fix timers

android/app/src/main/kotlin/tech/kadence/android/data/KadenceRepository.kt

@@ -82,8 +82,19 @@ class KadenceRepository(val api: KadenceApi) {
 
     suspend fun resume(): ApiResult<TimerStateDto> = api.post("/api/timer/resume")
 
-    suspend fun complete(autoNext: Boolean = true): ApiResult<TimerStateDto> =
-        api.post("/api/timer/complete", body("auto_next" to autoNext))
+    /**
+     * @param sessionId the interval the caller believes it is finishing. The server
+     *   ignores a call that names an interval which is no longer running — which is
+     *   what stops two clients reaching zero in the same second from completing the
+     *   break the first one's `auto_next` has just begun. Null means unconditional.
+     */
+    suspend fun complete(
+        autoNext: Boolean = true,
+        sessionId: Long? = null,
+    ): ApiResult<TimerStateDto> = api.post(
+        "/api/timer/complete",
+        body("auto_next" to autoNext, "session_id" to sessionId),
+    )
 
     suspend fun abandon(reason: String? = null): ApiResult<TimerStateDto> =
         api.post("/api/timer/abandon", body("reason" to reason))
@@ -98,7 +109,25 @@ class KadenceRepository(val api: KadenceApi) {
 
     // ---- tasks --------------------------------------------------------------
 
-    suspend fun tasks(): ApiResult<TaskListDto> = api.get("/api/tasks")
+    /**
+     * The task list.
+     *
+     * The calendar needs history — a past month is only worth looking at if the
+     * work that finished is on it, and laundry slots go `stale` rather than done
+     * — so it asks for the archive too. The defaults keep every existing caller
+     * byte-identical, and both views filter defensively anyway, so whichever
+     * payload was cached last is still rendered correctly.
+     */
+    suspend fun tasks(
+        includeDone: Boolean = false,
+        includeStale: Boolean = false,
+    ): ApiResult<TaskListDto> = api.get(
+        if (includeDone || includeStale) {
+            "/api/tasks?include_done=$includeDone&include_stale=$includeStale"
+        } else {
+            "/api/tasks"
+        },
+    )
 
     /** Fans out to Jira, Todoist, Google and the laundry site; slow by nature. */
     suspend fun refreshTasks(): ApiResult<RefreshResultDto> = api.post("/api/tasks/refresh")

android/app/src/main/kotlin/tech/kadence/android/data/dto/Dtos.kt

@@ -20,6 +20,7 @@ package tech.kadence.android.data.dto
 
 import kotlinx.serialization.SerialName
 import kotlinx.serialization.Serializable
+import tech.kadence.core.CalendarItem
 
 @Serializable
 data class TaskRefDto(
@@ -63,20 +64,25 @@ data class TimerStateDto(
     @SerialName("timer_enabled") val timerEnabled: Boolean = true,
 )
 
+/**
+ * A task, and — via [CalendarItem] — something the month grid can lay out
+ * directly, the way [KadenceConfig] is an `AuthConfig`. The alternative was a
+ * mapping layer between the wire and the grid that would only ever copy fields.
+ */
 @Serializable
 data class TaskDto(
-    val id: Long = 0,
-    val source: String = "",
-    @SerialName("source_label") val sourceLabel: String = "",
+    override val id: Long = 0,
+    override val source: String = "",
+    @SerialName("source_label") override val sourceLabel: String = "",
     @SerialName("external_id") val externalId: String = "",
     val title: String = "",
     val description: String? = null,
     val url: String? = null,
-    val project: String? = null,
+    override val project: String? = null,
     val status: String? = null,
     val priority: String? = null,
-    @SerialName("due_date") val dueDate: String? = null,
-    @SerialName("start_date") val startDate: String? = null,
+    @SerialName("due_date") override val dueDate: String? = null,
+    @SerialName("start_date") override val startDate: String? = null,
     val labels: List<String> = emptyList(),
     @SerialName("is_done") val isDone: Boolean = false,
     val pinned: Boolean = false,
@@ -84,7 +90,7 @@ data class TaskDto(
     @SerialName("estimated_pomodoros") val estimatedPomodoros: Int? = null,
     @SerialName("days_overdue") val daysOverdue: Int = 0,
     val bucket: String = "someday",
-)
+) : CalendarItem
 
 @Serializable
 data class TaskListDto(

android/app/src/main/kotlin/tech/kadence/android/data/store/KadencePrefs.kt

@@ -75,6 +75,28 @@ class KadencePrefs(context: Context) {
         get() = prefs.getLong(KEY_UPDATE_CHECKED_AT, 0L)
         set(value) = prefs.edit().putLong(KEY_UPDATE_CHECKED_AT, value).apply()
 
+    /**
+     * How the Tasks screen was last left, deliberately outside [KadenceConfig]
+     * for the same reason as the update bookkeeping above: a view toggle or a
+     * filter checkbox must not push the config StateFlow and recompose every
+     * screen in the app. Nothing outside that one screen reads them, and
+     * `TimerService` certainly does not.
+     */
+    var tasksCalendarView: Boolean
+        get() = prefs.getBoolean(KEY_TASKS_CALENDAR, false)
+        set(value) = prefs.edit().putBoolean(KEY_TASKS_CALENDAR, value).apply()
+
+    var tasksShowLong: Boolean
+        get() = prefs.getBoolean(KEY_TASKS_SHOW_LONG, false)
+        set(value) = prefs.edit().putBoolean(KEY_TASKS_SHOW_LONG, value).apply()
+
+    /** Hidden source/project keys — never the visible ones. See `isHidden`. */
+    var tasksHiddenKeys: Set<String>
+        // The returned set is owned by SharedPreferences and must not be handed
+        // out or mutated; copy it on the way through.
+        get() = prefs.getStringSet(KEY_TASKS_HIDDEN, emptySet())?.toSet() ?: emptySet()
+        set(value) = prefs.edit().putStringSet(KEY_TASKS_HIDDEN, value.toSet()).apply()
+
     fun update(transform: (KadenceConfig) -> KadenceConfig) {
         val next = transform(_config.value)
         prefs.edit().apply {
@@ -105,6 +127,9 @@ class KadencePrefs(context: Context) {
         private const val KEY_ONBOARDED = "onboarded"
         private const val KEY_UPDATE_SKIPPED = "update_skipped_version"
         private const val KEY_UPDATE_CHECKED_AT = "update_checked_at"
+        private const val KEY_TASKS_CALENDAR = "tasks_calendar_view"
+        private const val KEY_TASKS_SHOW_LONG = "tasks_show_long"
+        private const val KEY_TASKS_HIDDEN = "tasks_hidden_keys"
 
         fun normalizeBaseUrl(raw: String): String {
             val trimmed = raw.trim().trimEnd('/')

android/app/src/main/kotlin/tech/kadence/android/timer/TimerEngine.kt

@@ -22,7 +22,10 @@
  * whose time is up — it just reports `remaining_seconds = 0`. A client has to call
  * `complete`. `desktop/kadence_desktop/controller.py` does the same, with the same
  * re-entry guard, because without one a 1 Hz tick at zero fires `complete` every second
- * until the reply lands.
+ * until the reply lands. The guard is per interval id and the call names the interval
+ * it means to finish: the countdown runs out on every client at once, and a complete
+ * that arrives after someone else's has already rolled the timer on would otherwise
+ * finish the interval that rolling on created.
  */
 package tech.kadence.android.timer
 
@@ -147,8 +150,17 @@ class TimerEngine(
      */
     private val mutex = Mutex()
 
-    /** The `complete` re-entry guard. See the file header. */
-    private var completing = false
+    /**
+     * The interval we have already asked the server to finish. See the file header.
+     *
+     * An id, not a bare flag: a poll issued just before the countdown ran out answers
+     * with that interval still running at 00:00, and a flag cleared by that answer
+     * sends `complete` a second time — onto whatever `auto_next` has since started,
+     * which is how a break could end the instant it began. Ids are never reused, so
+     * the second attempt is never made; a call that *failed* clears it so the zero
+     * crossing is still retried.
+     */
+    private var completedId: Long? = null
 
     private var pollJob: Job? = null
     private var tickJob: Job? = null
@@ -257,10 +269,12 @@ class TimerEngine(
             if (remaining != _state.value.remaining) {
                 _state.value = _state.value.copy(remaining = remaining)
             }
-            if (remaining == 0 && _state.value.isActive && !current.paused && !completing) {
+            if (remaining == 0 && _state.value.isActive && !current.paused &&
+                completedId != current.sessionId
+            ) {
                 // The countdown has run out. The server books the interval and its
                 // reply decides what follows — an auto-started break, or nothing.
-                completing = true
+                completedId = current.sessionId
                 complete()
             }
         }
@@ -369,7 +383,6 @@ class TimerEngine(
         val current = server.current
         if (current == null) {
             anchor = null
-            completing = false
         } else {
             val changed = anchor?.sessionId != current.id ||
                 anchor?.paused != current.isPaused ||
@@ -386,7 +399,6 @@ class TimerEngine(
                     paused = current.isPaused,
                 )
             }
-            if (current.id != _state.value.sessionId) completing = false
         }
 
         _state.value = _state.value.copy(
@@ -467,12 +479,15 @@ class TimerEngine(
             _state.value = before.ended()
             anchor = null
             enqueue({ box, ui -> box.add(OutboxOp.COMPLETE, ui.sessionId) }, before)
-            completing = false
             return@launch
         }
+        // Naming the interval is what makes this safe to send at all: by the time it
+        // arrives, another client's countdown may already have finished it and started
+        // the next one, and an unconditional complete would end *that* instead.
+        val expected = before.sessionId?.takeIf { it != LOCAL_SESSION_ID }
         mutex.withLock {
             _state.value = _state.value.copy(busy = true)
-            when (val result = repo.complete(autoNext)) {
+            when (val result = repo.complete(autoNext, expected)) {
                 is ApiResult.Ok -> {
                     val dto = result.value
                     applyServer(dto, fromCommand = true)
@@ -493,10 +508,14 @@ class TimerEngine(
                     anchor = null
                     enqueue({ box, ui -> box.add(OutboxOp.COMPLETE, ui.sessionId) }, before)
                 }
-                else -> handleFailure(result)
+                else -> {
+                    // Nothing was booked, so the interval sitting at 00:00 is still
+                    // owed a complete; let the next tick try again.
+                    if (completedId == before.sessionId) completedId = null
+                    handleFailure(result)
+                }
             }
             _state.value = _state.value.copy(busy = false)
-            completing = false
         }
     }
 
@@ -704,7 +723,10 @@ class TimerEngine(
         )
         OutboxOp.PAUSE -> repo.pause()
         OutboxOp.RESUME -> repo.resume()
-        OutboxOp.COMPLETE -> repo.complete(autoNext = false)
+        OutboxOp.COMPLETE -> repo.complete(
+            autoNext = false,
+            sessionId = entry.anchorSessionId?.takeIf { it != LOCAL_SESSION_ID },
+        )
         OutboxOp.ABANDON -> repo.abandon(entry.reason)
         OutboxOp.EXTEND -> repo.extend(entry.minutes)
         OutboxOp.INTERRUPT -> repo.interrupt()

android/app/src/main/kotlin/tech/kadence/android/ui/KadenceApp.kt

@@ -69,6 +69,12 @@ fun KadenceApp(app: KadenceApplication) {
     val updateState by app.updates.state.collectAsStateWithLifecycle()
 
     var showOnboarding by remember { mutableStateOf(!config.onboarded) }
+    // How the Tasks screen was last left. Held here and written straight back to
+    // prefs rather than kept in `KadenceConfig`, so a filter checkbox does not
+    // push the config StateFlow and recompose every screen in the app.
+    var tasksCalendarView by remember { mutableStateOf(app.prefs.tasksCalendarView) }
+    var tasksShowLong by remember { mutableStateOf(app.prefs.tasksShowLong) }
+    var tasksHiddenKeys by remember { mutableStateOf(app.prefs.tasksHiddenKeys) }
     var showUpdateDialog by remember { mutableStateOf(false) }
     var destination by remember { mutableStateOf(Destination.Timer) }
     val scope = rememberCoroutineScope()
@@ -157,6 +163,21 @@ fun KadenceApp(app: KadenceApplication) {
                         cache = app.store.slot(Cached.TASKS, TaskListDto.serializer()),
                         runningTaskTitle = ui.taskTitle,
                         intervalRunning = ui.isActive,
+                        calendarView = tasksCalendarView,
+                        onSetCalendarView = { next ->
+                            tasksCalendarView = next
+                            app.prefs.tasksCalendarView = next
+                        },
+                        showLong = tasksShowLong,
+                        onSetShowLong = { next ->
+                            tasksShowLong = next
+                            app.prefs.tasksShowLong = next
+                        },
+                        hiddenKeys = tasksHiddenKeys,
+                        onSetHiddenKeys = { next ->
+                            tasksHiddenKeys = next
+                            app.prefs.tasksHiddenKeys = next
+                        },
                         onAttach = { taskId ->
                             // `attach` needs something to attach to: with nothing
                             // running the server answers "No interval is running."

android/app/src/main/kotlin/tech/kadence/android/ui/calendar/FilterPanel.kt

@@ -0,0 +1,132 @@
+/**
+ * Hide whole categories of work: a source, or one project inside it.
+ *
+ * The set it edits holds **hidden** keys, never visible ones, so a Jira project
+ * that first appears after a refresh shows up rather than being filtered out by a
+ * set written last week. See `isHidden` in `:core`'s `Calendar.kt`.
+ *
+ * Switching a source off disables its projects rather than silently unticking
+ * them: the parent governs, and switching it back on restores the whole subtree
+ * instead of leaving ghosts from whatever was unticked before.
+ *
+ * `ToggleRow` from the shared primitives is deliberately not used here — its
+ * explanatory `detail` line is mandatory by design, and twenty Jira projects would
+ * each demand a sentence nobody wants to read.
+ */
+package tech.kadence.android.ui.calendar
+
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.material3.Checkbox
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.style.TextOverflow
+import androidx.compose.ui.unit.dp
+import tech.kadence.android.ui.components.HorizontalRule
+import tech.kadence.android.ui.theme.KadenceTheme
+import tech.kadence.core.CalendarItem
+import tech.kadence.core.buildFilterTree
+
+@Composable
+fun FilterPanel(
+    /** The *unfiltered* list — the counts have to describe what is there. */
+    items: List<CalendarItem>,
+    hidden: Set<String>,
+    onChange: (Set<String>) -> Unit,
+    modifier: Modifier = Modifier,
+) {
+    val colors = KadenceTheme.colors
+    val tree = buildFilterTree(items)
+
+    Column(modifier.fillMaxWidth()) {
+        if (tree.isEmpty()) {
+            Text(
+                text = "Nothing to filter yet.",
+                style = KadenceTheme.type.bodySmall,
+                color = colors.inkMuted,
+                modifier = Modifier.padding(14.dp),
+            )
+            return@Column
+        }
+
+        tree.forEachIndexed { index, node ->
+            if (index > 0) HorizontalRule()
+            val sourceHidden = node.key in hidden
+            FilterRow(
+                label = node.label,
+                count = node.count,
+                checked = !sourceHidden,
+                bold = true,
+                onChange = { visible ->
+                    val next = hidden.toMutableSet()
+                    if (visible) {
+                        // Turning a source back on restores its projects with it.
+                        next.remove(node.key)
+                        node.children.forEach { next.remove(it.key) }
+                    } else {
+                        next.add(node.key)
+                    }
+                    onChange(next)
+                },
+            )
+            node.children.forEach { child ->
+                FilterRow(
+                    label = child.label,
+                    count = child.count,
+                    checked = !sourceHidden && child.key !in hidden,
+                    enabled = !sourceHidden,
+                    indent = true,
+                    onChange = { visible ->
+                        val next = hidden.toMutableSet()
+                        if (visible) next.remove(child.key) else next.add(child.key)
+                        onChange(next)
+                    },
+                )
+            }
+        }
+    }
+}
+
+@Composable
+private fun FilterRow(
+    label: String,
+    count: Int,
+    checked: Boolean,
+    onChange: (Boolean) -> Unit,
+    bold: Boolean = false,
+    indent: Boolean = false,
+    enabled: Boolean = true,
+) {
+    val colors = KadenceTheme.colors
+    Row(
+        Modifier
+            .fillMaxWidth()
+            .clickable(enabled = enabled) { onChange(!checked) }
+            .padding(start = if (indent) 32.dp else 8.dp, end = 14.dp, top = 2.dp, bottom = 2.dp),
+        verticalAlignment = Alignment.CenterVertically,
+        horizontalArrangement = Arrangement.spacedBy(8.dp),
+    ) {
+        Checkbox(checked = checked, onCheckedChange = onChange, enabled = enabled)
+        Text(
+            text = label,
+            style = KadenceTheme.type.body,
+            fontWeight = if (bold) FontWeight.SemiBold else null,
+            color = if (enabled) colors.ink else colors.inkFaint,
+            maxLines = 1,
+            overflow = TextOverflow.Ellipsis,
+            modifier = Modifier.weight(1f),
+        )
+        Text(
+            text = "$count",
+            style = KadenceTheme.type.caption,
+            color = colors.inkFaint,
+        )
+    }
+}

