Merge PR #91: "You might like" rows + taste profile (learn + apply)

internal/api/home.go

@@ -30,6 +30,8 @@ func (h *handlers) handleGetHome(w http.ResponseWriter, r *http.Request) {
 		RediscoverArtists:   make([]ArtistRef, 0, len(data.RediscoverArtists)),
 		MostPlayedTracks:    make([]TrackRef, 0, len(data.MostPlayedTracks)),
 		LastPlayedArtists:   make([]ArtistRef, 0, len(data.LastPlayedArtists)),
+		YouMightLikeAlbums:  make([]AlbumRef, 0, len(data.YouMightLikeAlbums)),
+		YouMightLikeArtists: make([]ArtistRef, 0, len(data.YouMightLikeArtists)),
 	}
 	for _, row := range data.RecentlyAddedAlbums {
 		out.RecentlyAddedAlbums = append(out.RecentlyAddedAlbums, albumRefFrom(row.Album, row.ArtistName, 0, 0))
@@ -46,6 +48,12 @@ func (h *handlers) handleGetHome(w http.ResponseWriter, r *http.Request) {
 	for _, row := range data.LastPlayedArtists {
 		out.LastPlayedArtists = append(out.LastPlayedArtists, artistRefFromCovered(row.Artist, int(row.AlbumCount), row.CoverAlbumID))
 	}
+	for _, row := range data.YouMightLikeAlbums {
+		out.YouMightLikeAlbums = append(out.YouMightLikeAlbums, albumRefFrom(row.Album, row.ArtistName, 0, 0))
+	}
+	for _, row := range data.YouMightLikeArtists {
+		out.YouMightLikeArtists = append(out.YouMightLikeArtists, artistRefFromCovered(row.Artist, int(row.AlbumCount), row.CoverAlbumID))
+	}
 	writeJSON(w, http.StatusOK, out)
 }
 
@@ -78,6 +86,8 @@ func (h *handlers) handleGetHomeIndex(w http.ResponseWriter, r *http.Request) {
 		RediscoverArtists:   make([]string, 0, len(data.RediscoverArtists)),
 		MostPlayedTracks:    make([]string, 0, len(data.MostPlayedTracks)),
 		LastPlayedArtists:   make([]string, 0, len(data.LastPlayedArtists)),
+		YouMightLikeAlbums:  make([]string, 0, len(data.YouMightLikeAlbums)),
+		YouMightLikeArtists: make([]string, 0, len(data.YouMightLikeArtists)),
 	}
 	for _, row := range data.RecentlyAddedAlbums {
 		out.RecentlyAddedAlbums = append(out.RecentlyAddedAlbums, uuidToString(row.Album.ID))
@@ -94,6 +104,12 @@ func (h *handlers) handleGetHomeIndex(w http.ResponseWriter, r *http.Request) {
 	for _, row := range data.LastPlayedArtists {
 		out.LastPlayedArtists = append(out.LastPlayedArtists, uuidToString(row.Artist.ID))
 	}
+	for _, row := range data.YouMightLikeAlbums {
+		out.YouMightLikeAlbums = append(out.YouMightLikeAlbums, uuidToString(row.Album.ID))
+	}
+	for _, row := range data.YouMightLikeArtists {
+		out.YouMightLikeArtists = append(out.YouMightLikeArtists, uuidToString(row.Artist.ID))
+	}
 	writeJSON(w, http.StatusOK, out)
 }
 

internal/api/radio.go

@@ -108,6 +108,7 @@ func (h *handlers) handleRadio(w http.ResponseWriter, r *http.Request) {
 		JitterMagnitude:  h.recCfg.JitterMagnitude,
 		ContextWeight:    h.recCfg.ContextWeight,
 		SimilarityWeight: h.recCfg.SimilarityWeight,
+		TasteWeight:      h.recCfg.TasteWeight,
 	}
 	picks := recommendation.Shuffle(candidates, weights, time.Now().UTC(), h.rng, limit-1)
 

internal/api/types.go

@@ -116,6 +116,11 @@ type HomePayload struct {
 	RediscoverArtists   []ArtistRef `json:"rediscover_artists"`
 	MostPlayedTracks    []TrackRef  `json:"most_played_tracks"`
 	LastPlayedArtists   []ArtistRef `json:"last_played_artists"`
+	// You-might-like: in-library albums/artists predicted from the user's
+	// listening that they don't actively spin. Built daily; gated on a
+	// minimum listening history so a thin profile gets empty rows.
+	YouMightLikeAlbums  []AlbumRef  `json:"you_might_like_albums"`
+	YouMightLikeArtists []ArtistRef `json:"you_might_like_artists"`
 }
 
 // HomeIndexPayload is the response body of GET /api/home/index — the
@@ -134,6 +139,8 @@ type HomeIndexPayload struct {
 	RediscoverArtists   []string `json:"rediscover_artists"`
 	MostPlayedTracks    []string `json:"most_played_tracks"`
 	LastPlayedArtists   []string `json:"last_played_artists"`
+	YouMightLikeAlbums  []string `json:"you_might_like_albums"`
+	YouMightLikeArtists []string `json:"you_might_like_artists"`
 }
 
 // HistoryEvent is one play in a user's listening history. Used by

internal/config/config.go

@@ -98,6 +98,7 @@ type RecommendationConfig struct {
 	JitterMagnitude     float64 `yaml:"jitter_magnitude"`
 	ContextWeight       float64 `yaml:"context_weight"`
 	SimilarityWeight    float64 `yaml:"similarity_weight"`
+	TasteWeight         float64 `yaml:"taste_weight"`
 	RecentlyPlayedHours int     `yaml:"recently_played_hours"`
 	RadioSize           int     `yaml:"radio_size"`
 	RadioSizeMax        int     `yaml:"radio_size_max"`
@@ -119,13 +120,16 @@ func Default() Config {
 			SkipMaxDurationPlayedMs: 30000,
 		},
 		Recommendation: RecommendationConfig{
-			BaseWeight:          1.0,
-			LikeBoost:           2.0,
-			RecencyWeight:       1.0,
-			SkipPenalty:         1.0,
-			JitterMagnitude:     0.1,
-			ContextWeight:       2.0,
-			SimilarityWeight:    2.0,
+			BaseWeight:       1.0,
+			LikeBoost:        2.0,
+			RecencyWeight:    1.0,
+			SkipPenalty:      1.0,
+			JitterMagnitude:  0.1,
+			ContextWeight:    2.0,
+			SimilarityWeight: 2.0,
+			// Radio is seed-directed (the user picked a direction), so taste
+			// is a lighter nudge here than in the daily mixes (1.5).
+			TasteWeight:         1.0,
 			RecentlyPlayedHours: 1,
 			RadioSize:           50,
 			RadioSizeMax:        200,

internal/db/dbq/models.go

@@ -497,6 +497,20 @@ type SystemPlaylistRun struct {
 	LastError   *string
 }
 
+type TasteProfileArtist struct {
+	UserID    pgtype.UUID
+	ArtistID  pgtype.UUID
+	Weight    float64
+	UpdatedAt pgtype.Timestamptz
+}
+
+type TasteProfileTag struct {
+	UserID    pgtype.UUID
+	Tag       string
+	Weight    float64
+	UpdatedAt pgtype.Timestamptz
+}
+
 type Track struct {
 	ID          pgtype.UUID
 	Title       string
@@ -549,3 +563,17 @@ type UserInvite struct {
 	RedeemedAt pgtype.Timestamptz
 	RedeemedBy pgtype.UUID
 }
+
+type YouMightLikeAlbum struct {
+	UserID  pgtype.UUID
+	AlbumID pgtype.UUID
+	Rank    int32
+	BuiltAt pgtype.Timestamptz
+}
+
+type YouMightLikeArtist struct {
+	UserID   pgtype.UUID
+	ArtistID pgtype.UUID
+	Rank     int32
+	BuiltAt  pgtype.Timestamptz
+}

internal/db/dbq/taste_profile.sql.go

@@ -0,0 +1,262 @@
+// Code generated by sqlc. DO NOT EDIT.
+// versions:
+//   sqlc v1.31.1
+// source: taste_profile.sql
+
+package dbq
+
+import (
+	"context"
+
+	"github.com/jackc/pgx/v5/pgtype"
+)
+
+const deleteTasteProfileArtistsForUser = `-- name: DeleteTasteProfileArtistsForUser :exec
+DELETE FROM taste_profile_artists WHERE user_id = $1
+`
+
+func (q *Queries) DeleteTasteProfileArtistsForUser(ctx context.Context, userID pgtype.UUID) error {
+	_, err := q.db.Exec(ctx, deleteTasteProfileArtistsForUser, userID)
+	return err
+}
+
+const deleteTasteProfileTagsForUser = `-- name: DeleteTasteProfileTagsForUser :exec
+DELETE FROM taste_profile_tags WHERE user_id = $1
+`
+
+func (q *Queries) DeleteTasteProfileTagsForUser(ctx context.Context, userID pgtype.UUID) error {
+	_, err := q.db.Exec(ctx, deleteTasteProfileTagsForUser, userID)
+	return err
+}
+
+const insertTasteProfileArtist = `-- name: InsertTasteProfileArtist :exec
+INSERT INTO taste_profile_artists (user_id, artist_id, weight)
+VALUES ($1, $2, $3)
+`
+
+type InsertTasteProfileArtistParams struct {
+	UserID   pgtype.UUID
+	ArtistID pgtype.UUID
+	Weight   float64
+}
+
+func (q *Queries) InsertTasteProfileArtist(ctx context.Context, arg InsertTasteProfileArtistParams) error {
+	_, err := q.db.Exec(ctx, insertTasteProfileArtist, arg.UserID, arg.ArtistID, arg.Weight)
+	return err
+}
+
+const insertTasteProfileTag = `-- name: InsertTasteProfileTag :exec
+INSERT INTO taste_profile_tags (user_id, tag, weight)
+VALUES ($1, $2, $3)
+`
+
+type InsertTasteProfileTagParams struct {
+	UserID pgtype.UUID
+	Tag    string
+	Weight float64
+}
+
+func (q *Queries) InsertTasteProfileTag(ctx context.Context, arg InsertTasteProfileTagParams) error {
+	_, err := q.db.Exec(ctx, insertTasteProfileTag, arg.UserID, arg.Tag, arg.Weight)
+	return err
+}
+
+const listLikedArtistIDsForUser = `-- name: ListLikedArtistIDsForUser :many
+SELECT artist_id FROM general_likes_artists WHERE user_id = $1
+`
+
+// Artists the user has explicitly liked; feeds the artist-like bonus.
+func (q *Queries) ListLikedArtistIDsForUser(ctx context.Context, userID pgtype.UUID) ([]pgtype.UUID, error) {
+	rows, err := q.db.Query(ctx, listLikedArtistIDsForUser, userID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var items []pgtype.UUID
+	for rows.Next() {
+		var artist_id pgtype.UUID
+		if err := rows.Scan(&artist_id); err != nil {
+			return nil, err
+		}
+		items = append(items, artist_id)
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return items, nil
+}
+
+const listLikedTrackTasteInputsForUser = `-- name: ListLikedTrackTasteInputsForUser :many
+SELECT t.artist_id, t.genre
+FROM general_likes gl
+JOIN tracks t ON t.id = gl.track_id
+WHERE gl.user_id = $1
+`
+
+type ListLikedTrackTasteInputsForUserRow struct {
+	ArtistID pgtype.UUID
+	Genre    *string
+}
+
+// (artist_id, genre) for each track the user has explicitly liked. Feeds the
+// track-like bonus into the liked track's artist and tags.
+func (q *Queries) ListLikedTrackTasteInputsForUser(ctx context.Context, userID pgtype.UUID) ([]ListLikedTrackTasteInputsForUserRow, error) {
+	rows, err := q.db.Query(ctx, listLikedTrackTasteInputsForUser, userID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var items []ListLikedTrackTasteInputsForUserRow
+	for rows.Next() {
+		var i ListLikedTrackTasteInputsForUserRow
+		if err := rows.Scan(&i.ArtistID, &i.Genre); err != nil {
+			return nil, err
+		}
+		items = append(items, i)
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return items, nil
+}
+
+const listPlayEngagementInputsForUser = `-- name: ListPlayEngagementInputsForUser :many
+
+SELECT
+    t.artist_id,
+    t.genre,
+    LEAST(GREATEST(
+        COALESCE(pe.completion_ratio,
+                 pe.duration_played_ms::float8 / NULLIF(t.duration_ms, 0),
+                 0), 0), 1)::float8 AS completion,
+    (EXTRACT(epoch FROM now() - pe.started_at) / 86400.0)::float8 AS age_days
+FROM play_events pe
+JOIN tracks t ON t.id = pe.track_id
+WHERE pe.user_id = $1
+  AND pe.started_at > now() - ($2::float8 * INTERVAL '1 day')
+  AND NOT EXISTS (
+      SELECT 1 FROM lidarr_quarantine q
+      WHERE q.user_id = $1 AND q.track_id = t.id
+  )
+`
+
+type ListPlayEngagementInputsForUserParams struct {
+	UserID  pgtype.UUID
+	Column2 float64
+}
+
+type ListPlayEngagementInputsForUserRow struct {
+	ArtistID   pgtype.UUID
+	Genre      *string
+	Completion float64
+	AgeDays    float64
+}
+
+// Taste profile (#796 phase 1). The daily build computes signed artist/tag
+// weights in Go (graded engagement + decay + like bonus) and atomic-replaces
+// them here. Read queries serve "top taste" lookups (used in phase 2).
+// One row per play in the decay-relevant window. completion is the play's
+// completion ratio (precomputed column when present, else duration_played /
+// track duration, clamped to [0,1]); age_days drives the time-decay. Genre
+// is split into tags in Go. Quarantined tracks are excluded.
+func (q *Queries) ListPlayEngagementInputsForUser(ctx context.Context, arg ListPlayEngagementInputsForUserParams) ([]ListPlayEngagementInputsForUserRow, error) {
+	rows, err := q.db.Query(ctx, listPlayEngagementInputsForUser, arg.UserID, arg.Column2)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var items []ListPlayEngagementInputsForUserRow
+	for rows.Next() {
+		var i ListPlayEngagementInputsForUserRow
+		if err := rows.Scan(
+			&i.ArtistID,
+			&i.Genre,
+			&i.Completion,
+			&i.AgeDays,
+		); err != nil {
+			return nil, err
+		}
+		items = append(items, i)
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return items, nil
+}
+
+const listTasteProfileArtistsForUser = `-- name: ListTasteProfileArtistsForUser :many
+SELECT artist_id, weight
+FROM taste_profile_artists
+WHERE user_id = $1
+ORDER BY weight DESC
+LIMIT $2
+`
+
+type ListTasteProfileArtistsForUserParams struct {
+	UserID pgtype.UUID
+	Limit  int32
+}
+
+type ListTasteProfileArtistsForUserRow struct {
+	ArtistID pgtype.UUID
+	Weight   float64
+}
+
+// Top-weighted taste artists (phase-2 consumption + tests).
+func (q *Queries) ListTasteProfileArtistsForUser(ctx context.Context, arg ListTasteProfileArtistsForUserParams) ([]ListTasteProfileArtistsForUserRow, error) {
+	rows, err := q.db.Query(ctx, listTasteProfileArtistsForUser, arg.UserID, arg.Limit)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var items []ListTasteProfileArtistsForUserRow
+	for rows.Next() {
+		var i ListTasteProfileArtistsForUserRow
+		if err := rows.Scan(&i.ArtistID, &i.Weight); err != nil {
+			return nil, err
+		}
+		items = append(items, i)
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return items, nil
+}
+
+const listTasteProfileTagsForUser = `-- name: ListTasteProfileTagsForUser :many
+SELECT tag, weight
+FROM taste_profile_tags
+WHERE user_id = $1
+ORDER BY weight DESC
+LIMIT $2
+`
+
+type ListTasteProfileTagsForUserParams struct {
+	UserID pgtype.UUID
+	Limit  int32
+}
+
+type ListTasteProfileTagsForUserRow struct {
+	Tag    string
+	Weight float64
+}
+
+func (q *Queries) ListTasteProfileTagsForUser(ctx context.Context, arg ListTasteProfileTagsForUserParams) ([]ListTasteProfileTagsForUserRow, error) {
+	rows, err := q.db.Query(ctx, listTasteProfileTagsForUser, arg.UserID, arg.Limit)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var items []ListTasteProfileTagsForUserRow
+	for rows.Next() {
+		var i ListTasteProfileTagsForUserRow
+		if err := rows.Scan(&i.Tag, &i.Weight); err != nil {
+			return nil, err
+		}
+		items = append(items, i)
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return items, nil
+}

