diff --git a/worker/lyra_worker/_musicbrainz.py b/worker/lyra_worker/_musicbrainz.py
index 293032e..8cd8852 100644
--- a/worker/lyra_worker/_musicbrainz.py
+++ b/worker/lyra_worker/_musicbrainz.py
@@ -47,6 +47,7 @@ class MusicBrainzResolver:
 
         track_count = None
         total_duration_s = None
+        titles: tuple[str, ...] = ()
         rgid = rg.get("id")
         if rgid:
             rgfull = musicbrainzngs.get_release_group_by_id(rgid, includes=["releases"])
@@ -62,6 +63,7 @@ class MusicBrainzResolver:
                     track_count = len(tracks)
                     total_ms = sum(int((t.get("recording") or {}).get("length") or 0) for t in tracks)
                     total_duration_s = total_ms // 1000 if total_ms else None
+                    titles = tuple((t.get("recording") or {}).get("title", "") for t in tracks)
 
         return MBTarget(
             artist=canonical_artist,
@@ -69,4 +71,5 @@ class MusicBrainzResolver:
             track_count=track_count,
             total_duration_s=total_duration_s,
             year=year,
+            tracklist=titles,
         )
diff --git a/worker/lyra_worker/_mutagen.py b/worker/lyra_worker/_mutagen.py
new file mode 100644
index 0000000..6390063
--- /dev/null
+++ b/worker/lyra_worker/_mutagen.py
@@ -0,0 +1,48 @@
+import os
+
+from lyra_worker.library import safe_name
+
+_AUDIO_EXT = {".flac", ".mp3", ".m4a", ".opus", ".ogg", ".aac", ".wav"}
+
+
+def plan_track_names(names: list[str], tracklist: tuple[str, ...]) -> list[tuple[str, str, str, int]]:
+    """Map audio filenames -> (old_name, new_name, title, track_number).
+
+    Files are sorted; titles come from `tracklist` by position when available,
+    else the filename stem. Pure — no filesystem or tag I/O.
+    """
+    plan: list[tuple[str, str, str, int]] = []
+    audio = sorted(n for n in names if os.path.splitext(n)[1].lower() in _AUDIO_EXT)
+    for i, name in enumerate(audio):
+        ext = os.path.splitext(name)[1].lower()
+        title = tracklist[i] if i < len(tracklist) else os.path.splitext(name)[0]
+        new_name = f"{i + 1:02d} {safe_name(title)}{ext}"
+        plan.append((name, new_name, title, i + 1))
+    return plan
+
+
+class MutagenTagger:
+    """Real Tagger using mutagen (lazily imported). The tag-write is not unit-tested
+    offline (needs real audio); the naming logic (`plan_track_names`) is."""
+
+    def tag_album(self, album_dir: str, target) -> None:
+        import mutagen
+
+        names = os.listdir(album_dir)
+        for old_name, new_name, title, number in plan_track_names(names, target.tracklist):
+            path = os.path.join(album_dir, old_name)
+            audio = mutagen.File(path, easy=True)
+            if audio is None:  # unreadable/unsupported file — leave it untouched
+                continue
+            audio["artist"] = target.artist
+            audio["albumartist"] = target.artist
+            audio["album"] = target.album
+            audio["title"] = title
+            audio["tracknumber"] = str(number)
+            if target.year:
+                audio["date"] = str(target.year)
+            audio.save()
+
+            new_path = os.path.join(album_dir, new_name)
+            if os.path.abspath(new_path) != os.path.abspath(path) and not os.path.exists(new_path):
+                os.rename(path, new_path)
diff --git a/worker/requirements.txt b/worker/requirements.txt
index 906dc41..6565a3e 100644
--- a/worker/requirements.txt
+++ b/worker/requirements.txt
@@ -5,3 +5,4 @@ yt-dlp>=2024.1
 streamrip>=2.0
 requests>=2.31
 musicbrainzngs>=0.7.1
+mutagen>=1.47
diff --git a/worker/tests/test_mutagen.py b/worker/tests/test_mutagen.py
new file mode 100644
index 0000000..852ef1d
--- /dev/null
+++ b/worker/tests/test_mutagen.py
@@ -0,0 +1,20 @@
+from lyra_worker._mutagen import plan_track_names
+
+
+def test_plan_uses_tracklist_titles_and_numbers():
+    names = ["02-b.flac", "01-a.flac"]  # unsorted on purpose
+    plan = plan_track_names(names, ("Alpha", "Beta"))
+    assert plan == [
+        ("01-a.flac", "01 Alpha.flac", "Alpha", 1),
+        ("02-b.flac", "02 Beta.flac", "Beta", 2),
+    ]
+
+
+def test_plan_falls_back_to_filename_stem_and_sanitizes():
+    plan = plan_track_names(["10 - AC_DC.mp3"], ())  # no tracklist
+    assert plan[0][1] == "01 10 - AC_DC.mp3"  # stem reused, renumbered, safe
+
+
+def test_plan_ignores_non_audio_files():
+    plan = plan_track_names(["cover.jpg", "song.opus", "notes.txt"], ())
+    assert [p[0] for p in plan] == ["song.opus"]
diff --git a/worker/tests/test_mutagen_live.py b/worker/tests/test_mutagen_live.py
new file mode 100644
index 0000000..6a802c3
--- /dev/null
+++ b/worker/tests/test_mutagen_live.py
@@ -0,0 +1,31 @@
+import os
+import shutil
+
+import pytest
+
+pytestmark = pytest.mark.skipif(
+    not (os.environ.get("LYRA_LIVE_TESTS") and os.environ.get("LYRA_SAMPLE_AUDIO")),
+    reason="tags a real audio file; set LYRA_LIVE_TESTS=1 + LYRA_SAMPLE_AUDIO=/path/to/a.flac to run",
+)
+
+
+def test_tags_and_renames_a_real_file(tmp_path):
+    import mutagen
+
+    from lyra_worker._mutagen import MutagenTagger
+    from lyra_worker.types import MBTarget
+
+    ext = os.path.splitext(os.environ["LYRA_SAMPLE_AUDIO"])[1]
+    src = tmp_path / f"track1{ext}"
+    shutil.copy(os.environ["LYRA_SAMPLE_AUDIO"], src)
+
+    target = MBTarget(artist="John Mayer", album="Continuum", year=2006, tracklist=("Stop This Train",))
+    MutagenTagger().tag_album(str(tmp_path), target)
+
+    out = tmp_path / f"01 Stop This Train{ext}"
+    assert out.exists()
+    tagged = mutagen.File(str(out), easy=True)
+    assert tagged["artist"] == ["John Mayer"]
+    assert tagged["album"] == ["Continuum"]
+    assert tagged["title"] == ["Stop This Train"]
+    assert tagged["tracknumber"] == ["1"]