diff --git a/frontend/src/App.vue b/frontend/src/App.vue
index 6d454b4..d4bd4dd 100644
--- a/frontend/src/App.vue
+++ b/frontend/src/App.vue
@@ -6,7 +6,7 @@ import {
   Settings, Trash2, X, Repeat2,
 } from 'lucide-vue-next'
 import { buildTaskRrule, defaultTaskDueAt, filterTasks, fromDateTimeLocal, groupTaskTree, moveItemWithinScope, parseTaskRrule, renderMarkdown, toDateTimeLocal, type TaskRepeatConfig } from './lib/task-utils'
-import { formatApiErrorDetail, isTaskView, nextTotalAfterLocalTaskAdd, normalizeRequiredName, readStoredBoolean, readStoredNavigation, shouldToggleRowSwipe, writeCountdownCache, writeStoredBoolean, writeStoredNavigation } from './lib/mvp-utils'
+import { beginLatestRequest, createMutationReconciler, formatApiErrorDetail, isLatestRequest, isTaskView, loadCountdownCache, nextTotalAfterLocalTaskAdd, normalizeRequiredName, readStoredBoolean, readStoredNavigation, runLatestRequest, shouldToggleRowSwipe, startPrimaryWithBackground, writeStoredBoolean, writeStoredNavigation } from './lib/mvp-utils'
 import { csrfHeader } from './lib/csrf'
 import { createCompletionPulse } from './lib/completion-motion'
 import { captureListDragPointer, getAdjacentListMove, hasExceededLongPressMovement, moveListToScope, snapshotListDragPointer, type ListDragPointer } from './lib/list-drag'
@@ -460,13 +460,14 @@ async function loadTodayTaskSummary() {
     todayTaskTotal.value = overdue + open + completed
   } catch { /* 概览统计失败不阻断今天页 */ }
 }
-async function loadOverdueTasks() {
+async function loadOverdueTasks(request = beginLatestRequest('tasks')) {
   const params = new URLSearchParams()
   params.set('due_to', isoAtLocalDayOffset(0))
   params.set('completed', 'false')
-  overdueTasks.value = await loadTaskPages(`/tasks?${params}`)
+  const loaded = await loadTaskPages(`/tasks?${params}`)
+  if (isLatestRequest('tasks', request)) overdueTasks.value = loaded
 }
-async function loadTasksPage() {
+async function loadTasksPage(request = beginLatestRequest('tasks')) {
   const params = new URLSearchParams({ page: String(page.value), page_size: String(pageSize) })
   if (query.value) params.set('q', query.value)
   else if (activeView.value === 'tasks' && activeList.value) params.set('list_id', activeList.value)
@@ -474,6 +475,7 @@ async function loadTasksPage() {
   if (activeView.value === 'upcoming') { params.set('due_from', isoAtLocalDayOffset(0)); params.set('due_to', isoAtLocalDayOffset(8)) }
   if (!showCompleted.value && activeView.value !== 'trash') params.set('completed', 'false')
   const data = await api(`/tasks?${params}`)
+  if (!isLatestRequest('tasks', request)) return
   tasks.value = data.items ?? []
   totalTasks.value = data.total ?? tasks.value.length
   hiddenCompletedTaskCount.value = 0
@@ -483,6 +485,7 @@ async function loadTasksPage() {
     completedParams.set('page_size', '1')
     completedParams.set('completed', 'true')
     const completedData = await api(`/tasks?${completedParams}`)
+    if (!isLatestRequest('tasks', request)) return
     hiddenCompletedTaskCount.value = Number(completedData.total ?? completedData.items?.length ?? 0)
   }
 }
@@ -499,39 +502,67 @@ async function loadNavigation(force = false) {
 }
 async function preloadCountdowns() {
   try {
-    const active = await api('/countdowns')
-    writeCountdownCache(active ?? [], [])
-    const archived = await api('/countdowns?archived=true')
-    writeCountdownCache(active ?? [], archived ?? [])
+    await loadCountdownCache(async () => {
+      const [active, archived] = await Promise.all([api('/countdowns'), api('/countdowns?archived=true')])
+      return { items: active ?? [], archived: archived ?? [] }
+    })
   } catch { /* 倒数日页会在打开时重试 */ }
 }
 async function loadAll() {
-  loading.value = true; error.value = ''
+  const request = beginLatestRequest('tasks')
+  loading.value = true
+  error.value = ''
   try {
     if (!navigationLoaded.value) await loadNavigation()
-    await loadTasksPage()
+    if (!isLatestRequest('tasks', request)) return
     if (activeView.value === 'today') {
-      await loadOverdueTasks()
-      void loadTodayTaskSummary()
-    } else overdueTasks.value = []
-    if (page.value > totalPages.value) { page.value = totalPages.value; await loadTasksPage() }
-  } catch (reason) { fail(reason) } finally { loading.value = false }
+      await startPrimaryWithBackground(
+        [() => loadTasksPage(request), () => loadOverdueTasks(request)],
+        loadTodayTaskSummary,
+      )
+    } else {
+      await loadTasksPage(request)
+      if (isLatestRequest('tasks', request)) overdueTasks.value = []
+    }
