Warm the stream cache for likely next plays

server/server.js

@@ -547,6 +547,21 @@ function pickFormat(formats, { formatId, wantAudio, wantHeight }) {
   return null;
 }
 
+// GET /api/streams/warm?v=<id> — fire-and-forget: resolve streams into
+// streamCache so the real /api/streams a moment later is instant. Bounded
+// so a scrolling user can't queue dozens of yt-dlp processes.
+const WARM_MAX = 2;
+let warmActive = 0;
+app.get('/api/streams/warm', async (c) => {
+  const id = (c.req.query('v') || '').trim();
+  if (!/^[A-Za-z0-9_-]{11}$/.test(id)) return c.body(null, 204);
+  if (warmActive >= WARM_MAX) return c.body(null, 204);
+  try { if (await media.getReady(id)) return c.body(null, 204); } catch { /* fall through */ }
+  warmActive++;
+  resolveStreams(id).catch(() => {}).finally(() => { warmActive--; });
+  return c.body(null, 204);
+});
+
 // GET /api/streams?v=<videoId> — meta + proxied audio/quality URLs.
 app.get('/api/streams', async (c) => {
   const videoId = (c.req.query('v') || '').replace(/[/\\:?<>|*"]/g, '').trim();