diff --git a/src/renderer/src/App.tsx b/src/renderer/src/App.tsx
index 7fa6827..3a6d517 100644
--- a/src/renderer/src/App.tsx
+++ b/src/renderer/src/App.tsx
@@ -75,6 +75,19 @@ function loadPrefs(): { options: DiffOptions; onlyDiff: boolean } {
 /** 计算中/无内容时的空统计（保持状态栏与徽章渲染稳定） */
 const EMPTY_SUMMARY: DiffSummary = { changedLines: 0, inserted: 0, deleted: 0, modified: 0 }
 
+/** toast 队列元素 */
+interface ToastItem {
+  id: number
+  text: string
+  action?: { label: string; onClick: () => void }
+}
+
+/** toast 队列上限：超出时顶掉最旧的一条 */
+const TOAST_MAX = 3
+
+/** 清空二次确认窗口时长：第一次点击后在此时间内再点确认，超时自动复位 */
+const CLEAR_CONFIRM_MS = 3000
+
 interface PaneState {
   meta: PaneMeta
   path: string
@@ -132,14 +145,16 @@ function EmptyPane({
 export default function App(): ReactElement {
   const [paneL, setPaneL] = useState<PaneState | null>(null)
   const [paneR, setPaneR] = useState<PaneState | null>(null)
-  // 比较选项与视图开关：初始值从持久化偏好恢复（惰性求值，每次挂载重新读取）
-  const [options, setOptions] = useState<DiffOptions>(() => loadPrefs().options)
+  // 偏好只读一次盘：两个初始 state 共享同一次 loadPrefs 结果（原实现挂载期读取两次）
+  const [initialPrefs] = useState(() => loadPrefs())
+  // 比较选项与视图开关：初始值从持久化偏好恢复
+  const [options, setOptions] = useState<DiffOptions>(initialPrefs.options)
   // 仅看差异：视图层过滤选项（不影响比较语义，也与报告导出无关，报告始终全量行）
-  const [onlyDiff, setOnlyDiff] = useState<boolean>(() => loadPrefs().onlyDiff)
+  const [onlyDiff, setOnlyDiff] = useState<boolean>(initialPrefs.onlyDiff)
   const [activeRowId, setActiveRowId] = useState<string | null>(null)
   const [navIndex, setNavIndex] = useState(0)
   const [menu, setMenu] = useState<{ x: number; y: number; items: ContextMenuItem[] } | null>(null)
-  const [toast, setToast] = useState<{ text: string; action?: { label: string; onClick: () => void } } | null>(null)
+  const [toasts, setToasts] = useState<ToastItem[]>([])
   const [pasteSide, setPasteSide] = useState<'left' | 'right' | null>(null)
   const [pasteOpen, setPasteOpen] = useState(false)
   const pasteWrapRef = useRef<HTMLDivElement>(null)
@@ -147,22 +162,43 @@ export default function App(): ReactElement {
   // 点击外部 / 按 Esc 关闭粘贴下拉
   useDismiss(pasteWrapRef, closePaste)
 
-  // toast 定时器：新提示先清掉旧定时器，避免前一条把后一条提前清空
-  const toastTimer = useRef<number | null>(null)
+  // toast 队列：最多同时展示 3 条，各自独立计时互不清除
+  // （此前单条覆盖式会互顶：二进制乱码预警被行数预警立即顶掉，用户看不到前一条）
+  const toastSeq = useRef(0)
+  const toastTimers = useRef(new Map<number, number>())
 
   const showToast = useCallback(
     (text: string, action?: { label: string; onClick: () => void }) => {
-      setToast({ text, action })
-      if (toastTimer.current !== null) window.clearTimeout(toastTimer.current)
-      toastTimer.current = window.setTimeout(() => setToast(null), 3600)
+      const id = ++toastSeq.current
+      setToasts((prev) => {
+        const next = [...prev, { id, text, action }]
+        // 超出上限时顶掉最旧的一条（其定时器到期后空过滤，无副作用）
+        return next.length > TOAST_MAX ? next.slice(next.length - TOAST_MAX) : next
+      })
+      const timer = window.setTimeout(() => {
+        setToasts((prev) => prev.filter((t) => t.id !== id))
+        toastTimers.current.delete(id)
+      }, 3600)
+      toastTimers.current.set(id, timer)
     },
     []
   )
 