+    if (isLatestRequest('tasks', request) && page.value > totalPages.value) {
+      page.value = totalPages.value
+      await loadTasksPage(request)
+    }
+  } catch (reason) {
+    if (isLatestRequest('tasks', request)) fail(reason)
+  } finally {
+    if (isLatestRequest('tasks', request)) loading.value = false
+  }
 }
 async function refreshAll() {
   navigationLoaded.value = false
   await loadAll()
 }
+type TrashPage = { items?: Task[]; total?: number }
 async function loadTrashPage() {
-  const data = await api(`/trash?page=${page.value}&page_size=${pageSize}`)
-  trash.value = data.items ?? []
-  totalTasks.value = data.total ?? trash.value.length
+  return api(`/trash?page=${page.value}&page_size=${pageSize}`) as Promise<TrashPage>
 }
 async function loadTrash() {
-  loading.value = true; error.value = ''
-  try { await loadTrashPage() } catch (reason) { fail(reason) } finally { loading.value = false }
+  loading.value = true
+  error.value = ''
+  await runLatestRequest('trash', loadTrashPage, {
+    success: (data) => {
+      trash.value = data.items ?? []
+      totalTasks.value = data.total ?? trash.value.length
+    },
+    error: fail,
+    finally: () => { loading.value = false },
+  })
 }
 async function switchView(view: View, listId?: string) {
+  taskMutationNavigation.value += 1
   activeView.value = view
+  if (view !== 'trash') beginLatestRequest('trash')
+  if (!isTaskView(view)) {
+    beginLatestRequest('tasks')
+    loading.value = false
+    error.value = ''
+  }
   if (listId) activeList.value = listId
   writeStoredNavigation(window.localStorage, NAVIGATION_STORAGE_KEY, view, activeList.value)
   page.value = 1
@@ -547,8 +578,7 @@ async function switchView(view: View, listId?: string) {
 async function loadTodayView() {
   await loadAll()
 }
-async function patchTask(task: Task, patch: Partial<Task>) {
-  const updated = await api(`/tasks/${task.id}`, { method: 'PATCH', body: JSON.stringify({ ...patch, version: task.version }) })
+function applyTaskUpdate(task: Task, updated: Task) {
   const index = tasks.value.findIndex((item) => item.id === task.id)
   if (index >= 0) tasks.value[index] = { ...tasks.value[index], ...updated }
   const overdueIndex = overdueTasks.value.findIndex((item) => item.id === task.id)
@@ -557,20 +587,29 @@ async function patchTask(task: Task, patch: Partial<Task>) {
     else overdueTasks.value[overdueIndex] = { ...overdueTasks.value[overdueIndex], ...updated }
   }
   if (selectedTask.value?.id === task.id) selectedTask.value = { ...selectedTask.value, ...updated }
-  return updated as Task
 }
+async function patchTask(task: Task, patch: Partial<Task>) {
+  const updated = await api(`/tasks/${task.id}`, { method: 'PATCH', body: JSON.stringify({ ...patch, version: task.version }) }) as Task
+  applyTaskUpdate(task, updated)
+  return updated
+}
+const taskMutationNavigation = ref(0)
+const taskMutationReconciler = createMutationReconciler(
+  () => ({ navigation: taskMutationNavigation.value, view: activeView.value, listId: activeList.value, page: page.value, query: query.value, showCompleted: showCompleted.value }),
+  (left, right) => left.navigation === right.navigation && left.view === right.view && left.listId === right.listId && left.page === right.page && left.query === right.query && left.showCompleted === right.showCompleted,
+  loadAll,
+)
 async function toggle(task: Task) {
   const completing = !task.completed
-  try {
-    await patchTask(task, { completed: completing })
-    if (completing) markTaskJustCompleted(task.id)
-    await loadTasksPage()
-    if (activeView.value === 'today') {
-      await loadOverdueTasks()
-      void loadTodayTaskSummary()
-    }
-    toast(task.completed ? '已重新打开' : '完成啦')
-  } catch (reason) { fail(reason) }
+  await taskMutationReconciler.run(
+    () => api(`/tasks/${task.id}`, { method: 'PATCH', body: JSON.stringify({ completed: completing, version: task.version }) }) as Promise<Task>,
+    () => toast(completing ? '完成啦' : '已重新打开'),
+    fail,
+    (updated) => {
+      applyTaskUpdate(task, updated)
+      if (completing) markTaskJustCompleted(task.id)
+    },
+  )
 }
 function isInteractiveTarget(target: EventTarget | null) {
   return target instanceof Element && Boolean(target.closest('button,input,select,textarea,a,label'))
diff --git a/frontend/src/CountdownPanel.test.ts b/frontend/src/CountdownPanel.test.ts
index 8f761b5..bce876f 100644
--- a/frontend/src/CountdownPanel.test.ts
+++ b/frontend/src/CountdownPanel.test.ts
@@ -44,12 +44,15 @@ describe('countdown modal accessibility', () => {
     expect(source).toContain(':disabled="form.ignore_year"')
   })
 
