diff --git a/content.js b/content.js
index eb686a1..02f862c 100644
--- a/content.js
+++ b/content.js
@@ -492,6 +492,22 @@
   }
 
   function createWeeklyTracker(pageData, dailyData) {
+    // Defense in depth: si pageData/dailyData vienen del caché de chrome.storage,
+    // los Date pueden seguir siendo string/number aunque rehydrateDates haya pasado.
+    // Normalizar aquí mismo evita TypeError al llamar .toLocaleDateString/Time.
+    const ensureDate = (v) => {
+      if (v == null) return null;
+      if (v instanceof Date) return isNaN(v.getTime()) ? null : v;
+      if (typeof v === 'string' || typeof v === 'number') {
+        const d = new Date(v);
+        return isNaN(d.getTime()) ? null : d;
+      }
+      return null;
+    };
+    pageData.sessionStartTime = ensureDate(pageData.sessionStartTime);
+    pageData.sessionEndTime = ensureDate(pageData.sessionEndTime);
+    dailyData.estimatedEndDate = ensureDate(dailyData.estimatedEndDate);
+
     const container = document.createElement('div');
     container.className = 'claude-usage-tracker-container';
     container.id = 'claude-usage-tracker';