diff --git a/internal/db/dbq/library_changes.sql.go b/internal/db/dbq/library_changes.sql.go
index de326379..0eeda6c4 100644
--- a/internal/db/dbq/library_changes.sql.go
+++ b/internal/db/dbq/library_changes.sql.go
@@ -102,3 +102,26 @@ func (q *Queries) InsertLibraryChange(ctx context.Context, arg InsertLibraryChan
 	_, err := q.db.Exec(ctx, insertLibraryChange, arg.EntityType, arg.EntityID, arg.Op)
 	return err
 }
+
+const insertLibraryChanges = `-- name: InsertLibraryChanges :exec
+INSERT INTO library_changes (entity_type, entity_id, op)
+SELECT $1::text,
+       unnest($2::text[]),
+       $3::text
+`
+
+type InsertLibraryChangesParams struct {
+	EntityType string
+	EntityIds  []string
+	Op         string
+}
+
+// Batch form, for a mutation that touches many rows at once (#2704: the scan's
+// reconcile pass can mark up to a quarter of a library missing in one go).
+// Every caller before this one changed a single entity, so per-row inserts
+// were the right shape; a loop here would be thousands of round-trips inside
+// a scan that is already the slow path.
+func (q *Queries) InsertLibraryChanges(ctx context.Context, arg InsertLibraryChangesParams) error {
+	_, err := q.db.Exec(ctx, insertLibraryChanges, arg.EntityType, arg.EntityIds, arg.Op)
+	return err
+}
diff --git a/internal/db/queries/library_changes.sql b/internal/db/queries/library_changes.sql
index 463e48e0..86a17848 100644
--- a/internal/db/queries/library_changes.sql
+++ b/internal/db/queries/library_changes.sql
@@ -2,6 +2,17 @@
 INSERT INTO library_changes (entity_type, entity_id, op)
 VALUES ($1, $2, $3);
 
+-- name: InsertLibraryChanges :exec
+-- Batch form, for a mutation that touches many rows at once (#2704: the scan's
+-- reconcile pass can mark up to a quarter of a library missing in one go).
+-- Every caller before this one changed a single entity, so per-row inserts
+-- were the right shape; a loop here would be thousands of round-trips inside
+-- a scan that is already the slow path.
+INSERT INTO library_changes (entity_type, entity_id, op)
+SELECT sqlc.arg(entity_type)::text,
+       unnest(sqlc.arg(entity_ids)::text[]),
+       sqlc.arg(op)::text;
+
 -- name: GetLibraryChangesSince :many
 SELECT id, entity_type, entity_id, op, changed_at
 FROM library_changes
diff --git a/internal/library/reconcile.go b/internal/library/reconcile.go
index 6c406cf2..534b42e8 100644
--- a/internal/library/reconcile.go
+++ b/internal/library/reconcile.go
@@ -9,6 +9,7 @@ import (
 	"github.com/jackc/pgx/v5/pgtype"
 
 	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
+	syncpkg "git.fabledsword.com/bvandeusen/minstrel/internal/sync"
 )
 
 // trackReconciler is the slice of dbq.Queries reconcileMissing needs. Narrowed
@@ -18,6 +19,7 @@ type trackReconciler interface {
 	ListTrackPathsForReconcile(ctx context.Context) ([]dbq.ListTrackPathsForReconcileRow, error)
 	MarkTracksMissing(ctx context.Context, ids []pgtype.UUID) (int64, error)
 	ClearTracksMissing(ctx context.Context, ids []pgtype.UUID) (int64, error)
+	InsertLibraryChanges(ctx context.Context, arg dbq.InsertLibraryChangesParams) error
 }
 
 // Reconcile marks tracks whose files have disappeared (#2523).
@@ -91,6 +93,9 @@ func (s *Scanner) reconcileMissing(
 	// otherwise a library that tripped the cap once could never recover its
 	// marks even after the mount came back.
 	if len(toClear) > 0 {
+		if err := logTrackChanges(ctx, q, toClear); err != nil {
+			return fmt.Errorf("log restored changes: %w", err)
+		}
 		n, err := q.ClearTracksMissing(ctx, toClear)
 		if err != nil {
 			return fmt.Errorf("clear missing marks: %w", err)
@@ -110,6 +115,9 @@ func (s *Scanner) reconcileMissing(
 		)
 	}
 
