fix: ListenBrainz similarity is stored relative to the seed's best, and the candidate arms keep tier order (#6177)

LB's similarity scores are counts (16 to 1445 for recordings, to 10,875
for artists), and they reached a scorer that reads similarity as 0 to 1.
One edge added 64 to 5,800 points under Songs-like, so likes, skips and
recency stopped mattering for any candidate with an edge.

- ResolveListenBrainzTrackEdges divides each edge by the seed's best
  score in its whole cached answer. The cache keeps the raw answer.
- The worker stores matched and unmatched artist rows over the seed's
  top artist.
- Migration 0096 rescales the rows already stored.
- The candidate arms hold sim_score bands so tier 1 stays above tier 2:
  lb_similar 0.5 + 0.5 x edge, tag_overlap halved, likes_overlap 0.3.
  Otherwise a seed's weaker LB edges fell below a shared genre tag.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/db/dbq/recommendation.sql.go

@@ -834,7 +834,7 @@ excluded_ids AS (
     WHERE q.user_id = $1
 ),
 lb_similar AS (
-    SELECT ts.track_b_id AS track_id, ts.score AS sim_score
+    SELECT ts.track_b_id AS track_id, 0.5 + 0.5 * ts.score AS sim_score
     FROM track_similarity ts
     WHERE ts.track_a_id = $2
       AND ts.source = 'listenbrainz'
@@ -864,8 +864,8 @@ similar_artists AS (
 ),
 tag_overlap AS (
     SELECT t.id AS track_id,
-           (count(DISTINCT trim(g))::float8
-            / GREATEST((SELECT count(*) FROM seed_tags), 1)) AS sim_score
+           0.5 * (count(DISTINCT trim(g))::float8
+                  / GREATEST((SELECT count(*) FROM seed_tags), 1)) AS sim_score
     FROM tracks t
     LEFT JOIN LATERAL regexp_split_to_table(coalesce(t.genre, ''), '[;,]') AS g_split(g) ON true
     WHERE trim(g_split.g) IN (SELECT tag FROM seed_tags)
@@ -877,7 +877,7 @@ tag_overlap AS (
     LIMIT $7
 ),
 likes_overlap AS (
-    SELECT gl.track_id, 0.6::float8 AS sim_score
+    SELECT gl.track_id, 0.3::float8 AS sim_score
     FROM general_likes gl
     WHERE gl.user_id = $1
       AND gl.track_id NOT IN (SELECT id FROM excluded_ids)
@@ -1025,6 +1025,20 @@ type LoadRadioCandidatesV2Row struct {
 // the determinism they promise; radio passes a fresh value per request and
 // keeps varying, which is what a radio should do.
 // Returns same shape as LoadRadioCandidates plus similarity_score column.
+//
+// sim_score BANDS keep the tiers in order (rule 131, #6177). Similarity edges
+// are stored relative to the seed's best match, 0 to 1, so the arms are placed
+// in bands rather than compared raw:
+//
+//	tier 1  lb_similar                      0.5 + 0.5 × edge   (0.5, 1.0]
+//	tier 2  similar_artists, coplay_artists 0.5 × edge         [0, 0.5]
+//	        tag_overlap                     0.5 × share of the seed's tags
+//	        likes_overlap                   0.3, flat
+//	tier 3  taste_overlap, random_fill      0
+//
+// Without the bands, the seed's weaker LB edges fell below a shared genre tag
+// and the flat likes score, and the one arm that measures the seed lost to
+// the ones that guess.
 func (q *Queries) LoadRadioCandidatesV2(ctx context.Context, arg LoadRadioCandidatesV2Params) ([]LoadRadioCandidatesV2Row, error) {
 	rows, err := q.db.Query(ctx, loadRadioCandidatesV2,
 		arg.UserID,

internal/db/dbq/similarity.sql.go

@@ -260,10 +260,19 @@ func (q *Queries) RecordTrackSimilarityFetch(ctx context.Context, arg RecordTrac
 }
 
