (Android modules need an SDK; see above)
 ```
diff --git a/components/src/main/kotlin/de/jeanlucmakiola/floret/components/FormSection.kt b/components/src/main/kotlin/de/jeanlucmakiola/floret/components/FormSection.kt
index d190547..b657e0e 100644
--- a/components/src/main/kotlin/de/jeanlucmakiola/floret/components/FormSection.kt
+++ b/components/src/main/kotlin/de/jeanlucmakiola/floret/components/FormSection.kt
@@ -21,6 +21,6 @@ fun OptionalFormSection(visible: Boolean, content: @Composable ColumnScope.() ->
         enter = expandEnter(),
         exit = collapseExit(),
     ) {
-        Column(modifier = Modifier.fillMaxWidth(), content = content)
+        Column(modifier = Modifier.fillMaxWidth().revealOnFocus(), content = content)
     }
 }
diff --git a/components/src/main/kotlin/de/jeanlucmakiola/floret/components/GroupedList.kt b/components/src/main/kotlin/de/jeanlucmakiola/floret/components/GroupedList.kt
index 292fe67..06e1dec 100644
--- a/components/src/main/kotlin/de/jeanlucmakiola/floret/components/GroupedList.kt
+++ b/components/src/main/kotlin/de/jeanlucmakiola/floret/components/GroupedList.kt
@@ -122,7 +122,7 @@ fun GroupedSurface(
         position == Position.Top || position == Position.Middle -> Modifier.padding(bottom = 2.dp)
         else -> Modifier
     }
-    val base = modifier.fillMaxWidth().then(gap)
+    val base = modifier.fillMaxWidth().then(gap).revealOnFocus()
     val haptics = LocalHapticFeedback.current
     when {
         onLongClick != null -> Surface(
@@ -159,6 +159,10 @@ fun GroupedSurface(
  * the inter-row gap for a caller that owns its own uniform spacing, e.g.
  * [ReorderableColumn]. [onLongClick] (see [GroupedSurface]) adds a long-press to
  * the row.
+ *
+ * [checked] marks a picker row as the chosen one: it implies [selected] and puts
+ * [SelectedCheck] in the trailing slot when [trailing] is null — the single-select
+ * picker row without the `if (selected) { { SelectedCheck() } } else null` dance.
  */
 @Composable
 fun GroupedRow(
@@ -176,6 +180,7 @@ fun GroupedRow(
     trailing: @Composable (() -> Unit)? = null,
     onClick: (() -> Unit)? = null,
     onLongClick: (() -> Unit)? = null,
+    checked: Boolean = false,
 ) = GroupedRow(
     title = AnnotatedString(title),
     position = position,
@@ -191,6 +196,7 @@ fun GroupedRow(
     trailing = trailing,
     onClick = onClick,
     onLongClick = onLongClick,
+    checked = checked,
 )
 
 /**
@@ -215,8 +221,15 @@ fun GroupedRow(
     trailing: @Composable (() -> Unit)? = null,
     onClick: (() -> Unit)? = null,
     onLongClick: (() -> Unit)? = null,
+    checked: Boolean = false,
 ) {
-    val itemColors = if (selected) {
+    val highlighted = selected || checked
+    val trailingContent = trailing ?: if (checked) {
+        { SelectedCheck() }
+    } else {
+        null
+    }
+    val itemColors = if (highlighted) {
         ListItemDefaults.colors(
             containerColor = Color.Transparent,
             headlineColor = MaterialTheme.colorScheme.onSecondaryContainer,
@@ -246,7 +259,7 @@ fun GroupedRow(
         ListItemDefaults.colors(containerColor = Color.Transparent)
     }
     val containerColor = when {
-        selected -> MaterialTheme.colorScheme.secondaryContainer
+        highlighted -> MaterialTheme.colorScheme.secondaryContainer
         container != null -> container
         else -> MaterialTheme.colorScheme.surfaceContainerHigh
     }
@@ -262,7 +275,7 @@ fun GroupedRow(
             headlineContent = { Text(title) },
             supportingContent = summary?.let { text -> { Text(text) } },
             leadingContent = leading,
-            trailingContent = trailing,
+            trailingContent = trailingContent,
             colors = itemColors,
             modifier = Modifier.heightIn(min = minHeight),
         )
diff --git a/components/src/main/kotlin/de/jeanlucmakiola/floret/components/GroupedRowRecipes.kt b/components/src/main/kotlin/de/jeanlucmakiola/floret/components/GroupedRowRecipes.kt
new file mode 100644
index 0000000..5070150
--- /dev/null
+++ b/components/src/main/kotlin/de/jeanlucmakiola/floret/components/GroupedRowRecipes.kt
@@ -0,0 +1,130 @@
+package de.jeanlucmakiola.floret.components
+
+import androidx.compose.animation.AnimatedVisibility
+import androidx.compose.animation.core.animateFloatAsState
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.padding
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.rounded.KeyboardArrowDown
+import androidx.compose.material3.Icon
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Switch
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.rotate
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.text.TextStyle
+import androidx.compose.ui.unit.Dp
+import androidx.compose.ui.unit.dp
+import de.jeanlucmakiola.floret.identity.collapseExit
+import de.jeanlucmakiola.floret.identity.expandEnter
+
+/**
+ * A [GroupedRow] with a trailing [Switch], where a tap anywhere on the row flips
+ * it — the family's settings toggle. [enabled] false dims the row and disables
+ * both the row and the switch.
+ */
+@Composable
+fun GroupedSwitchRow(
+    title: String,
+    checked: Boolean,
+    onCheckedChange: (Boolean) -> Unit,
+    position: Position,
+    modifier: Modifier = Modifier,
+    summary: String? = null,
+    enabled: Boolean = true,
+    leading: @Composable (() -> Unit)? = null,
+) {
+    GroupedRow(
+        title = title,
+        position = position,
+        modifier = modifier,
+        summary = summary,
+        dimmed = !enabled,
+        leading = leading,
+        trailing = {
+            Switch(checked = checked, onCheckedChange = onCheckedChange, enabled = enabled)
+        },
+        onClick = if (enabled) ({ onCheckedChange(!checked) }) else null,
+    )
+}
+
+/**
+ * The "Custom…" row that closes a presets-plus-custom picker: a [GroupedRow] that
+ * toggles [expanded] on tap and reveals [editor] beneath it (typically a
+ * [CustomAmountEditor]). Expanded, the row takes [Position.Top] so it and the
+ * editor read as one container; collapsed it sits at [position].
+ *
+ * [checked] marks the custom value as the current choice, as on the preset rows;
+ * the caller names it through [title]/[summary].
+ */
+@Composable
+fun CustomExpandRow(
+    title: String,
+    position: Position,
+    expanded: Boolean,
+    onExpandedChange: (Boolean) -> Unit,
+    modifier: Modifier = Modifier,
+    summary: String? = null,
+    checked: Boolean = false,
+    editor: @Composable () -> Unit,
+) {
+    Column(modifier) {
+        GroupedRow(
+            title = title,
+            summary = summary,
+            position = if (expanded) Position.Top else position,
+            onClick = { onExpandedChange(!expanded) },
+            checked = checked,
+        )
+        AnimatedVisibility(
+            visible = expanded,
+            enter = expandEnter(),
+            exit = collapseExit(),
+        ) {
+            editor()
+        }
+    }
+}
+
+/**
+ * Muted supporting text outside the cards — under a [GroupedSectionHeader], or
+ * above a picker's rows — inset to [GroupedListInset] so it shares their edge.
