diff --git a/app/static/index.html b/app/static/index.html
index 1ac0e89..77cfcdb 100644
--- a/app/static/index.html
+++ b/app/static/index.html
@@ -5,7 +5,7 @@
     <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no, viewport-fit=cover">
     <title>Notes — Персональный тренажер и словарь английского языка</title>
     <meta name="description" content="Защищённый персональный тренажёр и словарь английского языка с интервальными повторениями SRS SM-2, контекстным поиском и озвучкой">
-    <link rel="stylesheet" href="/static/css/style.css?v=5.3">
+    <link rel="stylesheet" href="/static/css/style.css?v=5.4">
     
     <!-- PWA meta and icons -->
     <link rel="manifest" href="/manifest.json">
@@ -1383,7 +1383,7 @@
     <!-- Audio Element for native streaming -->
     <audio id="global-audio-player" preload="none"></audio>
 
-    <script type="module" src="/static/js/app.js?v=5.3"></script>
+    <script type="module" src="/static/js/app.js?v=5.4"></script>
 </body>
 </html>
 
diff --git a/app/static/js/modules/cefr.js b/app/static/js/modules/cefr.js
index 7d915fe..00a4837 100644
--- a/app/static/js/modules/cefr.js
+++ b/app/static/js/modules/cefr.js
@@ -352,6 +352,9 @@ async function handleOptionTap(questionId, selectedOption, clickedBtn) {
     if (isAnswered) return;
     isAnswered = true;
 
+    const q = currentQuiz[currentQuestionIdx];
+    const sentence = q ? q.sentence : '';
+
     // Disable all options
     document.querySelectorAll('.cefr-opt-btn').forEach(b => {
         b.disabled = true;
@@ -384,7 +387,7 @@ async function handleOptionTap(questionId, selectedOption, clickedBtn) {
                     ${renderOptionsBreakdown(res.options_breakdown)}
                 `;
                 feedbackBox.classList.remove('hidden');
-                attachBreakdownListeners(feedbackBox, q.sentence);
+                attachBreakdownListeners(feedbackBox, sentence);
             }
         } else {
             sessionStats.mistakes++;
@@ -433,7 +436,7 @@ async function handleOptionTap(questionId, selectedOption, clickedBtn) {
                     ${renderOptionsBreakdown(res.options_breakdown)}
                 `;
                 feedbackBox.classList.remove('hidden');
-                attachBreakdownListeners(feedbackBox, q.sentence);
+                attachBreakdownListeners(feedbackBox, sentence);
             }
         }
 
diff --git a/app/static/sw.js b/app/static/sw.js
index 7adac4f..488a88d 100644
--- a/app/static/sw.js
+++ b/app/static/sw.js
@@ -1,7 +1,7 @@
 // Service Worker for Notes English PWA (Stage 2)
 // Strategy: Cache-first for static assets, Network-first for API calls.
 
-const CACHE_NAME = 'notes-v5.3';
+const CACHE_NAME = 'notes-v5.4';
 const OFFLINE_URL = '/';
 
 const PRECACHE_URLS = [