SPA遷移の修正

src/injected/page-script.ts

@@ -16,6 +16,7 @@
   w.__yt_playlist_ext_injected = true;
 
   let extractingUrl: string | null = null;
+  let isInitialLoad = true;
   let collabCache: Map<string, string> = new Map();
   let collabCachePlaylistId: string | null = null;
 
@@ -64,12 +65,13 @@
     const { cfg, apiKey, baseContext } = getConfig();
     const authHeaders = buildAuthHeaders(cfg, baseContext);
 
-    // Try ytInitialData first (works on initial page load)
-    let initialData = w.ytInitialData;
+    // Try ytInitialData only on initial page load.
+    // On SPA navigation ytInitialData is stale (still holds the previous page's data),
+    // so we must always fetch fresh data via the browse API.
+    let initialData = isInitialLoad ? w.ytInitialData : null;
     let videoList = initialData ? findVideoListContents(initialData) : null;
+    isInitialLoad = false;
 
-    // If ytInitialData doesn't have the video list (SPA navigation),
-    // fetch the playlist data ourselves via the browse API
     if (!videoList) {
       const playlistId = getPlaylistId();
       if (!playlistId) {