+	if err := logTrackChanges(ctx, q, toMark); err != nil {
+		return fmt.Errorf("log missing changes: %w", err)
+	}
 	n, err := q.MarkTracksMissing(ctx, toMark)
 	if err != nil {
 		return fmt.Errorf("mark tracks missing: %w", err)
@@ -123,6 +131,41 @@ func (s *Scanner) reconcileMissing(
 	return nil
 }
 
+// logTrackChanges tells the delta sync that these tracks changed, so clients
+// pick up the missing mark (#2704).
+//
+// Without this the mark was invisible to every client: MarkTracksMissing and
+// ClearTracksMissing are plain UPDATEs, and /api/library/sync is a change-log
+// feed — a row that never produces a change is never re-sent, so a client
+// would keep its stale copy until an unrelated edit touched the track or the
+// cursor fell out of the retention window.
+//
+// Logged BEFORE the mutation, deliberately, which is the opposite of the
+// scanner's log-after-success pattern. The two failure modes are not
+// symmetric: log-then-fail-to-mark makes clients re-fetch a track that has
+// not changed, which costs one wasted read. Mark-then-fail-to-log leaves the
+// mark in place with no change row, and because both statements are
+// idempotent (`missing_since IS NULL` / `IS NOT NULL` guards) the next scan
+// will not retry the pair — so the client never learns, permanently. A
+// spurious re-read is the cheaper mistake.
+func logTrackChanges(ctx context.Context, q trackReconciler, ids []pgtype.UUID) error {
+	if len(ids) == 0 {
+		return nil
+	}
+	strIDs := make([]string, 0, len(ids))
+	for _, id := range ids {
+		strIDs = append(strIDs, syncpkg.FormatUUID(id))
+	}
+	// OpUpsert, not OpDelete: the track still exists and keeps its history —
+	// only its playability changed. A delete would tell clients to drop the
+	// row, which is the behaviour #2704 deliberately rejected.
+	return q.InsertLibraryChanges(ctx, dbq.InsertLibraryChangesParams{
+		EntityType: string(syncpkg.EntityTrack),
+		EntityIds:  strIDs,
+		Op:         string(syncpkg.OpUpsert),
+	})
+}
+
 // verifyRootsPresent is the first and most important guard. If a configured root
 // doesn't resolve to a readable directory, the walk beneath it found nothing and
 // every row under it would look deleted. An unmounted media volume is the
diff --git a/internal/library/reconcile_test.go b/internal/library/reconcile_test.go
index a5248f73..55cb8e45 100644
--- a/internal/library/reconcile_test.go
+++ b/internal/library/reconcile_test.go
@@ -26,6 +26,8 @@ type fakeReconciler struct {
 	listErr  error
 	markErr  error
 	clearErr error
+	// Change rows the reconcile pass asked the delta sync to emit (#2704).
+	loggedChanges []dbq.InsertLibraryChangesParams
 }
 
 func (f *fakeReconciler) ListTrackPathsForReconcile(context.Context) ([]dbq.ListTrackPathsForReconcileRow, error) {
@@ -40,6 +42,13 @@ func (f *fakeReconciler) MarkTracksMissing(_ context.Context, ids []pgtype.UUID)
 	return int64(len(ids)), nil
 }
 