 const resolveListenBrainzTrackEdges = `-- name: ResolveListenBrainzTrackEdges :exec
-WITH want AS (
+WITH best AS (
+    SELECT seed_track_id, max(score) AS score
+    FROM listenbrainz_similar_recordings
+    WHERE $1::uuid[] IS NULL
+       OR seed_track_id = ANY($1::uuid[])
+    GROUP BY seed_track_id
+),
+want AS (
     SELECT DISTINCT ON (c.seed_track_id, c.recording_mbid)
-           c.seed_track_id AS track_a_id, t.id AS track_b_id, c.score
+           c.seed_track_id AS track_a_id, t.id AS track_b_id,
+           CASE WHEN b.score > 0 THEN c.score / b.score ELSE 0 END AS score
     FROM listenbrainz_similar_recordings c
+    JOIN best b ON b.seed_track_id = c.seed_track_id
     JOIN tracks t ON t.mbid = c.recording_mbid
                  AND t.missing_since IS NULL
                  AND t.id <> c.seed_track_id
@@ -299,6 +308,13 @@ WHERE ts.source = 'listenbrainz'
 // pool would offer the same song twice. No cap per seed: LB's answer is already
 // at most 50.
 //
+// The score is RELATIVE: each edge's LB score over the seed's best score in its
+// whole cached answer, so 1.0 is the seed's closest recording and the rest fall
+// below it (#6177). LB's raw scores are counts (16 to 1445 on the operator's
+// library) and reached the scorer, which reads similarity as 0 to 1, so one
+// edge outweighed likes, skips and recency together. The cache keeps the raw
+// answer; only the edge is scaled.
+//
 // Only edges of seeds the cache owns are removed, those with a fetch row.
 // Edges written before the cache existed, or copied onto a survivor by a fold
 // (merge.sql), stay until their seed is fetched.

internal/db/migrations/0096_similarity_relative_scores.down.sql

@@ -0,0 +1,3 @@
+-- The raw scores are not kept for artists; the worker rewrites every seed with
+-- relative scores on its next fetch either way. Nothing to undo.
+SELECT 1;

internal/db/migrations/0096_similarity_relative_scores.up.sql

@@ -0,0 +1,51 @@
+-- #6177: ListenBrainz similarity scores were stored raw. They are counts (16 to
+-- 1445 for recordings, 16 to 10,875 for artists on the operator's library), and
+-- every reader treats similarity as 0 to 1. Rescale the stored rows relative to
+-- each seed's best score, as the worker now writes them.
+--
+-- A seed's best is taken over everything stored for it: the cached LB answer
+-- and its edges for tracks, matched and unmatched rows for artists. A seed
+-- whose best is already at most 1 is left alone, so a second run changes
+-- nothing.
+
+WITH best AS (
+    SELECT seed_id, max(score) AS score
+    FROM (
+        SELECT track_a_id AS seed_id, score FROM track_similarity WHERE source = 'listenbrainz'
+        UNION ALL
+        SELECT seed_track_id, score FROM listenbrainz_similar_recordings
+    ) s
+    GROUP BY seed_id
+)
+UPDATE track_similarity ts
+   SET score = ts.score / b.score
+  FROM best b
+ WHERE ts.source = 'listenbrainz'
+   AND ts.track_a_id = b.seed_id
+   AND b.score > 1;
+
+-- One statement, so both updates divide by the best as it stood before either.
+WITH best AS (
+    SELECT seed_id, max(score) AS score
+    FROM (
+        SELECT artist_a_id AS seed_id, score FROM artist_similarity WHERE source = 'listenbrainz'
+        UNION ALL
+        SELECT seed_artist_id, score FROM artist_similarity_unmatched WHERE source = 'listenbrainz'
+    ) s
+    GROUP BY seed_id
+),
+matched AS (
+    UPDATE artist_similarity a
+       SET score = a.score / b.score
+      FROM best b
+     WHERE a.source = 'listenbrainz'
+       AND a.artist_a_id = b.seed_id
+       AND b.score > 1
+    RETURNING 1
+)
+UPDATE artist_similarity_unmatched u
+   SET score = u.score / b.score
+  FROM best b
+ WHERE u.source = 'listenbrainz'
+   AND u.seed_artist_id = b.seed_id
+   AND b.score > 1;

