diff --git a/Codex Documentation/Current Software Plan/README.md b/Codex Documentation/Current Software Plan/README.md
index 74a00bb..27b9bca 100644
--- a/Codex Documentation/Current Software Plan/README.md	
+++ b/Codex Documentation/Current Software Plan/README.md	
@@ -30,7 +30,7 @@ Do not infer a new level name.
 3. `V1_BLOCK_03_Scheduling_Engine.md`
 4. `V1_BLOCK_04_Backlog_Quick_Capture.md`
 5. `V1_BLOCK_05_Recurring_Locked_Blocks.md`
-6. `V1_BLOCK_06_Task_Actions_State_Transitions.md`
+6. `V1_BLOCK_06_Task_Actions_State_Transitions_UPDATED.md`
 7. `V1_BLOCK_07_Child_Tasks.md`
 8. `V1_BLOCK_08_Today_Timeline_State.md`
 9. `V1_BLOCK_09_Persistence_Preparation.md`
diff --git a/Codex Documentation/Current Software Plan/V1_BLOCK_06_Task_Actions_State_Transitions.md b/Codex Documentation/Current Software Plan/V1_BLOCK_06_Task_Actions_State_Transitions.md
index 26e6f4c..e1a9c90 100644
--- a/Codex Documentation/Current Software Plan/V1_BLOCK_06_Task_Actions_State_Transitions.md	
+++ b/Codex Documentation/Current Software Plan/V1_BLOCK_06_Task_Actions_State_Transitions.md	
@@ -1,6 +1,9 @@
 # V1 Block 06 — Task Actions and State Transitions
 
-Status: Planned
+Status: Superseded by `V1_BLOCK_06_Task_Actions_State_Transitions_UPDATED.md`
+
+Use the updated Block 06 plan for remaining work. The updated plan inserts the
+Chunk 6.3 edge-case regression suite before required task state transitions.
 
 Purpose: Define and implement the safe, low-friction actions available from task cards.
 
diff --git a/Codex Documentation/Current Software Plan/V1_BLOCK_06_Task_Actions_State_Transitions_UPDATED.md b/Codex Documentation/Current Software Plan/V1_BLOCK_06_Task_Actions_State_Transitions_UPDATED.md
index 6f757f1..8f60499 100644
--- a/Codex Documentation/Current Software Plan/V1_BLOCK_06_Task_Actions_State_Transitions_UPDATED.md	
+++ b/Codex Documentation/Current Software Plan/V1_BLOCK_06_Task_Actions_State_Transitions_UPDATED.md	
@@ -85,7 +85,7 @@ BREAKPOINT: Stop here. Confirm `extra high` mode before implementing Chunk 6.3,
 
 Recommended Codex level: extra high
 
-Status: Planned
+Status: Completed
 
 Purpose:
 
@@ -236,6 +236,18 @@ Commit suggestion:
 test(tasks): add edge-case regression coverage before state transitions
 ```
 
+Execution notes:
+
+- Added `test/edge_case_regression_test.dart` as a dedicated Block 06.3 regression suite.
+- Covered task title trimming/validation, `copyWith(clearSchedule: true)`, ProjectProfile task creation validation, flexible insertion no-fit safety, push order/fixed-item preservation, explicit source-window rollover safety, stable backlog sorting, consistent backlog staleness timestamps, quick capture scheduling validation, locked overlay-domain data, locked-hour counters, action-service unsupported-type handling, duplicate-id safety, change metadata, and input-list immutability.
+- Added optional `sourceWindow` to `SchedulingEngine.rollOverUnfinishedFlexibleTasks` so day-end rollover can explicitly limit rolled tasks to the intended source day while preserving existing callers.
+- Updated backlog stale filtering to use the same creation-age basis as staleness markers; V1 still documents that a separate backlog-entered timestamp belongs to later persistence work.
+- Made `ProjectProfile.createTask` trim and reject blank titles, matching quick-capture validation.
+- Made backlog sorting stable for equal sort keys by preserving source-list order.
+- No Required Task States implementation was added in this chunk.
+- No Surprise Task Logging implementation was added in this chunk.
+- `dart format lib test`, `dart analyze`, `dart test`, and `git diff --check` passed.
+
 BREAKPOINT: Stop here. Confirm `medium` mode before implementing Chunk 6.4 required task state transitions.
 
 ## Chunk 6.4 — Required task states
diff --git a/Human Documentation/Starter Architecture Notes.md b/Human Documentation/Starter Architecture Notes.md
index 208ad31..a1d8b09 100644
--- a/Human Documentation/Starter Architecture Notes.md	
+++ b/Human Documentation/Starter Architecture Notes.md	
@@ -31,6 +31,14 @@ Future sync layer, if explicitly planned
 
 The scheduling core must never move locked or inflexible blocks during automatic rescheduling.
