app/src/main/java/de/jeanlucmakiola/calendula/ui/month/MonthScreen.kt

@@ -9,6 +9,7 @@ import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.BoxWithConstraints
 import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.PaddingValues
 import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.fillMaxHeight
@@ -19,6 +20,10 @@ 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.lazy.LazyColumn
+import androidx.compose.foundation.lazy.LazyListState
+import androidx.compose.foundation.lazy.items
+import androidx.compose.foundation.lazy.rememberLazyListState
 import androidx.compose.foundation.shape.CircleShape
 import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.material.icons.Icons
@@ -36,9 +41,12 @@ import androidx.compose.material3.TopAppBar
 import androidx.compose.material3.TopAppBarDefaults
 import androidx.compose.material3.rememberDrawerState
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.CompositionLocalProvider
 import androidx.compose.runtime.derivedStateOf
 import androidx.compose.runtime.getValue
+import androidx.compose.runtime.key
+import androidx.compose.runtime.snapshotFlow
 import androidx.compose.runtime.mutableFloatStateOf
 import androidx.compose.runtime.mutableIntStateOf
 import androidx.compose.runtime.remember
@@ -85,11 +93,14 @@ import de.jeanlucmakiola.floret.locale.currentLocale
 import de.jeanlucmakiola.calendula.ui.common.rememberCalendarSlideSpec
 import de.jeanlucmakiola.calendula.ui.common.next
 import de.jeanlucmakiola.floret.time.isoWeekNumber
+import kotlinx.coroutines.flow.distinctUntilChanged
 import kotlinx.coroutines.launch
+import kotlinx.datetime.DateTimeUnit
 import kotlinx.datetime.DayOfWeek
 import kotlinx.datetime.LocalDate
 import kotlinx.datetime.TimeZone
 import kotlinx.datetime.YearMonth
+import kotlinx.datetime.plus
 import kotlinx.datetime.toJavaLocalDate
 import kotlinx.datetime.toLocalDateTime
 import kotlin.time.Clock
@@ -112,8 +123,10 @@ fun MonthScreen(
     viewModel: MonthViewModel = hiltViewModel(),
 ) {
     val state by viewModel.state.collectAsStateWithLifecycle()
+    val continuousState by viewModel.continuousState.collectAsStateWithLifecycle()
     val month by viewModel.month.collectAsStateWithLifecycle()
     val weekStart by viewModel.weekStart.collectAsStateWithLifecycle()
+    val viewStyle by viewModel.viewStyle.collectAsStateWithLifecycle()
     val dimCompleted by viewModel.dimCompletedEvents.collectAsStateWithLifecycle()
     val showWeekNumbers by viewModel.showWeekNumbers.collectAsStateWithLifecycle()
     // The instant before which an event counts as completed, or null when dimming
@@ -128,17 +141,52 @@ fun MonthScreen(
     val drawerState = rememberDrawerState(DrawerValue.Closed)
     val scope = rememberCoroutineScope()
 
-    val isOnCurrentMonth = when (val s = state) {
-        is MonthUiState.Success -> s.month == YearMonth(s.today.year, s.today.month)
-        else -> true
+    val continuous = viewStyle == MonthViewStyle.Continuous
+
+    // Today, from whichever state is driving; the clock only covers the first
+    // frame, before either has loaded.
+    val today = when {
+        continuous -> (continuousState as? ContinuousMonthUiState.Success)?.today
+        else -> (state as? MonthUiState.Success)?.today
+    } ?: Clock.System.now().toLocalDateTime(TimeZone.currentSystemDefault()).date
+
+    // Keyed on the week start: week indices are anchored on it, so a changed
+    // week start would leave the saved scroll offset pointing at a different week.
+    val listState = key(weekStart) {
+        rememberLazyListState(
+            initialFirstVisibleItemIndex =
+                weekIndexOf(LocalDate(month.year, month.month, 1), weekStart),
+        )
     }
 