+func (f *fakeReconciler) InsertLibraryChanges(
+	_ context.Context, arg dbq.InsertLibraryChangesParams,
+) error {
+	f.loggedChanges = append(f.loggedChanges, arg)
+	return nil
+}
+
 func (f *fakeReconciler) ClearTracksMissing(_ context.Context, ids []pgtype.UUID) (int64, error) {
 	if f.clearErr != nil {
 		return 0, f.clearErr
@@ -324,3 +333,68 @@ func TestVerifyRootsPresent_NoRootsConfigured(t *testing.T) {
 		t.Fatal("expected an error with no scan roots configured")
 	}
 }
+
+// Without a change row the mark is invisible to every client:
+// /api/library/sync is a change-log feed, so a plain UPDATE never reaches
+// anyone. This was the gap that made #2704's wire field inert — the flag
+// existed and nothing ever told a client to re-read the track.
+func TestReconcileMissing_MarkingEmitsSyncChanges(t *testing.T) {
+	s := testScanner(t, populatedRoot(t))
+
+	// 10 rows, 2 absent — under the cap, so this exercises marking.
+	rows := make([]dbq.ListTrackPathsForReconcileRow, 0, 10)
+	seen := map[string]struct{}{}
+	for i := 0; i < 10; i++ {
+		path := fmt.Sprintf("/music/track-%02d.mp3", i)
+		rows = append(rows, row(byte(i), path, false))
+		if i >= 2 {
+			seen[path] = struct{}{}
+		}
+	}
+	q := &fakeReconciler{rows: rows}
+	var stats Stats
+
+	if err := s.reconcileMissing(context.Background(), q, seen, &stats); err != nil {
+		t.Fatalf("reconcile: %v", err)
+	}
+
+	if len(q.loggedChanges) != 1 {
+		t.Fatalf("want one batch of change rows, got %d", len(q.loggedChanges))
+	}
+	got := q.loggedChanges[0]
+	if got.EntityType != "track" {
+		t.Errorf("entity_type = %q, want track", got.EntityType)
+	}
+	// Upsert, not delete: the track still exists and keeps its history. A
+	// delete would tell clients to drop the row, which is the behaviour
+	// #2704 deliberately rejected.
+	if got.Op != "upsert" {
+		t.Errorf("op = %q, want upsert — the row survives, only its state changed", got.Op)
+	}
+	if len(got.EntityIds) != 2 {
+		t.Errorf("want both missing tracks logged, got %d ids", len(got.EntityIds))
+	}
+}
+
+// A file coming back must reach clients too, or a restored track stays
+// greyed out on every device until something unrelated touches it.
+func TestReconcileMissing_RestoringEmitsSyncChanges(t *testing.T) {
+	s := testScanner(t, populatedRoot(t))
+	q := &fakeReconciler{rows: []dbq.ListTrackPathsForReconcileRow{
+		row(1, "/music/back.mp3", true),
+	}}
+	var stats Stats
+
+	if err := s.reconcileMissing(
+		context.Background(), q, map[string]struct{}{"/music/back.mp3": {}}, &stats,
+	); err != nil {
+		t.Fatalf("reconcile: %v", err)
+	}
+
+	if len(q.loggedChanges) != 1 {
+		t.Fatalf("a restored file must produce a change row, got %d batches", len(q.loggedChanges))
+	}
+	if q.loggedChanges[0].Op != "upsert" {
+		t.Errorf("op = %q, want upsert", q.loggedChanges[0].Op)
+	}
+}
diff --git a/internal/sync/changes.go b/internal/sync/changes.go
index 1734e611..a14b617d 100644
--- a/internal/sync/changes.go
+++ b/internal/sync/changes.go
@@ -36,6 +36,29 @@ func LogChange(ctx context.Context, dbtx dbq.DBTX, entityType EntityType, entity
 	return nil
 }
 
+// LogChanges is LogChange for a set of entities of one type sharing one op.
+//
+// Exists because the scan's reconcile pass can mark a quarter of a library
+// missing in a single sweep (#2704), and a per-row loop there would be
+// thousands of round-trips inside an operation that is already slow. Every
+// other caller mutates one entity and should keep using LogChange.
+//
+// A no-op on an empty set, so callers don't have to guard.
+func LogChanges(ctx context.Context, dbtx dbq.DBTX, entityType EntityType, entityIDs []string, op Op) error {
+	if len(entityIDs) == 0 {
+		return nil
+	}
+	q := dbq.New(dbtx)
+	if err := q.InsertLibraryChanges(ctx, dbq.InsertLibraryChangesParams{
+		EntityType: string(entityType),
+		EntityIds:  entityIDs,
+		Op:         string(op),
+	}); err != nil {
+		return fmt.Errorf("sync.LogChanges(%s, %d ids, %s): %w", entityType, len(entityIDs), op, err)
+	}
+	return nil
+}
+
 // FormatUUID renders a pgtype.UUID as the canonical 8-4-4-4-12 hex form.
 // Returns "" if the UUID is not valid.
 func FormatUUID(u pgtype.UUID) string {