 
+Flexible end-of-day rollover should use an explicit source-day window when
+available. That prevents planned flexible tasks from future days from being
+pulled into tomorrow during recovery.
+
+Backlog staleness in the current V1 domain model uses task creation age for both
+the stale filter and green/blue/purple marker. A later MongoDB-backed
+persistence pass may add a separate backlog-entered timestamp, but the current
+core keeps the timestamp semantics consistent and database-independent.
 
 ## Persistence direction
 
diff --git a/lib/src/backlog.dart b/lib/src/backlog.dart
index 101e58e..6dcae62 100644
--- a/lib/src/backlog.dart
+++ b/lib/src/backlog.dart
@@ -1,4 +1,4 @@
- // Backlog query helpers for the ADHD scheduling core.
+// Backlog query helpers for the ADHD scheduling core.
 //
 // The backlog is not a separate database table in this starter model. It is a
 // view over tasks whose `Task.status` is `TaskStatus.backlog`. This file keeps
@@ -134,7 +134,11 @@ class BacklogView {
   /// Clock value supplied by the caller so age/staleness behavior is testable.
   final DateTime now;
 
-  /// Age since [Task.updatedAt] that qualifies for the `stale` filter.
+  /// Age since [Task.createdAt] that qualifies for the `stale` filter.
+  ///
+  /// V1 does not yet store a separate "entered backlog at" timestamp. Until
+  /// persistence adds that field, both stale filtering and visual staleness use
+  /// task creation age so they do not disagree after a task edit.
   final Duration staleAfter;
 
   /// Color-bucket threshold configuration for backlog aging indicators.
@@ -164,10 +168,28 @@ class BacklogView {
   /// reordered by a read operation. The final list is unmodifiable to make that
   /// intent explicit to callers.
   List<Task> sorted(BacklogSortKey sortKey) {
-    final sortedTasks = [...backlogTasks];
-    sortedTasks.sort((a, b) => _compareTasks(a, b, sortKey));
+    final sortedTasks = backlogTasks
+        .asMap()
+        .entries
+        .map(
+          (entry) => _IndexedTask(
+            task: entry.value,
+            originalIndex: entry.key,
+          ),
+        )
+        .toList(growable: false);
+    sortedTasks.sort((a, b) {
+      final comparison = _compareTasks(a.task, b.task, sortKey);
+      if (comparison != 0) {
+        return comparison;
+      }
 
-    return List<Task>.unmodifiable(sortedTasks);
+      return a.originalIndex.compareTo(b.originalIndex);
+    });
+
+    return List<Task>.unmodifiable(
+      sortedTasks.map((indexedTask) => indexedTask.task),
+    );
   }
 
   /// Return the green/blue/purple marker for one task.
@@ -187,7 +209,7 @@ class BacklogView {
       BacklogFilter.criticalMissed =>
         task.type == TaskType.critical && task.stats.missedCount > 0,
       BacklogFilter.wishlist => task.backlogTags.contains(BacklogTag.wishlist),
-      BacklogFilter.stale => now.difference(task.updatedAt) >= staleAfter,
+      BacklogFilter.stale => now.difference(task.createdAt) >= staleAfter,
       BacklogFilter.noRewardSet => task.reward == RewardLevel.notSet,
     };
   }
@@ -261,3 +283,14 @@ int _rewardVsEffortScore(Task task) {
 int _timesPushed(Task task) {
   return task.stats.manuallyPushedCount + task.stats.autoPushedCount;
 }
+
+/// Backlog task paired with its source-list position for stable sorting.
+class _IndexedTask {
+  const _IndexedTask({
+    required this.task,
+    required this.originalIndex,
+  });
+
+  final Task task;
+  final int originalIndex;
+}
diff --git a/lib/src/models.dart b/lib/src/models.dart
index 2bd7909..bbb5a6d 100644
--- a/lib/src/models.dart
+++ b/lib/src/models.dart
@@ -441,9 +441,14 @@ class ProjectProfile {
     Set<BacklogTag> backlogTags = const <BacklogTag>{},
     DateTime? updatedAt,
   }) {
+    final trimmedTitle = title.trim();
+    if (trimmedTitle.isEmpty) {
+      throw ArgumentError.value(title, 'title', 'Title is required.');
+    }
+
     return Task(
       id: id,
-      title: title,
+      title: trimmedTitle,
       projectId: this.id,
       type: type,
       status: status,
diff --git a/lib/src/scheduling_engine.dart b/lib/src/scheduling_engine.dart
index ed1c014..f308704 100644
--- a/lib/src/scheduling_engine.dart
+++ b/lib/src/scheduling_engine.dart
@@ -511,20 +511,29 @@ class SchedulingEngine {
   /// Rollover is bulk push behavior for day-end recovery. It collects unfinished
   /// flexible tasks outside the target window, preserves their relative order,
   /// then places them at the start of the new window while shifting already
-  /// planned flexible tasks as needed.
