feat(listenbrainz): match collaboration top-songs via all credited artist MBIDs (#5670)

* refactor(agents): drop single Artist fields from Song, keep only Artists Song now represents credited artists solely via the Artists slice; the single Artist/ArtistMBID fields and the ArtistList passthrough are removed. Equals continues to hash the whole value. * refactor(lastfm,listenbrainz): build Song.Artists in built-in agents Last.fm and ListenBrainz now populate the Artists slice directly. For ListenBrainz top songs, all credited artist MBIDs are mapped (the combined display name on the first credit plus MBID-only collaborators) instead of keeping only the first MBID, feeding the matcher's per-MBID specificity. * refactor(external): set Song.Artists in top-songs enrichment getMatchingTopSongs now seeds an Artists entry from the known artist when a song carries none, replacing the single Artist/ArtistMBID writes. * refactor(plugins): fold single-artist SongRef into Song.Artists SongRef keeps its single Artist/ArtistMBID fields as part of the plugin wire contract; songRefToAgentSong now folds them into a one-element Artists list when a plugin sends no artists array. * refactor(matcher): read Song.Artists directly groupQueries consumes s.Artists now that ArtistList is gone; test inputs build the Artists slice. * fix(matcher): keep MBID-only artists as identity signals Review follow-up: an artist credited only by MBID (empty ID and name) was dropped before resolution in four places, defeating the multi-MBID matching path this PR adds. - matcher.groupQueries: treat a non-empty MBID as a usable artist signal - external.getMatchingTopSongs: backfill the primary credit's name/MBID when the agent left them empty - plugins.songRefToAgentSong: fold a single-artist SongRef when only ArtistMBID is set (not just when Artist name is set) - listenbrainz.topSongArtists: return nil instead of an empty-name placeholder when neither name nor MBIDs are present * fix(external): only backfill top-song artist onto an unnamed credit Review follow-up (codex P2): the previous backfill stamped the queried artist's MBID onto Artists[0] whenever it was empty, even when that credit already named a different (e.g. featured) artist — producing a mismatched name+MBID pair that could mis-rank matches. Now only an unnamed first credit is filled (it is, by construction, the queried artist); an already-named credit is left untouched. Signed-off-by: Deluan <deluan@navidrome.org> --------- Signed-off-by: Deluan <deluan@navidrome.org>
2026-07-09 17:18:45 +00:00 · 2026-06-26 17:06:14 -04:00 · 2026-06-26 17:06:14 -04:00 · bd9fa1c602
commit bd9fa1c602
parent 7b7721f002
16 changed files with 305 additions and 224 deletions
--- a/adapters/lastfm/agent.go
+++ b/adapters/lastfm/agent.go
@ -231,10 +231,9 @@ func (l *lastfmAgent) GetSimilarSongsByTrack(ctx context.Context, id, name, arti
 	res := make([]agents.Song, 0, len(resp))
 	for _, t := range resp {
 		res = append(res, agents.Song{
-			Name:       t.Name,
-			MBID:       t.MBID,
-			Artist:     t.Artist.Name,
-			ArtistMBID: t.Artist.MBID,
+			Name:    t.Name,
+			MBID:    t.MBID,
+			Artists: []agents.Artist{{Name: t.Artist.Name, MBID: t.Artist.MBID}},
 		})
 	}
 	return res, nil
--- a/adapters/lastfm/agent_test.go
+++ b/adapters/lastfm/agent_test.go
@ -309,11 +309,11 @@ var _ = Describe("lastfmAgent", func() {
 			f, _ := os.Open("tests/fixtures/lastfm.track.getsimilar.json")
 			httpClient.Res = http.Response{Body: f, StatusCode: 200}
 			Expect(agent.GetSimilarSongsByTrack(ctx, "123", "Just Can't Get Enough", "Depeche Mode", "", 5)).To(Equal([]agents.Song{
-				{Name: "Dreaming of Me", MBID: "027b553e-7c74-3ed4-a95e-1d4fea51f174", Artist: "Depeche Mode", ArtistMBID: "8538e728-ca0b-4321-b7e5-cff6565dd4c0"},
-				{Name: "Everything Counts", MBID: "5a5a3ca4-bdb8-4641-a674-9b54b9b319a6", Artist: "Depeche Mode", ArtistMBID: "8538e728-ca0b-4321-b7e5-cff6565dd4c0"},
-				{Name: "Don't You Want Me", MBID: "", Artist: "The Human League", ArtistMBID: "7adaabfb-acfb-47bc-8c7c-59471c2f0db8"},
-				{Name: "Tainted Love", MBID: "", Artist: "Soft Cell", ArtistMBID: "7fb50287-029d-47cc-825a-235ca28024b2"},
-				{Name: "Blue Monday", MBID: "727e84c6-1b56-31dd-a958-a5f46305cec0", Artist: "New Order", ArtistMBID: "f1106b17-dcbb-45f6-b938-199ccfab50cc"},
+				{Name: "Dreaming of Me", MBID: "027b553e-7c74-3ed4-a95e-1d4fea51f174", Artists: []agents.Artist{{Name: "Depeche Mode", MBID: "8538e728-ca0b-4321-b7e5-cff6565dd4c0"}}},
+				{Name: "Everything Counts", MBID: "5a5a3ca4-bdb8-4641-a674-9b54b9b319a6", Artists: []agents.Artist{{Name: "Depeche Mode", MBID: "8538e728-ca0b-4321-b7e5-cff6565dd4c0"}}},
+				{Name: "Don't You Want Me", MBID: "", Artists: []agents.Artist{{Name: "The Human League", MBID: "7adaabfb-acfb-47bc-8c7c-59471c2f0db8"}}},
+				{Name: "Tainted Love", MBID: "", Artists: []agents.Artist{{Name: "Soft Cell", MBID: "7fb50287-029d-47cc-825a-235ca28024b2"}}},
+				{Name: "Blue Monday", MBID: "727e84c6-1b56-31dd-a958-a5f46305cec0", Artists: []agents.Artist{{Name: "New Order", MBID: "f1106b17-dcbb-45f6-b938-199ccfab50cc"}}},
 			}))
 			Expect(httpClient.RequestCount).To(Equal(1))
 			Expect(httpClient.SavedRequest.URL.Query().Get("track")).To(Equal("Just Can't Get Enough"))
--- a/adapters/listenbrainz/agent.go
+++ b/adapters/listenbrainz/agent.go
@ -141,24 +141,37 @@ func (l *listenBrainzAgent) GetArtistTopSongs(ctx context.Context, id, artistNam

 	res := make([]agents.Song, len(resp))
 	for i, t := range resp {
-		mbid := ""
-		if len(t.ArtistMBIDs) > 0 {
-			mbid = t.ArtistMBIDs[0]
-		}
-
 		res[i] = agents.Song{
-			Album:      t.ReleaseName,
-			AlbumMBID:  t.ReleaseMBID,
-			Artist:     t.ArtistName,
-			ArtistMBID: mbid,
-			Duration:   t.DurationMs,
-			Name:       t.RecordingName,
-			MBID:       t.RecordingMbid,
+			Album:     t.ReleaseName,
+			AlbumMBID: t.ReleaseMBID,
+			Artists:   topSongArtists(t.ArtistName, t.ArtistMBIDs),
+			Duration:  t.DurationMs,
+			Name:      t.RecordingName,
+			MBID:      t.RecordingMbid,
 		}
 	}
 	return res, nil
 }