internal/db/queries/recommendation.sql

@@ -62,6 +62,18 @@ WHERE t.id <> $2
 -- the determinism they promise; radio passes a fresh value per request and
 -- keeps varying, which is what a radio should do.
 -- Returns same shape as LoadRadioCandidates plus similarity_score column.
+--
+-- sim_score BANDS keep the tiers in order (rule 131, #6177). Similarity edges
+-- are stored relative to the seed's best match, 0 to 1, so the arms are placed
+-- in bands rather than compared raw:
+--   tier 1  lb_similar                      0.5 + 0.5 × edge   (0.5, 1.0]
+--   tier 2  similar_artists, coplay_artists 0.5 × edge         [0, 0.5]
+--           tag_overlap                     0.5 × share of the seed's tags
+--           likes_overlap                   0.3, flat
+--   tier 3  taste_overlap, random_fill      0
+-- Without the bands, the seed's weaker LB edges fell below a shared genre tag
+-- and the flat likes score, and the one arm that measures the seed lost to
+-- the ones that guess.
 
 WITH
 seed_artist AS (
@@ -87,7 +99,7 @@ excluded_ids AS (
     WHERE q.user_id = $1
 ),
 lb_similar AS (
-    SELECT ts.track_b_id AS track_id, ts.score AS sim_score
+    SELECT ts.track_b_id AS track_id, 0.5 + 0.5 * ts.score AS sim_score
     FROM track_similarity ts
     WHERE ts.track_a_id = $2
       AND ts.source = 'listenbrainz'
@@ -117,8 +129,8 @@ similar_artists AS (
 ),
 tag_overlap AS (
     SELECT t.id AS track_id,
-           (count(DISTINCT trim(g))::float8
-            / GREATEST((SELECT count(*) FROM seed_tags), 1)) AS sim_score
+           0.5 * (count(DISTINCT trim(g))::float8
+                  / GREATEST((SELECT count(*) FROM seed_tags), 1)) AS sim_score
     FROM tracks t
     LEFT JOIN LATERAL regexp_split_to_table(coalesce(t.genre, ''), '[;,]') AS g_split(g) ON true
     WHERE trim(g_split.g) IN (SELECT tag FROM seed_tags)
@@ -130,7 +142,7 @@ tag_overlap AS (
     LIMIT $7
 ),
 likes_overlap AS (
-    SELECT gl.track_id, 0.6::float8 AS sim_score
+    SELECT gl.track_id, 0.3::float8 AS sim_score
     FROM general_likes gl
     WHERE gl.user_id = $1
       AND gl.track_id NOT IN (SELECT id FROM excluded_ids)

internal/db/queries/similarity.sql

@@ -68,13 +68,29 @@ ON CONFLICT (artist_id) DO UPDATE SET fetched_at = now(), returned = EXCLUDED.re
 -- pool would offer the same song twice. No cap per seed: LB's answer is already
 -- at most 50.
 --
+-- The score is RELATIVE: each edge's LB score over the seed's best score in its
+-- whole cached answer, so 1.0 is the seed's closest recording and the rest fall
+-- below it (#6177). LB's raw scores are counts (16 to 1445 on the operator's
+-- library) and reached the scorer, which reads similarity as 0 to 1, so one
+-- edge outweighed likes, skips and recency together. The cache keeps the raw
+-- answer; only the edge is scaled.
+--
 -- Only edges of seeds the cache owns are removed, those with a fetch row.
 -- Edges written before the cache existed, or copied onto a survivor by a fold
 -- (merge.sql), stay until their seed is fetched.
-WITH want AS (
+WITH best AS (
+    SELECT seed_track_id, max(score) AS score
+    FROM listenbrainz_similar_recordings
+    WHERE sqlc.narg(seed_ids)::uuid[] IS NULL
+       OR seed_track_id = ANY(sqlc.narg(seed_ids)::uuid[])
+    GROUP BY seed_track_id
+),
+want AS (
     SELECT DISTINCT ON (c.seed_track_id, c.recording_mbid)
-           c.seed_track_id AS track_a_id, t.id AS track_b_id, c.score
+           c.seed_track_id AS track_a_id, t.id AS track_b_id,
+           CASE WHEN b.score > 0 THEN c.score / b.score ELSE 0 END AS score
     FROM listenbrainz_similar_recordings c
+    JOIN best b ON b.seed_track_id = c.seed_track_id
     JOIN tracks t ON t.mbid = c.recording_mbid
                  AND t.missing_since IS NULL
                  AND t.id <> c.seed_track_id