android/app/src/main/kotlin/tech/kadence/android/ui/calendar/MonthGrid.kt

@@ -0,0 +1,258 @@
+/**
+ * The month, as bars from start date to deadline.
+ *
+ * Built like a printed table rather than a grid of cards: a hairline between the
+ * cells, tabular day figures, and exactly one accent — today.
+ *
+ * Bars are coloured by **state, not by source**. Five saturated fills across a
+ * month grid would read as Material rather than Kadence, and five categorical
+ * hues cannot clear the data-viz palette validator's all-pairs normal-vision
+ * floor anyway. Identity comes from the title and from the filter; colour is kept
+ * for what changes how you act on a task — done, overdue, or still waiting.
+ *
+ * A lane is a `Row` of weighted cells rather than an absolutely positioned strip:
+ * the bars are already clipped to the week by `layoutMonth`, so a bar is simply a
+ * cell of `weight(span)` with `Spacer`s either side. No offset arithmetic, and it
+ * reflows for free at any width.
+ */
+package tech.kadence.android.ui.calendar
+
+import androidx.compose.foundation.background
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.fillMaxHeight
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.heightIn
+import androidx.compose.foundation.layout.width
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.shape.RoundedCornerShape
+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.Color
+import androidx.compose.ui.text.style.TextAlign
+import androidx.compose.ui.text.style.TextDecoration
+import androidx.compose.ui.text.style.TextOverflow
+import androidx.compose.ui.unit.dp
+import tech.kadence.android.data.dto.TaskDto
+import tech.kadence.android.ui.components.HorizontalRule
+import tech.kadence.android.ui.theme.KadenceTheme
+import tech.kadence.core.WeekLayout
+import tech.kadence.core.weekdayLabels
+
+private val BAR_HEIGHT = 18.dp
+private val BAR_GAP = 3.dp
+private val ROW_MIN = 74.dp
+
+@Composable
+fun MonthGrid(
+    weeks: List<WeekLayout>,
+    /** 1-12 — days outside it are drawn faint. */
+    month: Int,
+    today: String,
+    tasksById: Map<Long, TaskDto>,
+    selectedDay: String?,
+    weekStartsMonday: Boolean,
+    onSelectDay: (String) -> Unit,
+    modifier: Modifier = Modifier,
+) {
+    val colors = KadenceTheme.colors
+    Column(modifier.fillMaxWidth()) {
+        Row(
+            Modifier
+                .fillMaxWidth()
+                .background(colors.surfaceSunken)
+                .padding(vertical = 5.dp),
+        ) {
+            weekdayLabels(weekStartsMonday).forEach { name ->
+                Text(
+                    text = name.take(2),
+                    style = KadenceTheme.type.caption,
+                    color = colors.inkMuted,
+                    textAlign = TextAlign.Center,
+                    modifier = Modifier.weight(1f),
+                )
+            }
+        }
+        HorizontalRule()
+
+        weeks.forEachIndexed { index, week ->
+            if (index > 0) HorizontalRule()
+            WeekRow(
+                week = week,
+                month = month,
+                today = today,
+                tasksById = tasksById,
+                selectedDay = selectedDay,
+                onSelectDay = onSelectDay,
+            )
+        }
+    }
+}
+
+@Composable
+private fun WeekRow(
+    week: WeekLayout,
+    month: Int,
+    today: String,
+    tasksById: Map<Long, TaskDto>,
+    selectedDay: String?,
+    onSelectDay: (String) -> Unit,
+) {
+    val colors = KadenceTheme.colors
+
+    Box(Modifier.fillMaxWidth().heightIn(min = ROW_MIN)) {
+        // The cells themselves: the tap targets and the selection tint, behind
+        // everything. The bars drawn over them carry no pointer modifiers, so
+        // they never swallow a tap meant for the day.
+        Row(Modifier.matchParentSize()) {
+            week.dates.forEach { date ->
+                Box(
+                    Modifier
+                        .weight(1f)
+                        .fillMaxHeight()
+                        .background(if (date == selectedDay) colors.accentSoft else Color.Transparent)
+                        .clickable { onSelectDay(date) },
+                )
+            }
+        }
+
+        Column(Modifier.fillMaxWidth().padding(bottom = 4.dp)) {
+            Row(Modifier.fillMaxWidth().padding(vertical = 3.dp)) {
+                week.dates.forEach { date ->
+                    val outside = date.substring(5, 7).toInt() != month
+                    Text(
+                        text = date.substring(8, 10).trimStart('0'),
+                        style = KadenceTheme.type.caption,
+                        color = when {
+                            date == today -> colors.accent
+                            outside -> colors.inkFaint
+                            else -> colors.inkMuted
+                        },
+                        textAlign = TextAlign.Center,
+                        modifier = Modifier.weight(1f),
+                    )
+                }
+            }
+
+            repeat(week.lanes) { lane ->
+                Row(Modifier.fillMaxWidth().height(BAR_HEIGHT)) {
+                    var column = 0
+                    week.bars
+                        .filter { it.lane == lane }
+                        .sortedBy { it.startCol }
+                        .forEach { bar ->
+                            if (bar.startCol > column) {
+                                Spacer(Modifier.weight((bar.startCol - column).toFloat()))
+                            }
+                            val task = tasksById[bar.id]
+                            val span = (bar.endCol - bar.startCol + 1).toFloat()
+                            if (task == null) {
+                                Spacer(Modifier.weight(span))
+                            } else {
+                                TaskBar(
+                                    task = task,
+                                    today = today,
+                                    continuesLeft = bar.continuesLeft,
+                                    continuesRight = bar.continuesRight,
+                                    modifier = Modifier.weight(span),
+                                )
+                            }
+                            column = bar.endCol + 1
+                        }
+                    if (column < 7) Spacer(Modifier.weight((7 - column).toFloat()))
+                }
+                Spacer(Modifier.height(BAR_GAP))
+            }
+
+            if (week.hasOverflow) {
+                Row(Modifier.fillMaxWidth()) {
+                    week.overflow.forEach { count ->
+                        Text(
+                            text = if (count > 0) "+$count" else "",
+                            style = KadenceTheme.type.caption,
+                            color = colors.inkMuted,
+                            textAlign = TextAlign.Center,
+                            modifier = Modifier.weight(1f),
+                        )
+                    }
+                }
+            }
+        }
+    }
+}
+
+/**
+ * One bar.
+ *
+ * `daysOverdue` and `bucket` are computed by the backend against *today*, so a
+ * stale laundry slot from March claims to be two hundred days overdue forever.
+ * Neither is used here: lateness is decided from the task's own due date, and only
+ * for something still open and still offered by its source.
+ */
+@Composable
+private fun TaskBar(
+    task: TaskDto,
+    today: String,
+    continuesLeft: Boolean,
+    continuesRight: Boolean,
+    modifier: Modifier = Modifier,
+) {
+    val colors = KadenceTheme.colors
+    val late = !task.isDone && !task.stale && (task.dueDate?.let { it < today } == true)
+    val muted = task.isDone || task.stale
+    val square = 0.dp
+    val round = 4.dp
+
+    Box(
+        modifier
+            .fillMaxHeight()
+            .padding(horizontal = 1.dp)
+            .clip(
+                RoundedCornerShape(
+                    topStart = if (continuesLeft) square else round,
+                    bottomStart = if (continuesLeft) square else round,
+                    topEnd = if (continuesRight) square else round,
+                    bottomEnd = if (continuesRight) square else round,
+                ),
+            )
+            .background(colors.surfaceSunken),
+        contentAlignment = Alignment.CenterStart,
+    ) {
+        Row(
+            Modifier.fillMaxSize().padding(horizontal = 4.dp),
+            verticalAlignment = Alignment.CenterVertically,
+            horizontalArrangement = Arrangement.spacedBy(4.dp),
+        ) {
+            if (!continuesLeft) {
+                Box(
+                    Modifier
+                        .width(2.dp)
+                        .fillMaxHeight(0.6f)
+                        .clip(RoundedCornerShape(1.dp))
+                        .background(if (late) colors.clay else if (muted) colors.inkFaint else colors.inkMuted),
+                )
+            }
+            Text(
+                text = task.title,
+                style = KadenceTheme.type.caption,
+                color = when {
+                    muted -> colors.inkFaint
+                    late -> colors.clay
+                    else -> colors.ink
+                },
+                textDecoration = if (task.isDone) TextDecoration.LineThrough else null,
+                maxLines = 1,
+                overflow = TextOverflow.Ellipsis,
+            )
+        }
+    }
+}

android/app/src/main/kotlin/tech/kadence/android/ui/tasks/TaskRow.kt

@@ -0,0 +1,134 @@
+/**
+ * One task, as a row.
+ *
+ * Moved out of `TasksScreen.kt` unchanged when that screen grew a calendar beside
+ * the list: the calendar's day detail renders the same row, so a task reads
+ * identically wherever you meet it.
+ *
+ * Read-only, and that is the product decision rather than a shortcut: tapping it
+ * **opens the task where it lives**, which is where closing it happens; "Track"
+ * attaches it to the running interval, which is the one thing that belongs to
+ * Kadence.
+ */
+package tech.kadence.android.ui.tasks
+
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Arrangement
+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.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
+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.text.style.TextDecoration
+import androidx.compose.ui.text.style.TextOverflow
+import androidx.compose.ui.unit.dp
+import tech.kadence.android.data.dto.TaskDto
+import tech.kadence.android.ui.components.Eyebrow
+import tech.kadence.android.ui.theme.KadenceTheme
+import tech.kadence.core.dueLabel
+
+@Composable
+internal fun TaskRow(
+    task: TaskDto,
+    isRunning: Boolean,
+    anyIntervalRunning: Boolean,
+    onOpen: () -> Unit,
+    onTrack: () -> Unit,
+) {
+    val colors = KadenceTheme.colors
+    val due = dueLabel(task.dueDate, task.daysOverdue)
+    val linkable = !task.url.isNullOrBlank()
+
+    Row(
+        Modifier
+            .fillMaxWidth()
+            // A local task has no URL and nothing to open; making it look tappable
+            // and then doing nothing is worse than it being plainly inert.
+            .then(if (linkable) Modifier.clickable(onClick = onOpen) else Modifier)
+            .padding(start = 14.dp, end = 4.dp, top = 12.dp, bottom = 12.dp),
+        verticalAlignment = Alignment.CenterVertically,
+        horizontalArrangement = Arrangement.spacedBy(10.dp),
+    ) {
+        Column(Modifier.weight(1f)) {
+            Text(
+                text = task.title,
+                style = KadenceTheme.type.body,
+                color = if (task.stale || task.isDone) colors.inkMuted else colors.ink,
+                textDecoration = if (task.isDone) TextDecoration.LineThrough else null,
+                maxLines = 2,
+                overflow = TextOverflow.Ellipsis,
+            )
+            Spacer(Modifier.height(2.dp))
+            Row(horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+                Eyebrow(task.sourceLabel.ifBlank { task.source })
+                if (due.isNotBlank()) {
+                    Text(
+                        text = due,
+                        style = KadenceTheme.type.caption,
+                        // Overdue is the one case worth colouring; everything else is
+                        // a date and a date is not an alarm. `daysOverdue` is computed
+                        // against *today*, so it only means anything for something
+                        // still open — a stale laundry slot carries one forever.
+                        color = if (task.daysOverdue > 0 && !task.isDone && !task.stale) {
+                            colors.clay
+                        } else {
+                            colors.inkFaint
+                        },
+                    )
+                }
+                task.project?.takeIf { it.isNotBlank() }?.let { project ->
+                    Text(
+                        text = project,
+                        style = KadenceTheme.type.caption,
+                        color = colors.inkFaint,
+                        maxLines = 1,
+                        overflow = TextOverflow.Ellipsis,
+                    )
+                }
+            }
+        }
+        if (isRunning) {
+            Text(
+                text = "running",
+                style = KadenceTheme.type.caption,
+                color = colors.accent,
+                modifier = Modifier.padding(end = 10.dp),
+            )
+        } else {
+            TextButton(onClick = onTrack, contentPadding = PaddingValues(horizontal = 10.dp)) {
+                // "Focus" when the tap will begin an interval on this task, "Track"
+                // when it only re-points the one already running.
+                Text(
+                    text = if (anyIntervalRunning) "Track" else "Focus",
+                    style = KadenceTheme.type.button,
+                    color = colors.accent,
+                )
+            }
+        }
+    }
+}
+
+/**
+ * Open the task in whatever app or browser owns it.
+ *
+ * `url` is absent for local tasks, and for a source that did not supply one; the row
+ * is not clickable in that case, so this is only ever reached with something to open.
+ * Still guarded, because an unparseable URL from a third-party API must not crash the
+ * list.
+ */
+internal fun openTask(context: android.content.Context, task: TaskDto) {
+    val url = task.url?.takeIf { it.isNotBlank() } ?: return
+    val intent = android.content.Intent(
+        android.content.Intent.ACTION_VIEW,
+        android.net.Uri.parse(url),
+    ).addFlags(android.content.Intent.FLAG_ACTIVITY_NEW_TASK)
+    runCatching { context.startActivity(intent) }
+        .onFailure { android.util.Log.w("Kadence", "cannot open $url: ${it.message}") }
+}

android/app/src/main/kotlin/tech/kadence/android/ui/tasks/TasksScreen.kt

@@ -1,85 +1,119 @@
 /**
- * Every todo you own, grouped the way the other clients group them.
+ * Every todo you own — as a list, or as a month.
  *
- * Read-only, and that is the product decision rather than a shortcut: **you cannot tick
- * a task off here.** Completion belongs to the tool the task lives in — close it in
- * Jira, Todoist or Google Tasks and the next refresh notices. Two places to mark
- * something done is two places to be wrong.
+ * Read-only, and that is the product decision rather than a shortcut: **you cannot
+ * tick a task off here.** Completion belongs to the tool the task lives in — close
+ * it in Jira, Todoist or Google Tasks and the next refresh notices. Two places to
+ * mark something done is two places to be wrong.
  *
- * So a row has exactly two actions and they follow from that. Tapping it **opens the
- * task where it lives**, which is where closing it happens; "Track" attaches it to the
- * running interval, which is the one thing that belongs to Kadence. A task with no
- * `url` — a local one, or a source that supplied none — is simply not tappable rather
- * than tappable-and-inert.
+ * The screen asks the backend for **done and stale rows too**, because a past
+ * month is only worth looking at if the work that finished is on it, and laundry
+ * slots go `stale` rather than done. The list therefore filters those out itself
+ * rather than trusting the URL the payload came from — which also means the single
+ * `Cached.TASKS` slot stays correct whichever view wrote it last.
  *
- * Bucket order and labels come from `:core`'s `BUCKET_ORDER` / `BUCKET_LABEL`, so the
- * phone cannot drift from the web app's wording — including the deliberate choice of
- * "Would be nice to start" over the desktop's "In progress".
+ * Bucket order and labels come from `:core`, and so does the whole calendar
+ * layout, so the phone cannot drift from the web app.
+ *
+ * One Compose constraint worth not re-learning: this is a single `LazyColumn`, and
+ * both bodies contribute `item`s to *it*. The month grid is a plain `Column` of
+ * `Row`s inside one item — never a nested `LazyVerticalGrid`, which throws on
+ * same-axis nested scrolling.
  */
 package tech.kadence.android.ui.tasks
 
-import androidx.compose.foundation.clickable
 import androidx.compose.foundation.layout.Arrangement
-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.PaddingValues
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
-import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.lazy.LazyColumn
-import androidx.compose.foundation.lazy.items
+import androidx.compose.foundation.lazy.LazyListScope
 import androidx.compose.material3.CircularProgressIndicator
 import androidx.compose.material3.Text
-import androidx.compose.material3.TextButton
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
 import androidx.compose.runtime.rememberCoroutineScope
+import androidx.compose.runtime.saveable.rememberSaveable
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.platform.LocalContext
-import androidx.compose.ui.text.style.TextOverflow
 import androidx.compose.ui.unit.dp
 import kotlinx.coroutines.launch
 import tech.kadence.android.data.KadenceRepository
 import tech.kadence.android.data.dto.TaskDto
+import tech.kadence.android.data.dto.TaskListDto
 import tech.kadence.android.data.net.ApiResult
+import tech.kadence.android.data.store.CacheSlot
 import tech.kadence.android.ui.Loadable
+import tech.kadence.android.ui.calendar.FilterPanel
+import tech.kadence.android.ui.calendar.MonthGrid
 import tech.kadence.android.ui.components.Banner
-import tech.kadence.android.ui.components.Eyebrow
 import tech.kadence.android.ui.components.GhostButton
 import tech.kadence.android.ui.components.HorizontalRule
 import tech.kadence.android.ui.components.PageHeader
 import tech.kadence.android.ui.components.Panel
+import tech.kadence.android.ui.components.PresetChip
 import tech.kadence.android.ui.components.SectionTitle
-import tech.kadence.android.data.store.CacheSlot
 import tech.kadence.android.ui.rememberLoad
 import tech.kadence.android.ui.theme.KadenceTheme
 import tech.kadence.core.BUCKET_LABEL
 import tech.kadence.core.BUCKET_ORDER
-import tech.kadence.core.dueLabel
+import tech.kadence.core.buildModel
+import tech.kadence.core.itemsOnDay
+import tech.kadence.core.layoutMonth
+import tech.kadence.core.monthGrid
+import tech.kadence.core.shiftMonth
+import tech.kadence.core.todayISO
+import java.time.LocalDate
+import java.time.YearMonth
+import java.time.format.DateTimeFormatter
+
+/**
+ * Monday-first, hardcoded on both clients for now.
+ *
+ * `week_starts_monday` is in the settings document, but `AppSettingsDto` does not
+ * carry it and this screen loads no settings — so honouring it on the web alone is
+ * how the two clients start disagreeing about what a week is. The backend default
+ * is Monday anyway.
+ */
+private const val WEEK_STARTS_MONDAY = true
 
 @Composable
 fun TasksScreen(
     repo: KadenceRepository,
     /** Yesterday's list, so a phone with no signal is not an empty screen. */
-    cache: CacheSlot<tech.kadence.android.data.dto.TaskListDto>? = null,
+    cache: CacheSlot<TaskListDto>? = null,
     runningTaskTitle: String?,
     /** An interval is running — with or without a task attached to it. */
     intervalRunning: Boolean,
+    calendarView: Boolean,
+    onSetCalendarView: (Boolean) -> Unit,
+    showLong: Boolean,
+    onSetShowLong: (Boolean) -> Unit,
+    hiddenKeys: Set<String>,
+    onSetHiddenKeys: (Set<String>) -> Unit,
     onAttach: (Long) -> Unit,
 ) {
     val colors = KadenceTheme.colors
     val context = LocalContext.current
     val scope = rememberCoroutineScope()
-    val loader = rememberLoad(cache = cache) { repo.tasks() }
+    val loader = rememberLoad(cache = cache) {
+        repo.tasks(includeDone = true, includeStale = true)
+    }
     var refreshing by remember { mutableStateOf(false) }
     var refreshNote by remember { mutableStateOf<String?>(null) }
 
+    val today = remember { todayISO() }
+    var cursorYear by rememberSaveable { mutableStateOf(LocalDate.now().year) }
+    var cursorMonth by rememberSaveable { mutableStateOf(LocalDate.now().monthValue) }
+    var selectedDay by rememberSaveable { mutableStateOf<String?>(null) }
+    var filterOpen by rememberSaveable { mutableStateOf(false) }
+
     fun refresh() {
         refreshing = true
         refreshNote = null
@@ -106,23 +140,21 @@ fun TasksScreen(
     }
 
     val state = loader.value
+    val all = (state as? Loadable.Loaded)?.value?.tasks.orEmpty()
+    // Always, regardless of which URL answered: that is what keeps one cache slot
+    // correct for two views.
+    val open = all.filter { !it.isDone && !it.stale }
 
     LazyColumn(
         Modifier.fillMaxSize(),
-        contentPadding = PaddingValues(
-            start = 20.dp,
-            end = 20.dp,
-            top = 24.dp,
-            bottom = 32.dp,
-        ),
+        contentPadding = PaddingValues(start = 20.dp, end = 20.dp, top = 24.dp, bottom = 32.dp),
         verticalArrangement = Arrangement.spacedBy(16.dp),
     ) {
         item {
-            val total = (state as? Loadable.Loaded)?.value?.tasks?.size
             PageHeader(
                 eyebrow = "Everything open",
                 title = "Tasks",
-                caption = total?.let { "$it across your sources" },
+                caption = if (state is Loadable.Loaded) "${open.size} across your sources" else null,
             ) {
                 GhostButton(
                     text = if (refreshing) "Refreshing…" else "Refresh sources",
@@ -132,6 +164,13 @@ fun TasksScreen(
             }
         }
 
+        item {
+            Row(horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+                PresetChip(text = "List", selected = !calendarView, onClick = { onSetCalendarView(false) })
+                PresetChip(text = "Calendar", selected = calendarView, onClick = { onSetCalendarView(true) })
+            }
+        }
+
         refreshNote?.let { note ->
             item { Banner(text = note, actionLabel = "Retry", onAction = ::refresh) }
         }
@@ -155,148 +194,239 @@ fun TasksScreen(
                     item { Banner(text = stale, actionLabel = "Retry", onAction = loader::reload) }
                 }
 
-                val byBucket = state.value.tasks.groupBy { it.bucket }
-                // BUCKET_ORDER first, then anything the backend invented later — an
-                // unknown bucket must still be visible rather than silently dropped.
-                val buckets = BUCKET_ORDER.filter { byBucket.containsKey(it) } +
-                    byBucket.keys.filterNot { it in BUCKET_ORDER }.sorted()
-
-                if (state.value.tasks.isEmpty()) {
-                    item {
-                        Panel {
-                            Text(
-                                text = "Nothing open. Either you are done, or no source " +
-                                    "is configured yet — the backend's Settings page " +
-                                    "is where they go.",
-                                style = KadenceTheme.type.bodySmall,
-                                color = colors.inkMuted,
-                            )
-                        }
-                    }
-                }
-
-                buckets.forEach { bucket ->
-                    val tasks = byBucket[bucket].orEmpty()
-                    item(key = "head-$bucket") {
-                        SectionTitle(
-                            label = BUCKET_LABEL[bucket] ?: bucket,
-                            trailing = "${tasks.size}",
-                        )
-                    }
-                    item(key = "body-$bucket") {
-                        Panel(padding = 0.dp) {
-                            tasks.forEachIndexed { index, task ->
-                                if (index > 0) HorizontalRule()
-                                TaskRow(
-                                    task = task,
-                                    isRunning = task.title == runningTaskTitle,
-                                    anyIntervalRunning = intervalRunning,
-                                    // Tapping the row opens the task where it lives —
-                                    // Jira, Todoist, Google Tasks. That is where it
-                                    // gets *closed*, and this app deliberately cannot
-                                    // close it, so sending you there is the whole of
-                                    // what a tap should do.
-                                    onOpen = { openTask(context, task) },
-                                    // Attaching is the separate, explicit action.
-                                    onTrack = { onAttach(task.id) },
-                                )
-                            }
-                        }
-                    }
+                if (calendarView) {
+                    calendarBody(
+                        all = all,
+                        hiddenKeys = hiddenKeys,
+                        onSetHiddenKeys = onSetHiddenKeys,
+                        showLong = showLong,
+                        onSetShowLong = onSetShowLong,
+                        today = today,
+                        year = cursorYear,
+                        month = cursorMonth,
+                        onShiftMonth = { delta ->
+                            val (y, m) = shiftMonth(cursorYear, cursorMonth, delta)
+                            cursorYear = y
+                            cursorMonth = m
+                            selectedDay = null
+                        },
+                        onToday = {
+                            cursorYear = LocalDate.now().year
+                            cursorMonth = LocalDate.now().monthValue
+                            selectedDay = null
+                        },
+                        selectedDay = selectedDay,
+                        onSelectDay = { selectedDay = if (it == selectedDay) null else it },
+                        filterOpen = filterOpen,
+                        onToggleFilter = { filterOpen = !filterOpen },
+                        runningTaskTitle = runningTaskTitle,
+                        intervalRunning = intervalRunning,
+                        onOpenTask = { openTask(context, it) },
+                        onAttach = onAttach,
+                    )
+                } else {
+                    listBody(
+                        tasks = open,
+                        runningTaskTitle = runningTaskTitle,
+                        intervalRunning = intervalRunning,
+                        onOpenTask = { openTask(context, it) },
+                        onAttach = onAttach,
+                    )
                 }
             }
         }
     }
 }
 
