feat(reminders): reminder notifications — EVENT_REMINDER receiver, onboarding step, settings toggle (v1.4)

Calendula now posts event reminders itself (the Etar model): the provider
schedules the alarms and broadcasts EVENT_REMINDER, but a calendar app must
turn them into visible notifications — essential for users whose only
calendar app this is. A manifest-registered, exported receiver (data scheme
content://com.android.calendar) wakes us at reminder time; no foreground
service, no own alarm scheduling.

Delivery path (data/reminders/): EventReminderReceiver (Hilt, goAsync) →
ReminderAlertStore queries CalendarAlerts for STATE_SCHEDULED rows with
ALARM_TIME <= now → ReminderNotifier posts one notification per alert on a
dedicated high-importance channel, then best-effort marks rows FIRED
(needs WRITE_CALENDAR; without it a re-broadcast silently replaces — tag
per alert + setOnlyAlertOnce). Swiped notifications never return: FIRED
rows are never re-queried, so no dismiss-intent machinery. Research
(AOSP CalendarAlarmManager): the provider creates alert rows only for
METHOD_ALERT reminders, so the email-reminder filter happens upstream.

Tapping opens the event's detail screen: MainActivity is singleTop now,
parses eventId/begin/end extras (onCreate + onNewIntent) into Compose
state, and CalendarHost consumes the key exactly like an event tap.

Onboarding gained a one-time second step after the calendar grant (shared
OnboardingScaffold extracted from PermissionScreen): explains delivery,
warns that a second calendar app with notifications on duplicates
reminders, requests POST_NOTIFICATIONS (dialog on API 33+ only; minSdk 29).
"Not now" turns the feature off; reminders default ON. Settings mirrors
the toggle in a new Notifications section with the duplicate hint, and
re-requests the permission when enabling. Strings DE+EN.

Deliberately deferred (roadmap): snooze/dismiss actions, BOOT_COMPLETED /
exact-alarm scheduling, battery-exemption prompts.

Tests: reminderTimeText (all-day UTC-midnight reading, exclusive end day,
midnight-crossing ranges), reminders/onboarding pref round-trips.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/src/main/AndroidManifest.xml

@@ -4,6 +4,7 @@
 
     <uses-permission android:name="android.permission.READ_CALENDAR" />
     <uses-permission android:name="android.permission.WRITE_CALENDAR" />
+    <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
 
     <application
         android:name=".CalendulaApp"
@@ -19,6 +20,7 @@
         <activity
             android:name=".MainActivity"
             android:exported="true"
+            android:launchMode="singleTop"
             android:windowSoftInputMode="adjustResize">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />
@@ -26,6 +28,20 @@
             </intent-filter>
         </activity>
 
+        <!-- The provider broadcasts EVENT_REMINDER at reminder time but posts
+             no notification itself — a calendar app must (v1.4, Etar model).
+             Exported: the broadcast arrives from the provider's process. -->
+        <receiver
+            android:name=".data.reminders.EventReminderReceiver"
+            android:exported="true">
+            <intent-filter>
+                <action android:name="android.intent.action.EVENT_REMINDER" />
+                <data
+                    android:host="com.android.calendar"
+                    android:scheme="content" />
+            </intent-filter>
+        </receiver>
+
         <!-- Persists the per-app language (M4) on API < 33, where the platform
              per-app-languages API is unavailable. On 33+ this is a no-op. -->
         <service

app/src/main/java/de/jeanlucmakiola/calendula/MainActivity.kt

@@ -1,5 +1,7 @@
 package de.jeanlucmakiola.calendula
 
+import android.content.Context
+import android.content.Intent
 import android.os.Bundle
 import androidx.activity.ComponentActivity
 import androidx.activity.compose.setContent
@@ -7,7 +9,10 @@ import androidx.activity.enableEdgeToEdge
 import androidx.compose.foundation.isSystemInDarkTheme
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.setValue
 import androidx.compose.ui.Modifier
+import androidx.core.net.toUri
 import androidx.hilt.navigation.compose.hiltViewModel
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import dagger.hilt.android.AndroidEntryPoint
@@ -18,9 +23,16 @@ import de.jeanlucmakiola.calendula.ui.theme.CalendulaTheme
 
 @AndroidEntryPoint
 class MainActivity : ComponentActivity() {
+
+    // The occurrence a reminder notification was tapped for (eventId, begin,
+    // end — the detail screen's key shape). singleTop + onNewIntent route a
+    // tap into the running activity; CalendarHost consumes and clears it.
+    private var requestedDetailKey by mutableStateOf<LongArray?>(null)
+
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         enableEdgeToEdge()
+        requestedDetailKey = intent.detailKeyOrNull()
         setContent {
             // One activity-scoped SettingsViewModel drives both the theme here
             // and the Settings screen, so a theme change applies app-wide at once.
@@ -35,8 +47,51 @@ class MainActivity : ComponentActivity() {
                 darkTheme = darkTheme,
                 dynamicColor = settings.dynamicColor,
             ) {
-                RootScreen(modifier = Modifier.fillMaxSize())
+                RootScreen(
+                    modifier = Modifier.fillMaxSize(),
+                    requestedDetailKey = requestedDetailKey,
+                    onDetailKeyConsumed = { requestedDetailKey = null },
+                )
             }
         }
     }
+
+    override fun onNewIntent(intent: Intent) {
+        super.onNewIntent(intent)
+        intent.detailKeyOrNull()?.let { requestedDetailKey = it }
+    }
+
+    private fun Intent.detailKeyOrNull(): LongArray? {
+        val eventId = getLongExtra(EXTRA_EVENT_ID, -1L)
+        if (eventId == -1L) return null
+        return longArrayOf(
+            eventId,
+            getLongExtra(EXTRA_BEGIN_MILLIS, 0L),
+            getLongExtra(EXTRA_END_MILLIS, 0L),
+        )
+    }
+
+    companion object {
+        private const val EXTRA_EVENT_ID = "de.jeanlucmakiola.calendula.extra.EVENT_ID"
+        private const val EXTRA_BEGIN_MILLIS = "de.jeanlucmakiola.calendula.extra.BEGIN"
+        private const val EXTRA_END_MILLIS = "de.jeanlucmakiola.calendula.extra.END"
+
+        /**
+         * Intent opening the detail screen of one occurrence (reminder
+         * notifications). The synthetic data URI keys the intent so
+         * PendingIntents for different occurrences never collapse into one.
+         */
+        fun eventDetailIntent(
+            context: Context,
+            eventId: Long,
+            beginMillis: Long,
+            endMillis: Long,
+        ): Intent = Intent(context, MainActivity::class.java).apply {
+            data = "calendula://event/$eventId/$beginMillis".toUri()
+            putExtra(EXTRA_EVENT_ID, eventId)
+            putExtra(EXTRA_BEGIN_MILLIS, beginMillis)
+            putExtra(EXTRA_END_MILLIS, endMillis)
+            addFlags(Intent.FLAG_ACTIVITY_NEW_TASK)
+        }
+    }
 }

app/src/main/java/de/jeanlucmakiola/calendula/data/di/DataModule.kt

@@ -14,6 +14,8 @@ import de.jeanlucmakiola.calendula.data.calendar.AndroidCalendarDataSource
 import de.jeanlucmakiola.calendula.data.calendar.CalendarDataSource
 import de.jeanlucmakiola.calendula.data.calendar.CalendarRepository
 import de.jeanlucmakiola.calendula.data.calendar.CalendarRepositoryImpl
+import de.jeanlucmakiola.calendula.data.reminders.AndroidReminderAlertStore
+import de.jeanlucmakiola.calendula.data.reminders.ReminderAlertStore
 import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.Dispatchers
 import javax.inject.Singleton
@@ -37,6 +39,12 @@ abstract class DataBindModule {
     abstract fun bindCalendarRepository(
         impl: CalendarRepositoryImpl,
     ): CalendarRepository
+
+    @Binds
+    @Singleton
+    abstract fun bindReminderAlertStore(
+        impl: AndroidReminderAlertStore,
+    ): ReminderAlertStore
 }
 
