diff --git a/src/main/index.ts b/src/main/index.ts
index 93959f2..d5e22ad 100644
--- a/src/main/index.ts
+++ b/src/main/index.ts
@@ -1,14 +1,44 @@
-import { join } from 'path'
-import { app, shell, BrowserWindow, Menu, ipcMain, dialog, clipboard, nativeTheme } from 'electron'
+import { join, dirname } from 'path'
+import { app, shell, BrowserWindow, Menu, ipcMain, dialog, clipboard, nativeTheme, screen } from 'electron'
 import { electronApp, optimizer, is } from '@electron-toolkit/utils'
 import iconv from 'iconv-lite'
 import fs from 'fs'
+import { parseState, clampBounds, type AppState } from './windowState'
+
+/** 应用状态持久化文件（窗口 bounds + 上次文件目录），位于 userData 目录 */
+const stateFile = (): string => join(app.getPath('userData'), 'window-state.json')
+
+/** 当前生效的应用状态（启动时从磁盘读取，运行中增量更新） */
+let appState: AppState = {}
+
+/** 读取持久化状态：文件不存在/损坏一律回退空状态，不影响启动 */
+function loadState(): AppState {
+  try {
+    return parseState(fs.readFileSync(stateFile(), 'utf-8'))
+  } catch {
+    return {}
+  }
+}
+
+/** 写回持久化状态：失败静默忽略（目录只读/磁盘满等，偏好记忆失效但不影响本次会话） */
+function saveState(): void {
+  try {
+    fs.writeFileSync(stateFile(), JSON.stringify(appState), 'utf-8')
+  } catch {
+    // 忽略写入失败
+  }
+}
 
 function createWindow(): void {
+  // 恢复上次窗口尺寸/位置：越界 bounds 钳制回当前屏幕工作区，无记录时用默认尺寸
+  const wa = screen.getPrimaryDisplay().workArea
+  const bounds = appState.bounds ? clampBounds(appState.bounds, wa) : null
   // 主窗口
   const mainWindow = new BrowserWindow({
-    width: 1280,
-    height: 820,
+    width: bounds?.width ?? 1280,
+    height: bounds?.height ?? 820,
+    x: bounds?.x,
+    y: bounds?.y,
     minWidth: 900,
     minHeight: 600,
     show: false,
@@ -24,6 +54,14 @@ function createWindow(): void {
     }
   })
 
+  // 关闭时记忆窗口普通状态 bounds（最大化/全屏/最小化时不记录，避免把超屏尺寸存进偏好）
+  mainWindow.on('close', () => {
+    if (mainWindow.isMinimized() || mainWindow.isMaximized() || mainWindow.isFullScreen()) return
+    const b = mainWindow.getBounds()
+    appState.bounds = { x: b.x, y: b.y, width: b.width, height: b.height }
+    saveState()
+  })
+
   mainWindow.on('ready-to-show', () => {
     mainWindow.show()
   })
@@ -98,6 +136,8 @@ function decodeText(buf: Buffer): { text: string; encoding: string; binary: bool
 ipcMain.handle('file:open', async (_event, side: 'left' | 'right' | null) => {
   const result = await dialog.showOpenDialog({
     title: `选择${side === 'left' ? '左侧' : side === 'right' ? '右侧' : ''}文本文件`,
+    // 记忆上次成功打开文件所在目录；无记录时传 undefined 走系统默认（最近使用位置）
+    defaultPath: appState.lastDir,
     properties: ['openFile'],
     filters: [
       // 与渲染进程 TEXT_EXTENSIONS（src/renderer/src/diff/textUtils.ts）完全对齐；两进程无法共享模块，改动需双向同步
@@ -108,6 +148,9 @@ ipcMain.handle('file:open', async (_event, side: 'left' | 'right' | null) => {
   })