+  /// planned flexible tasks as needed. When [sourceWindow] is supplied, only
+  /// unfinished flexible tasks from that source window are rolled over. This
+  /// prevents future planned tasks from being pulled into tomorrow accidentally.
   SchedulingResult rollOverUnfinishedFlexibleTasks({
     required SchedulingInput input,
+    SchedulingWindow? sourceWindow,
     DateTime? updatedAt,
   }) {
     // Build the explicit queue of tasks to roll before asking the planner to
     // place anything. This keeps selection separate from placement.
     final rolledItems = <_PlacementItem>[];
     final rolloverTasks = input.flexibleTasks
-        .where((task) => _shouldRollOver(task, input.window))
+        .where((task) => _shouldRollOver(
+              task: task,
+              targetWindow: input.window,
+              sourceWindow: sourceWindow,
+            ))
         .toList()
       ..sort((a, b) {
-        final aStart = a.scheduledStart ?? input.window.start;
-        final bStart = b.scheduledStart ?? input.window.start;
+        final aStart =
+            a.scheduledStart ?? sourceWindow?.start ?? input.window.start;
+        final bStart =
+            b.scheduledStart ?? sourceWindow?.start ?? input.window.start;
 
         return aStart.compareTo(bStart);
       });
@@ -1269,13 +1278,21 @@ SchedulingResult _applyRolloverPlacement({
 ///
 /// Planned/active flexible tasks already inside the target window are not rolled
 /// again; they are handled as existing tasks that may shift to make room.
-bool _shouldRollOver(Task task, SchedulingWindow tomorrowWindow) {
+bool _shouldRollOver({
+  required Task task,
+  required SchedulingWindow targetWindow,
+  SchedulingWindow? sourceWindow,
+}) {
   final interval = _scheduledIntervalFor(task);
   final isTomorrowTask =
-      interval != null && interval.overlaps(tomorrowWindow.interval);
+      interval != null && interval.overlaps(targetWindow.interval);
+
+  final isInSourceWindow = sourceWindow == null ||
+      (interval != null && sourceWindow.contains(interval));
 
   return task.isFlexible &&
       !isTomorrowTask &&
+      isInSourceWindow &&
       (task.status == TaskStatus.planned || task.status == TaskStatus.active);
 }
 
diff --git a/test/edge_case_regression_test.dart b/test/edge_case_regression_test.dart
new file mode 100644
index 0000000..bea21f3
--- /dev/null
+++ b/test/edge_case_regression_test.dart
@@ -0,0 +1,792 @@
+import 'package:adhd_scheduler_core/scheduler_core.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group('Block 06.3 domain model regressions', () {
+    final now = DateTime(2026, 6, 19, 12);
+
+    test('quick capture trims titles before storing them', () {
+      final task = Task.quickCapture(
+        id: 'capture-1',
+        title: '  Refill medication  ',
+        createdAt: now,
+      );
+
+      expect(task.title, 'Refill medication');
+    });
+
+    test('copyWith can clear schedule while preserving omitted values', () {
+      final scheduled = Task.quickCapture(
+        id: 'task-1',
+        title: 'Send invoice',
+        createdAt: now,
+        projectId: 'admin',
+        priority: PriorityLevel.high,
+        reward: RewardLevel.medium,
+      ).copyWith(
+        status: TaskStatus.planned,
+        durationMinutes: 30,
+        scheduledStart: DateTime(2026, 6, 19, 13),
+        scheduledEnd: DateTime(2026, 6, 19, 13, 30),
+      );
+
+      final cleared = scheduled.copyWith(clearSchedule: true);
+
+      expect(cleared.scheduledStart, isNull);
+      expect(cleared.scheduledEnd, isNull);
+      expect(cleared.id, scheduled.id);
+      expect(cleared.title, scheduled.title);
+      expect(cleared.projectId, 'admin');
+      expect(cleared.priority, PriorityLevel.high);
+      expect(cleared.reward, RewardLevel.medium);
+      expect(cleared.durationMinutes, 30);
+    });
+
+    test('project profile trims and validates task titles like quick capture',
+        () {
+      const project = ProjectProfile(
+        id: 'health',
+        name: 'Health',
+        colorKey: 'green',
+      );
+
+      final task = project.createTask(
+        id: 'task-1',
+        title: '  Book appointment  ',
+        createdAt: now,
+      );
+
+      expect(task.title, 'Book appointment');
+      expect(
+        () => project.createTask(
+          id: 'task-2',
+          title: '   ',
+          createdAt: now,
+        ),
+        throwsArgumentError,
+      );
+    });
+  });
+
+  group('Block 06.3 scheduling regressions', () {