 @Module

app/src/main/java/de/jeanlucmakiola/calendula/data/prefs/SettingsPrefs.kt

@@ -86,6 +86,31 @@ class SettingsPrefs @Inject constructor(
         }
     }
 
+    /**
+     * Whether Calendula posts reminder notifications (v1.4). Defaults to ON —
+     * for users whose only calendar app this is, reminders are essential; the
+     * onboarding step and Settings warn about duplicates from a second app.
+     */
+    val remindersEnabled: Flow<Boolean> = store.data.map { prefs ->
+        prefs[REMINDERS_ENABLED_KEY] ?: true
+    }
+
+    suspend fun setRemindersEnabled(enabled: Boolean) {
+        store.edit { it[REMINDERS_ENABLED_KEY] = enabled }
+    }
+
+    /**
+     * Whether the one-time reminder onboarding step (after the calendar
+     * grant) has been shown — also true for users who tapped "not now".
+     */
+    val reminderOnboardingDone: Flow<Boolean> = store.data.map { prefs ->
+        prefs[REMINDER_ONBOARDING_KEY] ?: false
+    }
+
+    suspend fun setReminderOnboardingDone() {
+        store.edit { it[REMINDER_ONBOARDING_KEY] = true }
+    }
+
     private fun parseFormFields(stored: String?): Set<EventFormField> = when (stored) {
         null -> DEFAULT_FORM_FIELDS
         else -> stored.split(',')
@@ -98,6 +123,8 @@ class SettingsPrefs @Inject constructor(
         internal val DYNAMIC_COLOR_KEY = booleanPreferencesKey("dynamic_color")
         internal val WEEK_START_KEY = stringPreferencesKey("week_start")
         internal val FORM_FIELDS_KEY = stringPreferencesKey("event_form_default_fields")
+        internal val REMINDERS_ENABLED_KEY = booleanPreferencesKey("reminders_enabled")
+        internal val REMINDER_ONBOARDING_KEY = booleanPreferencesKey("reminder_onboarding_done")
         internal val DEFAULT_FORM_FIELDS =
             setOf(EventFormField.Location, EventFormField.Description)
     }

app/src/main/java/de/jeanlucmakiola/calendula/data/reminders/EventReminderReceiver.kt

@@ -0,0 +1,57 @@
+package de.jeanlucmakiola.calendula.data.reminders
+
+import android.Manifest
+import android.content.BroadcastReceiver
+import android.content.Context
+import android.content.Intent
+import android.content.pm.PackageManager
+import android.provider.CalendarContract
+import androidx.core.content.ContextCompat
+import dagger.hilt.android.AndroidEntryPoint
+import de.jeanlucmakiola.calendula.data.prefs.SettingsPrefs
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.SupervisorJob
+import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.launch
+import javax.inject.Inject
+
+/**
+ * Becomes the app that turns the calendar provider's reminder alarms into
+ * visible notifications (the Etar model — the provider broadcasts
+ * `EVENT_REMINDER` at reminder time but posts nothing itself).
+ *
+ * The broadcast's data URI only carries the alarm time, so it is ignored:
+ * we query every still-scheduled, due `CalendarAlerts` row ourselves, post
+ * them, and mark them fired. Posting happens before marking — a crash in
+ * between re-posts silently (same tag) rather than losing the reminder.
+ */
+@AndroidEntryPoint
+class EventReminderReceiver : BroadcastReceiver() {
+
+    @Inject lateinit var alertStore: ReminderAlertStore
+    @Inject lateinit var notifier: ReminderNotifier
+    @Inject lateinit var settingsPrefs: SettingsPrefs
+
+    override fun onReceive(context: Context, intent: Intent) {
+        if (intent.action != CalendarContract.ACTION_EVENT_REMINDER) return
+        val readGranted = ContextCompat.checkSelfPermission(
+            context, Manifest.permission.READ_CALENDAR,
+        ) == PackageManager.PERMISSION_GRANTED
+        if (!readGranted || !notifier.canPost()) return
+
+        val pendingResult = goAsync()
+        CoroutineScope(SupervisorJob() + Dispatchers.IO).launch {
+            try {
+                if (settingsPrefs.remindersEnabled.first()) {
+                    val now = System.currentTimeMillis()
+                    val due = alertStore.dueAlerts(now)
+                    due.forEach(notifier::post)
+                    alertStore.markFired(due.map { it.alertId }, now)
+                }
+            } finally {
+                pendingResult.finish()
+            }
+        }
+    }
+}

app/src/main/java/de/jeanlucmakiola/calendula/data/reminders/ReminderAlertStore.kt

@@ -0,0 +1,112 @@
+package de.jeanlucmakiola.calendula.data.reminders
+
+import android.content.ContentValues
+import android.content.Context
+import android.provider.CalendarContract
+import android.util.Log
+import dagger.hilt.android.qualifiers.ApplicationContext
+import javax.inject.Inject
+import javax.inject.Singleton
+
+/**
+ * One due row of the provider's `CalendarAlerts` table (a join with Events).
+ * Stays in the data layer: alerts feed the notification path only and never
+ * reach a screen, so there is no domain model for them.
+ */
+data class ReminderAlert(
+    val alertId: Long,
+    val eventId: Long,
+    val beginMillis: Long,
+    val endMillis: Long,
+    /** Raw event title; may be blank — the notifier substitutes "(no title)". */
+    val title: String,
+    val location: String?,
+    val isAllDay: Boolean,
+)
+
+/**
+ * Seam over the `CalendarAlerts` table so the receiver logic can be exercised
+ * without a ContentResolver. The provider creates these rows itself — only
+ * for `METHOD_ALERT` reminders (verified in AOSP `CalendarAlarmManager`), so
+ * email reminders never show up here.
+ */
+interface ReminderAlertStore {
+
+    /** Alerts that are due (`ALARM_TIME` has passed) and still unhandled. */
+    fun dueAlerts(nowMillis: Long): List<ReminderAlert>
+
+    /**
+     * Mark the given alerts handled (`STATE_FIRED`) so a later broadcast does
+     * not surface them again. Best effort: this write needs `WRITE_CALENDAR`,
+     * which the user may have declined — then re-broadcasts silently replace
+     * the already-posted notifications instead (same tag, alert-once).
+     */
+    fun markFired(alertIds: List<Long>, nowMillis: Long)
+}
+
+@Singleton
+class AndroidReminderAlertStore @Inject constructor(
+    @ApplicationContext private val context: Context,
+) : ReminderAlertStore {
+
+    override fun dueAlerts(nowMillis: Long): List<ReminderAlert> = context.contentResolver.query(
+        CalendarContract.CalendarAlerts.CONTENT_URI,
+        PROJECTION,
+        CalendarContract.CalendarAlerts.STATE + " = ? AND " +
+            CalendarContract.CalendarAlerts.ALARM_TIME + " <= ?",
+        arrayOf(
+            CalendarContract.CalendarAlerts.STATE_SCHEDULED.toString(),
+            nowMillis.toString(),
+        ),
+        CalendarContract.CalendarAlerts.BEGIN + " ASC",
+    )?.use { c ->
+        buildList {
+            while (c.moveToNext()) {
+                add(
+                    ReminderAlert(
+                        alertId = c.getLong(0),
+                        eventId = c.getLong(1),
+                        beginMillis = c.getLong(2),
+                        endMillis = c.getLong(3),
+                        title = c.getString(4).orEmpty(),
+                        location = c.getString(5)?.takeIf { it.isNotBlank() },
+                        isAllDay = c.getInt(6) == 1,
+                    ),
+                )
+            }
+        }
+    } ?: emptyList()
+
+    override fun markFired(alertIds: List<Long>, nowMillis: Long) {
+        if (alertIds.isEmpty()) return
+        val values = ContentValues().apply {
+            put(CalendarContract.CalendarAlerts.STATE, CalendarContract.CalendarAlerts.STATE_FIRED)
+            put(CalendarContract.CalendarAlerts.RECEIVED_TIME, nowMillis)
+            put(CalendarContract.CalendarAlerts.NOTIFY_TIME, nowMillis)
+        }
+        try {
+            context.contentResolver.update(
+                CalendarContract.CalendarAlerts.CONTENT_URI,
+                values,
+                CalendarContract.CalendarAlerts._ID +
+                    " IN (" + alertIds.joinToString(",") + ")",
+                null,
+            )
+        } catch (e: SecurityException) {
+            Log.w(TAG, "Cannot mark alerts fired without WRITE_CALENDAR", e)
+        }
+    }
+
+    private companion object {
+        const val TAG = "ReminderAlertStore"
+        val PROJECTION = arrayOf(
+            CalendarContract.CalendarAlerts._ID,
+            CalendarContract.CalendarAlerts.EVENT_ID,
+            CalendarContract.CalendarAlerts.BEGIN,
+            CalendarContract.CalendarAlerts.END,
+            CalendarContract.CalendarAlerts.TITLE,
+            CalendarContract.CalendarAlerts.EVENT_LOCATION,
+            CalendarContract.CalendarAlerts.ALL_DAY,
+        )
+    }
+}