+// topSongArtists maps the top-recordings response, which carries a single combined display name
+// (e.g. "X feat. Y") plus a per-artist MBID list, onto agents.Artist. Names and MBIDs are not
+// positionally pairable, so the display name attaches to the first credit and any further MBIDs
+// become MBID-only collaborators — still valid identity signals for the matcher.
+func topSongArtists(name string, mbids []string) []agents.Artist {
+	if len(mbids) == 0 {
+		if name == "" {
+			return nil
+		}
+		return []agents.Artist{{Name: name}}
+	}
+	artists := make([]agents.Artist, len(mbids))
+	artists[0] = agents.Artist{Name: name, MBID: mbids[0]}
+	for i, m := range mbids[1:] {
+		artists[i+1] = agents.Artist{MBID: m}
+	}
+	return artists
+}
+
 func (l *listenBrainzAgent) GetSimilarArtists(ctx context.Context, id string, name string, mbid string, limit int) ([]agents.Artist, error) {
 	if mbid == "" {
 		return nil, agents.ErrNotFound
@ -203,7 +216,7 @@ func (l *listenBrainzAgent) GetSimilarSongsByTrack(ctx context.Context, id strin
 		songs[i] = agents.Song{
 			Album:     song.ReleaseName,
 			AlbumMBID: song.ReleaseMBID,
-			Artist:    song.Artist,
+			Artists:   []agents.Artist{{Name: song.Artist}},
 			MBID:      song.MBID,
 			Name:      song.Name,
 		}
--- a/adapters/listenbrainz/agent_test.go
+++ b/adapters/listenbrainz/agent_test.go
@ -249,24 +249,22 @@ var _ = Describe("listenBrainzAgent", func() {
 			Expect(err).ToNot(HaveOccurred())
 			Expect(data).To(Equal([]agents.Song{
 				{
-					ID:         "",
-					Name:       "world.execute(me);",
-					MBID:       "9980309d-3480-4e7e-89ce-fce971a452be",
-					Artist:     "Mili",
-					ArtistMBID: "d2a92ee2-27ce-4e71-bfc5-12e34fe8ef56",
-					Album:      "Miracle Milk",
-					AlbumMBID:  "38a8f6e1-0e34-4418-a89d-78240a367408",
-					Duration:   211912,
+					ID:        "",
+					Name:      "world.execute(me);",
+					MBID:      "9980309d-3480-4e7e-89ce-fce971a452be",
+					Artists:   []agents.Artist{{Name: "Mili", MBID: "d2a92ee2-27ce-4e71-bfc5-12e34fe8ef56"}},
+					Album:     "Miracle Milk",
+					AlbumMBID: "38a8f6e1-0e34-4418-a89d-78240a367408",
+					Duration:  211912,
 				},
 				{
-					ID:         "",
-					Name:       "String Theocracy",
-					MBID:       "afa2c83d-b17f-4029-b9da-790ea9250cf9",
-					Artist:     "Mili",
-					ArtistMBID: "d2a92ee2-27ce-4e71-bfc5-12e34fe8ef56",
-					Album:      "String Theocracy",
-					AlbumMBID:  "d79a38e3-7016-4f39-a31a-f495ce914b8e",
-					Duration:   174000,
+					ID:        "",
+					Name:      "String Theocracy",
+					MBID:      "afa2c83d-b17f-4029-b9da-790ea9250cf9",
+					Artists:   []agents.Artist{{Name: "Mili", MBID: "d2a92ee2-27ce-4e71-bfc5-12e34fe8ef56"}},
+					Album:     "String Theocracy",
+					AlbumMBID: "d79a38e3-7016-4f39-a31a-f495ce914b8e",
+					Duration:  174000,
 				},
 			}))
 		})
@ -278,17 +276,45 @@ var _ = Describe("listenBrainzAgent", func() {
 			Expect(err).ToNot(HaveOccurred())
 			Expect(data).To(Equal([]agents.Song{
 				{
-					ID:         "",
-					Name:       "world.execute(me);",
-					MBID:       "9980309d-3480-4e7e-89ce-fce971a452be",
-					Artist:     "Mili",
-					ArtistMBID: "d2a92ee2-27ce-4e71-bfc5-12e34fe8ef56",
-					Album:      "Miracle Milk",
-					AlbumMBID:  "38a8f6e1-0e34-4418-a89d-78240a367408",
-					Duration:   211912,
+					ID:        "",
+					Name:      "world.execute(me);",
+					MBID:      "9980309d-3480-4e7e-89ce-fce971a452be",
+					Artists:   []agents.Artist{{Name: "Mili", MBID: "d2a92ee2-27ce-4e71-bfc5-12e34fe8ef56"}},
+					Album:     "Miracle Milk",
+					AlbumMBID: "38a8f6e1-0e34-4418-a89d-78240a367408",
+					Duration:  211912,
 				},
 			}))
 		})
+
+		It("maps a multi-artist top song to one named artist plus MBID-only collaborators", func() {
+			body := `[{
+				"recording_name": "Collab",
+				"recording_mbid": "rec-1",
+				"artist_name": "Drake feat. Future",
+				"artist_mbids": ["mbid-drake", "mbid-future"],
+				"release_name": "Album",
+				"release_mbid": "rel-1",
+				"length": 200000
+			}]`
+			httpClient.Res = http.Response{Body: io.NopCloser(bytes.NewBufferString(body)), StatusCode: 200}
+			data, err := agent.GetArtistTopSongs(ctx, "", "", "mbid-drake", 1)
+			Expect(err).ToNot(HaveOccurred())
+			Expect(data).To(HaveLen(1))
+			Expect(data[0].Artists).To(Equal([]agents.Artist{
+				{Name: "Drake feat. Future", MBID: "mbid-drake"},
+				{MBID: "mbid-future"},
+			}))
+		})
+
+		It("leaves Artists nil when the top song carries no name or MBIDs", func() {
+			body := `[{"recording_name": "Anon", "recording_mbid": "rec-1", "artist_name": "", "artist_mbids": []}]`
+			httpClient.Res = http.Response{Body: io.NopCloser(bytes.NewBufferString(body)), StatusCode: 200}
+			data, err := agent.GetArtistTopSongs(ctx, "", "", "x", 1)
+			Expect(err).ToNot(HaveOccurred())
+			Expect(data).To(HaveLen(1))
+			Expect(data[0].Artists).To(BeNil())
+		})
 	})

 	Describe("GetSimilarArtists", func() {
@ -393,26 +419,24 @@ var _ = Describe("listenBrainzAgent", func() {
 			Expect(httpClient.SavedRequest.URL.String()).To(Equal(baseUrl + mbid))
 			Expect(resp).To(Equal([]agents.Song{
 				{
-					ID:         "",
-					Name:       "Take On Me",
-					MBID:       "12f65dca-de8f-43fe-a65d-f12a02aaadf3",
-					ISRC:       "",
-					Artist:     "a‐ha",
-					ArtistMBID: "",
-					Album:      "Hunting High and Low",
-					AlbumMBID:  "4ec07fe8-e7c6-3106-a0aa-fdf92f13f7fc",
-					Duration:   0,
+					ID:        "",
+					Name:      "Take On Me",
+					MBID:      "12f65dca-de8f-43fe-a65d-f12a02aaadf3",
+					ISRC:      "",
+					Artists:   []agents.Artist{{Name: "a‐ha"}},
+					Album:     "Hunting High and Low",
+					AlbumMBID: "4ec07fe8-e7c6-3106-a0aa-fdf92f13f7fc",
+					Duration:  0,
 				},
 				{
-					ID:         "",
-					Name:       "Wake Me Up Before You Go‐Go",
-					MBID:       "80033c72-aa19-4ba8-9227-afb075fec46e",
-					ISRC:       "",
-					Artist:     "Wham!",
-					ArtistMBID: "",
-					Album:      "Make It Big",
-					AlbumMBID:  "c143d542-48dc-446b-b523-1762da721638",
-					Duration:   0,
+					ID:        "",
+					Name:      "Wake Me Up Before You Go‐Go",
+					MBID:      "80033c72-aa19-4ba8-9227-afb075fec46e",
+					ISRC:      "",
+					Artists:   []agents.Artist{{Name: "Wham!"}},
+					Album:     "Make It Big",
+					AlbumMBID: "c143d542-48dc-446b-b523-1762da721638",
+					Duration:  0,
 				},
 			}))
 		})
@ -427,15 +451,14 @@ var _ = Describe("listenBrainzAgent", func() {
 			Expect(httpClient.SavedRequest.URL.String()).To(Equal(baseUrl + mbid))
 			Expect(resp).To(Equal([]agents.Song{
 				{
-					ID:         "",
-					Name:       "Take On Me",
-					MBID:       "12f65dca-de8f-43fe-a65d-f12a02aaadf3",
-					ISRC:       "",
-					Artist:     "a‐ha",
-					ArtistMBID: "",
-					Album:      "Hunting High and Low",
-					AlbumMBID:  "4ec07fe8-e7c6-3106-a0aa-fdf92f13f7fc",
-					Duration:   0,
+					ID:        "",
+					Name:      "Take On Me",
+					MBID:      "12f65dca-de8f-43fe-a65d-f12a02aaadf3",
+					ISRC:      "",
+					Artists:   []agents.Artist{{Name: "a‐ha"}},
+					Album:     "Hunting High and Low",
+					AlbumMBID: "4ec07fe8-e7c6-3106-a0aa-fdf92f13f7fc",
+					Duration:  0,
 				},
 			}))
 		})
--- a/core/agents/interfaces.go
+++ b/core/agents/interfaces.go
@ -34,16 +34,14 @@ type ExternalImage struct {
 }

 type Song struct {
-	ID         string
-	Name       string
-	MBID       string
-	ISRC       string
-	Artist     string
-	ArtistMBID string
-	Artists    []Artist // optional full artist list; ArtistList normalizes against Artist/ArtistMBID
-	Album      string
-	AlbumMBID  string
-	Duration   uint32 // Duration in milliseconds, 0 means unknown
+	ID        string
+	Name      string
+	MBID      string
+	ISRC      string
+	Artists   []Artist
+	Album     string
+	AlbumMBID string
+	Duration  uint32 // Duration in milliseconds, 0 means unknown
 }