-@Composable
-private fun TaskRow(
-    task: TaskDto,
-    isRunning: Boolean,
-    anyIntervalRunning: Boolean,
-    onOpen: () -> Unit,
-    onTrack: () -> Unit,
+/** The original view: grouped by deadline bucket. */
+private fun LazyListScope.listBody(
+    tasks: List<TaskDto>,
+    runningTaskTitle: String?,
+    intervalRunning: Boolean,
+    onOpenTask: (TaskDto) -> Unit,
+    onAttach: (Long) -> Unit,
 ) {
-    val colors = KadenceTheme.colors
-    val due = dueLabel(task.dueDate, task.daysOverdue)
-    val linkable = !task.url.isNullOrBlank()
+    val byBucket = tasks.groupBy { it.bucket }
+    // BUCKET_ORDER first, then anything the backend invented later — an unknown
+    // bucket must still be visible rather than silently dropped.
+    val buckets = BUCKET_ORDER.filter { byBucket.containsKey(it) } +
+        byBucket.keys.filterNot { it in BUCKET_ORDER }.sorted()
 
-    Row(
-        Modifier
-            .fillMaxWidth()
-            // A local task has no URL and nothing to open; making it look tappable
-            // and then doing nothing is worse than it being plainly inert.
-            .then(if (linkable) Modifier.clickable(onClick = onOpen) else Modifier)
-            .padding(start = 14.dp, end = 4.dp, top = 12.dp, bottom = 12.dp),
-        verticalAlignment = Alignment.CenterVertically,
-        horizontalArrangement = Arrangement.spacedBy(10.dp),
-    ) {
-        Column(Modifier.weight(1f)) {
-            Text(
-                text = task.title,
-                style = KadenceTheme.type.body,
-                color = if (task.stale) colors.inkMuted else colors.ink,
-                maxLines = 2,
-                overflow = TextOverflow.Ellipsis,
-            )
-            Spacer(Modifier.height(2.dp))
-            Row(horizontalArrangement = Arrangement.spacedBy(8.dp)) {
-                Eyebrow(task.sourceLabel.ifBlank { task.source })
-                if (due.isNotBlank()) {
-                    Text(
-                        text = due,
-                        style = KadenceTheme.type.caption,
-                        // Overdue is the one case worth colouring; everything else is
-                        // a date and a date is not an alarm.
-                        color = if (task.daysOverdue > 0) colors.clay else colors.inkFaint,
-                    )
-                }
-                task.project?.takeIf { it.isNotBlank() }?.let { project ->
-                    Text(
-                        text = project,
-                        style = KadenceTheme.type.caption,
-                        color = colors.inkFaint,
-                        maxLines = 1,
-                        overflow = TextOverflow.Ellipsis,
-                    )
-                }
-            }
-        }
-        if (isRunning) {
-            Text(
-                text = "running",
-                style = KadenceTheme.type.caption,
-                color = colors.accent,
-                modifier = Modifier.padding(end = 10.dp),
-            )
-        } else {
-            TextButton(onClick = onTrack, contentPadding = PaddingValues(horizontal = 10.dp)) {
-                // "Focus" when the tap will begin an interval on this task, "Track"
-                // when it only re-points the one already running.
+    if (tasks.isEmpty()) {
+        item {
+            Panel {
                 Text(
-                    text = if (anyIntervalRunning) "Track" else "Focus",
-                    style = KadenceTheme.type.button,
-                    color = colors.accent,
+                    text = "Nothing open. Either you are done, or no source is " +
+                        "configured yet — the backend's Settings page is where they go.",
+                    style = KadenceTheme.type.bodySmall,
+                    color = KadenceTheme.colors.inkMuted,
                 )
             }
         }
     }
+
+    buckets.forEach { bucket ->
+        val inBucket = byBucket[bucket].orEmpty()
+        item(key = "head-$bucket") {
+            SectionTitle(label = BUCKET_LABEL[bucket] ?: bucket, trailing = "${inBucket.size}")
+        }
+        item(key = "body-$bucket") {
+            Panel(padding = 0.dp) {
+                inBucket.forEachIndexed { index, task ->
+                    if (index > 0) HorizontalRule()
+                    TaskRow(
+                        task = task,
+                        isRunning = task.title == runningTaskTitle,
+                        anyIntervalRunning = intervalRunning,
+                        onOpen = { onOpenTask(task) },
+                        onTrack = { onAttach(task.id) },
+                    )
+                }
+            }
+        }
+    }
 }
 
-/**
- * Open the task in whatever app or browser owns it.
- *
- * `url` is absent for local tasks, and for a source that did not supply one; the row
- * is not clickable in that case, so this is only ever reached with something to open.
- * Still guarded, because an unparseable URL from a third-party API must not crash the
- * list.
- */
-private fun openTask(context: android.content.Context, task: TaskDto) {
-    val url = task.url?.takeIf { it.isNotBlank() } ?: return
-    val intent = android.content.Intent(
-        android.content.Intent.ACTION_VIEW,
-        android.net.Uri.parse(url),
-    ).addFlags(android.content.Intent.FLAG_ACTIVITY_NEW_TASK)
-    runCatching { context.startActivity(intent) }
-        .onFailure { android.util.Log.w("Kadence", "cannot open $url: ${it.message}") }
+private val MONTH_LABEL = DateTimeFormatter.ofPattern("LLLL yyyy")
+
+private fun LazyListScope.calendarBody(
+    all: List<TaskDto>,
+    hiddenKeys: Set<String>,
+    onSetHiddenKeys: (Set<String>) -> Unit,
+    showLong: Boolean,
+    onSetShowLong: (Boolean) -> Unit,
+    today: String,
+    year: Int,
+    month: Int,
+    onShiftMonth: (Int) -> Unit,
+    onToday: () -> Unit,
+    selectedDay: String?,
+    onSelectDay: (String) -> Unit,
+    filterOpen: Boolean,
+    onToggleFilter: () -> Unit,
+    runningTaskTitle: String?,
+    intervalRunning: Boolean,
+    onOpenTask: (TaskDto) -> Unit,
+    onAttach: (Long) -> Unit,
+) {
+    val model = buildModel(all, hiddenKeys, showLong)
+    val weeks = monthGrid(year, month, WEEK_STARTS_MONDAY)
+    // Showing long bars needs the room they take, or they simply push the day's
+    // real work into "+N" and the month gets less informative, not more.
+    val layouts = layoutMonth(weeks, model.visible, maxLanes = if (showLong) 4 else 3)
+    val byId = model.visible.associateBy { it.id }
+
+    item(key = "cal-toolbar") {
+        Row(
+            Modifier.fillMaxWidth(),
+            verticalAlignment = Alignment.CenterVertically,
+            horizontalArrangement = Arrangement.spacedBy(6.dp),
+        ) {
+            GhostButton(text = "‹", onClick = { onShiftMonth(-1) })
+            Text(
+                text = YearMonth.of(year, month).format(MONTH_LABEL),
+                style = KadenceTheme.type.statSmall,
+                color = KadenceTheme.colors.ink,
+                modifier = Modifier.weight(1f),
+            )
+            GhostButton(text = "›", onClick = { onShiftMonth(1) })
+            GhostButton(text = "Today", onClick = onToday)
+        }
+    }
+
+    item(key = "cal-filters") {
+        Row(horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+            PresetChip(
+                text = if (hiddenKeys.isEmpty()) "Filter" else "Filter (${hiddenKeys.size})",
+                selected = filterOpen,
+                onClick = onToggleFilter,
+            )
+            PresetChip(
+                text = "Long tasks (${model.longCount})",
+                selected = showLong,
+                onClick = { onSetShowLong(!showLong) },
+            )
+        }
+    }
+
+    if (filterOpen) {
+        item(key = "cal-filter-panel") {
+            Panel(padding = 0.dp) {
+                FilterPanel(items = all, hidden = hiddenKeys, onChange = onSetHiddenKeys)
+            }
+        }
+    }
+
+    item(key = "cal-grid") {
+        Panel(padding = 0.dp) {
+            MonthGrid(
+                weeks = layouts,
+                month = month,
+                today = today,
+                tasksById = byId,
+                selectedDay = selectedDay,
+                weekStartsMonday = WEEK_STARTS_MONDAY,
+                onSelectDay = onSelectDay,
+            )
+        }
+    }
+
+    // The tapped day's work, under the grid. Items of the *outer* LazyColumn, not
+    // a nested lazy list.
+    selectedDay?.let { day ->
+        val onDay = itemsOnDay(model.visible, day)
+        item(key = "cal-day-head") {
+            SectionTitle(
+                label = LocalDate.parse(day).format(DAY_LABEL),
+                trailing = "${onDay.size}",
+            )
+        }
+        item(key = "cal-day-body") {
+            Panel(padding = 0.dp) {
+                if (onDay.isEmpty()) {
+                    Text(
+                        text = "Nothing on this day.",
+                        style = KadenceTheme.type.bodySmall,
+                        color = KadenceTheme.colors.inkMuted,
+                        modifier = Modifier.padding(14.dp),
+                    )
+                } else {
+                    onDay.forEachIndexed { index, task ->
+                        if (index > 0) HorizontalRule()
+                        TaskRow(
+                            task = task,
+                            isRunning = task.title == runningTaskTitle,
+                            anyIntervalRunning = intervalRunning,
+                            onOpen = { onOpenTask(task) },
+                            onTrack = { onAttach(task.id) },
+                        )
+                    }
+                }
+            }
+        }
+    }
+
+    // The tasks a calendar cannot place: no due date, so no column to sit in.
+    // Jira keeps the same affordance and calls it the backlog.
+    if (model.undated.isNotEmpty()) {
+        item(key = "cal-undated-head") {
+            SectionTitle(label = "No due date", trailing = "${model.undated.size}")
+        }
+        item(key = "cal-undated-body") {
+            Panel(padding = 0.dp) {
+                model.undated.forEachIndexed { index, task ->
+                    if (index > 0) HorizontalRule()
+                    TaskRow(
+                        task = task,
+                        isRunning = task.title == runningTaskTitle,
+                        anyIntervalRunning = intervalRunning,
+                        onOpen = { onOpenTask(task) },
+                        onTrack = { onAttach(task.id) },
+                    )
+                }
+            }
+        }
+    }
 }
+
+private val DAY_LABEL = DateTimeFormatter.ofPattern("EEEE, d MMMM")

android/app/src/test/kotlin/tech/kadence/android/TimerEngineTest.kt

@@ -79,6 +79,8 @@ class TimerEngineTest {
                     path.endsWith("/api/timer/pause") -> running(pauseReplyStatus, remaining = 900)
                     path.endsWith("/api/timer/resume") -> running("running")
                     path.endsWith("/api/timer/extend") -> running("running", 1404, 1800)
+                    path.endsWith("/api/timer/complete") ->
+                        fixture("timer_complete_reply.json")
                     else -> fixture("timer_state_running.json")
                 }
                 return MockResponse.Builder()
@@ -140,6 +142,30 @@ class TimerEngineTest {
         assertTrue(engine.state.value.interruptions >= 1)
     }
 
+    @Test
+    fun `complete names the interval it is finishing`() {
+        // Every client runs its own countdown, so they all reach zero together. An
+        // unconditional complete from the slowest of them lands on the break the
+        // fastest one's auto-start has just created and ends it on the spot — which
+        // is what made breaks look like they turned straight into focus. Naming the
+        // interval is what lets the server ignore the late call.
+        val engine = engine()
+
+        runBlocking { engine.complete().join() }
+
+        val sent = server.takeRequest().let { first ->
+            // The first recorded request is the fixture poll from `engine()`.
+            if (first.url.encodedPath.endsWith("/api/timer/complete")) first
+            else server.takeRequest()
+        }
+        assertEquals("/api/timer/complete", sent.url.encodedPath)
+        assertTrue(
+            sent.body?.utf8()?.contains("\"session_id\":412") == true,
+            "the complete must name interval 412, not just say 'finish whatever is running'",
+        )
+        assertEquals(413L, engine.state.value.sessionId, "the auto-started break is adopted")
+    }
+
     @Test
     fun `toggle reads the state it just changed`() {
         val engine = engine()