app/src/main/java/de/jeanlucmakiola/calendula/data/reminders/ReminderNotifier.kt

@@ -0,0 +1,101 @@
+package de.jeanlucmakiola.calendula.data.reminders
+
+import android.Manifest
+import android.app.NotificationChannel
+import android.app.NotificationManager
+import android.app.PendingIntent
+import android.content.Context
+import android.content.pm.PackageManager
+import android.os.Build
+import android.util.Log
+import androidx.core.app.NotificationCompat
+import androidx.core.app.NotificationManagerCompat
+import androidx.core.content.ContextCompat
+import dagger.hilt.android.qualifiers.ApplicationContext
+import de.jeanlucmakiola.calendula.MainActivity
+import de.jeanlucmakiola.calendula.R
+import java.time.ZoneId
+import java.util.Locale
+import javax.inject.Inject
+import javax.inject.Singleton
+
+/**
+ * Posts one notification per due reminder alert on a dedicated channel.
+ * Tapping opens the event's detail screen; the tag is the alert id, so a
+ * re-broadcast of an alert we couldn't mark fired replaces its notification
+ * silently ([NotificationCompat.Builder.setOnlyAlertOnce]) instead of
+ * duplicating it.
+ */
+@Singleton
+class ReminderNotifier @Inject constructor(
+    @ApplicationContext private val context: Context,
+) {
+
+    /** False when the user declined `POST_NOTIFICATIONS` or muted the app. */
+    fun canPost(): Boolean {
+        val granted = Build.VERSION.SDK_INT < Build.VERSION_CODES.TIRAMISU ||
+            ContextCompat.checkSelfPermission(context, Manifest.permission.POST_NOTIFICATIONS) ==
+            PackageManager.PERMISSION_GRANTED
+        return granted && NotificationManagerCompat.from(context).areNotificationsEnabled()
+    }
+
+    fun post(alert: ReminderAlert) {
+        ensureChannel()
+        val title = alert.title.ifBlank { context.getString(R.string.event_untitled) }
+        val time = reminderTimeText(
+            beginMillis = alert.beginMillis,
+            endMillis = alert.endMillis,
+            isAllDay = alert.isAllDay,
+            zone = ZoneId.systemDefault(),
+            locale = Locale.getDefault(),
+        )
+        val text = listOfNotNull(time, alert.location).joinToString(" · ")
+        val notification = NotificationCompat.Builder(context, CHANNEL_ID)
+            .setSmallIcon(R.drawable.ic_notification)
+            .setContentTitle(title)
+            .setContentText(text)
+            .setWhen(alert.beginMillis)
+            .setShowWhen(false)
+            .setCategory(NotificationCompat.CATEGORY_EVENT)
+            .setPriority(NotificationCompat.PRIORITY_HIGH)
+            .setAutoCancel(true)
+            .setOnlyAlertOnce(true)
+            .setContentIntent(detailIntent(alert))
+            .build()
+        try {
+            NotificationManagerCompat.from(context)
+                .notify(alert.alertId.toString(), NOTIFICATION_ID, notification)
+        } catch (e: SecurityException) {
+            // POST_NOTIFICATIONS was revoked between canPost() and here.
+            Log.w(TAG, "Could not post reminder for event ${alert.eventId}", e)
+        }
+    }
+
+    private fun detailIntent(alert: ReminderAlert): PendingIntent = PendingIntent.getActivity(
+        context,
+        /* requestCode = */ alert.alertId.toInt(),
+        MainActivity.eventDetailIntent(context, alert.eventId, alert.beginMillis, alert.endMillis),
+        PendingIntent.FLAG_UPDATE_CURRENT or PendingIntent.FLAG_IMMUTABLE,
+    )
+
+    /** Channel creation is idempotent; re-running refreshes the localized name. */
+    private fun ensureChannel() {
+        val channel = NotificationChannel(
+            CHANNEL_ID,
+            context.getString(R.string.reminder_channel_name),
+            NotificationManager.IMPORTANCE_HIGH,
+        ).apply {
+            description = context.getString(R.string.reminder_channel_description)
+        }
+        NotificationManagerCompat.from(context).createNotificationChannel(channel)
+    }
+
+    private companion object {
+        const val TAG = "ReminderNotifier"
+        const val CHANNEL_ID = "reminders"
+
+        // One id, distinct tags: the tag (alert id) already keys the
+        // notification, so a fixed id keeps cancellation/replacement simple.
+        const val NOTIFICATION_ID = 1
+    }
+}

app/src/main/java/de/jeanlucmakiola/calendula/data/reminders/ReminderTimeText.kt

@@ -0,0 +1,56 @@
+package de.jeanlucmakiola.calendula.data.reminders
+
+import java.time.Instant
+import java.time.ZoneId
+import java.time.ZoneOffset
+import java.time.format.DateTimeFormatter
+import java.time.format.FormatStyle
+import java.util.Locale
+
+/**
+ * The one line of time context in a reminder notification. Pure so it can be
+ * JVM-tested:
+ *
+ * - timed, same day:      "09:30 – 10:00"
+ * - timed, crossing days: "11 Jun, 23:30 – 12 Jun, 00:30" (medium date + short time)
+ * - all-day, one day:     "11 Jun 2026"
+ * - all-day, multi-day:   "11 Jun 2026 – 12 Jun 2026"
+ *
+ * All-day instances store UTC midnights with an exclusive end, so they are
+ * read in UTC and the end day is the last *covered* day.
+ */
+fun reminderTimeText(
+    beginMillis: Long,
+    endMillis: Long,
+    isAllDay: Boolean,
+    zone: ZoneId,
+    locale: Locale,
+): String {
+    if (isAllDay) {
+        val dateFormat = DateTimeFormatter.ofLocalizedDate(FormatStyle.MEDIUM).withLocale(locale)
+        // (atZone().toLocalDate() instead of LocalDate.ofInstant — API 34+)
+        val firstDay = Instant.ofEpochMilli(beginMillis).atZone(ZoneOffset.UTC).toLocalDate()
+        val lastDay = Instant.ofEpochMilli(endMillis).atZone(ZoneOffset.UTC).toLocalDate()
+            .minusDays(1)
+            .coerceAtLeast(firstDay)
+        return if (lastDay == firstDay) {
+            dateFormat.format(firstDay)
+        } else {
+            dateFormat.format(firstDay) + RANGE + dateFormat.format(lastDay)
+        }
+    }
+
+    val timeFormat = DateTimeFormatter.ofLocalizedTime(FormatStyle.SHORT).withLocale(locale)
+    val begin = Instant.ofEpochMilli(beginMillis).atZone(zone)
+    val end = Instant.ofEpochMilli(endMillis).atZone(zone)
+    return if (begin.toLocalDate() == end.toLocalDate()) {
+        timeFormat.format(begin) + RANGE + timeFormat.format(end)
+    } else {
+        val dateTimeFormat = DateTimeFormatter
+            .ofLocalizedDateTime(FormatStyle.MEDIUM, FormatStyle.SHORT)
+            .withLocale(locale)
+        dateTimeFormat.format(begin) + RANGE + dateTimeFormat.format(end)
+    }
+}
+
+private const val RANGE = " – "