internal/db/dbq/you_might_like.sql.go

@@ -0,0 +1,217 @@
+// Code generated by sqlc. DO NOT EDIT.
+// versions:
+//   sqlc v1.31.1
+// source: you_might_like.sql
+
+package dbq
+
+import (
+	"context"
+
+	"github.com/jackc/pgx/v5/pgtype"
+)
+
+const countListeningSignalForUser = `-- name: CountListeningSignalForUser :one
+
+SELECT
+    count(DISTINCT pe.track_id)::bigint AS distinct_tracks,
+    count(DISTINCT t.artist_id)::bigint AS distinct_artists
+FROM play_events pe
+JOIN tracks t ON t.id = pe.track_id
+WHERE pe.user_id = $1 AND pe.was_skipped = false
+`
+
+type CountListeningSignalForUserRow struct {
+	DistinctTracks  int64
+	DistinctArtists int64
+}
+
+// "You might like" Home rows (#790). The daily build computes ranked
+// album/artist IDs in Go (similarity roll-up + cold-start gate) and
+// atomic-replaces them here; /api/home reads them back hydrated.
+// Cold-start gate. Returns the breadth of the user's real listening:
+// distinct unskipped tracks played and distinct artists played. The
+// build skips You-might-like entirely below a threshold (a thin history
+// yields near-random roll-ups). was_skipped=false so a user spamming
+// next can't inflate the signal.
+func (q *Queries) CountListeningSignalForUser(ctx context.Context, userID pgtype.UUID) (CountListeningSignalForUserRow, error) {
+	row := q.db.QueryRow(ctx, countListeningSignalForUser, userID)
+	var i CountListeningSignalForUserRow
+	err := row.Scan(&i.DistinctTracks, &i.DistinctArtists)
+	return i, err
+}
+
+const deleteYouMightLikeAlbumsForUser = `-- name: DeleteYouMightLikeAlbumsForUser :exec
+DELETE FROM you_might_like_albums WHERE user_id = $1
+`
+
+func (q *Queries) DeleteYouMightLikeAlbumsForUser(ctx context.Context, userID pgtype.UUID) error {
+	_, err := q.db.Exec(ctx, deleteYouMightLikeAlbumsForUser, userID)
+	return err
+}
+
+const deleteYouMightLikeArtistsForUser = `-- name: DeleteYouMightLikeArtistsForUser :exec
+DELETE FROM you_might_like_artists WHERE user_id = $1
+`
+
+func (q *Queries) DeleteYouMightLikeArtistsForUser(ctx context.Context, userID pgtype.UUID) error {
+	_, err := q.db.Exec(ctx, deleteYouMightLikeArtistsForUser, userID)
+	return err
+}
+
+const insertYouMightLikeAlbum = `-- name: InsertYouMightLikeAlbum :exec
+INSERT INTO you_might_like_albums (user_id, album_id, rank)
+VALUES ($1, $2, $3)
+`
+
+type InsertYouMightLikeAlbumParams struct {
+	UserID  pgtype.UUID
+	AlbumID pgtype.UUID
+	Rank    int32
+}
+
+func (q *Queries) InsertYouMightLikeAlbum(ctx context.Context, arg InsertYouMightLikeAlbumParams) error {
+	_, err := q.db.Exec(ctx, insertYouMightLikeAlbum, arg.UserID, arg.AlbumID, arg.Rank)
+	return err
+}
+
+const insertYouMightLikeArtist = `-- name: InsertYouMightLikeArtist :exec
+INSERT INTO you_might_like_artists (user_id, artist_id, rank)
+VALUES ($1, $2, $3)
+`
+
+type InsertYouMightLikeArtistParams struct {
+	UserID   pgtype.UUID
+	ArtistID pgtype.UUID
+	Rank     int32
+}
+
+func (q *Queries) InsertYouMightLikeArtist(ctx context.Context, arg InsertYouMightLikeArtistParams) error {
+	_, err := q.db.Exec(ctx, insertYouMightLikeArtist, arg.UserID, arg.ArtistID, arg.Rank)
+	return err
+}
+
+const listYouMightLikeAlbumsForUser = `-- name: ListYouMightLikeAlbumsForUser :many
+SELECT albums.id, albums.title, albums.sort_title, albums.artist_id, albums.release_date, albums.mbid, albums.cover_art_path, albums.created_at, albums.updated_at, albums.cover_art_source, albums.cover_art_sources_version, artists.name AS artist_name
+FROM you_might_like_albums yml
+JOIN albums  ON albums.id  = yml.album_id
+JOIN artists ON artists.id = albums.artist_id
+WHERE yml.user_id = $1
+ORDER BY yml.rank
+LIMIT $2
+`
+
+type ListYouMightLikeAlbumsForUserParams struct {
+	UserID pgtype.UUID
+	Limit  int32
+}
+
+type ListYouMightLikeAlbumsForUserRow struct {
+	Album      Album
+	ArtistName string
+}
+
+// Read path. Same projection as ListRediscoverAlbumsForUser so the API
+// layer reuses albumRefFrom(row.Album, row.ArtistName, …). Ordered by
+// the rank persisted at build time. Final cross-section dedup (vs Most
+// Played / Rediscover) and the output cap land in the Go layer
+// (internal/recommendation/home.go).
+func (q *Queries) ListYouMightLikeAlbumsForUser(ctx context.Context, arg ListYouMightLikeAlbumsForUserParams) ([]ListYouMightLikeAlbumsForUserRow, error) {
+	rows, err := q.db.Query(ctx, listYouMightLikeAlbumsForUser, arg.UserID, arg.Limit)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var items []ListYouMightLikeAlbumsForUserRow
+	for rows.Next() {
+		var i ListYouMightLikeAlbumsForUserRow
+		if err := rows.Scan(
+			&i.Album.ID,
+			&i.Album.Title,
+			&i.Album.SortTitle,
+			&i.Album.ArtistID,
+			&i.Album.ReleaseDate,
+			&i.Album.Mbid,
+			&i.Album.CoverArtPath,
+			&i.Album.CreatedAt,
+			&i.Album.UpdatedAt,
+			&i.Album.CoverArtSource,
+			&i.Album.CoverArtSourcesVersion,
+			&i.ArtistName,
+		); err != nil {
+			return nil, err
+		}
+		items = append(items, i)
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return items, nil
+}
+
+const listYouMightLikeArtistsForUser = `-- name: ListYouMightLikeArtistsForUser :many
+SELECT artists.id, artists.name, artists.sort_name, artists.mbid, artists.created_at, artists.updated_at, artists.artist_thumb_path, artists.artist_fanart_path, artists.artist_art_source, artists.artist_art_sources_version,
+       cov.id AS cover_album_id,
+       cnt.album_count::bigint AS album_count
+FROM you_might_like_artists yml
+JOIN artists ON artists.id = yml.artist_id
+LEFT JOIN LATERAL (
+    SELECT id FROM albums
+    WHERE artist_id = artists.id AND cover_art_path IS NOT NULL
+    ORDER BY created_at DESC LIMIT 1
+) cov ON true
+LEFT JOIN LATERAL (
+    SELECT count(*) AS album_count
+    FROM albums WHERE artist_id = artists.id
+) cnt ON true
+WHERE yml.user_id = $1
+ORDER BY yml.rank
+LIMIT $2
+`
+
+type ListYouMightLikeArtistsForUserParams struct {
+	UserID pgtype.UUID
+	Limit  int32
+}
+
+type ListYouMightLikeArtistsForUserRow struct {
+	Artist       Artist
+	CoverAlbumID pgtype.UUID
+	AlbumCount   int64
+}
+
+// Read path. Same projection as ListRediscoverArtistsForUser (embeds the
+// artist + a representative cover_album_id + album_count) so the API
+// layer reuses artistRefFromCovered. Ordered by persisted rank.
+func (q *Queries) ListYouMightLikeArtistsForUser(ctx context.Context, arg ListYouMightLikeArtistsForUserParams) ([]ListYouMightLikeArtistsForUserRow, error) {
+	rows, err := q.db.Query(ctx, listYouMightLikeArtistsForUser, arg.UserID, arg.Limit)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var items []ListYouMightLikeArtistsForUserRow
+	for rows.Next() {
+		var i ListYouMightLikeArtistsForUserRow
+		if err := rows.Scan(
+			&i.Artist.ID,
+			&i.Artist.Name,
+			&i.Artist.SortName,
+			&i.Artist.Mbid,
+			&i.Artist.CreatedAt,
+			&i.Artist.UpdatedAt,
+			&i.Artist.ArtistThumbPath,
+			&i.Artist.ArtistFanartPath,
+			&i.Artist.ArtistArtSource,
+			&i.Artist.ArtistArtSourcesVersion,
+			&i.CoverAlbumID,
+			&i.AlbumCount,
+		); err != nil {
+			return nil, err
+		}
+		items = append(items, i)
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return items, nil
+}

internal/db/migrations/0034_you_might_like.down.sql

@@ -0,0 +1,3 @@
+-- Reverse 0034_you_might_like.up.sql.
+DROP TABLE IF EXISTS you_might_like_artists;
+DROP TABLE IF EXISTS you_might_like_albums;

internal/db/migrations/0034_you_might_like.up.sql

@@ -0,0 +1,36 @@
+-- 0034_you_might_like.up.sql — "You might like" Home rows (#790).
+--
+-- Per-user ranked lists of IN-LIBRARY albums/artists the listener
+-- doesn't actively spin but is predicted to enjoy, derived from the
+-- same similarity + like-weighted candidate engine that powers For-You
+-- (rolled up from track scores to album/artist). Built in the daily
+-- 3am BuildSystemPlaylists pass and atomic-replaced, exactly like the
+-- system playlists; read back by /api/home.
+--
+-- Two thin tables (id + rank) rather than denormalized snapshots: the
+-- Home read path hydrates album/artist refs through the existing
+-- albums/artists joins, so a later metadata edit is reflected without
+-- a rebuild. CASCADE on user/album/artist deletes keeps them clean.
+
+CREATE TABLE you_might_like_albums (
+    user_id   uuid        NOT NULL REFERENCES users(id)  ON DELETE CASCADE,
+    album_id  uuid        NOT NULL REFERENCES albums(id) ON DELETE CASCADE,
+    rank      integer     NOT NULL,
+    built_at  timestamptz NOT NULL DEFAULT now(),
+    PRIMARY KEY (user_id, album_id)
+);
+
+-- Read path orders by rank within a user; the index serves it directly.
+CREATE INDEX you_might_like_albums_user_rank_idx
+    ON you_might_like_albums (user_id, rank);
+
+CREATE TABLE you_might_like_artists (
+    user_id    uuid        NOT NULL REFERENCES users(id)   ON DELETE CASCADE,
+    artist_id  uuid        NOT NULL REFERENCES artists(id) ON DELETE CASCADE,
+    rank       integer     NOT NULL,
+    built_at   timestamptz NOT NULL DEFAULT now(),
+    PRIMARY KEY (user_id, artist_id)
+);
+
+CREATE INDEX you_might_like_artists_user_rank_idx
+    ON you_might_like_artists (user_id, rank);