+ * [style] and [verticalPadding] cover the denser variants (`bodySmall`, 8dp under
+ * a picker title).
+ */
+@Composable
+fun GroupedHint(
+    text: String,
+    modifier: Modifier = Modifier,
+    style: TextStyle = MaterialTheme.typography.bodyMedium,
+    verticalPadding: Dp = 4.dp,
+) {
+    Text(
+        text = text,
+        style = style,
+        color = MaterialTheme.colorScheme.onSurfaceVariant,
+        modifier = modifier.padding(horizontal = GroupedListInset, vertical = verticalPadding),
+    )
+}
+
+/**
+ * The open/shut chevron for a row that folds content beneath it; turns over as
+ * [expanded] changes. Decorative — the row carries the semantics.
+ */
+@Composable
+fun ExpandIcon(
+    expanded: Boolean,
+    modifier: Modifier = Modifier,
+    tint: Color = MaterialTheme.colorScheme.onSurfaceVariant,
+) {
+    val turn by animateFloatAsState(if (expanded) 180f else 0f, label = "expand-icon")
+    Icon(
+        imageVector = Icons.Rounded.KeyboardArrowDown,
+        contentDescription = null,
+        tint = tint,
+        modifier = modifier.rotate(turn),
+    )
+}
diff --git a/components/src/main/kotlin/de/jeanlucmakiola/floret/components/IconInfoCard.kt b/components/src/main/kotlin/de/jeanlucmakiola/floret/components/IconInfoCard.kt
new file mode 100644
index 0000000..dcecba8
--- /dev/null
+++ b/components/src/main/kotlin/de/jeanlucmakiola/floret/components/IconInfoCard.kt
@@ -0,0 +1,83 @@
+package de.jeanlucmakiola.floret.components
+
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.ColumnScope
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.layout.width
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.material3.Icon
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Surface
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.graphics.vector.ImageVector
+import androidx.compose.ui.unit.Dp
+import androidx.compose.ui.unit.dp
+
+/**
+ * A free-standing info card: a tonal container with [icon] in a 24dp gutter on
+ * the left and [content] beside it — a detail screen's "where / when / repeats"
+ * cards, or the same fields on an edit form.
+ *
+ * [onClick] makes the whole card tappable. [iconAlignment] Top with an
+ * [iconTopPadding] lines the icon up with a multi-line field's first line. A
+ * tall card passes its first line as [header]: the icon centres on that, and
+ * [content] continues below it on the same text column.
+ */
+@Composable
+fun IconInfoCard(
+    icon: ImageVector,
+    iconContentDescription: String?,
+    modifier: Modifier = Modifier,
+    iconTint: Color = MaterialTheme.colorScheme.onSurfaceVariant,
+    onClick: (() -> Unit)? = null,
+    iconAlignment: Alignment.Vertical = Alignment.CenterVertically,
+    iconTopPadding: Dp = 0.dp,
+    header: (@Composable ColumnScope.() -> Unit)? = null,
+    content: @Composable ColumnScope.() -> Unit,
+) {
+    val shape = RoundedCornerShape(16.dp)
+    val color = MaterialTheme.colorScheme.surfaceContainerHigh
+    val inner: @Composable () -> Unit = {
+        if (header != null) {
+            Column(Modifier.padding(16.dp)) {
+                Row(verticalAlignment = Alignment.CenterVertically) {
+                    CardIcon(icon, iconContentDescription, iconTint, Modifier)
+                    Spacer(Modifier.width(IconGap))
+                    Column(Modifier.weight(1f), content = header)
+                }
+                Column(Modifier.padding(start = IconSize + IconGap), content = content)
+            }
+        } else {
+            Row(Modifier.padding(16.dp), verticalAlignment = iconAlignment) {
+                CardIcon(icon, iconContentDescription, iconTint, Modifier.padding(top = iconTopPadding))
+                Spacer(Modifier.width(IconGap))
+                Column(Modifier.weight(1f), content = content)
+            }
+        }
+    }
+    if (onClick != null) {
+        Surface(onClick = onClick, color = color, shape = shape, modifier = modifier.fillMaxWidth()) { inner() }
+    } else {
+        Surface(color = color, shape = shape, modifier = modifier.fillMaxWidth()) { inner() }
+    }
+}
+
+@Composable
+private fun CardIcon(icon: ImageVector, contentDescription: String?, tint: Color, modifier: Modifier) {
+    Icon(
+        imageVector = icon,
+        contentDescription = contentDescription,
+        tint = tint,
+        modifier = modifier.size(IconSize),
+    )
+}
+
+private val IconSize = 24.dp
+private val IconGap = 16.dp
diff --git a/components/src/main/kotlin/de/jeanlucmakiola/floret/components/InlineTextField.kt b/components/src/main/kotlin/de/jeanlucmakiola/floret/components/InlineTextField.kt
index 4ec755a..a8c2b13 100644
--- a/components/src/main/kotlin/de/jeanlucmakiola/floret/components/InlineTextField.kt
+++ b/components/src/main/kotlin/de/jeanlucmakiola/floret/components/InlineTextField.kt
@@ -91,6 +91,6 @@ fun InlineTextField(
                 innerTextField()
             }
         },
-        modifier = modifier,
+        modifier = modifier.revealOnFocus(),
     )
 }
diff --git a/components/src/main/kotlin/de/jeanlucmakiola/floret/components/InstructionSteps.kt b/components/src/main/kotlin/de/jeanlucmakiola/floret/components/InstructionSteps.kt
index 4f2dca2..3571bdb 100644
--- a/components/src/main/kotlin/de/jeanlucmakiola/floret/components/InstructionSteps.kt
+++ b/components/src/main/kotlin/de/jeanlucmakiola/floret/components/InstructionSteps.kt
@@ -1,6 +1,5 @@
 package de.jeanlucmakiola.floret.components
 
-import androidx.compose.animation.core.animateFloatAsState
 import androidx.compose.foundation.background
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
@@ -9,7 +8,6 @@ import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.shape.CircleShape
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.rounded.Check
-import androidx.compose.material.icons.rounded.KeyboardArrowDown
 import androidx.compose.material3.Icon
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Text
@@ -21,7 +19,6 @@ import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
-import androidx.compose.ui.draw.rotate
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.unit.dp
 
@@ -75,7 +72,7 @@ fun InstructionSteps(
                     minHeight = 56.dp,
                     // No disc: the empty leading slot is what tells the header
                     // apart from the numbered rows it opens.
-                    trailing = { Chevron(open) },
+                    trailing = { ExpandIcon(open) },
                     onClick = { open = !open },
                 )
             }
@@ -153,22 +150,5 @@ fun StepNumber(number: Int, done: Boolean = false) {
     }
 }
 
-/**
- * The open/shut marker.
- *
- * Decorative: the row it sits on carries the name and the click, so a screen
- * reader announcing a chevron as well would be describing the furniture.
