fix: address code review findings

- Fix duplicate Telegram notifications: SyncArtistDiscography no longer wipes
  notifications_sent for the whole artist on every cache-miss re-sync; only
  markers for releases that disappear are pruned (FK-safe via INSERT OR REPLACE
  + rgid NOT IN (...)).
- Cache empty MusicBrainz discographies via a new artist_settings.last_synced
  column (migration 009) so zero-release artists honor the TTL instead of being
  re-fetched every cycle.
- Wire the Web UI server and Telegram notifier scheduler into main.run/NewApp.
- Guard startPeriodicSync against overlapping syncs with a done-channel slot.
- Add server.public_url config; NewServerWithConfig derives reachable links
  and no longer advertises the 0.0.0.0 bind address.
- Web handlers: use scanner.ScanArtist per artist, drop always-false
  releaseIgnored lookup and dead endsWith, thread configured threshold.
- Limit :memory: DB pool to one connection so migrations and queries share the
  same in-memory store.

README.md

@@ -82,6 +82,11 @@ server:
   port: 8080
   username: "admin"
   password: "CHANGE_ME"
+  # Externally-reachable base URL for links in Telegram digests (e.g. behind a
+  # reverse proxy). If omitted, links are derived from host:port — but when host
+  # is 0.0.0.0 (the unspecified bind address) no link is emitted, since it is
+  # not reachable from outside the host.
+  public_url: "https://naviwatcher.example.com"
 
 navidrome:
   url: "http://localhost:4533"
@@ -203,6 +208,10 @@ server:
   port: 8080
   username: "admin"
   password: "CHANGE_ME"
+  # Внешний базовый URL для ссылок в дайджестах Telegram (напр. за обратным прокси).
+  # Если не задан, ссылки строятся из host:port — но при host 0.0.0.0 (несpecificированный
+  # адрес привязки) ссылка не генерируется, так как недоступна снаружи хоста.
+  public_url: "https://naviwatcher.example.com"
 
 navidrome:
   url: "http://localhost:4533"

cmd/naviwatcher/datastore_smoke_test.go

@@ -106,7 +106,7 @@ func TestDataFlowSmoke(t *testing.T) {
 		Username: "admin",
 		Password: "secret",
 	}
-	srv := web.NewServer(srvCfg, db, "http://localhost:8080")
+	srv := web.NewServer(srvCfg, db, "http://localhost:8080", 0)
 
 	// Unauthenticated -> 401.
 	rec := httptest.NewRecorder()

cmd/naviwatcher/main.go

@@ -14,7 +14,9 @@ import (
 	"naviwatcher/internal/database"
 	"naviwatcher/internal/musicbrainz"
 	"naviwatcher/internal/navidrome"
+	"naviwatcher/internal/notifier"
 	"naviwatcher/internal/scanner"
+	"naviwatcher/internal/web"
 )
 
 // App holds all application dependencies for clean shutdown and testability.
@@ -23,6 +25,8 @@ type App struct {
 	db       *database.DB
 	mbClient *musicbrainz.MusicBrainzClient
 	ndClient *navidrome.NavidromeClient
+	web      *web.Server
+	sender   notifier.Sender
 
 	// syncFn, when non-nil, replaces the real syncAndScan call in
 	// startPeriodicSync so tests can observe the loop without live clients.
@@ -94,11 +98,23 @@ func NewApp(ctx context.Context, cfg *config.Config, dbPath string) (*App, error
 		return nil, fmt.Errorf("failed to initialize navidrome client: %w", err)
 	}
 
+	// Build the Web UI dashboard server (not started until run).
+	webServer := web.NewServerWithConfig(cfg, db)
+
+	// Build the notifier sender. A nil sender is fine when Telegram is disabled;
+	// the scheduler is no-op-safe and the web UI needs no sender.
+	var sender notifier.Sender
+	if cfg.Telegram.Enabled {
+		sender = notifier.NewTelegramSender(cfg.Telegram)
+	}
+
 	return &App{
 		cfg:      cfg,
 		db:       db,
 		mbClient: mbClient,
 		ndClient: ndClient,
+		web:      webServer,
+		sender:   sender,
 	}, nil
 }
 
@@ -107,10 +123,6 @@ func (a *App) Close() {
 	if a.mbClient != nil {
 		a.mbClient.Close()
 	}
-	if a.ndClient != nil {
-		// NavidromeClient holds a stateless subsonic client; nothing to close
-		// beyond releasing idle connections tracked by the MusicBrainz client.
-	}
 	if a.db != nil {
 		if err := a.db.Close(); err != nil {
 			log.Printf("Error closing database: %v", err)
@@ -120,9 +132,7 @@ func (a *App) Close() {
 
 func (a *App) run(ctx context.Context) error {
 	// Run an immediate sync+scan so the service produces results without
-	// waiting a full interval, then kick off the periodic loop goroutine.
-	// Business logic added in later tasks (notifier, web server) will be
-	// wired as additional goroutines below.
+	// waiting a full interval.
 	if err := a.doSync(ctx); err != nil {
 		if ctx.Err() != nil {
 			return nil
@@ -130,6 +140,24 @@ func (a *App) run(ctx context.Context) error {
 		log.Printf("Initial sync+scan failed: %v", err)
 	}
 