-    // Drives whether the title carries the year. Falls back to the clock only
-    // while the first load is in flight, when there is no state to read today from.
-    val currentYear = when (val s = state) {
-        is MonthUiState.Success -> s.today.year
-        else -> Clock.System.now().toLocalDateTime(TimeZone.currentSystemDefault()).date.year
+    // The continuous stream has no single "current" month, so the title takes the
+    // one the viewport mostly sits in: the midweek day of the row below the top
+    // edge, which flips over as that month's first full week comes into view.
+    val visibleMonth by remember(weekStart) {
+        derivedStateOf {
+            val midweek = weekStartForIndex(listState.firstVisibleItemIndex + 1, weekStart)
+                .plus(3, DateTimeUnit.DAY)
+            YearMonth(midweek.year, midweek.month)
         }
+    }
+    val titleMonth = if (continuous) visibleMonth else month
+
+    // Feed the visible range back so the sliding data window can follow. The
+    // view model ignores everything that doesn't near a loaded edge.
+    LaunchedEffect(listState, continuous) {
+        if (!continuous) return@LaunchedEffect
+        snapshotFlow {
+            val visible = listState.layoutInfo.visibleItemsInfo
+            (visible.firstOrNull()?.index ?: 0) to (visible.lastOrNull()?.index ?: 0)
+        }
+            .distinctUntilChanged()
+            .collect { (first, last) -> viewModel.onVisibleWeeksChanged(first, last) }
+    }
+
+    val isOnCurrentMonth = titleMonth == YearMonth(today.year, today.month)
+
+    // Drives whether the title carries the year.
+    val currentYear = today.year
 
     // Slide direction for the grid transition: +1 = next, -1 = prev, 0 = jump (no slide).
     var slideDir by remember { mutableIntStateOf(0) }
@@ -152,8 +200,13 @@ fun MonthScreen(
         viewModel.goToPrev()
     }
     // Slide toward today: viewing the future → today comes in from the left
-    // (back), viewing the past → from the right (forward).
+    // (back), viewing the past → from the right (forward). The continuous stream
+    // scrolls to today's week instead — there is nothing to slide.
     val jumpToToday = {
+        if (continuous) {
+            scope.launch { listState.animateScrollToItem(weekIndexOf(today, weekStart)) }
+            Unit
+        } else {
             slideDir = when (val s = state) {
                 is MonthUiState.Success ->
                     if (YearMonth(s.today.year, s.today.month) < s.month) -1 else 1
@@ -161,11 +214,20 @@ fun MonthScreen(
             }
             viewModel.goToToday()
         }
+    }
     // Drawer jump-to-date: slide from the side the target month lies on.
     val jumpToDate: (LocalDate) -> Unit = { target ->
+        if (continuous) {
+            scope.launch {
+                listState.animateScrollToItem(
+                    weekIndexOf(LocalDate(target.year, target.month, 1), weekStart),
+                )
+            }
+        } else {
             slideDir = if (YearMonth(target.year, target.month) < month) -1 else 1
             viewModel.goToDate(target)
         }
+    }
 
