diff --git a/src/data/mock-events.json b/src/data/mock-events.json
index ff7bb6f..904cf74 100644
--- a/src/data/mock-events.json
+++ b/src/data/mock-events.json
@@ -1208,5 +1208,475 @@
     "allDay": false,
     "syncStatus": "synced",
     "metadata": { "duration": 120, "color": "#2196f3" }
+  },
+  {
+    "id": "122",
+    "title": "Multi-Day Conference",
+    "start": "2025-09-22T00:00:00",
+    "end": "2025-09-24T23:59:59",
+    "type": "meeting",
+    "allDay": true,
+    "syncStatus": "synced",
+    "metadata": { "duration": 4320, "color": "#4caf50" }
+  },
+  {
+    "id": "123",
+    "title": "Project Sprint",
+    "start": "2025-09-23T00:00:00",
+    "end": "2025-09-25T23:59:59",
+    "type": "work",
+    "allDay": true,
+    "syncStatus": "synced",
+    "metadata": { "duration": 4320, "color": "#2196f3" }
+  },
+  {
+    "id": "124",
+    "title": "Training Week",
+    "start": "2025-09-29T00:00:00",
+    "end": "2025-10-03T23:59:59",
+    "type": "meeting",
+    "allDay": true,
+    "syncStatus": "synced",
+    "metadata": { "duration": 7200, "color": "#9c27b0" }
+  },
+  {
+    "id": "125",
+    "title": "Holiday Weekend",
+    "start": "2025-10-04T00:00:00",
+    "end": "2025-10-06T23:59:59",
+    "type": "milestone",
+    "allDay": true,
+    "syncStatus": "synced",
+    "metadata": { "duration": 4320, "color": "#ff6f00" }
+  },
+  {
+    "id": "126",
+    "title": "Client Visit",
+    "start": "2025-10-07T00:00:00",
+    "end": "2025-10-09T23:59:59",
+    "type": "meeting",
+    "allDay": true,
+    "syncStatus": "synced",
+    "metadata": { "duration": 4320, "color": "#e91e63" }
+  },
+  {
+    "id": "127",
+    "title": "Development Marathon",
+    "start": "2025-10-13T00:00:00",
+    "end": "2025-10-15T23:59:59",
+    "type": "work",
+    "allDay": true,
+    "syncStatus": "synced",
+    "metadata": { "duration": 4320, "color": "#3f51b5" }
+  },
+  {
+    "id": "128",
+    "title": "Morgen Standup",
+    "start": "2025-09-22T09:00:00",
+    "end": "2025-09-22T09:30:00",
+    "type": "meeting",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 30, "color": "#ff5722" }
+  },
+  {
+    "id": "129",
+    "title": "Klient Præsentation",
+    "start": "2025-09-22T14:00:00",
+    "end": "2025-09-22T15:30:00",
+    "type": "meeting",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 90, "color": "#e91e63" }
+  },
+  {
+    "id": "130",
+    "title": "Eftermiddags Kodning",
+    "start": "2025-09-22T16:00:00",
+    "end": "2025-09-22T18:00:00",
+    "type": "work",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 120, "color": "#2196f3" }
+  },
+  {
+    "id": "131",
+    "title": "Team Standup",
+    "start": "2025-09-23T09:00:00",
+    "end": "2025-09-23T09:30:00",
+    "type": "meeting",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 30, "color": "#ff5722" }
+  },
+  {
+    "id": "132",
+    "title": "Arkitektur Review",
+    "start": "2025-09-23T11:00:00",
+    "end": "2025-09-23T12:30:00",
+    "type": "meeting",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 90, "color": "#009688" }
+  },
+  {
+    "id": "133",
+    "title": "Frokost & Læring",
+    "start": "2025-09-23T12:30:00",
+    "end": "2025-09-23T13:30:00",
+    "type": "meal",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 60, "color": "#ff9800" }
+  },
+  {
+    "id": "134",
+    "title": "Team Standup",
+    "start": "2025-09-24T09:00:00",
+    "end": "2025-09-24T09:30:00",
+    "type": "meeting",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 30, "color": "#ff5722" }
+  },
+  {
+    "id": "135",
+    "title": "Database Optimering",
+    "start": "2025-09-24T10:00:00",
+    "end": "2025-09-24T12:00:00",
+    "type": "work",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 120, "color": "#3f51b5" }
+  },
+  {
+    "id": "136",
+    "title": "Klient Opkald",
+    "start": "2025-09-24T15:00:00",
+    "end": "2025-09-24T16:00:00",
+    "type": "meeting",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 60, "color": "#795548" }
+  },
+  {
+    "id": "137",
+    "title": "Team Standup",
+    "start": "2025-09-25T09:00:00",
+    "end": "2025-09-25T09:30:00",
+    "type": "meeting",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 30, "color": "#ff5722" }
