diff --git a/src/components/BackupPanel.spec.ts b/src/components/BackupPanel.spec.ts
index 77203bd..85b730a 100644
--- a/src/components/BackupPanel.spec.ts
+++ b/src/components/BackupPanel.spec.ts
@@ -118,6 +118,7 @@ describe('BackupPanel 导入', () => {
 
     expect(store.tasks.map((task) => task.title).sort()).toEqual(['新任务一', '新任务二'])
     expect(wrapper.text()).toContain('已从 backup.json 导入 2 个任务')
+    expect(wrapper.text()).toContain('导入前的数据已自动备份')
   })
 
   it('取消确认后数据保持不变', async () => {
diff --git a/src/components/BackupPanel.vue b/src/components/BackupPanel.vue
index 7b7f493..f68c0d1 100644
--- a/src/components/BackupPanel.vue
+++ b/src/components/BackupPanel.vue
@@ -59,9 +59,13 @@ function confirmImport(): void {
   const target = pending.value
   if (!target) return
 
+  // 记录导入前的数量，用于提示「旧数据已自动备份」是否真的发生了
+  const beforeCount = store.tasks.length
+
   try {
     const count = store.importJson(target.text)
-    message.value = `已从 ${target.fileName} 导入 ${count} 个任务`
+    const backupNote = beforeCount > 0 ? '，导入前的数据已自动备份' : ''
+    message.value = `已从 ${target.fileName} 导入 ${count} 个任务${backupNote}`
     error.value = null
   } catch (cause) {
     error.value = cause instanceof Error ? cause.message : '导入失败'
@@ -71,9 +75,12 @@ function confirmImport(): void {
 }
 
 function restore(key: string): void {
+  const beforeCount = store.tasks.length
   try {
     const count = store.restoreSnapshot(key)
-    message.value = count > 0 ? `已从备份恢复 ${count} 个任务` : '该备份是空的，未做改动'
+    const backupNote = beforeCount > 0 ? '，恢复前的数据已自动备份' : ''
+    message.value =
+      count > 0 ? `已从备份恢复 ${count} 个任务${backupNote}` : '该备份是空的，未做改动'
     error.value = null
   } catch (cause) {
     error.value = cause instanceof Error ? cause.message : '恢复失败'
@@ -137,7 +144,8 @@ function formatTime(iso: string): string {
         >
           <p class="text-sm text-amber-900 dark:text-amber-200">
             将从「{{ pending.fileName }}」导入 {{ pending.count }} 个任务，
-            <strong>并覆盖当前全部 {{ store.tasks.length }} 个任务</strong>。此操作不可撤销。
+            <strong>并覆盖当前全部 {{ store.tasks.length }} 个任务</strong>。 覆盖前会自动把当前数据
+            存一份到下方「自动备份」，选错文件也能从那里恢复。
           </p>
           <div class="flex gap-2">
             <button
diff --git a/src/data/schema.spec.ts b/src/data/schema.spec.ts
index 9b08248..a43a91e 100644
--- a/src/data/schema.spec.ts
+++ b/src/data/schema.spec.ts
@@ -123,6 +123,17 @@ describe('coerceTaskList', () => {
     expect(coerceTaskList(null)).toEqual([])
     expect(coerceTaskList({})).toEqual([])
   })
+
+  it('重复 id 只保留先出现的那条', () => {
+    const list = coerceTaskList([
+      validTask({ id: 'dup', title: '第一条' }),
+      validTask({ id: 'dup', title: '第二条' }),
+      validTask({ id: 'other' }),
+    ])
+
+    expect(list.map((task) => task.id)).toEqual(['dup', 'other'])
+    expect(list[0]?.title).toBe('第一条')
+  })
 })
 
 describe('parsePersistedState', () => {
@@ -240,6 +251,18 @@ describe('导入校验（严格）', () => {
     )
   })
 