   if (result.canceled || result.filePaths.length === 0) return null
   const filePath = result.filePaths[0]
+  // 记录所在目录供下次对话框起始定位（与窗口 bounds 同存一个状态文件）
+  appState.lastDir = dirname(filePath)
+  saveState()
   const name = filePath.split(/[\\/]/).pop() ?? filePath
   let buf: Buffer
   try {
@@ -163,6 +206,9 @@ app.whenReady().then(() => {
   // 强制暗色系统主题：Windows 标题栏/滚动条等系统控件跟随应用暗色科幻风格
   nativeTheme.themeSource = 'dark'
 
+  // 读取持久化应用状态（窗口 bounds + 上次文件目录；损坏数据回退空状态）
+  appState = loadState()
+
   app.on('browser-window-created', (_, window) => {
     optimizer.watchWindowShortcuts(window)
   })
diff --git a/src/main/windowState.test.ts b/src/main/windowState.test.ts
new file mode 100644
index 0000000..689fcdf
--- /dev/null
+++ b/src/main/windowState.test.ts
@@ -0,0 +1,99 @@
+import { describe, it, expect } from 'vitest'
+import { parseState, clampBounds, MIN_WIDTH, MIN_HEIGHT, type Rect } from './windowState'
+
+/** 1920×1040 工作区（常见全高清屏去掉任务栏） */
+const work: Rect = { x: 0, y: 0, width: 1920, height: 1040 }
+
+describe('parseState', () => {
+  it('空输入回退空状态', () => {
+    expect(parseState(null)).toEqual({})
+    expect(parseState(undefined)).toEqual({})
+    expect(parseState('')).toEqual({})
+  })
+
+  it('非法 JSON 回退空状态', () => {
+    expect(parseState('{broken json!!')).toEqual({})
+  })
+
+  it('合法 bounds 与 lastDir 被保留', () => {
+    const s = parseState(
+      JSON.stringify({ bounds: { x: 10, y: 20, width: 1000, height: 700 }, lastDir: 'C:/docs' })
+    )
+    expect(s.bounds).toEqual({ x: 10, y: 20, width: 1000, height: 700 })
+    expect(s.lastDir).toBe('C:/docs')
+  })
+
+  it('bounds 字段类型异常或缺失时被忽略', () => {
+    expect(parseState(JSON.stringify({ bounds: { x: 'a', y: 2, width: 1000, height: 700 } })).bounds).toBeUndefined()
+    expect(parseState(JSON.stringify({ bounds: { x: 1, y: 2, width: 1000 } })).bounds).toBeUndefined()
+    expect(parseState(JSON.stringify({ bounds: null })).bounds).toBeUndefined()
+  })
+
+  it('bounds 含 NaN/Infinity 等非有限数值时被忽略', () => {
+    const s = parseState(
+      '{"bounds":{"x":NaN,"y":2,"width":1000,"height":700}}'
+    )
+    expect(s.bounds).toBeUndefined()
+  })
+
+  it('lastDir 非字符串或空串时被忽略', () => {
+    expect(parseState(JSON.stringify({ lastDir: 42 })).lastDir).toBeUndefined()
+    expect(parseState(JSON.stringify({ lastDir: '' })).lastDir).toBeUndefined()
+  })
+})
+
+describe('clampBounds', () => {
+  it('工作区内合法 bounds 原样保留', () => {
+    const b = { x: 100, y: 50, width: 1280, height: 820 }
+    expect(clampBounds(b, work)).toEqual(b)
+  })
+
+  it('小于最小尺寸时钳制到最小值', () => {
+    const c = clampBounds({ x: 100, y: 100, width: 400, height: 300 }, work)
+    expect(c.width).toBe(MIN_WIDTH)
+    expect(c.height).toBe(MIN_HEIGHT)
+  })
+
+  it('超出工作区尺寸时封顶到工作区大小', () => {
+    const c = clampBounds({ x: 0, y: 0, width: 4000, height: 3000 }, work)