+    final now = DateTime(2026, 6, 19, 12);
+    const engine = SchedulingEngine();
+
+    test('next-available insertion uses earliest fitting open slot', () {
+      final backlog = backlogTask(
+        id: 'new-task',
+        title: 'Make call',
+        createdAt: now,
+        durationMinutes: 15,
+      );
+      final laterFlexible = plannedFlexibleTask(
+        id: 'later-flex',
+        title: 'Fold laundry',
+        createdAt: now,
+        start: DateTime(2026, 6, 19, 10),
+        durationMinutes: 30,
+      );
+
+      final result = engine.insertBacklogTaskIntoNextAvailableSlot(
+        input: SchedulingInput(
+          tasks: [backlog, laterFlexible],
+          window: SchedulingWindow(
+            start: DateTime(2026, 6, 19, 9),
+            end: DateTime(2026, 6, 19, 11),
+          ),
+          lockedIntervals: [
+            TimeInterval(
+              start: DateTime(2026, 6, 19, 9),
+              end: DateTime(2026, 6, 19, 9, 20),
+              label: 'locked',
+            ),
+          ],
+        ),
+        taskId: 'new-task',
+        updatedAt: now,
+      );
+      final inserted = taskById(result.tasks, 'new-task');
+
+      expect(inserted.status, TaskStatus.planned);
+      expect(inserted.scheduledStart, DateTime(2026, 6, 19, 9, 20));
+      expect(inserted.scheduledEnd, DateTime(2026, 6, 19, 9, 35));
+    });
+
+    test('no-fit insertion leaves the task backlogged and unplaced', () {
+      final backlog = backlogTask(
+        id: 'new-task',
+        title: 'Make call',
+        createdAt: now,
+        durationMinutes: 45,
+      );
+
+      final result = engine.insertBacklogTaskIntoNextAvailableSlot(
+        input: SchedulingInput(
+          tasks: [backlog],
+          window: SchedulingWindow(
+            start: DateTime(2026, 6, 19, 9),
+            end: DateTime(2026, 6, 19, 9, 30),
+          ),
+        ),
+        taskId: 'new-task',
+        updatedAt: now,
+      );
+      final unchanged = taskById(result.tasks, 'new-task');
+
+      expect(unchanged.status, TaskStatus.backlog);
+      expect(unchanged.scheduledStart, isNull);
+      expect(unchanged.scheduledEnd, isNull);
+      expect(result.notices.single.type, SchedulingNoticeType.overflow);
+    });
+
+    test('pushing flexible tasks preserves order without moving fixed items',
+        () {
+      final first = plannedFlexibleTask(
+        id: 'first',
+        title: 'Email reply',
+        createdAt: now,
+        start: DateTime(2026, 6, 19, 9),
+        durationMinutes: 15,
+      );
+      final second = plannedFlexibleTask(
+        id: 'second',
+        title: 'Laundry',
+        createdAt: now,
+        start: DateTime(2026, 6, 19, 9, 15),
+        durationMinutes: 15,
+      );
+      final inflexible = fixedTask(
+        id: 'appointment',
+        type: TaskType.inflexible,
+        createdAt: now,
+        start: DateTime(2026, 6, 19, 10),
+        durationMinutes: 15,
+      );
+      final critical = fixedTask(
+        id: 'meds',
+        type: TaskType.critical,
+        createdAt: now,
+        start: DateTime(2026, 6, 19, 10, 15),
+        durationMinutes: 15,
+      );
+      final locked = fixedTask(
+        id: 'locked-task',
+        type: TaskType.locked,
+        createdAt: now,
+        start: DateTime(2026, 6, 19, 9, 30),
+        durationMinutes: 15,
+      );
+
+      final result = engine.pushFlexibleTaskToNextAvailableSlot(
+        input: SchedulingInput(
+          tasks: [first, second, locked, inflexible, critical],
+          window: SchedulingWindow(
+            start: DateTime(2026, 6, 19, 9),
+            end: DateTime(2026, 6, 19, 11),
+          ),
+        ),
+        taskId: 'first',
+        updatedAt: now,
+      );
+
+      expect(
+        result.changes.map((change) => change.taskId),
+        ['first', 'second'],
+      );
+      expect(
+        taskById(result.tasks, 'first').scheduledStart,
+        DateTime(2026, 6, 19, 9, 15),
+      );
+      expect(
+        taskById(result.tasks, 'second').scheduledStart,
+        DateTime(2026, 6, 19, 9, 45),
+      );
+      expect(taskById(result.tasks, 'appointment').type, TaskType.inflexible);
+      expect(taskById(result.tasks, 'appointment').scheduledStart,
+          inflexible.scheduledStart);
+      expect(taskById(result.tasks, 'meds').type, TaskType.critical);
+      expect(taskById(result.tasks, 'meds').scheduledStart,
+          critical.scheduledStart);
+      expect(taskById(result.tasks, 'locked-task').type, TaskType.locked);
