diff --git a/index.html b/index.html
index 8636778..f097d77 100644
--- a/index.html
+++ b/index.html
@@ -231,6 +231,14 @@
             return getSongDurationSeconds(song);
         };
 
+        // --- ID Normalization ---
+        const normalizeSongId = (song) => {
+            if (!song || song.id === undefined || song.id === null) return song;
+            const id = String(song.id);
+            return song.id === id ? song : { ...song, id };
+        };
+
+        const normalizeSongList = (songs) => Array.isArray(songs) ? songs.map(normalizeSongId) : [];
 
         // --- API Services ---
         const api = {
@@ -238,8 +246,11 @@
                 try {
                     const res = await fetch(`${API_BASE}/api/?type=search&keyword=${encodeURIComponent(keyword)}&source=${source}&page=${page}`);
                     const data = await res.json();
-                    // Return full data object to get total and results
-                    return data.code === 200 ? data.data : { results: [], total: 0 };
+                    if (data.code === 200) {
+                        const payload = data.data || {};
+                        return { ...payload, results: normalizeSongList(payload.results) };
+                    }
+                    return { results: [], total: 0 };
                 } catch (e) {
                     console.error("Search failed", e);
                     return { results: [], total: 0 };
@@ -306,7 +317,8 @@
                     const res = await fetch(`${API_BASE}/api/?source=${source}&id=${id}&type=toplist`);
                     const data = await res.json();
                     if (data.code === 200) {
-                        return Array.isArray(data.data) ? data.data : (data.data.list || data.data.tracks || []);
+                        const list = Array.isArray(data.data) ? data.data : (data.data.list || data.data.tracks || []);
+                        return normalizeSongList(list);
                     }
                     return [];
                 } catch (e) {
@@ -319,7 +331,7 @@
                     const res = await fetch(`${API_BASE}/api/?type=playlist&id=${id}&source=${source}`);
                     const data = await res.json();
                     if (data.code === 200 && data.data && Array.isArray(data.data.list)) {
-                        return data.data.list;
+                        return normalizeSongList(data.data.list);
                     }
                     return [];
                 } catch (e) {
@@ -906,18 +918,21 @@
             const observerTarget = useRef(null);
 
             // Player State
-            const [playlist, setPlaylist] = useState(() => JSON.parse(localStorage.getItem('th_playlist')) || []);
-            const [currentSong, setCurrentSong] = useState(() => JSON.parse(localStorage.getItem('th_current')) || null);
+            const [playlist, setPlaylist] = useState(() => normalizeSongList(JSON.parse(localStorage.getItem('th_playlist')) || []));
+            const [currentSong, setCurrentSong] = useState(() => {
+                const cached = JSON.parse(localStorage.getItem('th_current'));
+                return cached ? normalizeSongId(cached) : null;
+            });
             const [isPlaying, setIsPlaying] = useState(false);
             const [duration, setDuration] = useState(0);
             const [currentTime, setCurrentTime] = useState(0);
             const [lyrics, setLyrics] = useState([]);
             const [mode, setMode] = useState('loop'); // loop, one, shuffle
             const [volume, setVolume] = useState(1);
-            const [favorites, setFavorites] = useState(() => JSON.parse(localStorage.getItem('th_favorites')) || []);
+            const [favorites, setFavorites] = useState(() => normalizeSongList(JSON.parse(localStorage.getItem('th_favorites')) || []));
             // Add lastSyncedFavorites to track the state of favorites at the last successful sync
             // This allows us to determine what the user actually changed (added or removed)
-            const [lastSyncedFavorites, setLastSyncedFavorites] = useState(() => JSON.parse(localStorage.getItem('th_favorites_synced')) || []);
+            const [lastSyncedFavorites, setLastSyncedFavorites] = useState(() => normalizeSongList(JSON.parse(localStorage.getItem('th_favorites_synced')) || []));
             const [quality, setQuality] = useState(() => localStorage.getItem('th_quality') || '320k');
             const [syncToken, setSyncToken] = useState(() => localStorage.getItem('th_sync_token') || '');
             const [lastSuccessToken, setLastSuccessToken] = useState(() => localStorage.getItem('th_last_success_token') || '');
@@ -1011,7 +1026,7 @@
                 if (!syncToken || syncToken !== lastSuccessToken) return;
                 try {
                     // Get latest remote state
-                    const remoteFavorites = await syncService.get('favorites', syncToken) || [];
+                    const remoteFavorites = normalizeSongList(await syncService.get('favorites', syncToken) || []);
                     
                     // Calculate Diff: What did the user do locally since last sync?
                     // Added: In Local but not in LastSynced
@@ -1060,26 +1075,26 @@
                 if (isSwitchingToken) {
                     // Mode: Switch Account/Token -> Remote Overwrites Local
                     try {
-                        const cloudFavorites = await syncService.get('favorites', syncToken);
-                        
+                        const cloudFavorites = normalizeSongList(await syncService.get('favorites', syncToken) || []);
+
                         // If cloud has data, use it. If null/empty, we assume new empty account.
-                        const newFavorites = Array.isArray(cloudFavorites) ? cloudFavorites : [];
-                        
+                        const newFavorites = cloudFavorites;
+
                         setFavorites(newFavorites);
                         setLastSyncedFavorites(newFavorites);
                         setLastSuccessToken(syncToken);
-                        
+
                     } catch (e) {
                         console.error("Token switch sync failed", e);
                         throw e; // Let UI show error
                     }
                 } else {
                     // Mode: Regular Sync -> Merge / Union
-                    
+
                     // Pull Remote
-                    const cloudFavorites = await syncService.get('favorites', syncToken);
-                    
-                    if (cloudFavorites && Array.isArray(cloudFavorites)) {
+                    const cloudFavorites = normalizeSongList(await syncService.get('favorites', syncToken) || []);
+
+                    if (cloudFavorites.length > 0) {
                         // Merge: Union
                         const merged = [...favorites];
                         cloudFavorites.forEach(cloudSong => {
@@ -1400,11 +1415,13 @@
             };
 
             const toggleLike = (song) => {
-                const exists = favorites.find(s => s.id === song.id);
+                const normalized = normalizeSongId(song);
+                if (!normalized) return;
+                const exists = favorites.find(s => s.id === normalized.id);
                 if (exists) {
-                    setFavorites(favorites.filter(s => s.id !== song.id));
+                    setFavorites(favorites.filter(s => s.id !== normalized.id));
                 } else {
-                    setFavorites([song, ...favorites]);
+                    setFavorites([normalized, ...favorites]);
                 }
             };