+	// Start the Web UI dashboard in its own goroutine; it serves until ctx is
+	// cancelled, then shuts down gracefully.
+	if a.web != nil {
+		go func() {
+			if err := a.web.Start(ctx); err != nil {
+				if ctx.Err() != nil {
+					return
+				}
+				log.Printf("Web UI server stopped with error: %v", err)
+			}
+		}()
+	}
+
+	// Start the Telegram notifier scheduler. It is no-op-safe when Telegram is
+	// disabled (sender nil / enabled false), so always calling it is safe.
+	a.startNotifier(ctx)
+
+	// Kick off the periodic sync+scan loop goroutine.
 	a.startPeriodicSync(ctx)
 
 	<-ctx.Done()
@@ -173,21 +201,51 @@ func (a *App) syncAndScan(ctx context.Context) error {
 	return nil
 }
 
+// startNotifier wires the Telegram digest scheduler. The scheduler is
+// no-op-safe (returns without starting when disabled or sender is nil), so it
+// is always safe to call. The base URL for dashboard links comes from the
+// server's configured public_url.
+func (a *App) startNotifier(ctx context.Context) {
+	if !a.cfg.Telegram.Enabled {
+		return
+	}
+	schedule, err := notifier.NewCronSchedule(a.cfg.Telegram.CronSchedule)
+	if err != nil {
+		log.Printf("Notifier schedule invalid (%q): %v; notifier disabled", a.cfg.Telegram.CronSchedule, err)
+		return
+	}
+	uiBaseURL := a.cfg.Server.PublicURL
+	notifier.StartScheduler(ctx, true, schedule, func(ctx context.Context) error {
+		_, err := notifier.NotifyOnce(ctx, a.db, a.sender, a.cfg.Telegram, uiBaseURL)
+		return err
+	}, nil)
+}
+
 // startPeriodicSync runs syncAndScan on a ticker at cfg.Sync.Interval. It
-// blocks until ctx is cancelled, then returns cleanly. Each tick runs in its
-// own goroutine so a slow sync does not block the ticker; a fresh interval is
-// still scheduled regardless.
+// blocks until ctx is cancelled, then returns cleanly. Each tick spawns a
+// goroutine so a slow sync does not block the ticker, but a new sync is
+// skipped while the previous one is still running (guarded by a done channel)
+// so syncs never overlap and contend for the shared DB and rate-limited
+// MusicBrainz client.
 func (a *App) startPeriodicSync(ctx context.Context) {
 	ticker := time.NewTicker(a.cfg.Sync.Interval)
 	defer ticker.Stop()
 
+	// free is a sentinel channel: nil means a sync is currently in flight.
+	var free = make(chan struct{}, 1)
+	free <- struct{}{}
+
 	for {
 		select {
 		case <-ctx.Done():
 			log.Println("Periodic sync stopped.")
 			return
 		case <-ticker.C:
+			select {
+			case <-free:
+				// Slot was free; start a sync and release the slot when done.
 				go func() {
+					defer func() { free <- struct{}{} }()
 					if err := a.doSync(ctx); err != nil {
 						if ctx.Err() != nil {
 							return
@@ -195,6 +253,10 @@ func (a *App) startPeriodicSync(ctx context.Context) {
 						log.Printf("Periodic sync+scan failed: %v", err)
 					}
 				}()
+			default:
+				// Previous sync still running; skip this tick.
+				log.Println("Skipping periodic sync: previous sync still in progress.")
+			}
 		}
 	}
 }

config.yaml.example

@@ -4,6 +4,11 @@ server:
   # Basic Auth for Web UI access
   username: "admin"
   password: "CHANGE_ME"
+  # Externally-reachable base URL for links in Telegram digests (e.g. behind a
+  # reverse proxy). If omitted, links are derived from host:port — but when host
+  # is 0.0.0.0 (the unspecified bind address) no link is emitted, since it is
+  # not reachable from outside the host.
+  public_url: "https://naviwatcher.example.com"
 
 navidrome:
   url: "http://localhost:4533"