+  },
+  {
+    "id": "138",
+    "title": "Sprint Review",
+    "start": "2025-09-25T14:00:00",
+    "end": "2025-09-25T15:00:00",
+    "type": "meeting",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 60, "color": "#607d8b" }
+  },
+  {
+    "id": "139",
+    "title": "Retrospektiv",
+    "start": "2025-09-25T15:30:00",
+    "end": "2025-09-25T16:30:00",
+    "type": "meeting",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 60, "color": "#9c27b0" }
+  },
+  {
+    "id": "140",
+    "title": "Team Standup",
+    "start": "2025-09-26T09:00:00",
+    "end": "2025-09-26T09:30:00",
+    "type": "meeting",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 30, "color": "#ff5722" }
+  },
+  {
+    "id": "141",
+    "title": "Ny Feature Udvikling",
+    "start": "2025-09-26T10:00:00",
+    "end": "2025-09-26T12:00:00",
+    "type": "work",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 120, "color": "#4caf50" }
+  },
+  {
+    "id": "142",
+    "title": "Sikkerhedsgennemgang",
+    "start": "2025-09-26T14:00:00",
+    "end": "2025-09-26T15:30:00",
+    "type": "meeting",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 90, "color": "#f44336" }
+  },
+  {
+    "id": "143",
+    "title": "Weekend Hackathon",
+    "start": "2025-09-27T00:00:00",
+    "end": "2025-09-28T23:59:59",
+    "type": "work",
+    "allDay": true,
+    "syncStatus": "synced",
+    "metadata": { "duration": 2880, "color": "#673ab7" }
+  },
+  {
+    "id": "144",
+    "title": "Team Standup",
+    "start": "2025-09-29T09:00:00",
+    "end": "2025-09-29T09:30:00",
+    "type": "meeting",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 30, "color": "#ff5722" }
+  },
+  {
+    "id": "145",
+    "title": "Månedlig Planlægning",
+    "start": "2025-09-29T10:00:00",
+    "end": "2025-09-29T12:00:00",
+    "type": "meeting",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 120, "color": "#9c27b0" }
+  },
+  {
+    "id": "146",
+    "title": "Performance Test",
+    "start": "2025-09-29T14:00:00",
+    "end": "2025-09-29T16:00:00",
+    "type": "work",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 120, "color": "#00bcd4" }
+  },
+  {
+    "id": "147",
+    "title": "Team Standup",
+    "start": "2025-09-30T09:00:00",
+    "end": "2025-09-30T09:30:00",
+    "type": "meeting",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 30, "color": "#ff5722" }
+  },
+  {
+    "id": "148",
+    "title": "Kvartal Afslutning",
+    "start": "2025-09-30T15:00:00",
+    "end": "2025-09-30T17:00:00",
+    "type": "milestone",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 120, "color": "#f44336" }
+  },
+  {
+    "id": "149",
+    "title": "Oktober Kickoff",
+    "start": "2025-10-01T09:00:00",
+    "end": "2025-10-01T10:00:00",
+    "type": "meeting",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 60, "color": "#4caf50" }
+  },
+  {
+    "id": "150",
+    "title": "Sprint Planlægning",
+    "start": "2025-10-01T10:30:00",
+    "end": "2025-10-01T12:00:00",
+    "type": "meeting",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 90, "color": "#673ab7" }
+  },
+  {
+    "id": "151",
+    "title": "Eftermiddags Kodning",
+    "start": "2025-10-01T14:00:00",
+    "end": "2025-10-01T17:00:00",
+    "type": "work",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 180, "color": "#2196f3" }
+  },
+  {
+    "id": "152",
+    "title": "Team Standup",
+    "start": "2025-10-02T09:00:00",
+    "end": "2025-10-02T09:30:00",
+    "type": "meeting",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 30, "color": "#ff5722" }
+  },
+  {
+    "id": "153",
+    "title": "API Design Workshop",
+    "start": "2025-10-02T11:00:00",
+    "end": "2025-10-02T12:30:00",
+    "type": "meeting",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 90, "color": "#009688" }
+  },
+  {
+    "id": "154",
+    "title": "Bug Fixing Session",
+    "start": "2025-10-02T15:00:00",
+    "end": "2025-10-02T17:00:00",
+    "type": "work",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 120, "color": "#ff5722" }
+  },
+  {
+    "id": "155",
+    "title": "Team Standup",
+    "start": "2025-10-03T09:00:00",