android/core/src/main/kotlin/tech/kadence/core/Calendar.kt

@@ -0,0 +1,401 @@
+/**
+ * The month grid, and the two filters that make it readable.
+ *
+ * A literal port of `frontend/src/lib/calendar.ts`, the same way `Format.kt` is a
+ * literal port of `format.ts`. `CalendarTest` asserts the outputs the TypeScript
+ * produces; `CalendarParityTest` reads `LONG_TASK_DAYS` and the exported names
+ * straight out of the web source and fails the build when the two drift.
+ *
+ * A calendar of *tasks* is not a calendar of events: nothing here has a time of
+ * day, only a start date and a due date, so every item is a whole-day bar and the
+ * only interesting layout question is which lane it sits in.
+ *
+ * Three rules exist because of what the sources actually return rather than for
+ * their own sake:
+ *
+ *  * **Long tasks are measured on their true span, before clipping.** Clipping to
+ *    the week first would make a fifteen-day bar look like seven days in each of
+ *    three rows, so it would never trip the filter — the entire point of it.
+ *  * **The filter stores hidden keys, never visible ones**, so a Jira project that
+ *    appears for the first time after a refresh shows up instead of being filtered
+ *    out by a set written last week.
+ *  * **A due date is what makes a task plottable** — see [spanOf].
+ *
+ * Nothing here may key off `bucket` or `days_overdue`: the backend computes both
+ * against *today*, so a stale laundry slot from March reports `overdue` with a
+ * `days_overdue` that grows forever. In a cell you are looking at in a past month
+ * that is noise — style from the cell's own date against `is_done`/`stale`.
+ */
+package tech.kadence.core
+
+import java.time.LocalDate
+import java.time.temporal.ChronoUnit
+
+/** Longer than this many days and a bar is "long". Mirrored in `calendar.ts`. */
+const val LONG_TASK_DAYS = 7
+
+/**
+ * What the layout needs off a task.
+ *
+ * An interface rather than a data class so `TaskDto` can simply be one, the way
+ * `KadenceConfig` is an `AuthConfig` — no mapping layer between the wire and the
+ * grid.
+ */
+interface CalendarItem {
+    val id: Long
+    val source: String
+    val sourceLabel: String
+    val project: String?
+    val startDate: String?
+    val dueDate: String?
+}
+
+/** Inclusive, so a one-day task is `days == 1`. */
+data class Span(val start: String, val end: String, val days: Int)
+
+// --------------------------------------------------------------------------
+// Dates
+// --------------------------------------------------------------------------
+// ISO day strings compare lexicographically in calendar order, so ordering and
+// overlap tests never need a date object at all. Only arithmetic does.
+
+/** Whole days from [from] to [to]. */
+fun diffDays(from: String, to: String): Int =
+    ChronoUnit.DAYS.between(LocalDate.parse(from), LocalDate.parse(to)).toInt()
+
+fun addDays(iso: String, days: Int): String = LocalDate.parse(iso).plusDays(days.toLong()).toString()
+
+fun todayISO(): String = LocalDate.now().toString()
+
+private fun span(start: String, end: String): Span = Span(start, end, diffDays(start, end) + 1)
+
+/**
+ * Where a task sits on the calendar, or null if it cannot be plotted.
+ *
+ * **A due date is what makes a task plottable.** A task with only a start date is
+ * deliberately *not* drawn, which is the one rule here that costs something and is
+ * worth the cost: the Jira JQL in `backend/app/sources/jira.py` selects issues
+ * whose start date is today-or-earlier with no lower bound, and Jira issues very
+ * often carry a start date and no due date. Drawing those on their start day puts
+ * work the user thinks of as "now" into a cell four months back — a confident
+ * wrong answer, which is worse than an honest absence. They come back as undated
+ * instead and get their own list.
+ *
+ * A due date *before* the start date is bad data — Jira permits it — and collapses
+ * to the deadline, because the deadline is the half that matters.
+ */
+fun spanOf(item: CalendarItem): Span? {
+    val due = item.dueDate?.takeIf { it.isNotBlank() } ?: return null
+    val start = item.startDate?.takeIf { it.isNotBlank() }
+    if (start == null || due < start) return span(due, due)
+    return span(start, due)
+}
+
+fun isLong(value: Span): Boolean = value.days > LONG_TASK_DAYS
+
+// --------------------------------------------------------------------------
+// The grid
+// --------------------------------------------------------------------------
+
+/**
+ * The weeks a month needs — four to six, never a fixed six.
+ *
+ * October 2026 starts on a Thursday and ends on a Saturday, so Monday-first it
+ * runs 28 September to 1 November in five rows. February 2027 begins on a Monday
+ * and needs only four. Padding either to six hangs an empty week off the bottom
+ * of the page, which reads as a bug.
+ *
+ * [month] is 1-12.
+ */
+fun monthGrid(year: Int, month: Int, weekStartsMonday: Boolean): List<List<String>> {
+    val first = LocalDate.of(year, month, 1)
+    // `DayOfWeek.value` is Monday=1..Sunday=7; the TypeScript's `getDay()` is
+    // Sunday=0..Saturday=6. This is that conversion, and it is the one line in
+    // the port where the two languages genuinely disagree.
+    val weekday = first.dayOfWeek.value % 7
+    val offset = if (weekStartsMonday) (weekday + 6) % 7 else weekday
+    val lastDay = first.lengthOfMonth()
+
+    val weeks = mutableListOf<List<String>>()
+    var cursor = 1 - offset
+    while (cursor <= lastDay) {
+        val row = (0 until 7).map { first.plusDays((cursor - 1 + it).toLong()).toString() }
+        weeks.add(row)
+        cursor += 7
+    }
+    return weeks
+}
+
+private val WEEKDAYS_FROM_MONDAY = listOf("Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun")
+
+fun weekdayLabels(weekStartsMonday: Boolean): List<String> =
+    if (weekStartsMonday) WEEKDAYS_FROM_MONDAY
+    else listOf(WEEKDAYS_FROM_MONDAY[6]) + WEEKDAYS_FROM_MONDAY.subList(0, 6)
+
+/** `shiftMonth(2026, 1, -1)` is December 2025. [month] is 1-12 throughout. */
+fun shiftMonth(year: Int, month: Int, delta: Int): Pair<Int, Int> {
+    val zero = year * 12 + (month - 1) + delta
+    return Pair(Math.floorDiv(zero, 12), Math.floorMod(zero, 12) + 1)
+}
+
+// --------------------------------------------------------------------------
+// Lane packing
+// --------------------------------------------------------------------------
+
+data class Bar(
+    val id: Long,
+    val lane: Int,
+    /** Inclusive column indices into the week, 0-6. */
+    val startCol: Int,
+    val endCol: Int,
+    /** The task began before this week / ends after it — square that edge off. */
+    val continuesLeft: Boolean,
+    val continuesRight: Boolean,
+)
+
+data class WeekLayout(
+    val dates: List<String>,
+    val bars: List<Bar>,
+    /** Per column, how many tasks this week could not draw — the "+N" counts. */
+    val overflow: List<Int>,
+    /** Lanes actually drawn, so a row can size itself to its content. */
+    val lanes: Int,
+    /** Whether any day in this week needs the "+N" strip under the bars. */
+    val hasOverflow: Boolean,
+)
+
+private class Placed(val item: CalendarItem, val span: Span)
+
+/**
+ * Lay out a whole month, keeping a multi-week bar in one lane throughout.
+ *
+ * This has to be a month-at-a-time function rather than a week-at-a-time one,
+ * because the lane a continuing bar occupies is information that flows from one
+ * week to the next. Packing each week independently — however the segments are
+ * sorted — lets a bar step between lanes halfway along. With A spanning 2 to 18
+ * March and B spanning 9 March to 2 April, A owns lane 0 in the first week; in the
+ * second both clip to Monday, and *any* tie-break that prefers B (longest-first
+ * does) moves A down to lane 1 mid-bar.
+ *
+ * So, FullCalendar's rule, in two phases per week:
+ *
+ *  1. **Continuations keep the lane they already hold.** This can never collide:
+ *     every bar continuing into this week covers its first day, so every pair of
+ *     them also overlapped on the previous week's last day, and they were given
+ *     distinct lanes there.
+ *  2. **Everything else competes** for the lowest free lane, longest first.
+ *
+ * Note that `continuesLeft` is geometry (the span starts before this week) while
+ * "is a continuation" is bookkeeping (we already gave it a lane). They are not the
+ * same, and conflating them breaks the first visible week: a bar running in from
+ * before the grid has no lane yet, so it competes as a newcomer while still
+ * drawing with an open left edge.
+ *
+ * A task that finds no free lane is not drawn and is counted against **every** day
+ * it covers, because each cell's "+2" has to describe that cell — it is what opens
+ * when you tap it. It is deliberately given no lane, so next week it competes
+ * again and may well win one.
+ *
+ * [maxLanes] is a per-client layout budget, not a shared rule: it is a required
+ * argument with no default so that neither client can drift into its own idea of
+ * what "the" value is.
+ */
+fun layoutMonth(
+    weeks: List<List<String>>,
+    items: List<CalendarItem>,
+    maxLanes: Int,
+): List<WeekLayout> {
+    val placed = items.mapNotNull { item -> spanOf(item)?.let { Placed(item, it) } }
+    val laneOf = mutableMapOf<Long, Int>()
+    val layouts = mutableListOf<WeekLayout>()
+
+    for (week in weeks) {
+        val weekStart = week[0]
+        val weekEnd = week[6]
+        val inWeek = placed.filter { it.span.start <= weekEnd && it.span.end >= weekStart }
+
+        val occupied = Array(maxLanes) { BooleanArray(7) }
+        val bars = mutableListOf<Bar>()
+        val overflow = IntArray(7)
+
+        fun columns(entry: Placed): Pair<Int, Int> = Pair(
+            if (entry.span.start < weekStart) 0 else diffDays(weekStart, entry.span.start),
+            if (entry.span.end > weekEnd) 6 else diffDays(weekStart, entry.span.end),
+        )
+
+        fun claim(lane: Int, from: Int, to: Int) {
+            for (column in from..to) occupied[lane][column] = true
+        }
+
+        fun free(lane: Int, from: Int, to: Int): Boolean {
+            for (column in from..to) if (occupied[lane][column]) return false
+            return true
+        }
+
+        fun barFor(entry: Placed, lane: Int, from: Int, to: Int) = Bar(
+            id = entry.item.id,
+            lane = lane,
+            startCol = from,
+            endCol = to,
+            continuesLeft = entry.span.start < weekStart,
+            continuesRight = entry.span.end > weekEnd,
+        )
+
+        // Phase 1 — continuations reclaim their lane, in lane order.
+        val continuing = inWeek
+            .filter { it.span.start < weekStart && laneOf.containsKey(it.item.id) }
+            .sortedBy { laneOf.getValue(it.item.id) }
+        for (entry in continuing) {
+            val lane = laneOf.getValue(entry.item.id)
+            val (from, to) = columns(entry)
+            claim(lane, from, to)
+            bars.add(barFor(entry, lane, from, to))
+        }
+
+        // Phase 2 — the rest take the lowest lane that fits.
+        val seen = continuing.map { it.item.id }.toSet()
+        val starting = inWeek
+            .filter { it.item.id !in seen }
+            .sortedWith(
+                compareByDescending<Placed> { it.span.days }
+                    .thenBy { it.span.start }
+                    .thenBy { it.item.id },
+            )
+        for (entry in starting) {
+            val (from, to) = columns(entry)
+            val lane = (0 until maxLanes).firstOrNull { free(it, from, to) }
+            if (lane == null) {
+                for (column in from..to) overflow[column] += 1
+                continue
+            }
+            claim(lane, from, to)
+            laneOf[entry.item.id] = lane
+            bars.add(barFor(entry, lane, from, to))
+        }
+
+        layouts.add(
+            WeekLayout(
+                dates = week,
+                bars = bars,
+                overflow = overflow.toList(),
+                lanes = bars.maxOfOrNull { it.lane + 1 } ?: 0,
+                hasOverflow = overflow.any { it > 0 },
+            ),
+        )
+    }
+
+    return layouts
+}
+
+// --------------------------------------------------------------------------
+// The type filter
+// --------------------------------------------------------------------------
+
+data class FilterNode(
+    /** `"jira"` for a source, `"jira/MIPT"` for one of its projects. */
+    val key: String,
+    val label: String,
+    val count: Int,
+    val children: List<FilterNode>,
+)
+
+private fun projectKey(source: String, project: String): String = "$source/$project"
+
+/**
+ * Sources, each expanded into the projects seen under it.
+ *
+ * Only tasks that *name* a project get a child node, so a source's children can
+ * sum to less than its own count; those tasks are reachable by hiding the whole
+ * source, which is the honest thing a "(none)" bucket would only dress up.
+ */
+fun buildFilterTree(items: List<CalendarItem>): List<FilterNode> {
+    class Entry(var label: String) {
+        var count = 0
+        val projects = linkedMapOf<String, Int>()
+    }
+
+    val sources = linkedMapOf<String, Entry>()
+    for (item in items) {
+        val entry = sources.getOrPut(item.source) {
+            Entry(item.sourceLabel.ifBlank { item.source })
+        }
+        entry.count += 1
+        val project = item.project?.trim().orEmpty()
+        if (project.isNotEmpty()) entry.projects[project] = (entry.projects[project] ?: 0) + 1
+    }
+
+    return sources.entries
+        .sortedBy { it.value.label }
+        .map { (source, entry) ->
+            FilterNode(
+                key = source,
+                label = entry.label,
+                count = entry.count,
+                children = entry.projects.entries
+                    .sortedBy { it.key }
+                    .map { (project, count) ->
+                        FilterNode(projectKey(source, project), project, count, emptyList())
+                    },
+            )
+        }
+}
+
+/** Hiding a source hides its projects with it. */
+fun isHidden(item: CalendarItem, hidden: Set<String>): Boolean {
+    if (item.source in hidden) return true
+    val project = item.project?.trim().orEmpty()
+    return project.isNotEmpty() && projectKey(item.source, project) in hidden
+}
+
+data class CalendarModel<T : CalendarItem>(
+    /** What the grid draws. */
+    val visible: List<T>,
+    /** Passing the type filter but carrying no due date, so nowhere to draw them. */
+    val undated: List<T>,
+    /** Spanning more than a week — the toggle's count, whether or not it is on. */
+    val longCount: Int,
+)
+
+/**
+ * One pass over the list for everything the toolbar and the grid need.
+ *
+ * [longCount] deliberately ignores [showLong], so the toggle's own label does not
+ * change the moment you press it.
+ */
+fun <T : CalendarItem> buildModel(
+    items: List<T>,
+    hidden: Set<String>,
+    showLong: Boolean,
+): CalendarModel<T> {
+    val visible = mutableListOf<T>()
+    val undated = mutableListOf<T>()
+    var longCount = 0
+
+    for (item in items) {
+        if (isHidden(item, hidden)) continue
+        val value = spanOf(item)
+        if (value == null) {
+            undated.add(item)
+            continue
+        }
+        if (isLong(value)) {
+            longCount += 1
+            if (!showLong) continue
+        }
+        visible.add(item)
+    }
+
+    return CalendarModel(visible, undated, longCount)
+}
+
+/** The tasks touching one day, in the order the grid stacks them. */
+fun <T : CalendarItem> itemsOnDay(items: List<T>, day: String): List<T> =
+    items
+        .mapNotNull { item -> spanOf(item)?.let { Pair(item, it) } }
+        .filter { (_, span) -> span.start <= day && span.end >= day }
+        .sortedWith(
+            compareBy<Pair<T, Span>> { it.second.start }
+                .thenByDescending { it.second.days }
+                .thenBy { it.first.id },
+        )
+        .map { it.first }

android/core/src/main/kotlin/tech/kadence/core/Timer.kt

@@ -11,7 +11,10 @@
  *  * `POST /api/timer/start` **abandons** whatever is running, with reason
  *    `"superseded"` — so a queued start is destructive, not additive.
  *  * `POST /api/timer/complete` may **auto-start the next interval**, so a reply can
- *    contain an interval nobody explicitly asked for.
+ *    contain an interval nobody explicitly asked for. It also takes a `session_id`:
+ *    the interval the caller means to finish. Without one the call is unconditional,
+ *    and two clients hitting zero in the same second end up finishing two intervals —
+ *    the second call landing on the break the first one's auto-start had just begun.
  *  * There is **no stop endpoint**: stopping is `abandon`, and under `strict_mode` a
  *    work interval refuses to be abandoned without a reason.
  */

android/core/src/test/kotlin/tech/kadence/core/CalendarParityTest.kt

@@ -0,0 +1,67 @@
+package tech.kadence.core
+
+import java.io.File
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+
+/**
+ * The calendar algorithm, checked against the web app's own source.
+ *
+ * `Calendar.kt` is a hand port of `frontend/src/lib/calendar.ts`, and the two can
+ * only drift silently. This does what `TokenParityTest` does for the palette:
+ * reads the actual TypeScript and fails when it disagrees.
+ *
+ * It can check two things honestly. **`LONG_TASK_DAYS` is a shared product rule**
+ * — a week means a week on both clients — so its value is asserted. And **every
+ * exported function must exist on both sides**, which is weak but catches the
+ * real failure mode: a rule added to one copy and forgotten in the other.
+ *
+ * `maxLanes` is deliberately *not* checked. It is a per-client layout budget
+ * (the phone has less room than a browser), so pinning it across clients would
+ * encode a false equivalence — which is why it is a required argument with no
+ * default on either side.
+ *
+ * If `frontend/` is ever absent (a checkout of this module alone), these skip
+ * rather than fail — they are a guard, not a dependency.
+ */
+class CalendarParityTest {
+
+    private val repoRoot: File? = generateSequence(File("").absoluteFile) { it.parentFile }
+        .firstOrNull { File(it, "frontend/src/lib/calendar.ts").isFile }
+
+    private val calendarTs: File? = repoRoot?.let { File(it, "frontend/src/lib/calendar.ts") }
+
+    @Test
+    fun `the parity guard actually found the web app`() {
+        // Without this the whole file silently passes by skipping forever.
+        assertTrue(
+            calendarTs != null || System.getenv("CI") == null,
+            "frontend/src/lib/calendar.ts was not found from ${File("").absolutePath}",
+        )
+    }
+
+    @Test
+    fun `the long-task threshold matches calendar ts`() {
+        val source = calendarTs?.readText() ?: return
+        val declared = Regex("""export const LONG_TASK_DAYS\s*=\s*(\d+)""")
+            .find(source)
+            ?.groupValues
+            ?.get(1)
+            ?.toInt()
+        assertEquals(LONG_TASK_DAYS, declared, "LONG_TASK_DAYS drifted from calendar.ts")
+    }
+
+    @Test
+    fun `every exported function has a kotlin counterpart`() {
+        val source = calendarTs?.readText() ?: return
+        val exported = Regex("""export function (\w+)""").findAll(source).map { it.groupValues[1] }.toSortedSet()
+        assertTrue(exported.isNotEmpty(), "could not read the exports out of calendar.ts")
+
+        val kotlin = File(repoRoot, "android/core/src/main/kotlin/tech/kadence/core/Calendar.kt").readText()
+        val missing = exported.filterNot { name ->
+            Regex("""fun (<[^>]+> )?$name\b""").containsMatchIn(kotlin)
+        }
+        assertEquals(emptyList(), missing, "calendar.ts exports these and Calendar.kt does not")
+    }
+}