     ModalNavigationDrawer(
         drawerState = drawerState,
@@ -174,7 +236,7 @@ fun MonthScreen(
         drawerContent = {
             CalendarDrawer(
                 currentView = selectedView,
-                currentDate = LocalDate(month.year, month.month, 1),
+                currentDate = LocalDate(titleMonth.year, titleMonth.month, 1),
                 viewOrder = drawerViewOrder,
                 onSelectView = { view ->
                     onSelectView(view)
@@ -195,7 +257,7 @@ fun MonthScreen(
             modifier = modifier.nestedScroll(scrollBehavior.nestedScrollConnection),
             topBar = {
                 MonthTopBar(
-                    month = month,
+                    month = titleMonth,
                     currentYear = currentYear,
                     selectedView = selectedView,
                     onCycleView = { onSelectView(selectedView.next(quickSwitchViews)) },
@@ -213,11 +275,9 @@ fun MonthScreen(
                     onToday = jumpToToday,
                     onCreate = {
                         // Anchor on today when its month is shown, else the 1st.
-                        val today = Clock.System.now()
-                            .toLocalDateTime(TimeZone.currentSystemDefault()).date
                         onCreateEvent(
                             if (isOnCurrentMonth) today
-                            else LocalDate(month.year, month.month, 1),
+                            else LocalDate(titleMonth.year, titleMonth.month, 1),
                             null,
                         )
                     },
@@ -231,6 +291,15 @@ fun MonthScreen(
             ) {
                 WeekdayHeader(weekStart = weekStart, showWeekNumbers = showWeekNumbers)
                 CompositionLocalProvider(LocalDimCutoff provides dimCutoff) {
+                    if (continuous) {
+                        ContinuousMonthContent(
+                            state = continuousState,
+                            listState = listState,
+                            showWeekNumbers = showWeekNumbers,
+                            onRetry = jumpToToday,
+                            onOpenDay = onOpenDay,
+                        )
+                    } else {
                         MonthContent(
                             state = state,
                             slideDir = slideDir,
@@ -244,6 +313,7 @@ fun MonthScreen(
                 }
             }
         }
+    }
 }
 
 @Composable
@@ -303,6 +373,32 @@ private fun MonthContent(
     }
 }
 
+/**
+ * Continuous style content. No swipe detector and no [AnimatedContent]: vertical
+ * scrolling owns the gesture, and the list never swaps wholesale — it keeps
+ * scrolling while the window behind it reloads.
+ */
+@Composable
+private fun ContinuousMonthContent(
+    state: ContinuousMonthUiState,
+    listState: LazyListState,
+    showWeekNumbers: Boolean,
+    onRetry: () -> Unit,
+    onOpenDay: (LocalDate) -> Unit,
+) {
+    when (state) {
+        ContinuousMonthUiState.Loading -> MonthGridLoading()
+        is ContinuousMonthUiState.Failure ->
+            CalendarFailure(reason = state.reason, onRetry = onRetry)
+        is ContinuousMonthUiState.Success -> ContinuousMonthGrid(
+            state = state,
+            listState = listState,
+            showWeekNumbers = showWeekNumbers,
+            onOpenDay = onOpenDay,
+        )
+    }
+}
+
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
 private fun MonthTopBar(
@@ -391,6 +487,14 @@ private val CELL_GAP = 2.dp
 private val CELL_SHAPE = RoundedCornerShape(12.dp)
 private const val MAX_EVENT_ROWS = 3
 
+/**
+ * Row height in the continuous grid. The paged grid divides the viewport between
+ * however many rows the month has; a scrolling stream has no such bound, so it
+ * fixes a height that seats the day number plus [MAX_EVENT_ROWS] event rows —
+ * close to what a five-row month gets on a typical phone.
+ */
+private val CONTINUOUS_ROW_HEIGHT = 112.dp
+
 @Composable
 private fun MonthGrid(
     state: MonthUiState.Success,
@@ -406,11 +510,12 @@ private fun MonthGrid(
             .padding(horizontal = 8.dp, vertical = 4.dp),
         verticalArrangement = Arrangement.spacedBy(2.dp),
     ) {
+        val month = state.month
         state.weeks.forEach { week ->
             MonthWeekRow(
                 week = week,
                 today = state.today,
-                month = state.month,
+                inMonth = { it.month == month.month && it.year == month.year },
                 showWeekNumbers = showWeekNumbers,
                 onOpenDay = onOpenDay,
                 modifier = Modifier
@@ -421,6 +526,78 @@ private fun MonthGrid(
     }
 }
 