internal/recommendation/candidates.go

@@ -127,8 +127,9 @@ func DefaultCandidateSourceLimits() CandidateSourceLimits {
 //	tier 3  taste_overlap, random_fill
 //	                        seed-independent. The floor, and nothing more.
 //
-// The tiering is enforced by SCORE rather than by a fallback ladder: tier-3
-// arms carry sim_score 0, so under SongsLike weights (SimilarityWeight 4.0,
+// The tiering is enforced by SCORE rather than by a fallback ladder: each tier
+// holds its own sim_score band (recommendation.sql; tier 1 above 0.5, tier 2
+// at or below it, #6177), and tier-3 arms carry sim_score 0, so under SongsLike weights (SimilarityWeight 4.0,
 // everything seed-independent demoted) they rank below any real match and
 // surface only when tiers 1–2 cannot fill the mix. That is the rule's
 // "fill from tier 1 first, reach down only when a tier cannot fill".
@@ -159,19 +160,19 @@ func DefaultCandidateSourceLimits() CandidateSourceLimits {
 // surface only when the closer tiers cannot fill the mix.
 //
 // likes_overlap is cut hardest of the tier-2 arms for a specific reason: its
-// SQL assigns a FLAT 0.6 sim_score (recommendation.sql) rather than measuring
+// SQL assigns a FLAT 0.3 sim_score (recommendation.sql) rather than measuring
 // anything. It is a collaborative signal wearing similarity's clothes, and a
-// raised SimilarityWeight amplifies it — if real ListenBrainz scores commonly
-// land below 0.6 it would outrank genuine matches. Halved pending the
-// fill-rate measurement in #3879; the honest fix is to stop it claiming a
-// similarity score it never computed.
+// raised SimilarityWeight amplifies it. The tier bands keep it below every
+// ListenBrainz match (#6177); halved pending the fill-rate measurement in
+// #3879, and the honest fix is still to stop it claiming a similarity score
+// it never computed.
 func SongsLikeCandidateSourceLimits() CandidateSourceLimits {
 	return CandidateSourceLimits{
 		LBSimilar:     60, // tier 1 — doubled; the only arm that measures the seed
 		SimilarArtist: 40, // tier 2 — raised; growing is always safe
 		TagOverlap:    20, // tier 2
 		UserCoplay:    20, // tier 2
-		LikesOverlap:  10, // tier 2, halved — flat 0.6 sim_score, see above
+		LikesOverlap:  10, // tier 2, halved — flat 0.3 sim_score, see above
 		TasteOverlap:  10, // tier 3 floor — halved, not removed
 		RandomFill:    10, // tier 3 floor — cut hard, never to zero
 	}

internal/recommendation/candidates_v2_test.go

@@ -69,8 +69,9 @@ func TestLoadCandidatesFromSimilarity_LBSimilarSourceContributes(t *testing.T) {
 	if found == nil {
 		t.Fatal("LB-similar target missing from candidates")
 	}
-	if found.Inputs.SimilarityScore < 0.84 || found.Inputs.SimilarityScore > 0.86 {
-		t.Errorf("LB-similar SimilarityScore = %v, want ~0.85", found.Inputs.SimilarityScore)
+	// Tier 1's band (#6177): 0.5 + 0.5 × 0.85.
+	if found.Inputs.SimilarityScore < 0.92 || found.Inputs.SimilarityScore > 0.93 {
+		t.Errorf("LB-similar SimilarityScore = %v, want ~0.925 (0.5 + 0.5 × 0.85)", found.Inputs.SimilarityScore)
 	}
 }
 