android/core/src/test/kotlin/tech/kadence/core/CalendarTest.kt

@@ -0,0 +1,325 @@
+package tech.kadence.core
+
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+import kotlin.test.assertNotNull
+import kotlin.test.assertNull
+import kotlin.test.assertTrue
+
+/**
+ * The calendar layout, against hand-written items.
+ *
+ * There is no test runner on the web side, so this suite is the only place the
+ * algorithm is actually executed — `calendar.ts` and `Calendar.kt` are the same
+ * code written twice and only this copy runs. Every case here is a bug that was
+ * either found in review or is cheap to reintroduce.
+ */
+class CalendarTest {
+
+    private data class Item(
+        override val id: Long,
+        override val dueDate: String? = null,
+        override val startDate: String? = null,
+        override val source: String = "jira",
+        override val sourceLabel: String = "Jira",
+        override val project: String? = null,
+    ) : CalendarItem
+
+    private fun laneOf(layouts: List<WeekLayout>, week: Int, id: Long): Int? =
+        layouts[week].bars.firstOrNull { it.id == id }?.lane
+
+    // -- the grid ----------------------------------------------------------
+
+    @Test
+    fun `october 2026 runs from 28 september to 1 november`() {
+        val weeks = monthGrid(2026, 10, weekStartsMonday = true)
+        assertEquals(5, weeks.size, "October 2026 needs five rows, not a padded six")
+        assertEquals("2026-09-28", weeks.first().first())
+        assertEquals("2026-11-01", weeks.last().last())
+        assertTrue(weeks.all { it.size == 7 })
+    }
+
+    @Test
+    fun `a sunday-first grid shifts the month by one day`() {
+        val monday = monthGrid(2026, 10, weekStartsMonday = true)
+        val sunday = monthGrid(2026, 10, weekStartsMonday = false)
+        assertEquals("2026-09-28", monday.first().first())
+        assertEquals("2026-09-27", sunday.first().first())
+    }
+
+    @Test
+    fun `a 28-day month starting on its own first weekday needs only four rows`() {
+        // February 2026 begins on a Sunday; February 2027 begins on a Monday.
+        assertEquals(4, monthGrid(2026, 2, weekStartsMonday = false).size)
+        assertEquals(4, monthGrid(2027, 2, weekStartsMonday = true).size)
+    }
+
+    @Test
+    fun `shiftMonth crosses the year in both directions`() {
+        assertEquals(Pair(2025, 12), shiftMonth(2026, 1, -1))
+        assertEquals(Pair(2027, 1), shiftMonth(2026, 12, 1))
+        assertEquals(Pair(2026, 10), shiftMonth(2026, 10, 0))
+    }
+
+    // -- spans -------------------------------------------------------------
+
+    @Test
+    fun `a span needs a due date`() {
+        assertEquals(Span("2026-10-19", "2026-10-21", 3), spanOf(Item(1, dueDate = "2026-10-21", startDate = "2026-10-19")))
+        assertEquals(Span("2026-10-21", "2026-10-21", 1), spanOf(Item(2, dueDate = "2026-10-21")))
+        // Start-only is the Jira backlog: a start date with no deadline, often
+        // months old. Drawing it on its start day is a confident wrong answer.
+        assertNull(spanOf(Item(3, startDate = "2026-06-01")))
+        assertNull(spanOf(Item(4)))
+    }
+
+    @Test
+    fun `a due date before the start date collapses to the deadline`() {
+        assertEquals(
+            Span("2026-10-19", "2026-10-19", 1),
+            spanOf(Item(1, dueDate = "2026-10-19", startDate = "2026-10-25")),
+        )
+    }
+
+    @Test
+    fun `exactly a week is not long`() {
+        val seven = spanOf(Item(1, startDate = "2026-10-19", dueDate = "2026-10-25"))!!
+        val eight = spanOf(Item(2, startDate = "2026-10-19", dueDate = "2026-10-26"))!!
+        assertEquals(7, seven.days)
+        assertFalse(isLong(seven))
+        assertEquals(8, eight.days)
+        assertTrue(isLong(eight))
+    }
+
+    @Test
+    fun `a long span stays long in the middle of its run`() {
+        // The bar below covers a whole week of March with nothing sticking out.
+        // Measured on the clipped segment it would read as exactly seven days and
+        // escape the filter in that month only.
+        val long = spanOf(Item(1, startDate = "2026-03-02", dueDate = "2026-04-02"))!!
+        assertTrue(isLong(long))
+    }
+
+    // -- lane packing ------------------------------------------------------
+
+    @Test
+    fun `a multi-week bar keeps its lane when a longer one starts beside it`() {
+        // The review counterexample. Packing each week independently and sorting
+        // longest-first hands lane 0 to B in week two and steps A down mid-bar.
+        val a = Item(1, startDate = "2026-03-02", dueDate = "2026-03-18") // 17 days
+        val b = Item(2, startDate = "2026-03-09", dueDate = "2026-04-02") // 25 days
+        val weeks = monthGrid(2026, 3, weekStartsMonday = true)
+        val layouts = layoutMonth(weeks, listOf(a, b), maxLanes = 4)
+
+        // Weeks of March 2026, Monday-first: [Feb23, Mar2, Mar9, Mar16, Mar23, Mar30]
+        assertEquals(0, laneOf(layouts, 1, 1L), "A owns lane 0 in its first week")
+        assertEquals(0, laneOf(layouts, 2, 1L), "A must still own lane 0 beside B")
+        assertEquals(0, laneOf(layouts, 3, 1L), "and in its last week")
+        assertEquals(1, laneOf(layouts, 2, 2L), "B takes the next free lane")
+        assertEquals(1, laneOf(layouts, 3, 2L))
+        assertEquals(1, laneOf(layouts, 4, 2L), "B keeps it after A ends")
+    }
+
+    @Test
+    fun `three overlapping multi-week bars keep distinct unchanged lanes`() {
+        val items = listOf(
+            Item(1, startDate = "2026-03-02", dueDate = "2026-03-27"),
+            Item(2, startDate = "2026-03-03", dueDate = "2026-03-26"),
+            Item(3, startDate = "2026-03-04", dueDate = "2026-03-25"),
+        )
+        val layouts = layoutMonth(monthGrid(2026, 3, true), items, maxLanes = 4)
+        val lanes = (1L..3L).map { id -> (1..4).map { week -> laneOf(layouts, week, id) } }
+        for ((index, perWeek) in lanes.withIndex()) {
+            assertEquals(
+                1, perWeek.filterNotNull().distinct().size,
+                "task ${index + 1} changed lane part-way through: $perWeek",
+            )
+        }
+        assertEquals(3, lanes.map { it.filterNotNull().first() }.distinct().size, "lanes must not collide")
+    }
+
+    @Test
+    fun `a bar running in from before the grid is drawn open-ended and still gets a lane`() {
+        val item = Item(1, startDate = "2026-02-01", dueDate = "2026-03-10")
+        val layouts = layoutMonth(monthGrid(2026, 3, true), listOf(item), maxLanes = 3)
+        val first = layouts.first().bars.single()
+        assertTrue(first.continuesLeft, "geometry says it began before this week")
+        assertEquals(0, first.lane, "bookkeeping had no lane for it, so it competes as a newcomer")
+    }
+
+    @Test
+    fun `overflow counts every day a dropped task covers`() {
+        // Six single-day tasks on one day, with room for two.
+        val day = "2026-10-14"
+        val items = (1L..6L).map { Item(it, dueDate = day) }
+        val layouts = layoutMonth(monthGrid(2026, 10, true), items, maxLanes = 2)
+        val week = layouts.first { it.dates.contains(day) }
+        val column = week.dates.indexOf(day)
+
+        assertEquals(2, week.bars.size, "two lanes, two bars")
+        assertEquals(4, week.overflow[column], "the other four are counted on that day")
+        assertTrue(week.hasOverflow)
+        assertEquals(0, week.overflow.filterIndexed { index, _ -> index != column }.sum())
+    }
+
+    @Test
+    fun `a dropped multi-day task is counted on each of its days`() {
+        val items = listOf(
+            Item(1, dueDate = "2026-10-16", startDate = "2026-10-14"),
+            Item(2, dueDate = "2026-10-16", startDate = "2026-10-14"),
+            Item(3, dueDate = "2026-10-16", startDate = "2026-10-14"),
+        )
+        val layouts = layoutMonth(monthGrid(2026, 10, true), items, maxLanes = 2)
+        val week = layouts.first { it.dates.contains("2026-10-14") }
+        val from = week.dates.indexOf("2026-10-14")
+        assertEquals(listOf(1, 1, 1), (from..from + 2).map { week.overflow[it] })
+    }
+
+    @Test
+    fun `a task that overflows one week can win a lane the next`() {
+        // Two single-day blockers in week one only, plus a bar crossing both weeks.
+        val crossing = Item(99, startDate = "2026-10-09", dueDate = "2026-10-14")
+        val blockers = listOf(
+            Item(1, startDate = "2026-10-05", dueDate = "2026-10-11"),
+            Item(2, startDate = "2026-10-05", dueDate = "2026-10-11"),
+        )
+        val layouts = layoutMonth(monthGrid(2026, 10, true), blockers + crossing, maxLanes = 2)
+        val first = layouts.first { it.dates.contains("2026-10-09") }
+        val second = layouts.first { it.dates.contains("2026-10-14") }
+
+        assertNull(first.bars.firstOrNull { it.id == 99L }, "no lane left for it in week one")
+        assertTrue(first.overflow[first.dates.indexOf("2026-10-09")] > 0)
+
+        val bar = assertNotNull(second.bars.firstOrNull { it.id == 99L }, "week two has room, so it is drawn")
+        assertTrue(bar.continuesLeft, "and drawn open on the left, because it did start earlier")
+    }
+
+    @Test
+    fun `no overflow means no reserved strip`() {
+        val items = listOf(Item(1, dueDate = "2026-10-14"), Item(2, dueDate = "2026-10-15"))
+        val layouts = layoutMonth(monthGrid(2026, 10, true), items, maxLanes = 3)
+        assertTrue(layouts.none { it.hasOverflow })
+        assertTrue(layouts.all { it.overflow.sum() == 0 })
+    }
+
+    @Test
+    fun `the layout does not depend on the order of the input`() {
+        // This is what guarantees the phone and the browser draw the same month.
+        val items = listOf(
+            Item(1, startDate = "2026-10-01", dueDate = "2026-10-20"),
+            Item(2, dueDate = "2026-10-14"),
+            Item(3, startDate = "2026-10-12", dueDate = "2026-10-16"),
+            Item(4, startDate = "2026-09-20", dueDate = "2026-10-06"),
+            Item(5, dueDate = "2026-10-14"),
+        )
+        val weeks = monthGrid(2026, 10, true)
+        val expected = layoutMonth(weeks, items, maxLanes = 3)
+        assertEquals(expected, layoutMonth(weeks, items.reversed(), maxLanes = 3))
+        assertEquals(expected, layoutMonth(weeks, items.shuffled(java.util.Random(7)), maxLanes = 3))
+    }
+
+    @Test
+    fun `an undated task is never laid out`() {
+        val layouts = layoutMonth(monthGrid(2026, 10, true), listOf(Item(1, startDate = "2026-10-12")), maxLanes = 3)
+        assertTrue(layouts.all { it.bars.isEmpty() && it.overflow.sum() == 0 })
+    }
+
+    // -- the type filter ---------------------------------------------------
+
+    private val mixed = listOf(
+        Item(1, dueDate = "2026-10-14", source = "jira", sourceLabel = "Jira", project = "MIPT"),
+        Item(2, dueDate = "2026-10-15", source = "jira", sourceLabel = "Jira", project = "MIPT"),
+        Item(3, dueDate = "2026-10-15", source = "jira", sourceLabel = "Jira", project = "PLAT"),
+        Item(4, dueDate = "2026-10-15", source = "jira", sourceLabel = "Jira"),
+        Item(5, dueDate = "2026-10-15", source = "todoist", sourceLabel = "Todoist", project = "Home"),
+        Item(6, dueDate = "2026-10-15", source = "laundry", sourceLabel = "Laundry", project = "Laundry"),
+    )
+
+    @Test
+    fun `the tree is sources expanded into their projects`() {
+        val tree = buildFilterTree(mixed)
+        assertEquals(listOf("jira", "laundry", "todoist"), tree.map { it.key }, "ordered by label")
+        val jira = tree.first { it.key == "jira" }
+        assertEquals(4, jira.count, "the project-less issue still counts against the source")
+        assertEquals(listOf("jira/MIPT", "jira/PLAT"), jira.children.map { it.key })
+        assertEquals(listOf(2, 1), jira.children.map { it.count })
+    }
+
+    @Test
+    fun `hiding a source hides its projects with it`() {
+        val hidden = setOf("jira")
+        assertTrue(mixed.filter { it.source == "jira" }.all { isHidden(it, hidden) })
+        assertFalse(isHidden(mixed.first { it.source == "todoist" }, hidden))
+    }
+
+    @Test
+    fun `hiding one project leaves its siblings alone`() {
+        val hidden = setOf("jira/MIPT")
+        assertTrue(isHidden(mixed[0], hidden))
+        assertFalse(isHidden(mixed[2], hidden), "PLAT is untouched")
+        assertFalse(isHidden(mixed[3], hidden), "and so is the issue with no project")
+    }
+
+    @Test
+    fun `a project nobody has hidden is visible`() {
+        // The set holds hidden keys, never visible ones, so a project that first
+        // appears after a refresh shows up instead of being filtered out by a set
+        // written last week.
+        val hidden = setOf("jira/MIPT")
+        val fresh = Item(7, dueDate = "2026-10-15", source = "jira", sourceLabel = "Jira", project = "NEW")
+        assertFalse(isHidden(fresh, hidden))
+    }
+
+    // -- the model ---------------------------------------------------------
+
+    @Test
+    fun `the model splits visible, long and undated in one pass`() {
+        val items = listOf(
+            Item(1, dueDate = "2026-10-14"),
+            Item(2, startDate = "2026-10-01", dueDate = "2026-10-20"),
+            Item(3, startDate = "2026-06-01"),
+            Item(4, dueDate = "2026-10-15", source = "laundry", sourceLabel = "Laundry", project = "Laundry"),
+        )
+
+        val hiddenNothing = emptySet<String>()
+        val collapsed = buildModel(items, hiddenNothing, showLong = false)
+        assertEquals(listOf(1L, 4L), collapsed.visible.map { it.id })
+        assertEquals(listOf(3L), collapsed.undated.map { it.id })
+        assertEquals(1, collapsed.longCount)
+
+        val expanded = buildModel(items, hiddenNothing, showLong = true)
+        assertEquals(listOf(1L, 2L, 4L), expanded.visible.map { it.id })
+        assertEquals(1, expanded.longCount, "the count must not move when the toggle flips")
+
+        val filtered = buildModel(items, setOf("laundry"), showLong = false)
+        assertEquals(listOf(1L), filtered.visible.map { it.id })
+    }
+
+    @Test
+    fun `a laundry slot is a one-day bar and is never long`() {
+        // `laundry.py` emits due_date=today with no start date, one row per slot.
+        val slot = Item(1, dueDate = "2026-10-14", source = "laundry", sourceLabel = "Laundry", project = "Laundry")
+        val span = spanOf(slot)!!
+        assertEquals(1, span.days)
+        assertFalse(isLong(span))
+    }
+
+    @Test
+    fun `itemsOnDay returns everything covering that day, longest first`() {
+        val items = listOf(
+            Item(1, dueDate = "2026-10-14"),
+            Item(2, startDate = "2026-10-12", dueDate = "2026-10-16"),
+            Item(3, dueDate = "2026-10-20"),
+        )
+        assertEquals(listOf(2L, 1L), itemsOnDay(items, "2026-10-14").map { it.id })
+        assertEquals(emptyList(), itemsOnDay(items, "2026-10-18").map { it.id })
+    }
+
+    @Test
+    fun `weekday labels follow the week start`() {
+        assertEquals("Mon", weekdayLabels(true).first())
+        assertEquals("Sun", weekdayLabels(false).first())
+        assertEquals(7, weekdayLabels(true).size)
+    }
+}

backend/app/api/routes_timer.py

@@ -63,11 +63,18 @@ def resume(session: DbSession, settings: Settings) -> dict:
 @router.post("/complete")
 def complete(body: CompleteTimerRequest, session: DbSession, settings: Settings) -> dict:
     try:
-        finished, follow_on = pomodoro.complete(session, settings, auto_next=body.auto_next)
+        finished, follow_on = pomodoro.complete(
+            session,
+            settings,
+            auto_next=body.auto_next,
+            expect_id=body.session_id,
+        )
     except pomodoro.TimerError as exc:
         raise HTTPException(status_code=400, detail=str(exc)) from exc
 
-    celebration = _maybe_celebrate(session, settings) if finished.is_work else None
+    # `finished` is None when the named interval was no longer the running one:
+    # nothing happened, so there is nothing to celebrate and nothing to announce.
+    celebration = _maybe_celebrate(session, settings) if finished and finished.is_work else None
     state = pomodoro.state(session, settings)
     state["finished"] = pomodoro.session_dict(finished)
     state["auto_started"] = pomodoro.session_dict(follow_on)

backend/app/api/schemas.py

@@ -29,6 +29,16 @@ class AttachTaskRequest(BaseModel):
 
 class CompleteTimerRequest(BaseModel):
     auto_next: bool = True
+    session_id: int | None = None
+    """Which interval the client believes it is finishing.
+
+    Every client ticks its own local countdown and calls `complete` when it
+    reaches zero, so with two of them open (the phone and the desktop, say)
+    both fire within the same second. Unconditionally, the second call lands
+    on whatever `auto_next` has just started and ends *that* — which is why a
+    break could vanish the instant it began. Sent along, a stale call is a
+    no-op instead. Omitted, the old unconditional behaviour stands.
+    """
 
 
 class TaskCreateRequest(BaseModel):

backend/app/services/pomodoro.py

@@ -176,10 +176,28 @@ def resume(session: Session) -> PomodoroSession:
 
 
 def complete(
-    session: Session, settings: AppSettings, *, auto_next: bool = True
-) -> tuple[PomodoroSession, PomodoroSession | None]:
-    """Finish the current interval and, if configured, roll into the next one."""
-    row = _require_active(session)
+    session: Session,
+    settings: AppSettings,
+    *,
+    auto_next: bool = True,
+    expect_id: int | None = None,
+) -> tuple[PomodoroSession | None, PomodoroSession | None]:
+    """Finish the current interval and, if configured, roll into the next one.
+
+    `expect_id` is the interval the caller believes it is finishing. Every
+    client runs its own local countdown and calls this when it hits zero, so
+    two clients open at once both call within the same second — and the second
+    call used to land on the interval `auto_next` had just created and end it
+    immediately. That is a break disappearing the moment it starts, and it is
+    not something a client can fix on its own: only the server knows which
+    interval is current. So a call that names an interval which is no longer
+    running does nothing at all, and says so by returning no `finished`.
+    """
+    row = current_session(session)
+    if expect_id is not None and (row is None or row.id != expect_id):
+        return None, None
+    if row is None:
+        raise TimerError("No interval is running.")
     finished = _finish(session, settings, row, status="completed")
 
     follow_on: PomodoroSession | None = None

backend/tests/test_api.py

@@ -29,6 +29,28 @@ def test_a_whole_pomodoro_through_the_api(client):
     assert "Daily report" in report["telegram_preview"]
 
 
+def test_a_stale_complete_leaves_the_auto_started_break_alone(client):
+    client.put(
+        "/api/settings",
+        json={"pomodoro": {"auto_start_breaks": True, "auto_start_work": True}},
+    )
+    state = client.post("/api/timer/start", json={"kind": "work"}).json()
+    work_id = state["current"]["id"]
+
+    done = client.post(
+        "/api/timer/complete", json={"auto_next": True, "session_id": work_id}
+    ).json()
+    assert done["current"]["kind"] in ("short_break", "long_break")
+    break_id = done["current"]["id"]
+
+    # The other client's countdown, one beat behind.
+    again = client.post(
+        "/api/timer/complete", json={"auto_next": True, "session_id": work_id}
+    ).json()
+    assert again["finished"] is None
+    assert again["current"]["id"] == break_id
+
+
 def test_timer_errors_are_400_not_500(client):
     assert client.post("/api/timer/pause").status_code == 400
     assert client.post("/api/timer/complete", json={}).status_code == 400

backend/tests/test_pomodoro.py

@@ -69,6 +69,40 @@ def test_auto_start_breaks_rolls_straight_on(session, settings):
     assert follow_on is not None and follow_on.kind == "short_break"
 
 
+def test_a_complete_naming_a_finished_interval_does_nothing(session, settings):
+    """Two clients reaching zero at once must not cost you the break.
+
+    Every client ticks its own countdown and calls `complete` when it runs out.
+    The first call finishes the work interval and auto-starts the break; the
+    second — sent a moment earlier, from a client that has not polled since —
+    used to finish *that* break, so a break ended the instant it began.
+    """
+    settings.pomodoro.auto_start_breaks = True
+    settings.pomodoro.auto_start_work = True
+    settings_service.save_settings(session, settings)
+
+    work = pomodoro.start(session, settings, kind="work")
+    finished, follow_on = pomodoro.complete(session, settings, expect_id=work.id)
+    assert finished is not None and follow_on is not None
+    assert follow_on.kind == "short_break"
+
+    # The second client's call, naming the work interval it was still showing.
+    stale_finished, stale_follow_on = pomodoro.complete(session, settings, expect_id=work.id)
+    assert stale_finished is None and stale_follow_on is None
+
+    still_running = pomodoro.current_session(session)
+    assert still_running is not None
+    assert still_running.id == follow_on.id and still_running.status == "running"
+
+
+def test_complete_without_a_session_id_stays_unconditional(session, settings):
+    settings.pomodoro.auto_start_breaks = False
+    settings_service.save_settings(session, settings)
+    pomodoro.start(session, settings, kind="work")
+    finished, _ = pomodoro.complete(session, settings)
+    assert finished is not None and finished.status == "completed"
+
+
 def test_strict_mode_demands_a_reason(session, settings):
     settings.pomodoro.strict_mode = True
     settings_service.save_settings(session, settings)

desktop/kadence_desktop/api.py

@@ -87,8 +87,18 @@ class Api:
     def resume(self) -> dict:
         return self._request("POST", "/api/timer/resume", {})
 
-    def complete(self, auto_next: bool = True) -> dict:
-        return self._request("POST", "/api/timer/complete", {"auto_next": auto_next})
+    def complete(self, auto_next: bool = True, session_id: int | None = None) -> dict:
+        """`session_id` names the interval we think we are finishing.
+
+        The server ignores the call if something else is running by then, which
+        is what keeps two clients hitting zero at the same moment from eating
+        the break the first one's `auto_next` just started.
+        """
+        return self._request(
+            "POST",
+            "/api/timer/complete",
+            {"auto_next": auto_next, "session_id": session_id},
+        )
 
     def abandon(self, reason: str | None = None) -> dict:
         return self._request("POST", "/api/timer/abandon", {"reason": reason})

desktop/kadence_desktop/controller.py

@@ -78,7 +78,17 @@ class Controller(QObject):
         self._last_session_id: int | None = None
         self._last_kind = ""
         self._last_status = ""
-        self._completing = False
+        self._completed_id: int | None = None
+        """The interval we have already asked the server to finish.
+
+        An id rather than a bare "in flight" flag. A poll issued just before the
+        countdown ran out answers with that interval still running at 00:00, and
+        a flag cleared by that answer sends `complete` a second time — onto the
+        break `auto_next` has since started, which is why a break could end the
+        instant it began. Ids are never reused, so the second attempt is never
+        made. Cleared only when the call itself fails, so a refused or dropped
+        complete is still retried.
+        """
         self._paused_by_lock = False
         self._mini_visible = False
         self._mini_dismissed = False
@@ -174,6 +184,13 @@ class Controller(QObject):
         current = self._state.get("current")
         return str(current["status"]) if current else "idle"
 
+    @property
+    def _session_id(self) -> int | None:
+        """The running interval's id, or None when nothing is running."""
+        current = self._state.get("current") or {}
+        session_id = current.get("id")
+        return int(session_id) if session_id is not None else None
+
     @pyqtProperty(int, notify=stateChanged)
     def remainingSeconds(self) -> int:
         if self._state.get("current"):
@@ -393,7 +410,7 @@ class Controller(QObject):
 
     @pyqtSlot()
     def complete(self) -> None:
-        self._send("complete", {"auto_next": True})
+        self._send("complete", {"auto_next": True, "session_id": self._session_id})
 
     @pyqtSlot()
     @pyqtSlot(str)
@@ -567,7 +584,6 @@ class Controller(QObject):
             self._last_session_id = session_id
             self._last_kind = kind
             self._last_status = status
-        self._completing = False
         self.stateChanged.emit()
         self._update_launcher()
 
