web/src/lib/components/PlaylistCard.svelte

@@ -86,10 +86,17 @@
         const detail = await getPlaylist(playlist.id);
         const refs = toTrackRefs(detail.tracks);
         if (refs.length > 0) {
-          // Tag the queue with the variant when one exists so play
+          // Per-artist system mixes (songs_like_artist) carry a
-          // events still carry the correct source attribution even
+          // variant tag so play_started still attributes the source
-          // though we went through the per-id path.
+          // correctly even though we routed through the per-id path.
-          playQueue(refs, 0, variant != null ? { source: variant } : undefined);
+          // True user playlists (variant == null) call with two args
+          // so source attribution stays absent — the PlaylistCard
+          // test pins this contract.
+          if (variant != null) {
+            playQueue(refs, 0, { source: variant });
+          } else {
+            playQueue(refs, 0);
+          }
         }
       }
     } finally {