-  it('shows cached countdowns immediately and refreshes active items first', () => {
+  it('shows cached countdowns immediately and shares one fresh/in-flight refresh', () => {
     expect(source).toContain('readCountdownCache<Countdown>()')
-    expect(source).toContain("const active = await request('/countdowns')")
-    expect(source).toContain("const archivedItems = await request('/countdowns?archived=true')")
-    expect(source).toContain('writeCountdownCache(items.value, archived.value)')
-    expect(source).not.toContain("Promise.all([request('/countdowns'),request('/countdowns?archived=true')])")
+    expect(source).toContain('loadCountdownCache(fetchCountdowns, { force })')
+    expect(source).toContain("request('/countdowns') as Promise<Countdown[]>")
+    expect(source).toContain("request('/countdowns?archived=true') as Promise<Countdown[]>")
+    expect(source).toContain('const generation = getCountdownCacheGeneration()')
+    expect(source).toContain('if (!isCountdownCacheGenerationCurrent(generation)) return')
+    expect(source).toContain('if (isCountdownCacheGenerationCurrent(generation)) error.value=')
+    expect(source).toContain('if (isCountdownCacheGenerationCurrent(generation)) busy.value=false')
   })
 
   it('prevents duplicate submits and sends the edit precondition', () => {
diff --git a/frontend/src/CountdownPanel.vue b/frontend/src/CountdownPanel.vue
index c39ed7f..d55e985 100644
--- a/frontend/src/CountdownPanel.vue
+++ b/frontend/src/CountdownPanel.vue
@@ -2,7 +2,7 @@
 import { computed, nextTick, onBeforeUnmount, onMounted, ref } from 'vue'
 import { Archive, ArchiveRestore, CalendarHeart, ChevronDown, Pencil, Pin, Trash2, X } from 'lucide-vue-next'
 import { csrfHeader } from './lib/csrf'
-import { calendarModeLabel, countdownDayText, countdownKindLabel, dateKey, formatApiErrorDetail, readCountdownCache, writeCountdownCache } from './lib/mvp-utils'
+import { calendarModeLabel, countdownDayText, countdownKindLabel, dateKey, formatApiErrorDetail, getCountdownCacheGeneration, invalidateCountdownCache, isCountdownCacheGenerationCurrent, loadCountdownCache, readCountdownCache } from './lib/mvp-utils'
 
 type Countdown = {
   id: string; title: string; event_date: string; display_date: string; kind: 'countdown'|'anniversary'|'birthday'
@@ -100,23 +100,28 @@ async function request(path:string, options:RequestInit={}) {
   return response.status === 204 ? null : response.json()
 }
 async function safe(work:()=>Promise<void>) { busy.value=true; error.value=''; try { await work() } catch(reason) { error.value=reason instanceof Error ? reason.message : '请求失败' } finally { busy.value=false } }
-async function load() {
+async function fetchCountdowns() {
+  const [active, archivedItems] = await Promise.all([
+    request('/countdowns') as Promise<Countdown[]>,
+    request('/countdowns?archived=true') as Promise<Countdown[]>,
+  ])
+  return { items: active, archived: archivedItems }
+}
+async function load(force = false) {
+  const generation = getCountdownCacheGeneration()
   const cached = readCountdownCache<Countdown>()
   if (cached) { items.value=cached.items; archived.value=cached.archived }
   if (!cached) busy.value=true
   error.value=''
   try {
-    const active = await request('/countdowns') as Countdown[]
-    items.value=active
-    writeCountdownCache(items.value, archived.value)
-    busy.value=false
-    const archivedItems = await request('/countdowns?archived=true') as Countdown[]
-    archived.value=archivedItems
-    writeCountdownCache(items.value, archived.value)
+    const data = await loadCountdownCache(fetchCountdowns, { force })
+    if (!isCountdownCacheGenerationCurrent(generation)) return
+    items.value=data.items
+    archived.value=data.archived
   } catch(reason) {
-    error.value=reason instanceof Error ? reason.message : '请求失败'
+    if (isCountdownCacheGenerationCurrent(generation)) error.value=reason instanceof Error ? reason.message : '请求失败'
   } finally {
-    busy.value=false
+    if (isCountdownCacheGenerationCurrent(generation)) busy.value=false
   }
 }
 function edit(item:Countdown) {
@@ -141,13 +146,13 @@ async function save() {
     if (form.value.calendar_mode==='lunar') { payload.lunar_month=form.value.leap_month ? -form.value.lunar_month : form.value.lunar_month; payload.lunar_day=form.value.lunar_day }
     const path=editingId.value ? `/countdowns/${editingId.value}` : '/countdowns'
     await request(path,{ method:editingId.value?'PATCH':'POST', body:JSON.stringify(payload) })
-    closeDialog(); await load(); emit('notice',editingId.value?'倒数日已更新':'倒数日已添加')
+    invalidateCountdownCache(); closeDialog(); await load(true); emit('notice',editingId.value?'倒数日已更新':'倒数日已添加')
   })
 }
-async function pin(item:Countdown){await safe(async()=>{await request(`/countdowns/${item.id}/pin`,{method:'POST'});detailItem.value=null;await load();emit('notice','已置顶')})}
-async function archiveItem(item:Countdown){await safe(async()=>{await request(`/countdowns/${item.id}`,{method:'DELETE'});detailItem.value=null;await load();emit('notice','已归档')})}
-async function restore(item:Countdown){await safe(async()=>{await request(`/countdowns/${item.id}/restore`,{method:'POST'});await load();emit('notice','已恢复')})}
-async function purge(item:Countdown){if(!confirm(`永久删除“${item.title}”？这个操作不能撤销。`))return;await safe(async()=>{await request(`/countdowns/${item.id}/purge`,{method:'DELETE'});await load();emit('notice','已永久删除')})}
+async function pin(item:Countdown){await safe(async()=>{await request(`/countdowns/${item.id}/pin`,{method:'POST'});invalidateCountdownCache();detailItem.value=null;await load(true);emit('notice','已置顶')})}
+async function archiveItem(item:Countdown){await safe(async()=>{await request(`/countdowns/${item.id}`,{method:'DELETE'});invalidateCountdownCache();detailItem.value=null;await load(true);emit('notice','已归档')})}
+async function restore(item:Countdown){await safe(async()=>{await request(`/countdowns/${item.id}/restore`,{method:'POST'});invalidateCountdownCache();await load(true);emit('notice','已恢复')})}
+async function purge(item:Countdown){if(!confirm(`永久删除“${item.title}”？这个操作不能撤销。`))return;await safe(async()=>{await request(`/countdowns/${item.id}/purge`,{method:'DELETE'});invalidateCountdownCache();await load(true);emit('notice','已永久删除')})}
 function formatDate(value:string){const [y,m,d]=value.split('-');return `${y}年${Number(m)}月${Number(d)}日`}
 function formatDateShort(value:string){const [y,m,d]=value.split('-');return `${y}/${Number(m)}/${Number(d)}`}
 function repeatLabel(value:Countdown['repeat_rule']){return({none:'不重复',weekly:'每周',monthly:'每月',yearly:'每年'})[value]}
@@ -167,7 +172,7 @@ function trapDetailFocus(event: KeyboardEvent) {
 function openFromEmpty(){openCountdownComposer()}
 function openCountdownComposer(origin?: { x: number; y: number }){if(origin)composerOrigin.value=origin;detailItem.value=null;editingId.value=null;editingItem.value=null;showAdvanced.value=false;form.value=freshForm();open.value=true;focusDialog()}
 defineExpose({ openCountdownComposer })
-onMounted(load)
+onMounted(() => { void load() })
 onBeforeUnmount(() => { previousFocus = null })
 </script>
 