-  // 卸载时清理定时器，避免泄漏
+  const dismissToast = useCallback((id: number): void => {
+    const timer = toastTimers.current.get(id)
+    if (timer !== undefined) {
+      window.clearTimeout(timer)
+      toastTimers.current.delete(id)
+    }
+    setToasts((prev) => prev.filter((t) => t.id !== id))
+  }, [])
+
+  // 卸载时清理全部定时器，避免泄漏
   useEffect(() => {
+    const timers = toastTimers.current
     return () => {
-      if (toastTimer.current !== null) window.clearTimeout(toastTimer.current)
+      timers.forEach((t) => window.clearTimeout(t))
+      timers.clear()
     }
   }, [])
 
@@ -304,6 +340,37 @@ export default function App(): ReactElement {
     setPaneR(paneL)
   }, [paneL, paneR])
 
+  // 清空二次确认：两侧有内容时第一次点击仅提示，确认窗口内再点才真正清空
+  // （文件可重新打开，粘贴输入的手动文本无法恢复，需防误触）
+  const clearArmedRef = useRef(false)
+  const clearTimer = useRef<number | null>(null)
+
+  const handleClear = useCallback((): void => {
+    // 空态无内容，无需确认成本
+    if (paneL === null && paneR === null) return
+    if (clearArmedRef.current) {
+      if (clearTimer.current !== null) window.clearTimeout(clearTimer.current)
+      clearArmedRef.current = false
+      clearTimer.current = null
+      setPaneL(null)
+      setPaneR(null)
+      return
+    }
+    clearArmedRef.current = true
+    showToast('再次点击“清空”将移除两侧内容')
+    clearTimer.current = window.setTimeout(() => {
+      clearArmedRef.current = false
+      clearTimer.current = null
+    }, CLEAR_CONFIRM_MS)
+  }, [paneL, paneR, showToast])
+
+  // 卸载时清理确认窗口定时器
+  useEffect(() => {
+    return () => {
+      if (clearTimer.current !== null) window.clearTimeout(clearTimer.current)
+    }
+  }, [])
+
   // diff 内容或视图选项变化时重置导航
   useEffect(() => {
     setNavIndex(0)
@@ -472,13 +539,7 @@ export default function App(): ReactElement {
             </div>
           )}
         </div>
-        <button
-          className="btn ghost"
-          onClick={() => {
-            setPaneL(null)
-            setPaneR(null)
-          }}
-        >
+        <button className="btn ghost" onClick={handleClear}>
           清空
         </button>
       </header>
@@ -554,20 +615,24 @@ export default function App(): ReactElement {
           onConfirm={(t) => confirmPaste(pasteSide, t)}
         />
       )}
-      {toast && (
-        <div className="toast">
-          <span className="toast-text">{toast.text}</span>
-          {toast.action && (
-            <button
-              className="toast-btn"
-              onClick={() => {
-                toast.action!.onClick()
-                setToast(null)
-              }}
-            >
-              {toast.action.label}
-            </button>
-          )}
+      {toasts.length > 0 && (
+        <div className="toast-wrap">
+          {toasts.map((t) => (
+            <div className="toast" key={t.id}>
+              <span className="toast-text">{t.text}</span>
+              {t.action && (
+                <button
+                  className="toast-btn"
+                  onClick={() => {
+                    t.action!.onClick()
+                    dismissToast(t.id)
+                  }}
+                >
+                  {t.action.label}
+                </button>
+              )}
+            </div>
+          ))}
         </div>
       )}
     </div>
diff --git a/src/renderer/src/__tests__/App.test.tsx b/src/renderer/src/__tests__/App.test.tsx
index 0284167..987ac58 100644
--- a/src/renderer/src/__tests__/App.test.tsx
+++ b/src/renderer/src/__tests__/App.test.tsx
@@ -147,15 +147,60 @@ describe('App - 差异导航与清空', () => {
     expect(screen.getByText('2 / 2')).toBeInTheDocument()
   })
 
-  it('点击清空恢复空态', async () => {
+  it('点击清空恢复空态（二次确认后执行）', async () => {
     render(<App />)
     fireEvent.click(screen.getByText('打开左侧'))
     await screen.findByText('导出报告')
     fireEvent.click(screen.getByText('清空'))
+    expect(await screen.findByText(/再次点击/)).toBeInTheDocument()
+    fireEvent.click(screen.getByText('清空'))
     expect(await screen.findByText(/选择左侧文件/)).toBeInTheDocument()
   })
 })
 