+      expect(taskById(result.tasks, 'locked-task').scheduledStart,
+          locked.scheduledStart);
+    });
+
+    test('rollover uses an explicit source window and ignores future tasks',
+        () {
+      final sourceWindow = SchedulingWindow(
+        start: DateTime(2026, 6, 19),
+        end: DateTime(2026, 6, 20),
+      );
+      final targetWindow = SchedulingWindow(
+        start: DateTime(2026, 6, 20, 9),
+        end: DateTime(2026, 6, 20, 12),
+      );
+      final sourcePlanned = plannedFlexibleTask(
+        id: 'source-planned',
+        title: 'Source planned',
+        createdAt: now,
+        start: DateTime(2026, 6, 19, 13),
+        durationMinutes: 15,
+      );
+      final sourceActive = plannedFlexibleTask(
+        id: 'source-active',
+        title: 'Source active',
+        createdAt: now,
+        start: DateTime(2026, 6, 19, 14),
+        durationMinutes: 15,
+      ).copyWith(status: TaskStatus.active);
+      final completed = plannedFlexibleTask(
+        id: 'completed',
+        title: 'Completed',
+        createdAt: now,
+        start: DateTime(2026, 6, 19, 15),
+        durationMinutes: 15,
+      ).copyWith(status: TaskStatus.completed);
+      final cancelled = plannedFlexibleTask(
+        id: 'cancelled',
+        title: 'Cancelled',
+        createdAt: now,
+        start: DateTime(2026, 6, 19, 16),
+        durationMinutes: 15,
+      ).copyWith(status: TaskStatus.cancelled);
+      final backlogged = backlogTask(
+        id: 'backlog',
+        title: 'Already backlog',
+        createdAt: now,
+        durationMinutes: 15,
+      );
+      final critical = fixedTask(
+        id: 'critical',
+        type: TaskType.critical,
+        createdAt: now,
+        start: DateTime(2026, 6, 19, 17),
+        durationMinutes: 15,
+      );
+      final inflexible = fixedTask(
+        id: 'inflexible',
+        type: TaskType.inflexible,
+        createdAt: now,
+        start: DateTime(2026, 6, 19, 18),
+        durationMinutes: 15,
+      );
+      final futureFlexible = plannedFlexibleTask(
+        id: 'future',
+        title: 'Future',
+        createdAt: now,
+        start: DateTime(2026, 6, 21, 9),
+        durationMinutes: 15,
+      );
+      final tomorrowFlexible = plannedFlexibleTask(
+        id: 'tomorrow',
+        title: 'Tomorrow',
+        createdAt: now,
+        start: DateTime(2026, 6, 20, 9),
+        durationMinutes: 30,
+      );
+
+      final result = engine.rollOverUnfinishedFlexibleTasks(
+        input: SchedulingInput(
+          tasks: [
+            futureFlexible,
+            sourceActive,
+            sourcePlanned,
+            completed,
+            cancelled,
+            backlogged,
+            critical,
+            inflexible,
+            tomorrowFlexible,
+          ],
+          window: targetWindow,
+        ),
+        sourceWindow: sourceWindow,
+        updatedAt: now,
+      );
+
+      expect(taskById(result.tasks, 'source-planned').scheduledStart,
+          DateTime(2026, 6, 20, 9));
+      expect(taskById(result.tasks, 'source-active').scheduledStart,
+          DateTime(2026, 6, 20, 9, 15));
+      expect(taskById(result.tasks, 'tomorrow').scheduledStart,
+          DateTime(2026, 6, 20, 9, 30));
+      expect(taskById(result.tasks, 'future').scheduledStart,
+          futureFlexible.scheduledStart);
+      expect(taskById(result.tasks, 'completed').status, TaskStatus.completed);
+      expect(taskById(result.tasks, 'cancelled').status, TaskStatus.cancelled);
+      expect(taskById(result.tasks, 'backlog').status, TaskStatus.backlog);
+      expect(taskById(result.tasks, 'critical').type, TaskType.critical);
+      expect(taskById(result.tasks, 'inflexible').type, TaskType.inflexible);
+      expect(
+        result.changes.map((change) => change.taskId),
+        ['source-active', 'source-planned', 'tomorrow'],
+      );
+    });
+  });
+
+  group('Block 06.3 backlog regressions', () {
+    final now = DateTime(2026, 6, 19, 12);
+
+    test('filters only include backlog tasks in the expected category', () {
+      final inbox = backlogTask(
+        id: 'inbox',
+        title: 'Inbox',
+        createdAt: now,
+        reward: RewardLevel.low,
+      );
+      final pushed = backlogTask(
+        id: 'pushed',
+        title: 'Pushed',
+        createdAt: now,
+        projectId: 'home',
+        reward: RewardLevel.low,
+      ).copyWith(stats: const TaskStatistics(manuallyPushedCount: 1));
+      final criticalMissed = backlogTask(
+        id: 'critical',