@@ -610,12 +626,18 @@ class Controller(QObject):
 
     def _on_command_failed(self, name: str, detail: str) -> None:
         log.warning("%s failed: %s", name, detail)
+        if name == "complete":
+            # It never landed, so the interval at 00:00 is still owed a complete.
+            self._completed_id = None
         self.toast.emit(detail)
 
     def _on_command_done(self, name: str, result: dict[str, Any]) -> None:
         if name == "complete":
-            finished = result.get("finished") or {}
-            self._announce_finished(str(finished.get("kind", "work")), result)
+            finished = result.get("finished")
+            # None means the server declined: something else was running by the
+            # time the call arrived, so nothing finished and nothing is announced.
+            if finished:
+                self._announce_finished(str(finished.get("kind", "work")), result)
         elif name == "send_report":
             self.toast.emit("Daily report sent" if result.get("sent") else "Report not sent — check Telegram settings")
         elif name == "refresh_sources":
@@ -706,10 +728,11 @@ class Controller(QObject):
             if self._remaining % 5 == 0:
                 self._update_launcher()
             return
-        if not self._completing:
+        session_id = self._session_id
+        if session_id is not None and self._completed_id != session_id:
             # The countdown reached zero: the server books the interval, and its
             # reply decides what happens next (auto-break, or nothing).
-            self._completing = True
+            self._completed_id = session_id
             self.complete()
 
     def _check_idle(self) -> None:

desktop/packaging/kadence.desktop

@@ -3,7 +3,7 @@ Type=Application
 Name=Kadence
 GenericName=Pomodoro timer
 Comment=Pomodoro timer and focus guard — a tray agent with a floating countdown
-Exec=kadence-desktop --mini
+Exec=kadence-desktop
 TryExec=kadence-desktop
 Icon=kadence
 Terminal=false

frontend/src/components/calendar/TaskCalendar.tsx

@@ -0,0 +1,387 @@
+/**
+ * The month, as bars from start date to deadline.
+ *
+ * Built like a printed table rather than a grid of cards: hairlines between the
+ * cells, tabular day figures, the month set in the display serif, and exactly
+ * one accent — today.
+ *
+ * Bars are coloured by **state, not by source**. Five saturated fills across a
+ * month grid would read as Material rather than Kadence, and five categorical
+ * hues cannot clear the data-viz palette validator's all-pairs normal-vision
+ * floor anyway (the first three slots are the documented limit). Identity comes
+ * from the title and from the filter; colour is kept for what changes how you
+ * act on a task — done, overdue, or still waiting.
+ *
+ * The layout maths all live in `lib/calendar.ts`, which `:core` ports verbatim.
+ */
+import { useMemo, useState } from "react";
+import { Box, Button, Divider, Popover, Stack, Typography, useMediaQuery, useTheme } from "@mui/material";
+import ChevronLeftIcon from "@mui/icons-material/ChevronLeft";
+import ChevronRightIcon from "@mui/icons-material/ChevronRight";
+
+import { Panel } from "../Layout";
+import TaskRow from "../tasks/TaskRow";
+import {
+  itemsOnDay,
+  layoutMonth,
+  monthGrid,
+  shiftMonth,
+  todayISO,
+  weekdayLabels,
+  type WeekLayout,
+} from "../../lib/calendar";
+import type { Task } from "../../lib/types";
+
+const DAY_STRIP = 22;
+const BAR_H = 20;
+const BAR_GAP = 3;
+const OVERFLOW_H = 18;
+const MIN_ROW = 88;
+
+/**
+ * Monday-first on both clients for now.
+ *
+ * `AppSettings.week_starts_monday` exists and the web app could read it, but the
+ * phone cannot — `AppSettingsDto` does not carry it and the tasks screen loads
+ * no settings — so honouring it here alone is how the two clients start
+ * disagreeing about what a week is. The backend default is Monday anyway.
+ */
+const WEEK_STARTS_MONDAY = true;
+
+export default function TaskCalendar({
+  tasks,
+  longCount,
+  showLong,
+  onShowLong,
+  onPin,
+  onStart,
+  onDelete,
+}: {
+  /** Already filtered: the type tree and the long-task toggle have been applied. */
+  tasks: Task[];
+  longCount: number;
+  showLong: boolean;
+  onShowLong: (next: boolean) => void;
+  onPin: (task: Task) => Promise<void>;
+  onStart: (task: Task) => Promise<void>;
+  onDelete: (task: Task) => Promise<void>;
+}) {
+  const theme = useTheme();
+  const wide = useMediaQuery(theme.breakpoints.up("sm"));
+  const today = todayISO();
+  const [cursor, setCursor] = useState<[number, number]>(() => {
+    const now = new Date();
+    return [now.getFullYear(), now.getMonth() + 1];
+  });
+  const [day, setDay] = useState<{ date: string; anchor: HTMLElement } | null>(null);
+
+  const [year, month] = cursor;
+  // Showing long bars needs the room they take, or they simply push the day's
+  // real work into "+N" and the month gets less informative, not more.
+  const maxLanes = wide ? (showLong ? 5 : 4) : 2;
+
+  const weeks = useMemo(() => monthGrid(year, month, WEEK_STARTS_MONDAY), [year, month]);
+  const layouts = useMemo(() => layoutMonth(weeks, tasks, maxLanes), [weeks, tasks, maxLanes]);
+  const byId = useMemo(() => new Map(tasks.map((task) => [task.id, task])), [tasks]);
+
+  const label = new Date(year, month - 1, 1).toLocaleDateString(undefined, {
+    month: "long",
+    year: "numeric",
+  });
+  const dayTasks = day ? itemsOnDay(tasks, day.date) : [];
+
+  return (
+    <>
+      <Stack
+        direction="row"
+        alignItems="center"
+        spacing={1}
+        sx={{ mb: 2, flexWrap: "wrap", rowGap: 1 }}
+      >
+        <Button size="small" sx={{ minWidth: 32, px: 0 }} onClick={() => setCursor(shiftMonth(year, month, -1))}>
+          <ChevronLeftIcon fontSize="small" />
+        </Button>
+        <Typography
+          sx={{
+            fontFamily: theme.typography.h4.fontFamily,
+            fontSize: 20,
+            minWidth: { xs: 0, sm: 190 },
+            letterSpacing: "-0.01em",
+          }}
+        >
+          {label}
+        </Typography>
+        <Button size="small" sx={{ minWidth: 32, px: 0 }} onClick={() => setCursor(shiftMonth(year, month, 1))}>
+          <ChevronRightIcon fontSize="small" />
+        </Button>
+        <Button
+          size="small"
+          onClick={() => {
+            const now = new Date();
+            setCursor([now.getFullYear(), now.getMonth() + 1]);
+          }}
+        >
+          Today
+        </Button>
+        <Box sx={{ flexGrow: 1 }} />
+        <Button
+          size="small"
+          variant={showLong ? "contained" : "outlined"}
+          disabled={longCount === 0}
+          onClick={() => onShowLong(!showLong)}
+        >
+          Long tasks ({longCount})
+        </Button>
+      </Stack>
+
+      <Panel padded={false} sx={{ overflow: "hidden" }}>
+        <Box
+          sx={{
+            display: "grid",
+            gridTemplateColumns: "repeat(7, 1fr)",
+            bgcolor: "action.hover",
+            borderBottom: 1,
+            borderColor: "divider",
+          }}
+        >
+          {weekdayLabels(WEEK_STARTS_MONDAY).map((name) => (
+            <Typography
+              key={name}
+              variant="overline"
+              color="text.secondary"
+              sx={{ textAlign: "center", py: 0.75, fontSize: 10 }}
+            >
+              {wide ? name : name.slice(0, 1)}
+            </Typography>
+          ))}
+        </Box>
+
+        {layouts.map((week, index) => (
+          <WeekRow
+            key={week.dates[0]}
+            week={week}
+            month={month}
+            today={today}
+            byId={byId}
+            last={index === layouts.length - 1}
+            onPickDay={(date, anchor) => setDay({ date, anchor })}
+          />
+        ))}
+      </Panel>
+
+      <Popover
+        open={day !== null}
+        anchorEl={day?.anchor ?? null}
+        onClose={() => setDay(null)}
+        anchorOrigin={{ vertical: "bottom", horizontal: "center" }}
+        transformOrigin={{ vertical: "top", horizontal: "center" }}
+        slotProps={{ paper: { sx: { mt: 0.5, width: 380, maxWidth: "92vw", maxHeight: 420 } } }}
+      >
+        <Box sx={{ p: 2 }}>
+          <Typography variant="overline" color="text.secondary">
+            {day && new Date(`${day.date}T00:00:00`).toLocaleDateString(undefined, {
+              weekday: "long",
+              day: "numeric",
+              month: "long",
+            })}
+          </Typography>
+          <Divider sx={{ mt: 0.5 }} />
+          {dayTasks.length === 0 ? (
+            <Typography variant="body2" color="text.secondary" sx={{ mt: 1.5 }}>
+              Nothing on this day.
+            </Typography>
+          ) : (
+            <Stack divider={<Divider />}>
+              {dayTasks.map((task) => (
+                <TaskRow
+                  key={task.id}
+                  task={task}
+                  onPin={() => onPin(task)}
+                  onStart={() => onStart(task)}
+                  onDelete={() => onDelete(task)}
+                />
+              ))}
+            </Stack>
+          )}
+        </Box>
+      </Popover>
+    </>
+  );
+}
+
+function WeekRow({
+  week,
+  month,
+  today,
+  byId,
+  last,
+  onPickDay,
+}: {
+  week: WeekLayout;
+  month: number;
+  today: string;
+  byId: Map<number, Task>;
+  last: boolean;
+  onPickDay: (date: string, anchor: HTMLElement) => void;
+}) {
+  const height =
+    DAY_STRIP + week.lanes * (BAR_H + BAR_GAP) + (week.hasOverflow ? OVERFLOW_H : 0) + 6;
+
+  return (
+    <Box
+      sx={{
+        position: "relative",
+        display: "grid",
+        gridTemplateColumns: "repeat(7, 1fr)",
+        minHeight: Math.max(MIN_ROW, height),
+        borderBottom: last ? 0 : 1,
+        borderColor: "divider",
+      }}
+    >
+      {week.dates.map((date, column) => {
+        const outside = Number(date.slice(5, 7)) !== month;
+        const isToday = date === today;
+        return (
+          <Box
+            key={date}
+            onClick={(event) => onPickDay(date, event.currentTarget)}
+            sx={{
+              borderRight: column === 6 ? 0 : 1,
+              borderColor: "divider",
+              px: 0.75,
+              pt: 0.5,
+              cursor: "pointer",
+              minWidth: 0,
+              "&:hover": { bgcolor: "action.hover" },
+            }}
+          >
+            <Typography
+              component="span"
+              variant="caption"
+              sx={{
+                fontVariantNumeric: "tabular-nums",
+                color: isToday ? "primary.main" : outside ? "text.disabled" : "text.secondary",
+                fontWeight: isToday ? 600 : 400,
+                borderBottom: isToday ? 2 : 0,
+                borderColor: "primary.main",
+                pb: isToday ? "1px" : 0,
+              }}
+            >
+              {Number(date.slice(8, 10))}
+            </Typography>
+          </Box>
+        );
+      })}
+
+      {week.bars.map((bar) => {
+        const task = byId.get(bar.id);
+        if (!task) return null;
+        return (
+          <Box
+            key={`${bar.id}-${bar.startCol}`}
+            sx={{
+              position: "absolute",
+              pointerEvents: "none",
+              top: DAY_STRIP + bar.lane * (BAR_H + BAR_GAP),
+              left: `${(bar.startCol / 7) * 100}%`,
+              width: `${((bar.endCol - bar.startCol + 1) / 7) * 100}%`,
+              px: "2px",
+              boxSizing: "border-box",
+            }}
+          >
+            <TaskBar task={task} today={today} continuesLeft={bar.continuesLeft} continuesRight={bar.continuesRight} />
+          </Box>
+        );
+      })}
+
+      {week.hasOverflow &&
+        week.overflow.map((count, column) =>
+          count > 0 ? (
+            <Typography
+              key={`more-${column}`}
+              variant="caption"
+              color="text.secondary"
+              sx={{
+                position: "absolute",
+                pointerEvents: "none",
+                top: DAY_STRIP + week.lanes * (BAR_H + BAR_GAP) + 1,
+                left: `${(column / 7) * 100}%`,
+                width: `${(1 / 7) * 100}%`,
+                px: "6px",
+                boxSizing: "border-box",
+                fontSize: 11,
+              }}
+            >
+              +{count} more
+            </Typography>
+          ) : null,
+        )}
+    </Box>
+  );
+}
+
+/**
+ * One bar.
+ *
+ * `days_overdue` and `bucket` are computed against *today* by the backend, so a
+ * stale laundry slot from March claims to be two hundred days overdue forever.
+ * Neither is used here: lateness is decided from the task's own due date, and
+ * only for something still open and still offered by its source.
+ */
+function TaskBar({
+  task,
+  today,
+  continuesLeft,
+  continuesRight,
+}: {
+  task: Task;
+  today: string;
+  continuesLeft: boolean;
+  continuesRight: boolean;
+}) {
+  const late = !task.is_done && !task.stale && task.due_date !== null && task.due_date < today;
+  const muted = task.is_done || task.stale;
+  const radius = "4px";
+
+  return (
+    <Box
+      sx={{
+        height: BAR_H,
+        display: "flex",
+        alignItems: "center",
+        gap: "6px",
+        px: "6px",
+        bgcolor: "action.hover",
+        borderTopLeftRadius: continuesLeft ? 0 : radius,
+        borderBottomLeftRadius: continuesLeft ? 0 : radius,
+        borderTopRightRadius: continuesRight ? 0 : radius,
+        borderBottomRightRadius: continuesRight ? 0 : radius,
+        minWidth: 0,
+      }}
+    >
+      {!continuesLeft && (
+        <Box
+          sx={{
+            width: 2,
+            height: "60%",
+            flexShrink: 0,
+            borderRadius: 2,
+            bgcolor: late ? "error.main" : muted ? "text.disabled" : "text.secondary",
+          }}
+        />
+      )}
+      <Typography
+        noWrap
+        sx={{
+          fontSize: 11.5,
+          lineHeight: 1,
+          minWidth: 0,
+          color: muted ? "text.disabled" : late ? "error.main" : "text.primary",
+          textDecoration: task.is_done ? "line-through" : "none",
+        }}
+      >
+        {task.title}
+      </Typography>
+    </Box>
+  );
+}

frontend/src/components/tasks/AddTaskDialog.tsx

@@ -0,0 +1,75 @@
+/**
+ * The "and this too" you type at 9am.
+ *
+ * The draft lives here rather than in the page: it is this dialog's business and
+ * nothing else ever reads it.
+ */
+import { useState } from "react";
+import {
+  Button,
+  Dialog,
+  DialogActions,
+  DialogContent,
+  DialogTitle,
+  Stack,
+  TextField,
+  Typography,
+} from "@mui/material";
+
+import { api } from "../../lib/api";
+
+export default function AddTaskDialog({
+  open,
+  onClose,
+  onCreated,
+}: {
+  open: boolean;
+  onClose: () => void;
+  onCreated: () => Promise<void>;
+}) {
+  const [draft, setDraft] = useState({ title: "", due_date: "" });
+
+  return (
+    <Dialog open={open} onClose={onClose} fullWidth maxWidth="xs">
+      <DialogTitle>New task</DialogTitle>
+      <DialogContent>
+        <Stack spacing={2} sx={{ mt: 1 }}>
+          <TextField
+            autoFocus
+            label="What needs doing?"
+            value={draft.title}
+            onChange={(event) => setDraft({ ...draft, title: event.target.value })}
+          />
+          <TextField
+            label="Due date"
+            type="date"
+            InputLabelProps={{ shrink: true }}
+            value={draft.due_date}
+            onChange={(event) => setDraft({ ...draft, due_date: event.target.value })}
+          />
+          <Typography variant="caption" color="text.secondary">
+            Local tasks live only here, so they are the one kind you can delete.
+          </Typography>
+        </Stack>
+      </DialogContent>
+      <DialogActions>
+        <Button onClick={onClose}>Cancel</Button>
+        <Button
+          variant="contained"
+          disabled={!draft.title.trim()}
+          onClick={async () => {
+            await api.post("/api/tasks", {
+              title: draft.title.trim(),
+              due_date: draft.due_date || null,
+            });
+            setDraft({ title: "", due_date: "" });
+            onClose();
+            await onCreated();
+          }}
+        >
+          Add
+        </Button>
+      </DialogActions>
+    </Dialog>
+  );
+}

frontend/src/components/tasks/SourceFilterTree.tsx

@@ -0,0 +1,156 @@
+/**
+ * Hide whole categories of work: a source, or one project inside it.
+ *
+ * The set it edits holds **hidden** keys, never visible ones, so a Jira project
+ * that first appears after a refresh shows up rather than being filtered out by
+ * a set written last week. See `isHidden` in `lib/calendar.ts`.
+ *
+ * Switching a source off disables its projects rather than silently unticking
+ * them: the parent governs, and switching it back on restores the whole subtree
+ * instead of leaving ghosts from whatever was unticked before.
+ */
+import { useMemo, useState } from "react";
+import {
+  Box,
+  Button,
+  Checkbox,
+  Divider,
+  Popover,
+  Stack,
+  Typography,
+} from "@mui/material";
+import FilterListIcon from "@mui/icons-material/FilterList";
+
+import { buildFilterTree, type CalendarItem } from "../../lib/calendar";
+
+export default function SourceFilterTree({
+  items,
+  hidden,
+  onChange,
+}: {
+  /** The *unfiltered* list — the counts have to describe what is there. */
+  items: CalendarItem[];
+  hidden: string[];
+  onChange: (next: string[]) => void;
+}) {
+  const [anchor, setAnchor] = useState<HTMLElement | null>(null);
+  const tree = useMemo(() => buildFilterTree(items), [items]);
+  const hiddenSet = useMemo(() => new Set(hidden), [hidden]);
+
+  const setHidden = (key: string, isHidden: boolean, alsoClear: string[] = []) => {
+    const next = new Set(hiddenSet);
+    if (isHidden) next.add(key);
+    else next.delete(key);
+    for (const extra of alsoClear) next.delete(extra);
+    onChange([...next]);
+  };
+
+  return (
+    <>
+      <Button
+        size="small"
+        variant="outlined"
+        startIcon={<FilterListIcon sx={{ fontSize: 16 }} />}
+        onClick={(event) => setAnchor(event.currentTarget)}
+      >
+        {hidden.length ? `Filter (${hidden.length} hidden)` : "Filter"}
+      </Button>
+
+      <Popover
+        open={anchor !== null}
+        anchorEl={anchor}
+        onClose={() => setAnchor(null)}
+        anchorOrigin={{ vertical: "bottom", horizontal: "left" }}
+        slotProps={{ paper: { sx: { mt: 0.5, minWidth: 260, maxHeight: 420 } } }}
+      >
+        <Box sx={{ p: 2 }}>
+          <Stack direction="row" alignItems="center" sx={{ mb: 1 }}>
+            <Typography variant="overline" color="text.secondary">
+              Show
+            </Typography>
+            <Box sx={{ flexGrow: 1 }} />
+            <Button size="small" disabled={hidden.length === 0} onClick={() => onChange([])}>
+              Reset
+            </Button>
+          </Stack>
+          <Divider sx={{ mb: 1 }} />
+
+          {tree.length === 0 && (
+            <Typography variant="body2" color="text.secondary">
+              Nothing to filter yet.
+            </Typography>
+          )}
+
+          {tree.map((node) => {
+            const sourceHidden = hiddenSet.has(node.key);
+            return (
+              <Box key={node.key} sx={{ mb: 0.5 }}>
+                <FilterRow
+                  label={node.label}
+                  count={node.count}
+                  checked={!sourceHidden}
+                  bold
+                  onChange={(visible) =>
+                    setHidden(
+                      node.key,
+                      !visible,
+                      // Turning a source back on restores its projects with it.
+                      visible ? node.children.map((child) => child.key) : [],
+                    )
+                  }
+                />
+                {node.children.map((child) => (
+                  <FilterRow
+                    key={child.key}
+                    label={child.label}
+                    count={child.count}
+                    indent
+                    disabled={sourceHidden}
+                    checked={!sourceHidden && !hiddenSet.has(child.key)}
+                    onChange={(visible) => setHidden(child.key, !visible)}
+                  />
+                ))}
+              </Box>
+            );
+          })}
+        </Box>
+      </Popover>
+    </>
+  );
+}
+
+function FilterRow({
+  label,
+  count,
+  checked,
+  onChange,
+  indent = false,
+  bold = false,
+  disabled = false,
+}: {
+  label: string;
+  count: number;
+  checked: boolean;
+  onChange: (visible: boolean) => void;
+  indent?: boolean;
+  bold?: boolean;
+  disabled?: boolean;
+}) {
+  return (
+    <Stack
+      direction="row"
+      alignItems="center"
+      spacing={1}
+      sx={{ pl: indent ? 3 : 0, cursor: disabled ? "default" : "pointer", opacity: disabled ? 0.45 : 1 }}
+      onClick={() => !disabled && onChange(!checked)}
+    >
+      <Checkbox size="small" checked={checked} disabled={disabled} sx={{ p: 0.5 }} />
+      <Typography variant="body2" noWrap sx={{ flexGrow: 1, minWidth: 0, fontWeight: bold ? 600 : 400 }}>
+        {label}
+      </Typography>
+      <Typography variant="caption" color="text.secondary" sx={{ fontVariantNumeric: "tabular-nums" }}>
+        {count}
+      </Typography>
+    </Stack>
+  );
+}

frontend/src/components/tasks/TaskList.tsx

@@ -0,0 +1,88 @@
+/**
+ * Everything you owe, grouped by deadline — the original Tasks view.
+ *
+ * Moved out of `TasksPage.tsx` when the page grew a calendar beside it. The
+ * grouping and the empty state are unchanged; the one new thing is that the
+ * list filters `is_done`/`stale` itself rather than trusting the URL it was
+ * fetched from, because the page now asks the backend for history so the
+ * calendar has something to draw.
+ */
+import { useMemo } from "react";
+import { Box, Divider, Stack, Typography } from "@mui/material";
+
+import { Panel, SectionTitle } from "../Layout";
+import { BUCKET_LABEL } from "../../lib/format";
+import type { Task } from "../../lib/types";
+import TaskRow from "./TaskRow";
+
+const BUCKETS: Task["bucket"][] = ["overdue", "today", "active", "upcoming", "someday"];
+
+/** What the list has always shown: open, still offered by its source. */
+export function openTasks(tasks: Task[]): Task[] {
+  return tasks.filter((task) => !task.is_done && !task.stale);
+}
+
+export default function TaskList({
+  tasks,
+  onPin,
+  onStart,
+  onDelete,
+}: {
+  tasks: Task[];
+  onPin: (task: Task) => Promise<void>;
+  onStart: (task: Task) => Promise<void>;
+  onDelete: (task: Task) => Promise<void>;
+}) {
+  const grouped = useMemo(() => {
+    const map: Record<string, Task[]> = { overdue: [], today: [], active: [], upcoming: [], someday: [] };
+    for (const task of tasks) {
+      const bucket = task && task.bucket && map[task.bucket] ? task.bucket : "someday";
+      map[bucket].push(task);
+    }
+    return map;
+  }, [tasks]);
+
+  if (tasks.length === 0) {
+    return (
+      <Panel>
+        <Typography variant="h6" sx={{ mb: 1 }}>
+          Nothing on the list
+        </Typography>
+        <Typography variant="body2" color="text.secondary">
+          Connect Jira, Todoist or Google Tasks in Settings → Task sources, or add something yourself.
+        </Typography>
+      </Panel>
+    );
+  }
+
+  return (
+    <>
+      {BUCKETS.map((bucket) =>
+        grouped[bucket].length ? (
+          <Box key={bucket} sx={{ mb: 4 }}>
+            <SectionTitle
+              action={
+                <Typography variant="caption" color="text.secondary">
+                  {grouped[bucket].length}
+                </Typography>
+              }
+            >
+              {BUCKET_LABEL[bucket]}
+            </SectionTitle>
+            <Stack divider={<Divider />}>
+              {grouped[bucket].map((task) => (
+                <TaskRow
+                  key={task.id}
+                  task={task}
+                  onPin={() => onPin(task)}
+                  onStart={() => onStart(task)}
+                  onDelete={() => onDelete(task)}
+                />
+              ))}
+            </Stack>
+          </Box>
+        ) : null,
+      )}
+    </>
+  );
+}