 // Equals reports strict whole-value equality, used to dedup identical input songs. It hashes
@ -54,17 +52,6 @@ func (s Song) Equals(other Song) bool {
 	return h1 == h2
 }

-// ArtistList normalizes the single/multi-artist representations so callers never branch on len(Artists).
-func (s Song) ArtistList() []Artist {
-	if len(s.Artists) > 0 {
-		return s.Artists
-	}
-	if s.Artist != "" {
-		return []Artist{{Name: s.Artist, MBID: s.ArtistMBID}}
-	}
-	return nil
-}
-
 var (
 	ErrNotFound = errors.New("not found")
 )
--- a/core/agents/interfaces_test.go
+++ b/core/agents/interfaces_test.go
@ -6,7 +6,7 @@ import (
 )

 var _ = Describe("Song.Equals", func() {
-	base := Song{ID: "1", Name: "S", Artist: "A", Artists: []Artist{{ID: "x", Name: "A"}}}
+	base := Song{ID: "1", Name: "S", Artists: []Artist{{ID: "x", Name: "A"}}}
 	It("true for identical songs incl Artists", func() {
 		Expect(base.Equals(base)).To(BeTrue())
 	})
@ -21,27 +21,7 @@ var _ = Describe("Song.Equals", func() {
 		Expect(base.Equals(other)).To(BeFalse())
 	})
 	It("true when both have empty Artists and equal scalars", func() {
-		a := Song{ID: "1", Name: "S", Artist: "A"}
+		a := Song{ID: "1", Name: "S"}
 		Expect(a.Equals(a)).To(BeTrue())
 	})
 })
-
-var _ = Describe("Song.ArtistList", func() {
-	It("returns the Artists slice when present", func() {
-		s := Song{Artist: "Primary", ArtistMBID: "mbid-primary", Artists: []Artist{
-			{ID: "id-drake", Name: "Drake", MBID: "mbid-drake"},
-			{Name: "Future", MBID: "mbid-future"},
-		}}
-		Expect(s.ArtistList()).To(Equal([]Artist{
-			{ID: "id-drake", Name: "Drake", MBID: "mbid-drake"},
-			{Name: "Future", MBID: "mbid-future"},
-		}))
-	})
-	It("falls back to the single Artist field with empty ID", func() {
-		s := Song{Artist: "Drake", ArtistMBID: "mbid-drake"}
-		Expect(s.ArtistList()).To(Equal([]Artist{{Name: "Drake", MBID: "mbid-drake"}}))
-	})
-	It("returns empty when no artist is set", func() {
-		Expect(Song{}.ArtistList()).To(BeEmpty())
-	})
-})
--- a/core/external/provider.go
+++ b/core/external/provider.go
@ -471,13 +471,19 @@ func (e *provider) getMatchingTopSongs(ctx context.Context, agent agents.ArtistT
 		return nil, fmt.Errorf("failed to get top songs for artist %s: %w", artistName, err)
 	}

-	// Enrich songs with artist info if not already present (for top songs, we know the artist)
+	// Enrich top songs with the queried artist. A song with no artists, or whose first credit the
+	// agent left unnamed, is attributed to the queried artist. A first credit that already names an
+	// artist is left as-is: it may be a different (e.g. featured) artist, so stamping the queried
+	// MBID onto it would create a false name+MBID pairing.
 	for i := range songs {
-		if songs[i].Artist == "" {
-			songs[i].Artist = artistName
-		}
-		if songs[i].ArtistMBID == "" {
-			songs[i].ArtistMBID = artist.MbzArtistID
+		switch {
+		case len(songs[i].Artists) == 0:
+			songs[i].Artists = []agents.Artist{{Name: artistName, MBID: artist.MbzArtistID}}
+		case songs[i].Artists[0].Name == "":
+			songs[i].Artists[0].Name = artistName
+			if songs[i].Artists[0].MBID == "" {
+				songs[i].Artists[0].MBID = artist.MbzArtistID
+			}
 		}
 	}

--- a/core/external/provider_similarsongs_test.go
+++ b/core/external/provider_similarsongs_test.go
@ -73,7 +73,7 @@ var _ = Describe("Provider - SimilarSongs", func() {

 				agentsCombined.On("GetSimilarSongsByTrack", mock.Anything, "track-1", "Just Can't Get Enough", "Depeche Mode", "track-mbid", 5).
 					Return([]agents.Song{
-						{Name: "Dreaming of Me", MBID: "", Artist: "Depeche Mode", ArtistMBID: "artist-mbid"},
+						{Name: "Dreaming of Me", MBID: "", Artists: []agents.Artist{{Name: "Depeche Mode", MBID: "artist-mbid"}}},
 					}, nil).Once()

 				// Matcher artist resolution: resolve Depeche Mode in the artist table.
@ -177,7 +177,7 @@ var _ = Describe("Provider - SimilarSongs", func() {

 				agentsCombined.On("GetSimilarSongsByAlbum", mock.Anything, "album-1", "Speak & Spell", "Depeche Mode", "album-mbid", 5).
 					Return([]agents.Song{
-						{Name: "New Life", MBID: "song-mbid", Artist: "Depeche Mode"},
+						{Name: "New Life", MBID: "song-mbid", Artists: []agents.Artist{{Name: "Depeche Mode"}}},
 					}, nil).Once()

 				// Mock loadTracksByID - no ID matches
@ -254,7 +254,7 @@ var _ = Describe("Provider - SimilarSongs", func() {
 				artistRepo.On("Get", "artist-1").Return(&artist, nil).Once()
 				agentsCombined.On("GetSimilarSongsByArtist", mock.Anything, "artist-1", "Depeche Mode", "artist-mbid", 5).
 					Return([]agents.Song{
-						{Name: "Enjoy the Silence", MBID: "song-mbid", Artist: "Depeche Mode"},
+						{Name: "Enjoy the Silence", MBID: "song-mbid", Artists: []agents.Artist{{Name: "Depeche Mode"}}},
 					}, nil).Once()

 				// Mock loadTracksByID - no ID matches
--- a/core/external/provider_topsongs_test.go
+++ b/core/external/provider_topsongs_test.go
@ -76,6 +76,63 @@ var _ = Describe("Provider - TopSongs", func() {
 		mediaFileRepo.AssertExpectations(GinkgoT())
 	})