docs/plans/2026-07-19-notifier-webui-sync.md

@@ -161,3 +161,30 @@ name collisions.)
   ignore/restore actions persist.
 - **External**: ensure `config.yaml.example` matches deployed config; Telegram
   bot token/chat_id must be supplied by operator.
+
+## Follow-up fixes (post code review)
+After the plan's Tasks 1-10 merged, a code review surfaced and fixed:
+- **Duplicate notifications**: `SyncArtistDiscography` previously deleted
+  `notifications_sent` for the whole artist on every cache-miss re-sync, which
+  wiped "already notified" tracking and re-sent digests. Now only notifications
+  for releases that disappear are pruned, and surviving releases keep their sent
+  markers. Re-sync is FK-safe (uses `INSERT OR REPLACE` + `rgid NOT IN (…)`).
+- **Empty-discography caching**: artists with zero MusicBrainz release groups
+  were never cached (a `0`-row result was treated as a cache miss), re-fetching
+  every cycle. Added `artist_settings.last_synced` (migration `009`) as the cache
+  freshness signal so empty discographies honor the TTL.
+- **`main.run` wiring**: the Web UI server and Telegram notifier scheduler are
+  now constructed in `NewApp` and started as goroutines in `run()` (previously
+  only the sync loop ran).
+- **Overlap guard**: `startPeriodicSync` now skips a tick while a previous sync
+  is still in flight (buffered `done` channel) so syncs never overlap.
+- **`server.public_url` config**: added so Telegram digest links use an
+  externally-reachable origin instead of the bind `host:port` (which defaults to
+  `0.0.0.0`). `NewServerWithConfig` falls back to host:port only for a real host.
+- **Web handlers**: artist detail page now uses `scanner.ScanArtist` (per-artist)
+  instead of a full `ScanAll`; removed the always-false `releaseIgnored` lookup
+  and dead `endsWith` helper; the configured fuzzy threshold is now threaded
+  through `Server`.
+- **DB connection pooling**: `:memory:` databases now use `SetMaxOpenConns(1)`
+  so migrations and queries share one in-memory store (prevents "missing column"
+  errors under the connection pool).

internal/config/config.go

@@ -24,6 +24,7 @@ type ServerConfig struct {
 	Port      int    `yaml:"port"`
 	Username  string `yaml:"username"`
 	Password  string `yaml:"password"`
+	PublicURL string `yaml:"public_url"`
 }
 
 // NavidromeConfig holds Subsonic API connection details.

internal/database/artist_settings.go

@@ -4,19 +4,27 @@ import (
 	"database/sql"
 	"errors"
 	"fmt"
+	"time"
 )
 
+// DBer is the minimal query interface satisfied by both *sql.DB and *sql.Tx,
+// so callers can run statements inside or outside a transaction.
+type DBer interface {
+	Exec(query string, args ...interface{}) (sql.Result, error)
+}
+
 // GetArtistSettings retrieves an artist_settings row by ID.
 // Returns sql.ErrNoRows if the artist is not found.
 func GetArtistSettings(db *DB, id string) (*ArtistSettings, error) {
 	var (
 		s         ArtistSettings
 		mbid      sql.NullString
+		lastSynced sql.NullTime
 	)
 	err := db.Conn().QueryRow(
-		"SELECT id, name, mbid, ignore_singles, ignore_compilations, monitored FROM artist_settings WHERE id = ?",
+		"SELECT id, name, mbid, ignore_singles, ignore_compilations, monitored, last_synced FROM artist_settings WHERE id = ?",
 		id,
-	).Scan(&s.ID, &s.Name, &mbid, &s.IgnoreSingles, &s.IgnoreCompilations, &s.Monitored)
+	).Scan(&s.ID, &s.Name, &mbid, &s.IgnoreSingles, &s.IgnoreCompilations, &s.Monitored, &lastSynced)
 	if err != nil {
 		if errors.Is(err, sql.ErrNoRows) {
 			return nil, ErrArtistNotFound
@@ -24,9 +32,26 @@ func GetArtistSettings(db *DB, id string) (*ArtistSettings, error) {
 		return nil, err
 	}
 	s.MBID = mbid.String
+	if lastSynced.Valid {
+		s.LastSynced = lastSynced.Time
+	}
 	return &s, nil
 }
 
+// TouchArtistSynced records that the artist was synced at the given time. It
+// is used by the MusicBrainz pipeline to mark a successful sync (even one that
+// found zero release groups) so the cache TTL is honoured.
+func TouchArtistSynced(db DBer, artistID string, syncedAt time.Time) error {
+	_, err := db.Exec(
+		"UPDATE artist_settings SET last_synced = ? WHERE id = ?",
+		FormatCachedAt(syncedAt), artistID,
+	)
+	if err != nil {
+		return fmt.Errorf("touch artist synced: %w", err)
+	}
+	return nil
+}
+
 // SaveArtistSettings inserts or replaces an artist_settings row.
 func SaveArtistSettings(db *DB, settings *ArtistSettings) error {
 	_, err := db.Conn().Exec(

internal/database/database.go

@@ -25,10 +25,21 @@ func New(dbPath string) (*DB, error) {
 	// EVERY connection in the pool. A one-off "PRAGMA foreign_keys=ON" executed
 	// on the pooled *sql.DB only applies to the first connection and is lost on
 	// connections opened later by the pool, silently disabling the safety net.
+	// A plain ":memory:" database is private to the connection that opened it,
+	// so a pool of N connections would give N separate empty databases and
+	// migrations would appear missing on some. Limiting the pool to a single
+	// connection keeps one in-memory database per New() call, which is correct
+	// for both tests (isolated) and the single-process production service.
 	conn, err := sql.Open("sqlite3", dbPath+"?_foreign_keys=on")
 	if err != nil {
 		return nil, fmt.Errorf("open database: %w", err)
 	}
+	if dbPath == ":memory:" {
+		conn.SetMaxOpenConns(1)
+	}
+	if err != nil {
+		return nil, fmt.Errorf("open database: %w", err)
+	}
 
