diff --git a/public/themes/dist_static/static/js/common.js b/public/themes/dist_static/static/js/common.js
index 59fd44b..5c9dd1d 100644
--- a/public/themes/dist_static/static/js/common.js
+++ b/public/themes/dist_static/static/js/common.js
@@ -103,10 +103,12 @@ $(function() {
 		$(this).attr("aria-expanded", String(!isExpanded));
 	});
 
-	// nav-mega 子组：标题 / 箭头均可展开收起
+	// nav-mega 子组：标题 / 箭头均可展开收起（同组互斥）
 	$(document).on("click", ".nav-mega__subgroup-title, .nav-mega__subgroup-toggle", function() {
 		const $subgroup = $(this).closest(".nav-mega__subgroup");
+		const $siblings = $subgroup.siblings(".nav-mega__subgroup");
 		const isExpanded = !$subgroup.hasClass("is-expanded");
+		$siblings.removeClass("is-expanded").find(".nav-mega__subgroup-toggle").attr("aria-expanded", false);
 		$subgroup.toggleClass("is-expanded", isExpanded);
 		$subgroup.find(".nav-mega__subgroup-toggle").attr("aria-expanded", isExpanded);
 	});