+/**
+ * The continuous grid (#38): one uninterrupted vertical stream of weeks.
+ *
+ * The list is indexed by *absolute week number*, so a row's identity never
+ * changes and there is no page seam to scroll across. Weeks the loaded window
+ * hasn't reached yet render as a skeleton and pull the window along behind them.
+ *
+ * Deliberately not a stack of month grids — that would still repeat a boundary
+ * week at the end of one month and the start of the next, which is exactly the
+ * duplication #38 asks to be rid of.
+ */
+@Composable
+private fun ContinuousMonthGrid(
+    state: ContinuousMonthUiState.Success,
+    listState: LazyListState,
+    showWeekNumbers: Boolean,
+    onOpenDay: (LocalDate) -> Unit,
+    modifier: Modifier = Modifier,
+) {
+    val weekCount = remember(state.weekStart) { continuousWeekCount(state.weekStart) }
+    LazyColumn(
+        state = listState,
+        modifier = modifier
+            .fillMaxSize()
+            .padding(horizontal = 8.dp),
+        verticalArrangement = Arrangement.spacedBy(2.dp),
+        // Bottom inset clears the FAB stack so the last row stays tappable.
+        contentPadding = PaddingValues(top = 4.dp, bottom = 96.dp),
+    ) {
+        items(count = weekCount, key = { it }) { index ->
+            val week = state.weeksByIndex[index]
+            if (week == null) {
+                ContinuousWeekPlaceholder()
+            } else {
+                MonthWeekRow(
+                    week = week,
+                    today = state.today,
+                    // Every day in the stream belongs to a month equally — there
+                    // is no "other month" to recede here.
+                    inMonth = { true },
+                    showWeekNumbers = showWeekNumbers,
+                    onOpenDay = onOpenDay,
+                    labelMonthOnFirst = true,
+                    modifier = Modifier
+                        .fillMaxWidth()
+                        .height(CONTINUOUS_ROW_HEIGHT),
+                )
+            }
+        }
+    }
+}
+
+/** A week the sliding window hasn't loaded yet — same height, so nothing jumps. */
+@Composable
+private fun ContinuousWeekPlaceholder() {
+    Row(
+        modifier = Modifier
+            .fillMaxWidth()
+            .height(CONTINUOUS_ROW_HEIGHT),
+    ) {
+        repeat(7) {
+            Box(
+                modifier = Modifier
+                    .weight(1f)
+                    .fillMaxHeight()
+                    .padding(horizontal = CELL_GAP, vertical = 1.dp)
+                    .background(MaterialTheme.colorScheme.surfaceContainerLow, CELL_SHAPE),
+            )
+        }
+    }
+}
+
 /**
  * One week of the grid. Bars (all-day / multi-day) are positioned absolutely so
  * a multi-day event is one connected bar across the columns; single-day timed
@@ -432,10 +609,11 @@ private fun MonthGrid(
 private fun MonthWeekRow(
     week: MonthWeek,
     today: LocalDate,
-    month: YearMonth,
+    inMonth: (LocalDate) -> Boolean,
     showWeekNumbers: Boolean,
     onOpenDay: (LocalDate) -> Unit,
     modifier: Modifier = Modifier,
+    labelMonthOnFirst: Boolean = false,
 ) {
     val dark = isSystemInDarkTheme()
     val laneCount = (week.spans.maxOfOrNull { it.lane } ?: -1) + 1
@@ -466,14 +644,13 @@ private fun MonthWeekRow(
             // as one continuous event.
             Row(Modifier.matchParentSize()) {
                 week.days.forEach { d ->
-                    val inMonth = d.month == month.month && d.year == month.year
                     Box(
                         Modifier
                             .weight(1f)
                             .fillMaxHeight()
                             .padding(horizontal = CELL_GAP, vertical = 1.dp)
                             .background(
-                                color = if (inMonth) MaterialTheme.colorScheme.surfaceContainer
+                                color = if (inMonth(d)) MaterialTheme.colorScheme.surfaceContainer
                                 else MaterialTheme.colorScheme.surfaceContainerLow,
                                 shape = CELL_SHAPE,
                             ),
@@ -487,7 +664,15 @@ private fun MonthWeekRow(
                         DayNumberCell(
                             date = d,
                             isToday = d == today,
-                            inMonth = d.month == month.month && d.year == month.year,
+                            inMonth = inMonth(d),
+                            // Continuous has no month boundaries to dim across, so
+                            // the 1st names its month instead — the only marker
+                            // telling one month from the next inside the stream.
+                            monthLabel = if (labelMonthOnFirst && d.day == 1) {
+                                shortMonthName(d)
+                            } else {
+                                null
+                            },
                             modifier = Modifier.weight(1f),
                         )
                     }
@@ -620,6 +805,7 @@ private fun DayNumberCell(
     isToday: Boolean,
     inMonth: Boolean,
     modifier: Modifier = Modifier,
+    monthLabel: String? = null,
 ) {
     Box(
         modifier = modifier.height(DAY_NUMBER_HEIGHT),
@@ -639,6 +825,16 @@ private fun DayNumberCell(
                     color = MaterialTheme.colorScheme.onPrimary,
                 )
             }
+        } else if (monthLabel != null) {
+            Text(
+                text = "$monthLabel ${date.day}",
+                style = MaterialTheme.typography.labelMedium,
+                fontWeight = FontWeight.Bold,
+                color = MaterialTheme.colorScheme.primary,
+                maxLines = 1,
+                overflow = TextOverflow.Visible,
+                softWrap = false,
+            )
         } else {
             Text(
                 text = date.day.toString(),
@@ -650,6 +846,16 @@ private fun DayNumberCell(
     }
 }
 
