diff --git a/public/index.html b/public/index.html
index 79377d8..7aa1fb7 100644
--- a/public/index.html
+++ b/public/index.html
@@ -4,6 +4,21 @@
 <meta charset="utf-8">
 <meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no">
 <title>動態相片</title>
+<script>
+// iOS 27 Beta 的 WebKit 會讓 tfjs 打包著色器連結失敗
+// （Failed to link vertex and fragment shaders，辨識引擎無聲掛掉），
+// 改用未打包著色器可正常運作。必須在 MindAR 載入前把 tfjsflags
+// 補進網址，tfjs 是從 query string 讀取這個設定的；
+// 網址已手動帶 tfjsflags 時不覆蓋，方便之後實驗其他參數
+(() => {
+  const isIOS = /iPhone|iPad|iPod/.test(navigator.userAgent) ||
+    (navigator.platform === 'MacIntel' && navigator.maxTouchPoints > 1);
+  if (isIOS && !location.search.includes('tfjsflags')) {
+    const q = location.search ? location.search + '&' : '?';
+    history.replaceState(null, '', q + 'tfjsflags=WEBGL_PACK:false' + location.hash);
+  }
+})();
+</script>
 <script src="/vendor/aframe.min.js"></script>
 <script src="/vendor/mindar-image-aframe.prod.js"></script>
 <style>
@@ -41,6 +56,20 @@
   }
   #dlBtn:active { transform: scale(0.94); }
   a { color: #8fb4ff; }
+  #errBox {
+    position: fixed; top: 0; left: 0; right: 0; z-index: 2000;
+    display: none; padding: 10px 14px;
+    background: rgba(170, 32, 32, .92); color: #fff;
+    font: 12px/1.6 monospace; white-space: pre-wrap; word-break: break-all;
+    max-height: 45%; overflow: auto;
+  }
+  #dbgBox {
+    position: fixed; bottom: 0; left: 0; z-index: 2000;
+    display: none; padding: 8px 12px; max-width: 100%;
+    background: rgba(0, 0, 0, .6); color: #9f9;
+    font: 11px/1.5 monospace; white-space: pre-wrap; word-break: break-all;
+    max-height: 40%; overflow: auto;
+  }
 </style>
 </head>
 <body>
@@ -49,10 +78,12 @@
     <p id="status">載入中…</p>
     <button id="startBtn" hidden>開始掃描</button>
     <p class="hint">按下開始後，將相機對準已登錄的照片，<br>對應的影片就會覆蓋在照片上播放。</p>
-    <p class="hint" style="font-size:11px">v7</p>
+    <p class="hint" style="font-size:11px">v8</p>
   </div>
   <button id="stopBtn" title="停止">✕</button>
   <a id="dlBtn" title="下載影片" download>⬇</a>
+  <div id="errBox"></div>
+  <div id="dbgBox"></div>
 
 <script>
 const overlay = document.getElementById('overlay');
@@ -60,6 +91,47 @@ const statusEl = document.getElementById('status');
 const startBtn = document.getElementById('startBtn');
 const stopBtn = document.getElementById('stopBtn');
 const dlBtn = document.getElementById('dlBtn');
+const errBox = document.getElementById('errBox');
+const dbgBox = document.getElementById('dbgBox');
+
+// 掃描在某些裝置上「沒反應」時，錯誤常常只進 console 看不到。
+// 這裡把所有未攔截的錯誤直接顯示在畫面頂端，行動裝置也能看到
+function showErr(msg) {
+  errBox.style.display = 'block';
+  errBox.textContent += (errBox.textContent ? '\n' : '') + msg;
+}
+window.addEventListener('error', (e) => {
+  showErr('錯誤：' + (e.message || String(e.error || '未知')));
+});
+window.addEventListener('unhandledrejection', (e) => {
+  const r = e.reason;
+  showErr('錯誤：' + ((r && r.message) || String(r)));
+});
+
+// 網址加 ?debug 會在畫面底部顯示掃描過程（相機解析度、targetFound 等）
+const DEBUG = new URLSearchParams(location.search).has('debug');
+function dbg(msg) {
+  if (!DEBUG) return;
+  dbgBox.style.display = 'block';
+  const t = (performance.now() / 1000).toFixed(1);
+  dbgBox.textContent += `[${t}s] ${msg}\n`;
+  dbgBox.scrollTop = dbgBox.scrollHeight;
+}
+
+// debug 模式下把 console 訊息也收進畫面：
+// tfjs 著色器編譯失敗的詳細原因只會 console.log，行動裝置上否則看不到
+if (DEBUG) {
+  for (const level of ['log', 'warn', 'error']) {
+    const orig = console[level].bind(console);
+    console[level] = (...args) => {
+      orig(...args);
+      try {
+        const text = args.map((a) => typeof a === 'string' ? a : JSON.stringify(a)).join(' ');
+        if (text && !text.startsWith('%c')) dbg(`console.${level}: ${text.slice(0, 400)}`);
+      } catch {}
+    };
+  }
+}
 
 let sceneEl = null;
 const videos = [];
@@ -92,6 +164,7 @@ async function init() {
     return;
   }
 
+  dbg(`state 載入完成：${entries.length} 個目標，編譯於 ${new Date(state.targets.compiledAt).toLocaleString()}`);
   buildScene(state.targets.compiledAt, entries);
   statusEl.textContent = '';
   startBtn.hidden = false;
@@ -153,6 +226,7 @@ function buildScene(version, entries) {
       }
     });
     anchor.addEventListener('targetFound', () => {
+      dbg(`targetFound：#${t.index}（${t.pair.name}）`);
       isFound = true;
       video.muted = false; // 掃到照片這一刻才解除靜音
       video.defaultMuted = false;
@@ -167,6 +241,7 @@ function buildScene(version, entries) {
       dlBtn.style.display = 'flex';
     });
     anchor.addEventListener('targetLost', () => {
+      dbg(`targetLost：#${t.index}`);
       isFound = false;
       video.pause();
     });
@@ -204,6 +279,12 @@ startBtn.addEventListener('click', async () => {
       if (!v.paused) v.pause();
       v.currentTime = 0;
     }
+    // MindAR 的相機 video 是掛在 body 下、沒有 id 的那個元素
+    const cam = document.querySelector('body > video');
+    dbg('arReady：辨識引擎啟動' + (cam ? `，相機 ${cam.videoWidth}x${cam.videoHeight}` : ''));
+  }, { once: true });
+  sceneEl.addEventListener('arError', () => {
+    showErr('AR 啟動失敗（arError）：通常是相機無法開啟或 WebGL 資源不足');
   }, { once: true });
 
   const start = () => {