- */
-@Composable
-private fun Chevron(open: Boolean) {
-    val turn by animateFloatAsState(if (open) 180f else 0f, label = "instruction-chevron")
-    Icon(
-        imageVector = Icons.Rounded.KeyboardArrowDown,
-        contentDescription = null,
-        tint = MaterialTheme.colorScheme.onSurfaceVariant,
-        modifier = Modifier.rotate(turn),
-    )
-}
-
 /** The leading slot's own size, matched to the icons that usually fill it. */
 private val StepNumberSize = 28.dp
diff --git a/components/src/main/kotlin/de/jeanlucmakiola/floret/components/Onboarding.kt b/components/src/main/kotlin/de/jeanlucmakiola/floret/components/Onboarding.kt
index b82e6fd..22e50a5 100644
--- a/components/src/main/kotlin/de/jeanlucmakiola/floret/components/Onboarding.kt
+++ b/components/src/main/kotlin/de/jeanlucmakiola/floret/components/Onboarding.kt
@@ -19,6 +19,8 @@ import androidx.compose.foundation.layout.width
 import androidx.compose.foundation.rememberScrollState
 import androidx.compose.foundation.shape.CircleShape
 import androidx.compose.foundation.verticalScroll
+import androidx.compose.material3.Button
+import androidx.compose.material3.ButtonDefaults
 import androidx.compose.material3.Icon
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Scaffold
@@ -30,6 +32,7 @@ import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
 import androidx.compose.ui.graphics.vector.ImageVector
 import androidx.compose.ui.semantics.clearAndSetSemantics
+import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.unit.Dp
 import androidx.compose.ui.unit.dp
 
@@ -66,6 +69,10 @@ object OnboardingSpace {
  * the scrolling content, for a step whose content is taller than the screen: a
  * pinned bar there eats the room the content needs and hides the fact that
  * there is more of it below.
+ *
+ * [headline] and [supporting] are the step's centred title and muted
+ * explanation, drawn at the top of [body] — the block nearly every step opens
+ * with. [body] then continues below them, and may be left out entirely.
  */
 @Composable
 fun OnboardingScaffold(
@@ -77,7 +84,9 @@ fun OnboardingScaffold(
     topSpacing: Dp = OnboardingSpace.xl,
     contentPadding: Dp = OnboardingSpace.md,
     scrollingActions: Boolean = false,
-    body: @Composable ColumnScope.() -> Unit,
+    headline: String? = null,
+    supporting: String? = null,
+    body: @Composable ColumnScope.() -> Unit = {},
 ) {
     Scaffold(
         modifier = modifier,
@@ -120,6 +129,22 @@ fun OnboardingScaffold(
             Spacer(Modifier.height(topSpacing))
             hero()
             Spacer(Modifier.height(OnboardingSpace.lg))
+            if (headline != null) {
+                Text(
+                    text = headline,
+                    style = MaterialTheme.typography.headlineMedium,
+                    textAlign = TextAlign.Center,
+                )
+            }
+            if (headline != null && supporting != null) Spacer(Modifier.height(12.dp))
+            if (supporting != null) {
+                Text(
+                    text = supporting,
+                    style = MaterialTheme.typography.bodyLarge,
+                    color = MaterialTheme.colorScheme.onSurfaceVariant,
+                    textAlign = TextAlign.Center,
+                )
+            }
             body()
             // No inset of its own: scrolling actions sit inside the content
             // column, so they line up with whatever is above them.
@@ -135,6 +160,37 @@ fun OnboardingScaffold(
     }
 }
 
+/**
+ * The step's main call to action for [OnboardingScaffold]'s `actions`: a
+ * full-width 56dp filled button with a `titleMedium` label, and an optional
+ * [trailingIcon] (e.g. a forward arrow) after it.
+ */
+@Composable
+fun OnboardingPrimaryButton(
+    text: String,
+    onClick: () -> Unit,
+    modifier: Modifier = Modifier,
+    enabled: Boolean = true,
+    trailingIcon: ImageVector? = null,
+) {
+    Button(
+        onClick = onClick,
+        enabled = enabled,
+        modifier = modifier.fillMaxWidth().height(56.dp),
+        contentPadding = if (trailingIcon != null) {
+            ButtonDefaults.ButtonWithIconContentPadding
+        } else {
+            ButtonDefaults.ContentPadding
+        },
+    ) {
+        Text(text = text, style = MaterialTheme.typography.titleMedium)
+        if (trailingIcon != null) {
+            Spacer(Modifier.width(OnboardingSpace.xs))
+            Icon(imageVector = trailingIcon, contentDescription = null, modifier = Modifier.size(20.dp))
+        }
+    }
+}
+
 /** The call-to-action stack, wherever the shell has put it. */
 @Composable
 private fun ActionsColumn(
diff --git a/components/src/main/kotlin/de/jeanlucmakiola/floret/components/OptionPicker.kt b/components/src/main/kotlin/de/jeanlucmakiola/floret/components/OptionPicker.kt
index dd5e550..eca0fba 100644
--- a/components/src/main/kotlin/de/jeanlucmakiola/floret/components/OptionPicker.kt
+++ b/components/src/main/kotlin/de/jeanlucmakiola/floret/components/OptionPicker.kt
@@ -105,6 +105,9 @@ fun FullScreenPicker(
  * the cheap middle rung of the richness ladder described on [FullScreenPicker]:
  * every option shows its effect at once and stays comparable, without the cost
  * of a live preview.
+ *
+ * [dismissOnSelect] closes the picker on a pick (the default). Pass false for a
+ * preview picker, which applies at once and stays open (see [FullScreenPicker]).
  */
 @Composable
 fun <T> OptionPicker(
@@ -118,28 +121,49 @@ fun <T> OptionPicker(
     leading: (@Composable (T) -> Unit)? = null,
     header: (@Composable ColumnScope.() -> Unit)? = null,
     predictiveBack: Boolean = false,
+    dismissOnSelect: Boolean = true,
 ) {
     FullScreenPicker(title = title, onDismiss = onDismiss, predictiveBack = predictiveBack) {
         header?.invoke(this)
-        options.forEachIndexed { index, option ->
-            val isSelected = option == selected
-            GroupedRow(
-                title = label(option),
-                summary = summary?.invoke(option),
-                position = positionOf(index, options.size),
-                selected = isSelected,
-                leading = leading?.let { { it(option) } },
-                trailing = if (isSelected) {
-                    { SelectedCheck() }
-                } else {
-                    null
-                },
-                onClick = {
-                    onSelect(option)
-                    onDismiss()
-                },
-            )
-        }
+        OptionRows(
+            options = options,
+            selected = selected,
+            label = label,
+            onSelect = {
+                onSelect(it)
+                if (dismissOnSelect) onDismiss()
+            },
+            summary = summary,
+            leading = leading,
+        )
+    }
+}
+
+/**
+ * [OptionPicker]'s option list on its own: one connected run of [GroupedRow]s,
+ * the current option highlighted and checked. For a picker that composes its own
+ * [FullScreenPicker] — a preview above the rows, a description between — but
+ * wants the standard rows underneath. [onSelect] only reports the pick; closing
+ * the picker is the caller's call.
