fix(496): give music videos a per-library server identity; itemId diff + soft trash

Music videos carried no server identity, so JellyfinMusicVideoLibraryScanner had to
reconcile by a (LibraryPathId, path) diff and HARD-delete the remainder. A file served
by two libraries with overlapping local paths is a single row owned by whichever library
scanned it first, so that owner's sweep destroyed a row another library still served —
taking collection membership and playout references with it, irreversibly.

This is #494's deferred "option 2":

- New JellyfinMusicVideo : MusicVideo (ItemId/Etag), mirroring JellyfinMovie — TPT table,
  varchar(36), ItemId index. Dual-provider migration Add_JellyfinMusicVideo.
- New IMediaServerMusicVideoRepository + JellyfinMusicVideoRepository: itemId-keyed
  existing-set/lookup and Flag{Normal,Unavailable,FileNotFound} seams, all scoped per
  library via LibraryPath.LibraryId.
- New MediaServerMusicVideoLibraryScanner base; JellyfinMusicVideoLibraryScanner folds
  onto it and keeps the #177/#488/#497/#500 metadata-reconcile logic verbatim.
- The sweep now soft-trashes (FileNotFound) instead of deleting, so removal is reversible
  and EmptyTrash-governed. DeleteEmptyArtists consequently no longer fires from a sweep.
- Pre-identity rows are ADOPTED in place: the identity row is inserted against the same
  MediaItem id, scoped to the scanned library's own LibraryPath, so collection membership
  survives and a local/second-library row is never hijacked.
- AddMusicVideo normalizes Path/PathHash to the path-REPLACED local path; the projection
  fills them from the server-reported path, which would break every later PathHash lookup.

Docs: scan.musicvideo-reconciliation relocated to docs/decisions/archive/scan.md as
superseded; new active record scan.musicvideo-server-identity.

fixes #496

ErsatzTV.Core/Domain/MediaItem/JellyfinMusicVideo.cs

@@ -0,0 +1,7 @@
+namespace ErsatzTV.Core.Domain;
+
+public class JellyfinMusicVideo : MusicVideo
+{
+    public string ItemId { get; set; }
+    public string Etag { get; set; }
+}

ErsatzTV.Core/Interfaces/Jellyfin/IJellyfinApiClient.cs

@@ -21,7 +21,7 @@ public interface IJellyfinApiClient
         JellyfinLibrary library,
         MediaServerProjectionFailureCounter projectionFailures = null);
 
-    IAsyncEnumerable<Tuple<MusicVideo, int>> GetMusicVideoLibraryItems(
+    IAsyncEnumerable<Tuple<JellyfinMusicVideo, int>> GetMusicVideoLibraryItems(
         string address,
         string authorizationHeader,
         JellyfinLibrary library,

ErsatzTV.Core/Interfaces/Repositories/IJellyfinMusicVideoRepository.cs

@@ -0,0 +1,10 @@
+using ErsatzTV.Core.Domain;
+using ErsatzTV.Core.Jellyfin;
+
+namespace ErsatzTV.Core.Interfaces.Repositories;
+
+public interface
+    IJellyfinMusicVideoRepository : IMediaServerMusicVideoRepository<JellyfinLibrary, JellyfinMusicVideo,
+    JellyfinItemEtag>
+{
+}

ErsatzTV.Core/Interfaces/Repositories/IMediaServerMusicVideoRepository.cs

@@ -0,0 +1,26 @@
+using ErsatzTV.Core.Domain;
+using ErsatzTV.Core.Metadata;
+
+namespace ErsatzTV.Core.Interfaces.Repositories;
+
+public interface IMediaServerMusicVideoRepository<in TLibrary, TMusicVideo, TEtag> where TLibrary : Library
+    where TMusicVideo : MusicVideo
+    where TEtag : MediaServerItemEtag
+{
+    Task<List<TEtag>> GetExistingMusicVideos(TLibrary library);
+    Task<Option<int>> FlagNormal(TLibrary library, TMusicVideo musicVideo);
+    Task<Option<int>> FlagUnavailable(TLibrary library, TMusicVideo musicVideo);
+    Task<List<int>> FlagFileNotFound(TLibrary library, List<string> musicVideoItemIds);
+
+    // Unlike the movie/other-video seams, GetOrAdd takes the resolved Artist and LibraryFolder: a music video is
+    // owned by an Artist (FK, not null) and ersatztv#488 requires the media file to carry its LibraryFolderId.
+    Task<Either<BaseError, MediaItemScanResult<TMusicVideo>>> GetOrAdd(
+        TLibrary library,
+        Artist artist,
+        LibraryFolder libraryFolder,
+        TMusicVideo item,
+        bool deepScan,
+        CancellationToken cancellationToken);
+
+    Task<Unit> SetEtag(TMusicVideo musicVideo, string etag);
+}