app/src/main/java/de/jeanlucmakiola/calendula/ui/CalendarHost.kt

@@ -8,6 +8,7 @@ import androidx.compose.animation.slideOutHorizontally
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
@@ -29,9 +30,18 @@ import kotlinx.datetime.LocalDate
  * Holds the active top-level view (spec M1) and swaps between the calendar
  * screens. Each screen owns its own ViewModel and date anchor; the view-switcher
  * pill in their top bars writes back here via [onSelectView].
+ *
+ * [requestedDetailKey] is an externally requested occurrence (a tapped
+ * reminder notification routed through MainActivity): it opens the detail
+ * overlay exactly like an event tap and is cleared via [onDetailKeyConsumed]
+ * so a later recomposition can't re-open it.
  */
 @Composable
-fun CalendarHost(modifier: Modifier = Modifier) {
+fun CalendarHost(
+    modifier: Modifier = Modifier,
+    requestedDetailKey: LongArray? = null,
+    onDetailKeyConsumed: () -> Unit = {},
+) {
     var view by rememberSaveable { mutableStateOf(CalendarView.Week) }
     val onSelectView: (CalendarView) -> Unit = { view = it }
 
@@ -61,6 +71,15 @@ fun CalendarHost(modifier: Modifier = Modifier) {
         detailKey = key
     }
 
+    // A tapped reminder notification asks for a specific occurrence.
+    LaunchedEffect(requestedDetailKey) {
+        if (requestedDetailKey != null) {
+            heldKey = requestedDetailKey
+            detailKey = requestedDetailKey
+            onDetailKeyConsumed()
+        }
+    }
+
     // Settings (M4) is hoisted here so it overlays whichever calendar view is
     // active and survives view switches. (The calendar filter now lives inline
     // in the navigation drawer, so no overlay state is needed for it.)

app/src/main/java/de/jeanlucmakiola/calendula/ui/RootScreen.kt

@@ -10,14 +10,22 @@ import androidx.compose.runtime.setValue
 import androidx.compose.runtime.getValue
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.platform.LocalContext
+import androidx.hilt.navigation.compose.hiltViewModel
 import androidx.lifecycle.compose.LocalLifecycleOwner
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import androidx.core.content.ContextCompat
 import androidx.lifecycle.Lifecycle
 import androidx.lifecycle.LifecycleEventObserver
 import de.jeanlucmakiola.calendula.ui.permission.PermissionScreen
+import de.jeanlucmakiola.calendula.ui.permission.ReminderOnboardingScreen
+import de.jeanlucmakiola.calendula.ui.permission.ReminderOnboardingViewModel
 
 @Composable
-fun RootScreen(modifier: Modifier = Modifier) {
+fun RootScreen(
+    modifier: Modifier = Modifier,
+    requestedDetailKey: LongArray? = null,
+    onDetailKeyConsumed: () -> Unit = {},
+) {
     val context = LocalContext.current
     var hasPermission by remember {
         mutableStateOf(
@@ -40,7 +48,23 @@ fun RootScreen(modifier: Modifier = Modifier) {
     }
 
     if (hasPermission) {
-        CalendarHost(modifier = modifier)
+        // Second onboarding gate (v1.4, one-time): reminder notifications.
+        // Null until DataStore's first emission — render nothing for that
+        // frame instead of flashing the wrong screen.
+        val reminderOnboarding: ReminderOnboardingViewModel = hiltViewModel()
+        val onboardingDone by reminderOnboarding.onboardingDone.collectAsStateWithLifecycle()
+        when (onboardingDone) {
+            true -> CalendarHost(
+                modifier = modifier,
+                requestedDetailKey = requestedDetailKey,
+                onDetailKeyConsumed = onDetailKeyConsumed,
+            )
+            false -> ReminderOnboardingScreen(
+                onFinished = reminderOnboarding::finish,
+                modifier = modifier,
+            )
+            null -> {}
+        }
     } else {
         PermissionScreen(
             onGranted = { hasPermission = true },

app/src/main/java/de/jeanlucmakiola/calendula/ui/permission/OnboardingScaffold.kt

@@ -0,0 +1,163 @@
+package de.jeanlucmakiola.calendula.ui.permission
+
+import androidx.compose.foundation.Image
+import androidx.compose.foundation.background
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+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.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.navigationBarsPadding
+import androidx.compose.foundation.layout.offset
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.layout.width
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.shape.CircleShape
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.foundation.verticalScroll
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.filled.Lock
+import androidx.compose.material3.Icon
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Scaffold
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.clip
+import androidx.compose.ui.graphics.vector.ImageVector
+import androidx.compose.ui.res.colorResource
+import androidx.compose.ui.res.painterResource
+import androidx.compose.ui.res.stringResource
+import androidx.compose.ui.unit.dp
+import de.jeanlucmakiola.calendula.R
+
+/** MD3 8dp spacing scale shared by the onboarding screens. */
+internal object OnboardingSpace {
+    val xs = 8.dp
+    val sm = 16.dp
+    val md = 24.dp
+    val lg = 32.dp
+    val xl = 48.dp
+}
+
+/**
+ * Shared onboarding shell (calendar grant, reminder step): a scrollable,
+ * centred hero + body with the call(s) to action pinned to the bottom (clear
+ * of the navigation bar). The content slot is centred horizontally; benefit
+ * rows fill the width so their own content left-aligns.
+ */
+@Composable
+internal fun OnboardingScaffold(
+    hero: @Composable () -> Unit,
+    actions: @Composable ColumnScope.() -> Unit,
+    modifier: Modifier = Modifier,
+    body: @Composable ColumnScope.() -> Unit,
+) {
+    Scaffold(
+        modifier = modifier,
+        containerColor = MaterialTheme.colorScheme.surface,
+        bottomBar = {
+            Column(
+                modifier = Modifier
+                    .fillMaxWidth()
+                    .navigationBarsPadding()
+                    .padding(horizontal = OnboardingSpace.md, vertical = OnboardingSpace.sm),
+                horizontalAlignment = Alignment.CenterHorizontally,
+                verticalArrangement = Arrangement.spacedBy(4.dp),
+                content = actions,
+            )
+        },
+    ) { innerPadding ->
+        Column(
+            modifier = Modifier
+                .fillMaxSize()
+                .padding(innerPadding)
+                .verticalScroll(rememberScrollState())
+                .padding(horizontal = OnboardingSpace.md),
+            horizontalAlignment = Alignment.CenterHorizontally,
+        ) {
+            Spacer(Modifier.height(OnboardingSpace.xl))
+            hero()
+            Spacer(Modifier.height(OnboardingSpace.lg))
+            body()
+            Spacer(Modifier.height(OnboardingSpace.md))
+        }
+    }
+}
+
+/** The app's adaptive launcher mark, reconstructed as a large branded squircle. */
+@Composable
+internal fun BrandHero(denied: Boolean) {
+    Box(contentAlignment = Alignment.Center) {
+        Box(
+            modifier = Modifier
+                .size(128.dp)
+                .clip(RoundedCornerShape(34.dp))
+                .background(colorResource(R.color.ic_launcher_background)),
+        ) {
+            Image(
+                painter = painterResource(R.drawable.ic_launcher_foreground),
+                contentDescription = stringResource(R.string.app_name),
+                modifier = Modifier.fillMaxSize(),
+            )
+        }
+        if (denied) {
+            // A small lock badge sits over the corner to signal "blocked".
+            Box(
+                modifier = Modifier
+                    .align(Alignment.BottomEnd)
+                    .offset(x = 10.dp, y = 10.dp)
+                    .size(44.dp)
+                    .clip(CircleShape)
+                    .background(MaterialTheme.colorScheme.errorContainer),
+                contentAlignment = Alignment.Center,
+            ) {
+                Icon(
+                    imageVector = Icons.Filled.Lock,
+                    contentDescription = null,
+                    tint = MaterialTheme.colorScheme.onErrorContainer,
+                    modifier = Modifier.size(24.dp),
+                )
+            }
+        }
+    }
+}
+
+/** One trust point: a tonal icon chip on the left, title + supporting text right. */
+@Composable
+internal fun BenefitRow(icon: ImageVector, title: String, body: String) {
+    Row(
+        modifier = Modifier.fillMaxWidth(),
+        verticalAlignment = Alignment.CenterVertically,
+    ) {
+        Box(
+            modifier = Modifier
+                .size(44.dp)
+                .clip(CircleShape)
+                .background(MaterialTheme.colorScheme.secondaryContainer),
+            contentAlignment = Alignment.Center,
+        ) {
+            Icon(
+                imageVector = icon,
+                contentDescription = null,
+                tint = MaterialTheme.colorScheme.onSecondaryContainer,
+                modifier = Modifier.size(22.dp),
+            )
+        }
+        Spacer(Modifier.width(OnboardingSpace.sm))
+        Column(modifier = Modifier.weight(1f)) {
+            Text(text = title, style = MaterialTheme.typography.titleMedium)
+            Text(
+                text = body,
+                style = MaterialTheme.typography.bodyMedium,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+            )
+        }
+    }
+}

