fix(artwork): clear a fresh-looking hash when the serve finds no source

In the window before a rescan records a deleted cover (or after cache
eviction/restart), no row or mtime signal moves, so the freshness skip kept
the stale hash. ErrUnavailable serves now carry a sourceGone signal that
bypasses the skip only while a stored hash remains to clear — afterwards
the negative cache applies, so artwork-less entities still don't re-resolve
per serve. The e2e spec now covers the no-rescan window.

core/artwork/artwork.go

@@ -83,7 +83,7 @@ func (a *artwork) Get(ctx context.Context, artID model.ArtworkID, size int, squa
 		// A vanished source must still reach the worker, or a stored hash would keep describing
 		// artwork that no longer exists.
 		if a.blurHashes != nil && errors.Is(err, ErrUnavailable) {
-			a.blurHashes.Enqueue(artID, artReader.LastUpdated(), false)
+			a.blurHashes.Enqueue(artID, artReader.LastUpdated(), false, true)
 		}
 		return nil, time.Time{}, err
 	}
@@ -93,7 +93,7 @@ func (a *artwork) Get(ctx context.Context, artID model.ArtworkID, size int, squa
 		// readers re-fetch the original through Get, carrying the real signal); nor does cache
 		// warmup/disabled, where every serve misses — there the LastUpdated signal applies.
 		force := size == 0 && !square && !r.Cached && a.cache.Available(ctx)
-		a.blurHashes.Enqueue(artID, artReader.LastUpdated(), force)
+		a.blurHashes.Enqueue(artID, artReader.LastUpdated(), force, false)
 	}
 	return r, artReader.LastUpdated(), nil
 }

core/artwork/blurhash_updater.go

@@ -17,10 +17,12 @@ import (
 	"github.com/navidrome/navidrome/resources"
 )
 
-// enqueueRequest carries the staleness signals seen at serve time: force (image-cache miss) and
-// the reader's LastUpdated, which tracks file mtimes that no entity row timestamp reflects.
+// enqueueRequest carries the staleness signals seen at serve time: force (image-cache miss),
+// sourceGone (the serve failed with ErrUnavailable) and the reader's LastUpdated, which tracks
+// file mtimes that no entity row timestamp reflects.
 type enqueueRequest struct {
 	force          bool
+	sourceGone     bool
 	imageUpdatedAt time.Time
 }
 
@@ -59,7 +61,7 @@ func newBlurHashUpdater(a *artwork) *blurHashUpdater {
 	}
 }
 
-func (u *blurHashUpdater) Enqueue(artID model.ArtworkID, imageUpdatedAt time.Time, force bool) {
+func (u *blurHashUpdater) Enqueue(artID model.ArtworkID, imageUpdatedAt time.Time, force, sourceGone bool) {
 	switch artID.Kind {
 	case model.KindAlbumArtwork, model.KindArtistArtwork, model.KindPlaylistArtwork:
 	default:
@@ -80,6 +82,7 @@ func (u *blurHashUpdater) Enqueue(artID model.ArtworkID, imageUpdatedAt time.Tim
 	}
 	req := u.buffer[artID]
 	req.force = req.force || force
+	req.sourceGone = req.sourceGone || sourceGone
 	if imageUpdatedAt.After(req.imageUpdatedAt) {
 		req.imageUpdatedAt = imageUpdatedAt
 	}
@@ -167,7 +170,10 @@ func (u *blurHashUpdater) process(ctx context.Context, artID model.ArtworkID, re
 	if req.imageUpdatedAt.After(sig) {
 		sig = req.imageUpdatedAt
 	}
-	if !req.force {
+	// A gone source only forces while a hash remains to clear; afterwards the negative cache
+	// applies, so artwork-less entities don't re-resolve on every placeholder serve.
+	force := req.force || (req.sourceGone && stored != "")
+	if !force {
 		// Current when computed from this row version or later; the snapshot may exceed the row
 		// version because file mtimes (which don't move rows) are folded into it on persist.
 		if stored != "" && storedAt != nil && !storedAt.Before(version) && !sig.After(*storedAt) {