+    expect(c.width).toBe(work.width)
+    expect(c.height).toBe(work.height)
+  })
+
+  it('窗口移出屏幕左侧时拉回（右边缘至少 60px 进入工作区）', () => {
+    const c = clampBounds({ x: -2000, y: 100, width: 1000, height: 700 }, work)
+    expect(c.x).toBe(work.x - 1000 + 60)
+  })
+
+  it('窗口移出屏幕右侧时拉回（左边缘至少 60px 进入工作区）', () => {
+    const c = clampBounds({ x: 5000, y: 100, width: 1000, height: 700 }, work)
+    expect(c.x).toBe(work.x + work.width - 60)
+  })
+
+  it('窗口移出屏幕下方时拉回', () => {
+    const c = clampBounds({ x: 100, y: 5000, width: 1000, height: 700 }, work)
+    expect(c.y).toBe(work.y + work.height - 60)
+  })
+
+  it('带偏移的工作区（多显示器副屏）同样钳制', () => {
+    const side: Rect = { x: 1920, y: 200, width: 1080, height: 900 }
+    const c = clampBounds({ x: 0, y: 0, width: 1000, height: 700 }, side)
+    // 左边缘至少 60px 进入副屏
+    expect(c.x).toBe(side.x - 1000 + 60)
+  })
+
+  it('非整数尺寸与坐标被取整', () => {
+    const c = clampBounds({ x: 10.6, y: 20.2, width: 1000.7, height: 700.1 }, work)
+    expect(Number.isInteger(c.x)).toBe(true)
+    expect(Number.isInteger(c.y)).toBe(true)
+    expect(Number.isInteger(c.width)).toBe(true)
+    expect(Number.isInteger(c.height)).toBe(true)
+  })
+
+  it('工作区小于最小尺寸时尺寸仍保持最小值', () => {
+    const tiny: Rect = { x: 0, y: 0, width: 800, height: 500 }
+    const c = clampBounds({ x: 0, y: 0, width: 1000, height: 700 }, tiny)
+    expect(c.width).toBe(MIN_WIDTH)
+    expect(c.height).toBe(MIN_HEIGHT)
+  })
+})
diff --git a/src/main/windowState.ts b/src/main/windowState.ts
new file mode 100644
index 0000000..7d3e287
--- /dev/null
+++ b/src/main/windowState.ts
@@ -0,0 +1,70 @@
+/**
+ * 应用状态持久化的纯数据模块：窗口尺寸/位置记忆 + 文件对话框上次目录记忆。
+ * 不依赖 electron 与 fs（磁盘读写由主进程调用方完成），校验逻辑可被 vitest 直接测试。
+ */
+
+/** 矩形区域（窗口 bounds 与屏幕工作区共用结构，字段与 Electron Rectangle 一致） */
+export interface Rect {
+  x: number
+  y: number
+  width: number
+  height: number
+}
+
+/** 持久化的应用状态 */
+export interface AppState {
+  /** 上次关闭时的窗口 bounds */
+  bounds?: Rect
+  /** 上次成功打开文件所在目录（file:open 对话框 defaultPath） */
+  lastDir?: string
+}
+
+/** 最小窗口尺寸（与 BrowserWindow 的 minWidth/minHeight 保持一致，改动需双向同步） */
+export const MIN_WIDTH = 900
+export const MIN_HEIGHT = 600
+
+function isRect(v: unknown): v is Rect {
+  if (typeof v !== 'object' || v === null) return false
+  const r = v as Record<string, unknown>
+  return (
+    typeof r.x === 'number' &&
+    Number.isFinite(r.x) &&
+    typeof r.y === 'number' &&
+    Number.isFinite(r.y) &&
+    typeof r.width === 'number' &&
+    Number.isFinite(r.width) &&
+    typeof r.height === 'number' &&
+    Number.isFinite(r.height)
+  )
+}
+
+/**
+ * 解析持久化文本为状态对象：JSON 非法 / 字段类型异常一律回退空状态，
+ * 保证损坏数据不影响启动。
+ */
+export function parseState(raw: string | null | undefined): AppState {
+  if (!raw) return {}
+  try {
+    const obj = JSON.parse(raw) as AppState