+  it('id 重复时整体拒绝，并指出重复的两条', () => {
+    const duplicated = [
+      validTask({ id: 'same' }),
+      validTask({ id: 'other' }),
+      validTask({ id: 'same' }),
+    ]
+
+    expect(() => validateImportPayload({ tasks: duplicated })).toThrow(
+      /第 3 条与第 1 条任务的 id 相同（same）/,
+    )
+  })
+
   it('缺少 tasks 数组时抛错', () => {
     expect(() => validateImportPayload({ schemaVersion: 1 })).toThrow(/缺少 tasks 数组/)
   })
diff --git a/src/data/schema.ts b/src/data/schema.ts
index 02a9beb..cfa9b0e 100644
--- a/src/data/schema.ts
+++ b/src/data/schema.ts
@@ -66,9 +66,7 @@ export function coerceTask(value: unknown): Task | null {
   if (!isPriority(priority)) return null
 
   const rawTags = Array.isArray(value.tags) ? value.tags : []
-  const tags = rawTags.filter(
-    (tag): tag is string => typeof tag === 'string' && tag.trim() !== '',
-  )
+  const tags = rawTags.filter((tag): tag is string => typeof tag === 'string' && tag.trim() !== '')
 
   const dueDate = value.dueDate
   const sortOrder = value.sortOrder
@@ -96,9 +94,15 @@ export function coerceTask(value: unknown): Task | null {
 export function coerceTaskList(value: unknown): Task[] {
   if (!Array.isArray(value)) return []
   const tasks: Task[] = []
+  const seen = new Set<string>()
   for (const item of value) {
     const task = coerceTask(item)
-    if (task) tasks.push(task)
+    if (!task) continue
+    // 重复 id 会让 Vue 的 :key 冲突、findIndex 只命中第一条，
+    // 宽容读取时保留先出现的那条，丢弃后续重复项。
+    if (seen.has(task.id)) continue
+    seen.add(task.id)
+    tasks.push(task)
   }
   return tasks
 }
@@ -195,11 +199,22 @@ export function validateImportPayload(value: unknown): Task[] {
   }
 
   const tasks: Task[] = []
+  /** 记录每个 id 首次出现的下标，用于给出「第 N 条与第 M 条重复」的定位信息 */
+  const firstIndexById = new Map<string, number>()
   value.tasks.forEach((item, index) => {
     const task = coerceTask(item)
     if (!task) {
       throw new DataValidationError(`第 ${index + 1} 条任务格式不合法，已取消导入`)
     }
+
+    const firstIndex = firstIndexById.get(task.id)
+    if (firstIndex !== undefined) {
+      throw new DataValidationError(
+        `第 ${index + 1} 条与第 ${firstIndex + 1} 条任务的 id 相同（${task.id}），已取消导入`,
+      )
+    }
+
+    firstIndexById.set(task.id, index)
     tasks.push(task)
   })
   return tasks
diff --git a/src/data/snapshot.spec.ts b/src/data/snapshot.spec.ts
index 46ff3fd..15641a2 100644
--- a/src/data/snapshot.spec.ts
+++ b/src/data/snapshot.spec.ts
@@ -129,6 +129,17 @@ describe('writeSnapshot', () => {
     expect(listSnapshots(storage)).toHaveLength(1)
   })
 
+  it('同一时间点重复写入不会产生重复索引项', () => {
+    const storage = createFakeStorage()
+    writeSnapshot(storage, [makeTask('a')], at(0))
+    writeSnapshot(storage, [makeTask('b')], at(0))
+
+    expect(listSnapshots(storage)).toHaveLength(1)
+    expect(readSnapshot(storage, `${SNAPSHOT_KEY_PREFIX}${at(0).toISOString()}`)).toEqual([
+      makeTask('b'),
+    ])
+  })
+
   it('存储写入失败时返回 null 而不抛错', () => {
     const storage: StorageLike = {
       getItem: () => null,
diff --git a/src/data/snapshot.ts b/src/data/snapshot.ts
index b252acb..b42dd65 100644
--- a/src/data/snapshot.ts
+++ b/src/data/snapshot.ts
@@ -10,7 +10,12 @@
 
 import type { Task } from '@/types/task'
 
-import { DataValidationError, SNAPSHOT_KEY_PREFIX, parsePersistedState, serializeState } from './schema'
+import {
+  DataValidationError,
+  SNAPSHOT_KEY_PREFIX,
+  parsePersistedState,
+  serializeState,
+} from './schema'
 import type { StorageLike } from './storage'
 
 /**
@@ -71,7 +76,11 @@ export function writeSnapshot(
     return null
   }
 
-  const next = [{ key, savedAt }, ...previous].slice(0, Math.max(1, keep))
+  const next = [
+    { key, savedAt },
+    // 同一毫秒内重复写入会产生相同 key，先剔除旧条目避免索引里出现重复项
+    ...previous.filter((info) => info.key !== key),
+  ].slice(0, Math.max(1, keep))
   const keptKeys = new Set(next.map((info) => info.key))
 
   for (const info of previous) {
diff --git a/src/stores/tasks.spec.ts b/src/stores/tasks.spec.ts
index b80de8b..aef273f 100644
--- a/src/stores/tasks.spec.ts
+++ b/src/stores/tasks.spec.ts
@@ -1,7 +1,8 @@
 import { createPinia, setActivePinia } from 'pinia'
-import { describe, expect, it } from 'vitest'
+import { describe, expect, it, vi } from 'vitest'
 
 import { createMemoryTaskRepository, type TaskRepository } from '@/data/taskRepository'
+import type { Task } from '@/types/task'
 
 import { useTaskStore } from './tasks'
 
