diff --git a/src/components/CalendarHeader.vue b/src/components/CalendarHeader.vue
index f82fa43..1ddb646 100644
--- a/src/components/CalendarHeader.vue
+++ b/src/components/CalendarHeader.vue
@@ -96,8 +96,8 @@ const weekdayNames = computed(() => {
       <Numeric
         :model-value="currentYear"
         @update:modelValue="changeYear"
-  :min="MIN_YEAR"
-  :max="MAX_YEAR"
+        :min="MIN_YEAR"
+        :max="MAX_YEAR"
         :step="1"
         aria-label="Year"
         number-prefix=""
diff --git a/src/components/CalendarView.vue b/src/components/CalendarView.vue
index c96553a..f2b43d2 100644
--- a/src/components/CalendarView.vue
+++ b/src/components/CalendarView.vue
@@ -114,22 +114,49 @@ const todayString = computed(() => {
   return formatTodayString(d)
 })
 
-const visibleWeeks = computed(() => {
+// PERFORMANCE: Maintain a manual cache of computed weeks instead of relying on
+// deep reactive tracking of every event & day object. We rebuild lazily when
+// (a) scrolling changes the needed range or (b) eventsMutation counter bumps.
+const visibleWeeks = ref([])
+let lastScrollRange = { startVW: null, endVW: null }
+let pendingRebuild = false
+
+function scheduleRebuild(reason) {
+  if (pendingRebuild) return
+  pendingRebuild = true
+  // Use requestIdleCallback when available, else fallback to rAF
+  const cb = () => {
+    pendingRebuild = false
+    rebuildVisibleWeeks(reason)
+  }
+  if ('requestIdleCallback' in window) {
+    requestIdleCallback(cb, { timeout: 120 })
+  } else {
+    requestAnimationFrame(cb)
+  }
+}
+
+function rebuildVisibleWeeks(reason) {
   const buffer = 10
   const startIdx = Math.floor((scrollTop.value - buffer * rowHeight.value) / rowHeight.value)
   const endIdx = Math.ceil(
     (scrollTop.value + viewportHeight.value + buffer * rowHeight.value) / rowHeight.value,
   )
-
   const startVW = Math.max(minVirtualWeek.value, startIdx + minVirtualWeek.value)
   const endVW = Math.min(maxVirtualWeek.value, endIdx + minVirtualWeek.value)
-
-  const weeks = []
-  for (let vw = startVW; vw <= endVW; vw++) {
-    weeks.push(createWeek(vw))
+  if (
+    reason === 'scroll' &&
+    lastScrollRange.startVW === startVW &&
+    lastScrollRange.endVW === endVW &&
+    visibleWeeks.value.length
+  ) {
+    return
   }
-  return weeks
-})
+  const weeks = []
+  for (let vw = startVW; vw <= endVW; vw++) weeks.push(createWeek(vw))
+  visibleWeeks.value = weeks
+  lastScrollRange = { startVW, endVW }
+}
 
 const contentHeight = computed(() => {
   return totalVirtualWeeks.value * rowHeight.value
@@ -448,9 +475,8 @@ function calculateSelection(anchorStr, otherStr) {
 }
 
 const onScroll = () => {
-  if (viewport.value) {
-    scrollTop.value = viewport.value.scrollTop
-  }
+  if (viewport.value) scrollTop.value = viewport.value.scrollTop
+  scheduleRebuild('scroll')
 }
 
 const handleJogwheelScrollTo = (newScrollTop) => {
@@ -473,6 +499,9 @@ onMounted(() => {
     calendarStore.updateCurrentDate()
   }, 60000)
 
+  // Initial build after mount & measurement
+  scheduleRebuild('init')
+
   onBeforeUnmount(() => {
     clearInterval(timer)
   })
@@ -532,9 +561,25 @@ watch(
       const newScroll = (newTopWeekIndex - minVirtualWeek.value) * rowHeight.value
       scrollTop.value = newScroll
       if (viewport.value) viewport.value.scrollTop = newScroll
+      scheduleRebuild('first-day-change')
     })
   },
 )
+
+// Watch lightweight mutation counter only (not deep events map) and rebuild lazily
+watch(
+  () => calendarStore.events,
+  () => {
+    scheduleRebuild('events')
+  },
+  { deep: true },
+)
+
+// Rebuild if viewport height changes (e.g., resize)
+window.addEventListener('resize', () => {
+  if (viewport.value) viewportHeight.value = viewport.value.clientHeight
+  scheduleRebuild('resize')
+})
 </script>
 
