diff --git a/main.js b/main.js
index 52dce35..be421d0 100644
--- a/main.js
+++ b/main.js
@@ -84,9 +84,9 @@ function stopWatching() {
   }
 }
 
-async function showOpenDialog(multi) {
+async function showOpenDialog() {
   const result = await dialog.showOpenDialog(mainWindow, {
-    properties: multi ? ['openFile', 'multiSelections'] : ['openFile'],
+    properties: ['openFile'],
     filters: [
       { name: 'Markdown 文件', extensions: ['md', 'markdown', 'txt'] },
       { name: '所有文件', extensions: ['*'] }
@@ -131,7 +131,7 @@ function switchActiveFile(filePath) {
 // Open single file via dialog
 ipcMain.handle('dialog:openFile', async () => {
   try {
-    const files = await showOpenDialog(false);
+    const files = await showOpenDialog();
     if (files && files.length > 0) {
       const content = readFileContent(files[0]);
       activeFilePath = files[0];
@@ -145,27 +145,6 @@ ipcMain.handle('dialog:openFile', async () => {
   }
 });
 
-// Open multiple files via dialog
-ipcMain.handle('dialog:openFiles', async () => {
-  try {
-    const files = await showOpenDialog(true);
-    if (files && files.length > 0) {
-      const results = [];
-      for (const fp of files) {
-        try {
-          const content = readFileContent(fp);
-          results.push({ filePath: fp, content });
-        } catch (err) {
-          results.push({ filePath: fp, error: err.message });
-        }
-      }
-      return results;
-    }
-    return null;
-  } catch (err) {
-    return { error: err.message };
-  }
-});
 
 ipcMain.handle('file:read', async (event, filePath) => {
   try {
diff --git a/preload.js b/preload.js
index f16d805..8258c3a 100644
--- a/preload.js
+++ b/preload.js
@@ -3,7 +3,6 @@ const { contextBridge, ipcRenderer } = require('electron');
 contextBridge.exposeInMainWorld('electronAPI', {
   // File operations
   openFile: () => ipcRenderer.invoke('dialog:openFile'),
-  openFiles: () => ipcRenderer.invoke('dialog:openFiles'),
   readFile: (filePath) => ipcRenderer.invoke('file:read', filePath),
   saveFile: (data) => ipcRenderer.invoke('file:save', data),
   saveFileAs: (data) => ipcRenderer.invoke('file:saveAs', data),
diff --git a/renderer/renderer.js b/renderer/renderer.js
index 26739a8..8b59295 100644
--- a/renderer/renderer.js
+++ b/renderer/renderer.js
@@ -297,7 +297,9 @@
     const tab = getActiveTab();
     if (tab) {
       tab.isModified = modified;
-      renderTabBar();
+      // Toggle class directly instead of rebuilding entire tab bar
+      const tabEl = tabList.querySelector(`.tab-item[data-tab-id="${tab.id}"]`);
+      if (tabEl) tabEl.classList.toggle('modified', modified);
     }
     updateTitle();
   }
@@ -672,8 +674,7 @@
       if (tab) {
         tab.isModified = true;
         tab.content = editor.value;
-        renderTabBar();
-        updateTitle();
+        setModified(true);
       }
       scheduleUpdate();
     });