+	It("backfills name and MBID onto an unnamed primary credit (the queried artist) and matches", func() {
+		artist1 := model.Artist{ID: "artist-1", Name: "Artist One", MbzArtistID: "mbid-artist-1"}
+		artistRepo.On("GetAll", mock.AnythingOfType("model.QueryOptions")).Return(model.Artists{artist1}, nil)
+
+		// Agent leaves the first credit unnamed (e.g. an MBID-less collaborator slot). That blank
+		// credit IS the queried artist, so enrichment fills both name and MBID; the song then matches
+		// the queried artist's track via the backfilled identity.
+		agentSongs := []agents.Song{
+			{Name: "Song One", Artists: []agents.Artist{{}}},
+		}
+		ag.On("GetArtistTopSongs", ctx, "artist-1", "Artist One", "mbid-artist-1", 1).Return(agentSongs, nil).Once()
+
+		track := model.MediaFile{
+			ID: "song-1", Title: "Song One", ArtistID: "artist-1",
+			Participants: model.Participants{model.RoleArtist: model.ParticipantList{
+				{Artist: model.Artist{ID: "artist-1", Name: "Artist One", OrderArtistName: "artist one", MbzArtistID: "mbid-artist-1"}},
+			}},
+		}
+		mediaFileRepo.On("GetAll", mock.AnythingOfType("model.QueryOptions")).Return(model.MediaFiles{track}, nil)
+
+		songs, err := p.TopSongs(ctx, "Artist One", 1)
+
+		Expect(err).ToNot(HaveOccurred())
+		Expect(songs).To(HaveLen(1))
+		Expect(songs[0].ID).To(Equal("song-1"))
+	})
+
+	It("does not stamp the queried MBID onto an already-named different first credit", func() {
+		// The queried artist (One) appears only as a featured collaborator; the displayed first credit
+		// is a DIFFERENT artist (Two) returned without an MBID. Enrichment must NOT assign One's MBID
+		// to Two — only Two's name match (which fails here) or One's own credit may resolve the track.
+		artist1 := model.Artist{ID: "artist-1", Name: "Artist One", MbzArtistID: "mbid-artist-1"}
+		artistRepo.On("GetAll", mock.AnythingOfType("model.QueryOptions")).Return(model.Artists{artist1}, nil)
+
+		agentSongs := []agents.Song{
+			{Name: "Collab Song", Artists: []agents.Artist{{Name: "Artist Two"}}},
+		}
+		ag.On("GetArtistTopSongs", ctx, "artist-1", "Artist One", "mbid-artist-1", 1).Return(agentSongs, nil).Once()
+
+		// Library track is credited to Artist One (the queried artist) under a same title. If the
+		// queried MBID were wrongly stamped onto the "Artist Two" credit, that mismatched name+MBID
+		// could mis-resolve. With the guard, "Artist Two" stays MBID-less and does not match One's track.
+		track := model.MediaFile{
+			ID: "one-track", Title: "Collab Song", ArtistID: "artist-1",
+			Participants: model.Participants{model.RoleArtist: model.ParticipantList{
+				{Artist: model.Artist{ID: "artist-1", Name: "Artist One", OrderArtistName: "artist one", MbzArtistID: "mbid-artist-1"}},
+			}},
+		}
+		mediaFileRepo.On("GetAll", mock.AnythingOfType("model.QueryOptions")).Return(model.MediaFiles{track}, nil)
+
+		songs, err := p.TopSongs(ctx, "Artist One", 1)
+
+		Expect(err).ToNot(HaveOccurred())
+		// "Artist Two" (named, MBID-less, not in the library) does not resolve to One's track.
+		Expect(songs).To(BeEmpty())
+	})
+
 	It("returns nil for an unknown artist", func() {
 		// Mock artist not found
 		artistRepo.On("GetAll", mock.AnythingOfType("model.QueryOptions")).Return(model.Artists{}, nil).Once()
--- a/core/matcher/matcher.go
+++ b/core/matcher/matcher.go
@ -360,9 +360,9 @@ func groupQueries(songs []agents.Song, result map[int]model.MediaFile) []indexed
 			continue
 		}
 		var artists []queryArtist
-		for _, a := range s.ArtistList() {
+		for _, a := range s.Artists {
 			name := str.SanitizeFieldForSortingNoArticle(a.Name)
-			if a.ID == "" && name == "" {
+			if a.ID == "" && name == "" && a.MBID == "" {
 				continue
 			}
 			artists = append(artists, queryArtist{id: a.ID, name: name, mbid: a.MBID})
--- a/core/matcher/matcher_internal_test.go
+++ b/core/matcher/matcher_internal_test.go
@ -143,7 +143,7 @@ var _ = Describe("groupQueries", func() {

 	It("strips leading articles from artist names", func() {
 		songs := []agents.Song{
-			{Name: "Song A", Artist: "The Drake"},
+			{Name: "Song A", Artists: []agents.Artist{{Name: "The Drake"}}},
 		}
 		queries := groupQueries(songs, map[int]model.MediaFile{})
 		Expect(queries).To(HaveLen(1))
@ -162,32 +162,35 @@ var _ = Describe("groupQueries", func() {
 		Expect(queries[0].query.artists[0].name).To(Equal(""))
 	})

-	It("drops an artist with empty id and empty name but keeps usable ones", func() {
+	It("keeps an artist that carries only an MBID (empty id and name)", func() {
+		// ListenBrainz collaborators arrive as MBID-only when the API supplies a combined display
+		// name; the MBID is a usable identity signal and must not be dropped.
 		songs := []agents.Song{
-			{Name: "Song A", Artists: []agents.Artist{{Name: ""}, {Name: "Future"}}},
+			{Name: "Song A", Artists: []agents.Artist{{MBID: "mbz-future"}}},
 		}
 		queries := groupQueries(songs, map[int]model.MediaFile{})
 		Expect(queries).To(HaveLen(1))
 		Expect(queries[0].query.artists).To(HaveLen(1))
-		Expect(queries[0].query.artists[0].name).To(Equal("future"))
+		Expect(queries[0].query.artists[0].id).To(Equal(""))
+		Expect(queries[0].query.artists[0].name).To(Equal(""))
+		Expect(queries[0].query.artists[0].mbid).To(Equal("mbz-future"))
 	})

-	It("falls back to the single Artist field via ArtistList", func() {
+	It("drops a fully-empty artist (no id, name, or mbid) but keeps usable ones", func() {
 		songs := []agents.Song{
-			{Name: "Song A", Artist: "Future", ArtistMBID: "mbid-1"},
+			{Name: "Song A", Artists: []agents.Artist{{}, {Name: "Future"}}},
 		}
 		queries := groupQueries(songs, map[int]model.MediaFile{})
 		Expect(queries).To(HaveLen(1))
 		Expect(queries[0].query.artists).To(HaveLen(1))
 		Expect(queries[0].query.artists[0].name).To(Equal("future"))
-		Expect(queries[0].query.artists[0].mbid).To(Equal("mbid-1"))
 	})