app/src/main/java/de/jeanlucmakiola/calendula/ui/permission/PermissionScreen.kt

@@ -6,25 +6,14 @@ import android.net.Uri
 import android.provider.Settings
 import androidx.activity.compose.rememberLauncherForActivityResult
 import androidx.activity.result.contract.ActivityResultContracts
-import androidx.compose.foundation.background
 import androidx.compose.foundation.layout.Arrangement
-import androidx.compose.foundation.layout.Box
-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.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.height
-import androidx.compose.foundation.layout.navigationBarsPadding
-import androidx.compose.foundation.layout.offset
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.layout.width
-import androidx.compose.foundation.rememberScrollState
-import androidx.compose.foundation.shape.CircleShape
-import androidx.compose.foundation.shape.RoundedCornerShape
-import androidx.compose.foundation.verticalScroll
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.automirrored.filled.ArrowForward
 import androidx.compose.material.icons.filled.CalendarMonth
@@ -34,7 +23,6 @@ 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
 import androidx.compose.material3.Text
 import androidx.compose.material3.TextButton
 import androidx.compose.runtime.Composable
@@ -42,18 +30,13 @@ import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.getValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
-import androidx.compose.ui.draw.clip
-import androidx.compose.ui.graphics.vector.ImageVector
 import androidx.compose.ui.platform.LocalContext
-import androidx.compose.ui.res.colorResource
-import androidx.compose.ui.res.painterResource
 import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.unit.sp
 import androidx.hilt.navigation.compose.hiltViewModel
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
-import androidx.compose.foundation.Image
 import de.jeanlucmakiola.calendula.R
 
 private val CALENDAR_PERMISSIONS = arrayOf(
@@ -61,15 +44,6 @@ private val CALENDAR_PERMISSIONS = arrayOf(
     Manifest.permission.WRITE_CALENDAR,
 )
 
-// MD3 8dp spacing scale, scoped to this screen.
-private object Space {
-    val xs = 8.dp
-    val sm = 16.dp
-    val md = 24.dp
-    val lg = 32.dp
-    val xl = 48.dp
-}
-
 @Composable
 fun PermissionScreen(
     onGranted: () -> Unit,
@@ -118,7 +92,7 @@ private fun RationaleContent(
     onRequest: () -> Unit,
     modifier: Modifier = Modifier,
 ) {
-    PermissionScaffold(
+    OnboardingScaffold(
         modifier = modifier,
         hero = { BrandHero(denied = false) },
         actions = {
@@ -131,7 +105,7 @@ private fun RationaleContent(
                     text = stringResource(R.string.permission_request_button),
                     style = MaterialTheme.typography.titleMedium,
                 )
-                Spacer(Modifier.width(Space.xs))
+                Spacer(Modifier.width(OnboardingSpace.xs))
                 Icon(
                     imageVector = Icons.AutoMirrored.Filled.ArrowForward,
                     contentDescription = null,
@@ -147,7 +121,7 @@ private fun RationaleContent(
             color = MaterialTheme.colorScheme.primary,
             letterSpacing = 2.sp,
         )
-        Spacer(Modifier.height(Space.xs))
+        Spacer(Modifier.height(OnboardingSpace.xs))
         Text(
             text = stringResource(R.string.permission_rationale_title),
             style = MaterialTheme.typography.headlineMedium,
@@ -161,20 +135,20 @@ private fun RationaleContent(
             textAlign = TextAlign.Center,
         )
 
-        Spacer(Modifier.height(Space.xl))
+        Spacer(Modifier.height(OnboardingSpace.xl))
 
         BenefitRow(
             icon = Icons.Filled.Lock,
             title = stringResource(R.string.permission_benefit_private_title),
             body = stringResource(R.string.permission_benefit_private_body),
         )
-        Spacer(Modifier.height(Space.sm))
+        Spacer(Modifier.height(OnboardingSpace.sm))
         BenefitRow(
             icon = Icons.Filled.CalendarMonth,
             title = stringResource(R.string.permission_benefit_sync_title),
             body = stringResource(R.string.permission_benefit_sync_body),
         )
-        Spacer(Modifier.height(Space.sm))
+        Spacer(Modifier.height(OnboardingSpace.sm))
         BenefitRow(
             icon = Icons.Filled.VisibilityOff,
             title = stringResource(R.string.permission_benefit_privacy_title),
@@ -189,7 +163,7 @@ private fun DeniedContent(
     modifier: Modifier = Modifier,
 ) {
     val context = LocalContext.current
-    PermissionScaffold(
+    OnboardingScaffold(
         modifier = modifier,
         hero = { BrandHero(denied = true) },
         actions = {
@@ -231,122 +205,6 @@ private fun DeniedContent(
     }
 }
 