internal/db/migrations/0035_taste_profile.down.sql

@@ -0,0 +1,3 @@
+-- Reverse 0035_taste_profile.up.sql.
+DROP TABLE IF EXISTS taste_profile_tags;
+DROP TABLE IF EXISTS taste_profile_artists;

internal/db/migrations/0035_taste_profile.up.sql

@@ -0,0 +1,33 @@
+-- 0035_taste_profile.up.sql — per-user taste profile (#796 phase 1).
+--
+-- A persistent, decaying model of each user's taste, rebuilt daily from
+-- graded play engagement (completion + skip position) plus explicit
+-- likes. Two facet tables: weighted artists and weighted genre tags.
+-- Weight is a signed float — positive = drawn to, negative = (passively)
+-- avoided; magnitude reflects decayed engagement. Phase 1 only BUILDS
+-- these; consumption (candidate sourcing + scoring) lands in phase 2.
+--
+-- CASCADE on user/artist deletes keeps them clean. Indexed by
+-- (user_id, weight DESC) to serve "top taste artists/tags" reads cheaply.
+
+CREATE TABLE taste_profile_artists (
+    user_id    uuid             NOT NULL REFERENCES users(id)   ON DELETE CASCADE,
+    artist_id  uuid             NOT NULL REFERENCES artists(id) ON DELETE CASCADE,
+    weight     double precision NOT NULL,
+    updated_at timestamptz      NOT NULL DEFAULT now(),
+    PRIMARY KEY (user_id, artist_id)
+);
+
+CREATE INDEX taste_profile_artists_user_weight_idx
+    ON taste_profile_artists (user_id, weight DESC);
+
+CREATE TABLE taste_profile_tags (
+    user_id    uuid             NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    tag        text             NOT NULL,
+    weight     double precision NOT NULL,
+    updated_at timestamptz      NOT NULL DEFAULT now(),
+    PRIMARY KEY (user_id, tag)
+);
+
+CREATE INDEX taste_profile_tags_user_weight_idx
+    ON taste_profile_tags (user_id, weight DESC);

internal/db/queries/taste_profile.sql

@@ -0,0 +1,66 @@
+-- Taste profile (#796 phase 1). The daily build computes signed artist/tag
+-- weights in Go (graded engagement + decay + like bonus) and atomic-replaces
+-- them here. Read queries serve "top taste" lookups (used in phase 2).
+
+-- name: ListPlayEngagementInputsForUser :many
+-- One row per play in the decay-relevant window. completion is the play's
+-- completion ratio (precomputed column when present, else duration_played /
+-- track duration, clamped to [0,1]); age_days drives the time-decay. Genre
+-- is split into tags in Go. Quarantined tracks are excluded.
+SELECT
+    t.artist_id,
+    t.genre,
+    LEAST(GREATEST(
+        COALESCE(pe.completion_ratio,
+                 pe.duration_played_ms::float8 / NULLIF(t.duration_ms, 0),
+                 0), 0), 1)::float8 AS completion,
+    (EXTRACT(epoch FROM now() - pe.started_at) / 86400.0)::float8 AS age_days
+FROM play_events pe
+JOIN tracks t ON t.id = pe.track_id
+WHERE pe.user_id = $1
+  AND pe.started_at > now() - ($2::float8 * INTERVAL '1 day')
+  AND NOT EXISTS (
+      SELECT 1 FROM lidarr_quarantine q
+      WHERE q.user_id = $1 AND q.track_id = t.id
+  );
+
+-- name: ListLikedTrackTasteInputsForUser :many
+-- (artist_id, genre) for each track the user has explicitly liked. Feeds the
+-- track-like bonus into the liked track's artist and tags.
+SELECT t.artist_id, t.genre
+FROM general_likes gl
+JOIN tracks t ON t.id = gl.track_id
+WHERE gl.user_id = $1;
+
+-- name: ListLikedArtistIDsForUser :many
+-- Artists the user has explicitly liked; feeds the artist-like bonus.
+SELECT artist_id FROM general_likes_artists WHERE user_id = $1;
+
+-- name: DeleteTasteProfileArtistsForUser :exec
+DELETE FROM taste_profile_artists WHERE user_id = $1;
+
+-- name: InsertTasteProfileArtist :exec
+INSERT INTO taste_profile_artists (user_id, artist_id, weight)
+VALUES ($1, $2, $3);
+
+-- name: DeleteTasteProfileTagsForUser :exec
+DELETE FROM taste_profile_tags WHERE user_id = $1;
+
+-- name: InsertTasteProfileTag :exec
+INSERT INTO taste_profile_tags (user_id, tag, weight)
+VALUES ($1, $2, $3);
+
+-- name: ListTasteProfileArtistsForUser :many
+-- Top-weighted taste artists (phase-2 consumption + tests).
+SELECT artist_id, weight
+FROM taste_profile_artists
+WHERE user_id = $1
+ORDER BY weight DESC
+LIMIT $2;
+
+-- name: ListTasteProfileTagsForUser :many
+SELECT tag, weight
+FROM taste_profile_tags
+WHERE user_id = $1
+ORDER BY weight DESC
+LIMIT $2;

internal/db/queries/you_might_like.sql

@@ -0,0 +1,66 @@
+-- "You might like" Home rows (#790). The daily build computes ranked
+-- album/artist IDs in Go (similarity roll-up + cold-start gate) and
+-- atomic-replaces them here; /api/home reads them back hydrated.
+
+-- name: CountListeningSignalForUser :one
+-- Cold-start gate. Returns the breadth of the user's real listening:
+-- distinct unskipped tracks played and distinct artists played. The
+-- build skips You-might-like entirely below a threshold (a thin history
+-- yields near-random roll-ups). was_skipped=false so a user spamming
+-- next can't inflate the signal.
+SELECT
+    count(DISTINCT pe.track_id)::bigint AS distinct_tracks,
+    count(DISTINCT t.artist_id)::bigint AS distinct_artists
+FROM play_events pe
+JOIN tracks t ON t.id = pe.track_id
+WHERE pe.user_id = $1 AND pe.was_skipped = false;
+
+-- name: DeleteYouMightLikeAlbumsForUser :exec
+DELETE FROM you_might_like_albums WHERE user_id = $1;
+
+-- name: InsertYouMightLikeAlbum :exec
+INSERT INTO you_might_like_albums (user_id, album_id, rank)
+VALUES ($1, $2, $3);
+
+-- name: DeleteYouMightLikeArtistsForUser :exec
+DELETE FROM you_might_like_artists WHERE user_id = $1;
+
+-- name: InsertYouMightLikeArtist :exec
+INSERT INTO you_might_like_artists (user_id, artist_id, rank)
+VALUES ($1, $2, $3);
+
+-- name: ListYouMightLikeAlbumsForUser :many
+-- Read path. Same projection as ListRediscoverAlbumsForUser so the API
+-- layer reuses albumRefFrom(row.Album, row.ArtistName, …). Ordered by
+-- the rank persisted at build time. Final cross-section dedup (vs Most
+-- Played / Rediscover) and the output cap land in the Go layer
+-- (internal/recommendation/home.go).
+SELECT sqlc.embed(albums), artists.name AS artist_name
+FROM you_might_like_albums yml
+JOIN albums  ON albums.id  = yml.album_id
+JOIN artists ON artists.id = albums.artist_id
+WHERE yml.user_id = $1
+ORDER BY yml.rank
+LIMIT $2;
+
+-- name: ListYouMightLikeArtistsForUser :many
+-- Read path. Same projection as ListRediscoverArtistsForUser (embeds the
+-- artist + a representative cover_album_id + album_count) so the API
+-- layer reuses artistRefFromCovered. Ordered by persisted rank.
+SELECT sqlc.embed(artists),
+       cov.id AS cover_album_id,
+       cnt.album_count::bigint AS album_count
+FROM you_might_like_artists yml
+JOIN artists ON artists.id = yml.artist_id
+LEFT JOIN LATERAL (
+    SELECT id FROM albums
+    WHERE artist_id = artists.id AND cover_art_path IS NOT NULL
+    ORDER BY created_at DESC LIMIT 1
+) cov ON true
+LEFT JOIN LATERAL (
+    SELECT count(*) AS album_count
+    FROM albums WHERE artist_id = artists.id
+) cnt ON true
+WHERE yml.user_id = $1
+ORDER BY yml.rank
+LIMIT $2;

internal/playlists/scheduler.go

@@ -28,6 +28,7 @@ import (
 	"github.com/jackc/pgx/v5/pgxpool"
 
 	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
+	"git.fabledsword.com/bvandeusen/minstrel/internal/taste"
 )
 
 // dailyRebuildHour is the local-time hour at which each user's system
@@ -158,10 +159,7 @@ func (s *Scheduler) registerLocked(ctx context.Context, userID pgtype.UUID, tz s
 	job, err := s.gocron.NewJob(
 		gocron.CronJob(cronExpr, false /* withSeconds */),
 		gocron.NewTask(func() {
-			if err := BuildSystemPlaylists(ctx, s.pool, s.logger, userID, time.Now(), s.dataDir); err != nil {
-				s.logger.Warn("scheduler: build failed",
-					"user_id", uuidStringPL(userID), "err", err)
-			}
+			s.rebuildUserDaily(ctx, userID, time.Now())
 		}),
 	)
 	if err != nil {
@@ -220,10 +218,22 @@ func (s *Scheduler) reconcile(ctx context.Context) {
 // whose scheduled fire was missed during downtime get caught up.
 func (s *Scheduler) runStartupCatchUp(ctx context.Context, users []dbq.ListActiveUsersWithTimezonesRow) {
 	for _, u := range users {
-		if err := BuildSystemPlaylists(ctx, s.pool, s.logger, u.ID, time.Now(), s.dataDir); err != nil {
-			s.logger.Warn("scheduler: startup catch-up build failed",
-				"user_id", uuidStringPL(u.ID), "err", err)
-		}
+		s.rebuildUserDaily(ctx, u.ID, time.Now())
+	}
+}
+
+// rebuildUserDaily recomputes the user's taste profile, then rebuilds their
+// system playlists + You-might-like rows. Taste runs first so the playlist
+// build can read a fresh profile (phase-2 consumption); both steps are
+// best-effort and a failure in one is logged without blocking the other.
+func (s *Scheduler) rebuildUserDaily(ctx context.Context, userID pgtype.UUID, now time.Time) {
+	if err := taste.BuildTasteProfile(ctx, s.pool, s.logger, userID, taste.DefaultConfig()); err != nil {
+		s.logger.Warn("scheduler: taste profile rebuild failed",
+			"user_id", uuidStringPL(userID), "err", err)
+	}
+	if err := BuildSystemPlaylists(ctx, s.pool, s.logger, userID, now, s.dataDir); err != nil {
+		s.logger.Warn("scheduler: build failed",
+			"user_id", uuidStringPL(userID), "err", err)
 	}
 }
 

internal/playlists/system.go

@@ -5,6 +5,7 @@
 package playlists
 
 import (
+	"bytes"
 	"context"
 	"crypto/sha256"
 	"encoding/binary"
@@ -147,6 +148,11 @@ var systemMixWeights = recommendation.ScoringWeights{
 	JitterMagnitude:  0.1,
 	ContextWeight:    0.5,
 	SimilarityWeight: 1.5,
+	// Taste profile (#796 phase 2): the daily mixes are the primary
+	// taste-driven surface, so they lean on it. TasteMatchScore is in
+	// [-1,+1], so 1.5 makes a strong taste fit comparable to a like boost
+	// while passive avoidance (negative) gently demotes.
+	TasteWeight: 1.5,
 }
 
 // forYouHeadN is the number of top-scored tracks that anchor the For-You
@@ -180,8 +186,21 @@ func scoreAndSortCandidates(cands []recommendation.Candidate, userID pgtype.UUID
 		c     recommendation.Candidate
 		score float64
 	}
-	pairs := make([]scored, len(cands))
-	for i, c := range cands {
+	// Pin candidate order by track id before drawing jitter. The candidate
+	// query (LoadRadioCandidatesV2) has ORDER BY random() arms and no
+	// stable outer ordering, so DB row order varies call-to-call. Since
+	// the i-th candidate gets the i-th seeded jitter draw, an unstable
+	// input order would assign different jitter to the same track across
+	// same-day rebuilds and reorder near-ties — breaking the daily
+	// determinism this function promises. Sorting by id first makes the
+	// jitter assignment a function of (track, day) alone.
+	ordered := make([]recommendation.Candidate, len(cands))
+	copy(ordered, cands)
+	sort.SliceStable(ordered, func(i, j int) bool {
+		return uuidLessPL(ordered[i].Track.ID, ordered[j].Track.ID)
+	})
+	pairs := make([]scored, len(ordered))
+	for i, c := range ordered {
 		pairs[i] = scored{c: c, score: recommendation.Score(c.Inputs, systemMixWeights, now, rng.Float64)}
 	}
 	sort.SliceStable(pairs, func(i, j int) bool {
@@ -497,6 +516,13 @@ func BuildSystemPlaylists(ctx context.Context, pool *pgxpool.Pool, logger *slog.
 		built = append(built, out...)
 	}
 
+	// "You might like" Home rows reuse the same similarity engine but
+	// persist to dedicated album/artist tables (not playlist_tracks).
+	// Computed here (reads only) and atomic-replaced inside the tx below,
+	// alongside the system playlists. A failed/gated computation is
+	// handled by yml.built (leave prior rows vs. clear) — never fatal.
+	yml := buildYouMightLike(ctx, q, logger, userID, dateStr, now)
+
 	// Atomic replace inside a transaction.
 	tx, err := pool.Begin(ctx)
 	if err != nil {
@@ -530,6 +556,13 @@ func BuildSystemPlaylists(ctx context.Context, pool *pgxpool.Pool, logger *slog.
 		createdIDs = append(createdIDs, id)
 	}
 