+describe('App - 清空二次确认', () => {
+  it('有内容时第一次点击仅提示，不清空', async () => {
+    render(<App />)
+    fireEvent.click(screen.getByText('打开左侧'))
+    await screen.findByText('导出报告')
+    fireEvent.click(screen.getByText('清空'))
+    expect(await screen.findByText(/再次点击“清空”将移除两侧内容/)).toBeInTheDocument()
+    // 未清空：对比视图仍在
+    expect(screen.getByText('导出报告')).toBeInTheDocument()
+  })
+
+  it('确认窗口超时后自动复位（再点一次仍先提示）', async () => {
+    vi.useFakeTimers()
+    render(<App />)
+    await act(async () => {
+      fireEvent.click(screen.getByText('打开左侧'))
+    })
+    expect(screen.getByText('导出报告')).toBeInTheDocument()
+    await act(async () => {
+      fireEvent.click(screen.getByText('清空'))
+    })
+    expect(screen.getAllByText(/再次点击/).length).toBeGreaterThan(0)
+    // 超过确认窗口 + toast 自身寿命：复位且提示消失
+    act(() => {
+      vi.advanceTimersByTime(4000)
+    })
+    expect(screen.queryByText(/再次点击/)).not.toBeInTheDocument()
+    // 复位后再点击仍是“先提示”而非直接清空
+    await act(async () => {
+      fireEvent.click(screen.getByText('清空'))
+    })
+    expect(screen.getAllByText(/再次点击/).length).toBeGreaterThan(0)
+    expect(screen.getByText('导出报告')).toBeInTheDocument()
+  })
+
+  it('空态时点击清空不弹确认（无内容无确认成本）', () => {
+    render(<App />)
+    fireEvent.click(screen.getByText('清空'))
+    expect(screen.queryByText(/再次点击/)).not.toBeInTheDocument()
+    expect(screen.getByText(/选择左侧文件/)).toBeInTheDocument()
+  })
+})
+
 describe('App - 空态打开按钮', () => {
   it('点击空面板的打开文件按钮加载左侧文件', async () => {
     render(<App />)
@@ -257,6 +302,75 @@ describe('App - 提示与容错', () => {
     expect(screen.queryByText(/仅支持文本文件：b.png/)).not.toBeInTheDocument()
   })
 
+  it('两条提示同时可见（队列化不互顶），各自独立消失', () => {
+    vi.useFakeTimers()
+    render(<App />)
+    const pane = screen.getByText(/选择左侧文件/).closest('.pane-empty') as Element
+    fireEvent.drop(pane, {
+      dataTransfer: { files: [new File(['x'], 'a.png', { type: 'image/png' })] }
+    })
+    fireEvent.drop(pane, {
+      dataTransfer: { files: [new File(['x'], 'b.png', { type: 'image/png' })] }
+    })
+    // 两条都在队列中同时展示
+    expect(screen.getByText(/仅支持文本文件：a.png/)).toBeInTheDocument()
+    expect(screen.getByText(/仅支持文本文件：b.png/)).toBeInTheDocument()
+    act(() => {
+      vi.advanceTimersByTime(3700)
+    })
+    expect(screen.queryByText(/仅支持文本文件：a.png/)).not.toBeInTheDocument()
+    expect(screen.queryByText(/仅支持文本文件：b.png/)).not.toBeInTheDocument()
+  })
+
+  it('二进制乱码预警与行数预警同时可见（原单条覆盖式会互顶）', async () => {
+    window.api = mockApi({
+      openFile: async () => ({
+        path: '/tmp/bin.log',
+        name: 'bin.log',
+        text: Array.from({ length: 50001 }, () => 'x').join('\n'),
+        encoding: 'GBK',
+        binary: true
+      })
+    })
+    render(<App />)
+    fireEvent.click(screen.getByText('打开左侧'))
+    expect(await screen.findByText(/疑似二进制文件/)).toBeInTheDocument()
+    expect(screen.getByText(/行数较多/)).toBeInTheDocument()
+  })
+
+  it('提示超过 3 条时最旧的一条被顶掉', () => {
+    vi.useFakeTimers()
+    render(<App />)
+    const pane = screen.getByText(/选择左侧文件/).closest('.pane-empty') as Element
+    const names = ['a.png', 'b.png', 'c.png', 'd.png']
+    for (const n of names) {
+      fireEvent.drop(pane, {
+        dataTransfer: { files: [new File(['x'], n, { type: 'image/png' })] }
+      })
+    }
+    expect(screen.queryByText(/仅支持文本文件：a.png/)).not.toBeInTheDocument()
+    expect(screen.getByText(/仅支持文本文件：b.png/)).toBeInTheDocument()
+    expect(screen.getByText(/仅支持文本文件：c.png/)).toBeInTheDocument()
+    expect(screen.getByText(/仅支持文本文件：d.png/)).toBeInTheDocument()
+  })
+
+  it('点击 toast 动作按钮后该条立即消失', async () => {
+    const showInFolder = vi.fn(async () => true)
+    window.api = mockApi({
+      saveReport: async () => ({ ok: true, path: 'C:/docs/DiffLens-report.html' }),
+      showInFolder
+    })
+    render(<App />)
+    fireEvent.click(screen.getByText('打开左侧'))
+    await screen.findByText('导出报告')
+    fireEvent.click(screen.getByText('导出报告'))
+    fireEvent.click(screen.getByText('HTML 报告'))
+    expect(await screen.findByText(/报告已保存/)).toBeInTheDocument()
+    fireEvent.click(screen.getByText('打开文件夹'))
+    expect(showInFolder).toHaveBeenCalled()
+    expect(screen.queryByText(/报告已保存/)).not.toBeInTheDocument()
+  })
+
   it('文件超过 10MB 时被拦截并保持空态', async () => {
     window.api = mockApi({
       openFile: async () => ({ error: 'too-large', name: 'big.log', size: 11 * 1024 * 1024 })
diff --git a/src/renderer/src/diff/diffEngine.ts b/src/renderer/src/diff/diffEngine.ts
index 9283072..de69303 100644
--- a/src/renderer/src/diff/diffEngine.ts
+++ b/src/renderer/src/diff/diffEngine.ts
@@ -291,6 +291,14 @@ function computeLineDiff(
  */
 export const CHAR_DIFF_MAX_CHARS = 200000
 