 	// Enable WAL mode for better concurrent read performance.
 	if _, err := conn.Exec("PRAGMA journal_mode=WAL"); err != nil {
@@ -135,6 +146,10 @@ func (db *DB) migrate() error {
 			name: "008_add_mbid_to_artist_settings",
 			sql:  `ALTER TABLE artist_settings ADD COLUMN mbid TEXT;`,
 		},
+		{
+			name: "009_add_last_synced_to_artist_settings",
+			sql:  `ALTER TABLE artist_settings ADD COLUMN last_synced DATETIME;`,
+		},
 	}
 
 	for _, m := range migrations {
@@ -187,6 +202,7 @@ type ArtistSettings struct {
 	IgnoreSingles      bool      `json:"ignore_singles"`
 	IgnoreCompilations bool      `json:"ignore_compilations"`
 	Monitored          bool      `json:"monitored"`
+	LastSynced         time.Time `json:"last_synced"`
 }
 
 // LocalAlbum represents a row in the local_albums table.

internal/database/database_test.go

@@ -205,11 +205,11 @@ func TestMigrationTracking(t *testing.T) {
 		t.Fatalf("query migrations count: %v", err)
 	}
 
-	// We have 8 recorded migrations: artist_settings, external_releases,
+	// We have 9 recorded migrations: artist_settings, external_releases,
 	// local_albums, notifications_sent, cached_at column, secondary_types
-	// column, the external_releases.artist_id index, and the artist_settings
-	// mbid column.
-	if count != 8 {
-		t.Errorf("expected 8 applied migrations, got %d", count)
+	// column, the external_releases.artist_id index, the artist_settings mbid
+	// column, and the artist_settings last_synced column.
+	if count != 9 {
+		t.Errorf("expected 9 applied migrations, got %d", count)
 	}
 }

internal/database/external_releases.go

@@ -166,6 +166,42 @@ func SetReleaseIgnored(db *DB, rgid string, ignored bool) error {
 	return nil
 }
 
+// ArtistCacheFresh reports whether the artist was synced within the TTL. A hit
+// requires a fresh external_releases row (covers pre-seeded/non-empty caches)
+// OR a fresh artist_settings.last_synced (covers empty discographies, which
+// store no external_releases rows but are still marked as synced). Either
+// signal means we should not re-fetch from MusicBrainz.
+func ArtistCacheFresh(db *DB, artistID string, ttl time.Duration) (bool, error) {
+	if ttl <= 0 {
+		return false, nil
+	}
+	cutoff := time.Now().UTC().Add(-ttl).Format(utcLayout)
+	var dummy int
+	err := db.Conn().QueryRow(
+		"SELECT 1 FROM external_releases WHERE artist_id = ? AND cached_at >= ? LIMIT 1",
+		artistID, cutoff,
+	).Scan(&dummy)
+	if err == nil {
+		return true, nil
+	}
+	if err != sql.ErrNoRows {
+		return false, fmt.Errorf("check artist cache freshness (releases): %w", err)
+	}
+
+	// Fall back to the per-artist last_synced marker (set even on empty syncs).
+	err = db.Conn().QueryRow(
+		"SELECT 1 FROM artist_settings WHERE id = ? AND last_synced >= ? LIMIT 1",
+		artistID, cutoff,
+	).Scan(&dummy)
+	if err == nil {
+		return true, nil
+	}
+	if err == sql.ErrNoRows {
+		return false, nil
+	}
+	return false, fmt.Errorf("check artist cache freshness (settings): %w", err)
+}
+
 // GetExternalReleasesByArtistWithCache returns cached external_release rows for a given artist_id
 // that are within the specified TTL.
 func GetExternalReleasesByArtistWithCache(db *DB, artistID string, ttl time.Duration) ([]ExternalRelease, error) {

internal/musicbrainz/sync.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"database/sql"
 	"fmt"
+	"strings"
 	"time"
 
 	"naviwatcher/internal/database"
@@ -38,18 +39,25 @@ func SyncArtistDiscography(
 		return nil, fmt.Errorf("sync artist discography: %w", err)
 	}
 
-	// Step 1: Check cache.
+	// Step 1: Check cache freshness. A genuine hit means the artist was synced
+	// within the TTL — even when it has zero release groups. We must not gate on
+	// row count, or artists with an empty MusicBrainz discography would be
+	// re-fetched on every sync (defeating the TTL and wasting the 1 req/s budget).
 	cachedReleases, err := database.GetExternalReleasesByArtistWithCache(db, artistID, ttl)
 	if err != nil {
 		return nil, fmt.Errorf("sync artist discography: cache check failed: %w", err)
 	}
+	fresh, err := database.ArtistCacheFresh(db, artistID, ttl)
+	if err != nil {
+		return nil, fmt.Errorf("sync artist discography: cache freshness check failed: %w", err)
+	}
 