@@ -117,9 +118,9 @@ func TestLoadCandidatesFromSimilarity_TagOverlapContributes(t *testing.T) {
 	}
 	for _, c := range got {
 		if c.Track.ID == target.ID {
-			// Seed has 2 tags; target shares 1 → jaccard 1/2 = 0.5.
-			if c.Inputs.SimilarityScore < 0.49 || c.Inputs.SimilarityScore > 0.51 {
-				t.Errorf("tag-overlap SimilarityScore = %v, want ~0.5", c.Inputs.SimilarityScore)
+			// Seed has 2 tags; target shares 1 → 1/2, in tier 2's band → 0.25.
+			if c.Inputs.SimilarityScore < 0.24 || c.Inputs.SimilarityScore > 0.26 {
+				t.Errorf("tag-overlap SimilarityScore = %v, want ~0.25 (0.5 × 1/2)", c.Inputs.SimilarityScore)
 			}
 			return
 		}
@@ -144,10 +145,10 @@ func TestLoadCandidatesFromSimilarity_LikesOverlapContributes(t *testing.T) {
 	}
 	for _, c := range got {
 		if c.Track.ID == liked.ID {
-			// Both tracks tagged "Rock" → jaccard 1/1 = 1.0 from tag-overlap.
-			// likes-overlap = 0.6. Max wins = 1.0.
-			if c.Inputs.SimilarityScore < 0.59 {
-				t.Errorf("likes-overlap candidate SimilarityScore = %v, want ≥ 0.6", c.Inputs.SimilarityScore)
+			// Both tracks tagged "Rock" → 0.5 × 1/1 = 0.5 from tag-overlap.
+			// likes-overlap = 0.3. Max wins = 0.5.
+			if c.Inputs.SimilarityScore < 0.29 {
+				t.Errorf("likes-overlap candidate SimilarityScore = %v, want ≥ 0.3", c.Inputs.SimilarityScore)
 			}
 			return
 		}
@@ -243,8 +244,8 @@ func TestLoadCandidatesFromSimilarity_DedupTakesMaxScore(t *testing.T) {
 	seed := f.tracks[0]
 	target := f.tracks[1]
 	helperSetTrackGenre(t, f, seed.ID, "Rock")
-	helperSetTrackGenre(t, f, target.ID, "Rock")      // jaccard 1/1 = 1.0 from tag-overlap
-	helperLBSimilarity(t, f, seed.ID, target.ID, 0.5) // weaker LB signal
+	helperSetTrackGenre(t, f, target.ID, "Rock")      // 0.5 × 1/1 = 0.5 from tag-overlap
+	helperLBSimilarity(t, f, seed.ID, target.ID, 0.1) // a weak LB edge → 0.5 + 0.05
 	got, err := LoadCandidatesFromSimilarity(
 		context.Background(), f.q, f.user, seed.ID, 1, SessionVector{Seed: true}, nil, defaultLimits(), "test-seed",
 	)
@@ -255,9 +256,10 @@ func TestLoadCandidatesFromSimilarity_DedupTakesMaxScore(t *testing.T) {
 	for _, c := range got {
 		if c.Track.ID == target.ID {
 			count++
-			// tag-overlap (1.0) wins over LB (0.5) per max() — expect ≥ 0.99
-			if c.Inputs.SimilarityScore < 0.99 {
-				t.Errorf("dedup max SimilarityScore = %v, want ≥ 0.99 (tag-overlap should win)", c.Inputs.SimilarityScore)
+			// max() keeps LB's 0.55. Even a weak ListenBrainz edge is tier 1 and
+			// outranks a full tag match (#6177).
+			if c.Inputs.SimilarityScore < 0.54 || c.Inputs.SimilarityScore > 0.56 {
+				t.Errorf("dedup max SimilarityScore = %v, want ~0.55 (the LB edge's band should win)", c.Inputs.SimilarityScore)
 			}
 		}
 	}