 <template>
diff --git a/src/stores/CalendarStore.js b/src/stores/CalendarStore.js
index bb221f0..e5232f5 100644
--- a/src/stores/CalendarStore.js
+++ b/src/stores/CalendarStore.js
@@ -15,6 +15,9 @@ export const useCalendarStore = defineStore('calendar', {
     today: toLocalString(new Date(), DEFAULT_TZ),
     now: new Date().toISOString(),
     events: new Map(),
+    // Lightweight mutation counter so views can rebuild in a throttled / idle way
+    // without tracking deep reactivity on every event object.
+    eventsMutation: 0,
     weekend: getLocaleWeekendDays(),
     _holidayConfigSignature: null,
     _holidaysInitialized: false,
@@ -107,6 +110,14 @@ export const useCalendarStore = defineStore('calendar', {
       return 'e-' + Math.random().toString(36).slice(2, 10) + '-' + Date.now().toString(36)
     },
 
+    notifyEventsChanged() {
+      // Bump simple counter (wrapping to avoid overflow in extreme long sessions)
+      this.eventsMutation = (this.eventsMutation + 1) % 1_000_000_000
+    },
+    touchEvents() {
+      this.notifyEventsChanged()
+    },
+
     createEvent(eventData) {
       const singleDay = eventData.startDate === eventData.endDate
       const event = {
@@ -125,6 +136,7 @@ export const useCalendarStore = defineStore('calendar', {
         isRepeating: eventData.repeat && eventData.repeat !== 'none',
       }
       this.events.set(event.id, { ...event, isSpanning: event.startDate < event.endDate })
+      this.notifyEventsChanged()
       return event.id
     },
 
@@ -155,6 +167,7 @@ export const useCalendarStore = defineStore('calendar', {
 
     deleteEvent(eventId) {
       this.events.delete(eventId)
+      this.notifyEventsChanged()
     },
 
     deleteFirstOccurrence(baseId) {
@@ -186,6 +199,7 @@ export const useCalendarStore = defineStore('calendar', {
       base.endDate = newEndStr
       if (numericCount !== Infinity) base.repeatCount = String(Math.max(1, numericCount - 1))
       this.events.set(baseId, { ...base, isSpanning: base.startDate < base.endDate })
+      this.notifyEventsChanged()
     },
 
     deleteSingleOccurrence(ctx) {
@@ -231,6 +245,7 @@ export const useCalendarStore = defineStore('calendar', {
         repeatCount: remainingCount,
         repeatWeekdays: snapshot.repeatWeekdays,
       })
+      this.notifyEventsChanged()
     },
 
     deleteFromOccurrence(ctx) {
@@ -242,6 +257,7 @@ export const useCalendarStore = defineStore('calendar', {
         return
       }
       this._terminateRepeatSeriesAtIndex(baseId, occurrenceIndex)
+      this.notifyEventsChanged()
     },
 
     setEventRange(eventId, newStartStr, newEndStr, { mode = 'auto' } = {}) {
@@ -283,6 +299,7 @@ export const useCalendarStore = defineStore('calendar', {
         }
       }
       this.events.set(eventId, { ...snapshot, isSpanning: snapshot.startDate < snapshot.endDate })
+      this.notifyEventsChanged()
     },
 
     splitMoveVirtualOccurrence(baseId, occurrenceDateStr, newStartStr, newEndStr) {
@@ -359,6 +376,7 @@ export const useCalendarStore = defineStore('calendar', {
         repeatCount: remainingCount,
         repeatWeekdays,
       })
+      this.notifyEventsChanged()
     },
 
     splitRepeatSeries(baseId, occurrenceIndex, newStartStr, newEndStr) {
@@ -395,6 +413,7 @@ export const useCalendarStore = defineStore('calendar', {
         const rc = parseInt(ev.repeatCount, 10)
         if (!isNaN(rc)) ev.repeatCount = String(Math.min(rc, index))
       }
+      this.notifyEventsChanged()
     },
   },
   persist: {