-	// Step 2: If we have cached data, return it. Re-apply the per-artist type
-	// toggles even on a cache hit so user changes to ignore_singles /
-	// ignore_compilations take effect without waiting for cache expiry.
-	// (Status/type inclusion was already applied when the rows were first
+	// Step 2: If we have a fresh cache, return the cached data. Re-apply the
+	// per-artist type toggles even on a cache hit so user changes to
+	// ignore_singles / ignore_compilations take effect without waiting for cache
+	// expiry. (Status/type inclusion was already applied when the rows were first
 	// synced and stored, so only the toggles can change.)
-	if len(cachedReleases) > 0 {
+	if fresh {
 		if err := ctx.Err(); err != nil {
 			return nil, fmt.Errorf("sync artist discography: %w", err)
 		}
@@ -108,18 +116,45 @@ func SyncArtistDiscography(
 	}
 	rows.Close()
 
-	// Delete old entries for this artist to avoid stale records.
-	// Must delete notifications_sent first to avoid FK violation since
-	// notifications_sent.rgid references external_releases.rgid.
-	if _, err := tx.Exec(
-		"DELETE FROM notifications_sent WHERE rgid IN (SELECT rgid FROM external_releases WHERE artist_id = ?)",
-		artistID,
-	); err != nil {
-		return nil, fmt.Errorf("sync artist discography: delete old notifications: %w", err)
+	// Build the set of RGIDs present in this sync so we can drop only the rows
+	// that disappeared, leaving the rest (and their notification markers) intact.
+	synced := make([]any, 0, len(filtered))
+	for _, rg := range filtered {
+		synced = append(synced, rg.ID)
+	}
+
+	// Drop notification markers for releases that are gone. This runs before the
+	// external_releases delete so the FK on notifications_sent.rgid stays valid
+	// (we only ever delete from notifications_sent here).
+	if len(synced) > 0 {
+		placeholders := strings.Repeat("?,", len(synced))
+		placeholders = placeholders[:len(placeholders)-1]
+		query := fmt.Sprintf(
+			"DELETE FROM notifications_sent WHERE rgid IN (SELECT rgid FROM external_releases WHERE artist_id = ? AND rgid NOT IN (%s))",
+			placeholders,
+		)
+		args := append([]any{artistID}, synced...)
+		if _, err := tx.Exec(query, args...); err != nil {
+			return nil, fmt.Errorf("sync artist discography: prune stale notifications: %w", err)
+		}
+		// Remove external_release rows that are no longer part of the discography.
+		delQuery := fmt.Sprintf(
+			"DELETE FROM external_releases WHERE artist_id = ? AND rgid NOT IN (%s)",
+			placeholders,
+		)
+		if _, err := tx.Exec(delQuery, args...); err != nil {
+			return nil, fmt.Errorf("sync artist discography: delete stale releases: %w", err)
+		}
+	} else {
+		// No releases this sync: the artist may have an empty discography. Drop
+		// everything we previously cached for them.
+		if _, err := tx.Exec("DELETE FROM notifications_sent WHERE rgid IN (SELECT rgid FROM external_releases WHERE artist_id = ?)", artistID); err != nil {
+			return nil, fmt.Errorf("sync artist discography: delete notifications: %w", err)
 		}
 		if _, err := tx.Exec("DELETE FROM external_releases WHERE artist_id = ?", artistID); err != nil {
 			return nil, fmt.Errorf("sync artist discography: delete old releases: %w", err)
 		}
+	}
 
 	var releases []database.ExternalRelease
 	for _, rg := range filtered {
@@ -136,7 +171,7 @@ func SyncArtistDiscography(
 		}
 
 		if _, err := tx.Exec(
-			"INSERT INTO external_releases (rgid, artist_id, title, type, release_date, is_ignored, cached_at, secondary_types) VALUES (?, ?, ?, ?, ?, ?, ?, ?)",
+			"INSERT OR REPLACE INTO external_releases (rgid, artist_id, title, type, release_date, is_ignored, cached_at, secondary_types) VALUES (?, ?, ?, ?, ?, ?, ?, ?)",
 			ext.RGID, ext.ArtistID, ext.Title, ext.Type, ext.ReleaseDate, ext.IsIgnored, database.FormatCachedAt(ext.CachedAt), database.JoinSecondaryTypes(ext.SecondaryTypes),
 		); err != nil {
 			return nil, fmt.Errorf("sync artist discography: insert release %s: %w", rg.ID, err)
@@ -145,6 +180,13 @@ func SyncArtistDiscography(
 		releases = append(releases, *ext)
 	}
 
+	// Mark the artist as synced (even when it has zero release groups) so the
+	// cache TTL honours empty discographies and they are not re-fetched every
+	// cycle.
+	if err := database.TouchArtistSynced(tx, artistID, now); err != nil {
+		return nil, fmt.Errorf("sync artist discography: touch last_synced: %w", err)
+	}
+
 	if err := tx.Commit(); err != nil {
 		return nil, fmt.Errorf("sync artist discography: commit transaction: %w", err)
 	}

internal/musicbrainz/sync_test.go

@@ -370,11 +370,16 @@ func TestSyncArtistDiscography_IdempotentResync(t *testing.T) {
 		t.Fatalf("expected 1 server call after first sync, got %d", callCount)
 	}
 