 	It("skips already-matched songs and songs with no usable artist", func() {
 		songs := []agents.Song{
-			{Name: "Already Matched", Artist: "Drake"},
+			{Name: "Already Matched", Artists: []agents.Artist{{Name: "Drake"}}},
 			{Name: "No Artist"},
-			{Name: "Song C", Artist: "Future"},
+			{Name: "Song C", Artists: []agents.Artist{{Name: "Future"}}},
 		}
 		queries := groupQueries(songs, map[int]model.MediaFile{0: {ID: "done"}})
 		Expect(queries).To(HaveLen(1))
--- a/core/matcher/matcher_test.go
+++ b/core/matcher/matcher_test.go
@ -107,7 +107,7 @@ var _ = Describe("Matcher", func() {
 			It("matches songs with an ID field to MediaFiles by ID", func() {
 				conf.Server.Matcher.FuzzyThreshold = 100
 				songs := []agents.Song{
-					{ID: "track-1", Name: "Some Song", Artist: "Some Artist"},
+					{ID: "track-1", Name: "Some Song", Artists: []agents.Artist{{Name: "Some Artist"}}},
 				}
 				idMatch := model.MediaFile{
 					ID: "track-1", Title: "Some Song", Artist: "Some Artist",
@ -125,7 +125,7 @@ var _ = Describe("Matcher", func() {
 			It("matches songs with MBID to tracks with matching mbz_recording_id", func() {
 				conf.Server.Matcher.FuzzyThreshold = 100
 				songs := []agents.Song{
-					{Name: "Paranoid Android", MBID: "abc-123", Artist: "Radiohead"},
+					{Name: "Paranoid Android", MBID: "abc-123", Artists: []agents.Artist{{Name: "Radiohead"}}},
 				}
 				mbidMatch := model.MediaFile{
 					ID: "track-mbid", Title: "Paranoid Android", Artist: "Radiohead",
@ -144,7 +144,7 @@ var _ = Describe("Matcher", func() {
 			It("matches songs with ISRC to tracks with matching ISRC tag", func() {
 				conf.Server.Matcher.FuzzyThreshold = 100
 				songs := []agents.Song{
-					{Name: "Paranoid Android", ISRC: "GBAYE0000351", Artist: "Radiohead"},
+					{Name: "Paranoid Android", ISRC: "GBAYE0000351", Artists: []agents.Artist{{Name: "Radiohead"}}},
 				}
 				isrcMatch := model.MediaFile{
 					ID: "track-isrc", Title: "Paranoid Android", Artist: "Radiohead",
@ -163,7 +163,7 @@ var _ = Describe("Matcher", func() {
 			It("matches songs by title and artist name", func() {
 				conf.Server.Matcher.FuzzyThreshold = 100
 				songs := []agents.Song{
-					{Name: "Enjoy the Silence", Artist: "Depeche Mode"},
+					{Name: "Enjoy the Silence", Artists: []agents.Artist{{Name: "Depeche Mode"}}},
 				}
 				titleMatch := model.MediaFile{
 					ID: "track-title", Title: "Enjoy the Silence", Artist: "Depeche Mode",
@ -179,7 +179,7 @@ var _ = Describe("Matcher", func() {
 			It("matches songs with fuzzy title similarity", func() {
 				conf.Server.Matcher.FuzzyThreshold = 85
 				songs := []agents.Song{
-					{Name: "Bohemian Rhapsody", Artist: "Queen"},
+					{Name: "Bohemian Rhapsody", Artists: []agents.Artist{{Name: "Queen"}}},
 				}
 				fuzzyMatch := model.MediaFile{
 					ID: "track-fuzzy", Title: "Bohemian Rhapsody (Live)", Artist: "Queen",
@ -195,7 +195,7 @@ var _ = Describe("Matcher", func() {
 			It("does not match completely different titles", func() {
 				conf.Server.Matcher.FuzzyThreshold = 85
 				songs := []agents.Song{
-					{Name: "Yesterday", Artist: "The Beatles"},
+					{Name: "Yesterday", Artists: []agents.Artist{{Name: "The Beatles"}}},
 				}
 				differentTracks := model.MediaFiles{
 					{ID: "different", Title: "Tomorrow Never Knows", Artist: "The Beatles",
@ -213,8 +213,8 @@ var _ = Describe("Matcher", func() {
 			It("removes duplicates when different input songs match the same library track", func() {
 				conf.Server.Matcher.FuzzyThreshold = 85
 				songs := []agents.Song{
-					{Name: "Bohemian Rhapsody (Live)", Artist: "Queen"},
-					{Name: "Bohemian Rhapsody (Original Mix)", Artist: "Queen"},
+					{Name: "Bohemian Rhapsody (Live)", Artists: []agents.Artist{{Name: "Queen"}}},
+					{Name: "Bohemian Rhapsody (Original Mix)", Artists: []agents.Artist{{Name: "Queen"}}},
 				}
 				libraryTrack := model.MediaFile{
 					ID: "br-live", Title: "Bohemian Rhapsody (Live)", Artist: "Queen",
@ -230,8 +230,8 @@ var _ = Describe("Matcher", func() {
 			It("preserves duplicates when identical input songs match the same library track", func() {
 				conf.Server.Matcher.FuzzyThreshold = 85
 				songs := []agents.Song{
-					{Name: "Bohemian Rhapsody", Artist: "Queen", Album: "A Night at the Opera"},
-					{Name: "Bohemian Rhapsody", Artist: "Queen", Album: "A Night at the Opera"},
+					{Name: "Bohemian Rhapsody", Artists: []agents.Artist{{Name: "Queen"}}, Album: "A Night at the Opera"},
+					{Name: "Bohemian Rhapsody", Artists: []agents.Artist{{Name: "Queen"}}, Album: "A Night at the Opera"},
 				}
 				libraryTrack := model.MediaFile{
 					ID: "br", Title: "Bohemian Rhapsody", Artist: "Queen", Album: "A Night at the Opera",
@ -253,7 +253,7 @@ var _ = Describe("Matcher", func() {
 				// and short-circuit the MBID phase entirely, so no MBID fetch should
 				// occur even though an mbz_recording_id exists in the input.
 				songs := []agents.Song{
-					{ID: "track-id", Name: "Song", MBID: "mbid-1", Artist: "Artist"},
+					{ID: "track-id", Name: "Song", MBID: "mbid-1", Artists: []agents.Artist{{Name: "Artist"}}},
 				}
 				idMatch := model.MediaFile{
 					ID: "track-id", Title: "Song", Artist: "Artist",
@ -271,9 +271,9 @@ var _ = Describe("Matcher", func() {
 			It("returns at most 'count' results", func() {
 				conf.Server.Matcher.FuzzyThreshold = 100
 				songs := []agents.Song{
-					{Name: "Song A", Artist: "Artist"},
-					{Name: "Song B", Artist: "Artist"},
-					{Name: "Song C", Artist: "Artist"},
+					{Name: "Song A", Artists: []agents.Artist{{Name: "Artist"}}},
+					{Name: "Song B", Artists: []agents.Artist{{Name: "Artist"}}},
+					{Name: "Song C", Artists: []agents.Artist{{Name: "Artist"}}},
 				}
 				tracks := model.MediaFiles{
 					{ID: "a", Title: "Song A", Artist: "Artist",
@ -304,7 +304,7 @@ var _ = Describe("Matcher", func() {
 		Context("artist grouping", func() {
 			It("groups title-phase tracks by participant artist ID, not display Artist", func() {
 				songs := []agents.Song{
-					{Name: "Song A", Artist: "Daft Punk"},
+					{Name: "Song A", Artists: []agents.Artist{{Name: "Daft Punk"}}},
 				}
 				// Display Artist differs from the query artist; only the participant
 				// with order_artist_name "daft punk" routes to this query bucket.
@ -326,7 +326,7 @@ var _ = Describe("Matcher", func() {

 			It("matches a track that credits the searched artist as a collaborator", func() {
 				songs := []agents.Song{
-					{Name: "Crazy", Artist: "INXS"},
+					{Name: "Crazy", Artists: []agents.Artist{{Name: "INXS"}}},
 				}
 				// "Par-T-One vs. INXS" — display Artist is the collaboration, but INXS is a
 				// credited artist participant. Searching INXS must match it.
@ -347,7 +347,7 @@ var _ = Describe("Matcher", func() {

 			It("does not match a track where the searched artist is only the album artist", func() {
 				songs := []agents.Song{
-					{Name: "Qmart", Artist: "808 State"},
+					{Name: "Qmart", Artists: []agents.Artist{{Name: "808 State"}}},
 				}
 				// Track performed by Björk on an "808 State" compilation: 808 State is the
 				// albumartist, Björk is the performer. Searching 808 State must NOT match it.
@ -379,7 +379,7 @@ var _ = Describe("Matcher", func() {

 			It("resolves the artist by ArtistMBID when the name differs", func() {
 				songs := []agents.Song{
-					{Name: "Song A", Artist: "Typo Artist", ArtistMBID: "mbid-9"},
+					{Name: "Song A", Artists: []agents.Artist{{Name: "Typo Artist", MBID: "mbid-9"}}},
 				}
 				track := model.MediaFile{
 					ID: "by-mbid", Title: "Song A", Artist: "Correct Artist",
@ -403,8 +403,8 @@ var _ = Describe("Matcher", func() {
 				// Two agent results for the same MusicBrainz artist but spelled differently
 				// (an alias). Both must match the artist's track via the shared MBID.
 				songs := []agents.Song{
-					{Name: "Song A", Artist: "Alias One", ArtistMBID: "mbid-shared"},
-					{Name: "Song B", Artist: "Alias Two", ArtistMBID: "mbid-shared"},
+					{Name: "Song A", Artists: []agents.Artist{{Name: "Alias One", MBID: "mbid-shared"}}},
+					{Name: "Song B", Artists: []agents.Artist{{Name: "Alias Two", MBID: "mbid-shared"}}},
 				}
 				artist := model.Artist{ID: "a-shared", Name: "Canonical", OrderArtistName: "canonical", MbzArtistID: "mbid-shared"}
 				trackA := model.MediaFile{ID: "ta", Title: "Song A", Artist: "Canonical", Participants: artistParticipants(artist)}
@ -427,8 +427,8 @@ var _ = Describe("Matcher", func() {
 		Context("title phase DB errors", func() {
 			It("returns an error when the title query fails and nothing else matched", func() {
 				songs := []agents.Song{
-					{Name: "Song A", Artist: "Artist One"},
-					{Name: "Song B", Artist: "Artist Two"},
+					{Name: "Song A", Artists: []agents.Artist{{Name: "Artist One"}}},
+					{Name: "Song B", Artists: []agents.Artist{{Name: "Artist Two"}}},
 				}
 				allowIdentifierPhases()
 				artistRepo.On("GetAll", mock.Anything).Return(model.Artists{
@ -445,8 +445,8 @@ var _ = Describe("Matcher", func() {