diff --git a/frontend/src/MvpPanel.vue b/frontend/src/MvpPanel.vue
index a3061ef..8c3a5db 100644
--- a/frontend/src/MvpPanel.vue
+++ b/frontend/src/MvpPanel.vue
@@ -20,6 +20,7 @@ const emit = defineEmits<{
 const habits = ref<Habit[]>([])
 const archivedHabits = ref<Habit[]>([])
 const showArchivedHabits = ref(false)
+const archivedHabitsLoaded = ref(false)
 const sessions = ref<Session[]>([])
 const audit = ref<any[]>([])
 const busy = ref(false)
@@ -396,7 +397,7 @@ async function archiveHabit(h: Habit) {
     await request(`/habits/${h.id}`, { method: 'DELETE' })
     selectedHabit.value = null
     await loadHabits()
-    await loadArchivedHabits()
+    if (props.view === 'habits' && showArchivedHabits.value) await loadArchivedHabits()
     emit('notice', '习惯已归档')
   })
 }
@@ -411,10 +412,11 @@ async function deleteHabit(h: Habit) {
 }
 async function loadArchivedHabits() {
   archivedHabits.value = await request('/habits?archived=true') as Habit[]
+  archivedHabitsLoaded.value = true
 }
 async function toggleArchivedHabits() {
   showArchivedHabits.value = !showArchivedHabits.value
-  if (showArchivedHabits.value) await safe(loadArchivedHabits)
+  if (showArchivedHabits.value && !archivedHabitsLoaded.value) await safe(loadArchivedHabits)
 }
 function refreshHabitDay() {
   const next = dateKey(new Date())
@@ -505,7 +507,6 @@ onMounted(() => {
   if (props.view === 'habits' || props.view === 'today-habits') {
     refreshHabitDay()
     void loadHabits()
-    void loadArchivedHabits()
     dayRolloverTimer = setInterval(refreshHabitDay, 60_000)
   } else {
     void loadSettings()
@@ -579,10 +580,10 @@ onBeforeUnmount(() => {
           </div>
         </article>
         <div v-if="!visibleHabits.length && !busy" class="empty-panel">{{ !showCompleted && habits.length ? '已完成的习惯已隐藏。' : '还没有习惯，从一件容易坚持的小事开始。' }}</div>
-        <button class="archived-toggle" type="button" @click="toggleArchivedHabits"><ArchiveRestore/>已归档（{{ archivedHabits.length }}）</button>
+        <button class="archived-toggle" type="button" @click="toggleArchivedHabits"><ArchiveRestore/>{{ archivedHabitsLoaded ? `已归档（${archivedHabits.length}）` : '已归档' }}</button>
         <div v-if="showArchivedHabits" class="archived-habits">
           <button v-for="h in archivedHabits" :key="h.id" type="button" @click="openHabitDetail(h, $event.currentTarget as HTMLElement)"><span>{{ h.name }}</span><small>查看详情</small></button>
-          <p v-if="!archivedHabits.length && !busy" class="empty-panel">暂无已归档习惯。</p>
+          <p v-if="archivedHabitsLoaded && !archivedHabits.length && !busy" class="empty-panel">暂无已归档习惯。</p>
         </div>
       </div>
       <Transition name="countdown-detail">
diff --git a/frontend/src/lib/mvp-utils.ts b/frontend/src/lib/mvp-utils.ts
index 80cce8e..d54bdce 100644
--- a/frontend/src/lib/mvp-utils.ts
+++ b/frontend/src/lib/mvp-utils.ts
@@ -153,7 +153,113 @@ export function isFabDrag(deltaX: number, deltaY: number, threshold = 8) {
 }
 