frontend/src/components/tasks/TaskRow.tsx

@@ -0,0 +1,120 @@
+/**
+ * One task, as a row of hairline-separated facts.
+ *
+ * Moved out of `TasksPage.tsx` unchanged when the page grew a second view; the
+ * calendar's day popover renders the same row, so a task reads identically
+ * wherever you meet it.
+ */
+import { Box, IconButton, Link, Stack, Tooltip, Typography } from "@mui/material";
+import DeleteOutlineIcon from "@mui/icons-material/DeleteOutline";
+import OpenInNewIcon from "@mui/icons-material/OpenInNew";
+import PlayArrowOutlinedIcon from "@mui/icons-material/PlayArrowOutlined";
+import StarIcon from "@mui/icons-material/Star";
+import StarBorderIcon from "@mui/icons-material/StarBorder";
+
+import type { Task } from "../../lib/types";
+
+export const BUCKET_COLOR: Record<string, string> = {
+  overdue: "error.main",
+  today: "warning.main",
+  active: "success.main",
+  upcoming: "text.disabled",
+  someday: "divider",
+};
+
+export default function TaskRow({
+  task,
+  onPin,
+  onStart,
+  onDelete,
+}: {
+  task: Task;
+  onPin: () => Promise<void>;
+  onStart: () => Promise<void>;
+  onDelete: () => Promise<void>;
+}) {
+  return (
+    <Stack
+      direction="row"
+      spacing={2}
+      alignItems="center"
+      sx={{ py: 1.5, "&:hover .row-actions": { opacity: 1 } }}
+    >
+      <Box sx={{ width: 2, alignSelf: "stretch", bgcolor: BUCKET_COLOR[task.bucket] ?? BUCKET_COLOR.someday, borderRadius: 1 }} />
+
+      <Box sx={{ flexGrow: 1, minWidth: 0 }}>
+        <Stack direction="row" spacing={1} alignItems="center">
+          <Typography
+            variant="body1"
+            noWrap
+            sx={{
+              fontWeight: task.pinned ? 600 : 400,
+              textDecoration: task.is_done ? "line-through" : "none",
+              color: task.is_done ? "text.disabled" : "text.primary",
+            }}
+          >
+            {task.title}
+          </Typography>
+          {task.url && (
+            <Link href={task.url} target="_blank" rel="noreferrer" sx={{ display: "inline-flex", color: "text.disabled" }}>
+              <OpenInNewIcon sx={{ fontSize: 14 }} />
+            </Link>
+          )}
+        </Stack>
+        <Stack direction="row" spacing={1.5} sx={{ mt: 0.25, flexWrap: "wrap", rowGap: 0.5 }}>
+          <Typography variant="caption" color="text.secondary">
+            {task.source_label}
+          </Typography>
+          {task.project && (
+            <Typography variant="caption" color="text.secondary">
+              {task.project}
+            </Typography>
+          )}
+          {task.status && (
+            <Typography variant="caption" color="text.secondary">
+              {task.status}
+            </Typography>
+          )}
+          {task.priority && (
+            <Typography variant="caption" color="text.secondary">
+              {task.priority}
+            </Typography>
+          )}
+          {/* `days_overdue` is computed against today, so it is only the truth for
+              something still open. A stale laundry slot carries one forever. */}
+          {task.days_overdue > 0 && !task.is_done && !task.stale ? (
+            <Typography variant="caption" color="error.main" sx={{ fontWeight: 600 }}>
+              {task.days_overdue}d overdue
+            </Typography>
+          ) : (
+            task.due_date && (
+              <Typography variant="caption" color="text.secondary">
+                due {task.due_date}
+              </Typography>
+            )
+          )}
+        </Stack>
+      </Box>
+
+      <Stack direction="row" spacing={0.5} className="row-actions" sx={{ opacity: { xs: 1, md: 0.25 }, transition: "opacity .15s" }}>
+        <Tooltip title={task.pinned ? "Unpin" : "Pin to the top"}>
+          <IconButton size="small" onClick={() => void onPin()}>
+            {task.pinned ? <StarIcon sx={{ fontSize: 17 }} /> : <StarBorderIcon sx={{ fontSize: 17 }} />}
+          </IconButton>
+        </Tooltip>
+        <Tooltip title="Start a pomodoro on this">
+          <IconButton size="small" onClick={() => void onStart()}>
+            <PlayArrowOutlinedIcon sx={{ fontSize: 18 }} />
+          </IconButton>
+        </Tooltip>
+        {task.source === "local" && (
+          <Tooltip title="Delete">
+            <IconButton size="small" onClick={() => void onDelete()}>
+              <DeleteOutlineIcon sx={{ fontSize: 17 }} />
+            </IconButton>
+          </Tooltip>
+        )}
+      </Stack>
+    </Stack>
+  );
+}

frontend/src/lib/calendar.ts

@@ -0,0 +1,443 @@
+/**
+ * The month grid, and the two filters that make it readable.
+ *
+ * A calendar of *tasks* is not a calendar of events: nothing here has a time of
+ * day, only a `start_date` and a `due_date`, so every item is a whole-day bar and
+ * the only interesting layout question is which lane it sits in.
+ *
+ * Three rules exist because of what the sources actually return rather than for
+ * their own sake:
+ *
+ *  * **Long tasks are measured on their true span, before clipping.** Jira hands
+ *    back every open issue with whatever "Start date" the custom field holds,
+ *    which is routinely months old. Clipping to the week first would make a
+ *    fifteen-day bar look like seven days in each of three rows and it would
+ *    never trip the filter — which is the entire point of the filter.
+ *  * **The filter stores hidden keys, never visible ones.** A Jira project that
+ *    appears for the first time after a refresh must show up, not be silently
+ *    filtered out because it was absent from a set written last week.
+ *  * **A due date is what makes a task plottable** — see `spanOf`.
+ *
+ * Nothing here may key off `bucket` or `days_overdue`: the backend computes both
+ * against *today* (`_bucket_of` in `backend/app/api/routes_tasks.py`), so a stale
+ * laundry slot from March reports `overdue` with a `days_overdue` that grows
+ * forever. In a cell you are looking at in a past month that is noise — style
+ * from the cell's own date against `is_done` and `stale` instead.
+ *
+ * `android/core/src/main/kotlin/tech/kadence/core/Calendar.kt` is a literal port
+ * of this file, and `CalendarTest` asserts the outputs this produces.
+ * `CalendarParityTest` reads `LONG_TASK_DAYS` straight out of this source.
+ */
+
+/** Longer than this many days and a bar is "long". Mirrored in `Calendar.kt`. */
+export const LONG_TASK_DAYS = 7;
+
+/**
+ * What the layout needs off a task. `Task` satisfies this structurally, so
+ * callers pass their tasks straight in.
+ */
+export interface CalendarItem {
+  id: number;
+  source: string;
+  source_label: string;
+  project: string | null;
+  start_date: string | null;
+  due_date: string | null;
+}
+
+export interface Span {
+  start: string;
+  end: string;
+  /** Inclusive length, so a one-day task is 1. */
+  days: number;
+}
+
+// --------------------------------------------------------------------------
+// Dates
+// --------------------------------------------------------------------------
+// ISO day strings compare lexicographically in calendar order, so ordering and
+// overlap tests never need a Date at all. Only arithmetic does.
+
+/** `new Date("2026-10-19")` is parsed as UTC; this is the local-midnight form. */
+function parseISO(iso: string): Date {
+  return new Date(`${iso}T00:00:00`);
+}
+
+function toISO(date: Date): string {
+  const month = `${date.getMonth() + 1}`.padStart(2, "0");
+  const day = `${date.getDate()}`.padStart(2, "0");
+  return `${date.getFullYear()}-${month}-${day}`;
+}
+
+/** Whole days from `from` to `to`; rounded, so a DST day is still one day. */
+export function diffDays(from: string, to: string): number {
+  return Math.round((parseISO(to).getTime() - parseISO(from).getTime()) / 86_400_000);
+}
+
+export function addDays(iso: string, days: number): string {
+  const date = parseISO(iso);
+  return toISO(new Date(date.getFullYear(), date.getMonth(), date.getDate() + days));
+}
+
+export function todayISO(): string {
+  return toISO(new Date());
+}
+
+// --------------------------------------------------------------------------
+// Spans
+// --------------------------------------------------------------------------
+
+function span(start: string, end: string): Span {
+  return { start, end, days: diffDays(start, end) + 1 };
+}
+
+/**
+ * Where a task sits on the calendar, or null if it cannot be plotted.
+ *
+ * **A due date is what makes a task plottable.** A task with only a start date
+ * is deliberately *not* drawn, which is the one rule here that costs something
+ * and is worth the cost: the Jira JQL in `backend/app/sources/jira.py:77`
+ * selects issues whose start date is today-or-earlier with no lower bound, and
+ * Jira issues very often carry a start date and no due date. Drawing those on
+ * their start day puts work the user thinks of as "now" into a cell four months
+ * back — a confident wrong answer, which is worse than an honest absence. They
+ * come back as `undated` instead and get their own list.
+ *
+ * A due date *before* the start date is bad data — Jira permits it — and
+ * collapses to the deadline, because the deadline is the half that matters.
+ */
+export function spanOf(item: CalendarItem): Span | null {
+  const due = item.due_date;
+  if (!due) return null;
+  const start = item.start_date;
+  if (!start || due < start) return span(due, due);
+  return span(start, due);
+}
+
+export function isLong(value: Span): boolean {
+  return value.days > LONG_TASK_DAYS;
+}
+
+// --------------------------------------------------------------------------
+// The grid
+// --------------------------------------------------------------------------
+
+/**
+ * The weeks a month needs — five or six, never a fixed six.
+ *
+ * October 2026 starts on a Thursday and ends on a Saturday, so Monday-first it
+ * runs 28 September to 1 November in five rows. Padding that to six would hang
+ * an empty week off the bottom of the page.
+ *
+ * `month` is 1-12.
+ */
+export function monthGrid(year: number, month: number, weekStartsMonday: boolean): string[][] {
+  const first = new Date(year, month - 1, 1);
+  const weekday = first.getDay();
+  const offset = weekStartsMonday ? (weekday + 6) % 7 : weekday;
+  const lastDay = new Date(year, month, 0).getDate();
+
+  const weeks: string[][] = [];
+  let cursor = 1 - offset;
+  while (cursor <= lastDay) {
+    const row: string[] = [];
+    for (let index = 0; index < 7; index += 1) {
+      row.push(toISO(new Date(year, month - 1, cursor + index)));
+    }
+    weeks.push(row);
+    cursor += 7;
+  }
+  return weeks;
+}
+
+const WEEKDAYS_FROM_MONDAY = ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"];
+
+export function weekdayLabels(weekStartsMonday: boolean): string[] {
+  if (weekStartsMonday) return [...WEEKDAYS_FROM_MONDAY];
+  return [WEEKDAYS_FROM_MONDAY[6], ...WEEKDAYS_FROM_MONDAY.slice(0, 6)];
+}
+
+// --------------------------------------------------------------------------
+// Lane packing
+// --------------------------------------------------------------------------
+
+export interface Bar {
+  id: number;
+  lane: number;
+  /** Inclusive column indices into the week, 0-6. */
+  startCol: number;
+  endCol: number;
+  /** The task began before this week / ends after it — square that edge off. */
+  continuesLeft: boolean;
+  continuesRight: boolean;
+}
+
+export interface WeekLayout {
+  dates: string[];
+  bars: Bar[];
+  /** Per column, how many tasks this week could not draw — the "+N" counts. */
+  overflow: number[];
+  /** Lanes actually drawn, so a row can size itself to its content. */
+  lanes: number;
+  /** Whether any day in this week needs the "+N" strip under the bars. */
+  hasOverflow: boolean;
+}
+
+interface Placed {
+  item: CalendarItem;
+  span: Span;
+}
+
+/**
+ * Lay out a whole month, keeping a multi-week bar in one lane throughout.
+ *
+ * This has to be a month-at-a-time function rather than a week-at-a-time one,
+ * because the lane a continuing bar occupies is information that flows from one
+ * week to the next. Packing each week independently — however the segments are
+ * sorted — lets a bar step between lanes halfway along. With A spanning
+ * 2 to 18 March and B spanning 9 March to 2 April, A owns lane 0 in the first
+ * week; in the second both clip to Monday, and *any* tie-break that prefers B
+ * (longest-first does) moves A down to lane 1 mid-bar.
+ *
+ * So, FullCalendar's rule, in two phases per week:
+ *
+ *  1. **Continuations keep the lane they already hold.** This can never
+ *     collide: every bar continuing into this week covers its first day, so
+ *     every pair of them also overlapped on the previous week's last day, and
+ *     they were given distinct lanes there.
+ *  2. **Everything else competes** for the lowest free lane, longest first.
+ *
+ * Note that `continuesLeft` is geometry (the span starts before this week) while
+ * "is a continuation" is bookkeeping (we already gave it a lane). They are not
+ * the same, and conflating them breaks the first visible week: a bar running in
+ * from before the grid has no lane yet, so it competes as a newcomer while still
+ * drawing with an open left edge.
+ *
+ * A task that finds no free lane is not drawn and is counted against **every**
+ * day it covers, because each cell's "+2" has to describe that cell — it is what
+ * opens when you click it. It is deliberately given no lane, so next week it
+ * competes again and may well win one.
+ *
+ * `maxLanes` is a per-client layout budget, not a shared rule: it is a required
+ * argument with no default so that neither client can drift into its own idea of
+ * what "the" value is.
+ */
+export function layoutMonth(
+  weeks: string[][],
+  items: CalendarItem[],
+  maxLanes: number,
+): WeekLayout[] {
+  const placed: Placed[] = [];
+  for (const item of items) {
+    const value = spanOf(item);
+    if (value) placed.push({ item, span: value });
+  }
+
+  const laneOf = new Map<number, number>();
+  const layouts: WeekLayout[] = [];
+
+  for (const week of weeks) {
+    const weekStart = week[0];
+    const weekEnd = week[6];
+    const inWeek = placed.filter((entry) => entry.span.start <= weekEnd && entry.span.end >= weekStart);
+
+    const occupied: boolean[][] = [];
+    for (let lane = 0; lane < maxLanes; lane += 1) occupied.push(new Array(7).fill(false));
+    const bars: Bar[] = [];
+    const overflow = new Array(7).fill(0);
+
+    const claim = (lane: number, from: number, to: number) => {
+      for (let column = from; column <= to; column += 1) occupied[lane][column] = true;
+    };
+    const free = (lane: number, from: number, to: number) => {
+      for (let column = from; column <= to; column += 1) {
+        if (occupied[lane][column]) return false;
+      }
+      return true;
+    };
+    const columns = (entry: Placed): [number, number] => [
+      entry.span.start < weekStart ? 0 : diffDays(weekStart, entry.span.start),
+      entry.span.end > weekEnd ? 6 : diffDays(weekStart, entry.span.end),
+    ];
+    const barFor = (entry: Placed, lane: number, from: number, to: number): Bar => ({
+      id: entry.item.id,
+      lane,
+      startCol: from,
+      endCol: to,
+      continuesLeft: entry.span.start < weekStart,
+      continuesRight: entry.span.end > weekEnd,
+    });
+
+    // Phase 1 — continuations reclaim their lane, in lane order.
+    const continuing = inWeek
+      .filter((entry) => entry.span.start < weekStart && laneOf.has(entry.item.id))
+      .sort((a, b) => (laneOf.get(a.item.id) as number) - (laneOf.get(b.item.id) as number));
+    for (const entry of continuing) {
+      const lane = laneOf.get(entry.item.id) as number;
+      const [from, to] = columns(entry);
+      claim(lane, from, to);
+      bars.push(barFor(entry, lane, from, to));
+    }
+
+    // Phase 2 — the rest take the lowest lane that fits.
+    const seen = new Set(continuing.map((entry) => entry.item.id));
+    const starting = inWeek
+      .filter((entry) => !seen.has(entry.item.id))
+      .sort(
+        (a, b) =>
+          b.span.days - a.span.days ||
+          a.span.start.localeCompare(b.span.start) ||
+          a.item.id - b.item.id,
+      );
+    for (const entry of starting) {
+      const [from, to] = columns(entry);
+      let lane = -1;
+      for (let candidate = 0; candidate < maxLanes; candidate += 1) {
+        if (free(candidate, from, to)) {
+          lane = candidate;
+          break;
+        }
+      }
+      if (lane < 0) {
+        for (let column = from; column <= to; column += 1) overflow[column] += 1;
+        continue;
+      }
+      claim(lane, from, to);
+      laneOf.set(entry.item.id, lane);
+      bars.push(barFor(entry, lane, from, to));
+    }
+
+    const lanes = bars.reduce((most, bar) => Math.max(most, bar.lane + 1), 0);
+    layouts.push({
+      dates: week,
+      bars,
+      overflow,
+      lanes,
+      hasOverflow: overflow.some((count) => count > 0),
+    });
+  }
+
+  return layouts;
+}
+
+/** `shiftMonth(2026, 1, -1)` is December 2025. `month` is 1-12 throughout. */
+export function shiftMonth(year: number, month: number, delta: number): [number, number] {
+  const zero = year * 12 + (month - 1) + delta;
+  return [Math.floor(zero / 12), (zero % 12) + 1];
+}
+
+// --------------------------------------------------------------------------
+// The type filter
+// --------------------------------------------------------------------------
+
+export interface FilterNode {
+  /** `"jira"` for a source, `"jira/MIPT"` for one of its projects. */
+  key: string;
+  label: string;
+  count: number;
+  children: FilterNode[];
+}
+
+function projectKey(source: string, project: string): string {
+  return `${source}/${project}`;
+}
+
+/**
+ * Sources, each expanded into the projects seen under it.
+ *
+ * Only tasks that *name* a project get a child node, so a source's children can
+ * sum to less than its own count; those tasks are reachable by hiding the whole
+ * source, which is the honest thing a "(none)" bucket would only dress up.
+ */
+export function buildFilterTree(items: CalendarItem[]): FilterNode[] {
+  const sources = new Map<string, { label: string; count: number; projects: Map<string, number> }>();
+
+  for (const item of items) {
+    let entry = sources.get(item.source);
+    if (!entry) {
+      entry = { label: item.source_label || item.source, count: 0, projects: new Map() };
+      sources.set(item.source, entry);
+    }
+    entry.count += 1;
+    const project = (item.project ?? "").trim();
+    if (project) entry.projects.set(project, (entry.projects.get(project) ?? 0) + 1);
+  }
+
+  return [...sources.entries()]
+    .sort((a, b) => a[1].label.localeCompare(b[1].label))
+    .map(([source, entry]) => ({
+      key: source,
+      label: entry.label,
+      count: entry.count,
+      children: [...entry.projects.entries()]
+        .sort((a, b) => a[0].localeCompare(b[0]))
+        .map(([project, count]) => ({
+          key: projectKey(source, project),
+          label: project,
+          count,
+          children: [],
+        })),
+    }));
+}
+
+/** Hiding a source hides its projects with it. */
+export function isHidden(item: CalendarItem, hidden: ReadonlySet<string>): boolean {
+  if (hidden.has(item.source)) return true;
+  const project = (item.project ?? "").trim();
+  return project.length > 0 && hidden.has(projectKey(item.source, project));
+}
+
+export interface CalendarModel<T> {
+  /** What the grid draws. */
+  visible: T[];
+  /** Passing the type filter but carrying no due date, so nowhere to draw them. */
+  undated: T[];
+  /** Spanning more than a week — the toggle's count, whether or not it is on. */
+  longCount: number;
+}
+
+/**
+ * One pass over the list for everything the toolbar and the grid need.
+ *
+ * `longCount` deliberately ignores `showLong`, so the toggle's own label does
+ * not change the moment you press it.
+ */
+export function buildModel<T extends CalendarItem>(
+  items: T[],
+  hidden: ReadonlySet<string>,
+  showLong: boolean,
+): CalendarModel<T> {
+  const visible: T[] = [];
+  const undated: T[] = [];
+  let longCount = 0;
+
+  for (const item of items) {
+    if (isHidden(item, hidden)) continue;
+    const value = spanOf(item);
+    if (!value) {
+      undated.push(item);
+      continue;
+    }
+    if (isLong(value)) {
+      longCount += 1;
+      if (!showLong) continue;
+    }
+    visible.push(item);
+  }
+
+  return { visible, undated, longCount };
+}
+
+/** The tasks touching one day, in the order the grid stacks them. */
+export function itemsOnDay<T extends CalendarItem>(items: T[], day: string): T[] {
+  return items
+    .filter((item) => {
+      const value = spanOf(item);
+      return value !== null && value.start <= day && value.end >= day;
+    })
+    .sort((a, b) => {
+      const left = spanOf(a) as Span;
+      const right = spanOf(b) as Span;
+      return left.start.localeCompare(right.start) || right.days - left.days || a.id - b.id;
+    });
+}