core/artwork/blurhash_updater_internal_test.go

@@ -38,17 +38,18 @@ var _ = Describe("blurHashUpdater", func() {
 			id := model.Album{ID: "al-1"}.CoverArtID()
 			t1 := time.Date(2024, 1, 1, 0, 0, 0, 0, time.UTC)
 			t2 := t1.Add(time.Hour)
-			u.Enqueue(id, t2, true)
-			u.Enqueue(id, t1, false)
-			u.Enqueue(model.Artist{ID: "ar-1"}.CoverArtID(), t1, false)
+			u.Enqueue(id, t2, true, false)
+			u.Enqueue(id, t1, false, true)
+			u.Enqueue(model.Artist{ID: "ar-1"}.CoverArtID(), t1, false, false)
 			Expect(u.buffer).To(HaveLen(2))
 			Expect(u.buffer[id].force).To(BeTrue())
+			Expect(u.buffer[id].sourceGone).To(BeTrue())
 			Expect(u.buffer[id].imageUpdatedAt).To(Equal(t2))
 		})
 
 		It("ignores other artwork kinds", func() {
-			u.Enqueue(model.ArtworkID{Kind: model.KindMediaFileArtwork, ID: "mf-1"}, time.Time{}, false)
-			u.Enqueue(model.ArtworkID{Kind: model.KindRadioArtwork, ID: "ra-1"}, time.Time{}, true)
+			u.Enqueue(model.ArtworkID{Kind: model.KindMediaFileArtwork, ID: "mf-1"}, time.Time{}, false, false)
+			u.Enqueue(model.ArtworkID{Kind: model.KindRadioArtwork, ID: "ra-1"}, time.Time{}, true, false)
 			Expect(u.buffer).To(BeEmpty())
 		})
 	})
@@ -116,6 +117,21 @@ var _ = Describe("blurHashUpdater", func() {
 			Expect(stored.BlurHash).To(BeEmpty())
 		})
 
+		It("clears a fresh-looking stored hash when the source is gone", func() {
+			al := model.Album{ID: "al-1", UpdatedAt: version, BlurHash: "LEHV6nWB2yk8", BlurHashUpdatedAt: &version}
+			repo := tests.CreateMockAlbumRepo()
+			repo.SetData(model.Albums{al})
+			ds.MockedAlbum = repo
+			ds.MockedFolder = failingFolderRepo{}
+
+			// No row/mtime signal moved (eviction/restart window), but the serve 404ed: sourceGone
+			// must bypass the freshness skip so the stale hash is cleared.
+			u.process(GinkgoT().Context(), al.CoverArtID(), enqueueRequest{imageUpdatedAt: version, sourceGone: true})
+			stored, err := ds.Album(GinkgoT().Context()).Get("al-1")
+			Expect(err).ToNot(HaveOccurred())
+			Expect(stored.BlurHash).To(BeEmpty())
+		})
+
 		It("does nothing when the entity is gone", func() {
 			ds.MockedAlbum = tests.CreateMockAlbumRepo()
 			Expect(func() {

core/artwork/e2e/blurhash_test.go

@@ -49,10 +49,11 @@ var _ = Describe("BlurHash", func() {
 			g.Expect(updated.BlurHash).ToNot(BeEmpty())
 		}, "10s", "100ms").Should(Succeed())
 
+		// No rescan: the folder row still lists the cover, but the file is gone — the serve's
+		// ErrUnavailable alone must trigger the clear.
 		setLayout(fstest.MapFS{
 			"Artist/Album/01 - Song.mp3": trackFile(1, "Song"),
 		})
-		scan()
 		_, err := readArtworkOrErr(al.CoverArtID())
 		Expect(err).To(HaveOccurred())