@@ -64,7 +65,9 @@ describe('初始化', () => {
     const store = freshStore()
     store.createTask({ title: 'A', tags: ['前端', '设计'] })
     store.createTask({ title: 'B', status: 'doing', tags: ['设计', 'Bug'] })
-    expect(store.allTags).toEqual(['Bug', '前端', '设计'].sort((a, b) => a.localeCompare(b, 'zh-Hans-CN')))
+    expect(store.allTags).toEqual(
+      ['Bug', '前端', '设计'].sort((a, b) => a.localeCompare(b, 'zh-Hans-CN')),
+    )
   })
 
   it('没有任务时 allTags 为空数组', () => {
@@ -285,6 +288,30 @@ describe('持久化', () => {
     const second = freshStore(repository)
     expect(second.tasks).toHaveLength(0)
   })
+
+  it('写入失败时标记为非持久化并提示，恢复后自动清除', () => {
+    const base = createMemoryTaskRepository()
+    let shouldFail = true
+    const repository: TaskRepository = {
+      ...base,
+      save(tasks) {
+        if (shouldFail) throw new Error('写入本地存储失败：QuotaExceededError')
+        base.save(tasks)
+      },
+    }
+
+    const store = freshStore(repository)
+    store.createTask({ title: 'A' })
+
+    expect(store.persistent).toBe(false)
+    expect(store.notice).toContain('QuotaExceededError')
+
+    shouldFail = false
+    store.createTask({ title: 'B' })
+
+    expect(store.persistent).toBe(true)
+    expect(store.notice).toBeNull()
+  })
 })
 
 describe('导出与导入', () => {
@@ -330,6 +357,74 @@ describe('导出与导入', () => {
     store.importJson(payload)
     expect(titles(store.tasks)).toEqual(['新数据'])
   })
+
+  it('导入前会把当前数据写入快照，误导入可恢复', () => {
+    vi.useFakeTimers()
+    try {
+      vi.setSystemTime(new Date('2026-10-19T00:00:00.000Z'))
+      const store = freshStore()
+      store.createTask({ title: '导入前的旧任务' })
+      expect(store.snapshots).toHaveLength(0)
+
+      vi.setSystemTime(new Date('2026-10-19T00:00:01.000Z'))
+      const count = store.importJson(
+        JSON.stringify({
+          schemaVersion: 2,
+          tasks: [{ id: 'new', title: '新任务', status: 'todo', priority: 2, sortOrder: 1024 }],
+        }),
+      )
+
+      expect(count).toBe(1)
+      expect(titles(store.tasks)).toEqual(['新任务'])
+      expect(store.snapshots).toHaveLength(1)
+
+      const key = store.snapshots[0]?.key ?? ''
+      expect(key).not.toBe('')
+      expect(store.restoreSnapshot(key)).toBe(1)
+      expect(titles(store.tasks)).toEqual(['导入前的旧任务'])
+    } finally {
+      vi.useRealTimers()
+    }
+  })
+
+  it('恢复快照前会先备份当前数据', () => {
+    vi.useFakeTimers()
+    try {
+      vi.setSystemTime(new Date('2026-10-19T00:00:00.000Z'))
+      const repository = createMemoryTaskRepository()
+      const store = freshStore(repository)
+      store.createTask({ title: '当前任务' })
+
+      const oldTask: Task = {
+        id: 'old',
+        title: '快照里的旧任务',
+        description: '',
+        status: 'todo',
+        priority: 2,
+        tags: [],
+        dueDate: null,
+        sortOrder: 1024,
+        createdAt: '2026-10-18T00:00:00.000Z',
+        updatedAt: '2026-10-18T00:00:00.000Z',
+        completedAt: null,
+        archivedAt: null,
+      }
+
+      vi.setSystemTime(new Date('2026-10-19T00:00:01.000Z'))
+      const snapshot = repository.snapshot([oldTask])
+      store.refreshSnapshots()
+
+      vi.setSystemTime(new Date('2026-10-19T00:00:02.000Z'))
+      expect(store.restoreSnapshot(snapshot?.key ?? '')).toBe(1)
+      expect(titles(store.tasks)).toEqual(['快照里的旧任务'])
+
+      // 恢复前的「当前任务」也应留下备份，而不是被静默覆盖
+      const backedUp = store.snapshots.map((info) => titles(repository.restoreSnapshot(info.key)))
+      expect(backedUp.some((items) => items.includes('当前任务'))).toBe(true)
+    } finally {
+      vi.useRealTimers()
+    }
+  })
 })
 