+	if yml.built {
+		if err := persistYouMightLike(ctx, qtx, userID, yml); err != nil {
+			buildErr = fmt.Errorf("persist you-might-like: %w", err)
+			return buildErr
+		}
+	}
+
 	if err := tx.Commit(ctx); err != nil {
 		buildErr = fmt.Errorf("commit tx: %w", err)
 		return buildErr
@@ -695,6 +728,12 @@ func insertSystemPlaylist(ctx context.Context, qtx *dbq.Queries, userID pgtype.U
 // (pgtype.UUID's String method exists on some pgx versions but not others;
 // also the playlists package needs this independent of test helpers.)
 // Suffix `PL` distinguishes it from any test helper named uuidString.
+// uuidLessPL reports whether a sorts before b by raw 16-byte value. Used
+// to pin candidate order deterministically before jitter assignment.
+func uuidLessPL(a, b pgtype.UUID) bool {
+	return bytes.Compare(a.Bytes[:], b.Bytes[:]) < 0
+}
+
 func uuidStringPL(u pgtype.UUID) string {
 	if !u.Valid {
 		return "<nil>"

internal/playlists/you_might_like.go

@@ -0,0 +1,227 @@
+// you_might_like.go builds the per-user "You might like" Home rows
+// (#790): in-library albums/artists the listener doesn't actively spin
+// but is predicted to enjoy. It reuses the For-You candidate engine
+// (similarity + like-weighted scoring) and rolls the per-track scores up
+// to album/artist granularity, gated on a minimum listening history so a
+// near-empty profile ships nothing rather than noise.
+//
+// Built in the same daily BuildSystemPlaylists pass and atomic-replaced
+// alongside the system playlists; read back by /api/home.
+package playlists
+
+import (
+	"context"
+	"fmt"
+	"log/slog"
+	"math/rand"
+	"sort"
+	"time"
+
+	"github.com/jackc/pgx/v5/pgtype"
+
+	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
+	"git.fabledsword.com/bvandeusen/minstrel/internal/recommendation"
+)
+
+const (
+	// Cold-start gate. Below this much *real* listening the similarity
+	// roll-up degrades toward random fill, so You-might-like ships
+	// nothing rather than arbitrary tiles. Both bars must clear: distinct
+	// tracks rules out "played 3 songs on repeat," distinct artists rules
+	// out "hammered one album." Conservative defaults; raise if early
+	// rows feel random on thin libraries.
+	youMightLikeMinDistinctTracks  = 20
+	youMightLikeMinDistinctArtists = 5
+
+	// Persisted depth — a few more than the rendered HomeYouMightLikeLimit
+	// so the read-time cross-section dedup (vs Most Played / Rediscover)
+	// has headroom before trimming.
+	youMightLikeAlbumsN  = 12
+	youMightLikeArtistsN = 12
+
+	// One strongly-matched artist shouldn't fill the albums row.
+	youMightLikeMaxAlbumsPerArtist = 2
+
+	// Aggregation: sum of an entity's top-K track scores. Favors albums/
+	// artists with several good matches over a single outlier track.
+	youMightLikeAggTopK = 3
+)
+
+// youMightLikeResult carries one day's roll-up. built=false means the
+// computation failed and the caller must leave any existing rows intact;
+// built=true with nil slices means "explicitly empty" (cold-start gate or
+// no candidates) and the caller should clear the user's rows.
+type youMightLikeResult struct {
+	albumIDs  []pgtype.UUID
+	artistIDs []pgtype.UUID
+	built     bool
+}
+
+// buildYouMightLike computes the user's daily album/artist rolls. Reads
+// only — the caller persists inside the build tx. Never returns an error:
+// a failure logs and yields built=false so the prior day's rows survive.
+func buildYouMightLike(
+	ctx context.Context, q *dbq.Queries, logger *slog.Logger,
+	userID pgtype.UUID, dateStr string, now time.Time,
+) youMightLikeResult {
+	signal, err := q.CountListeningSignalForUser(ctx, userID)
+	if err != nil {
+		logger.Warn("you-might-like: listening-signal query failed; skipping",
+			"user_id", uuidStringPL(userID), "err", err)
+		return youMightLikeResult{built: false}
+	}
+	if signal.DistinctTracks < youMightLikeMinDistinctTracks ||
+		signal.DistinctArtists < youMightLikeMinDistinctArtists {
+		// Cold start: not enough listening to recommend from. built=true
+		// clears any stale rows (normally none) and ships an empty row.
+		return youMightLikeResult{built: true}
+	}
+
+	seeds, err := q.PickTopPlayedTracksForUser(ctx, userID)
+	if err != nil {
+		logger.Warn("you-might-like: seed query failed; skipping",
+			"user_id", uuidStringPL(userID), "err", err)
+		return youMightLikeResult{built: false}
+	}
+	seed := pickForYouSeedForDay(seeds, userID, dateStr)
+	if !seed.Valid {
+		return youMightLikeResult{built: true}
+	}
+
+	zeroVec := recommendation.SessionVector{Seed: true}
+	cands, err := recommendation.LoadCandidatesFromSimilarity(
+		ctx, q, userID, seed, 1, zeroVec,
+		[]pgtype.UUID{seed}, systemForYouSourceLimits(),
+	)
+	if err != nil {
+		logger.Warn("you-might-like: candidate load failed; skipping",
+			"user_id", uuidStringPL(userID), "err", err)
+		return youMightLikeResult{built: false}
+	}
+
+	albumIDs, artistIDs := rollUpCandidates(cands, userID, dateStr, now)
+	return youMightLikeResult{albumIDs: albumIDs, artistIDs: artistIDs, built: true}
+}
+
+// scoredEntity is an album or artist with its aggregated score.
+type scoredEntity struct {
+	id    pgtype.UUID
+	score float64
+}
+
+// rollUpCandidates scores every candidate track (systemMixWeights, jitter
+// seeded by userIDHash so near-ties rotate day-to-day) and aggregates the
+// scores up to album and artist via sum-of-top-K. Returns the top-N album
+// and artist IDs, with a per-artist cap on the album list.
+func rollUpCandidates(
+	cands []recommendation.Candidate, userID pgtype.UUID, dateStr string, now time.Time,
+) (albumIDs, artistIDs []pgtype.UUID) {
+	rng := rand.New(rand.NewSource(int64(userIDHash(userID, dateStr))))
+	albumScores := map[pgtype.UUID][]float64{}
+	artistScores := map[pgtype.UUID][]float64{}
+	albumArtist := map[pgtype.UUID]pgtype.UUID{}
+	for _, c := range cands {
+		s := recommendation.Score(c.Inputs, systemMixWeights, now, rng.Float64)
+		if c.Track.AlbumID.Valid {
+			albumScores[c.Track.AlbumID] = append(albumScores[c.Track.AlbumID], s)
+			albumArtist[c.Track.AlbumID] = c.Track.ArtistID
+		}
+		if c.Track.ArtistID.Valid {
+			artistScores[c.Track.ArtistID] = append(artistScores[c.Track.ArtistID], s)
+		}
+	}
+
+	rankedAlbums := capAlbumsPerArtist(
+		rankEntities(albumScores, dateStr), albumArtist, youMightLikeMaxAlbumsPerArtist)
+	albumIDs = topNEntityIDs(rankedAlbums, youMightLikeAlbumsN)
+	artistIDs = topNEntityIDs(rankEntities(artistScores, dateStr), youMightLikeArtistsN)
+	return albumIDs, artistIDs
+}
+
+// rankEntities aggregates each entity's track scores (sum-of-top-K) and
+// returns them sorted by score DESC, ties broken deterministically by
+// tieBreakHash(id, dateStr) so ordering is stable within a day.
+func rankEntities(scoresByEntity map[pgtype.UUID][]float64, dateStr string) []scoredEntity {
+	out := make([]scoredEntity, 0, len(scoresByEntity))
+	for id, scores := range scoresByEntity {
+		out = append(out, scoredEntity{id: id, score: sumTopK(scores, youMightLikeAggTopK)})
+	}
+	sort.SliceStable(out, func(i, j int) bool {
+		if out[i].score != out[j].score {
+			return out[i].score > out[j].score
+		}
+		return tieBreakHash(out[i].id, dateStr) < tieBreakHash(out[j].id, dateStr)
+	})
+	return out
+}
+
+// sumTopK sorts scores DESC and sums the highest k.
+func sumTopK(scores []float64, k int) float64 {
+	sort.Sort(sort.Reverse(sort.Float64Slice(scores)))
+	sum := 0.0
+	for i := 0; i < len(scores) && i < k; i++ {
+		sum += scores[i]
+	}
+	return sum
+}
+
+// capAlbumsPerArtist drops albums beyond maxPerArtist for any one artist,
+// preserving input (score) order.
+func capAlbumsPerArtist(
+	albums []scoredEntity, albumArtist map[pgtype.UUID]pgtype.UUID, maxPerArtist int,
+) []scoredEntity {
+	perArtist := map[pgtype.UUID]int{}
+	out := make([]scoredEntity, 0, len(albums))
+	for _, a := range albums {
+		art := albumArtist[a.id]
+		if art.Valid {
+			if perArtist[art] >= maxPerArtist {
+				continue
+			}
+			perArtist[art]++
+		}
+		out = append(out, a)
+	}
+	return out
+}
+
+// topNEntityIDs truncates to n and projects the IDs in rank order.
+func topNEntityIDs(entities []scoredEntity, n int) []pgtype.UUID {
+	if len(entities) > n {
+		entities = entities[:n]
+	}
+	out := make([]pgtype.UUID, 0, len(entities))
+	for _, e := range entities {
+		out = append(out, e.id)
+	}
+	return out
+}
+
+// persistYouMightLike atomic-replaces the user's You-might-like rows
+// inside the build tx. Called only when the roll-up was freshly built;
+// a failed computation leaves the prior rows untouched.
+func persistYouMightLike(
+	ctx context.Context, qtx *dbq.Queries, userID pgtype.UUID, r youMightLikeResult,
+) error {
+	if err := qtx.DeleteYouMightLikeAlbumsForUser(ctx, userID); err != nil {
+		return fmt.Errorf("delete you-might-like albums: %w", err)
+	}
+	for i, id := range r.albumIDs {
+		if err := qtx.InsertYouMightLikeAlbum(ctx, dbq.InsertYouMightLikeAlbumParams{
+			UserID: userID, AlbumID: id, Rank: int32(i),
+		}); err != nil {
+			return fmt.Errorf("insert you-might-like album: %w", err)
+		}
+	}
+	if err := qtx.DeleteYouMightLikeArtistsForUser(ctx, userID); err != nil {
+		return fmt.Errorf("delete you-might-like artists: %w", err)
+	}
+	for i, id := range r.artistIDs {
+		if err := qtx.InsertYouMightLikeArtist(ctx, dbq.InsertYouMightLikeArtistParams{
+			UserID: userID, ArtistID: id, Rank: int32(i),
+		}); err != nil {
+			return fmt.Errorf("insert you-might-like artist: %w", err)
+		}
+	}
+	return nil
+}

internal/playlists/you_might_like_db_test.go

@@ -0,0 +1,99 @@
+package playlists_test
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/jackc/pgx/v5/pgtype"
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"git.fabledsword.com/bvandeusen/minstrel/internal/playlists"
+)
+
+// countYouMightLike returns the persisted row counts for a user.
+func countYouMightLike(t *testing.T, pool *pgxpool.Pool, userID pgtype.UUID) (albums, artists int) {
+	t.Helper()
+	ctx := context.Background()
+	if err := pool.QueryRow(ctx,
+		`SELECT count(*) FROM you_might_like_albums WHERE user_id = $1`, userID,
+	).Scan(&albums); err != nil {
+		t.Fatalf("count albums: %v", err)
+	}
+	if err := pool.QueryRow(ctx,
+		`SELECT count(*) FROM you_might_like_artists WHERE user_id = $1`, userID,
+	).Scan(&artists); err != nil {
+		t.Fatalf("count artists: %v", err)
+	}
+	return albums, artists
+}
+
+// TestYouMightLike_ColdStartGate: a thin profile (3 artists × 3 tracks =
+// 9 distinct tracks, below the 20-track / 5-artist gate) must produce no
+// You-might-like rows — the build ships nothing rather than near-random
+// tiles.
+func TestYouMightLike_ColdStartGate(t *testing.T) {
+	pool := newPool(t)
+	logger := discardLogger()
+	u, _ := seedActiveLibrary(t, pool, "ymlcold", 3, 3)
+
+	if err := playlists.BuildSystemPlaylists(
+		context.Background(), pool, logger, u.ID, time.Now().UTC(), t.TempDir(),
+	); err != nil {
+		t.Fatalf("build: %v", err)
+	}
+
+	albums, artists := countYouMightLike(t, pool, u.ID)
+	if albums != 0 || artists != 0 {
+		t.Errorf("cold-start user should have no you-might-like rows; got %d albums, %d artists",
+			albums, artists)
+	}
+}
+
+// TestYouMightLike_SufficientActivityPopulates: a rich profile (8 artists
+// × 4 tracks = 32 distinct tracks, clearing both gate bars) populates the
+// You-might-like tables in the daily build.
+func TestYouMightLike_SufficientActivityPopulates(t *testing.T) {
+	pool := newPool(t)
+	logger := discardLogger()
+	u, _ := seedActiveLibrary(t, pool, "ymlrich", 8, 4)
+
+	if err := playlists.BuildSystemPlaylists(
+		context.Background(), pool, logger, u.ID, time.Now().UTC(), t.TempDir(),
+	); err != nil {
+		t.Fatalf("build: %v", err)
+	}
+
+	albums, artists := countYouMightLike(t, pool, u.ID)
+	if albums == 0 {
+		t.Error("rich user should have you-might-like album rows; got 0")
+	}
+	if artists == 0 {
+		t.Error("rich user should have you-might-like artist rows; got 0")
+	}
+}
+
+// TestYouMightLike_AtomicReplace: a second build replaces rather than
+// appends, so counts stay bounded by the persisted depth.
+func TestYouMightLike_AtomicReplace(t *testing.T) {
+	pool := newPool(t)
+	logger := discardLogger()
+	u, _ := seedActiveLibrary(t, pool, "ymlreplace", 8, 4)
+	ctx := context.Background()
+
+	for i := 0; i < 2; i++ {
+		if err := playlists.BuildSystemPlaylists(
+			ctx, pool, logger, u.ID, time.Now().UTC(), t.TempDir(),
+		); err != nil {
+			t.Fatalf("build %d: %v", i, err)
+		}
+	}
+
+	albums, artists := countYouMightLike(t, pool, u.ID)
+	if albums > 12 {
+		t.Errorf("albums = %d after two builds, want <= 12 (atomic replace)", albums)
+	}
+	if artists > 12 {
+		t.Errorf("artists = %d after two builds, want <= 12 (atomic replace)", artists)
+	}
+}