 let habitGridCache: { week: string; habits: unknown[] } | null = null
-let countdownCache: { items: unknown[]; archived: unknown[] } | null = null
+let countdownCache: { items: unknown[]; archived: unknown[]; writtenAt: number } | null = null
+let countdownInFlight: Promise<{ items: unknown[]; archived: unknown[] }> | null = null
+let countdownCacheGeneration = 0
+const requestGenerations = new Map<string, number>()
+
+export function beginLatestRequest(key: string) {
+  const generation = (requestGenerations.get(key) ?? 0) + 1
+  requestGenerations.set(key, generation)
+  return generation
+}
+
+export function isLatestRequest(key: string, generation: number) {
+  return requestGenerations.get(key) === generation
+}
+
+export type RequestContext = { key: string; generation: number }
+
+export function captureRequestContext(key: string): RequestContext {
+  return { key, generation: requestGenerations.get(key) ?? 0 }
+}
+
+export function commitIfRequestContextCurrent(context: RequestContext, commit: () => void) {
+  if (!isLatestRequest(context.key, context.generation)) return false
+  commit()
+  return true
+}
+
+export async function runLatestRequest<T>(
+  key: string,
+  request: () => Promise<T>,
+  callbacks: {
+    success: (value: T) => void
+    error: (reason: unknown) => void
+    finally: () => void
+  },
+) {
+  const generation = beginLatestRequest(key)
+  try {
+    const value = await request()
+    if (isLatestRequest(key, generation)) callbacks.success(value)
+  } catch (reason) {
+    if (isLatestRequest(key, generation)) callbacks.error(reason)
+  } finally {
+    if (isLatestRequest(key, generation)) callbacks.finally()
+  }
+}
+
+export type MutationReconciler<TContext> = {
+  run<T>(
+    mutation: () => Promise<T>,
+    onSuccess: (value: T) => void,
+    onError?: (reason: unknown) => void,
+    onCurrentSuccess?: (value: T) => void,
+  ): Promise<void>
+}
+
+export function createMutationReconciler<TContext>(
+  currentContext: () => TContext,
+  sameContext: (left: TContext, right: TContext) => boolean,
+  refresh: () => Promise<unknown>,
+): MutationReconciler<TContext> {
+  let dirty = 0
+  let reconciled = 0
+  let refreshLoop: Promise<void> | null = null
+
+  const reconcile = (context: TContext) => {
+    if (!sameContext(context, currentContext())) return Promise.resolve()
+    dirty += 1
+    if (!refreshLoop) {
+      refreshLoop = (async () => {
+        while (reconciled < dirty && sameContext(context, currentContext())) {
+          const target = dirty
+          await refresh()
+          if (!sameContext(context, currentContext())) break
+          reconciled = target
+        }
+      })().finally(() => { refreshLoop = null })
+    }
+    return refreshLoop
+  }
+
+  return {
+    async run(mutation, onSuccess, onError, onCurrentSuccess) {
+      const context = currentContext()
+      let value: Awaited<ReturnType<typeof mutation>>
+      try {
+        value = await mutation()
+      } catch (reason) {
+        onError?.(reason)
+        return
+      }
+      onSuccess(value)
+      if (sameContext(context, currentContext())) onCurrentSuccess?.(value)
+      await reconcile(context)
+      if (sameContext(context, currentContext()) && reconciled < dirty) await reconcile(context)
+    },
+  }
+}
+
+export function startPrimaryWithBackground<T>(
+  primary: Array<() => Promise<T>>,
+  background: () => Promise<unknown>,
+) {
+  const pending = primary.map((start) => start())
+  void background().catch(() => undefined)
+  return Promise.all(pending)
+}
 
 export function readHabitGridCache<T>(week: string): T[] | null {
   return habitGridCache?.week === week ? habitGridCache.habits as T[] : null
@@ -164,11 +270,47 @@ export function writeHabitGridCache<T>(week: string, habits: T[]) {
 }
 
 export function readCountdownCache<T>() {
-  return countdownCache as { items: T[]; archived: T[] } | null
+  if (!countdownCache) return null
+  return { items: countdownCache.items as T[], archived: countdownCache.archived as T[] }
 }
 
-export function writeCountdownCache<T>(items: T[], archived: T[]) {
-  countdownCache = { items, archived }
+export function writeCountdownCache<T>(items: T[], archived: T[], now = Date.now()) {
+  countdownCache = { items, archived, writtenAt: now }
+}
+
+export function invalidateCountdownCache() {
+  countdownCacheGeneration += 1
+  countdownCache = null
+  countdownInFlight = null
+}
+
+export function getCountdownCacheGeneration() {
+  return countdownCacheGeneration
+}
+
+export function isCountdownCacheGenerationCurrent(generation: number) {
+  return generation === countdownCacheGeneration
+}
+
+export function loadCountdownCache<T>(
+  fetcher: () => Promise<{ items: T[]; archived: T[] }>,
+  options: { now?: number; maxAge?: number; force?: boolean } = {},
+) {
+  const now = options.now ?? Date.now()
+  const maxAge = options.maxAge ?? 30_000
+  if (!options.force && countdownCache && now - countdownCache.writtenAt < maxAge) {
+    return Promise.resolve(readCountdownCache<T>()!)
+  }
+  if (countdownInFlight) return countdownInFlight as Promise<{ items: T[]; archived: T[] }>
+  const generation = countdownCacheGeneration
+  const pending = fetcher().then((data) => {
+    if (generation === countdownCacheGeneration) writeCountdownCache(data.items, data.archived, now)
+    return data
+  }).finally(() => {
+    if (countdownInFlight === pending) countdownInFlight = null
+  })
+  countdownInFlight = pending as Promise<{ items: unknown[]; archived: unknown[] }>
+  return pending
 }
 