+        title: 'Critical',
+        createdAt: now,
+        type: TaskType.critical,
+        projectId: 'health',
+        reward: RewardLevel.low,
+      ).copyWith(stats: const TaskStatistics(missedCount: 1));
+      final wishlist = backlogTask(
+        id: 'wishlist',
+        title: 'Wishlist',
+        createdAt: now,
+        projectId: 'ideas',
+        reward: RewardLevel.low,
+        backlogTags: const {BacklogTag.wishlist},
+      );
+      final stale = backlogTask(
+        id: 'stale',
+        title: 'Stale',
+        createdAt: now.subtract(const Duration(days: 40)),
+        projectId: 'archive',
+        reward: RewardLevel.low,
+      );
+      final noReward = backlogTask(
+        id: 'no-reward',
+        title: 'No reward',
+        createdAt: now,
+        projectId: 'admin',
+      );
+      final plannedNoReward = noReward.copyWith(
+        id: 'planned-no-reward',
+        status: TaskStatus.planned,
+      );
+      final view = BacklogView(
+        tasks: [
+          inbox,
+          pushed,
+          criticalMissed,
+          wishlist,
+          stale,
+          noReward,
+          plannedNoReward,
+        ],
+        now: now,
+      );
+
+      expect(view.filter(BacklogFilter.inbox).map((task) => task.id), [
+        'inbox',
+      ]);
+      expect(view.filter(BacklogFilter.pushed).map((task) => task.id), [
+        'pushed',
+      ]);
+      expect(view.filter(BacklogFilter.criticalMissed).map((task) => task.id), [
+        'critical',
+      ]);
+      expect(view.filter(BacklogFilter.wishlist).map((task) => task.id), [
+        'wishlist',
+      ]);
+      expect(view.filter(BacklogFilter.stale).map((task) => task.id), [
+        'stale',
+      ]);
+      expect(view.filter(BacklogFilter.noRewardSet).map((task) => task.id), [
+        'no-reward',
+      ]);
+    });
+
+    test('priority sorting preserves input order for equal priorities', () {
+      final first = backlogTask(id: 'first', title: 'First', createdAt: now);
+      final second = backlogTask(id: 'second', title: 'Second', createdAt: now);
+      final third = backlogTask(id: 'third', title: 'Third', createdAt: now);
+      final view = BacklogView(tasks: [second, first, third], now: now);
+
+      expect(view.sorted(BacklogSortKey.priority).map((task) => task.id), [
+        'second',
+        'first',
+        'third',
+      ]);
+    });
+
+    test('reward not-set sorts as distinct from very-low reward', () {
+      final notSet = backlogTask(
+        id: 'not-set',
+        title: 'Unknown reward',
+        createdAt: now,
+        reward: RewardLevel.notSet,
+        difficulty: DifficultyLevel.easy,
+      );
+      final veryLow = backlogTask(
+        id: 'very-low',
+        title: 'Very low reward',
+        createdAt: now,
+        reward: RewardLevel.veryLow,
+        difficulty: DifficultyLevel.easy,
+      );
+      final view = BacklogView(tasks: [notSet, veryLow], now: now);
+
+      expect(
+          view.sorted(BacklogSortKey.rewardVsEffort).map((task) => task.id), [
+        'very-low',
+        'not-set',
+      ]);
+    });
+
+    test('age sorting preserves input order when createdAt values match', () {
+      final createdAt = DateTime(2026, 6, 1);
+      final first =
+          backlogTask(id: 'first', title: 'First', createdAt: createdAt);
+      final second =
+          backlogTask(id: 'second', title: 'Second', createdAt: createdAt);
+      final view = BacklogView(tasks: [second, first], now: now);
+
+      expect(view.sorted(BacklogSortKey.age).map((task) => task.id), [
+        'second',
+        'first',
+      ]);
+    });
+
+    test('stale filter and marker use the same creation-age semantics', () {
+      final oldButRecentlyUpdated = backlogTask(
+        id: 'old',
+        title: 'Old idea',
+        createdAt: now.subtract(const Duration(days: 40)),
+      ).copyWith(updatedAt: now);
+      final newButOldUpdate = backlogTask(
+        id: 'new',
+        title: 'New idea',
+        createdAt: now,
+      ).copyWith(updatedAt: now.subtract(const Duration(days: 40)));
+      final view = BacklogView(
+        tasks: [oldButRecentlyUpdated, newButOldUpdate],
+        now: now,
+      );
+
+      expect(view.filter(BacklogFilter.stale).map((task) => task.id), ['old']);
+      expect(
+        view.stalenessMarkerFor(oldButRecentlyUpdated),
+        BacklogStalenessMarker.purple,
+      );
+      expect(
+        view.stalenessMarkerFor(newButOldUpdate),
+        BacklogStalenessMarker.green,
+      );
+    });