+    const state: AppState = {}
+    if (isRect(obj.bounds)) state.bounds = obj.bounds
+    if (typeof obj.lastDir === 'string' && obj.lastDir !== '') state.lastDir = obj.lastDir
+    return state
+  } catch {
+    return {}
+  }
+}
+
+/**
+ * 把窗口 bounds 钳制到屏幕工作区：
+ * - 尺寸不小于最小值、不超过工作区大小（工作区小于最小值时以最小值为准）；
+ * - 位置保证窗口至少 60px 落在工作区内（分辨率/显示器变更后不出现“看不见的窗口”）；
+ * - 结果取整（BrowserWindow 接受整数坐标）。
+ */
+export function clampBounds(b: Rect, workArea: Rect): Rect {
+  const width = Math.min(Math.max(b.width, MIN_WIDTH), Math.max(workArea.width, MIN_WIDTH))
+  const height = Math.min(Math.max(b.height, MIN_HEIGHT), Math.max(workArea.height, MIN_HEIGHT))
+  const x = Math.min(Math.max(b.x, workArea.x - width + 60), workArea.x + workArea.width - 60)
+  const y = Math.min(Math.max(b.y, workArea.y - height + 60), workArea.y + workArea.height - 60)
+  return { x: Math.round(x), y: Math.round(y), width: Math.round(width), height: Math.round(height) }
+}
diff --git a/src/renderer/src/App.tsx b/src/renderer/src/App.tsx
index 3a6d517..7ff598f 100644
--- a/src/renderer/src/App.tsx
+++ b/src/renderer/src/App.tsx
@@ -493,6 +493,10 @@ export default function App(): ReactElement {
   const leftMeta = paneL?.meta ?? null
   const rightMeta = paneR?.meta ?? null
 
+  // 状态栏行数（面板内容不变时不重算；切分规则与 diff 引擎一致）
+  const leftLines = useMemo(() => (paneL ? countLines(paneL.text) : 0), [paneL])
+  const rightLines = useMemo(() => (paneR ? countLines(paneR.text) : 0), [paneR])
+
   return (
     <div className="app">
       <header className="app-header">
@@ -580,9 +584,11 @@ export default function App(): ReactElement {
         <div className="status-left">
           <span className="status-item">
             左：<b>{paneL ? paneL.meta.name : '—'}</b>
+            {paneL ? ` · ${leftLines} 行` : ''}
           </span>
           <span className="status-item">
             右：<b>{paneR ? paneR.meta.name : '—'}</b>
+            {paneR ? ` · ${rightLines} 行` : ''}
           </span>
           <span className="status-item">
             变更行：<b>{summary.changedLines}</b>
diff --git a/src/renderer/src/__tests__/App.test.tsx b/src/renderer/src/__tests__/App.test.tsx
index 987ac58..8b461ac 100644
--- a/src/renderer/src/__tests__/App.test.tsx
+++ b/src/renderer/src/__tests__/App.test.tsx
@@ -791,6 +791,50 @@ describe('App - 字符级对比', () => {
   })
 })
 
+describe('App - 状态栏行数', () => {
+  // 文件名在 <b> 子元素内，getByText 只拼直接文本子节点无法跨元素匹配，
+  // 用 container 取 .status-item 的完整 textContent 断言（含换行空白，正则放宽）
+  it('加载文件后状态栏显示对应行数（切分规则与引擎一致）', async () => {
+    const { container } = render(<App />)
+    fireEvent.click(screen.getByText('打开左侧'))
+    await screen.findByText('导出报告')
+    const items = () => Array.from(container.querySelectorAll('.status-item'), (e) => e.textContent ?? '')
