diff --git a/src/render/diffViewer.ts b/src/render/diffViewer.ts
index 8e07ed8..29d673f 100644
--- a/src/render/diffViewer.ts
+++ b/src/render/diffViewer.ts
@@ -5,7 +5,7 @@
  * 1. 临时文件（非 untitled）避免保存提示
  * 2. ★ 临时文件只在 Accept/Reject 后删除，手动关闭 Diff 不影响
  * 3. Accept/Reject 后自动推进到下一个 pending 文件
- * 4. 状态栏按钮在 Diff 模式下可见
+ * 4. 状态栏按钮在 Diff 模式下可见（isOpening 锁防竞态）
  */
 
 import * as vscode from 'vscode';
@@ -27,8 +27,9 @@ export interface DiffSession {
 
 export class DiffViewer {
   private activeSession: DiffSession | null = null;
-  private closeListener: vscode.Disposable | null = null;
   private tmpFiles: string[] = [];
+  /** ★ 原子锁：Diff 正在打开中，禁止清除 session */
+  private isOpening = false;
 
   /** 外部回调：Diff 操作完成后通知（用于刷新 UI） */
   onDiffAction?: () => void;
@@ -49,23 +50,24 @@ export class DiffViewer {
     const beforePath = this.makeTmpFile(`ai-diff-before-${editRecord.id.slice(0, 8)}${ext}`, editRecord.beforeContent);
     const afterPath = this.makeTmpFile(`ai-diff-after-${editRecord.id.slice(0, 8)}${ext}`, editRecord.afterContent);
 
-    this.setSession({
+    this.isOpening = true;
+    this.activeSession = {
       fileId: fileChangeId,
       editId: editRecord.id,
       beforeTmpPath: beforePath,
       afterTmpPath: afterPath,
       beforeUri: vscode.Uri.file(beforePath),
       afterUri: vscode.Uri.file(afterPath),
-    });
+    };
 
     await vscode.commands.executeCommand(
       'vscode.diff',
-      this.activeSession!.beforeUri,
-      this.activeSession!.afterUri,
+      this.activeSession.beforeUri,
+      this.activeSession.afterUri,
       `${fileName} — AI ${toolLabel} #${editRecord.id.slice(0, 6)} · 状态栏操作`
     );
 
-    // ★ 通知外部刷新状态栏（切换到 Diff 模式显示 Accept/Reject 按钮）
+    this.isOpening = false;
     this.onDiffAction?.();
   }
 
@@ -76,22 +78,23 @@ export class DiffViewer {
     const beforePath = this.makeTmpFile(`ai-diff-before-${fileChange.id.slice(0, 8)}${ext}`, fileChange.originalContent);
     const afterPath = this.makeTmpFile(`ai-diff-after-${fileChange.id.slice(0, 8)}${ext}`, fileChange.latestContent);
 
-    this.setSession({
+    this.isOpening = true;
+    this.activeSession = {
       fileId: fileChange.id,
       beforeTmpPath: beforePath,
       afterTmpPath: afterPath,
       beforeUri: vscode.Uri.file(beforePath),
       afterUri: vscode.Uri.file(afterPath),
-    });
+    };
 
     await vscode.commands.executeCommand(
       'vscode.diff',
-      this.activeSession!.beforeUri,
-      this.activeSession!.afterUri,
+      this.activeSession.beforeUri,
+      this.activeSession.afterUri,
       `${fileName} — ${fileChange.edits.length} 次 AI 编辑 · 状态栏操作`
     );
 
-    // ★ 通知外部刷新状态栏（切换到 Diff 模式显示 Accept/Reject 按钮）
+    this.isOpening = false;
     this.onDiffAction?.();
   }
 
@@ -108,9 +111,7 @@ export class DiffViewer {
     else vscode.window.showInformationMessage('AI Diff: 当前文件无待处理变更');
   }
 