 			It("keeps exact-phase matches when the title query fails", func() {
 				songs := []agents.Song{
-					{ID: "track-1", Name: "Exact Song", Artist: "Exact Artist"},
-					{Name: "Fuzzy Song", Artist: "Fuzzy Artist"},
+					{ID: "track-1", Name: "Exact Song", Artists: []agents.Artist{{Name: "Exact Artist"}}},
+					{Name: "Fuzzy Song", Artists: []agents.Artist{{Name: "Fuzzy Artist"}}},
 				}
 				idMatch := model.MediaFile{ID: "track-1", Title: "Exact Song", Artist: "Exact Artist"}
 				expectIDPhase(model.MediaFiles{idMatch})
@ -500,7 +500,7 @@ var _ = Describe("Matcher", func() {
 			It("matches a single-artist song against a track crediting several artists", func() {
 				conf.Server.Matcher.FuzzyThreshold = 85
 				songs := []agents.Song{
-					{Name: "Life Is Good", Artist: "Future"},
+					{Name: "Life Is Good", Artists: []agents.Artist{{Name: "Future"}}},
 				}
 				track := model.MediaFile{
 					ID: "multi", Title: "Life Is Good", Artist: "Future feat. Drake",
@ -568,9 +568,9 @@ var _ = Describe("Matcher", func() {
 	Describe("MatchSongsIndexed", func() {
 		It("returns index-keyed map of matched songs", func() {
 			songs := []agents.Song{
-				{ID: "track-1", Name: "Song One", Artist: "Artist A"},
-				{ID: "track-2", Name: "Song Two", Artist: "Artist B"},
-				{ID: "track-3", Name: "Song Three", Artist: "Artist C"},
+				{ID: "track-1", Name: "Song One", Artists: []agents.Artist{{Name: "Artist A"}}},
+				{ID: "track-2", Name: "Song Two", Artists: []agents.Artist{{Name: "Artist B"}}},
+				{ID: "track-3", Name: "Song Three", Artists: []agents.Artist{{Name: "Artist C"}}},
 			}
 			mf1 := model.MediaFile{ID: "track-1", Title: "Song One", Artist: "Artist A"}
 			mf2 := model.MediaFile{ID: "track-2", Title: "Song Two", Artist: "Artist B"}
@ -589,8 +589,8 @@ var _ = Describe("Matcher", func() {

 		It("preserves original indices when some songs don't match", func() {
 			songs := []agents.Song{
-				{Name: "Unknown Song", Artist: "Unknown Artist"},
-				{ID: "track-1", Name: "Known Song", Artist: "Known Artist"},
+				{Name: "Unknown Song", Artists: []agents.Artist{{Name: "Unknown Artist"}}},
+				{ID: "track-1", Name: "Known Song", Artists: []agents.Artist{{Name: "Known Artist"}}},
 			}
 			mf1 := model.MediaFile{ID: "track-1", Title: "Known Song", Artist: "Known Artist"}

@ -629,7 +629,7 @@ var _ = Describe("Matcher", func() {
 				Participants: artistParticipants(model.Artist{ID: "dm", Name: "Depeche Mode", OrderArtistName: "depeche mode", MbzArtistID: "artist-mbid-123"}),
 			}
 			songs := []agents.Song{
-				{Name: "Similar Song", Artist: "Depeche Mode", ArtistMBID: "artist-mbid-123", Album: "Violator", AlbumMBID: "album-mbid-456"},
+				{Name: "Similar Song", Artists: []agents.Artist{{Name: "Depeche Mode", MBID: "artist-mbid-123"}}, Album: "Violator", AlbumMBID: "album-mbid-456"},
 			}

 			allowTitlePhase(model.MediaFiles{wrongMatch, correctMatch})
@ -651,7 +651,7 @@ var _ = Describe("Matcher", func() {
 				Participants: artistParticipants(model.Artist{ID: "oa", Name: "Other Artist", OrderArtistName: "other artist"}),
 			}
 			songs := []agents.Song{
-				{Name: "Similar Song", Artist: "Depeche Mode", Album: "Violator"},
+				{Name: "Similar Song", Artists: []agents.Artist{{Name: "Depeche Mode"}}, Album: "Violator"},
 			}

 			allowTitlePhase(model.MediaFiles{wrongMatch, correctMatch})
@ -673,7 +673,7 @@ var _ = Describe("Matcher", func() {
 				Participants: artistParticipants(model.Artist{ID: "oa", Name: "Other Artist", OrderArtistName: "other artist"}),
 			}
 			songs := []agents.Song{
-				{Name: "Similar Song", Artist: "Depeche Mode"},
+				{Name: "Similar Song", Artists: []agents.Artist{{Name: "Depeche Mode"}}},
 			}

 			allowTitlePhase(model.MediaFiles{wrongMatch, correctMatch})
@ -710,9 +710,9 @@ var _ = Describe("Matcher", func() {
 			}

 			songs := []agents.Song{
-				{Name: "Yesterday", Artist: "The Beatles", Album: "Help!"},
-				{Name: "Yesterday", Artist: "Ray Charles", Album: "Greatest Hits"},
-				{Name: "Yesterday", Artist: "Frank Sinatra", Album: "My Way"},
+				{Name: "Yesterday", Artists: []agents.Artist{{Name: "The Beatles"}}, Album: "Help!"},
+				{Name: "Yesterday", Artists: []agents.Artist{{Name: "Ray Charles"}}, Album: "Greatest Hits"},
+				{Name: "Yesterday", Artists: []agents.Artist{{Name: "Frank Sinatra"}}, Album: "My Way"},
 			}

 			allowTitlePhase(model.MediaFiles{cover1, cover2, cover3})
@ -742,8 +742,8 @@ var _ = Describe("Matcher", func() {
 			}

 			songs := []agents.Song{
-				{Name: "Song A", Artist: "Artist One", ArtistMBID: "mbid-1", Album: "Album One", AlbumMBID: "album-mbid-1"},
-				{Name: "Song B", Artist: "Artist Two"},
+				{Name: "Song A", Artists: []agents.Artist{{Name: "Artist One", MBID: "mbid-1"}}, Album: "Album One", AlbumMBID: "album-mbid-1"},
+				{Name: "Song B", Artists: []agents.Artist{{Name: "Artist Two"}}},
 			}

 			allowTitlePhase(model.MediaFiles{lessAccurateMatch, preciseMatch, artistTwoMatch})
@ -758,7 +758,7 @@ var _ = Describe("Matcher", func() {

 		It("uses the resolved artist MBID for specificity (level 5)", func() {
 			songs := []agents.Song{
-				{Name: "Song A", Artist: "Artist One", ArtistMBID: "mbid-1", Album: "Album One", AlbumMBID: "album-mbid-1"},
+				{Name: "Song A", Artists: []agents.Artist{{Name: "Artist One", MBID: "mbid-1"}}, Album: "Album One", AlbumMBID: "album-mbid-1"},
 			}
 			// Two tracks with the same title and album; only the one whose resolved artist
 			// carries mbid-1 (and whose album MBID matches) wins via Level 5. Without the
@ -788,7 +788,7 @@ var _ = Describe("Matcher", func() {
 				conf.Server.Matcher.FuzzyThreshold = 85

 				songs := []agents.Song{
-					{Name: "Paranoid Android", Artist: "Radiohead"},
+					{Name: "Paranoid Android", Artists: []agents.Artist{{Name: "Radiohead"}}},
 				}
 				artistTracks := model.MediaFiles{
 					{ID: "remastered", Title: "Paranoid Android - Remastered", Artist: "Radiohead",
@ -809,7 +809,7 @@ var _ = Describe("Matcher", func() {
 				conf.Server.Matcher.FuzzyThreshold = 85

 				songs := []agents.Song{
-					{Name: "Bohemian Rhapsody", Artist: "Queen"},
+					{Name: "Bohemian Rhapsody", Artists: []agents.Artist{{Name: "Queen"}}},
 				}
 				artistTracks := model.MediaFiles{
 					{ID: "live", Title: "Bohemian Rhapsody (Live)", Artist: "Queen",
@ -832,7 +832,7 @@ var _ = Describe("Matcher", func() {
 				conf.Server.Matcher.FuzzyThreshold = 100

 				songs := []agents.Song{
-					{Name: "Paranoid Android", Artist: "Radiohead"},
+					{Name: "Paranoid Android", Artists: []agents.Artist{{Name: "Radiohead"}}},
 				}
 				artistTracks := model.MediaFiles{
 					{ID: "remastered", Title: "Paranoid Android - Remastered", Artist: "Radiohead",
@ -854,7 +854,7 @@ var _ = Describe("Matcher", func() {
 				conf.Server.Matcher.FuzzyThreshold = 75

 				songs := []agents.Song{
-					{Name: "Song", Artist: "Artist"},
+					{Name: "Song", Artists: []agents.Artist{{Name: "Artist"}}},
 				}
 				artistTracks := model.MediaFiles{
 					{ID: "extended", Title: "Song (Extended Mix)", Artist: "Artist",
@ -881,7 +881,7 @@ var _ = Describe("Matcher", func() {