+/**
+ * 字符级对比的重输入阈值（两侧原始字符总量）：超过即走 worker 后台计算。
+ * 按 CHAR_DIFF_MAX_CHARS / 4 取值——降级上限之内仍可能出现编辑距离极大、
+ * O(ND) 耗时失控的输入，且此类输入往往行数很少（压缩 JSON / base64 单行），
+ * 行数维度的重输入判定防不住，需以字符量兜底。
+ */
+export const CHAR_HEAVY_INPUT_CHARS = CHAR_DIFF_MAX_CHARS / 4
+
 /** 空白字符判定：与 ignoreAllWhitespace 的 \s 语义一致（含换行、制表符、全角空格） */
 function isWsChar(ch: string): boolean {
   return /\s/.test(ch)
diff --git a/src/renderer/src/hooks/useDiff.test.ts b/src/renderer/src/hooks/useDiff.test.ts
index fdedbf8..917e427 100644
--- a/src/renderer/src/hooks/useDiff.test.ts
+++ b/src/renderer/src/hooks/useDiff.test.ts
@@ -46,6 +46,8 @@ function heavyText(lines: number): string {
 // 注意：renderHook 回调内联对象（如 {}）会在每次渲染生成新引用并触发 effect 双跑，
 // 测试中必须将 left/right/options 提升为稳定引用（生产中 options 为 state，天然稳定）
 const NO_OPTIONS: DiffOptions = {}
+const CHAR_ON: DiffOptions = { charMode: true }
+const CHAR_OFF: DiffOptions = { charMode: false }
 
 beforeEach(() => {
   vi.useFakeTimers()
@@ -71,6 +73,60 @@ describe('useDiff - 快路径', () => {
   })
 })
 