-  // ---- Diff 界面操作 (Bug 1 修复: 自动推进) ----
-
-  // ★ Accept/Reject 后删除临时文件 + 关闭 Diff
+  // ---- Accept/Reject（Accept/Reject 后删除临时文件 + 关闭 Diff） ----
 
   async acceptCurrentDiff(): Promise<void> {
     if (!this.activeSession) return;
@@ -123,7 +124,7 @@ export class DiffViewer {
     }
 
     vscode.window.showInformationMessage('AI Diff: 已接受 ✓');
-    this.deleteSessionFiles();  // ★ Accept 后才删
+    this.deleteSessionFiles();
     await this.closeDiff();
     this.onDiffAction?.();
     this.advanceToNext(fileId);
@@ -140,7 +141,7 @@ export class DiffViewer {
     }
 
     vscode.window.showInformationMessage('AI Diff: 已拒绝 ✗');
-    this.deleteSessionFiles();  // ★ Reject 后才删
+    this.deleteSessionFiles();
     await this.closeDiff();
     this.onDiffAction?.();
     this.advanceToNext(fileId);
@@ -153,16 +154,15 @@ export class DiffViewer {
     if (ok) {
       vscode.window.showInformationMessage('AI Diff: 已接受此文件全部 ✓');
     }
-    this.deleteSessionFiles();  // ★ AcceptAll 后才删
+    this.deleteSessionFiles();
     await this.closeDiff();
     this.onDiffAction?.();
     this.advanceToNext(fileId);
   }
 
-  // ---- ★ Bug 1: 自动推进 ----
+  // ---- 自动推进 ----
 
   private advanceToNext(afterFileId: string): void {
-    // 如果此文件仍有待处理编辑，重新打开此文件
     if (!this.changeSetManager.isFileFullyProcessed(afterFileId)) {
       const set = this.changeSetManager.getCurrentSet();
       const same = set?.changes.find(c => c.id === afterFileId);
@@ -172,7 +172,6 @@ export class DiffViewer {
       }
     }
 
-    // 否则推进到下一个 pending 文件
     const next = this.changeSetManager.findNextPending(afterFileId);
     if (next) {
       setTimeout(() => this.showFileDiff(next), 150);
@@ -189,7 +188,7 @@ export class DiffViewer {
     if (this.activeSession) {
       try { await vscode.commands.executeCommand('workbench.action.closeActiveEditor'); } catch { /* ok */ }
     }
-    this.clearSession();
+    this.activeSession = null;
   }
 
   // ---- 内部 ----
@@ -203,20 +202,6 @@ export class DiffViewer {
     return filePath;
   }
 
-  private setSession(session: DiffSession): void {
-    this.clearSession();
-    this.activeSession = session;
-    this.closeListener = vscode.window.onDidChangeVisibleTextEditors(() => {
-      if (!this.activeSession) return;
-      const stillOpen = vscode.window.visibleTextEditors.some(
-        e => e.document.uri.toString() === this.activeSession!.beforeUri.toString() ||
-             e.document.uri.toString() === this.activeSession!.afterUri.toString()
-      );
-      if (!stillOpen) this.clearSession();
-    });
-  }
-
-  /** ★ 删除当前会话的临时文件（只在 Accept/Reject 时调用） */
   private deleteSessionFiles(): void {
     if (!this.activeSession) return;
     [this.activeSession.beforeTmpPath, this.activeSession.afterTmpPath].forEach(p => {
@@ -227,16 +212,10 @@ export class DiffViewer {
     );
   }
 
-  /** 清除会话状态（不删文件！手动关闭 Diff 后不影响重新打开） */
-  private clearSession(): void {
-    this.activeSession = null;
-    if (this.closeListener) { this.closeListener.dispose(); this.closeListener = null; }
-  }
-
   cleanupTmpFiles(): void {
     for (const p of this.tmpFiles) {
       try { if (fs.existsSync(p)) fs.unlinkSync(p); } catch { /* ok */ }
     }
     this.tmpFiles = [];
   }
-}
+}
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