diff --git a/src/AKSRT/Settings/Settings.php b/src/AKSRT/Settings/Settings.php
index 98d446ac..43703d37 100644
--- a/src/AKSRT/Settings/Settings.php
+++ b/src/AKSRT/Settings/Settings.php
@@ -19,7 +19,42 @@ class Settings {
     private static $instance = null;
     use FacadeBulk;
 
+    /**
+     * Per-request memoization of merged settings.
+     *
+     * 同一请求内多次调用 get_all() 仅读 1 次 option。
+     * 后端写入 option 时通过 updated_option hook 失效。
+     *
+     * @var array|null
+     */
+    private static $cached_all = null;
 
+    /**
+     * 所有独立 option key（非 aksrt_settings）。
+     * 用于导入导出完整性检查。
+     */
+    public const STANDALONE_OPTION_KEYS = [
+        'aksrt_mail_smtp',
+        'aksrt_oauth',
+        'aksrt_captcha_config',
+        'aksrt_moderation_config',
+        'aksrt_footer_settings',
+        'aksrt_footer_tabbar',
+        'aksrt_floating_buttons',
+        'aksrt_credit_settings',
+        'aksrt_notification_settings',
+        'aksrt_friend_links',
+        'aksrt_banners',
+        'aksrt_category_recommend',
+    ];
+
+    /**
+     * 包含 secret 字段的 option key — 空值保留旧值策略。
+     */
+    public const SECRET_OPTION_KEYS = [
+        'aksrt_mail_smtp',
+        'aksrt_oauth',
+    ];
 
     private function __construct() {}