 describe('归档', () => {
diff --git a/src/stores/tasks.ts b/src/stores/tasks.ts
index 57812d2..3404ea8 100644
--- a/src/stores/tasks.ts
+++ b/src/stores/tasks.ts
@@ -19,7 +19,12 @@ import {
 } from '@/data/taskRepository'
 import { DEFAULT_PRIORITY, type ColumnId, type Priority, type Task } from '@/types/task'
 import { createId } from '@/utils/id'
-import { groupByColumn, moveWithinColumn, sortByOrder, sortOrderForPosition } from '@/utils/sortOrder'
+import {
+  groupByColumn,
+  moveWithinColumn,
+  sortByOrder,
+  sortOrderForPosition,
+} from '@/utils/sortOrder'
 
 /** 跨标签页同步使用的频道名 */
 export const SYNC_CHANNEL_NAME = 'kanban.sync'
@@ -105,7 +110,14 @@ export const useTaskStore = defineStore('tasks', () => {
     if (!repository) return
     try {
       repository.save(tasks.value)
+      // 之前写入失败过，现在恢复了：把告警撤掉，避免一直吓唬用户。
+      // 读取失败（数据损坏）时 persistent 仍是 true，不会被这里误清。
+      if (!persistent.value) {
+        persistent.value = true
+        notice.value = null
+      }
     } catch (error) {
+      persistent.value = false
       notice.value = error instanceof Error ? error.message : '保存失败'
     }
   }
@@ -158,11 +170,35 @@ export const useTaskStore = defineStore('tasks', () => {
     refreshSnapshots()
   }
 
+  /**
+   * 覆盖式操作（导入 / 恢复快照）执行前，把当前数据留一份快照。
+   *
+   * 这两类操作会整份替换内存与落盘数据，一旦选错文件或选错快照，
+   * 用户原本的数据就没有退路了。先快照一份，配合「备份与恢复」面板，
+   * 把不可逆操作变成可逆。
+   *
+   * @returns 是否真的写入了快照（空看板或存储不可用时跳过）
+   */
+  function snapshotBeforeOverwrite(): boolean {
+    if (!repository || !persistent.value || tasks.value.length === 0) return false
+    try {
+      repository.snapshot(tasks.value)
+      refreshSnapshots()
+      return true
+    } catch {
+      // 快照只是兜底，失败不应阻断主流程
+      return false
+    }
+  }
+
   /** 从快照恢复；返回实际恢复的任务数 */
   function restoreSnapshot(key: string): number {
     if (!repository) return 0
     const restored = repository.restoreSnapshot(key)
     if (restored.length === 0) return 0
+    // 先读快照再备份当前数据：即使备份把这份快照挤出保留窗口，
+    // 待恢复的内容也已经拿在手里。
+    snapshotBeforeOverwrite()
     tasks.value = sortByOrder(restored)
     commit()
     return restored.length
@@ -189,8 +225,7 @@ export const useTaskStore = defineStore('tasks', () => {
       } catch (error) {
         repository = createMemoryTaskRepository()
         persistent.value = false
-        notice.value =
-          error instanceof Error ? error.message : '本地存储不可用，本次改动不会被保存'
+        notice.value = error instanceof Error ? error.message : '本地存储不可用，本次改动不会被保存'
       }
     }
 
@@ -338,10 +373,13 @@ export const useTaskStore = defineStore('tasks', () => {
 
   /**
    * 覆盖式导入（T14）。校验失败会抛错，此时现有数据保持不变。
+   * 校验通过后、覆盖之前会自动留一份快照，误导入可以回到导入前的状态。
    * @returns 成功导入的任务数量
    */
   function importJson(raw: string): number {
     const imported = parseImportJson(raw)
+    // 先解析再备份：非法文件不应该产生任何副作用
+    snapshotBeforeOverwrite()
     tasks.value = sortByOrder(imported)
     commit()
     return imported.length