-/**
- * Shared onboarding shell: a scrollable, centred hero + body with the call(s) to
- * action pinned to the bottom (clear of the navigation bar). The content slot is
- * centred horizontally; benefit rows fill the width so their own content
- * left-aligns.
- */
-@Composable
-private fun PermissionScaffold(
-    hero: @Composable () -> Unit,
-    actions: @Composable ColumnScope.() -> Unit,
-    modifier: Modifier = Modifier,
-    body: @Composable ColumnScope.() -> Unit,
-) {
-    Scaffold(
-        modifier = modifier,
-        containerColor = MaterialTheme.colorScheme.surface,
-        bottomBar = {
-            Column(
-                modifier = Modifier
-                    .fillMaxWidth()
-                    .navigationBarsPadding()
-                    .padding(horizontal = Space.md, vertical = Space.sm),
-                horizontalAlignment = Alignment.CenterHorizontally,
-                verticalArrangement = Arrangement.spacedBy(4.dp),
-                content = actions,
-            )
-        },
-    ) { innerPadding ->
-        Column(
-            modifier = Modifier
-                .fillMaxSize()
-                .padding(innerPadding)
-                .verticalScroll(rememberScrollState())
-                .padding(horizontal = Space.md),
-            horizontalAlignment = Alignment.CenterHorizontally,
-        ) {
-            Spacer(Modifier.height(Space.xl))
-            hero()
-            Spacer(Modifier.height(Space.lg))
-            body()
-            Spacer(Modifier.height(Space.md))
-        }
-    }
-}
-
-/** The app's adaptive launcher mark, reconstructed as a large branded squircle. */
-@Composable
-private fun BrandHero(denied: Boolean) {
-    Box(contentAlignment = Alignment.Center) {
-        Box(
-            modifier = Modifier
-                .size(128.dp)
-                .clip(RoundedCornerShape(34.dp))
-                .background(colorResource(R.color.ic_launcher_background)),
-        ) {
-            Image(
-                painter = painterResource(R.drawable.ic_launcher_foreground),
-                contentDescription = stringResource(R.string.app_name),
-                modifier = Modifier.fillMaxSize(),
-            )
-        }
-        if (denied) {
-            // A small lock badge sits over the corner to signal "blocked".
-            Box(
-                modifier = Modifier
-                    .align(Alignment.BottomEnd)
-                    .offset(x = 10.dp, y = 10.dp)
-                    .size(44.dp)
-                    .clip(CircleShape)
-                    .background(MaterialTheme.colorScheme.errorContainer),
-                contentAlignment = Alignment.Center,
-            ) {
-                Icon(
-                    imageVector = Icons.Filled.Lock,
-                    contentDescription = null,
-                    tint = MaterialTheme.colorScheme.onErrorContainer,
-                    modifier = Modifier.size(24.dp),
-                )
-            }
-        }
-    }
-}
-
-/** One trust point: a tonal icon chip on the left, title + supporting text right. */
-@Composable
-private fun BenefitRow(icon: ImageVector, title: String, body: String) {
-    Row(
-        modifier = Modifier.fillMaxWidth(),
-        verticalAlignment = Alignment.CenterVertically,
-    ) {
-        Box(
-            modifier = Modifier
-                .size(44.dp)
-                .clip(CircleShape)
-                .background(MaterialTheme.colorScheme.secondaryContainer),
-            contentAlignment = Alignment.Center,
-        ) {
-            Icon(
-                imageVector = icon,
-                contentDescription = null,
-                tint = MaterialTheme.colorScheme.onSecondaryContainer,
-                modifier = Modifier.size(22.dp),
-            )
-        }
-        Spacer(Modifier.width(Space.sm))
-        Column(modifier = Modifier.weight(1f)) {
-            Text(text = title, style = MaterialTheme.typography.titleMedium)
-            Text(
-                text = body,
-                style = MaterialTheme.typography.bodyMedium,
-                color = MaterialTheme.colorScheme.onSurfaceVariant,
-            )
-        }
-    }
-}
-
 @Composable
 private fun PrivacyFootnote() {
     Row(

app/src/main/java/de/jeanlucmakiola/calendula/ui/permission/ReminderOnboardingScreen.kt

@@ -0,0 +1,138 @@
+package de.jeanlucmakiola.calendula.ui.permission
+
+import android.Manifest
+import android.os.Build
+import androidx.activity.compose.rememberLauncherForActivityResult
+import androidx.activity.result.contract.ActivityResultContracts
+import androidx.compose.foundation.background
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.filled.NotificationsActive
+import androidx.compose.material.icons.filled.ContentCopy
+import androidx.compose.material.icons.filled.Tune
+import androidx.compose.material3.Button
+import androidx.compose.material3.Icon
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.clip
+import androidx.compose.ui.res.stringResource
+import androidx.compose.ui.text.style.TextAlign
+import androidx.compose.ui.unit.dp
+import androidx.compose.ui.unit.sp
+import de.jeanlucmakiola.calendula.R
+
+/**
+ * One-time onboarding step after the calendar grant (v1.4): explains that
+ * Calendula delivers reminder notifications itself, warns about duplicates
+ * when a second calendar app has notifications on, and requests
+ * `POST_NOTIFICATIONS` (a system dialog on API 33+ only; minSdk is 29).
+ *
+ * Reminders default ON: [onFinished] gets true from the primary action even
+ * if the system dialog is declined — the OS permission is the real gate, and
+ * the Settings toggle re-requests it. "Not now" turns the in-app toggle off.
+ */
+@Composable
+fun ReminderOnboardingScreen(
+    onFinished: (remindersEnabled: Boolean) -> Unit,
+    modifier: Modifier = Modifier,
+) {
+    val launcher = rememberLauncherForActivityResult(
+        contract = ActivityResultContracts.RequestPermission(),
+    ) { onFinished(true) }
+
+    OnboardingScaffold(
+        modifier = modifier,
+        hero = { BellHero() },
+        actions = {
+            Button(
+                onClick = {
+                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
+                        launcher.launch(Manifest.permission.POST_NOTIFICATIONS)
+                    } else {
+                        onFinished(true)
+                    }
+                },
+                modifier = Modifier.fillMaxWidth().height(56.dp),
+            ) {
+                Text(
+                    text = stringResource(R.string.reminder_onboarding_enable_button),
+                    style = MaterialTheme.typography.titleMedium,
+                )
+            }
+            TextButton(
+                onClick = { onFinished(false) },
+                modifier = Modifier.fillMaxWidth(),
+            ) {
+                Text(stringResource(R.string.reminder_onboarding_skip_button))
+            }
+        },
+    ) {
+        Text(
+            text = stringResource(R.string.app_name).uppercase(),
+            style = MaterialTheme.typography.labelLarge,
+            color = MaterialTheme.colorScheme.primary,
+            letterSpacing = 2.sp,
+        )
+        Spacer(Modifier.height(OnboardingSpace.xs))
+        Text(
+            text = stringResource(R.string.reminder_onboarding_title),
+            style = MaterialTheme.typography.headlineMedium,
+            textAlign = TextAlign.Center,
+        )
+        Spacer(Modifier.height(12.dp))
+        Text(
+            text = stringResource(R.string.reminder_onboarding_body),
+            style = MaterialTheme.typography.bodyLarge,
+            color = MaterialTheme.colorScheme.onSurfaceVariant,
+            textAlign = TextAlign.Center,
+        )
+
+        Spacer(Modifier.height(OnboardingSpace.xl))
+
+        BenefitRow(
+            icon = Icons.Filled.NotificationsActive,
+            title = stringResource(R.string.reminder_benefit_delivery_title),
+            body = stringResource(R.string.reminder_benefit_delivery_body),
+        )
+        Spacer(Modifier.height(OnboardingSpace.sm))
+        BenefitRow(
+            icon = Icons.Filled.ContentCopy,
+            title = stringResource(R.string.reminder_benefit_duplicates_title),
+            body = stringResource(R.string.reminder_benefit_duplicates_body),
+        )
+        Spacer(Modifier.height(OnboardingSpace.sm))
+        BenefitRow(
+            icon = Icons.Filled.Tune,
+            title = stringResource(R.string.reminder_benefit_reversible_title),
+            body = stringResource(R.string.reminder_benefit_reversible_body),
+        )
+    }
+}
+
+/** A bell in the brand squircle — same silhouette as the permission hero. */
+@Composable
+private fun BellHero() {
+    Box(
+        modifier = Modifier
+            .size(128.dp)
+            .clip(RoundedCornerShape(34.dp))
+            .background(MaterialTheme.colorScheme.primaryContainer),
+        contentAlignment = Alignment.Center,
+    ) {
+        Icon(
+            imageVector = Icons.Filled.NotificationsActive,
+            contentDescription = null,
+            tint = MaterialTheme.colorScheme.onPrimaryContainer,
+            modifier = Modifier.size(56.dp),
+        )
+    }
+}

app/src/main/java/de/jeanlucmakiola/calendula/ui/permission/ReminderOnboardingViewModel.kt