internal/playlists/you_might_like_test.go

@@ -0,0 +1,125 @@
+package playlists
+
+import (
+	"testing"
+	"time"
+
+	"github.com/jackc/pgx/v5/pgtype"
+
+	"git.fabledsword.com/bvandeusen/minstrel/internal/recommendation"
+)
+
+// fixedNow keeps recencyDecay stable across the pure roll-up tests.
+var fixedNow = time.Date(2026, 6, 11, 12, 0, 0, 0, time.UTC)
+
+// byteOf returns the per-test entity discriminator (makeCand sets it in
+// Bytes[15]) so assertions can name albums/artists by their small int.
+func byteOf(u pgtype.UUID) byte { return u.Bytes[15] }
+
+// countWithByte reports how many of ids carry the given Bytes[15] marker.
+func countWithByte(ids []pgtype.UUID, want byte) int {
+	n := 0
+	for _, id := range ids {
+		if byteOf(id) == want {
+			n++
+		}
+	}
+	return n
+}
+
+func TestSumTopK(t *testing.T) {
+	if got := sumTopK([]float64{1, 2, 3, 4}, 2); got != 7 {
+		t.Errorf("sumTopK top-2 of 1..4 = %v, want 7", got)
+	}
+	if got := sumTopK([]float64{5}, 3); got != 5 {
+		t.Errorf("sumTopK fewer-than-k = %v, want 5", got)
+	}
+	if got := sumTopK(nil, 3); got != 0 {
+		t.Errorf("sumTopK empty = %v, want 0", got)
+	}
+}
+
+func TestRollUpCandidates_MultiMatchAlbumRanksFirst(t *testing.T) {
+	// Album 10 (artist 100): three solid matches. Album 20 (artist 200):
+	// one slightly-stronger single match. Sum-of-top-3 should rank the
+	// multi-match album ahead of the single-match one. Similarity gaps are
+	// wide enough that the ±0.1 jitter can't reorder the result.
+	cands := []recommendation.Candidate{
+		makeCand(1, 10, 100, 0.8),
+		makeCand(2, 10, 100, 0.8),
+		makeCand(3, 10, 100, 0.8),
+		makeCand(4, 20, 200, 0.95),
+	}
+	albums, _ := rollUpCandidates(cands, testUserID, "2026-06-11", fixedNow)
+	if len(albums) < 2 {
+		t.Fatalf("want >=2 albums, got %d", len(albums))
+	}
+	if byteOf(albums[0]) != 10 {
+		t.Errorf("top album = %d, want 10 (multi-match beats single)", byteOf(albums[0]))
+	}
+}
+
+func TestRollUpCandidates_PerArtistAlbumCap(t *testing.T) {
+	// Artist 100 spans albums 10/11/12; the album row caps any one artist
+	// at youMightLikeMaxAlbumsPerArtist (2). Artist 200's album 20 should
+	// still appear.
+	cands := []recommendation.Candidate{
+		makeCand(1, 10, 100, 0.9),
+		makeCand(2, 11, 100, 0.85),
+		makeCand(3, 12, 100, 0.8),
+		makeCand(4, 20, 200, 0.7),
+	}
+	albums, _ := rollUpCandidates(cands, testUserID, "2026-06-11", fixedNow)
+	from100 := countWithByte(albums, 10) + countWithByte(albums, 11) + countWithByte(albums, 12)
+	if from100 > youMightLikeMaxAlbumsPerArtist {
+		t.Errorf("artist 100 contributed %d albums, want <= %d",
+			from100, youMightLikeMaxAlbumsPerArtist)
+	}
+	if countWithByte(albums, 20) != 1 {
+		t.Errorf("album 20 (artist 200) should survive the cap; got %d",
+			countWithByte(albums, 20))
+	}
+}
+
+func TestRollUpCandidates_ArtistRollupDistinct(t *testing.T) {
+	// Three artists; the artist roll-up should surface all three distinct
+	// artist IDs (no per-artist cap on the artist row).
+	cands := []recommendation.Candidate{
+		makeCand(1, 10, 100, 0.9),
+		makeCand(2, 11, 101, 0.6),
+		makeCand(3, 12, 102, 0.3),
+	}
+	_, artists := rollUpCandidates(cands, testUserID, "2026-06-11", fixedNow)
+	seen := map[byte]bool{}
+	for _, a := range artists {
+		seen[byteOf(a)] = true
+	}
+	for _, want := range []byte{100, 101, 102} {
+		if !seen[want] {
+			t.Errorf("artist %d missing from roll-up", want)
+		}
+	}
+}
+
+func TestCapAlbumsPerArtist_DropsBeyondCap(t *testing.T) {
+	mk := func(albumN, artistN int) (pgtype.UUID, pgtype.UUID) {
+		var al, ar pgtype.UUID
+		al.Valid, ar.Valid = true, true
+		al.Bytes[15], ar.Bytes[15] = byte(albumN), byte(artistN)
+		return al, ar
+	}
+	a10, ar1 := mk(10, 1)
+	a11, _ := mk(11, 1)
+	a12, _ := mk(12, 1)
+	a20, ar2 := mk(20, 2)
+	albumArtist := map[pgtype.UUID]pgtype.UUID{a10: ar1, a11: ar1, a12: ar1, a20: ar2}
+	in := []scoredEntity{{a10, 3}, {a11, 2}, {a12, 1}, {a20, 0.5}}
+	got := capAlbumsPerArtist(in, albumArtist, 2)
+	if len(got) != 3 {
+		t.Fatalf("len = %d, want 3 (artist 1 capped at 2 + artist 2's one)", len(got))
+	}
+	// Highest-scored two of artist 1 (albums 10, 11) kept; 12 dropped.
+	if byteOf(got[2].id) != 20 {
+		t.Errorf("third survivor = %d, want 20", byteOf(got[2].id))
+	}
+}

internal/recommendation/candidates.go

@@ -36,6 +36,11 @@ func LoadCandidates(
 		return nil, err
 	}
 
+	profile, err := LoadTasteProfile(ctx, q, userID)
+	if err != nil {
+		return nil, err
+	}
+
 	out := make([]Candidate, 0, len(rows))
 	for _, r := range rows {
 		var lpt *time.Time
@@ -52,6 +57,7 @@ func LoadCandidates(
 				PlayCount:            int(r.PlayCount),
 				SkipCount:            int(r.SkipCount),
 				ContextualMatchScore: ctxScore,
+				TasteMatchScore:      profile.Match(r.Track.ArtistID, r.Track.Genre),
 			},
 		})
 	}
@@ -117,6 +123,11 @@ func LoadCandidatesFromSimilarity(
 		return nil, err
 	}
 
+	profile, err := LoadTasteProfile(ctx, q, userID)
+	if err != nil {
+		return nil, err
+	}
+
 	out := make([]Candidate, 0, len(rows))
 	for _, r := range rows {
 		var lpt *time.Time
@@ -141,6 +152,7 @@ func LoadCandidatesFromSimilarity(
 				SkipCount:            int(r.SkipCount),
 				ContextualMatchScore: ctxScore,
 				SimilarityScore:      simScore,
+				TasteMatchScore:      profile.Match(r.Track.ArtistID, r.Track.Genre),
 			},
 		})
 	}

internal/recommendation/home.go

@@ -34,6 +34,13 @@ const (
 	// artist from dominating the row. Two is enough variety; higher
 	// reads as "this artist's discography" instead of "rediscover".
 	maxAlbumsPerArtistInRediscover = 2
+
+	// HomeYouMightLikeLimit is the rendered count for each You-might-like
+	// row. The build persists a few more (youMightLikeAlbumsN/ArtistsN)
+	// so the read-time cross-section dedup has headroom; this query asks
+	// for the persisted depth and the Go layer trims to this after dedup.
+	HomeYouMightLikeLimit = 10
+	youMightLikeFetch     = 12
 )
 
 // HomePayload is the composite returned by HomeData. All slices are
@@ -45,6 +52,8 @@ type HomePayload struct {
 	RediscoverArtists   []dbq.ListRediscoverArtistsForUserRow
 	MostPlayedTracks    []dbq.ListMostPlayedTracksForUserRow
 	LastPlayedArtists   []dbq.ListLastPlayedArtistsForUserRow
+	YouMightLikeAlbums  []dbq.ListYouMightLikeAlbumsForUserRow
+	YouMightLikeArtists []dbq.ListYouMightLikeArtistsForUserRow
 }
 
 // HomeData runs five queries in parallel and assembles the payload.
@@ -77,9 +86,11 @@ func HomeData(ctx context.Context, pool *pgxpool.Pool, userID pgtype.UUID) (*Hom
 		RediscoverArtists:   []dbq.ListRediscoverArtistsForUserRow{},
 		MostPlayedTracks:    []dbq.ListMostPlayedTracksForUserRow{},
 		LastPlayedArtists:   []dbq.ListLastPlayedArtistsForUserRow{},
+		YouMightLikeAlbums:  []dbq.ListYouMightLikeAlbumsForUserRow{},
+		YouMightLikeArtists: []dbq.ListYouMightLikeArtistsForUserRow{},
 	}
 
-	wg.Add(5)
+	wg.Add(7)
 	go func() {
 		defer wg.Done()
 		rows, err := q.ListRecentlyAddedAlbumsWithArtist(ctx, HomeRecentlyAddedLimit)
@@ -129,6 +140,28 @@ func HomeData(ctx context.Context, pool *pgxpool.Pool, userID pgtype.UUID) (*Hom
 		}
 		out.RediscoverArtists = rows
 	}()
+	go func() {
+		defer wg.Done()
+		rows, err := q.ListYouMightLikeAlbumsForUser(ctx, dbq.ListYouMightLikeAlbumsForUserParams{
+			UserID: userID, Limit: youMightLikeFetch,
+		})
+		if err != nil {
+			fail("you_might_like_albums", err)
+			return
+		}
+		out.YouMightLikeAlbums = rows
+	}()
+	go func() {
+		defer wg.Done()
+		rows, err := q.ListYouMightLikeArtistsForUser(ctx, dbq.ListYouMightLikeArtistsForUserParams{
+			UserID: userID, Limit: youMightLikeFetch,
+		})
+		if err != nil {
+			fail("you_might_like_artists", err)
+			return
+		}
+		out.YouMightLikeArtists = rows
+	}()
 	wg.Wait()
 
 	if firstErr != nil {
@@ -140,9 +173,70 @@ func HomeData(ctx context.Context, pool *pgxpool.Pool, userID pgtype.UUID) (*Hom
 	// the rediscover lists down toward HomeRediscoverLimit.
 	out.RediscoverAlbums = applyRediscoverAlbumFilters(out.RediscoverAlbums, out.MostPlayedTracks)
 	out.RediscoverArtists = applyRediscoverArtistFilters(out.RediscoverArtists, out.MostPlayedTracks)
+	// You-might-like dedups against what the user already engages with
+	// (Most Played) and against the other Home rows so a tile doesn't
+	// appear twice. Trims to HomeYouMightLikeLimit after dedup.
+	out.YouMightLikeAlbums = applyYouMightLikeAlbumFilters(
+		out.YouMightLikeAlbums, out.MostPlayedTracks, out.RediscoverAlbums)
+	out.YouMightLikeArtists = applyYouMightLikeArtistFilters(
+		out.YouMightLikeArtists, out.MostPlayedTracks, out.RediscoverArtists, out.LastPlayedArtists)
 	return out, nil
 }
 
+// applyYouMightLikeAlbumFilters drops albums the user actively plays
+// (Most Played) or that already appear in Rediscover, then trims to
+// HomeYouMightLikeLimit. Build-time rank order is preserved.
+func applyYouMightLikeAlbumFilters(
+	rows []dbq.ListYouMightLikeAlbumsForUserRow,
+	mostPlayed []dbq.ListMostPlayedTracksForUserRow,
+	rediscover []dbq.ListRediscoverAlbumsForUserRow,
+) []dbq.ListYouMightLikeAlbumsForUserRow {
+	excluded := mostPlayedAlbumIDs(mostPlayed)
+	for _, r := range rediscover {
+		excluded[r.Album.ID] = struct{}{}
+	}
+	out := make([]dbq.ListYouMightLikeAlbumsForUserRow, 0, HomeYouMightLikeLimit)
+	for _, r := range rows {
+		if _, dup := excluded[r.Album.ID]; dup {
+			continue
+		}
+		out = append(out, r)
+		if len(out) >= HomeYouMightLikeLimit {
+			break
+		}
+	}
+	return out
+}
+
+// applyYouMightLikeArtistFilters drops artists the user actively plays
+// (Most Played), recently played (Last Played), or that already appear in
+// Rediscover, then trims to HomeYouMightLikeLimit.
+func applyYouMightLikeArtistFilters(
+	rows []dbq.ListYouMightLikeArtistsForUserRow,
+	mostPlayed []dbq.ListMostPlayedTracksForUserRow,
+	rediscover []dbq.ListRediscoverArtistsForUserRow,
+	lastPlayed []dbq.ListLastPlayedArtistsForUserRow,
+) []dbq.ListYouMightLikeArtistsForUserRow {
+	excluded := mostPlayedArtistIDs(mostPlayed)
+	for _, r := range rediscover {
+		excluded[r.Artist.ID] = struct{}{}
+	}
+	for _, r := range lastPlayed {
+		excluded[r.Artist.ID] = struct{}{}
+	}
+	out := make([]dbq.ListYouMightLikeArtistsForUserRow, 0, HomeYouMightLikeLimit)
+	for _, r := range rows {
+		if _, dup := excluded[r.Artist.ID]; dup {
+			continue
+		}
+		out = append(out, r)
+		if len(out) >= HomeYouMightLikeLimit {
+			break
+		}
+	}
+	return out
+}
+
 // mostPlayedAlbumIDs returns the set of album IDs whose tracks appear
 // in the Most Played row. Used to dedup Rediscover so it doesn't list
 // albums the user is actively spinning.