+  });
+
+  group('Block 06.3 quick capture regressions', () {
+    final now = DateTime(2026, 6, 19, 12);
+    const service = QuickCaptureService();
+
+    test('immediate scheduling uses normal insertion and push rules', () {
+      final existing = plannedFlexibleTask(
+        id: 'existing',
+        title: 'Existing',
+        createdAt: now,
+        start: DateTime(2026, 6, 19, 9),
+        durationMinutes: 15,
+      );
+
+      final result = service.capture(
+        QuickCaptureRequest(
+          id: 'capture',
+          title: 'Captured task',
+          createdAt: now,
+          addToNextAvailableSlot: true,
+          durationMinutes: 15,
+        ),
+        schedulingInput: SchedulingInput(
+          tasks: [existing],
+          window: SchedulingWindow(
+            start: DateTime(2026, 6, 19, 9),
+            end: DateTime(2026, 6, 19, 10),
+          ),
+        ),
+        updatedAt: now,
+      );
+      final scheduledTasks = result.schedulingResult!.tasks;
+
+      expect(result.status, QuickCaptureStatus.scheduled);
+      expect(taskById(scheduledTasks, 'capture').scheduledStart,
+          DateTime(2026, 6, 19, 9));
+      expect(taskById(scheduledTasks, 'existing').scheduledStart,
+          DateTime(2026, 6, 19, 9, 15));
+    });
+
+    test('immediate scheduling requires enough scheduling data', () {
+      final result = service.capture(
+        QuickCaptureRequest(
+          id: 'capture',
+          title: 'Captured task',
+          createdAt: now,
+          addToNextAvailableSlot: true,
+          durationMinutes: 15,
+        ),
+        updatedAt: now,
+      );
+
+      expect(result.status, QuickCaptureStatus.validationError);
+      expect(result.messages.single, 'Scheduling input is required.');
+    });
+
+    test('quick capture cannot create blank tasks', () {
+      expect(
+        () => service.capture(
+          QuickCaptureRequest(
+            id: 'capture',
+            title: '   ',
+            createdAt: now,
+          ),
+        ),
+        throwsArgumentError,
+      );
+    });
+  });
+
+  group('Block 06.3 locked-time regressions', () {
+    final now = DateTime(2026, 6, 19, 12);
+
+    test('locked occurrence exposes overlay data without becoming a task', () {
+      final block = LockedBlock(
+        id: 'work',
+        name: 'Work',
+        startTime: const ClockTime(hour: 9, minute: 0),
+        endTime: const ClockTime(hour: 17, minute: 0),
+        recurrence: const LockedBlockRecurrence.weekly(
+          weekdays: {LockedWeekday.friday},
+        ),
+        createdAt: now,
+        updatedAt: now,
+      );
+
+      final expansion = expandLockedBlocksForDay(
+        blocks: [block],
+        overrides: const [],
+        date: DateTime(2026, 6, 19),
+      );
+      final occurrence = expansion.occurrences.single;
+
+      expect(occurrence, isA<LockedBlockOccurrence>());
+      expect(occurrence, isNot(isA<Task>()));
+      expect(occurrence.hiddenByDefault, isTrue);
+      expect(occurrence.schedulingInterval.label, 'Work');
+      expect(expansion.schedulingIntervals.single.label, 'Work');
+    });
+
+    test('completed tasks outside locked hours do not increment counters', () {
+      final task = plannedFlexibleTask(
+        id: 'task',
+        title: 'Task',
+        createdAt: now,
+        start: DateTime(2026, 6, 19, 8),
+        durationMinutes: 30,
+      ).copyWith(status: TaskStatus.completed);
+
+      final tracked = trackCompletedDuringLockedHours(
+        task: task,
+        lockedIntervals: [
+          TimeInterval(
+            start: DateTime(2026, 6, 19, 9),
+            end: DateTime(2026, 6, 19, 10),
+          ),
+        ],
+      );
+
+      expect(tracked.stats.completedDuringLockedHoursCount, 0);
+      expect(tracked.stats.completedDuringLockedHoursMinutes, 0);
+    });
+  });
+
+  group('Block 06.3 action-service regressions', () {
+    final now = DateTime(2026, 6, 19, 12);
+    const service = FlexibleTaskActionService();
+
+    test('unsupported flexible quick action types fail predictably', () {
+      final inflexible = fixedTask(
+        id: 'appointment',
+        type: TaskType.inflexible,
+        createdAt: now,
+        start: DateTime(2026, 6, 19, 9),
+        durationMinutes: 30,
+      );
+
+      expect(
+        () => service.apply(
+          task: inflexible,
+          action: FlexibleTaskQuickAction.done,
+          updatedAt: now,
+        ),
+        throwsArgumentError,
+      );
+    });
+