+/** Locale-short month name ("Jul", "Juli"), for the 1st in the continuous grid. */
+@Composable
+private fun shortMonthName(date: LocalDate): String {
+    val locale = currentLocale()
+    return remember(date.month, locale) {
+        java.time.Month.of(date.month.ordinal + 1)
+            .getDisplayName(JavaTextStyle.SHORT, locale)
+    }
+}
+
 /** A filled event pill/bar — softened (or raw) fill, title clipped to one line. */
 @Composable
 private fun MonthBar(

app/src/main/java/de/jeanlucmakiola/calendula/ui/month/MonthUiState.kt

@@ -2,6 +2,7 @@ package de.jeanlucmakiola.calendula.ui.month
 
 import de.jeanlucmakiola.calendula.domain.EventInstance
 import de.jeanlucmakiola.calendula.domain.FailureReason
+import kotlinx.datetime.DayOfWeek
 import kotlinx.datetime.LocalDate
 import kotlinx.datetime.YearMonth
 
@@ -37,6 +38,23 @@ data class MonthWeek(
     val countByDay: Map<LocalDate, Int>,
 )
 
+/**
+ * State for the continuous style (#38). Weeks are keyed by absolute week index
+ * rather than gathered into months: the whole point of the style is that there
+ * are no month boundaries to scroll across, so there is no "current month" here
+ * and no notion of an out-of-month day. [weeksByIndex] holds only the loaded
+ * window; indices outside it render as placeholders until the window catches up.
+ */
+sealed interface ContinuousMonthUiState {
+    data object Loading : ContinuousMonthUiState
+    data class Failure(val reason: FailureReason) : ContinuousMonthUiState
+    data class Success(
+        val today: LocalDate,
+        val weeksByIndex: Map<Int, MonthWeek>,
+        val weekStart: DayOfWeek,
+    ) : ContinuousMonthUiState
+}
+
 sealed interface MonthUiState {
     data object Loading : MonthUiState
     data class Failure(val reason: FailureReason) : MonthUiState

app/src/main/java/de/jeanlucmakiola/calendula/ui/month/MonthViewModel.kt

@@ -29,6 +29,7 @@ import kotlinx.datetime.TimeZone
 import kotlinx.datetime.YearMonth
 import kotlinx.datetime.atStartOfDayIn
 import kotlinx.datetime.atTime
+import kotlinx.datetime.daysUntil
 import kotlinx.datetime.minus
 import kotlinx.datetime.plus
 import kotlinx.datetime.toInstant
@@ -66,6 +67,14 @@ class MonthViewModel @Inject constructor(
             initialValue = false,
         )
 
