diff --git a/src-tauri/src/services/subscription.rs b/src-tauri/src/services/subscription.rs
index 5528455e6..5d6cbf58d 100644
--- a/src-tauri/src/services/subscription.rs
+++ b/src-tauri/src/services/subscription.rs
@@ -1340,3 +1340,21 @@ fn now_millis() -> i64 {
         .unwrap_or_default()
         .as_millis() as i64
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn window_seconds_map_to_expected_tier_names() {
+        // 官方特例窗口
+        assert_eq!(window_seconds_to_tier_name(18000), "five_hour");
+        assert_eq!(window_seconds_to_tier_name(604800), "seven_day");
+        // Codex 免费方案的次要窗口是 30 天（30 * 24 * 3600 = 2_592_000 秒）。
+        // 前端 TIER_I18N_KEYS 需要有对应的 "30_day" 才能展示，见 #3651。
+        assert_eq!(window_seconds_to_tier_name(2_592_000), "30_day");
+        // 其他窗口按小时/天回退命名
+        assert_eq!(window_seconds_to_tier_name(3600), "1_hour");
+        assert_eq!(window_seconds_to_tier_name(86400), "1_day");
+    }
+}
diff --git a/src/components/SubscriptionQuotaFooter.tsx b/src/components/SubscriptionQuotaFooter.tsx
index 7d46bc376..e5ce8ecaf 100644
--- a/src/components/SubscriptionQuotaFooter.tsx
+++ b/src/components/SubscriptionQuotaFooter.tsx
@@ -27,6 +27,8 @@ export const TIER_I18N_KEYS: Record<string, string> = {
   seven_day: "subscription.sevenDay",
   seven_day_opus: "subscription.sevenDayOpus",
   seven_day_sonnet: "subscription.sevenDaySonnet",
+  // Codex 免费方案的次要窗口是 30 天（付费方案为 7 天）
+  "30_day": "subscription.thirtyDay",
   // Gemini 模型分类
   gemini_pro: "subscription.geminiPro",
   gemini_flash: "subscription.geminiFlash",
diff --git a/src/i18n/locales/en.json b/src/i18n/locales/en.json
index fcad23b3f..1bb0c7314 100644
--- a/src/i18n/locales/en.json
+++ b/src/i18n/locales/en.json
@@ -2903,6 +2903,7 @@
     "sevenDay": "7-Day",
     "sevenDayOpus": "7-Day (Opus)",
     "sevenDaySonnet": "7-Day (Sonnet)",
+    "thirtyDay": "30-Day",
     "geminiPro": "Pro",
     "geminiFlash": "Flash",
     "geminiFlashLite": "Flash Lite",
diff --git a/src/i18n/locales/ja.json b/src/i18n/locales/ja.json
index 46c3b51fc..1638fde00 100644
--- a/src/i18n/locales/ja.json
+++ b/src/i18n/locales/ja.json
@@ -2903,6 +2903,7 @@
     "sevenDay": "7日間",
     "sevenDayOpus": "7日間(Opus)",
     "sevenDaySonnet": "7日間(Sonnet)",
+    "thirtyDay": "30日間",
     "geminiPro": "Pro",
     "geminiFlash": "Flash",
     "geminiFlashLite": "Flash Lite",
diff --git a/src/i18n/locales/zh-TW.json b/src/i18n/locales/zh-TW.json
index feaddbbb0..ee07ad703 100644
--- a/src/i18n/locales/zh-TW.json
+++ b/src/i18n/locales/zh-TW.json
@@ -2875,6 +2875,7 @@
     "sevenDay": "7 天",
     "sevenDayOpus": "7 天 (Opus)",
     "sevenDaySonnet": "7 天 (Sonnet)",
+    "thirtyDay": "30 天",
     "geminiPro": "Pro",
     "geminiFlash": "Flash",
     "geminiFlashLite": "Flash Lite",
diff --git a/src/i18n/locales/zh.json b/src/i18n/locales/zh.json
index c58366488..c31ccd930 100644
--- a/src/i18n/locales/zh.json
+++ b/src/i18n/locales/zh.json
@@ -2903,6 +2903,7 @@
     "sevenDay": "7天",
     "sevenDayOpus": "7天(Opus)",
     "sevenDaySonnet": "7天(Sonnet)",
+    "thirtyDay": "30天",
     "geminiPro": "Pro",
     "geminiFlash": "Flash",
     "geminiFlashLite": "Flash Lite",