diff --git a/core/listenbrainz_manager.py b/core/listenbrainz_manager.py
index c29e4cc6..09855211 100644
--- a/core/listenbrainz_manager.py
+++ b/core/listenbrainz_manager.py
@@ -326,11 +326,43 @@ class ListenBrainzManager:
         covers_found = sum(1 for t in track_data_list if t.get('album_cover_url'))
         logger.info(f"Fetched {covers_found}/{len(track_data_list)} cover art URLs")
 
+    def _retag_misrouted_lastfm_radio_mirrors(self, cursor):
+        """Re-tag mirrored_playlists rows that should be 'lastfm' but
+        were inserted as 'listenbrainz'.
+
+        Backfill for the Phase 1c.1 bug where the auto-mirror helper
+        hardcoded ``source='listenbrainz'`` regardless of playlist
+        origin. Last.fm Radio playlists carry a consistent
+        "Last.fm Radio: <seed>" title prefix from
+        ``save_lastfm_radio_playlist``, so any mirror row matching
+        that prefix should sit under the Last.fm group instead of
+        the ListenBrainz one. Idempotent — only updates rows that
+        are still misrouted."""
+        try:
+            cursor.execute(
+                """
+                UPDATE mirrored_playlists
+                SET source = 'lastfm'
+                WHERE source = 'listenbrainz'
+                  AND name LIKE 'Last.fm Radio:%'
+                """
+            )
+            if cursor.rowcount:
+                logger.info(
+                    f"Re-tagged {cursor.rowcount} Last.fm Radio mirror rows "
+                    "from source='listenbrainz' to source='lastfm'"
+                )
+        except Exception as exc:
+            logger.debug(f"Last.fm radio mirror retag skipped: {exc}")
+
     def _cleanup_old_playlists(self):
         """Remove old playlists, keeping only the 25 most recent per type"""
         conn = self._get_db_connection()
         cursor = conn.cursor()
 
+        # One-shot backfill for legacy misrouting (see method docstring).
+        self._retag_misrouted_lastfm_radio_mirrors(cursor)
+
         # For each playlist type, keep only the N most recent
         # lastfm_radio keeps fewer since they're auto-regenerated weekly
         playlist_type_limits = {
diff --git a/webui/static/sync-services.js b/webui/static/sync-services.js
index 67f6ded7..a133ef04 100644
--- a/webui/static/sync-services.js
+++ b/webui/static/sync-services.js
@@ -10855,18 +10855,27 @@ function _mirrorListenBrainzAfterDiscovery(playlistMbid) {
             return;
         }
 
+        // Last.fm Radio playlists live in the same listenbrainz_playlists
+        // table but are persisted by ``save_lastfm_radio_playlist`` with
+        // a "Last.fm Radio: <seed>" title prefix and ``playlist_type='lastfm_radio'``.
+        // Route them to ``source='lastfm'`` so the Auto-Sync manager
+        // groups them under the Last.fm Radio section + the cascade-
+        // delete hook targets the right mirror source.
+        const title = state.playlist.name || 'ListenBrainz Playlist';
+        const mirrorSource = title.startsWith('Last.fm Radio:') ? 'lastfm' : 'listenbrainz';
+        const ownerFallback = mirrorSource === 'lastfm' ? 'Last.fm' : 'ListenBrainz';
         mirrorPlaylist(
-            'listenbrainz',
+            mirrorSource,
             playlistMbid,
-            state.playlist.name || 'ListenBrainz Playlist',
+            title,
             tracks,
             {
-                owner: state.playlist.creator || 'ListenBrainz',
+                owner: state.playlist.creator || ownerFallback,
                 description: state.playlist.description || '',
                 image_url: state.playlist.image_url || '',
             }
         );
-        console.log(`🪞 [LB Mirror] Mirrored '${state.playlist.name}' with ${tracks.length} matched tracks`);
+        console.log(`🪞 [${mirrorSource} Mirror] Mirrored '${title}' with ${tracks.length} matched tracks`);
     } catch (err) {
         console.warn('LB mirror-after-discovery failed:', err);
     }