diff --git a/src/render/diffViewer.ts b/src/render/diffViewer.ts
index 29d673f..b3e25f9 100644
--- a/src/render/diffViewer.ts
+++ b/src/render/diffViewer.ts
@@ -30,6 +30,7 @@ export class DiffViewer {
   private tmpFiles: string[] = [];
   /** ★ 原子锁：Diff 正在打开中，禁止清除 session */
   private isOpening = false;
+  private closeListener: vscode.Disposable | null = null;
 
   /** 外部回调：Diff 操作完成后通知（用于刷新 UI） */
   onDiffAction?: () => void;
@@ -51,19 +52,19 @@ export class DiffViewer {
     const afterPath = this.makeTmpFile(`ai-diff-after-${editRecord.id.slice(0, 8)}${ext}`, editRecord.afterContent);
 
     this.isOpening = true;
-    this.activeSession = {
+    this.setSession({
       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`
     );
 
@@ -79,18 +80,18 @@ export class DiffViewer {
     const afterPath = this.makeTmpFile(`ai-diff-after-${fileChange.id.slice(0, 8)}${ext}`, fileChange.latestContent);
 
     this.isOpening = true;
-    this.activeSession = {
+    this.setSession({
       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`
     );
 
@@ -188,11 +189,31 @@ export class DiffViewer {
     if (this.activeSession) {
       try { await vscode.commands.executeCommand('workbench.action.closeActiveEditor'); } catch { /* ok */ }
     }
-    this.activeSession = null;
+    this.clearSession();
   }
 
   // ---- 内部 ----
 
+  private setSession(session: DiffSession): void {
+    this.clearSession();
+    this.activeSession = session;
+    // ★ isOpening 锁保护：只有非 opening 状态下的关闭才清除 session
+    this.closeListener = vscode.window.onDidChangeVisibleTextEditors(() => {
+      if (this.isOpening) return; // ← 打开中，不检测
+      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();
+    });
+  }
+
+  private clearSession(): void {
+    this.activeSession = null;
+    if (this.closeListener) { this.closeListener.dispose(); this.closeListener = null; }
+  }
+
   private makeTmpFile(name: string, content: string): string {
     const dir = path.join(os.tmpdir(), 'ai-diff-preview');
     if (!fs.existsSync(dir)) fs.mkdirSync(dir, { recursive: true });