-	// Force cache expiry by setting cached_at to the past.
+	// Force cache expiry by setting cached_at (on external_releases) and
+	// last_synced (on artist_settings) to the past.
 	_, err = db.Conn().Exec("UPDATE external_releases SET cached_at = ? WHERE artist_id = ?",
 		time.Now().Add(-48*time.Hour).Format("2006-01-02 15:04:05"), artistID)
 	if err != nil {
-		t.Fatalf("expire cache: %v", err)
+		t.Fatalf("expire cache (releases): %v", err)
+	}
+	if _, err = db.Conn().Exec("UPDATE artist_settings SET last_synced = ? WHERE id = ?",
+		time.Now().Add(-48*time.Hour).Format("2006-01-02 15:04:05"), artistID); err != nil {
+		t.Fatalf("expire cache (settings): %v", err)
 	}
 
 	// Second sync should re-fetch from API (cache expired).
@@ -438,6 +443,28 @@ func TestSyncArtistDiscography_EmptyResponse(t *testing.T) {
 	if len(stored) != 0 {
 		t.Errorf("expected 0 stored releases, got %d", len(stored))
 	}
+
+	// A second sync within the TTL must be a cache hit: an empty discography is
+	// now cached via artist_settings.last_synced, so the MusicBrainz API must
+	// not be re-queried (and still returns 0 releases).
+	serverHits := 0
+	server2 := newTestMBServer(func(w http.ResponseWriter, r *http.Request) {
+		serverHits++
+		w.Header().Set("Content-Type", "application/xml")
+		w.Write([]byte(mbReleaseGroupListResponse("", 0)))
+	})
+	defer server2.Close()
+
+	releases2, err := SyncArtistDiscography(ctx, newTestClient(server2.URL), db, artistID, artistMBID, ttl)
+	if err != nil {
+		t.Fatalf("second SyncArtistDiscography() error: %v", err)
+	}
+	if len(releases2) != 0 {
+		t.Errorf("expected 0 releases on cached empty sync, got %d", len(releases2))
+	}
+	if serverHits != 0 {
+		t.Errorf("expected empty discography to be cached (0 API calls), got %d", serverHits)
+	}
 }
 
 // -----------------------------------------------------------------------
@@ -714,11 +741,16 @@ func TestSyncArtistDiscography_CleansStaleReleases(t *testing.T) {
 		t.Fatalf("expected 3 releases after first sync, got %d", len(releases1))
 	}
 
-	// Force cache expiry by setting cached_at to the past.
+	// Force cache expiry by setting cached_at (on external_releases) and
+	// last_synced (on artist_settings) to the past.
 	_, err = db.Conn().Exec("UPDATE external_releases SET cached_at = ? WHERE artist_id = ?",
 		time.Now().Add(-48*time.Hour).Format("2006-01-02 15:04:05"), artistID)
 	if err != nil {
-		t.Fatalf("expire cache: %v", err)
+		t.Fatalf("expire cache (releases): %v", err)
+	}
+	if _, err = db.Conn().Exec("UPDATE artist_settings SET last_synced = ? WHERE id = ?",
+		time.Now().Add(-48*time.Hour).Format("2006-01-02 15:04:05"), artistID); err != nil {
+		t.Fatalf("expire cache (settings): %v", err)
 	}
 
 	// Second sync should re-fetch from API (cache expired).
@@ -876,10 +908,14 @@ func TestSyncArtistDiscography_ResyncWithNotifications(t *testing.T) {
 	artistID := "nav-fk-test"
 	artistName := "FK Artist"
 
+	// First response includes two release groups; the second sync drops one
+	// ("rg-2") so we can verify its notification is pruned while the surviving
+	// release's notification ("rg-1") is preserved.
 	server := newTestMBServer(func(w http.ResponseWriter, r *http.Request) {
 		resp := mbReleaseGroupListResponse(
-			mbReleaseGroupXML("rg-1", "Album", "Album", "Official", artistMBID, artistName, "2024-01-01"),
-			1,
+			mbReleaseGroupXML("rg-1", "Album", "Album", "Official", artistMBID, artistName, "2024-01-01")+
+				mbReleaseGroupXML("rg-2", "Album", "Album", "Official", artistMBID, artistName, "2023-01-01"),
+			2,
 		)
 		w.Write([]byte(resp))
 	})
@@ -893,27 +929,37 @@ func TestSyncArtistDiscography_ResyncWithNotifications(t *testing.T) {
 	ctx := context.Background()
 
 	// First sync.
-	_, err := SyncArtistDiscography(ctx, client, db, artistID, artistMBID, 24*time.Hour)
-	if err != nil {
+	if _, err := SyncArtistDiscography(ctx, client, db, artistID, artistMBID, 24*time.Hour); err != nil {
 		t.Fatalf("first SyncArtistDiscography() error: %v", err)
 	}
 