internal/recsettings/service.go

@@ -136,7 +136,7 @@ func ShippedDailyMixWeights() recommendation.ScoringWeights {
 // admin tuning card and good values get baked back here. They are a
 // defensible starting point rather than a measured optimum: the per-arm fill
 // rates and the real sim_score distribution are still unknown (#3879), and
-// `likes_overlap` contributes a flat 0.6 that a high SimilarityWeight
+// `likes_overlap` contributes a flat 0.3 that a high SimilarityWeight
 // amplifies. Expect to move these once that lands.
 func ShippedSongsLikeWeights() recommendation.ScoringWeights {
 	return recommendation.ScoringWeights{

internal/similarity/worker.go

@@ -199,6 +199,10 @@ func (w *Worker) upsertArtistSimilar(ctx context.Context, q *dbq.Queries, artist
 		return
 	}
 	sort.Slice(results, func(i, j int) bool { return results[i].Score > results[j].Score })
+	// Scores are stored relative to the seed's closest artist, as track edges
+	// are (#6177): LB's raw scores are counts (16 to 10,875 on the operator's
+	// library), and both the candidate pool and the suggestions read 0 to 1.
+	best := results[0].Score
 
 	mbids := make([]string, 0, len(results))
 	for _, r := range results {
@@ -230,7 +234,7 @@ func (w *Worker) upsertArtistSimilar(ctx context.Context, q *dbq.Queries, artist
 			continue
 		}
 		if uerr := q.UpsertArtistSimilarity(ctx, dbq.UpsertArtistSimilarityParams{
-			ArtistAID: artistAID, ArtistBID: localID, Score: r.Score,
+			ArtistAID: artistAID, ArtistBID: localID, Score: relativeScore(r.Score, best),
 		}); uerr != nil {
 			w.logger.Warn("similarity: UpsertArtistSimilarity", "err", uerr)
 			continue
@@ -257,7 +261,7 @@ func (w *Worker) upsertArtistSimilar(ctx context.Context, q *dbq.Queries, artist
 			SeedArtistID:  artistAID,
 			CandidateMbid: r.MBID,
 			CandidateName: r.Name,
-			Score:         r.Score,
+			Score:         relativeScore(r.Score, best),
 			Source:        "listenbrainz",
 		}); uerr != nil {
 			w.logger.Warn("similarity: UpsertArtistSimilarityUnmatched", "err", uerr)
@@ -266,3 +270,12 @@ func (w *Worker) upsertArtistSimilar(ctx context.Context, q *dbq.Queries, artist
 		takenUnmatched++
 	}
 }
+
+// relativeScore is score over the seed's best, in [0, 1]; 0 when the seed has
+// no positive score to measure against.
+func relativeScore(score, best float64) float64 {
+	if best <= 0 {
+		return 0
+	}
+	return score / best
+}

internal/similarity/worker_integration_test.go

@@ -209,6 +209,38 @@ func TestTickOnce_MapsLBResponseToLocalLibrary(t *testing.T) {
 	}
 }
 