+ */
+@Composable
+fun <T> OptionRows(
+    options: List<T>,
+    selected: T,
+    label: @Composable (T) -> String,
+    onSelect: (T) -> Unit,
+    summary: (@Composable (T) -> String?)? = null,
+    leading: (@Composable (T) -> Unit)? = null,
+) {
+    options.forEachIndexed { index, option ->
+        GroupedRow(
+            title = label(option),
+            summary = summary?.invoke(option),
+            position = positionOf(index, options.size),
+            leading = leading?.let { { it(option) } },
+            onClick = { onSelect(option) },
+            checked = option == selected,
+        )
     }
 }
 
diff --git a/components/src/main/kotlin/de/jeanlucmakiola/floret/components/RevealOnFocus.kt b/components/src/main/kotlin/de/jeanlucmakiola/floret/components/RevealOnFocus.kt
new file mode 100644
index 0000000..7f80f16
--- /dev/null
+++ b/components/src/main/kotlin/de/jeanlucmakiola/floret/components/RevealOnFocus.kt
@@ -0,0 +1,62 @@
+package de.jeanlucmakiola.floret.components
+
+import androidx.compose.foundation.ExperimentalFoundationApi
+import androidx.compose.foundation.layout.ExperimentalLayoutApi
+import androidx.compose.foundation.layout.WindowInsets
+import androidx.compose.foundation.layout.ime
+import androidx.compose.foundation.layout.imeAnimationTarget
+import androidx.compose.foundation.relocation.BringIntoViewRequester
+import androidx.compose.foundation.relocation.bringIntoViewRequester
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.runtime.snapshotFlow
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.composed
+import androidx.compose.ui.focus.onFocusChanged
+import androidx.compose.ui.layout.onSizeChanged
+import androidx.compose.ui.platform.LocalDensity
+import androidx.compose.ui.unit.IntSize
+import kotlinx.coroutines.flow.distinctUntilChanged
+import kotlinx.coroutines.flow.filterNotNull
+
+/**
+ * Scrolls this whole element into view while anything inside it has focus — once
+ * the keyboard has finished opening, and again whenever the element resizes.
+ *
+ * A text field on its own only brings its text line into view, so a card's
+ * padding, its label and whatever appears below the field (suggestions, chips)
+ * stay under the keyboard. [InlineTextField], [GroupedSurface] and
+ * [OptionalFormSection] apply it already; add it to an app's own card or row
+ * that holds an input. Needs a scrolling parent whose viewport shrinks with the
+ * keyboard (`imePadding`).
+ *
+ * The keyboard is only read while focused, so an unfocused element never
+ * recomposes as the keyboard animates.
+ */
+@OptIn(ExperimentalFoundationApi::class, ExperimentalLayoutApi::class)
+fun Modifier.revealOnFocus(): Modifier = composed {
+    val requester = remember { BringIntoViewRequester() }
+    var focused by remember { mutableStateOf(false) }
+    var size by remember { mutableStateOf(IntSize.Zero) }
+    val density = LocalDensity.current
+    val ime = WindowInsets.ime
+    val imeTarget = WindowInsets.imeAnimationTarget
+    LaunchedEffect(focused) {
+        if (!focused) return@LaunchedEffect
+        // Reveal against the final viewport, not one frame of the keyboard sliding in.
+        snapshotFlow {
+            val now = ime.getBottom(density)
+            if (now == imeTarget.getBottom(density)) now to size else null
+        }
+            .filterNotNull()
+            .distinctUntilChanged()
+            .collect { requester.bringIntoView() }
+    }
+    this
+        .bringIntoViewRequester(requester)
+        .onSizeChanged { size = it }
+        .onFocusChanged { focused = it.hasFocus }
+}
diff --git a/components/src/main/kotlin/de/jeanlucmakiola/floret/components/SettingsRecipes.kt b/components/src/main/kotlin/de/jeanlucmakiola/floret/components/SettingsRecipes.kt
index 3f82d9a..e8ec3db 100644
--- a/components/src/main/kotlin/de/jeanlucmakiola/floret/components/SettingsRecipes.kt
+++ b/components/src/main/kotlin/de/jeanlucmakiola/floret/components/SettingsRecipes.kt
@@ -5,6 +5,7 @@ import android.net.Uri
 import androidx.annotation.XmlRes
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.ColumnScope
 import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.PaddingValues
@@ -111,7 +112,8 @@ fun AboutCard(
  * [AppLanguage]. The choice is mirrored locally so the row updates instantly
  * before the activity recreation lands. [autoLabel] names the follow-the-system
  * option (the `null` tag); [localesConfig] is the app's `res/xml/locales_config`;
- * [leading] is the row's icon.
+ * [leading] is the row's icon. [header] and [predictiveBack] are forwarded to the
+ * picker's [OptionPicker] (e.g. a "help translate" row above the languages).
  */
 @Composable
 fun LanguagePickerRow(
@@ -119,6 +121,8 @@ fun LanguagePickerRow(
     title: String,
     autoLabel: String,
     @XmlRes localesConfig: Int,
+    header: (@Composable ColumnScope.() -> Unit)? = null,
+    predictiveBack: Boolean = false,
     leading: @Composable () -> Unit,
 ) {
     val context = LocalContext.current
@@ -148,6 +152,8 @@ fun LanguagePickerRow(
                 AppLanguage.apply(context, it)
             },
             onDismiss = { showDialog = false },
+            header = header,
+            predictiveBack = predictiveBack,
         )
     }
 }
diff --git a/core-android/build.gradle.kts b/core-android/build.gradle.kts
new file mode 100644
index 0000000..b386c91
--- /dev/null
+++ b/core-android/build.gradle.kts
@@ -0,0 +1,47 @@
+// core-android — small Android plumbing every app in the family writes again:
+// a broadcast-driven tick Flow, a coroutine `goAsync` for receivers, a
+// permission check, the exact-or-inexact alarm wake-up, and the
+// `stateIn(WhileSubscribed(5s))` idiom. No Compose and no DI, so only the
+// Android library plugin is applied; coroutines are part of the public API.
+plugins {
+    alias(libs.plugins.android.library)
+}
+
+android {
+    namespace = "de.jeanlucmakiola.floret.android"
+    compileSdk = 37
+
+    defaultConfig {
+        minSdk = 29
+    }
+
+    compileOptions {
+        sourceCompatibility = JavaVersion.VERSION_17
+        targetCompatibility = JavaVersion.VERSION_17
+    }
+
+    testOptions {
+        unitTests {
+            all { it.useJUnitPlatform() }
+            isReturnDefaultValues = true
+        }
+    }
+}
+
+kotlin {
+    compilerOptions {
+        jvmTarget = org.jetbrains.kotlin.gradle.dsl.JvmTarget.JVM_17
+    }
+}
+
+dependencies {
+    // `Flow`/`StateFlow`/`CoroutineScope` appear in the public API.
+    api(libs.kotlinx.coroutines.core)
+    implementation(libs.androidx.core.ktx)
+
+    testImplementation(libs.junit.jupiter.api)
+    testRuntimeOnly(libs.junit.jupiter.engine)
+    testRuntimeOnly(libs.junit.platform.launcher)
+    testImplementation(libs.truth)
+    testImplementation(libs.kotlinx.coroutines.test)
+}
diff --git a/core-android/src/main/kotlin/de/jeanlucmakiola/floret/android/Alarms.kt b/core-android/src/main/kotlin/de/jeanlucmakiola/floret/android/Alarms.kt
new file mode 100644
index 0000000..9cf2655
--- /dev/null
+++ b/core-android/src/main/kotlin/de/jeanlucmakiola/floret/android/Alarms.kt
@@ -0,0 +1,32 @@
+package de.jeanlucmakiola.floret.android
+
+import android.app.AlarmManager
+import android.app.PendingIntent
+import android.os.Build
+
+/**
+ * True below API 31 (no restriction), and on 31+ when the exact-alarm capability
+ * is held — `USE_EXACT_ALARM`, or a `SCHEDULE_EXACT_ALARM` the user hasn't
+ * revoked.
+ */
+fun AlarmManager.canScheduleExactCompat(): Boolean =
+    Build.VERSION.SDK_INT < Build.VERSION_CODES.S || canScheduleExactAlarms()
+
+/**
+ * A doze-proof wake-up at [triggerAtMillis]: exact when [canScheduleExactCompat],
+ * otherwise the inexact allow-while-idle alarm, which needs no permission.