+    "end": "2025-10-03T09:30:00",
+    "type": "meeting",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 30, "color": "#ff5722" }
+  },
+  {
+    "id": "156",
+    "title": "Klient Demo",
+    "start": "2025-10-03T14:00:00",
+    "end": "2025-10-03T15:00:00",
+    "type": "meeting",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 60, "color": "#e91e63" }
+  },
+  {
+    "id": "157",
+    "title": "Code Review Session",
+    "start": "2025-10-03T16:00:00",
+    "end": "2025-10-03T17:00:00",
+    "type": "work",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 60, "color": "#009688" }
+  },
+  {
+    "id": "158",
+    "title": "Fredag Standup",
+    "start": "2025-10-04T09:00:00",
+    "end": "2025-10-04T09:30:00",
+    "type": "meeting",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 30, "color": "#ff5722" }
+  },
+  {
+    "id": "159",
+    "title": "Uge Retrospektiv",
+    "start": "2025-10-04T15:00:00",
+    "end": "2025-10-04T16:00:00",
+    "type": "meeting",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 60, "color": "#9c27b0" }
+  },
+  {
+    "id": "160",
+    "title": "Weekend Projekt",
+    "start": "2025-10-05T10:00:00",
+    "end": "2025-10-05T14:00:00",
+    "type": "work",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 240, "color": "#3f51b5" }
+  },
+  {
+    "id": "161",
+    "title": "Teknisk Workshop",
+    "start": "2025-09-24T00:00:00",
+    "end": "2025-09-26T23:59:59",
+    "type": "meeting",
+    "allDay": true,
+    "syncStatus": "synced",
+    "metadata": { "duration": 4320, "color": "#795548" }
+  },
+  {
+    "id": "162",
+    "title": "Produktudvikling Sprint",
+    "start": "2025-10-01T00:00:00",
+    "end": "2025-10-03T23:59:59",
+    "type": "work",
+    "allDay": true,
+    "syncStatus": "synced",
+    "metadata": { "duration": 4320, "color": "#cddc39" }
+  },
+  {
+    "id": "163",
+    "title": "Tidlig Morgen Træning",
+    "start": "2025-09-23T06:30:00",
+    "end": "2025-09-23T07:30:00",
+    "type": "work",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 60, "color": "#00bcd4" }
+  },
+  {
+    "id": "164",
+    "title": "Sen Aften Deploy",
+    "start": "2025-09-25T22:00:00",
+    "end": "2025-09-26T00:30:00",
+    "type": "work",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 150, "color": "#ffc107" }
+  },
+  {
+    "id": "165",
+    "title": "Overlappende Møde A",
+    "start": "2025-09-30T10:00:00",
+    "end": "2025-09-30T11:30:00",
+    "type": "meeting",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 90, "color": "#8bc34a" }
+  },
+  {
+    "id": "166",
+    "title": "Overlappende Møde B",
+    "start": "2025-09-30T10:30:00",
+    "end": "2025-09-30T12:00:00",
+    "type": "meeting",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 90, "color": "#ff6f00" }
+  },
+  {
+    "id": "167",
+    "title": "Kort Check-in",
+    "start": "2025-10-02T09:45:00",
+    "end": "2025-10-02T10:00:00",
+    "type": "meeting",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 15, "color": "#607d8b" }
+  },
+  {
+    "id": "168",
+    "title": "Lang Udviklingssession",
+    "start": "2025-10-04T09:00:00",
+    "end": "2025-10-04T13:00:00",
+    "type": "work",
+    "allDay": false,
+    "syncStatus": "synced",
+    "metadata": { "duration": 240, "color": "#2196f3" }
   }
 ]
\ No newline at end of file
diff --git a/src/managers/AllDayManager.ts b/src/managers/AllDayManager.ts
index e0887cc..c88f775 100644
--- a/src/managers/AllDayManager.ts
+++ b/src/managers/AllDayManager.ts
@@ -107,6 +107,19 @@ export class AllDayManager {
       console.log('🎯 AllDayManager: Ending drag for all-day event', { eventId });
       this.handleDragEnd(draggedElement, dragClone as HTMLElement, finalPosition.column);
     });
+
+    // Listen for drag cancellation to recalculate height
+    eventBus.on('drag:cancelled', (event) => {
+      const { draggedElement, reason } = (event as CustomEvent).detail;
+      
+      console.log('🚫 AllDayManager: Drag cancelled', {
+        eventId: draggedElement?.dataset?.eventId,
+        reason
+      });
+      
+      // Recalculate all-day height since clones may have been removed
+      this.checkAndAnimateAllDayHeight();
+    });
   }
 