 		It("matches album with (Remaster) suffix", func() {
 			songs := []agents.Song{
-				{Name: "Bohemian Rhapsody", Artist: "Queen", Album: "A Night at the Opera"},
+				{Name: "Bohemian Rhapsody", Artists: []agents.Artist{{Name: "Queen"}}, Album: "A Night at the Opera"},
 			}
 			correctMatch := model.MediaFile{
 				ID: "correct", Title: "Bohemian Rhapsody", Artist: "Queen", Album: "A Night at the Opera (2011 Remaster)",
@ -903,7 +903,7 @@ var _ = Describe("Matcher", func() {

 		It("matches album with (Deluxe Edition) suffix", func() {
 			songs := []agents.Song{
-				{Name: "Enjoy the Silence", Artist: "Depeche Mode", Album: "Violator"},
+				{Name: "Enjoy the Silence", Artists: []agents.Artist{{Name: "Depeche Mode"}}, Album: "Violator"},
 			}
 			correctMatch := model.MediaFile{
 				ID: "correct", Title: "Enjoy the Silence", Artist: "Depeche Mode", Album: "Violator (Deluxe Edition)",
@ -925,7 +925,7 @@ var _ = Describe("Matcher", func() {

 		It("prefers exact album match over fuzzy album match", func() {
 			songs := []agents.Song{
-				{Name: "Enjoy the Silence", Artist: "Depeche Mode", Album: "Violator"},
+				{Name: "Enjoy the Silence", Artists: []agents.Artist{{Name: "Depeche Mode"}}, Album: "Violator"},
 			}
 			exactMatch := model.MediaFile{
 				ID: "exact", Title: "Enjoy the Silence", Artist: "Depeche Mode", Album: "Violator",
@ -948,7 +948,7 @@ var _ = Describe("Matcher", func() {
 		It("prefers a more specific match over a starred track when PreferStarred is enabled", func() {
 			conf.Server.Matcher.PreferStarred = true
 			songs := []agents.Song{
-				{Name: "Enjoy the Silence", Artist: "Depeche Mode", Album: "Violator"},
+				{Name: "Enjoy the Silence", Artists: []agents.Artist{{Name: "Depeche Mode"}}, Album: "Violator"},
 			}
 			albumMatch := model.MediaFile{
 				ID: "album-match", Title: "Enjoy the Silence", Artist: "Depeche Mode", Album: "Violator",
@ -969,7 +969,7 @@ var _ = Describe("Matcher", func() {
 		It("prefers a more specific match over a 4-star track when PreferStarred is enabled", func() {
 			conf.Server.Matcher.PreferStarred = true
 			songs := []agents.Song{
-				{Name: "Enjoy the Silence", Artist: "Depeche Mode", Album: "Violator"},
+				{Name: "Enjoy the Silence", Artists: []agents.Artist{{Name: "Depeche Mode"}}, Album: "Violator"},
 			}
 			albumMatch := model.MediaFile{
 				ID: "album-match", Title: "Enjoy the Silence", Artist: "Depeche Mode", Album: "Violator",
@ -990,7 +990,7 @@ var _ = Describe("Matcher", func() {
 		It("prefers a starred track when specificity and overlap are equal", func() {
 			conf.Server.Matcher.PreferStarred = true
 			songs := []agents.Song{
-				{Name: "Enjoy the Silence", Artist: "Depeche Mode", Album: "Violator"},
+				{Name: "Enjoy the Silence", Artists: []agents.Artist{{Name: "Depeche Mode"}}, Album: "Violator"},
 			}
 			// Both credit the same single artist and the same album → equal specificity AND equal overlap.
 			plain := model.MediaFile{
@ -1017,7 +1017,7 @@ var _ = Describe("Matcher", func() {

 		It("prefers tracks with matching duration", func() {
 			songs := []agents.Song{
-				{Name: "Similar Song", Artist: "Test Artist", Duration: 180000},
+				{Name: "Similar Song", Artists: []agents.Artist{{Name: "Test Artist"}}, Duration: 180000},
 			}
 			correctMatch := model.MediaFile{
 				ID: "correct", Title: "Similar Song", Artist: "Test Artist", Duration: 180.0,
@ -1039,7 +1039,7 @@ var _ = Describe("Matcher", func() {

 		It("matches tracks with close duration", func() {
 			songs := []agents.Song{
-				{Name: "Similar Song", Artist: "Test Artist", Duration: 180000},
+				{Name: "Similar Song", Artists: []agents.Artist{{Name: "Test Artist"}}, Duration: 180000},
 			}
 			closeDuration := model.MediaFile{
 				ID: "close-duration", Title: "Similar Song", Artist: "Test Artist", Duration: 182.5,
@ -1057,7 +1057,7 @@ var _ = Describe("Matcher", func() {

 		It("prefers closer duration over farther duration", func() {
 			songs := []agents.Song{
-				{Name: "Similar Song", Artist: "Test Artist", Duration: 180000},
+				{Name: "Similar Song", Artists: []agents.Artist{{Name: "Test Artist"}}, Duration: 180000},
 			}
 			closeDuration := model.MediaFile{
 				ID: "close", Title: "Similar Song", Artist: "Test Artist", Duration: 181.0,
@ -1079,7 +1079,7 @@ var _ = Describe("Matcher", func() {

 		It("still matches when no tracks have matching duration", func() {
 			songs := []agents.Song{
-				{Name: "Similar Song", Artist: "Test Artist", Duration: 180000},
+				{Name: "Similar Song", Artists: []agents.Artist{{Name: "Test Artist"}}, Duration: 180000},
 			}
 			differentDuration := model.MediaFile{
 				ID: "different", Title: "Similar Song", Artist: "Test Artist", Duration: 300.0,
@ -1097,7 +1097,7 @@ var _ = Describe("Matcher", func() {

 		It("prefers title match over duration match when titles differ", func() {
 			songs := []agents.Song{
-				{Name: "Similar Song", Artist: "Test Artist", Duration: 180000},
+				{Name: "Similar Song", Artists: []agents.Artist{{Name: "Test Artist"}}, Duration: 180000},
 			}
 			differentTitle := model.MediaFile{
 				ID: "wrong-title", Title: "Different Song", Artist: "Test Artist", Duration: 180.0,
@ -1119,7 +1119,7 @@ var _ = Describe("Matcher", func() {

 		It("matches without duration filtering when agent duration is 0", func() {
 			songs := []agents.Song{
-				{Name: "Similar Song", Artist: "Test Artist", Duration: 0},
+				{Name: "Similar Song", Artists: []agents.Artist{{Name: "Test Artist"}}, Duration: 0},
 			}
 			anyTrack := model.MediaFile{
 				ID: "any", Title: "Similar Song", Artist: "Test Artist", Duration: 999.0,
@ -1137,7 +1137,7 @@ var _ = Describe("Matcher", func() {

 		It("handles very short songs with close duration", func() {
 			songs := []agents.Song{
-				{Name: "Short Song", Artist: "Test Artist", Duration: 30000},
+				{Name: "Short Song", Artists: []agents.Artist{{Name: "Test Artist"}}, Duration: 30000},
 			}
 			shortTrack := model.MediaFile{
 				ID: "short", Title: "Short Song", Artist: "Test Artist", Duration: 31.0,
@ -1155,8 +1155,8 @@ var _ = Describe("Matcher", func() {

 		It("matches same title+artist songs to their own closest-duration track", func() {
 			songs := []agents.Song{
-				{Name: "Same Song", Artist: "Same Artist", Duration: 180000},
-				{Name: "Same Song", Artist: "Same Artist", Duration: 240000},
+				{Name: "Same Song", Artists: []agents.Artist{{Name: "Same Artist"}}, Duration: 180000},
+				{Name: "Same Song", Artists: []agents.Artist{{Name: "Same Artist"}}, Duration: 240000},
 			}
 			shortTrack := model.MediaFile{
 				ID: "short", Title: "Same Song", Artist: "Same Artist", Duration: 180.0,
@ -1185,10 +1185,10 @@ var _ = Describe("Matcher", func() {

 		It("handles mixed scenario with both identical and different input songs", func() {
 			songs := []agents.Song{
-				{Name: "Yesterday", Artist: "The Beatles", Album: "Help!"},
-				{Name: "Yesterday (Remastered)", Artist: "The Beatles", Album: "1"},
-				{Name: "Yesterday", Artist: "The Beatles", Album: "Help!"},
-				{Name: "Yesterday (Anthology)", Artist: "The Beatles", Album: "Anthology"},
+				{Name: "Yesterday", Artists: []agents.Artist{{Name: "The Beatles"}}, Album: "Help!"},
+				{Name: "Yesterday (Remastered)", Artists: []agents.Artist{{Name: "The Beatles"}}, Album: "1"},
+				{Name: "Yesterday", Artists: []agents.Artist{{Name: "The Beatles"}}, Album: "Help!"},
+				{Name: "Yesterday (Anthology)", Artists: []agents.Artist{{Name: "The Beatles"}}, Album: "Anthology"},
 			}
 			libraryTrack := model.MediaFile{
 				ID: "yesterday", Title: "Yesterday", Artist: "The Beatles", Album: "Help!",
@ -1207,9 +1207,9 @@ var _ = Describe("Matcher", func() {