+ * Returns whether the exact alarm was set.
+ */
+fun AlarmManager.setWakeup(
+    triggerAtMillis: Long,
+    operation: PendingIntent,
+    type: Int = AlarmManager.RTC_WAKEUP,
+): Boolean {
+    val exact = canScheduleExactCompat()
+    if (exact) {
+        setExactAndAllowWhileIdle(type, triggerAtMillis, operation)
+    } else {
+        setAndAllowWhileIdle(type, triggerAtMillis, operation)
+    }
+    return exact
+}
diff --git a/core-android/src/main/kotlin/de/jeanlucmakiola/floret/android/Broadcasts.kt b/core-android/src/main/kotlin/de/jeanlucmakiola/floret/android/Broadcasts.kt
new file mode 100644
index 0000000..36d8c29
--- /dev/null
+++ b/core-android/src/main/kotlin/de/jeanlucmakiola/floret/android/Broadcasts.kt
@@ -0,0 +1,28 @@
+package de.jeanlucmakiola.floret.android
+
+import android.content.BroadcastReceiver
+import android.content.Context
+import android.content.Intent
+import android.content.IntentFilter
+import androidx.core.content.ContextCompat
+import kotlinx.coroutines.channels.awaitClose
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.callbackFlow
+import kotlinx.coroutines.flow.onStart
+
+/**
+ * Emits once on collection and again on every broadcast of [actions], through a
+ * not-exported receiver registered for as long as the flow is collected. Map
+ * each tick to a fresh read of whatever the broadcasts announce — the date, the
+ * zone — rather than reading the intent.
+ */
+fun Context.broadcastTicks(vararg actions: String): Flow<Unit> = callbackFlow {
+    val receiver = object : BroadcastReceiver() {
+        override fun onReceive(context: Context, intent: Intent) {
+            trySend(Unit)
+        }
+    }
+    val filter = IntentFilter().apply { actions.forEach(::addAction) }
+    ContextCompat.registerReceiver(this@broadcastTicks, receiver, filter, ContextCompat.RECEIVER_NOT_EXPORTED)
+    awaitClose { unregisterReceiver(receiver) }
+}.onStart { emit(Unit) }
diff --git a/core-android/src/main/kotlin/de/jeanlucmakiola/floret/android/Flows.kt b/core-android/src/main/kotlin/de/jeanlucmakiola/floret/android/Flows.kt
new file mode 100644
index 0000000..bf3d235
--- /dev/null
+++ b/core-android/src/main/kotlin/de/jeanlucmakiola/floret/android/Flows.kt
@@ -0,0 +1,18 @@
+package de.jeanlucmakiola.floret.android
+
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.SharingStarted
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.stateIn
+
+/**
+ * `stateIn(scope, WhileSubscribed(stopTimeoutMillis), initialValue)` — the
+ * ViewModel idiom: upstream runs while the UI collects and survives a
+ * configuration change inside the timeout.
+ */
+fun <T> Flow<T>.stateWhileSubscribed(
+    scope: CoroutineScope,
+    initialValue: T,
+    stopTimeoutMillis: Long = 5_000L,
+): StateFlow<T> = stateIn(scope, SharingStarted.WhileSubscribed(stopTimeoutMillis), initialValue)
diff --git a/core-android/src/main/kotlin/de/jeanlucmakiola/floret/android/Permissions.kt b/core-android/src/main/kotlin/de/jeanlucmakiola/floret/android/Permissions.kt
new file mode 100644
index 0000000..8a6b987
--- /dev/null
+++ b/core-android/src/main/kotlin/de/jeanlucmakiola/floret/android/Permissions.kt
@@ -0,0 +1,9 @@
+package de.jeanlucmakiola.floret.android
+
+import android.content.Context
+import android.content.pm.PackageManager
+import androidx.core.content.ContextCompat
+
+/** Whether [permission] is currently granted to this app. */
+fun Context.hasPermission(permission: String): Boolean =
+    ContextCompat.checkSelfPermission(this, permission) == PackageManager.PERMISSION_GRANTED
diff --git a/core-android/src/main/kotlin/de/jeanlucmakiola/floret/android/Receivers.kt b/core-android/src/main/kotlin/de/jeanlucmakiola/floret/android/Receivers.kt
new file mode 100644
index 0000000..958a4e4
--- /dev/null
+++ b/core-android/src/main/kotlin/de/jeanlucmakiola/floret/android/Receivers.kt
@@ -0,0 +1,28 @@
+package de.jeanlucmakiola.floret.android
+
+import android.content.BroadcastReceiver
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.SupervisorJob
+import kotlinx.coroutines.launch
+import kotlin.coroutines.CoroutineContext
+
+/**
+ * Runs [block] off the main thread with the broadcast kept alive until it
+ * returns: `goAsync()` plus a one-off scope, finishing the pending result even if
+ * [block] throws. Call it from `onReceive`; the usual ~10s receiver budget still
+ * applies.
+ */
+fun BroadcastReceiver.goAsync(
+    context: CoroutineContext = Dispatchers.IO,
+    block: suspend CoroutineScope.() -> Unit,
+) {
+    val pending = goAsync()
+    CoroutineScope(SupervisorJob() + context).launch {
+        try {
+            block()
+        } finally {
+            pending.finish()
+        }
+    }
+}
diff --git a/core-android/src/test/kotlin/de/jeanlucmakiola/floret/android/StateWhileSubscribedTest.kt b/core-android/src/test/kotlin/de/jeanlucmakiola/floret/android/StateWhileSubscribedTest.kt
new file mode 100644
index 0000000..e0d27c0
--- /dev/null
+++ b/core-android/src/test/kotlin/de/jeanlucmakiola/floret/android/StateWhileSubscribedTest.kt
@@ -0,0 +1,45 @@
+package de.jeanlucmakiola.floret.android
+
+import com.google.common.truth.Truth.assertThat
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.test.advanceTimeBy
+import kotlinx.coroutines.test.runCurrent
+import kotlinx.coroutines.test.runTest
+import org.junit.jupiter.api.Test
+
+@OptIn(ExperimentalCoroutinesApi::class)
+class StateWhileSubscribedTest {
+
+    @Test
+    fun `starts at the initial value and follows upstream while collected`() = runTest {
+        val upstream = MutableStateFlow(1)
+        val state = upstream.stateWhileSubscribed(backgroundScope, initialValue = 0)
+        assertThat(state.value).isEqualTo(0)
+
+        backgroundScope.launch { state.collect {} }
+        runCurrent()
+        assertThat(state.value).isEqualTo(1)
+
+        upstream.value = 2
+        runCurrent()
+        assertThat(state.value).isEqualTo(2)
+    }
+
+    @Test
+    fun `keeps upstream alive for the stop timeout after the last collector leaves`() = runTest {
+        val upstream = MutableStateFlow(1)
+        val state = upstream.stateWhileSubscribed(backgroundScope, initialValue = 0, stopTimeoutMillis = 1_000L)
+
+        val collector = backgroundScope.launch { state.collect {} }
+        runCurrent()
+        collector.cancel()
+        runCurrent()
+        assertThat(upstream.subscriptionCount.value).isEqualTo(1)
+
+        advanceTimeBy(1_001L)
+        runCurrent()
+        assertThat(upstream.subscriptionCount.value).isEqualTo(0)
+    }
+}
diff --git a/core-locale/src/main/kotlin/de/jeanlucmakiola/floret/locale/RelativeTime.kt b/core-locale/src/main/kotlin/de/jeanlucmakiola/floret/locale/RelativeTime.kt
new file mode 100644
index 0000000..376a724
--- /dev/null
+++ b/core-locale/src/main/kotlin/de/jeanlucmakiola/floret/locale/RelativeTime.kt
@@ -0,0 +1,17 @@
+package de.jeanlucmakiola.floret.locale
+
+import android.text.format.DateUtils
+
+/**
+ * "5 minutes ago" / "in 2 hours" for [epochMillis] relative to [nowMillis], in the
+ * process locale, via the platform's `DateUtils`. Spans shorter than
+ * [minResolution] read as the smallest unit ("0 minutes ago"), so a status line
+ * doesn't tick by the second.