+describe('useDiff - 字符级大字符量重路径', () => {
+  it('少行大字符量输入（charMode 开启）进入重路径后台计算', () => {
+    const factory = makeFactory()
+    // 2 行 × 约 3 万字符 ≈ 6 万字符：行数远低于快路径阈值，但字符量超过 CHAR_HEAVY_INPUT_CHARS
+    const big = 'a'.repeat(30000) + '\n' + 'b'.repeat(30000)
+    const { result } = renderHook(() => useDiff(big, big, CHAR_ON, factory))
+    expect(result.current.computing).toBe(true)
+    expect(result.current.diff).toBeNull()
+    // 去抖期内尚未创建 worker
+    expect(factory.workers).toHaveLength(0)
+    act(() => {
+      vi.advanceTimersByTime(250)
+    })
+    expect(factory.workers).toHaveLength(1)
+    const w = factory.workers[0]
+    const res = computeDiff(big, big, CHAR_ON)
+    act(() => {
+      w.respond(w.posted[0].jobId, res)
+    })
+    expect(result.current.diff).toEqual(res)
+    expect(result.current.computing).toBe(false)
+  })
+
+  it('charMode 开启但字符量未超阈值仍走快路径', () => {
+    const factory = vi.fn(makeFactory())
+    const { result } = renderHook(() => useDiff('ab\ncd', 'ab\ncd', CHAR_ON, factory))
+    expect(result.current.computing).toBe(false)
+    expect(result.current.diff).not.toBeNull()
+    expect(result.current.diff!.summary.changedLines).toBe(0)
+    expect(factory).not.toHaveBeenCalled()
+  })
+
+  it('charMode 关闭时大字符量输入不触发重路径（行数维度判定不变）', () => {
+    const factory = vi.fn(makeFactory())
+    const big = 'a'.repeat(60000)
+    const { result } = renderHook(() => useDiff(big, big, CHAR_OFF, factory))
+    expect(result.current.computing).toBe(false)
+    expect(result.current.diff).not.toBeNull()
+    expect(factory).not.toHaveBeenCalled()
+  })
+
+  it('恰好阈值不触发重路径，超过阈值触发', () => {
+    const factory = makeFactory()
+    // 两侧各 25000 字符 = 恰好 50000（CHAR_HEAVY_INPUT_CHARS）：不触发
+    const at = 'a'.repeat(25000)
+    const hook1 = renderHook(() => useDiff(at, at, CHAR_ON, factory))
+    expect(hook1.result.current.computing).toBe(false)
+    // 25001 + 25000 = 50001：触发
+    const over = 'a'.repeat(25001)
+    const hook2 = renderHook(() => useDiff(over, at, CHAR_ON, factory))
+    expect(hook2.result.current.computing).toBe(true)
+  })
+})
+
 describe('useDiff - worker 后台计算', () => {
   it('重输入先进入 computing，去抖到期才创建 worker 并派发，回传后更新', () => {
     const factory = makeFactory()
diff --git a/src/renderer/src/hooks/useDiff.ts b/src/renderer/src/hooks/useDiff.ts
index 90e6b83..bb365c0 100644
--- a/src/renderer/src/hooks/useDiff.ts
+++ b/src/renderer/src/hooks/useDiff.ts
@@ -1,5 +1,10 @@
 import { useEffect, useMemo, useRef, useState } from 'react'
-import { computeDiff, type DiffOptions, type DiffResult } from '../diff/diffEngine'
+import {
+  computeDiff,
+  CHAR_HEAVY_INPUT_CHARS,
+  type DiffOptions,
+  type DiffResult
+} from '../diff/diffEngine'
 import { createDiffWorker, type DiffWorkerFactory } from '../diff/createDiffWorker'
 import type { DiffWorkerResponse } from '../diff/diffWorker'
 import { countLines } from '../diff/textUtils'
@@ -31,8 +36,12 @@ export function useDiff(
   workerFactory?: DiffWorkerFactory
 ): DiffState {
   const heavy = useMemo(
-    () => countLines(left) + countLines(right) > FAST_PATH_MAX_LINES,
-    [left, right]
+    () =>
+      countLines(left) + countLines(right) > FAST_PATH_MAX_LINES ||
+      // 字符级对比的耗时由字符量×编辑距离决定：少行大字符量输入（压缩 JSON / base64 单行）
+      // 行数维度防不住，需按字符量兜底走 worker 后台计算
+      (options.charMode === true && left.length + right.length > CHAR_HEAVY_INPUT_CHARS),
+    [left, right, options]
   )
   const factory = workerFactory ?? createDiffWorker
 
diff --git a/src/renderer/src/styles/global.css b/src/renderer/src/styles/global.css
index d0effd3..f50aefe 100644
--- a/src/renderer/src/styles/global.css
+++ b/src/renderer/src/styles/global.css
@@ -599,12 +599,21 @@ button:disabled {
   bottom: calc(100% + 6px);
 }
 
-.toast {
+/* ============ toast 队列（最多 3 条堆叠，各自独立计时） ============ */
+.toast-wrap {
   position: fixed;
   left: 50%;
   bottom: 46px;
   transform: translateX(-50%);
   z-index: 1100;
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  gap: 8px;
+  max-width: 72vw;
+  pointer-events: none;
+}
+.toast {
   max-width: 72vw;
   padding: 9px 16px;
   border-radius: 10px;
@@ -616,16 +625,17 @@ button:disabled {
   overflow: hidden;
   text-overflow: ellipsis;
   white-space: nowrap;
+  pointer-events: auto;
   animation: toast-in 0.2s ease;
 }
 @keyframes toast-in {
   from {
     opacity: 0;
-    transform: translate(-50%, 8px);
+    transform: translateY(8px);
   }
   to {
     opacity: 1;
-    transform: translate(-50%, 0);
+    transform: translateY(0);
   }
 }