ErsatzTV.Infrastructure.MySql/Migrations/20260725122358_Add_JellyfinMusicVideo.cs

@@ -0,0 +1,48 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace ErsatzTV.Infrastructure.MySql.Migrations
+{
+    /// <inheritdoc />
+    public partial class Add_JellyfinMusicVideo : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.CreateTable(
+                name: "JellyfinMusicVideo",
+                columns: table => new
+                {
+                    Id = table.Column<int>(type: "int", nullable: false),
+                    ItemId = table.Column<string>(type: "varchar(36)", unicode: false, maxLength: 36, nullable: true)
+                        .Annotation("MySql:CharSet", "utf8mb4"),
+                    Etag = table.Column<string>(type: "varchar(36)", unicode: false, maxLength: 36, nullable: true)
+                        .Annotation("MySql:CharSet", "utf8mb4")
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_JellyfinMusicVideo", x => x.Id);
+                    table.ForeignKey(
+                        name: "FK_JellyfinMusicVideo_MusicVideo_Id",
+                        column: x => x.Id,
+                        principalTable: "MusicVideo",
+                        principalColumn: "Id",
+                        onDelete: ReferentialAction.Cascade);
+                })
+                .Annotation("MySql:CharSet", "utf8mb4");
+
+            migrationBuilder.CreateIndex(
+                name: "IX_JellyfinMusicVideo_ItemId",
+                table: "JellyfinMusicVideo",
+                column: "ItemId");
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropTable(
+                name: "JellyfinMusicVideo");
+        }
+    }
+}

ErsatzTV.Infrastructure.MySql/Migrations/TvContextModelSnapshot.cs

@@ -4452,6 +4452,25 @@ namespace ErsatzTV.Infrastructure.MySql.Migrations
                     b.ToTable("PlexMovie", (string)null);
                 });
 
+            modelBuilder.Entity("ErsatzTV.Core.Domain.JellyfinMusicVideo", b =>
+                {
+                    b.HasBaseType("ErsatzTV.Core.Domain.MusicVideo");
+
+                    b.Property<string>("Etag")
+                        .HasMaxLength(36)
+                        .IsUnicode(false)
+                        .HasColumnType("varchar(36)");
+
+                    b.Property<string>("ItemId")
+                        .HasMaxLength(36)
+                        .IsUnicode(false)
+                        .HasColumnType("varchar(36)");
+
+                    b.HasIndex("ItemId");
+
+                    b.ToTable("JellyfinMusicVideo", (string)null);
+                });
+
             modelBuilder.Entity("ErsatzTV.Core.Domain.PlexOtherVideo", b =>
                 {
                     b.HasBaseType("ErsatzTV.Core.Domain.OtherVideo");
@@ -6730,6 +6749,15 @@ namespace ErsatzTV.Infrastructure.MySql.Migrations
                         .IsRequired();
                 });
 
+            modelBuilder.Entity("ErsatzTV.Core.Domain.JellyfinMusicVideo", b =>
+                {
+                    b.HasOne("ErsatzTV.Core.Domain.MusicVideo", null)
+                        .WithOne()
+                        .HasForeignKey("ErsatzTV.Core.Domain.JellyfinMusicVideo", "Id")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+                });
+
             modelBuilder.Entity("ErsatzTV.Core.Domain.PlexOtherVideo", b =>
                 {
                     b.HasOne("ErsatzTV.Core.Domain.OtherVideo", null)

ErsatzTV.Infrastructure.Sqlite/Migrations/20260725122152_Add_JellyfinMusicVideo.cs