 		It("does not deduplicate songs that match different library tracks", func() {
 			songs := []agents.Song{
-				{Name: "Song A", Artist: "Artist"},
-				{Name: "Song B", Artist: "Artist"},
-				{Name: "Song C", Artist: "Artist"},
+				{Name: "Song A", Artists: []agents.Artist{{Name: "Artist"}}},
+				{Name: "Song B", Artists: []agents.Artist{{Name: "Artist"}}},
+				{Name: "Song C", Artists: []agents.Artist{{Name: "Artist"}}},
 			}
 			trackA := model.MediaFile{ID: "track-a", Title: "Song A", Artist: "Artist",
 				Participants: artistParticipants(model.Artist{ID: "art", Name: "Artist", OrderArtistName: "artist"}),
@ -1234,10 +1234,10 @@ var _ = Describe("Matcher", func() {

 		It("respects count limit after deduplication", func() {
 			songs := []agents.Song{
-				{Name: "Song A", Artist: "Artist"},
-				{Name: "Song A (Live)", Artist: "Artist"},
-				{Name: "Song B", Artist: "Artist"},
-				{Name: "Song B (Remix)", Artist: "Artist"},
+				{Name: "Song A", Artists: []agents.Artist{{Name: "Artist"}}},
+				{Name: "Song A (Live)", Artists: []agents.Artist{{Name: "Artist"}}},
+				{Name: "Song B", Artists: []agents.Artist{{Name: "Artist"}}},
+				{Name: "Song B (Remix)", Artists: []agents.Artist{{Name: "Artist"}}},
 			}
 			trackA := model.MediaFile{ID: "track-a", Title: "Song A", Artist: "Artist",
 				Participants: artistParticipants(model.Artist{ID: "art", Name: "Artist", OrderArtistName: "artist"}),
--- a/core/sonic/sonic_test.go
+++ b/core/sonic/sonic_test.go
@ -101,7 +101,7 @@ var _ = Describe("Sonic", func() {

 			provider := &mockProvider{
 				similarResults: []sonic.SimilarResult{
-					{Song: agents.Song{ID: "song-2", Name: "Similar Song", Artist: "Test Artist"}, Similarity: 0.85},
+					{Song: agents.Song{ID: "song-2", Name: "Similar Song", Artists: []agents.Artist{{Name: "Test Artist"}}}, Similarity: 0.85},
 				},
 			}
 			loader.names = []string{"test-plugin"}
--- a/plugins/metadata_agent.go
+++ b/plugins/metadata_agent.go
@ -227,26 +227,29 @@ func (a *MetadataAgent) GetSimilarSongsByArtist(ctx context.Context, id, name, m
 	return callSimilarSongsPluginFunction[capabilities.SimilarSongsByArtistRequest](ctx, a.plugin, FuncGetSimilarSongsByArtist, capabilities.SimilarSongsByArtistRequest{ID: id, Name: name, MBID: mbid, Count: int32(count)})
 }

-// songRefToAgentSong converts a single SongRef to agents.Song
+// songRefToAgentSong converts a single SongRef to agents.Song. SongRef keeps the single
+// Artist/ArtistMBID fields as part of the plugin wire contract; when a plugin sends those instead
+// of the artists array, they are folded into a one-element Artists list here.
 func songRefToAgentSong(s capabilities.SongRef) agents.Song {
 	var artists []agents.Artist
-	if len(s.Artists) > 0 {
+	switch {
+	case len(s.Artists) > 0:
 		artists = make([]agents.Artist, len(s.Artists))
 		for i, a := range s.Artists {
 			artists[i] = agents.Artist{ID: a.ID, Name: a.Name, MBID: a.MBID}
 		}
+	case s.Artist != "" || s.ArtistMBID != "":
+		artists = []agents.Artist{{Name: s.Artist, MBID: s.ArtistMBID}}
 	}
 	return agents.Song{
-		ID:         s.ID,
-		Name:       s.Name,
-		MBID:       s.MBID,
-		ISRC:       s.ISRC,
-		Artist:     s.Artist,
-		ArtistMBID: s.ArtistMBID,
-		Artists:    artists,
-		Album:      s.Album,
-		AlbumMBID:  s.AlbumMBID,
-		Duration:   uint32(s.Duration * 1000),
+		ID:        s.ID,
+		Name:      s.Name,
+		MBID:      s.MBID,
+		ISRC:      s.ISRC,
+		Artists:   artists,
+		Album:     s.Album,
+		AlbumMBID: s.AlbumMBID,
+		Duration:  uint32(s.Duration * 1000),
 	}
 }

--- a/plugins/metadata_agent_test.go
+++ b/plugins/metadata_agent_test.go
@ -119,7 +119,8 @@ var _ = Describe("MetadataAgent", Ordered, func() {
 			Expect(err).ToNot(HaveOccurred())
 			Expect(songs).To(HaveLen(3))
 			Expect(songs[0].Name).To(Equal("Similar to Yesterday #1"))
-			Expect(songs[0].Artist).To(Equal("The Beatles"))
+			Expect(songs[0].Artists).To(HaveLen(1))
+			Expect(songs[0].Artists[0].Name).To(Equal("The Beatles"))
 		})
 	})

@ -343,11 +344,18 @@ var _ = Describe("songRefToAgentSong multi-artist", func() {
 			{Name: "Future", MBID: "m-future"},
 		}))
 	})
-	It("leaves Artists nil and keeps the single Artist when no Artists provided", func() {
+	It("folds the single Artist/ArtistMBID into a one-element Artists when no Artists provided", func() {
 		ref := capabilities.SongRef{Name: "Solo", Artist: "Drake", ArtistMBID: "m-drake"}
 		got := songRefToAgentSong(ref)
+		Expect(got.Artists).To(Equal([]agents.Artist{{Name: "Drake", MBID: "m-drake"}}))
+	})
+	It("folds an MBID-only single artist (empty name) so the MBID is not dropped", func() {
+		ref := capabilities.SongRef{Name: "Solo", ArtistMBID: "m-drake"}
+		got := songRefToAgentSong(ref)
+		Expect(got.Artists).To(Equal([]agents.Artist{{MBID: "m-drake"}}))
+	})
+	It("leaves Artists nil when neither Artists nor the single Artist/ArtistMBID are provided", func() {
+		got := songRefToAgentSong(capabilities.SongRef{Name: "Anon"})
 		Expect(got.Artists).To(BeNil())
-		Expect(got.Artist).To(Equal("Drake"))
-		Expect(got.ArtistMBID).To(Equal("m-drake"))
 	})
 })
--- a/plugins/sonic_similarity_adapter_test.go
+++ b/plugins/sonic_similarity_adapter_test.go
@ -43,7 +43,8 @@ var _ = Describe("SonicSimilarityPlugin", Ordered, func() {
 			Expect(err).ToNot(HaveOccurred())
 			Expect(results).To(HaveLen(3))
 			Expect(results[0].Song.Name).To(Equal("Similar to Yesterday #1"))
-			Expect(results[0].Song.Artist).To(Equal("The Beatles"))
+			Expect(results[0].Song.Artists).To(HaveLen(1))
+			Expect(results[0].Song.Artists[0].Name).To(Equal("The Beatles"))
 			Expect(results[0].Similarity).To(Equal(1.0))
 			Expect(results[1].Similarity).To(Equal(0.9))
 			Expect(results[2].Similarity).To(Equal(0.8))
@ -68,7 +69,8 @@ var _ = Describe("SonicSimilarityPlugin", Ordered, func() {
 			Expect(err).ToNot(HaveOccurred())
 			Expect(results).To(HaveLen(3))
 			Expect(results[0].Song.Name).To(Equal("Path Yesterday to Tomorrow Never Knows #1"))
-			Expect(results[0].Song.Artist).To(Equal("The Beatles"))
+			Expect(results[0].Song.Artists).To(HaveLen(1))
+			Expect(results[0].Song.Artists[0].Name).To(Equal("The Beatles"))
 			Expect(results[0].Similarity).To(Equal(1.0))
 			Expect(results[1].Similarity).To(Equal(0.95))
 			Expect(results[2].Similarity).To(Equal(0.9))