-	// Insert a notifications_sent row referencing the release.
-	_, err = db.Conn().Exec(
-		"INSERT INTO notifications_sent (rgid) VALUES (?)", "rg-1",
-	)
-	if err != nil {
+	// Mark both releases as already notified.
+	for _, rgid := range []string{"rg-1", "rg-2"} {
+		if _, err := db.Conn().Exec("INSERT INTO notifications_sent (rgid) VALUES (?)", rgid); err != nil {
 			t.Fatalf("insert notification: %v", err)
 		}
-
-	// Force cache expiry.
-	_, err = db.Conn().Exec("UPDATE external_releases SET cached_at = ? WHERE artist_id = ?",
-		time.Now().Add(-48*time.Hour).Format("2006-01-02 15:04:05"), artistID)
-	if err != nil {
-		t.Fatalf("expire cache: %v", err)
 	}
 
-	// Second sync should succeed without FK violation.
+	// Force cache expiry on the first sync so the second sync re-fetches.
+	if _, err := db.Conn().Exec("UPDATE external_releases SET cached_at = ? WHERE artist_id = ?",
+		time.Now().Add(-48*time.Hour).Format("2006-01-02 15:04:05"), artistID); err != nil {
+		t.Fatalf("expire cache (releases): %v", err)
+	}
+	if _, err := db.Conn().Exec("UPDATE artist_settings SET last_synced = ? WHERE id = ?",
+		time.Now().Add(-48*time.Hour).Format("2006-01-02 15:04:05"), artistID); err != nil {
+		t.Fatalf("expire cache (settings): %v", err)
+	}
+
+	// Second sync returns only rg-1 (drop rg-2 from the server response) and
+	// must succeed without an FK violation.
+	server.Config.Handler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		resp := mbReleaseGroupListResponse(
+			mbReleaseGroupXML("rg-1", "Album", "Album", "Official", artistMBID, artistName, "2024-01-01"),
+			1,
+		)
+		w.Write([]byte(resp))
+	})
+
 	releases, err := SyncArtistDiscography(ctx, client, db, artistID, artistMBID, 24*time.Hour)
 	if err != nil {
 		t.Fatalf("second SyncArtistDiscography() error (FK violation?): %v", err)
@@ -922,13 +968,20 @@ func TestSyncArtistDiscography_ResyncWithNotifications(t *testing.T) {
 		t.Fatalf("expected 1 release after resync, got %d", len(releases))
 	}
 
-	// Notification should have been cleaned up.
-	var count int
-	err = db.Conn().QueryRow("SELECT COUNT(*) FROM notifications_sent WHERE rgid = ?", "rg-1").Scan(&count)
-	if err != nil {
-		t.Fatalf("count notifications: %v", err)
+	// The surviving release's notification must be preserved (no duplicate
+	// digest on the next notify run). The dropped release's notification must
+	// be pruned.
+	var count1, count2 int
+	if err := db.Conn().QueryRow("SELECT COUNT(*) FROM notifications_sent WHERE rgid = ?", "rg-1").Scan(&count1); err != nil {
+		t.Fatalf("count rg-1 notifications: %v", err)
 	}
-	if count != 0 {
-		t.Errorf("expected 0 notifications after resync, got %d", count)
+	if err := db.Conn().QueryRow("SELECT COUNT(*) FROM notifications_sent WHERE rgid = ?", "rg-2").Scan(&count2); err != nil {
+		t.Fatalf("count rg-2 notifications: %v", err)
+	}
+	if count1 != 1 {
+		t.Errorf("expected surviving release rg-1 notification preserved (1), got %d", count1)
+	}
+	if count2 != 0 {
+		t.Errorf("expected dropped release rg-2 notification pruned (0), got %d", count2)
 	}
 }

internal/web/handlers.go

@@ -32,7 +32,7 @@ func (s *Server) handleDashboard(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	threshold := s.defaultThreshold()
+	threshold := s.threshold
 	data, err := s.buildDashboardData(r.Context(), threshold)
 	if err != nil {
 		http.Error(w, fmt.Sprintf("failed to build dashboard: %v", err), http.StatusInternalServerError)
@@ -120,11 +120,14 @@ func (s *Server) buildArtistData(ctx context.Context, id string) (*ArtistData, e
 		return nil, fmt.Errorf("load local albums: %w", err)
 	}
 
-	// Compute the missing releases for this artist.
-	threshold := s.defaultThreshold()
-	missing, err := scanner.ScanAll(ctx, s.db, threshold)
+	// Compute the missing releases for this single artist (ScanArtist scopes the
+	// query to the artist instead of scanning every monitored artist). ScanAll
+	// excludes ignored releases, so every missing release surfaced here is, by
+	// definition, not ignored.
+	threshold := s.threshold
+	missing, err := scanner.ScanArtist(ctx, s.db, id, threshold)
 	if err != nil {
-		return nil, fmt.Errorf("scan: %w", err)
+		return nil, fmt.Errorf("scan artist: %w", err)
 	}
 
 	data := &ArtistData{
@@ -138,38 +141,18 @@ func (s *Server) buildArtistData(ctx context.Context, id string) (*ArtistData, e
 		data.LocalAlbums = append(data.LocalAlbums, LocalAlbumView{Title: a.Title})
 	}
 	for _, m := range missing {
-		if m.ArtistID != id {
-			continue
-		}
-		ignored, igErr := s.releaseIgnored(id, m.RGID)
-		if igErr != nil {
-			return nil, igErr
-		}
 		data.Missing = append(data.Missing, MissingReleaseView{
-			ArtistID:    id,
+			ArtistID:    m.ArtistID,
 			RGID:        m.RGID,
 			Title:       m.Title,
 			Type:        m.Type,
 			ReleaseDate: m.ReleaseDate,
-			Ignored:     ignored,
+			Ignored:     false,
 		})
 	}
 	return data, nil
 }
 