+    test('push backlog destination does not create duplicate task ids', () {
+      final task = plannedFlexibleTask(
+        id: 'task',
+        title: 'Task',
+        createdAt: now,
+        start: DateTime(2026, 6, 19, 9),
+        durationMinutes: 30,
+      );
+
+      final result = service.applyPushDestination(
+        destination: PushDestination.backlog,
+        input: SchedulingInput(
+          tasks: [task],
+          window: SchedulingWindow(
+            start: DateTime(2026, 6, 19, 9),
+            end: DateTime(2026, 6, 19, 10),
+          ),
+        ),
+        taskId: 'task',
+        updatedAt: now,
+      );
+
+      expect(result.schedulingResult.tasks.map((task) => task.id), ['task']);
+      expect(result.schedulingResult.tasks.toSet().length, 1);
+      expect(result.schedulingResult.changes.single.previousStart,
+          DateTime(2026, 6, 19, 9));
+      expect(result.schedulingResult.changes.single.nextStart, isNull);
+    });
+
+    test('public scheduling services do not reorder the input task list', () {
+      final first = plannedFlexibleTask(
+        id: 'first',
+        title: 'First',
+        createdAt: now,
+        start: DateTime(2026, 6, 19, 9),
+        durationMinutes: 15,
+      );
+      final second = plannedFlexibleTask(
+        id: 'second',
+        title: 'Second',
+        createdAt: now,
+        start: DateTime(2026, 6, 19, 9, 15),
+        durationMinutes: 15,
+      );
+      final tasks = [second, first];
+
+      const SchedulingEngine().pushFlexibleTaskToNextAvailableSlot(
+        input: SchedulingInput(
+          tasks: tasks,
+          window: SchedulingWindow(
+            start: DateTime(2026, 6, 19, 9),
+            end: DateTime(2026, 6, 19, 10),
+          ),
+        ),
+        taskId: 'first',
+        updatedAt: now,
+      );
+
+      expect(tasks.map((task) => task.id), ['second', 'first']);
+    });
+
+    test('invalid push destinations leave fixed task types unchanged', () {
+      final critical = fixedTask(
+        id: 'critical',
+        type: TaskType.critical,
+        createdAt: now,
+        start: DateTime(2026, 6, 19, 9),
+        durationMinutes: 30,
+      );
+
+      final result = service.applyPushDestination(
+        destination: PushDestination.nextAvailableSlot,
+        input: SchedulingInput(
+          tasks: [critical],
+          window: SchedulingWindow(
+            start: DateTime(2026, 6, 19, 9),
+            end: DateTime(2026, 6, 19, 10),
+          ),
+        ),
+        taskId: 'critical',
+        updatedAt: now,
+      );
+
+      expect(result.schedulingResult.notices.single.type,
+          SchedulingNoticeType.noFit);
+      expect(result.schedulingResult.tasks.single.type, TaskType.critical);
+      expect(result.schedulingResult.tasks.single.status, TaskStatus.planned);
+    });
+  });
+}
+
+Task backlogTask({
+  required String id,
+  required String title,
+  required DateTime createdAt,
+  String projectId = 'inbox',
+  TaskType type = TaskType.flexible,
+  RewardLevel reward = RewardLevel.notSet,
+  DifficultyLevel difficulty = DifficultyLevel.notSet,
+  int? durationMinutes,
+  Set<BacklogTag> backlogTags = const <BacklogTag>{},
+}) {
+  return Task.quickCapture(
+    id: id,
+    title: title,
+    createdAt: createdAt,
+    projectId: projectId,
+    type: type,
+    reward: reward,
+    difficulty: difficulty,
+    backlogTags: backlogTags,
+  ).copyWith(durationMinutes: durationMinutes);
+}
+
+Task plannedFlexibleTask({
+  required String id,
+  required String title,
+  required DateTime createdAt,
+  required DateTime start,
+  required int durationMinutes,
+}) {
+  return backlogTask(
+    id: id,
+    title: title,
+    createdAt: createdAt,
+    durationMinutes: durationMinutes,
+  ).copyWith(
+    status: TaskStatus.planned,
+    scheduledStart: start,
+    scheduledEnd: start.add(Duration(minutes: durationMinutes)),
+  );
+}
+
+Task fixedTask({
+  required String id,
+  required TaskType type,
+  required DateTime createdAt,
+  required DateTime start,
+  required int durationMinutes,
+}) {
+  return Task(
+    id: id,
+    title: id,
+    projectId: 'fixed',
+    type: type,
+    status: TaskStatus.planned,
+    priority: PriorityLevel.medium,
+    durationMinutes: durationMinutes,
+    scheduledStart: start,
+    scheduledEnd: start.add(Duration(minutes: durationMinutes)),
+    createdAt: createdAt,
+    updatedAt: createdAt,
+  );
+}
+
+Task taskById(List<Task> tasks, String id) {
+  return tasks.singleWhere((task) => task.id == id);
+}