   /**
diff --git a/src/managers/DragDropManager.ts b/src/managers/DragDropManager.ts
index b4004b0..8db9840 100644
--- a/src/managers/DragDropManager.ts
+++ b/src/managers/DragDropManager.ts
@@ -62,6 +62,7 @@ export class DragDropManager {
   // Column bounds cache for coordinate-based column detection
   private columnBoundsCache: ColumnBounds[] = [];
 
+
   // Auto-scroll properties
   private autoScrollAnimationId: number | null = null;
   private readonly scrollSpeed = 10; // pixels per frame
@@ -108,6 +109,16 @@ export class DragDropManager {
     document.body.addEventListener('mousedown', this.boundHandlers.mouseDown);
     document.body.addEventListener('mouseup', this.boundHandlers.mouseUp);
 
+    // Add mouseleave listener to calendar container for drag cancellation
+    const calendarContainer = document.querySelector('swp-calendar-container');
+    if (calendarContainer) {
+      calendarContainer.addEventListener('mouseleave', () => {
+        if (this.draggedElement && this.isDragStarted) {
+          this.cancelDrag();
+        }
+      });
+    }
+
     // Initialize column bounds cache
     this.updateColumnBoundsCache();
 
@@ -303,7 +314,41 @@ export class DragDropManager {
   private cleanupAllClones(): void {
     // Remove clones from all possible locations
     const allClones = document.querySelectorAll('[data-event-id^="clone"]');
-    allClones.forEach(clone => clone.remove());
+    
+    if (allClones.length > 0) {
+      console.log(`🧹 DragDropManager: Removing ${allClones.length} clone(s)`);
+      allClones.forEach(clone => clone.remove());
+    }
+  }
+
+  /**
+   * Cancel drag operation when mouse leaves grid container
+   */
+  private cancelDrag(): void {
+    if (!this.draggedElement) return;
+
+    console.log('🚫 DragDropManager: Cancelling drag - mouse left grid container');
+
+    const draggedElement = this.draggedElement;
+
+    // 1. Remove all clones
+    this.cleanupAllClones();
+
+    // 2. Restore original element
+    if (draggedElement) {
+      draggedElement.style.opacity = '';
+      draggedElement.style.cursor = '';
+    }
+
+    // 3. Emit cancellation event
+    this.eventBus.emit('drag:cancelled', {
+      draggedElement: draggedElement,
+      reason: 'mouse-left-grid'
+    });
+
+    // 4. Clean up state
+    this.cleanupDragState();
+    this.stopAutoScroll();
   }
 
   /**
diff --git a/src/managers/HeaderManager.ts b/src/managers/HeaderManager.ts
index 1f9d1b3..8ac9204 100644
--- a/src/managers/HeaderManager.ts
+++ b/src/managers/HeaderManager.ts
@@ -11,7 +11,6 @@ import { DragMouseEnterHeaderEventPayload, DragMouseLeaveHeaderEventPayload } fr
  * Separates event handling from rendering concerns
  */
 export class HeaderManager {
-  private cachedCalendarHeader: HTMLElement | null = null;
   
   // Event listeners for drag events
   private dragMouseEnterHeaderListener: ((event: Event) => void) | null = null;
@@ -40,10 +39,7 @@ export class HeaderManager {
    * Get cached calendar header element
    */
   private getCalendarHeader(): HTMLElement | null {
-    if (!this.cachedCalendarHeader) {
-      this.cachedCalendarHeader = document.querySelector('swp-calendar-header');
-    }
-    return this.cachedCalendarHeader;
+      return document.querySelector('swp-calendar-header');
   }
 
   /**
@@ -196,21 +192,13 @@ export class HeaderManager {
         calendarHeader = document.createElement('swp-calendar-header');
         // Insert header as first child
         gridContainer.insertBefore(calendarHeader, gridContainer.firstChild);
-        this.cachedCalendarHeader = calendarHeader;
+ 
       }
     }
     
     return calendarHeader;
   }
 
-
-  /**
-   * Clear cached header reference
-   */
-  public clearCache(): void {
-    this.cachedCalendarHeader = null;
-  }
-
   /**
    * Clean up resources and event listeners
    */
@@ -228,6 +216,5 @@ export class HeaderManager {
     this.dragMouseEnterHeaderListener = null;
     this.dragMouseLeaveHeaderListener = null;
     
-    this.clearCache();
   }
 }
\ No newline at end of file