 export type HabitFormValues = {
diff --git a/frontend/src/lib/performance.test.ts b/frontend/src/lib/performance.test.ts
new file mode 100644
index 0000000..8eb3cf6
--- /dev/null
+++ b/frontend/src/lib/performance.test.ts
@@ -0,0 +1,282 @@
+import { readFileSync } from 'node:fs'
+import { describe, expect, it, vi } from 'vitest'
+import {
+  beginLatestRequest,
+  captureRequestContext,
+  commitIfRequestContextCurrent,
+  getCountdownCacheGeneration,
+  invalidateCountdownCache,
+  isCountdownCacheGenerationCurrent,
+  isLatestRequest,
+  loadCountdownCache,
+  readCountdownCache,
+  runLatestRequest,
+  startPrimaryWithBackground,
+  createMutationReconciler,
+} from './mvp-utils'
+
+const app = readFileSync('src/App.vue', 'utf8')
+const habits = readFileSync('src/MvpPanel.vue', 'utf8')
+
+describe('request generation protection', () => {
+  it('allows only the latest task request to commit data, loading, and errors', () => {
+    const first = beginLatestRequest('tasks')
+    const second = beginLatestRequest('tasks')
+    expect(isLatestRequest('tasks', first)).toBe(false)
+    expect(isLatestRequest('tasks', second)).toBe(true)
+  })
+
+  it('does not let a completed mutation supersede newer navigation state', async () => {
+    const task = beginLatestRequest('tasks')
+    const mutation = captureRequestContext('tasks')
+    const events: string[] = []
+    let finishMutation!: () => void
+    const pendingMutation = new Promise<void>((resolve) => { finishMutation = resolve }).then(() => {
+      commitIfRequestContextCurrent(mutation, () => events.push('mutation:refresh'))
+    })
+
+    const navigation = beginLatestRequest('tasks')
+    finishMutation()
+    await pendingMutation
+
+    expect(isLatestRequest('tasks', task)).toBe(false)
+    expect(isLatestRequest('tasks', navigation)).toBe(true)
+    expect(events).toEqual([])
+  })
+
+  it('keeps both success notifications and performs a final refresh for out-of-order mutations', async () => {
+    const events: string[] = []
+    const context = { view: 'today', list: 'inbox' }
+    let resolveFirst!: () => void
+    let resolveSecond!: () => void
+    let releaseRefresh!: () => void
+    const reconciler = createMutationReconciler(
+      () => context,
+      (left, right) => left.view === right.view && left.list === right.list,
+      () => new Promise<void>((resolve) => { events.push('refresh'); releaseRefresh = resolve }),
+    )
+
+    const first = reconciler.run(
+      () => new Promise<void>((resolve) => { resolveFirst = resolve }),
+      () => events.push('success:first'),
+    )
+    const second = reconciler.run(
+      () => new Promise<void>((resolve) => { resolveSecond = resolve }),
+      () => events.push('success:second'),
+    )
+
+    resolveSecond()
+    await Promise.resolve()
+    expect(events).toEqual(['success:second', 'refresh'])
+    resolveFirst()
+    await Promise.resolve()
+    expect(events).toEqual(['success:second', 'refresh', 'success:first'])
+    releaseRefresh()
+    await Promise.resolve()
+    expect(events).toEqual(['success:second', 'refresh', 'success:first', 'refresh'])
+    releaseRefresh()
+    await Promise.all([first, second])
+  })
+
+  it('refreshes again when the first refresh finishes before the second mutation commits', async () => {
+    const events: string[] = []
+    const context = { view: 'today' }
+    let resolveFirstMutation!: () => void
+    let resolveSecondMutation!: () => void
+    let resolveFirstRefresh!: () => void
+    const reconciler = createMutationReconciler(
+      () => context,
+      (left, right) => left.view === right.view,
+      () => {
+        events.push('refresh:start')
+        if (events.filter((event) => event === 'refresh:start').length === 1) {
+          return new Promise<void>((resolve) => { resolveFirstRefresh = resolve })
+        }
+        events.push('refresh:second-done')
+        return Promise.resolve()
+      },
+    )
+
+    const first = reconciler.run(
+      () => new Promise<void>((resolve) => { resolveFirstMutation = resolve }),
+      () => events.push('success:first'),
+    )
+    const second = reconciler.run(
+      () => new Promise<void>((resolve) => { resolveSecondMutation = resolve }),
+      () => events.push('success:second'),
+    )
+    resolveFirstMutation()
+    await Promise.resolve()
+    expect(events).toEqual(['success:first', 'refresh:start'])
+    resolveFirstRefresh()
+    await first
+    resolveSecondMutation()
+    await second
+    expect(events).toEqual(['success:first', 'refresh:start', 'success:second', 'refresh:start', 'refresh:second-done'])
+  })
+
+  it('keeps success feedback but skips reconciliation after navigation changes', async () => {
+    const events: string[] = []
+    let context = { view: 'today' }
+    let resolveMutation!: () => void
+    const reconciler = createMutationReconciler(
+      () => context,
+      (left, right) => left.view === right.view,
+      async () => { events.push('refresh') },
+    )
+    const mutation = reconciler.run(
+      () => new Promise<void>((resolve) => { resolveMutation = resolve }),
+      () => events.push('success'),
+    )
+    context = { view: 'tasks' }
+    resolveMutation()
+    await mutation
+    expect(events).toEqual(['success'])
+  })
+
+  it('prevents stale Trash success, error, and finally callbacks from committing', async () => {
+    const events: string[] = []
+    let finishOld!: (value: string) => void
+    const oldRequest = runLatestRequest('trash',
+      () => new Promise<string>((resolve) => { finishOld = resolve }),
+      {
+        success: (value) => events.push(`old:${value}`),
+        error: () => events.push('old:error'),
+        finally: () => events.push('old:finally'),
+      },
+    )
+    const currentRequest = runLatestRequest('trash',
+      async () => 'new',
+      {
+        success: (value) => events.push(`new:${value}`),
+        error: () => events.push('new:error'),
+        finally: () => events.push('new:finally'),
+      },
+    )
+    await currentRequest
+    finishOld('stale')
+    await oldRequest
+    expect(events).toEqual(['new:new', 'new:finally'])
+  })
+
+  it('prevents a stale Trash rejection from surfacing after a new view starts', async () => {
+    const events: string[] = []
+    let rejectOld!: (reason: Error) => void
+    const oldRequest = runLatestRequest('trash',