+    /** How the grid is laid out and navigated (#38, #53). */
+    val viewStyle: StateFlow<MonthViewStyle> = settingsPrefs.monthViewStyle
+        .stateIn(
+            scope = viewModelScope,
+            started = SharingStarted.WhileSubscribed(5_000L),
+            initialValue = MonthViewStyle.Paged,
+        )
+
     private val todayDate: LocalDate
         get() = Clock.System.now().toLocalDateTime(zone).date
 
@@ -91,6 +100,73 @@ class MonthViewModel @Inject constructor(
                 initialValue = MonthUiState.Loading,
             )
 
+    // --- Continuous style (#38) -------------------------------------------
+    //
+    // The continuous grid is one endless stream of weeks, so it can't load "a
+    // month" — it loads a sliding window of week indices around whatever is on
+    // screen. The window only moves when the visible range comes within
+    // WINDOW_EDGE weeks of a loaded edge, so a scroll re-queries occasionally
+    // rather than on every frame.
+
+    // Seeded around today so the first frame has data. The week-start preference
+    // hasn't arrived yet, but anchoring on a different day shifts an index by at
+    // most one week — well inside the pad, and the first scroll report corrects it.
+    private val _loadedWeeks = MutableStateFlow(
+        weekIndexOf(todayDate, DayOfWeek.MONDAY).let { it - WINDOW_PAD..it + WINDOW_PAD },
+    )
+
+    val continuousState: StateFlow<ContinuousMonthUiState> =
+        combine(_loadedWeeks, weekStart) { window, ws -> window to ws }
+            .flatMapLatest { (window, ws) ->
+                val first = weekStartForIndex(window.first, ws)
+                val last = weekStartForIndex(window.last, ws).plus(6, DateTimeUnit.DAY)
+                val range = first.atStartOfDayIn(zone)..last.atTime(23, 59, 59).toInstant(zone)
+                combine(
+                    repository.calendars(),
+                    repository.instances(range),
+                ) { calendars, instances ->
+                    buildContinuousState(window, ws, calendars, instances)
+                }
+            }
+            .catch { emit(ContinuousMonthUiState.Failure(FailureReason.ProviderUnavailable)) }
+            .flowOn(io)
+            .stateIn(
+                scope = viewModelScope,
+                started = SharingStarted.WhileSubscribed(5_000L),
+                initialValue = ContinuousMonthUiState.Loading,
+            )
+
+    /**
+     * Report which absolute week indices are on screen. Cheap to call on every
+     * scroll frame: it returns immediately unless the visible range has drifted
+     * close enough to a loaded edge to warrant a wider query.
+     */
+    fun onVisibleWeeksChanged(firstIndex: Int, lastIndex: Int) {
+        nextLoadWindow(_loadedWeeks.value, firstIndex, lastIndex)?.let { _loadedWeeks.value = it }
+    }
+
+    private fun buildContinuousState(
+        window: IntRange,
+        weekStart: DayOfWeek,
+        calendars: List<CalendarSource>,
+        instances: List<EventInstance>,
+    ): ContinuousMonthUiState {
+        if (calendars.isEmpty()) {
+            return ContinuousMonthUiState.Failure(FailureReason.NoCalendarsConfigured)
+        }
+        val weeks = window.associateWith { index ->
+            val days = (0 until 7).map {
+                weekStartForIndex(index, weekStart).plus(it, DateTimeUnit.DAY)
+            }
+            layoutCalendarWeek(days, instances, zone)
+        }
+        return ContinuousMonthUiState.Success(
+            today = todayDate,
+            weeksByIndex = weeks,
+            weekStart = weekStart,
+        )
+    }
+
     fun goToPrev() {
         _month.value = _month.value.minus(1, DateTimeUnit.MONTH)
     }
@@ -225,6 +301,52 @@ internal fun monthGridRange(
     return start..end
 }
 