+    // mockApi 默认返回 'line1\nline2' = 2 行；右侧未加载无行数
+    expect(items()[0]).toMatch(/左：\s*a\.txt\s*·\s*2 行/)
+    expect(items()[1]).toMatch(/右：\s*—$/)
+  })
+
+  it('两侧均加载时各自显示行数', async () => {
+    window.api = mockApi({
+      openFile: async (side) =>
+        side === 'left'
+          ? { path: '/tmp/a.txt', name: 'a.txt', text: 'a\nb\nc', encoding: 'UTF-8', binary: false }
+          : { path: '/tmp/b.txt', name: 'b.txt', text: 'x\ny', encoding: 'UTF-8', binary: false }
+    })
+    const { container } = render(<App />)
+    fireEvent.click(screen.getByText('打开左侧'))
+    await screen.findByText('导出报告')
+    fireEvent.click(screen.getByText('打开右侧'))
+    await screen.findAllByText('b.txt')
+    const items = () => Array.from(container.querySelectorAll('.status-item'), (e) => e.textContent ?? '')
+    expect(items()[0]).toMatch(/左：\s*a\.txt\s*·\s*3 行/)
+    expect(items()[1]).toMatch(/右：\s*b\.txt\s*·\s*2 行/)
+  })
+
+  it('清空后行数展示随空态消失', async () => {
+    const { container } = render(<App />)
+    fireEvent.click(screen.getByText('打开左侧'))
+    await screen.findByText('导出报告')
+    const items = () => Array.from(container.querySelectorAll('.status-item'), (e) => e.textContent ?? '')
+    expect(items()[0]).toMatch(/左：\s*a\.txt\s*·\s*2 行/)
+    fireEvent.click(screen.getByText('清空'))
+    await screen.findByText(/再次点击/)
+    fireEvent.click(screen.getByText('清空'))
+    await screen.findByText(/选择左侧文件/)
+    expect(items()[0]).not.toMatch(/·\s*2 行/)
+  })
+})
+
 describe('App - 交换左右侧', () => {
   it('交换后左右面板文件互换', async () => {
     window.api = mockApi({
diff --git a/vitest.config.ts b/vitest.config.ts
index 53a7664..fb1a348 100644
--- a/vitest.config.ts
+++ b/vitest.config.ts
@@ -13,18 +13,24 @@ export default defineConfig({
     environment: 'jsdom',
     globals: false,
     setupFiles: ['./src/renderer/src/test/setup.ts'],
-    include: ['src/renderer/src/**/*.{test,spec}.{ts,tsx}'],
+    include: [
+      'src/renderer/src/**/*.{test,spec}.{ts,tsx}',
+      // 主进程纯逻辑模块（无 electron 依赖）的单元测试
+      'src/main/**/*.{test,spec}.{ts,tsx}'
+    ],
     exclude: ['node_modules', 'dist', 'out'],
     coverage: {
       provider: 'v8',
       reporter: ['text', 'text-summary'],
-      include: ['src/renderer/src/**/*.{ts,tsx}'],
+      include: ['src/renderer/src/**/*.{ts,tsx}', 'src/main/**/*.ts'],
       exclude: [
         'src/renderer/src/**/*.{test,spec}.{ts,tsx}',
         'src/renderer/src/test/**',
         'src/renderer/src/env.d.ts',
         // worker 线程入口无法在 jsdom 执行，其调用的 computeDiff 已由 diffEngine 测试覆盖
-        'src/renderer/src/diff/diffWorker.ts'
+        'src/renderer/src/diff/diffWorker.ts',
+        // 主进程入口依赖 electron 运行时，无法在 jsdom 测试（窗口/IPC 逻辑随发布人工自测）
+        'src/main/index.ts'
       ],
       all: true,
       // CI 门禁：四项覆盖率不得低于 80%，否则测试失败