diff --git a/frontend/src/pages/usr/UserDetailPage.tsx b/frontend/src/pages/usr/UserDetailPage.tsx
index f6b61eb..94a33a3 100644
--- a/frontend/src/pages/usr/UserDetailPage.tsx
+++ b/frontend/src/pages/usr/UserDetailPage.tsx
@@ -176,7 +176,16 @@ export default function UserDetailPage() {
         ))}
       </div>
 
-      {/* Permission list */}
+      {/* Permission list
+          KNOWN LIMITATION (edit mode): UserListItemVO does not include permGroupIds (backend list API
+          does not return them). In edit mode, selectedPermIds starts empty — saving will overwrite
+          existing permissions with whatever the user selects here. A future backend GET /usr/users/:id
+          endpoint should return permGroupIds so they can be pre-populated. */}
+      {!isNew && activePermTab === 0 && (
+        <div style={{ background: '#fffbe6', borderBottom: '1px solid #ffe58f', padding: '8px 14px', fontSize: 12, color: '#ad6800' }}>
+          ⚠ 编辑模式下权限组未预加载（后端列表接口不返回 permGroupIds）。保存将以当前勾选为准，请重新勾选所需权限组。
+        </div>
+      )}
       <div style={{ flex: 1, background: '#fff', overflow: 'auto' }}>
         <div style={{ display: 'flex', alignItems: 'center', gap: 14, padding: '10px 14px', borderBottom: '1px solid var(--color-table-border)', background: 'var(--color-table-header-bg)', fontWeight: 500, color: '#222', fontSize: 13 }}>
           <span style={{ width: 14, height: 14, border: '1px solid #b8bcc3', display: 'inline-block', flexShrink: 0 }} />