diff --git a/entry/src/main/ets/pages/BridgeGameContainer.ets b/entry/src/main/ets/pages/BridgeGameContainer.ets
index 87a637d..d59bdbc 100644
--- a/entry/src/main/ets/pages/BridgeGameContainer.ets
+++ b/entry/src/main/ets/pages/BridgeGameContainer.ets
@@ -114,7 +114,13 @@ export struct BridgeGameContainer {
 
   /** 路径 A：大厅 → 子游戏（大厅去激活并保活，创建子游戏 Web）。 */
   private switchGame(p?: EventPayload): void {
-    if (p === undefined || this.subgameUrl !== '') {
+    if (p === undefined) {
+      return;
+    }
+    // 拓扑约束：仅 大厅↔子游戏，无 子游戏→子游戏。已在子游戏中时忽略——
+    // 游戏逻辑须先 backgameData 回大厅、再由大厅发 SwitchOverGameData 进新子游戏。
+    if (this.subgameUrl !== '') {
+      Logger.tag('BridgeGameContainer').w('SwitchOverGameData ignored: already in subgame (route via lobby)');
       return;
     }
     const d = p as SwitchGamePayload;