+// LB's scores are counts, not 0 to 1 (16 to 1445 on the operator's library).
+// An edge is stored over the seed's best score in the whole answer, in the
+// library or not, so the scorer reads it as 0 to 1 (#6177).
+func TestTickOnce_EdgeIsRelativeToTheSeedsBest(t *testing.T) {
+	f := newFixture(t)
+	mbidA := "11111111-1111-1111-1111-111111111111"
+	mbidB := "22222222-2222-2222-2222-222222222222"
+	mbidC := "99999999-9999-9999-9999-999999999999" // NOT in library
+	trackA := seedTrack(t, f, "A", &mbidA)
+	trackB := seedTrack(t, f, "B", &mbidB)
+	markPlayed(t, f, trackA.ID)
+	body := `[
+		{"recording_mbid": "` + mbidC + `", "score": 1445},
+		{"recording_mbid": "` + mbidB + `", "score": 289}
+	]`
+	srv := stubLB(body, `[]`, http.StatusOK)
+	defer srv.Close()
+	w := newTestWorker(f, srv.URL)
+	if err := w.tickOnce(context.Background()); err != nil {
+		t.Fatalf("tickOnce: %v", err)
+	}
+	var score float64
+	if err := f.pool.QueryRow(context.Background(),
+		`SELECT score FROM track_similarity WHERE track_a_id = $1 AND track_b_id = $2 AND source = 'listenbrainz'`,
+		trackA.ID, trackB.ID).Scan(&score); err != nil {
+		t.Fatalf("edge: %v", err)
+	}
+	if score != 0.2 {
+		t.Errorf("score = %v, want 0.2 (289 over the seed's best, 1445)", score)
+	}
+}
+
 // The 20-per-seed cap is gone with the cache (#5296): LB's answer is at most
 // 50, and every recording of it that is in the library becomes an edge.
 func TestTickOnce_KeepsEveryInLibraryMatch(t *testing.T) {
@@ -279,8 +311,9 @@ func TestTickOnce_RefreshesStaleRow(t *testing.T) {
 	_ = f.pool.QueryRow(context.Background(),
 		`SELECT score, fetched_at FROM track_similarity WHERE track_a_id = $1 AND track_b_id = $2 AND source = 'listenbrainz'`,
 		trackA.ID, other.ID).Scan(&score, &fetchedAt)
-	if score != 0.95 {
-		t.Errorf("score = %v, want 0.95 (refreshed)", score)
+	// The seed's only answer is its best, so the refreshed edge is 1.0 (#6177).
+	if score != 1.0 {
+		t.Errorf("score = %v, want 1.0 (refreshed, relative to the seed's best)", score)
 	}
 	if time.Since(fetchedAt) > time.Minute {
 		t.Errorf("fetched_at not bumped: %v ago", time.Since(fetchedAt))
@@ -419,11 +452,12 @@ func TestUpsertArtistSimilar_PersistsUnmatchedToTable(t *testing.T) {
 	w := newTestWorker(f, "")
 
 	similars := []listenbrainz.SimilarArtist{
-		{MBID: inLibMBID, Name: "InLib Artist", Score: 0.95},
-		{MBID: "out-mbid-1", Name: "Outsider One", Score: 0.85},
-		{MBID: "out-mbid-2", Name: "Outsider Two", Score: 0.80},
-		{MBID: "out-mbid-3", Name: "Outsider Three", Score: 0.70},
-		{MBID: "out-mbid-4", Name: "", Score: 0.60}, // empty name — skipped
+		// LB's scores are counts; rows are stored over the seed's best (#6177).
+		{MBID: inLibMBID, Name: "InLib Artist", Score: 1000},
+		{MBID: "out-mbid-1", Name: "Outsider One", Score: 850},
+		{MBID: "out-mbid-2", Name: "Outsider Two", Score: 800},
+		{MBID: "out-mbid-3", Name: "Outsider Three", Score: 700},
+		{MBID: "out-mbid-4", Name: "", Score: 600}, // empty name — skipped
 	}
 	w.upsertArtistSimilar(ctx, f.q, f.artist.ID, similars)
 
@@ -438,6 +472,16 @@ func TestUpsertArtistSimilar_PersistsUnmatchedToTable(t *testing.T) {
 	if matchedCount != 1 {
 		t.Errorf("artist_similarity rows = %d, want 1 (only the in-library match)", matchedCount)
 	}
+	var matchedScore float64
+	if err := f.pool.QueryRow(ctx,
+		"SELECT score FROM artist_similarity WHERE artist_a_id = $1 AND artist_b_id = $2",
+		f.artist.ID, inLibArtist.ID,
+	).Scan(&matchedScore); err != nil {
+		t.Fatalf("fetch matched score: %v", err)
+	}
+	if matchedScore != 1.0 {
+		t.Errorf("matched score = %v, want 1.0 (the seed's best)", matchedScore)
+	}
 
 	// Unmatched path: 3 rows (out-mbid-1/2/3); the empty-name row is skipped.
 	var unmatchedCount int
@@ -464,7 +508,6 @@ func TestUpsertArtistSimilar_PersistsUnmatchedToTable(t *testing.T) {
 		t.Errorf("row = (%q, %v), want (Outsider One, 0.85)", name, score)
 	}
 
-	_ = inLibArtist
 }
 
 // recordFetch stamps a seed as answered by ListenBrainz at the given SQL time.