@@ -0,0 +1,39 @@
+package de.jeanlucmakiola.calendula.ui.permission
+
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewModelScope
+import dagger.hilt.android.lifecycle.HiltViewModel
+import de.jeanlucmakiola.calendula.data.prefs.SettingsPrefs
+import kotlinx.coroutines.flow.SharingStarted
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.flow.stateIn
+import kotlinx.coroutines.launch
+import javax.inject.Inject
+
+/**
+ * Gates the one-time reminder onboarding step (v1.4) shown after the calendar
+ * grant. [onboardingDone] is null until DataStore's first emission so the
+ * step neither flashes for users who completed it nor gets skipped.
+ */
+@HiltViewModel
+class ReminderOnboardingViewModel @Inject constructor(
+    private val prefs: SettingsPrefs,
+) : ViewModel() {
+
+    val onboardingDone: StateFlow<Boolean?> = prefs.reminderOnboardingDone
+        .map { done -> done as Boolean? }
+        .stateIn(
+            scope = viewModelScope,
+            started = SharingStarted.WhileSubscribed(5_000L),
+            initialValue = null,
+        )
+
+    /** Close the step, recording whether reminder notifications stay on. */
+    fun finish(remindersEnabled: Boolean) {
+        viewModelScope.launch {
+            prefs.setRemindersEnabled(remindersEnabled)
+            prefs.setReminderOnboardingDone()
+        }
+    }
+}

app/src/main/java/de/jeanlucmakiola/calendula/ui/settings/SettingsScreen.kt

@@ -1,7 +1,12 @@
 package de.jeanlucmakiola.calendula.ui.settings
 
+import android.Manifest
 import android.content.Intent
+import android.content.pm.PackageManager
+import android.os.Build
 import androidx.activity.compose.BackHandler
+import androidx.activity.compose.rememberLauncherForActivityResult
+import androidx.activity.result.contract.ActivityResultContracts
 import androidx.core.net.toUri
 import androidx.compose.foundation.background
 import androidx.compose.foundation.clickable
@@ -42,6 +47,7 @@ import androidx.compose.ui.Modifier
 import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.unit.dp
+import androidx.core.content.ContextCompat
 import androidx.hilt.navigation.compose.hiltViewModel
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import de.jeanlucmakiola.calendula.R
@@ -128,6 +134,13 @@ fun SettingsScreen(
                 )
             }
 
+            HorizontalDivider(Modifier.padding(vertical = 8.dp))
+            SectionHeader(stringResource(R.string.settings_section_notifications))
+            RemindersRow(
+                checked = state.remindersEnabled,
+                onCheckedChange = viewModel::setRemindersEnabled,
+            )
+
             HorizontalDivider(Modifier.padding(vertical = 8.dp))
             SectionHeader(stringResource(R.string.settings_section_language))
             LanguageRow()
@@ -249,6 +262,55 @@ private fun DynamicColorRow(
     }
 }
 
+/**
+ * Reminder-notifications toggle (v1.4), mirroring the onboarding step.
+ * Turning it on re-requests `POST_NOTIFICATIONS` when missing (API 33+) —
+ * the pref is set either way; the OS permission is the real gate.
+ */
+@Composable
+private fun RemindersRow(
+    checked: Boolean,
+    onCheckedChange: (Boolean) -> Unit,
+) {
+    val context = LocalContext.current
+    val launcher = rememberLauncherForActivityResult(
+        contract = ActivityResultContracts.RequestPermission(),
+    ) { /* The pref is already on; a denial just leaves the OS gate shut. */ }
+    Row(
+        modifier = Modifier
+            .fillMaxWidth()
+            .padding(horizontal = 24.dp, vertical = 12.dp),
+        verticalAlignment = Alignment.CenterVertically,
+    ) {
+        Column(Modifier.weight(1f)) {
+            Text(
+                text = stringResource(R.string.settings_reminders),
+                style = MaterialTheme.typography.bodyLarge,
+            )
+            Text(
+                text = stringResource(R.string.settings_reminders_hint),
+                style = MaterialTheme.typography.bodySmall,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+            )
+        }
+        Spacer(Modifier.width(16.dp))
+        Switch(
+            checked = checked,
+            onCheckedChange = { enabled ->
+                onCheckedChange(enabled)
+                val needsPermission = enabled &&
+                    Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU &&
+                    ContextCompat.checkSelfPermission(
+                        context, Manifest.permission.POST_NOTIFICATIONS,
+                    ) != PackageManager.PERMISSION_GRANTED
+                if (needsPermission) {
+                    launcher.launch(Manifest.permission.POST_NOTIFICATIONS)
+                }
+            },
+        )
+    }
+}
+
 @Composable
 private fun AboutSection() {
     val context = LocalContext.current

app/src/main/java/de/jeanlucmakiola/calendula/ui/settings/SettingsUiState.kt

@@ -18,4 +18,6 @@ data class SettingsUiState(
     val weekStart: WeekStartPref = WeekStartPref.AUTO,
     /** Optional event-form fields shown by default (rest behind "more fields"). */
     val defaultFormFields: Set<EventFormField> = SettingsPrefs.DEFAULT_FORM_FIELDS,
+    /** Whether Calendula posts reminder notifications (v1.4). */
+    val remindersEnabled: Boolean = true,
 )

app/src/main/java/de/jeanlucmakiola/calendula/ui/settings/SettingsViewModel.kt

@@ -28,13 +28,15 @@ class SettingsViewModel @Inject constructor(
             prefs.dynamicColor,
             prefs.weekStart,
             prefs.defaultFormFields,
-        ) { theme, dynamic, weekStart, formFields ->
+            prefs.remindersEnabled,
+        ) { theme, dynamic, weekStart, formFields, reminders ->
             SettingsUiState(
                 themeMode = theme,
                 dynamicColor = dynamic && dynamicColorAvailable,
                 dynamicColorAvailable = dynamicColorAvailable,
                 weekStart = weekStart,
                 defaultFormFields = formFields,
+                remindersEnabled = reminders,
             )
         }.stateIn(
             scope = viewModelScope,
@@ -57,4 +59,8 @@ class SettingsViewModel @Inject constructor(
     fun setFormFieldDefault(field: EventFormField, enabled: Boolean) {
         viewModelScope.launch { prefs.setFormFieldDefault(field, enabled) }
     }
+
+    fun setRemindersEnabled(enabled: Boolean) {
+        viewModelScope.launch { prefs.setRemindersEnabled(enabled) }
+    }
 }

app/src/main/res/drawable/ic_notification.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Monochrome status-bar mark: Material "event" calendar glyph. -->
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24"
+    android:tint="?attr/colorControlNormal">
+    <path
+        android:fillColor="@android:color/white"
+        android:pathData="M19,3h-1V1h-2v2H8V1H6v2H5C3.89,3 3.01,3.9 3.01,5L3,19c0,1.1 0.89,2 2,2h14c1.1,0 2,-0.9 2,-2V5C21,3.9 20.1,3 19,3zM19,19H5V8h14V19zM7,10h5v5H7V10z" />
+</vector>

app/src/main/res/values-de/strings.xml

@@ -159,6 +159,20 @@
     <!-- Geteilte Event-Strings -->
     <string name="event_untitled">(Ohne Titel)</string>
 
+    <!-- Erinnerungs-Benachrichtigungen (v1.4) -->
+    <string name="reminder_channel_name">Termin-Erinnerungen</string>
+    <string name="reminder_channel_description">Benachrichtigungen zu den Erinnerungszeiten deiner Termine</string>
+    <string name="reminder_onboarding_title">Keinen Termin mehr verpassen</string>
+    <string name="reminder_onboarding_body">Android zeigt Termin-Erinnerungen nicht von selbst — das muss eine Kalender-App tun. Überlass Calendula den Job.</string>
+    <string name="reminder_benefit_delivery_title">Erinnerungen, zugestellt</string>
+    <string name="reminder_benefit_delivery_body">Jede Erinnerung an deinen Terminen kommt pünktlich als Benachrichtigung an.</string>
+    <string name="reminder_benefit_duplicates_title">Noch eine zweite Kalender-App?</string>
+    <string name="reminder_benefit_duplicates_body">Wenn eine andere App ebenfalls Erinnerungen zeigt, siehst du sie doppelt — schalte sie dort oder hier ab.</string>
+    <string name="reminder_benefit_reversible_title">Jederzeit änderbar</string>
+    <string name="reminder_benefit_reversible_body">Der Schalter liegt in den Einstellungen unter Benachrichtigungen.</string>
+    <string name="reminder_onboarding_enable_button">Erinnerungen einschalten</string>
+    <string name="reminder_onboarding_skip_button">Später</string>
+
     <!-- View-Switcher (M1) -->
     <string name="view_month">Monat</string>
     <string name="view_week">Woche</string>
@@ -183,6 +197,9 @@
     <string name="settings_week_start_sunday">Sonntag</string>
     <string name="settings_section_event_form">Termin-Formular</string>
     <string name="settings_form_fields_hint">Standardmäßig angezeigte Felder — alles Weitere liegt hinter \"Weitere Felder\"</string>
+    <string name="settings_section_notifications">Benachrichtigungen</string>
+    <string name="settings_reminders">Termin-Erinnerungen</string>
+    <string name="settings_reminders_hint">Erinnerungen doppelt? Eine andere Kalender-App zeigt sie ebenfalls — schalte sie in einer der beiden ab.</string>
     <string name="settings_section_language">Sprache</string>
     <string name="settings_language">App-Sprache</string>
     <string name="settings_language_auto">Systemstandard</string>

app/src/main/res/values/strings.xml

@@ -160,6 +160,20 @@
     <!-- Shared event strings -->
     <string name="event_untitled">(No title)</string>
 
