diff --git a/apps/desktop/src/renderer/App.tsx b/apps/desktop/src/renderer/App.tsx
index 429c950..b6eae5c 100644
--- a/apps/desktop/src/renderer/App.tsx
+++ b/apps/desktop/src/renderer/App.tsx
@@ -49,7 +49,7 @@ export function App() {
   }).catch(() => {}); } }, [activeId]);
   // FR-S4：关窗前冲刷未保存内容
   useEffect(() => {
-    const onBeforeUnload = () => { try { useStore.getState().saveNow(); } catch {} };
+    const onBeforeUnload = () => { try { window.dispatchEvent(new CustomEvent('dsh-flush-body')); useStore.getState().saveNow(); } catch {} };
     window.addEventListener('beforeunload', onBeforeUnload);
     return () => window.removeEventListener('beforeunload', onBeforeUnload);
   }, []);
@@ -62,7 +62,7 @@ export function App() {
       await useStore.getState().loadTree();
       await useStore.getState().openDoc(path);
     },
-    onSave: () => useStore.getState().saveNow(),
+    onSave: () => { window.dispatchEvent(new CustomEvent('dsh-flush-body')); useStore.getState().saveNow(); },
     onFocusSearch: () => { const el = document.querySelector('input[placeholder*="搜索"]') as HTMLInputElement; el?.focus(); },
     onToggleOutline: () => layout.toggleOutline(),
     onCheat: () => setShowCheat(true),
diff --git a/apps/desktop/src/renderer/features/editor/TiptapEditor.tsx b/apps/desktop/src/renderer/features/editor/TiptapEditor.tsx
index 7f60c13..bac14a4 100644
--- a/apps/desktop/src/renderer/features/editor/TiptapEditor.tsx
+++ b/apps/desktop/src/renderer/features/editor/TiptapEditor.tsx
@@ -44,6 +44,7 @@ export function TiptapEditor() {
   const setBody = useStore(s => s.setBody);
   const skipUpdate = useRef(false);
   const editorRef = useRef<Editor | null>(null);
+  const mdTimer = useRef<ReturnType<typeof setTimeout> | null>(null);
 
   // editor 实例稳定，不随文档切换重建（避免销毁/重建过渡期 commands 为 null）
   const editor = useEditor({
@@ -92,7 +93,14 @@ export function TiptapEditor() {
         return false;
       },
     },
-    onUpdate: ({ editor }) => { if (!skipUpdate.current) setBody((editor.storage as Record<string, any>).markdown.getMarkdown()); },
+    onUpdate: ({ editor }) => {
+      if (skipUpdate.current) return;
+      // 大文档防抖——getMarkdown() 对 2000+ 行文档开销显著，不必每次按键都序列化
+      if (mdTimer.current) clearTimeout(mdTimer.current);
+      mdTimer.current = setTimeout(() => {
+        setBody((editor.storage as Record<string, any>).markdown.getMarkdown());
+      }, 300);
+    },
   });
 
   // 切换文档时只同步内容，不重建 editor
@@ -111,6 +119,17 @@ export function TiptapEditor() {
     skipUpdate.current = false;
   }, [currentPath, editor]);
 
+  // 监听保存前冲刷——Ctrl+S / 关窗前同步编辑器内容到 store
+  useEffect(() => {
+    if (!editor) return;
+    const onFlush = () => {
+      if (mdTimer.current) { clearTimeout(mdTimer.current); mdTimer.current = null; }
+      setBody((editor.storage as Record<string, any>).markdown.getMarkdown());
+    };
+    window.addEventListener('dsh-flush-body', onFlush);
+    return () => window.removeEventListener('dsh-flush-body', onFlush);
+  }, [editor, setBody]);
+
   if (!currentPath) {
     return (
       <div style={{ flex: 1, display: 'flex', alignItems: 'center', justifyContent: 'center', opacity: 0.4 }}>
diff --git a/apps/desktop/src/renderer/store.ts b/apps/desktop/src/renderer/store.ts
index df0a18f..f51b7ba 100644
--- a/apps/desktop/src/renderer/store.ts
+++ b/apps/desktop/src/renderer/store.ts
@@ -66,8 +66,9 @@ export const useStore = create<EditorState>((set, get) => ({
   },
 
   openDoc: async (path: string) => {
-    // 切换前冲刷当前文档
-    await get().saveNow();
+    // 切换前冲刷当前文档——先同步编辑器内容到 store 再保存
+    window.dispatchEvent(new CustomEvent('dsh-flush-body'));
+    void get().saveNow();
     const doc: ReadDocResult = await invoke(IPC.docRead, { path });
     set({ currentPath: path, body: doc.body, meta: doc.meta, title: doc.meta.title ?? path.split('/').pop()!.replace(/\.md$/, ''), saveState: 'saved', docMtime: doc.mtime });
     // 同步到标签页（如已存在则激活，否则新建）
@@ -103,7 +104,7 @@ export const useStore = create<EditorState>((set, get) => ({
     set({ body, saveState: 'saving' });
     // FR-S1：防抖自动保存——间隔读 settings.autoSaveInterval（秒→毫秒）
     if (saveTimer) clearTimeout(saveTimer);
-    const interval = (() => { try { const s = JSON.parse(localStorage.getItem('dsh-settings') ?? '{}'); return (s.autoSaveInterval ?? 1) * 1000; } catch { return 1000; } })();
+    const interval = (() => { try { const s = JSON.parse(localStorage.getItem('dsh-settings') ?? '{}'); return (s.autoSaveInterval ?? 3) * 1000; } catch { return 3000; } })();
     saveTimer = setTimeout(() => { get().saveNow(); }, interval);
   },
 
diff --git a/apps/desktop/tests/e2e/save-mechanism.spec.ts b/apps/desktop/tests/e2e/save-mechanism.spec.ts
index b913367..01de35f 100644
--- a/apps/desktop/tests/e2e/save-mechanism.spec.ts
+++ b/apps/desktop/tests/e2e/save-mechanism.spec.ts
@@ -62,7 +62,8 @@ test('FR-S4：关窗冲刷未保存内容', async () => {
   await a.page.keyboard.type('before-close-flush');
   // 等一下让内容进入 store
   await a.page.waitForTimeout(200);
-  // 手动触发 saveNow（模拟 beforeunload 冲刷）
+  // 冲刷编辑器内容到 store 再保存（模拟 beforeunload 冲刷）
+  await a.page.evaluate(() => window.dispatchEvent(new CustomEvent('dsh-flush-body')));
   await a.page.evaluate(() => (window as any).__STORE__?.getState?.().saveNow?.());
   await a.page.waitForTimeout(500);
   await a.app.close();
@@ -86,7 +87,10 @@ test('FR-S6：reloadDoc 检测外部改动', async () => {
 
   await a.page.locator('.ProseMirror').click();
   await a.page.keyboard.type('original');
-  await a.page.waitForTimeout(2000); // 等待自动保存
+  await a.page.waitForTimeout(200);
+  await a.page.evaluate(() => window.dispatchEvent(new CustomEvent('dsh-flush-body')));
+  await a.page.evaluate(() => (window as any).__STORE__?.getState?.().saveNow?.());
+  await a.page.waitForTimeout(500); // 等待保存完成
 
   // 外部修改文件
   const filePath = nodePath.join(vault, '重载测试.md');