+/**
+ * How many weeks the continuous window loads beyond the visible range, and how
+ * close the visible range may drift to a loaded edge before it reloads. The pad
+ * is generous relative to the trigger so a steady scroll crosses the trigger
+ * well before it would run out of laid-out weeks.
+ */
+private const val WINDOW_PAD = 12
+private const val WINDOW_EDGE = 4
+
+/**
+ * The window to load for a visible range, or null to keep the current one.
+ *
+ * Kept pure and separate from the view model so the hysteresis — the reason a
+ * scroll doesn't re-query the provider on every frame — is testable on its own.
+ */
+internal fun nextLoadWindow(loaded: IntRange, firstVisible: Int, lastVisible: Int): IntRange? {
+    val comfortablyInside =
+        firstVisible - WINDOW_EDGE >= loaded.first && lastVisible + WINDOW_EDGE <= loaded.last
+    if (comfortablyInside) return null
+    return (firstVisible - WINDOW_PAD)..(lastVisible + WINDOW_PAD)
+}
+
+/**
+ * The continuous grid addresses weeks by an absolute index rather than a
+ * (month, row) pair, so the list has one stable, gap-free coordinate space to
+ * scroll through and key its items by. Index 0 is the first week of 1900 under
+ * the active week-start; the list runs to [CONTINUOUS_WEEK_COUNT].
+ *
+ * The epoch is deliberately far in the past so every index is non-negative,
+ * which keeps the LazyColumn's item indices and week indices the same number.
+ */
+private val WEEK_INDEX_EPOCH = LocalDate(1900, 1, 1)
+private val WEEK_INDEX_END = LocalDate(2100, 12, 31)
+
+internal fun weekIndexOf(date: LocalDate, weekStart: DayOfWeek): Int {
+    val base = WEEK_INDEX_EPOCH.startOfGridWeek(weekStart)
+    return base.daysUntil(date.startOfGridWeek(weekStart)) / 7
+}
+
+internal fun weekStartForIndex(index: Int, weekStart: DayOfWeek): LocalDate =
+    WEEK_INDEX_EPOCH.startOfGridWeek(weekStart).plus(index * 7, DateTimeUnit.DAY)
+
+/** Total weeks the continuous grid scrolls through (1900 → 2100). */
+internal fun continuousWeekCount(weekStart: DayOfWeek): Int =
+    weekIndexOf(WEEK_INDEX_END, weekStart) + 1
+
 internal fun LocalDate.startOfGridWeek(weekStart: DayOfWeek): LocalDate {
     // DayOfWeek.ordinal: MONDAY=0..SUNDAY=6 → identical to ISO ordering.
     val offset = ((dayOfWeek.ordinal - weekStart.ordinal) + 7) % 7

app/src/test/java/de/jeanlucmakiola/calendula/ui/month/ContinuousWeekIndexTest.kt