+ *
+ * Needs a real Android runtime, like [localizedDateFormatter].
+ */
+fun relativeTimeAgo(
+    epochMillis: Long,
+    nowMillis: Long = System.currentTimeMillis(),
+    minResolution: Long = DateUtils.MINUTE_IN_MILLIS,
+): String = DateUtils.getRelativeTimeSpanString(epochMillis, nowMillis, minResolution).toString()
diff --git a/core-prefs/src/main/kotlin/de/jeanlucmakiola/floret/prefs/Appearance.kt b/core-prefs/src/main/kotlin/de/jeanlucmakiola/floret/prefs/Appearance.kt
index dcb0c22..19a3fc5 100644
--- a/core-prefs/src/main/kotlin/de/jeanlucmakiola/floret/prefs/Appearance.kt
+++ b/core-prefs/src/main/kotlin/de/jeanlucmakiola/floret/prefs/Appearance.kt
@@ -4,16 +4,22 @@ import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.distinctUntilChanged
 import kotlinx.coroutines.flow.map
 
-/** Light/dark override. [SYSTEM] follows the device setting. */
-enum class ThemeMode { SYSTEM, LIGHT, DARK }
+/**
+ * Light/dark override. [SYSTEM] follows the device setting; [BLACK] is dark
+ * with pure-black surfaces (the AMOLED option).
+ */
+enum class ThemeMode { SYSTEM, LIGHT, DARK, BLACK }
 
 /** Resolve to a concrete dark flag; [SYSTEM] defers to [systemDark]. */
 fun ThemeMode.isDark(systemDark: Boolean): Boolean = when (this) {
     ThemeMode.SYSTEM -> systemDark
     ThemeMode.LIGHT -> false
-    ThemeMode.DARK -> true
+    ThemeMode.DARK, ThemeMode.BLACK -> true
 }
 
+/** Whether the theme should draw pure-black surfaces; only [ThemeMode.BLACK] does. */
+val ThemeMode.isPureBlack: Boolean get() = this == ThemeMode.BLACK
+
 /** The two appearance choices every app in the family has. */
 data class Appearance(
     val themeMode: ThemeMode = ThemeMode.SYSTEM,
diff --git a/core-prefs/src/main/kotlin/de/jeanlucmakiola/floret/prefs/Pref.kt b/core-prefs/src/main/kotlin/de/jeanlucmakiola/floret/prefs/Pref.kt
index 785660b..cc7c7cc 100644
--- a/core-prefs/src/main/kotlin/de/jeanlucmakiola/floret/prefs/Pref.kt
+++ b/core-prefs/src/main/kotlin/de/jeanlucmakiola/floret/prefs/Pref.kt
@@ -54,10 +54,20 @@ fun stringSetPref(name: String, default: Set<String> = emptySet()): Pref<Set<Str
 fun nullableStringPref(name: String): Pref<String?> =
     nullablePref(stringPreferencesKey(name), name)
 
+/** Absent reads back as `null`; writing `null` removes the key. */
+fun nullableBooleanPref(name: String): Pref<Boolean?> =
+    nullablePref(booleanPreferencesKey(name), name)
+
 /** Absent reads back as `null`; writing `null` removes the key. */
 fun nullableLongPref(name: String): Pref<Long?> =
     nullablePref(longPreferencesKey(name), name)
 
+/** [pref]'s value in this snapshot, for reading several prefs in one `PrefStore.data` map. */
+operator fun <T> Preferences.get(pref: Pref<T>): T = pref.read(this)
+
+/** Writes [pref] inside a multi-key `PrefStore.edit`, with the same encoding as `PrefStore.set`. */
+operator fun <T> MutablePreferences.set(pref: Pref<T>, value: T) = pref.write(this, value)
+
 /** An absent key reads back as [default]; the value is stored under [key] verbatim. */
 private fun <T : Any> scalarPref(key: Preferences.Key<T>, name: String, default: T): Pref<T> =
     Pref(
diff --git a/core-prefs/src/test/kotlin/de/jeanlucmakiola/floret/prefs/PrefStoreTest.kt b/core-prefs/src/test/kotlin/de/jeanlucmakiola/floret/prefs/PrefStoreTest.kt
index ea34046..7d0360e 100644
--- a/core-prefs/src/test/kotlin/de/jeanlucmakiola/floret/prefs/PrefStoreTest.kt
+++ b/core-prefs/src/test/kotlin/de/jeanlucmakiola/floret/prefs/PrefStoreTest.kt
@@ -281,4 +281,45 @@ class PrefStoreTest {
 
         assertThat(store.get(pref)).isFalse()
     }
+
+    @Test
+    fun `a nullable boolean keeps false apart from unset`(@TempDir tempDir: Path) = runTest {
+        val store = newStore(tempDir)
+        val pref = nullableBooleanPref("b")
+        assertThat(store.get(pref)).isNull()
+
+        store.set(pref, false)
+        assertThat(store.get(pref)).isFalse()
+
+        store.set(pref, null)
+        assertThat(store.get(pref)).isNull()
+    }
+
+    @Test
+    fun `several prefs read from one snapshot`(@TempDir tempDir: Path) = runTest {
+        val store = newStore(tempDir)
+        val count = intPref("count", 1)
+        val mode = enumPref("mode", ThemeMode.SYSTEM)
+        store.set(mode, ThemeMode.DARK)
+
+        val snapshot = store.data.first()
+
+        assertThat(snapshot[count] to snapshot[mode]).isEqualTo(1 to ThemeMode.DARK)
+    }
+
+    @Test
+    fun `a multi-key edit writes typed prefs with their codecs`(@TempDir tempDir: Path) = runTest {
+        val store = newStore(tempDir)
+        val mode = enumPref("mode", ThemeMode.SYSTEM)
+        val folder = nullableStringPref("folder")
+        store.set(folder, "content://x")
+
+        store.edit {
+            it[mode] = ThemeMode.BLACK
+            it[folder] = null
+        }
+
+        assertThat(store.data.first()[stringPreferencesKey("mode")]).isEqualTo("BLACK")
+        assertThat(store.get(folder)).isNull()
+    }
 }
diff --git a/core-prefs/src/test/kotlin/de/jeanlucmakiola/floret/prefs/PrefTest.kt b/core-prefs/src/test/kotlin/de/jeanlucmakiola/floret/prefs/PrefTest.kt
index 4ec96d3..1ba43fb 100644
--- a/core-prefs/src/test/kotlin/de/jeanlucmakiola/floret/prefs/PrefTest.kt
+++ b/core-prefs/src/test/kotlin/de/jeanlucmakiola/floret/prefs/PrefTest.kt
@@ -46,11 +46,11 @@ class PrefTest {
 
     @Test
     fun `the nullable factories default to null`() {
-        val prefs = listOf(nullableStringPref("s"), nullableLongPref("l"))
+        val prefs = listOf(nullableStringPref("s"), nullableLongPref("l"), nullableBooleanPref("b"))
 
         val defaults = prefs.map { it.default }
 
-        assertThat(defaults).containsExactly(null, null)
+        assertThat(defaults).containsExactly(null, null, null)
     }
 
     @Test
diff --git a/core-prefs/src/test/kotlin/de/jeanlucmakiola/floret/prefs/ThemeModeTest.kt b/core-prefs/src/test/kotlin/de/jeanlucmakiola/floret/prefs/ThemeModeTest.kt
index d42d47e..32155d9 100644
--- a/core-prefs/src/test/kotlin/de/jeanlucmakiola/floret/prefs/ThemeModeTest.kt