internal/recommendation/score.go

@@ -19,6 +19,11 @@ type ScoringInputs struct {
 	SkipCount            int        // play_events with was_skipped=true
 	ContextualMatchScore float64    // [0, 1]; 0 when no signal
 	SimilarityScore      float64    // [0, 1]; 0 when no signal (random fill)
+	// TasteMatchScore is the candidate's fit to the user's learned taste
+	// profile (#796 phase 2), in [-1, +1]: positive draws a track toward the
+	// user's taste, negative reflects passive avoidance, 0 when there's no
+	// profile signal (cold start / artist+tags absent from the profile).
+	TasteMatchScore float64
 }
 
 // ScoringWeights are the operator-tunable knobs. Defaults live in
@@ -31,6 +36,7 @@ type ScoringWeights struct {
 	JitterMagnitude  float64
 	ContextWeight    float64
 	SimilarityWeight float64
+	TasteWeight      float64
 }
 
 // Score computes the weighted-shuffle score per spec §6:
@@ -41,6 +47,7 @@ type ScoringWeights struct {
 //	      - skip_ratio * SkipPenalty
 //	      + contextual_match_score * ContextWeight
 //	      + similarity_score * SimilarityWeight
+//	      + taste_match_score * TasteWeight
 //	      + small_random_jitter
 //
 // Higher score = more likely to surface. rng is a function returning a
@@ -55,6 +62,7 @@ func Score(in ScoringInputs, w ScoringWeights, now time.Time, rng func() float64
 	s -= skipRatio(in.PlayCount, in.SkipCount) * w.SkipPenalty
 	s += in.ContextualMatchScore * w.ContextWeight
 	s += in.SimilarityScore * w.SimilarityWeight
+	s += in.TasteMatchScore * w.TasteWeight
 	s += (rng()*2 - 1) * w.JitterMagnitude
 	return s
 }

internal/recommendation/taste.go

@@ -0,0 +1,91 @@
+package recommendation
+
+import (
+	"context"
+	"math"
+
+	"github.com/jackc/pgx/v5/pgtype"
+
+	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
+)
+
+// Taste-match tuning. The taste profile (written by internal/taste) holds
+// signed, unbounded artist/tag weights; these scales squash them into a
+// bounded [-1, +1] match via tanh, so one outlier artist can't compress the
+// rest toward zero (as a per-user max-normalisation would). A weight at the
+// scale value maps to tanh(1) ≈ 0.76 — "clearly a preference."
+const (
+	tasteArtistScale  = 4.0
+	tasteTagScale     = 3.0
+	tasteArtistShare  = 0.7
+	tasteTagShare     = 0.3
+	tasteProfileLimit = 2000 // read cap; profiles are size-capped on write
+)
+
+// TasteProfile is the read-side view of a user's learned taste: signed
+// weights over artists and genre tags. The zero value (and any unknown
+// artist/tag) contributes 0, so cold-start users get no taste effect.
+type TasteProfile struct {
+	artists map[pgtype.UUID]float64
+	tags    map[string]float64
+}
+
+// LoadTasteProfile reads the user's taste profile from the taste_profile_*
+// tables (written daily by internal/taste). Returns an empty profile with no
+// error when the user has none.
+func LoadTasteProfile(ctx context.Context, q *dbq.Queries, userID pgtype.UUID) (TasteProfile, error) {
+	arts, err := q.ListTasteProfileArtistsForUser(ctx, dbq.ListTasteProfileArtistsForUserParams{
+		UserID: userID, Limit: tasteProfileLimit,
+	})
+	if err != nil {
+		return TasteProfile{}, err
+	}
+	tags, err := q.ListTasteProfileTagsForUser(ctx, dbq.ListTasteProfileTagsForUserParams{
+		UserID: userID, Limit: tasteProfileLimit,
+	})
+	if err != nil {
+		return TasteProfile{}, err
+	}
+	p := TasteProfile{
+		artists: make(map[pgtype.UUID]float64, len(arts)),
+		tags:    make(map[string]float64, len(tags)),
+	}
+	for _, a := range arts {
+		p.artists[a.ArtistID] = a.Weight
+	}
+	for _, t := range tags {
+		p.tags[t.Tag] = t.Weight
+	}
+	return p, nil
+}
+
+// Match scores a candidate track's fit to the profile in [-1, +1]: a blend of
+// the artist's taste weight and the average of its genre tags' weights, each
+// tanh-squashed. Absent artist/tags contribute 0.
+func (p TasteProfile) Match(artistID pgtype.UUID, genre *string) float64 {
+	a := math.Tanh(p.artists[artistID] / tasteArtistScale)
+
+	var tg float64
+	if genre != nil {
+		tags := splitGenres(*genre)
+		if len(tags) > 0 {
+			var sum float64
+			for _, t := range tags {
+				sum += p.tags[t]
+			}
+			tg = math.Tanh((sum / float64(len(tags))) / tasteTagScale)
+		}
+	}
+	return clampUnit(tasteArtistShare*a + tasteTagShare*tg)
+}
+
+// clampUnit constrains x to [-1, 1].
+func clampUnit(x float64) float64 {
+	if x < -1 {
+		return -1
+	}
+	if x > 1 {
+		return 1
+	}
+	return x
+}

internal/recommendation/taste_test.go

@@ -0,0 +1,109 @@
+package recommendation
+
+import (
+	"context"
+	"math"
+	"testing"
+	"time"
+
+	"github.com/jackc/pgx/v5/pgtype"
+
+	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
+)
+
+func uuidN(n byte) pgtype.UUID {
+	return pgtype.UUID{Bytes: [16]byte{15: n}, Valid: true}
+}
+
+func strPtr(s string) *string { return &s }
+
+func TestTasteProfile_Match(t *testing.T) {
+	loved := uuidN(1)
+	disliked := uuidN(2)
+	unknown := uuidN(3)
+	p := TasteProfile{
+		artists: map[pgtype.UUID]float64{loved: 8.0, disliked: -8.0},
+		tags:    map[string]float64{"Jazz": 6.0, "Noise": -6.0},
+	}
+
+	if m := p.Match(loved, strPtr("Jazz")); m <= 0.5 {
+		t.Errorf("loved artist + loved tag = %.3f, want strongly positive", m)
+	}
+	if m := p.Match(disliked, strPtr("Noise")); m >= -0.5 {
+		t.Errorf("disliked artist + disliked tag = %.3f, want strongly negative", m)
+	}
+	if m := p.Match(unknown, nil); m != 0 {
+		t.Errorf("unknown artist, no genre = %.3f, want 0", m)
+	}
+	// Artist dominates (0.7 share): loved artist with an unknown tag is still
+	// clearly positive.
+	if m := p.Match(loved, strPtr("Unheard")); m <= 0 {
+		t.Errorf("loved artist + unknown tag = %.3f, want positive", m)
+	}
+	// Output stays within [-1, 1] even with saturated inputs.
+	for _, a := range []pgtype.UUID{loved, disliked, unknown} {
+		m := p.Match(a, strPtr("Jazz"))
+		if m < -1 || m > 1 {
+			t.Errorf("Match out of [-1,1]: %.3f", m)
+		}
+	}
+}
+
+func TestTasteProfile_EmptyIsNeutral(t *testing.T) {
+	var p TasteProfile // zero value: nil maps
+	if m := p.Match(uuidN(1), strPtr("Jazz")); m != 0 {
+		t.Errorf("empty profile Match = %.3f, want 0 (cold start neutral)", m)
+	}
+}
+
+func TestScore_TasteTermAddsAndSubtracts(t *testing.T) {
+	now := time.Now()
+	zeroJitter := func() float64 { return 0.5 } // (0.5*2-1)=0 with any magnitude
+	w := ScoringWeights{TasteWeight: 2.0}       // all other weights 0
+
+	pos := Score(ScoringInputs{TasteMatchScore: 1.0}, w, now, zeroJitter)
+	if !almostEq(pos, 2.0) {
+		t.Errorf("positive taste: Score = %.3f, want 2.0", pos)
+	}
+	neg := Score(ScoringInputs{TasteMatchScore: -1.0}, w, now, zeroJitter)
+	if !almostEq(neg, -2.0) {
+		t.Errorf("negative taste: Score = %.3f, want -2.0 (demotes)", neg)
+	}
+	off := Score(ScoringInputs{TasteMatchScore: 1.0}, ScoringWeights{}, now, zeroJitter)
+	if !almostEq(off, 0.0) {
+		t.Errorf("TasteWeight 0: Score = %.3f, want 0 (no effect)", off)
+	}
+}
+
+func almostEq(a, b float64) bool { return math.Abs(a-b) < 1e-9 }
+
+// TestLoadTasteProfile_RoundTrip seeds taste_profile rows and verifies the
+// reader hydrates them into a profile that scores a matching track positively.
+func TestLoadTasteProfile_RoundTrip(t *testing.T) {
+	pool := newPool(t)
+	ctx := context.Background()
+	u := seedUser(t, pool, "taste-rt")
+	art := seedArtist(t, pool, "Loved Artist", "")
+
+	if _, err := pool.Exec(ctx,
+		`INSERT INTO taste_profile_artists (user_id, artist_id, weight) VALUES ($1, $2, $3)`,
+		u.ID, art.ID, 8.0); err != nil {
+		t.Fatalf("seed taste artist: %v", err)
+	}
+	if _, err := pool.Exec(ctx,
+		`INSERT INTO taste_profile_tags (user_id, tag, weight) VALUES ($1, $2, $3)`,
+		u.ID, "Jazz", 6.0); err != nil {
+		t.Fatalf("seed taste tag: %v", err)
+	}
+
+	p, err := LoadTasteProfile(ctx, dbq.New(pool), u.ID)
+	if err != nil {
+		t.Fatalf("load: %v", err)
+	}
+	if m := p.Match(art.ID, strPtr("Jazz")); m <= 0.5 {
+		t.Errorf("round-trip Match = %.3f, want strongly positive", m)
+	}
+	if m := p.Match(uuidN(9), nil); m != 0 {
+		t.Errorf("absent artist Match = %.3f, want 0", m)
+	}
+}

internal/taste/engagement.go

@@ -0,0 +1,81 @@
+// Package taste builds a persistent, decaying per-user taste profile (#796).
+// engagement.go is the pure core: it turns a single play's completion ratio
+// into a graded taste signal in [-1, +1], replacing the binary was_skipped
+// for learning purposes (was_skipped stays as-is for History display).
+package taste
+
+import "math"
+
+// EngagementParams tune the completion→engagement curve. All in [0,1] and
+// ordered HardSkip < NeutralCompletion < FullCompletion.
+type EngagementParams struct {
+	// HardSkip: completion at/below which a play is a strong reject (-1).
+	HardSkip float64
+	// NeutralCompletion: completion at which a play is neutral (0). Set low
+	// (~0.30) because people enjoy plenty of tracks they don't finish; only
+	// genuinely-early abandons read as negative.
+	NeutralCompletion float64
+	// FullCompletion: completion at/above which a play is a full positive
+	// (+1).
+	FullCompletion float64
+}
+
+// DefaultEngagementParams returns the tuned starting curve.
+func DefaultEngagementParams() EngagementParams {
+	return EngagementParams{HardSkip: 0.05, NeutralCompletion: 0.30, FullCompletion: 0.90}
+}
+
+// Engagement maps a play's completion ratio to a taste signal in [-1, +1]
+// via two linear ramps meeting at the neutral point:
+//
+//	completion <= HardSkip            → -1
+//	HardSkip   < c < Neutral          → ramp -1 → 0
+//	Neutral    <= c < Full            → ramp 0 → +1
+//	completion >= Full                → +1
+//
+// Completion is clamped to [0,1]. Degenerate params (non-increasing
+// thresholds) collapse the affected ramp to its endpoint rather than
+// dividing by zero.
+func Engagement(completion float64, p EngagementParams) float64 {
+	c := clamp01(completion)
+	if c <= p.HardSkip {
+		return -1
+	}
+	if c < p.NeutralCompletion {
+		span := p.NeutralCompletion - p.HardSkip
+		if span <= 0 {
+			return 0
+		}
+		return -1 + (c-p.HardSkip)/span
+	}
+	if c < p.FullCompletion {
+		span := p.FullCompletion - p.NeutralCompletion
+		if span <= 0 {
+			return 1
+		}
+		return (c - p.NeutralCompletion) / span
+	}
+	return 1
+}
+
+// decay is the exponential time-decay applied to a play's engagement:
+// 1.0 at age 0, 0.5 at age == halfLifeDays. Negative ages clamp to 0.
+func decay(ageDays, halfLifeDays float64) float64 {
+	if ageDays < 0 {
+		ageDays = 0
+	}
+	if halfLifeDays <= 0 {
+		return 1
+	}
+	return math.Exp(-math.Ln2 * ageDays / halfLifeDays)
+}
+
+func clamp01(x float64) float64 {
+	if x < 0 {
+		return 0
+	}
+	if x > 1 {
+		return 1
+	}
+	return x
+}

