fix: write single first-artist tag, not doubled/multi-artist

Live end-to-end test surfaced two bugs in youtube tagging:
- `--replace-in-metadata artist .* NAME` matched twice and doubled the
  artist tag (e.g. "SLVMLORDSLVMLORD"). Anchor with ^.*$ to match once.
- Use only the first artist when several are present (SLVMLORD, not
  "SLVMLORD, Travis Bradley, ...") for both the embedded tag and the
  spoken/echoed API messages.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

musicfetch

@@ -474,7 +474,10 @@ def yt_download(url_or_query: str, target_folder: str, quality: str, dry_run: bo
     # Override tags from the chosen hit so they don't rely on scraped titles.
     if hit:
         if hit.artist:
-            cmd += ["--replace-in-metadata", "artist", ".*", hit.artist]
+            # First artist only; anchored ^.*$ replaces the whole field exactly once
+            # (a bare .* matches twice and doubles the value).
+            primary_artist = hit.artist.split(",")[0].strip()
+            cmd += ["--replace-in-metadata", "artist", "^.*$", primary_artist]
         if hit.album:
             cmd += ["--parse-metadata", f"{hit.album}:%(album)s"]
         if hit.title:

server/actions.py

@@ -13,16 +13,21 @@ def _title(hit) -> str:
     return hit.album if hit.kind == "album" else (hit.title or hit.album or hit.artist)
 
 
+def _primary_artist(hit) -> str:
+    """First artist only — ignore featured/secondary artists."""
+    return (hit.artist.split(",")[0].strip() if hit.artist else "") or "unknown artist"
+
+
 def started_message(hit) -> str:
-    return f"Found '{_title(hit)}' by {hit.artist or 'unknown artist'} on {_source_label(hit)}. Downloading now."
+    return f"Found '{_title(hit)}' by {_primary_artist(hit)} on {_source_label(hit)}. Downloading now."
 
 
 def done_message(hit) -> str:
-    return f"Finished downloading '{_title(hit)}' by {hit.artist or 'unknown artist'}."
+    return f"Finished downloading '{_title(hit)}' by {_primary_artist(hit)}."
 
 
 def failed_message(hit) -> str:
-    return f"Failed to download '{_title(hit)}' by {hit.artist or 'unknown artist'}."
+    return f"Failed to download '{_title(hit)}' by {_primary_artist(hit)}."
 
 
 def _yt_path(hit, root: str) -> str:

tests/test_actions.py

@@ -28,6 +28,17 @@ def test_done_message_mentions_title():
     assert "Avril Lavigne" in msg
 
 
+def test_messages_use_only_first_artist():
+    hit = mf.Hit(source="youtube", kind="track", title="Under My Skin",
+                 artist="SLVMLORD, James John, BobbyGee", album="X", year="",
+                 payload={"videoId": "abc"})
+    for msg in (actions.started_message(hit), actions.done_message(hit),
+                actions.failed_message(hit)):
+        assert "SLVMLORD" in msg
+        assert "James John" not in msg
+        assert "BobbyGee" not in msg
+
+
 def test_perform_youtube_calls_act_youtube(monkeypatch):
     calls = {}
     monkeypatch.setattr(mf, "act_youtube",