+++ b/core-prefs/src/test/kotlin/de/jeanlucmakiola/floret/prefs/ThemeModeTest.kt
@@ -42,6 +42,24 @@ class ThemeModeTest {
         assertThat(dark).isTrue()
     }
 
+    @Test
+    fun `isDark lets BLACK override a light system`() {
+        val mode = ThemeMode.BLACK
+
+        val dark = mode.isDark(systemDark = false)
+
+        assertThat(dark).isTrue()
+    }
+
+    @Test
+    fun `isPureBlack is set only for BLACK`() {
+        val modes = ThemeMode.entries
+
+        val pureBlack = modes.filter { it.isPureBlack }
+
+        assertThat(pureBlack).containsExactly(ThemeMode.BLACK)
+    }
+
     @Test
     fun `Appearance defaults to following the system with dynamic colour on`() {
         val appearance = Appearance()
diff --git a/core-reminders/src/main/kotlin/de/jeanlucmakiola/floret/reminders/ReminderOverride.kt b/core-reminders/src/main/kotlin/de/jeanlucmakiola/floret/reminders/ReminderOverride.kt
index a2f7b80..36d86de 100644
--- a/core-reminders/src/main/kotlin/de/jeanlucmakiola/floret/reminders/ReminderOverride.kt
+++ b/core-reminders/src/main/kotlin/de/jeanlucmakiola/floret/reminders/ReminderOverride.kt
@@ -19,6 +19,9 @@ sealed interface ReminderOverride {
     data class Minutes(val minutes: List<Int>) : ReminderOverride
 }
 
+/** The lead times of a [ReminderOverride.Minutes]; empty for [ReminderOverride.Inherit] and [ReminderOverride.None]. */
+fun ReminderOverride.minutesOrEmpty(): List<Int> = (this as? ReminderOverride.Minutes)?.minutes.orEmpty()
+
 /** Distinct, ascending lead times — the canonical form stored and resolved. */
 fun List<Int>.normalizeReminders(): List<Int> = distinct().sorted()
 
diff --git a/core-reminders/src/test/kotlin/de/jeanlucmakiola/floret/reminders/ReminderModelTest.kt b/core-reminders/src/test/kotlin/de/jeanlucmakiola/floret/reminders/ReminderModelTest.kt
index 29d4399..170a6e2 100644
--- a/core-reminders/src/test/kotlin/de/jeanlucmakiola/floret/reminders/ReminderModelTest.kt
+++ b/core-reminders/src/test/kotlin/de/jeanlucmakiola/floret/reminders/ReminderModelTest.kt
@@ -64,4 +64,11 @@ class ReminderModelTest {
         assertThat(reminderOverrideForMinutes(emptyList(), allowInherit = false))
             .isEqualTo(ReminderOverride.None)
     }
+
+    @Test
+    fun `minutesOrEmpty reads the lead times and is empty otherwise`() {
+        assertThat(ReminderOverride.Minutes(listOf(10, 60)).minutesOrEmpty()).containsExactly(10, 60).inOrder()
+        assertThat(ReminderOverride.Inherit.minutesOrEmpty()).isEmpty()
+        assertThat(ReminderOverride.None.minutesOrEmpty()).isEmpty()
+    }
 }
diff --git a/docs/ARCHITECTURE.md b/docs/ARCHITECTURE.md
index dfb1413..41e189e 100644
--- a/docs/ARCHITECTURE.md
+++ b/docs/ARCHITECTURE.md
@@ -75,6 +75,7 @@ should scan the submodule's Gradle scripts (see §5).
 | Plumbing | `core-time` (JVM) | Pure logic; no Android, no deps. |
 | Plumbing | `core-crash` (Android) | Self-contained subsystem; parameterized per app. |
 | Plumbing | `core-prefs` (Android) | Typed DataStore layer. The store's name and construction stay with the app. |
+| Plumbing | `core-android` (Android) | Receiver, permission, alarm and Flow helpers. No Compose, no DI. |
 | Plumbing | `core-di` (JVM) | Dispatcher/scope qualifiers + their Hilt module. The only module that knows about DI. |
 | Design — identity | `identity` (Android) | Theme factory + motion. App supplies seed/palette. |
 | Design — components | `components` (Android) | Shared Compose primitives. App composes screens. |
@@ -95,7 +96,7 @@ Two kinds of module:
 - **JVM library** (`core-time`) — `org.jetbrains.kotlin.jvm`, `jvmTarget = 17`,
   JUnit 5 + Truth tests. The right home for pure logic; cheapest to build and
   test.
-- **Android library** (`core-crash`, `core-prefs`, `identity`, `components`) —
+- **Android library** (`core-crash`, `core-prefs`, `core-android`, `identity`, `components`) —
   `com.android.library` + the Compose plugin, `compileSdk 37` / `minSdk 29`.
 
 > **AGP 9.x provides built-in Kotlin compilation.** Android modules therefore
diff --git a/docs/ROADMAP.md b/docs/ROADMAP.md
index 0f57ac4..98b86ad 100644
--- a/docs/ROADMAP.md
+++ b/docs/ROADMAP.md
@@ -17,6 +17,7 @@ divergent or app-specific code where it lives.
 | `core-crash` | Android | Agendula |
 | `core-prefs` | Android | Clockula |
 | `core-di` | JVM | Clockula |
+| `core-android` | Android | — (Calendula pending) |
 | `identity` | Android | Agendula |
 | `components` | Android | Agendula |
 | `glance` | Android | Agendula (Calendula pending — its own M3 Expressive widget pass) |
diff --git a/identity/build.gradle.kts b/identity/build.gradle.kts
index a9fa649..26740f5 100644
--- a/identity/build.gradle.kts
+++ b/identity/build.gradle.kts
@@ -23,6 +23,13 @@ android {
     buildFeatures {
         compose = true
     }
+
+    testOptions {
+        unitTests {
+            all { it.useJUnitPlatform() }
+            isReturnDefaultValues = true
+        }
+    }
 }
 
 kotlin {
@@ -39,4 +46,9 @@ dependencies {
     implementation(libs.androidx.animation)
     // activity-compose for PredictiveBackHandler + BackEventCompat (the back-gesture peek).
     implementation(libs.androidx.activity.compose)
+
+    testImplementation(libs.junit.jupiter.api)
+    testRuntimeOnly(libs.junit.jupiter.engine)
+    testRuntimeOnly(libs.junit.platform.launcher)
+    testImplementation(libs.truth)
 }
diff --git a/identity/src/main/kotlin/de/jeanlucmakiola/floret/identity/PureBlack.kt b/identity/src/main/kotlin/de/jeanlucmakiola/floret/identity/PureBlack.kt
new file mode 100644
index 0000000..a99aa1b
--- /dev/null
+++ b/identity/src/main/kotlin/de/jeanlucmakiola/floret/identity/PureBlack.kt
@@ -0,0 +1,43 @@
+package de.jeanlucmakiola.floret.identity
+
+import androidx.compose.material3.ColorScheme
+import androidx.compose.ui.graphics.Color
+
+/**
+ * The pure-black (AMOLED) take on a dark [ColorScheme]: the ground — `background`,
+ * `surface`, `surfaceDim`, `surfaceContainerLowest` — goes to #000, and the
+ * container ladder is pulled down towards black rather than flattened onto it.