internal/taste/engagement_test.go

@@ -0,0 +1,75 @@
+package taste
+
+import (
+	"math"
+	"testing"
+)
+
+func almostEqual(a, b float64) bool { return math.Abs(a-b) < 1e-9 }
+
+func TestEngagement_Curve(t *testing.T) {
+	p := DefaultEngagementParams() // HardSkip 0.05, Neutral 0.30, Full 0.90
+	cases := []struct {
+		name       string
+		completion float64
+		want       float64
+	}{
+		{"instant skip", 0.00, -1},
+		{"at hard-skip boundary", 0.05, -1},
+		{"neg ramp midpoint", 0.175, -0.5}, // (0.175-0.05)/(0.30-0.05)=0.5 → -0.5
+		{"neutral point", 0.30, 0},
+		{"pos ramp midpoint", 0.60, 0.5}, // (0.60-0.30)/(0.90-0.30)=0.5
+		{"at full boundary", 0.90, 1},
+		{"complete", 1.00, 1},
+		{"clamp above 1", 1.50, 1},
+		{"clamp below 0", -0.5, -1},
+	}
+	for _, c := range cases {
+		if got := Engagement(c.completion, p); !almostEqual(got, c.want) {
+			t.Errorf("%s: Engagement(%.3f) = %.4f, want %.4f", c.name, c.completion, got, c.want)
+		}
+	}
+}
+
+func TestEngagement_MonotonicNonDecreasing(t *testing.T) {
+	p := DefaultEngagementParams()
+	prev := math.Inf(-1)
+	for i := 0; i <= 100; i++ {
+		c := float64(i) / 100
+		got := Engagement(c, p)
+		if got < prev-1e-9 {
+			t.Fatalf("engagement decreased at completion %.2f: %.4f < %.4f", c, got, prev)
+		}
+		prev = got
+	}
+}
+
+func TestEngagement_DegenerateParamsStayInRange(t *testing.T) {
+	// Non-increasing thresholds must collapse ramps (no divide-by-zero) and
+	// still produce a value in [-1, 1].
+	p := EngagementParams{HardSkip: 0.5, NeutralCompletion: 0.5, FullCompletion: 0.5}
+	for _, c := range []float64{0, 0.25, 0.5, 0.75, 1} {
+		got := Engagement(c, p)
+		if got < -1 || got > 1 {
+			t.Errorf("Engagement(%.2f) = %.3f out of [-1,1]", c, got)
+		}
+	}
+}
+
+func TestDecay_HalfLife(t *testing.T) {
+	if got := decay(0, 75); !almostEqual(got, 1) {
+		t.Errorf("decay(0) = %.4f, want 1", got)
+	}
+	if got := decay(75, 75); !almostEqual(got, 0.5) {
+		t.Errorf("decay(halflife) = %.4f, want 0.5", got)
+	}
+	if got := decay(150, 75); !almostEqual(got, 0.25) {
+		t.Errorf("decay(2*halflife) = %.4f, want 0.25", got)
+	}
+	if got := decay(-5, 75); !almostEqual(got, 1) {
+		t.Errorf("decay(negative age) = %.4f, want 1 (clamped)", got)
+	}
+	if got := decay(10, 0); !almostEqual(got, 1) {
+		t.Errorf("decay(halflife=0) = %.4f, want 1 (guarded)", got)
+	}
+}

internal/taste/profile.go

@@ -0,0 +1,267 @@
+// profile.go assembles the per-user taste profile from graded play
+// engagement (decayed over time) plus explicit-like bonuses, and
+// atomic-replaces the taste_profile_* tables. Phase 1 only builds the
+// object; candidate sourcing + scoring consume it in phase 2.
+package taste
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"log/slog"
+	"sort"
+	"strings"
+
+	"github.com/jackc/pgx/v5/pgtype"
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
+)
+
+// Config holds the operator-tunable knobs. DefaultConfig supplies tuned
+// starting values; wiring these into the server RecommendationConfig is a
+// later follow-up (phase 1 uses the defaults).
+type Config struct {
+	Engagement EngagementParams
+
+	// HalfLifeDays: a play's engagement halves every this-many days, so the
+	// profile tracks drift (recent behaviour dominates). WindowDays bounds
+	// the plays fetched — beyond ~3 half-lives the decayed contribution is
+	// negligible, so older plays are skipped for cost, not correctness.
+	HalfLifeDays float64
+	WindowDays   float64
+
+	// Explicit-like bonuses. Likes stay the strongest single positive.
+	ArtistLikeBonus float64
+	TrackLikeBonus  float64
+	TagLikeBonus    float64
+
+	// ArtistFloor / TagFloor clamp how negative a single entity's weight may
+	// go. Aggregation already protects an artist the user likes (one skip
+	// nets out against many good plays); the floor additionally bounds the
+	// magnitude so a heavily-skipped entity can't dominate as an extreme
+	// negative.
+	ArtistFloor float64
+	TagFloor    float64
+
+	// WeightEpsilon: entities with |weight| below this are dropped as noise.
+	WeightEpsilon float64
+
+	// Size caps (guard rails for pathological libraries). Persist the top
+	// MaxArtists by weight plus the most-negative MaxNegArtists; same for tags.
+	MaxArtists    int
+	MaxNegArtists int
+	MaxTags       int
+	MaxNegTags    int
+}
+
+// DefaultConfig returns the tuned starting configuration.
+func DefaultConfig() Config {
+	return Config{
+		Engagement:      DefaultEngagementParams(),
+		HalfLifeDays:    75,
+		WindowDays:      270,
+		ArtistLikeBonus: 3.0,
+		TrackLikeBonus:  1.0,
+		TagLikeBonus:    0.5,
+		ArtistFloor:     -3.0,
+		TagFloor:        -3.0,
+		WeightEpsilon:   0.05,
+		MaxArtists:      500,
+		MaxNegArtists:   150,
+		MaxTags:         200,
+		MaxNegTags:      60,
+	}
+}
+
+// BuildTasteProfile recomputes and atomic-replaces the user's taste profile.
+// Reads the decay-windowed play engagement + explicit likes, accumulates
+// signed artist/tag weights, applies floor damping + size caps, and persists.
+// Self-contained transaction for the replace. Returns an error only on a
+// fatal DB failure; the daily caller logs and proceeds to playlist building
+// regardless (best-effort).
+//
+// The decay reference time is the database clock (age is computed in SQL via
+// now()), so no Go-side timestamp is threaded here; a phase-3 context model
+// that needs a pinned reference time would add one.
+func BuildTasteProfile(
+	ctx context.Context, pool *pgxpool.Pool, logger *slog.Logger,
+	userID pgtype.UUID, cfg Config,
+) error {
+	q := dbq.New(pool)
+
+	artistW, tagW, err := accumulate(ctx, q, userID, cfg)
+	if err != nil {
+		return err
+	}
+	applyFloor(artistW, cfg.ArtistFloor)
+	applyFloor(tagW, cfg.TagFloor)
+
+	artists := rankWeighted(artistW, cfg.WeightEpsilon, cfg.MaxArtists, cfg.MaxNegArtists, uuidLess)
+	tags := rankWeighted(tagW, cfg.WeightEpsilon, cfg.MaxTags, cfg.MaxNegTags,
+		func(a, b string) bool { return a < b })
+
+	if err := persist(ctx, pool, userID, artists, tags); err != nil {
+		return err
+	}
+	logger.Debug("taste: profile rebuilt",
+		"user_id", uuidString(userID), "artists", len(artists), "tags", len(tags))
+	return nil
+}
+
+// accumulate sums decayed play engagement and like bonuses into artist/tag
+// weight maps.
+func accumulate(
+	ctx context.Context, q *dbq.Queries, userID pgtype.UUID, cfg Config,
+) (map[pgtype.UUID]float64, map[string]float64, error) {
+	plays, err := q.ListPlayEngagementInputsForUser(ctx, dbq.ListPlayEngagementInputsForUserParams{
+		UserID:  userID,
+		Column2: cfg.WindowDays,
+	})
+	if err != nil {
+		return nil, nil, fmt.Errorf("taste: load play engagement: %w", err)
+	}
+	artistW := make(map[pgtype.UUID]float64)
+	tagW := make(map[string]float64)
+	for _, p := range plays {
+		e := Engagement(p.Completion, cfg.Engagement) * decay(p.AgeDays, cfg.HalfLifeDays)
+		artistW[p.ArtistID] += e
+		for _, tag := range splitGenres(p.Genre) {
+			tagW[tag] += e
+		}
+	}
+
+	likedTracks, err := q.ListLikedTrackTasteInputsForUser(ctx, userID)
+	if err != nil {
+		return nil, nil, fmt.Errorf("taste: load liked tracks: %w", err)
+	}
+	for _, lt := range likedTracks {
+		artistW[lt.ArtistID] += cfg.TrackLikeBonus
+		for _, tag := range splitGenres(lt.Genre) {
+			tagW[tag] += cfg.TagLikeBonus
+		}
+	}
+
+	likedArtists, err := q.ListLikedArtistIDsForUser(ctx, userID)
+	if err != nil {
+		return nil, nil, fmt.Errorf("taste: load liked artists: %w", err)
+	}
+	for _, aid := range likedArtists {
+		artistW[aid] += cfg.ArtistLikeBonus
+	}
+	return artistW, tagW, nil
+}
+
+// persist atomic-replaces the user's profile rows inside one transaction.
+func persist(
+	ctx context.Context, pool *pgxpool.Pool, userID pgtype.UUID,
+	artists []weighted[pgtype.UUID], tags []weighted[string],
+) error {
+	tx, err := pool.Begin(ctx)
+	if err != nil {
+		return fmt.Errorf("taste: begin tx: %w", err)
+	}
+	defer func() { _ = tx.Rollback(ctx) }()
+	qtx := dbq.New(tx)
+
+	if err := qtx.DeleteTasteProfileArtistsForUser(ctx, userID); err != nil {
+		return fmt.Errorf("taste: delete artists: %w", err)
+	}
+	for _, a := range artists {
+		if err := qtx.InsertTasteProfileArtist(ctx, dbq.InsertTasteProfileArtistParams{
+			UserID: userID, ArtistID: a.Key, Weight: a.Weight,
+		}); err != nil {
+			return fmt.Errorf("taste: insert artist: %w", err)
+		}
+	}
+	if err := qtx.DeleteTasteProfileTagsForUser(ctx, userID); err != nil {
+		return fmt.Errorf("taste: delete tags: %w", err)
+	}
+	for _, t := range tags {
+		if err := qtx.InsertTasteProfileTag(ctx, dbq.InsertTasteProfileTagParams{
+			UserID: userID, Tag: t.Key, Weight: t.Weight,
+		}); err != nil {
+			return fmt.Errorf("taste: insert tag: %w", err)
+		}
+	}
+	if err := tx.Commit(ctx); err != nil {
+		return fmt.Errorf("taste: commit: %w", err)
+	}
+	return nil
+}
+
+// weighted is a key with its signed taste weight.
+type weighted[K comparable] struct {
+	Key    K
+	Weight float64
+}
+
+// rankWeighted drops near-zero entries, sorts by weight DESC (ties broken by
+// keyLess for determinism), and caps to the top topN plus the most-negative
+// botN so both ends of the signal survive without unbounded table growth.
+func rankWeighted[K comparable](
+	m map[K]float64, eps float64, topN, botN int, keyLess func(a, b K) bool,
+) []weighted[K] {
+	all := make([]weighted[K], 0, len(m))
+	for k, w := range m {
+		if w >= eps || w <= -eps {
+			all = append(all, weighted[K]{Key: k, Weight: w})
+		}
+	}
+	sort.Slice(all, func(i, j int) bool {
+		if all[i].Weight != all[j].Weight {
+			return all[i].Weight > all[j].Weight
+		}
+		return keyLess(all[i].Key, all[j].Key)
+	})
+	if topN+botN >= len(all) {
+		return all
+	}
+	out := make([]weighted[K], 0, topN+botN)
+	out = append(out, all[:topN]...)
+	out = append(out, all[len(all)-botN:]...)
+	return out
+}
+
+// applyFloor clamps every weight in m up to floor (no entity goes more
+// negative than the floor).
+func applyFloor[K comparable](m map[K]float64, floor float64) {
+	for k, w := range m {
+		if w < floor {
+			m[k] = floor
+		}
+	}
+}
+
+// uuidLess orders two UUIDs by raw bytes (deterministic tie-break).
+func uuidLess(a, b pgtype.UUID) bool {
+	return bytes.Compare(a.Bytes[:], b.Bytes[:]) < 0
+}
+
+// uuidString renders a pgtype.UUID canonically for log lines.
+func uuidString(u pgtype.UUID) string {
+	if !u.Valid {
+		return "<nil>"
+	}
+	return fmt.Sprintf("%x-%x-%x-%x-%x",
+		u.Bytes[0:4], u.Bytes[4:6], u.Bytes[6:8], u.Bytes[8:10], u.Bytes[10:16])
+}
+
+// splitGenres splits a track's denormalized genre string on the common
+// multi-genre delimiters, trimming whitespace and dropping empties. Mirrors
+// the recommendation package's splitter (kept local to avoid a dependency).
+func splitGenres(genre *string) []string {
+	if genre == nil || *genre == "" {
+		return nil
+	}
+	parts := strings.FieldsFunc(*genre, func(r rune) bool {
+		return r == ';' || r == ','
+	})
+	out := make([]string, 0, len(parts))
+	for _, p := range parts {
+		if p = strings.TrimSpace(p); p != "" {
+			out = append(out, p)
+		}
+	}
+	return out
+}