@@ -0,0 +1,104 @@
+package de.jeanlucmakiola.calendula.ui.month
+
+import com.google.common.truth.Truth.assertThat
+import kotlinx.datetime.DateTimeUnit
+import kotlinx.datetime.DayOfWeek
+import kotlinx.datetime.LocalDate
+import kotlinx.datetime.plus
+import org.junit.jupiter.api.Test
+
+/**
+ * The continuous grid's coordinate space. Every row's identity — and the
+ * LazyColumn item it maps to — hangs off this arithmetic, so it gets its own
+ * tests rather than being exercised only through the UI.
+ */
+class ContinuousWeekIndexTest {
+
+    // 2026-06-08 is a Monday; 2026-06-10 the Wednesday of the same week.
+    private val mon = LocalDate(2026, 6, 8)
+    private val wed = LocalDate(2026, 6, 10)
+
+    @Test
+    fun `every day of a week shares one index`() {
+        val indices = (0..6).map { weekIndexOf(mon.plus(it, DateTimeUnit.DAY), DayOfWeek.MONDAY) }
+        assertThat(indices.toSet()).hasSize(1)
+    }
+
+    @Test
+    fun `consecutive weeks are consecutive indices`() {
+        val a = weekIndexOf(mon, DayOfWeek.MONDAY)
+        val b = weekIndexOf(mon.plus(7, DateTimeUnit.DAY), DayOfWeek.MONDAY)
+        val back = weekIndexOf(mon.plus(-7, DateTimeUnit.DAY), DayOfWeek.MONDAY)
+        assertThat(b).isEqualTo(a + 1)
+        assertThat(back).isEqualTo(a - 1)
+    }
+
+    @Test
+    fun `index round-trips back to the week's first day`() {
+        DayOfWeek.entries.forEach { ws ->
+            val index = weekIndexOf(wed, ws)
+            assertThat(weekStartForIndex(index, ws)).isEqualTo(wed.startOfGridWeek(ws))
+        }
+    }
+
+    @Test
+    fun `the week start shifts which week a boundary day belongs to`() {
+        // Sunday the 14th closes the Monday-anchored week but opens the Sunday one.
+        val sun = LocalDate(2026, 6, 14)
+        assertThat(weekIndexOf(sun, DayOfWeek.MONDAY))
+            .isEqualTo(weekIndexOf(mon, DayOfWeek.MONDAY))
+        assertThat(weekIndexOf(sun, DayOfWeek.SUNDAY))
+            .isEqualTo(weekIndexOf(sun.plus(1, DateTimeUnit.DAY), DayOfWeek.SUNDAY))
+    }
+
+    @Test
+    fun `indices are non-negative across the supported span`() {
+        // The epoch sits before any date the grid scrolls to, so item indices and
+        // week indices stay the same number — no offset to reconcile.
+        DayOfWeek.entries.forEach { ws ->
+            assertThat(weekIndexOf(LocalDate(1900, 1, 1), ws)).isAtLeast(0)
+            assertThat(weekIndexOf(LocalDate(2026, 6, 8), ws)).isGreaterThan(0)
+        }
+    }
+
+    @Test
+    fun `the list spans 1900 through 2100`() {
+        DayOfWeek.entries.forEach { ws ->
+            val count = continuousWeekCount(ws)
+            assertThat(weekIndexOf(LocalDate(2100, 12, 31), ws)).isLessThan(count)
+            assertThat(weekIndexOf(LocalDate(2026, 6, 8), ws)).isLessThan(count)
+            // ~200 years of weeks, give or take the anchor.
+            assertThat(count).isIn(10_400..10_500)
+        }
+    }
+
+    @Test
+    fun `a window comfortably around the visible range is kept`() {
+        assertThat(nextLoadWindow(loaded = 0..100, firstVisible = 40, lastVisible = 45)).isNull()
+    }
+
+    @Test
+    fun `nearing a loaded edge widens the window around the visible range`() {
+        // Within four weeks of the top edge → reload, padded on both sides.
+        val widened = nextLoadWindow(loaded = 0..100, firstVisible = 2, lastVisible = 7)
+        assertThat(widened).isEqualTo(-10..19)
+
+        val atBottom = nextLoadWindow(loaded = 0..100, firstVisible = 94, lastVisible = 99)
+        assertThat(atBottom).isEqualTo(82..111)
+    }
+
+    @Test
+    fun `a jump far outside the window reloads around the destination`() {
+        assertThat(nextLoadWindow(loaded = 0..100, firstVisible = 500, lastVisible = 505))
+            .isEqualTo(488..517)
+    }
+
+    @Test
+    fun `the reloaded window always clears the trigger it just crossed`() {
+        // Otherwise every scroll frame would re-trigger a query.
+        var loaded = 0..100
+        val window = nextLoadWindow(loaded, firstVisible = 2, lastVisible = 7)!!
+        loaded = window
+        assertThat(nextLoadWindow(loaded, firstVisible = 2, lastVisible = 7)).isNull()
+    }
+}