-// releaseIgnored reports whether the external release with the given RGID is
-// flagged ignored.
-func (s *Server) releaseIgnored(artistID, rgid string) (bool, error) {
-	// ScanAll already excludes ignored releases, so a missing release shown here
-	// is, by definition, not ignored. We still surface the persisted flag so the
-	// UI can reflect a release that was ignored and later re-evaluated.
-	rel, err := database.GetExternalRelease(s.db, rgid)
-	if err != nil {
-		return false, fmt.Errorf("get external release %s: %w", rgid, err)
-	}
-	return rel.IsIgnored, nil
-}
-
 // ArchiveData is the view model for the ignored-releases archive page.
 type ArchiveData struct {
 	Releases []MissingReleaseView
@@ -208,20 +191,20 @@ func (s *Server) handleArchive(w http.ResponseWriter, r *http.Request) {
 	}
 }
 
-// defaultThreshold returns the fuzzy threshold to use when scanning for the
-// dashboard. It is currently fixed at the engine default; later wiring can
-// thread the configured threshold through the Server if desired.
-func (s *Server) defaultThreshold() float64 {
-	return 0 // 0 → scanner.DefaultThreshold
-}
-
 // NewServerWithConfig is a convenience constructor that accepts the full
 // *config.Config (mirroring how the app constructs other components). It
-// forwards the server sub-config and derives uiBaseURL from host/port.
+// forwards the server sub-config and derives uiBaseURL from the configured
+// public_url, falling back to a best-effort host:port.
 func NewServerWithConfig(cfg *config.Config, db *database.DB) *Server {
-	// Build a best-effort external base URL from the server config.
-	base := fmt.Sprintf("http://%s:%d", cfg.Server.Host, cfg.Server.Port)
-	return NewServer(&cfg.Server, db, base)
+	// Prefer an explicit, externally-reachable public_url (e.g. behind a
+	// reverse proxy). Fall back to host:port — but if the bind host is the
+	// unspecified "0.0.0.0", it is not reachable from outside the host, so
+	// omit the link rather than advertise an unusable address.
+	base := cfg.Server.PublicURL
+	if base == "" && cfg.Server.Host != "0.0.0.0" && cfg.Server.Host != "" {
+		base = fmt.Sprintf("http://%s:%d", cfg.Server.Host, cfg.Server.Port)
+	}
+	return NewServer(&cfg.Server, db, base, cfg.Scanner.FuzzyThreshold)
 }
 
 // ignoreOrRestore handles the POST /artist/{id}/ignore and .../restore routes.
@@ -290,8 +273,3 @@ func (s *Server) toggleIgnoreSingles(w http.ResponseWriter, r *http.Request) {
 	http.Redirect(w, r, "/artist/"+id, http.StatusSeeOther)
 }
 
-// endsWith reports whether s ends with suffix.
-func endsWith(s, suffix string) bool {
-	return len(s) >= len(suffix) && s[len(s)-len(suffix):] == suffix
-}
-

internal/web/server.go

@@ -27,16 +27,22 @@ type Server struct {
 	// uiBaseURL is the externally reachable base URL of the dashboard (scheme +
 	// host), used to build links in notifications and elsewhere. Optional.
 	uiBaseURL string
+
+	// threshold is the fuzzy-similarity cutoff used when scanning for missing
+	// releases; 0 means use the scanner default.
+	threshold float64
 }
 
 // NewServer constructs a dashboard Server bound to the given DB and server
 // config. uiBaseURL is the externally reachable origin (e.g.
 // "http://localhost:8080") used when rendering absolute links; pass "" to omit.
-func NewServer(cfg *config.ServerConfig, db *database.DB, uiBaseURL string) *Server {
+// threshold is the fuzzy-similarity cutoff (0 → scanner default).
+func NewServer(cfg *config.ServerConfig, db *database.DB, uiBaseURL string, threshold float64) *Server {
 	s := &Server{
 		cfg:       cfg,
 		db:        db,
 		uiBaseURL: strings.TrimRight(uiBaseURL, "/"),
+		threshold: threshold,
 	}
 	mux := http.NewServeMux()
 	mux.HandleFunc("/", s.handleDashboard)

internal/web/server_test.go

@@ -51,7 +51,7 @@ func newServer(t *testing.T, user, pass string) (*Server, *database.DB) {
 		t.Fatalf("open db: %v", err)
 	}
 	cfg := &config.ServerConfig{Host: "0.0.0.0", Port: 8080, Username: user, Password: pass}
-	s := NewServer(cfg, db, "http://ui.example")
+	s := NewServer(cfg, db, "http://ui.example", 0)
 	return s, db
 }