+    <!-- Reminder notifications (v1.4) -->
+    <string name="reminder_channel_name">Event reminders</string>
+    <string name="reminder_channel_description">Notifications at the reminder times of your events</string>
+    <string name="reminder_onboarding_title">Never miss an event</string>
+    <string name="reminder_onboarding_body">Android doesn\'t show event reminders by itself — a calendar app has to. Let Calendula take that job.</string>
+    <string name="reminder_benefit_delivery_title">Reminders, delivered</string>
+    <string name="reminder_benefit_delivery_body">Every reminder on your events arrives as a notification, right on time.</string>
+    <string name="reminder_benefit_duplicates_title">Using a second calendar app?</string>
+    <string name="reminder_benefit_duplicates_body">If another app also posts reminders, you\'ll see them twice — turn them off there or here.</string>
+    <string name="reminder_benefit_reversible_title">Change it anytime</string>
+    <string name="reminder_benefit_reversible_body">The switch lives in Settings, under Notifications.</string>
+    <string name="reminder_onboarding_enable_button">Turn on reminders</string>
+    <string name="reminder_onboarding_skip_button">Not now</string>
+
     <!-- View switcher (M1) -->
     <string name="view_month">Month</string>
     <string name="view_week">Week</string>
@@ -184,6 +198,9 @@
     <string name="settings_week_start_sunday">Sunday</string>
     <string name="settings_section_event_form">New event form</string>
     <string name="settings_form_fields_hint">Fields shown by default — everything else sits behind \"More fields\"</string>
+    <string name="settings_section_notifications">Notifications</string>
+    <string name="settings_reminders">Event reminders</string>
+    <string name="settings_reminders_hint">Seeing reminders twice? Another calendar app is posting them too — turn them off in one of the two.</string>
     <string name="settings_section_language">Language</string>
     <string name="settings_language">App language</string>
     <string name="settings_language_auto">System default</string>

app/src/test/java/de/jeanlucmakiola/calendula/data/prefs/SettingsPrefsTest.kt

@@ -100,6 +100,27 @@ class SettingsPrefsTest {
         assertThat(prefs.defaultFormFields.first()).containsExactly(EventFormField.Location)
     }
 
+    @Test
+    fun `reminders default to enabled, onboarding to not done`(@TempDir tempDir: Path) = runTest {
+        val prefs = SettingsPrefs(newDataStore(tempDir))
+        assertThat(prefs.remindersEnabled.first()).isTrue()
+        assertThat(prefs.reminderOnboardingDone.first()).isFalse()
+    }
+
+    @Test
+    fun `reminders toggle round-trips`(@TempDir tempDir: Path) = runTest {
+        val prefs = SettingsPrefs(newDataStore(tempDir))
+        prefs.setRemindersEnabled(false)
+        assertThat(prefs.remindersEnabled.first()).isFalse()
+    }
+
+    @Test
+    fun `reminder onboarding completes one-way`(@TempDir tempDir: Path) = runTest {
+        val prefs = SettingsPrefs(newDataStore(tempDir))
+        prefs.setReminderOnboardingDone()
+        assertThat(prefs.reminderOnboardingDone.first()).isTrue()
+    }
+
     @Test
     fun `explicit week-start prefs resolve regardless of locale`() {
         assertThat(WeekStartPref.MONDAY.resolveFirstDay(Locale.US)).isEqualTo(DayOfWeek.MONDAY)

app/src/test/java/de/jeanlucmakiola/calendula/data/reminders/ReminderTimeTextTest.kt

@@ -0,0 +1,85 @@
+package de.jeanlucmakiola.calendula.data.reminders
+
+import com.google.common.truth.Truth.assertThat
+import org.junit.jupiter.api.Test
+import java.time.LocalDate
+import java.time.LocalDateTime
+import java.time.ZoneId
+import java.time.ZoneOffset
+import java.util.Locale
+
+class ReminderTimeTextTest {
+
+    private val berlin = ZoneId.of("Europe/Berlin")
+
+    private fun millisAt(dateTime: LocalDateTime, zone: ZoneId): Long =
+        dateTime.atZone(zone).toInstant().toEpochMilli()
+
+    private fun utcMidnight(date: LocalDate): Long =
+        date.atStartOfDay(ZoneOffset.UTC).toInstant().toEpochMilli()
+
+    @Test
+    fun `timed event on one day shows just the time range`() {
+        val text = reminderTimeText(
+            beginMillis = millisAt(LocalDateTime.of(2026, 6, 11, 9, 30), berlin),
+            endMillis = millisAt(LocalDateTime.of(2026, 6, 11, 10, 0), berlin),
+            isAllDay = false,
+            zone = berlin,
+            locale = Locale.GERMANY,
+        )
+        assertThat(text).isEqualTo("09:30 – 10:00")
+    }
+
+    @Test
+    fun `timed event crossing midnight includes both dates`() {
+        val text = reminderTimeText(
+            beginMillis = millisAt(LocalDateTime.of(2026, 6, 11, 23, 30), berlin),
+            endMillis = millisAt(LocalDateTime.of(2026, 6, 12, 0, 30), berlin),
+            isAllDay = false,
+            zone = berlin,
+            locale = Locale.GERMANY,
+        )
+        assertThat(text).contains("11.06.2026")
+        assertThat(text).contains("12.06.2026")
+        assertThat(text).contains("23:30")
+    }
+
+    @Test
+    fun `all-day single day shows one date, read in UTC`() {
+        val text = reminderTimeText(
+            beginMillis = utcMidnight(LocalDate.of(2026, 6, 11)),
+            endMillis = utcMidnight(LocalDate.of(2026, 6, 12)),
+            isAllDay = true,
+            // Zone must not matter for all-day events: UTC midnight is
+            // 02:00 in Berlin — naive local reading would shift the day.
+            zone = berlin,
+            locale = Locale.GERMANY,
+        )
+        assertThat(text).isEqualTo("11.06.2026")
+    }
+
+    @Test
+    fun `all-day multi-day shows the last covered day, not the exclusive end`() {
+        val text = reminderTimeText(
+            beginMillis = utcMidnight(LocalDate.of(2026, 6, 11)),
+            endMillis = utcMidnight(LocalDate.of(2026, 6, 13)),
+            isAllDay = true,
+            zone = berlin,
+            locale = Locale.GERMANY,
+        )
+        assertThat(text).isEqualTo("11.06.2026 – 12.06.2026")
+    }
+
+    @Test
+    fun `degenerate all-day range never renders an inverted span`() {
+        val day = utcMidnight(LocalDate.of(2026, 6, 11))
+        val text = reminderTimeText(
+            beginMillis = day,
+            endMillis = day,
+            isAllDay = true,
+            zone = berlin,
+            locale = Locale.GERMANY,
+        )
+        assertThat(text).isEqualTo("11.06.2026")
+    }
+}