internal/taste/profile_db_test.go

@@ -0,0 +1,249 @@
+package taste
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"log/slog"
+	"os"
+	"path/filepath"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgtype"
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"git.fabledsword.com/bvandeusen/minstrel/internal/db"
+	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
+	"git.fabledsword.com/bvandeusen/minstrel/internal/dbtest"
+)
+
+var seedCounter uint64
+
+func discardLogger() *slog.Logger { return slog.New(slog.NewTextHandler(io.Discard, nil)) }
+
+func newPool(t *testing.T) *pgxpool.Pool {
+	t.Helper()
+	if testing.Short() {
+		t.Skip("skipping integration test in -short mode")
+	}
+	dsn := os.Getenv("MINSTREL_TEST_DATABASE_URL")
+	if dsn == "" {
+		t.Skip("MINSTREL_TEST_DATABASE_URL not set")
+	}
+	if err := db.Migrate(dsn, discardLogger()); err != nil {
+		t.Fatalf("migrate: %v", err)
+	}
+	pool, err := pgxpool.New(context.Background(), dsn)
+	if err != nil {
+		t.Fatalf("pool: %v", err)
+	}
+	t.Cleanup(pool.Close)
+	dbtest.ResetDB(t, pool)
+	return pool
+}
+
+func seedUser(t *testing.T, pool *pgxpool.Pool, name string) dbq.User {
+	t.Helper()
+	u, err := dbq.New(pool).CreateUser(context.Background(), dbq.CreateUserParams{
+		Username: dbtest.TestUserPrefix + name, PasswordHash: "x",
+		ApiToken: name + "-token", IsAdmin: false,
+	})
+	if err != nil {
+		t.Fatalf("seed user: %v", err)
+	}
+	return u
+}
+
+func seedArtist(t *testing.T, pool *pgxpool.Pool, name string) dbq.Artist {
+	t.Helper()
+	a, err := dbq.New(pool).UpsertArtist(context.Background(), dbq.UpsertArtistParams{
+		Name: name, SortName: name,
+	})
+	if err != nil {
+		t.Fatalf("seed artist: %v", err)
+	}
+	return a
+}
+
+// seedTrack creates an album + track under the given artist with a genre.
+func seedTrack(t *testing.T, pool *pgxpool.Pool, artistID pgtype.UUID, genre string) dbq.Track {
+	t.Helper()
+	q := dbq.New(pool)
+	n := atomic.AddUint64(&seedCounter, 1)
+	al, err := q.UpsertAlbum(context.Background(), dbq.UpsertAlbumParams{
+		Title: fmt.Sprintf("Album %d", n), SortTitle: fmt.Sprintf("Album %d", n), ArtistID: artistID,
+	})
+	if err != nil {
+		t.Fatalf("seed album: %v", err)
+	}
+	g := genre
+	tk, err := q.UpsertTrack(context.Background(), dbq.UpsertTrackParams{
+		Title: fmt.Sprintf("Track %d", n), AlbumID: al.ID, ArtistID: artistID,
+		DurationMs: 200000, FilePath: filepath.Join(t.TempDir(), fmt.Sprintf("t%d.mp3", n)),
+		FileSize: 100, FileFormat: "mp3", Genre: &g,
+	})
+	if err != nil {
+		t.Fatalf("seed track: %v", err)
+	}
+	return tk
+}
+
+// seedPlay inserts a play with an explicit completion_ratio at startedAt.
+func seedPlay(t *testing.T, pool *pgxpool.Pool, userID, trackID pgtype.UUID, startedAt time.Time, completion float64) {
+	t.Helper()
+	_, err := pool.Exec(context.Background(), `
+		WITH s AS (
+			INSERT INTO play_sessions (user_id, started_at, last_event_at)
+			VALUES ($1, $3, $3) RETURNING id
+		)
+		INSERT INTO play_events (user_id, track_id, session_id, started_at, completion_ratio, was_skipped)
+		SELECT $1, $2, s.id, $3, $4, false FROM s
+	`, userID, trackID, startedAt, completion)
+	if err != nil {
+		t.Fatalf("seed play: %v", err)
+	}
+}
+
+func artistWeight(t *testing.T, pool *pgxpool.Pool, userID, artistID pgtype.UUID) (float64, bool) {
+	t.Helper()
+	var w float64
+	err := pool.QueryRow(context.Background(),
+		`SELECT weight FROM taste_profile_artists WHERE user_id = $1 AND artist_id = $2`,
+		userID, artistID).Scan(&w)
+	if errors.Is(err, pgx.ErrNoRows) {
+		return 0, false
+	}
+	if err != nil {
+		t.Fatalf("artist weight: %v", err)
+	}
+	return w, true
+}
+
+func tagWeight(t *testing.T, pool *pgxpool.Pool, userID pgtype.UUID, tag string) (float64, bool) {
+	t.Helper()
+	var w float64
+	err := pool.QueryRow(context.Background(),
+		`SELECT weight FROM taste_profile_tags WHERE user_id = $1 AND tag = $2`,
+		userID, tag).Scan(&w)
+	if errors.Is(err, pgx.ErrNoRows) {
+		return 0, false
+	}
+	if err != nil {
+		t.Fatalf("tag weight: %v", err)
+	}
+	return w, true
+}
+
+// TestBuildTasteProfile_PositiveVsNegative: a completed-track artist earns a
+// positive weight; an early-skipped artist earns a negative one. Genre tags
+// follow the same sign.
+func TestBuildTasteProfile_PositiveVsNegative(t *testing.T) {
+	pool := newPool(t)
+	now := time.Now().UTC()
+	u := seedUser(t, pool, "tp1")
+
+	loved := seedArtist(t, pool, "Loved")
+	lovedTrack := seedTrack(t, pool, loved.ID, "Rock")
+	skipped := seedArtist(t, pool, "Skipped")
+	skippedTrack := seedTrack(t, pool, skipped.ID, "Noise")
+	for i := 0; i < 3; i++ {
+		seedPlay(t, pool, u.ID, lovedTrack.ID, now.Add(-time.Duration(i+1)*time.Hour), 1.0)
+		seedPlay(t, pool, u.ID, skippedTrack.ID, now.Add(-time.Duration(i+1)*time.Hour), 0.02)
+	}
+
+	if err := BuildTasteProfile(context.Background(), pool, discardLogger(), u.ID, DefaultConfig()); err != nil {
+		t.Fatalf("build: %v", err)
+	}
+
+	lw, ok := artistWeight(t, pool, u.ID, loved.ID)
+	if !ok || lw <= 0 {
+		t.Errorf("loved artist weight = %.3f (present=%v), want > 0", lw, ok)
+	}
+	sw, ok := artistWeight(t, pool, u.ID, skipped.ID)
+	if !ok || sw >= 0 {
+		t.Errorf("skipped artist weight = %.3f (present=%v), want < 0", sw, ok)
+	}
+	if rw, ok := tagWeight(t, pool, u.ID, "Rock"); !ok || rw <= 0 {
+		t.Errorf("Rock tag weight = %.3f (present=%v), want > 0", rw, ok)
+	}
+}
+
+// TestBuildTasteProfile_AggregationProtectsArtist: one early-skip among many
+// completed plays must NOT make a loved artist net-negative (the user's
+// concern that a track-dislike shouldn't tank the artist).
+func TestBuildTasteProfile_AggregationProtectsArtist(t *testing.T) {
+	pool := newPool(t)
+	now := time.Now().UTC()
+	u := seedUser(t, pool, "tp2")
+	fav := seedArtist(t, pool, "Fav")
+
+	for i := 0; i < 4; i++ {
+		tk := seedTrack(t, pool, fav.ID, "Indie")
+		seedPlay(t, pool, u.ID, tk.ID, now.Add(-time.Duration(i+1)*time.Hour), 1.0)
+		seedPlay(t, pool, u.ID, tk.ID, now.Add(-time.Duration(i+5)*time.Hour), 0.95)
+	}
+	// One early-skipped track by the same artist.
+	skipTrack := seedTrack(t, pool, fav.ID, "Indie")
+	seedPlay(t, pool, u.ID, skipTrack.ID, now.Add(-2*time.Hour), 0.02)
+
+	if err := BuildTasteProfile(context.Background(), pool, discardLogger(), u.ID, DefaultConfig()); err != nil {
+		t.Fatalf("build: %v", err)
+	}
+	w, ok := artistWeight(t, pool, u.ID, fav.ID)
+	if !ok || w <= 0 {
+		t.Errorf("fav artist weight = %.3f (present=%v), want > 0 despite one skip", w, ok)
+	}
+}
+
+// TestBuildTasteProfile_ArtistLikeBonus: an explicitly-liked artist with no
+// plays still earns a positive weight from the like bonus.
+func TestBuildTasteProfile_ArtistLikeBonus(t *testing.T) {
+	pool := newPool(t)
+	u := seedUser(t, pool, "tp3")
+	liked := seedArtist(t, pool, "LikedOnly")
+	if _, err := pool.Exec(context.Background(),
+		`INSERT INTO general_likes_artists (user_id, artist_id) VALUES ($1, $2)`,
+		u.ID, liked.ID); err != nil {
+		t.Fatalf("seed artist like: %v", err)
+	}
+
+	if err := BuildTasteProfile(context.Background(), pool, discardLogger(), u.ID, DefaultConfig()); err != nil {
+		t.Fatalf("build: %v", err)
+	}
+	w, ok := artistWeight(t, pool, u.ID, liked.ID)
+	if !ok || w <= 0 {
+		t.Errorf("liked-only artist weight = %.3f (present=%v), want > 0 from like bonus", w, ok)
+	}
+}
+
+// TestBuildTasteProfile_AtomicReplace: a second build replaces, not appends.
+func TestBuildTasteProfile_AtomicReplace(t *testing.T) {
+	pool := newPool(t)
+	ctx := context.Background()
+	now := time.Now().UTC()
+	u := seedUser(t, pool, "tp4")
+	a := seedArtist(t, pool, "A")
+	tk := seedTrack(t, pool, a.ID, "Rock")
+	seedPlay(t, pool, u.ID, tk.ID, now.Add(-time.Hour), 1.0)
+
+	count := func() int {
+		var n int
+		if err := pool.QueryRow(ctx,
+			`SELECT count(*) FROM taste_profile_artists WHERE user_id = $1`, u.ID).Scan(&n); err != nil {
+			t.Fatalf("count: %v", err)
+		}
+		return n
+	}
+	for i := 0; i < 2; i++ {
+		if err := BuildTasteProfile(ctx, pool, discardLogger(), u.ID, DefaultConfig()); err != nil {
+			t.Fatalf("build %d: %v", i, err)
+		}
+	}
+	if got := count(); got != 1 {
+		t.Errorf("artist rows after two builds = %d, want 1 (atomic replace)", got)
+	}
+}

internal/taste/profile_test.go

@@ -0,0 +1,94 @@
+package taste
+
+import (
+	"testing"
+
+	"github.com/jackc/pgx/v5/pgtype"
+)
+
+func strLess(a, b string) bool { return a < b }
+
+func TestRankWeighted_DropsEpsilonAndSortsDesc(t *testing.T) {
+	m := map[string]float64{"a": 3.0, "b": 1.0, "tiny": 0.01, "d": -2.0}
+	got := rankWeighted(m, 0.05, 10, 10, strLess)
+	if len(got) != 3 {
+		t.Fatalf("len = %d, want 3 (tiny dropped by epsilon)", len(got))
+	}
+	wantOrder := []string{"a", "b", "d"} // 3, 1, -2 descending
+	for i, w := range wantOrder {
+		if got[i].Key != w {
+			t.Errorf("pos %d = %q, want %q", i, got[i].Key, w)
+		}
+	}
+}
+
+func TestRankWeighted_CapsTopAndBottom(t *testing.T) {
+	m := map[string]float64{"e5": 5, "e4": 4, "e3": 3, "e2": 2, "e1": 1}
+	got := rankWeighted(m, 0.0, 1, 1, strLess) // top 1 + bottom 1
+	if len(got) != 2 {
+		t.Fatalf("len = %d, want 2", len(got))
+	}
+	if got[0].Key != "e5" || got[1].Key != "e1" {
+		t.Errorf("got [%s,%s], want [e5,e1]", got[0].Key, got[1].Key)
+	}
+}
+
+func TestRankWeighted_DeterministicTieBreak(t *testing.T) {
+	m := map[string]float64{"z": 1.0, "a": 1.0, "m": 1.0}
+	got := rankWeighted(m, 0.0, 10, 10, strLess)
+	// Equal weights → ordered by keyLess (string asc): a, m, z.
+	want := []string{"a", "m", "z"}
+	for i, w := range want {
+		if got[i].Key != w {
+			t.Errorf("tie-break pos %d = %q, want %q", i, got[i].Key, w)
+		}
+	}
+}
+
+func TestApplyFloor_ClampsNegatives(t *testing.T) {
+	m := map[string]float64{"a": -5, "b": 2, "c": -1}
+	applyFloor(m, -3)
+	if m["a"] != -3 {
+		t.Errorf("a = %.1f, want -3 (floored)", m["a"])
+	}
+	if m["b"] != 2 {
+		t.Errorf("b = %.1f, want 2 (untouched)", m["b"])
+	}
+	if m["c"] != -1 {
+		t.Errorf("c = %.1f, want -1 (above floor)", m["c"])
+	}
+}
+
+func TestSplitGenres(t *testing.T) {
+	mk := func(s string) *string { return &s }
+	cases := []struct {
+		in   *string
+		want []string
+	}{
+		{nil, nil},
+		{mk(""), nil},
+		{mk("Rock"), []string{"Rock"}},
+		{mk(" Rock "), []string{"Rock"}},
+		{mk("Rock; Pop, Jazz"), []string{"Rock", "Pop", "Jazz"}},
+	}
+	for _, c := range cases {
+		got := splitGenres(c.in)
+		if len(got) != len(c.want) {
+			t.Errorf("splitGenres(%v) len = %d, want %d", c.in, len(got), len(c.want))
+			continue
+		}
+		for i := range got {
+			if got[i] != c.want[i] {
+				t.Errorf("splitGenres(%v)[%d] = %q, want %q", c.in, i, got[i], c.want[i])
+			}
+		}
+	}
+}
+
+func TestUuidLess_Orders(t *testing.T) {
+	a := pgtype.UUID{Bytes: [16]byte{1}, Valid: true}
+	b := pgtype.UUID{Bytes: [16]byte{2}, Valid: true}
+	if !uuidLess(a, b) || uuidLess(b, a) {
+		t.Error("uuidLess byte ordering wrong")
+	}
+}