+ * Apps draw grids as container tiles over a `surface` ground, so the tiles keep
+ * a small lift and the gaps between them still read as lines; sheets and menus
+ * on the upper containers still separate from the page.
+ *
+ * Each container keeps a fixed share of its own sRGB channels, so the scheme's
+ * hue tint — a dynamic wallpaper colour or an app's seed — carries
+ * over. Accent, outline and `on*` roles are untouched. Meant for a dark scheme
+ * only; on a light one it would just darken the surfaces.
+ */
+fun ColorScheme.toPureBlack(): ColorScheme = copy(
+    background = Color.Black,
+    surface = Color.Black,
+    surfaceDim = Color.Black,
+    surfaceContainerLowest = Color.Black,
+    surfaceContainerLow = surfaceContainerLow.dimmed(PURE_BLACK_LOW),
+    surfaceContainer = surfaceContainer.dimmed(PURE_BLACK_CONTAINER),
+    surfaceContainerHigh = surfaceContainerHigh.dimmed(PURE_BLACK_HIGH),
+    surfaceContainerHighest = surfaceContainerHighest.dimmed(PURE_BLACK_HIGHEST),
+)
+
+/**
+ * This colour with each sRGB channel scaled by [share], keeping its hue. Plain
+ * channel scaling rather than `lerp`, which blends in Oklab and lands darker.
+ */
+private fun Color.dimmed(share: Float): Color =
+    Color(red = red * share, green = green * share, blue = blue * share, alpha = alpha)
+
+// Shares of each container's own sRGB channels kept in pure black. Against the
+// stock dark tones (#1D1B20 / #211F26 / #2B2930 / #36343B) they land near
+// #131215 / #1A191E / #252329 / #302F35.
+private const val PURE_BLACK_LOW = 0.65f
+private const val PURE_BLACK_CONTAINER = 0.80f
+private const val PURE_BLACK_HIGH = 0.85f
+private const val PURE_BLACK_HIGHEST = 0.90f
diff --git a/identity/src/main/kotlin/de/jeanlucmakiola/floret/identity/Theme.kt b/identity/src/main/kotlin/de/jeanlucmakiola/floret/identity/Theme.kt
index bce727d..6574513 100644
--- a/identity/src/main/kotlin/de/jeanlucmakiola/floret/identity/Theme.kt
+++ b/identity/src/main/kotlin/de/jeanlucmakiola/floret/identity/Theme.kt
@@ -34,6 +34,9 @@ val LocalFloretDarkTheme = staticCompositionLocalOf { false }
  * passing its own hand-tuned, seed-derived [lightScheme] / [darkScheme] and an
  * optional [typography]. A thin per-app wrapper (e.g. `AgendulaTheme`) supplies
  * those and forwards [darkTheme] / [dynamicColor] from settings.
+ *
+ * [pureBlack] swaps the dark scheme — dynamic or app-supplied — for its
+ * [toPureBlack] take, the AMOLED option. It has no effect on a light theme.
  */
 @OptIn(ExperimentalMaterial3ExpressiveApi::class)
 @Composable
@@ -42,6 +45,7 @@ fun FloretExpressiveTheme(
     darkScheme: ColorScheme,
     darkTheme: Boolean = isSystemInDarkTheme(),
     dynamicColor: Boolean = true,
+    pureBlack: Boolean = false,
     typography: Typography = Typography(),
     content: @Composable () -> Unit,
 ) {
@@ -52,7 +56,7 @@ fun FloretExpressiveTheme(
         }
         darkTheme -> darkScheme
         else -> lightScheme
-    }
+    }.let { if (darkTheme && pureBlack) it.toPureBlack() else it }
 
     CompositionLocalProvider(LocalFloretDarkTheme provides darkTheme) {
         MaterialExpressiveTheme(
diff --git a/identity/src/test/kotlin/de/jeanlucmakiola/floret/identity/PureBlackTest.kt b/identity/src/test/kotlin/de/jeanlucmakiola/floret/identity/PureBlackTest.kt
new file mode 100644
index 0000000..de62607
--- /dev/null
+++ b/identity/src/test/kotlin/de/jeanlucmakiola/floret/identity/PureBlackTest.kt
@@ -0,0 +1,66 @@
+package de.jeanlucmakiola.floret.identity
+
+import androidx.compose.material3.darkColorScheme
+import androidx.compose.ui.graphics.Color
+import com.google.common.truth.Truth.assertThat
+import org.junit.jupiter.api.Test
+
+/** The pure-black take on a dark scheme: a black ground, a dimmed container ladder. */
+class PureBlackTest {
+
+    private val dark = darkColorScheme()
+
+    @Test
+    fun `toPureBlack sets the ground roles to black`() {
+        val black = dark.toPureBlack()
+
+        val ground = listOf(black.background, black.surface, black.surfaceDim, black.surfaceContainerLowest)
+
+        assertThat(ground).containsExactly(Color.Black, Color.Black, Color.Black, Color.Black)
+    }
+
+    @Test
+    fun `toPureBlack keeps the containers above black and in order`() {
+        val black = dark.toPureBlack()
+
+        val ladder = listOf(
+            black.surfaceContainerLow,
+            black.surfaceContainer,
+            black.surfaceContainerHigh,
+            black.surfaceContainerHighest,
+        ).map { it.red + it.green + it.blue }
+
+        assertThat(ladder.first()).isGreaterThan(0f)
+        assertThat(ladder).isInStrictOrder()
+    }
+
+    @Test
+    fun `toPureBlack dims each container below its stock tone`() {
+        val black = dark.toPureBlack()
+
+        val dimmed = listOf(
+            black.surfaceContainer.red < dark.surfaceContainer.red,
+            black.surfaceContainerHighest.red < dark.surfaceContainerHighest.red,
+        )
+
+        assertThat(dimmed).containsExactly(true, true)
+    }
+
+    @Test
+    fun `toPureBlack scales a container's channels linearly`() {
+        val black = dark.toPureBlack()
+
+        val ratio = black.surfaceContainer.red / dark.surfaceContainer.red
+
+        assertThat(ratio).isWithin(0.02f).of(0.80f)
+    }
+
+    @Test
+    fun `toPureBlack leaves accent and content roles alone`() {
+        val black = dark.toPureBlack()
+
+        val kept = listOf(black.primary, black.onSurface, black.outline)
+
+        assertThat(kept).containsExactly(dark.primary, dark.onSurface, dark.outline).inOrder()
+    }
+}
diff --git a/settings.gradle.kts b/settings.gradle.kts
index ba063be..fef090c 100644
--- a/settings.gradle.kts
+++ b/settings.gradle.kts
@@ -37,6 +37,7 @@ include(":core-locale")
 include(":core-crash")
 include(":core-prefs")
 include(":core-di")
+include(":core-android")
 include(":identity")
 include(":components")
 include(":glance")