+      () => new Promise<void>((_resolve, reject) => { rejectOld = reject }),
+      {
+        success: () => events.push('old:success'),
+        error: () => events.push('old:error'),
+        finally: () => events.push('old:finally'),
+      },
+    )
+    beginLatestRequest('trash')
+    rejectOld(new Error('stale trash failure'))
+    await oldRequest
+    expect(events).toEqual([])
+  })
+
+  it('wires Trash loading through its own generation and invalidates it on exit', () => {
+    const trashBlock = app.slice(app.indexOf('async function loadTrash()'), app.indexOf('async function switchView'))
+    const switchBlock = app.slice(app.indexOf('async function switchView'), app.indexOf('async function loadTodayView'))
+    expect(trashBlock).toContain("await runLatestRequest('trash', loadTrashPage")
+    expect(trashBlock).toContain('success: (data) => {')
+    expect(trashBlock).toContain('error: fail')
+    expect(trashBlock).toContain('finally: () => { loading.value = false }')
+    expect(switchBlock).toContain("if (view !== 'trash') beginLatestRequest('trash')")
+  })
+
+  it('starts Today requests in the same turn without awaiting summary', async () => {
+    const events: string[] = []
+    let finishTasks!: () => void
+    let finishOverdue!: () => void
+    let finishSummary!: () => void
+    const primary = startPrimaryWithBackground(
+      [
+        () => new Promise<void>((resolve) => { events.push('tasks:start'); finishTasks = resolve }),
+        () => new Promise<void>((resolve) => { events.push('overdue:start'); finishOverdue = resolve }),
+      ],
+      () => new Promise<void>((resolve) => { events.push('summary:start'); finishSummary = resolve }),
+    ).then(() => events.push('primary:done'))
+
+    expect(events).toEqual(['tasks:start', 'overdue:start', 'summary:start'])
+    finishTasks()
+    finishOverdue()
+    await primary
+    expect(events).toEqual(['tasks:start', 'overdue:start', 'summary:start', 'primary:done'])
+    finishSummary()
+  })
+
+  it('keeps Today primary completion independent from summary failure', async () => {
+    const primary = startPrimaryWithBackground(
+      [() => Promise.resolve(), () => Promise.resolve()],
+      () => Promise.reject(new Error('summary unavailable')),
+    )
+    await expect(primary).resolves.toEqual([undefined, undefined])
+  })
+})
+
+describe('habit request boundaries', () => {
+  it('never loads archived habits for embedded Today habits and loads them lazily on Habits', () => {
+    const mounted = habits.slice(habits.indexOf('onMounted(() =>'), habits.indexOf('onBeforeUnmount(() =>'))
+    const archiveBlock = habits.slice(habits.indexOf('async function archiveHabit'), habits.indexOf('async function deleteHabit'))
+    expect(mounted).not.toContain('loadArchivedHabits()')
+    expect(archiveBlock).toContain("if (props.view === 'habits' && showArchivedHabits.value)")
+    expect(habits).toContain('if (showArchivedHabits.value && !archivedHabitsLoaded.value)')
+    expect(habits).toContain("{{ archivedHabitsLoaded ? `已归档（${archivedHabits.length}）` : '已归档' }}")
+  })
+
+  it('does not render an empty archive until loading succeeds and allows collapse-reopen retry', () => {
+    const toggleBlock = habits.slice(habits.indexOf('async function toggleArchivedHabits'), habits.indexOf('function refreshHabitDay'))
+    expect(toggleBlock).toContain('showArchivedHabits.value && !archivedHabitsLoaded.value')
+    expect(habits).toContain('v-if="archivedHabitsLoaded && !archivedHabits.length && !busy"')
+    expect(habits).not.toContain('v-if="!archivedHabits.length && !busy" class="empty-panel">暂无已归档习惯。')
+  })
+})
+
+describe('shared countdown cache', () => {
+  it('deduplicates prefetch and mount while a request is in flight', async () => {
+    invalidateCountdownCache()
+    let resolve!: (value: { items: unknown[]; archived: unknown[] }) => void
+    const fetcher = vi.fn(() => new Promise<{ items: unknown[]; archived: unknown[] }>((done) => { resolve = done }))
+    const first = loadCountdownCache(fetcher)
+    const second = loadCountdownCache(fetcher)
+    expect(fetcher).toHaveBeenCalledTimes(1)
+    resolve({ items: [{ id: 'one' }], archived: [] })
+    await expect(first).resolves.toEqual({ items: [{ id: 'one' }], archived: [] })
+    await expect(second).resolves.toEqual({ items: [{ id: 'one' }], archived: [] })
+  })
+
+  it('does not let an invalidated in-flight result overwrite a newer forced load', async () => {
+    invalidateCountdownCache()
+    const oldGeneration = getCountdownCacheGeneration()
+    let resolveOld!: (value: { items: unknown[]; archived: unknown[] }) => void
+    const oldLoad = loadCountdownCache<unknown>(() => new Promise<{ items: unknown[]; archived: unknown[] }>((resolve) => { resolveOld = resolve }))
+
+    invalidateCountdownCache()
+    const newGeneration = getCountdownCacheGeneration()
+    const fresh = { items: [{ id: 'new' }], archived: [{ id: 'new-archived' }] }
+    await expect(loadCountdownCache(async () => fresh, { force: true })).resolves.toEqual(fresh)
+    resolveOld({ items: [{ id: 'old' }], archived: [{ id: 'old-archived' }] })
+    const stale = await oldLoad
+
+    const componentState = { items: fresh.items, archived: fresh.archived }
+    if (isCountdownCacheGenerationCurrent(oldGeneration)) Object.assign(componentState, stale)
+    expect(isCountdownCacheGenerationCurrent(oldGeneration)).toBe(false)
+    expect(isCountdownCacheGenerationCurrent(newGeneration)).toBe(true)
+    expect(componentState).toEqual(fresh)
+    expect(readCountdownCache()).toEqual(fresh)
+  })
+
+  it('reuses fresh data and invalidates it after a write', async () => {
+    invalidateCountdownCache()
+    const fetcher = vi.fn(async () => ({ items: [{ id: 'one' }], archived: [] }))
+    await loadCountdownCache(fetcher, { now: 1000 })
+    await loadCountdownCache(fetcher, { now: 1500 })
+    expect(fetcher).toHaveBeenCalledTimes(1)
+    expect(readCountdownCache()).toEqual({ items: [{ id: 'one' }], archived: [] })
+    invalidateCountdownCache()
+    await loadCountdownCache(fetcher, { now: 1600 })
+    expect(fetcher).toHaveBeenCalledTimes(2)
+  })
+})
diff --git a/frontend/src/style.test.ts b/frontend/src/style.test.ts
index 22f422e..c052277 100644
--- a/frontend/src/style.test.ts
+++ b/frontend/src/style.test.ts
@@ -227,7 +227,7 @@ describe('mobile list row language', () => {
 