frontend/src/pages/TasksPage.tsx

@@ -1,9 +1,16 @@
 /**
- * Everything you owe, from every source, grouped by deadline.
+ * Everything you owe, from every source — as a list, or as a month.
  *
  * There is no checkbox. A task is closed in Jira, Todoist or Google Tasks —
  * wherever it lives — and the next refresh notices and credits it to the day.
  * Two places to tick something off is two places to be wrong.
+ *
+ * The page asks the backend for **done and stale rows too**, because the
+ * calendar's whole point is that a past month shows what actually happened. The
+ * list therefore filters `is_done`/`stale` itself rather than trusting the URL
+ * it was fetched from, and the source buttons are counted from that filtered
+ * list — `sources` and `counts` in the response now describe the archive, not
+ * the work in front of you.
  */
 import { useMemo, useState } from "react";
 import {
@@ -13,51 +20,43 @@ import {
   Button,
   Chip,
   Collapse,
-  Dialog,
-  DialogActions,
-  DialogContent,
-  DialogTitle,
   Divider,
-  IconButton,
   LinearProgress,
-  Link,
   Stack,
-  TextField,
   ToggleButton,
   ToggleButtonGroup,
-  Tooltip,
   Typography,
 } from "@mui/material";
-import DeleteOutlineIcon from "@mui/icons-material/DeleteOutline";
-import OpenInNewIcon from "@mui/icons-material/OpenInNew";
-import PlayArrowOutlinedIcon from "@mui/icons-material/PlayArrowOutlined";
-import StarIcon from "@mui/icons-material/Star";
-import StarBorderIcon from "@mui/icons-material/StarBorder";
 import { useNavigate } from "react-router-dom";
 
 import { PageHeader, Panel, SectionTitle } from "../components/Layout";
+import AddTaskDialog from "../components/tasks/AddTaskDialog";
+import SourceFilterTree from "../components/tasks/SourceFilterTree";
+import TaskList, { openTasks } from "../components/tasks/TaskList";
+import TaskRow from "../components/tasks/TaskRow";
+import TaskCalendar from "../components/calendar/TaskCalendar";
 import { api } from "../lib/api";
-import { BUCKET_LABEL } from "../lib/format";
-import { useResource } from "../lib/hooks";
+import { buildModel } from "../lib/calendar";
+import { useLocalState, useResource } from "../lib/hooks";
 import type { RefreshResult, Task, TaskListResponse } from "../lib/types";
 
-const BUCKETS: Task["bucket"][] = ["overdue", "today", "active", "upcoming", "someday"];
-const BUCKET_COLOR: Record<string, string> = {
-  overdue: "error.main",
-  today: "warning.main",
-  active: "success.main",
-  upcoming: "text.disabled",
-  someday: "divider",
-};
+/** History included: the calendar draws past months, the list filters it back out. */
+const TASKS_PATH = "/api/tasks?include_done=true&include_stale=true";
 
 export default function TasksPage({ onToast }: { onToast: (message: string) => void }) {
   const navigate = useNavigate();
-  const tasks = useResource<TaskListResponse>("/api/tasks", 60000);
+  const tasks = useResource<TaskListResponse>(TASKS_PATH, 60000);
   const [refreshing, setRefreshing] = useState(false);
   const [sourceStatus, setSourceStatus] = useState<RefreshResult["sources"] | null>(null);
   const [filter, setFilter] = useState("all");
   const [addOpen, setAddOpen] = useState(false);
-  const [draft, setDraft] = useState({ title: "", due_date: "" });
+
+  // Per-device UI preferences. `useLocalState` JSON-stringifies, and a `Set`
+  // stringifies to `{}` — so the hidden keys are persisted as an array and the
+  // set is derived.
+  const [view, setView] = useLocalState<"list" | "calendar">("kadence.tasks.view", "list");
+  const [hiddenKeys, setHiddenKeys] = useLocalState<string[]>("kadence.tasks.hidden", []);
+  const [showLong, setShowLong] = useLocalState<boolean>("kadence.tasks.showLong", false);
 
   const refresh = async () => {
     setRefreshing(true);
@@ -79,19 +78,38 @@ export default function TasksPage({ onToast }: { onToast: (message: string) => v
     }
   };
 
-  const visible = useMemo(() => {
-    const all = tasks.data?.tasks ?? [];
-    return filter === "all" ? all : all.filter((task) => task.source === filter);
-  }, [tasks.data, filter]);
+  const onPin = async (task: Task) => {
+    await api.patch(`/api/tasks/${task.id}`, { pinned: !task.pinned });
+    await tasks.reload();
+  };
+  const onStart = async (task: Task) => {
+    await api.post("/api/timer/start", { kind: "work", task_id: task.id });
+    onToast(`Focusing on “${task.title}”`);
+    navigate("/");
+  };
+  const onDelete = async (task: Task) => {
+    await api.del(`/api/tasks/${task.id}`);
+    await tasks.reload();
+  };
 
-  const grouped = useMemo(() => {
-    const map: Record<string, Task[]> = { overdue: [], today: [], active: [], upcoming: [], someday: [] };
-    for (const task of visible) {
-      const bucket = task && task.bucket && map[task.bucket] ? task.bucket : "someday";
-      map[bucket].push(task);
-    }
-    return map;
-  }, [visible]);
+  const all = useMemo(() => tasks.data?.tasks ?? [], [tasks.data]);
+  const open = useMemo(() => openTasks(all), [all]);
+
+  // The response's `sources` now lists every source that ever had a row; the
+  // buttons have to describe what is actually on the list.
+  const openSources = useMemo(() => {
+    const labels = new Map<string, string>();
+    for (const task of open) labels.set(task.source, task.source_label || task.source);
+    return [...labels.entries()].sort((a, b) => a[1].localeCompare(b[1]));
+  }, [open]);
+
+  const listed = useMemo(
+    () => (filter === "all" ? open : open.filter((task) => task.source === filter)),
+    [open, filter],
+  );
+
+  const hiddenSet = useMemo(() => new Set(hiddenKeys), [hiddenKeys]);
+  const model = useMemo(() => buildModel(all, hiddenSet, showLong), [all, hiddenSet, showLong]);
 
   const failed = sourceStatus?.filter((item) => !item.ok) ?? [];
 
@@ -130,16 +148,31 @@ export default function TasksPage({ onToast }: { onToast: (message: string) => v
         <ToggleButtonGroup
           size="small"
           exclusive
-          value={filter}
-          onChange={(_event, value) => value && setFilter(value)}
+          value={view}
+          onChange={(_event, value) => value && setView(value as "list" | "calendar")}
         >
-          <ToggleButton value="all">All</ToggleButton>
-          {(tasks.data?.sources ?? []).map((source) => (
-            <ToggleButton key={source} value={source}>
-              {tasks.data?.tasks.find((task) => task.source === source)?.source_label ?? source}
-            </ToggleButton>
-          ))}
+          <ToggleButton value="list">List</ToggleButton>
+          <ToggleButton value="calendar">Calendar</ToggleButton>
         </ToggleButtonGroup>
+
+        {view === "list" ? (
+          <ToggleButtonGroup
+            size="small"
+            exclusive
+            value={filter}
+            onChange={(_event, value) => value && setFilter(value)}
+          >
+            <ToggleButton value="all">All</ToggleButton>
+            {openSources.map(([source, label]) => (
+              <ToggleButton key={source} value={source}>
+                {label}
+              </ToggleButton>
+            ))}
+          </ToggleButtonGroup>
+        ) : (
+          <SourceFilterTree items={all} hidden={hiddenKeys} onChange={setHiddenKeys} />
+        )}
+
         <Box sx={{ flexGrow: 1 }} />
         {sourceStatus && failed.length === 0 && (
           <Stack direction="row" spacing={1} alignItems="center" sx={{ flexWrap: "wrap", rowGap: 1 }}>
@@ -150,182 +183,75 @@ export default function TasksPage({ onToast }: { onToast: (message: string) => v
         )}
       </Stack>
 
-      {tasks.data && visible.length === 0 && (
-        <Panel>
-          <Typography variant="h6" sx={{ mb: 1 }}>
-            Nothing on the list
-          </Typography>
-          <Typography variant="body2" color="text.secondary">
-            Connect Jira, Todoist or Google Tasks in Settings → Task sources, or add something yourself.
-          </Typography>
-        </Panel>
+      {view === "calendar" ? (
+        <>
+          <TaskCalendar
+            tasks={model.visible}
+            longCount={model.longCount}
+            showLong={showLong}
+            onShowLong={setShowLong}
+            onPin={onPin}
+            onStart={onStart}
+            onDelete={onDelete}
+          />
+          <UndatedSection tasks={model.undated} onPin={onPin} onStart={onStart} onDelete={onDelete} />
+        </>
+      ) : (
+        <TaskList tasks={listed} onPin={onPin} onStart={onStart} onDelete={onDelete} />
       )}
 
-      {BUCKETS.map((bucket) =>
-        grouped[bucket].length ? (
-          <Box key={bucket} sx={{ mb: 4 }}>
-            <SectionTitle
-              action={
-                <Typography variant="caption" color="text.secondary">
-                  {grouped[bucket].length}
-                </Typography>
-              }
-            >
-              {BUCKET_LABEL[bucket]}
-            </SectionTitle>
-            <Stack divider={<Divider />}>
-              {grouped[bucket].map((task) => (
-                <TaskRow
-                  key={task.id}
-                  task={task}
-                  onPin={async () => {
-                    await api.patch(`/api/tasks/${task.id}`, { pinned: !task.pinned });
-                    await tasks.reload();
-                  }}
-                  onStart={async () => {
-                    await api.post("/api/timer/start", { kind: "work", task_id: task.id });
-                    onToast(`Focusing on “${task.title}”`);
-                    navigate("/");
-                  }}
-                  onDelete={async () => {
-                    await api.del(`/api/tasks/${task.id}`);
-                    await tasks.reload();
-                  }}
-                />
-              ))}
-            </Stack>
-          </Box>
-        ) : null,
-      )}
-
-      <Dialog open={addOpen} onClose={() => setAddOpen(false)} fullWidth maxWidth="xs">
-        <DialogTitle>New task</DialogTitle>
-        <DialogContent>
-          <Stack spacing={2} sx={{ mt: 1 }}>
-            <TextField
-              autoFocus
-              label="What needs doing?"
-              value={draft.title}
-              onChange={(event) => setDraft({ ...draft, title: event.target.value })}
-            />
-            <TextField
-              label="Due date"
-              type="date"
-              InputLabelProps={{ shrink: true }}
-              value={draft.due_date}
-              onChange={(event) => setDraft({ ...draft, due_date: event.target.value })}
-            />
-            <Typography variant="caption" color="text.secondary">
-              Local tasks live only here, so they are the one kind you can delete.
-            </Typography>
-          </Stack>
-        </DialogContent>
-        <DialogActions>
-          <Button onClick={() => setAddOpen(false)}>Cancel</Button>
-          <Button
-            variant="contained"
-            disabled={!draft.title.trim()}
-            onClick={async () => {
-              await api.post("/api/tasks", {
-                title: draft.title.trim(),
-                due_date: draft.due_date || null,
-              });
-              setDraft({ title: "", due_date: "" });
-              setAddOpen(false);
-              await tasks.reload();
-            }}
-          >
-            Add
-          </Button>
-        </DialogActions>
-      </Dialog>
+      <AddTaskDialog open={addOpen} onClose={() => setAddOpen(false)} onCreated={tasks.reload} />
     </>
   );
 }
 
-function TaskRow({
-  task,
+/**
+ * The tasks a calendar cannot place: no due date, so no column to sit in.
+ *
+ * Jira keeps the same affordance and calls it the backlog. Collapsed by default
+ * — it is routinely the longest list on the page, and it is not what you opened
+ * a calendar to look at.
+ */
+function UndatedSection({
+  tasks,
   onPin,
   onStart,
   onDelete,
 }: {
-  task: Task;
-  onPin: () => Promise<void>;
-  onStart: () => Promise<void>;
-  onDelete: () => Promise<void>;
+  tasks: Task[];
+  onPin: (task: Task) => Promise<void>;
+  onStart: (task: Task) => Promise<void>;
+  onDelete: (task: Task) => Promise<void>;
 }) {
+  const [open, setOpen] = useState(false);
+  if (tasks.length === 0) return null;
+
   return (
-    <Stack
-      direction="row"
-      spacing={2}
-      alignItems="center"
-      sx={{ py: 1.5, "&:hover .row-actions": { opacity: 1 } }}
-    >
-      <Box sx={{ width: 2, alignSelf: "stretch", bgcolor: BUCKET_COLOR[task.bucket] ?? BUCKET_COLOR.someday, borderRadius: 1 }} />
-
-      <Box sx={{ flexGrow: 1, minWidth: 0 }}>
-        <Stack direction="row" spacing={1} alignItems="center">
-          <Typography variant="body1" noWrap sx={{ fontWeight: task.pinned ? 600 : 400 }}>
-            {task.title}
-          </Typography>
-          {task.url && (
-            <Link href={task.url} target="_blank" rel="noreferrer" sx={{ display: "inline-flex", color: "text.disabled" }}>
-              <OpenInNewIcon sx={{ fontSize: 14 }} />
-            </Link>
-          )}
-        </Stack>
-        <Stack direction="row" spacing={1.5} sx={{ mt: 0.25, flexWrap: "wrap", rowGap: 0.5 }}>
-          <Typography variant="caption" color="text.secondary">
-            {task.source_label}
-          </Typography>
-          {task.project && (
-            <Typography variant="caption" color="text.secondary">
-              {task.project}
-            </Typography>
-          )}
-          {task.status && (
-            <Typography variant="caption" color="text.secondary">
-              {task.status}
-            </Typography>
-          )}
-          {task.priority && (
-            <Typography variant="caption" color="text.secondary">
-              {task.priority}
-            </Typography>
-          )}
-          {task.days_overdue > 0 ? (
-            <Typography variant="caption" color="error.main" sx={{ fontWeight: 600 }}>
-              {task.days_overdue}d overdue
-            </Typography>
-          ) : (
-            task.due_date && (
-              <Typography variant="caption" color="text.secondary">
-                due {task.due_date}
-              </Typography>
-            )
-          )}
-        </Stack>
-      </Box>
-
-      <Stack direction="row" spacing={0.5} className="row-actions" sx={{ opacity: { xs: 1, md: 0.25 }, transition: "opacity .15s" }}>
-        <Tooltip title={task.pinned ? "Unpin" : "Pin to the top"}>
-          <IconButton size="small" onClick={() => void onPin()}>
-            {task.pinned ? <StarIcon sx={{ fontSize: 17 }} /> : <StarBorderIcon sx={{ fontSize: 17 }} />}
-          </IconButton>
-        </Tooltip>
-        <Tooltip title="Start a pomodoro on this">
-          <IconButton size="small" onClick={() => void onStart()}>
-            <PlayArrowOutlinedIcon sx={{ fontSize: 18 }} />
-          </IconButton>
-        </Tooltip>
-        {task.source === "local" && (
-          <Tooltip title="Delete">
-            <IconButton size="small" onClick={() => void onDelete()}>
-              <DeleteOutlineIcon sx={{ fontSize: 17 }} />
-            </IconButton>
-          </Tooltip>
-        )}
-      </Stack>
-    </Stack>
+    <Box sx={{ mt: 3 }}>
+      <SectionTitle
+        action={
+          <Button size="small" onClick={() => setOpen(!open)}>
+            {open ? "Hide" : "Show"}
+          </Button>
+        }
+      >
+        No due date ({tasks.length})
+      </SectionTitle>
+      <Collapse in={open}>
+        <Panel padded={false} sx={{ px: 2 }}>
+          <Stack divider={<Divider />}>
+            {tasks.map((task) => (
+              <TaskRow
+                key={task.id}
+                task={task}
+                onPin={() => onPin(task)}
+                onStart={() => onStart(task)}
+                onDelete={() => onDelete(task)}
+              />
+            ))}
+          </Stack>
+        </Panel>
+      </Collapse>
+    </Box>
   );
 }

frontend/src/pages/TimerPage.tsx

@@ -100,13 +100,22 @@ export default function TimerPage({
     [onToast, timer, today],
   );
 
-  const firing = useRef(false);
+  // Which interval we have already told the server to finish. Keyed by id, not a
+  // bare "in flight" flag: a poll issued just before the countdown ran out answers
+  // with the finished interval still running at 00:00, and a flag cleared by that
+  // reply fires `complete` a second time — onto the break `auto_next` has since
+  // started, which is a break that ends the instant it begins. An id is never
+  // reused, so the second attempt is simply never made.
+  const completed = useRef<number | null>(null);
   useEffect(() => {
-    if (!current || remaining > 0 || firing.current) return;
-    firing.current = true;
+    if (!current || remaining > 0 || completed.current === current.id) return;
+    completed.current = current.id;
     const wasWork = current.kind === "work";
     void (async () => {
-      const next = await call("/api/timer/complete", { auto_next: true });
+      const next = await call("/api/timer/complete", { auto_next: true, session_id: current.id });
+      // It never landed, so this interval is still owed a complete: let the next
+      // tick try again rather than leave the dial stuck at 00:00.
+      if (!next && completed.current === current.id) completed.current = null;
       const volume = settings?.pomodoro.alarm_volume ?? 70;
       if (settings?.pomodoro.alarm_sound ?? true) {
         wasWork ? sound.workDone(volume) : sound.breakDone(volume);
@@ -115,7 +124,6 @@ export default function TimerPage({
         notify(wasWork ? "Pomodoro complete" : "Break over", wasWork ? "Time for a break." : "Back to it.");
       }
       if (next?.celebration) onToast("Milestone reached — Telegram got a cheer");
-      firing.current = false;
     })();
   }, [remaining, current, call, settings, onToast]);
 
@@ -218,7 +226,13 @@ export default function TimerPage({
                   <Button
                     variant="contained"
                     disabled={busy}
-                    onClick={() => void call("/api/timer/complete", { auto_next: true }, "Interval finished")}
+                    onClick={() =>
+                      void call(
+                        "/api/timer/complete",
+                        { auto_next: true, session_id: current.id },
+                        "Interval finished",
+                      )
+                    }
                   >
                     Finish
                   </Button>