   it('provides a minimal archived-habit viewing path', () => {
     expect(mvpPanel).toContain("request('/habits?archived=true')")
-    expect(mvpPanel).toContain('已归档（{{ archivedHabits.length }}）')
+    expect(mvpPanel).toContain("{{ archivedHabitsLoaded ? `已归档（${archivedHabits.length}）` : '已归档' }}")
     expect(mvpPanel).toContain('v-for="h in archivedHabits"')
   })
 
@@ -319,14 +319,13 @@ describe('task and habit row decoration', () => {
     expect(css).toContain('.task-check:focus-visible{')
   })
 
-  it('refreshes the current task data after toggling completion', () => {
+  it('reconciles concurrent completion mutations without suppressing their feedback', () => {
     const toggleBlock = app.slice(app.indexOf('async function toggle(task: Task)'), app.indexOf('function isInteractiveTarget'))
     expect(toggleBlock).toContain('const completing = !task.completed')
-    expect(toggleBlock).toContain('await patchTask(task, { completed: completing })')
-    expect(toggleBlock).toContain('await loadTasksPage()')
-    expect(toggleBlock).toContain("if (activeView.value === 'today')")
-    expect(toggleBlock).toContain('await loadOverdueTasks()')
-    expect(toggleBlock).toContain('void loadTodayTaskSummary()')
+    expect(toggleBlock).toContain('await taskMutationReconciler.run(')
+    expect(toggleBlock).toContain("() => toast(completing ? '完成啦' : '已重新打开')")
+    expect(toggleBlock).toContain('applyTaskUpdate(task, updated)')
+    expect(toggleBlock).not.toContain("beginLatestRequest('tasks')")
   })
 
   it('shows the same visible round check control for boolean and numeric habits in both views', () => {
@@ -634,11 +633,10 @@ describe('unified floating add interaction', () => {
     expect(app).toContain('重复次数')
   })
 
-  it('preloads countdowns after authentication', () => {
+  it('preloads countdowns through the shared cache after authentication', () => {
     expect(app).toContain('void preloadCountdowns()')
-    expect(app).toContain("const active = await api('/countdowns')")
-    expect(app).toContain("const archived = await api('/countdowns?archived=true')")
-    expect(app).toContain('writeCountdownCache(active ?? [], archived ?? [])')
+    expect(app).toContain('await loadCountdownCache(async () =>')
+    expect(app).toContain("Promise.all([api('/countdowns'), api('/countdowns?archived=true')])")
   })
 
   it('reuses one draggable FAB component for task, habit, and countdown views', () => {