@@ -0,0 +1,46 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace ErsatzTV.Infrastructure.Sqlite.Migrations
+{
+    /// <inheritdoc />
+    public partial class Add_JellyfinMusicVideo : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.CreateTable(
+                name: "JellyfinMusicVideo",
+                columns: table => new
+                {
+                    Id = table.Column<int>(type: "INTEGER", nullable: false)
+                        .Annotation("Sqlite:Autoincrement", true),
+                    ItemId = table.Column<string>(type: "TEXT", unicode: false, maxLength: 36, nullable: true),
+                    Etag = table.Column<string>(type: "TEXT", unicode: false, maxLength: 36, nullable: true)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_JellyfinMusicVideo", x => x.Id);
+                    table.ForeignKey(
+                        name: "FK_JellyfinMusicVideo_MusicVideo_Id",
+                        column: x => x.Id,
+                        principalTable: "MusicVideo",
+                        principalColumn: "Id",
+                        onDelete: ReferentialAction.Cascade);
+                });
+
+            migrationBuilder.CreateIndex(
+                name: "IX_JellyfinMusicVideo_ItemId",
+                table: "JellyfinMusicVideo",
+                column: "ItemId");
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropTable(
+                name: "JellyfinMusicVideo");
+        }
+    }
+}

ErsatzTV.Infrastructure.Sqlite/Migrations/TvContextModelSnapshot.cs

@@ -4277,6 +4277,25 @@ namespace ErsatzTV.Infrastructure.Sqlite.Migrations
                     b.ToTable("PlexMovie", (string)null);
                 });
 
+            modelBuilder.Entity("ErsatzTV.Core.Domain.JellyfinMusicVideo", b =>
+                {
+                    b.HasBaseType("ErsatzTV.Core.Domain.MusicVideo");
+
+                    b.Property<string>("Etag")
+                        .HasMaxLength(36)
+                        .IsUnicode(false)
+                        .HasColumnType("TEXT");
+
+                    b.Property<string>("ItemId")
+                        .HasMaxLength(36)
+                        .IsUnicode(false)
+                        .HasColumnType("TEXT");
+
+                    b.HasIndex("ItemId");
+
+                    b.ToTable("JellyfinMusicVideo", (string)null);
+                });
+
             modelBuilder.Entity("ErsatzTV.Core.Domain.PlexOtherVideo", b =>
                 {
                     b.HasBaseType("ErsatzTV.Core.Domain.OtherVideo");
@@ -6555,6 +6574,15 @@ namespace ErsatzTV.Infrastructure.Sqlite.Migrations
                         .IsRequired();
                 });
 
+            modelBuilder.Entity("ErsatzTV.Core.Domain.JellyfinMusicVideo", b =>
+                {
+                    b.HasOne("ErsatzTV.Core.Domain.MusicVideo", null)
+                        .WithOne()
+                        .HasForeignKey("ErsatzTV.Core.Domain.JellyfinMusicVideo", "Id")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+                });
+
             modelBuilder.Entity("ErsatzTV.Core.Domain.PlexOtherVideo", b =>
                 {
                     b.HasOne("ErsatzTV.Core.Domain.OtherVideo", null)

ErsatzTV.Infrastructure/Data/Configurations/JellyfinMusicVideoConfiguration.cs

@@ -0,0 +1,23 @@
+using ErsatzTV.Core.Domain;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace ErsatzTV.Infrastructure.Data.Configurations;
+
+public class JellyfinMusicVideoConfiguration : IEntityTypeConfiguration<JellyfinMusicVideo>
+{
+    public void Configure(EntityTypeBuilder<JellyfinMusicVideo> builder)
+    {
+        builder.ToTable("JellyfinMusicVideo");
+
+        builder.Property(mv => mv.Etag)
+            .HasMaxLength(36)
+            .IsUnicode(false);
+
+        builder.Property(mv => mv.ItemId)
+            .HasMaxLength(36)
+            .IsUnicode(false);
+
+        builder.HasIndex(mv => mv.ItemId);
+    }
+}

ErsatzTV.Infrastructure/Data/Repositories/JellyfinMusicVideoRepository.cs

@@ -0,0 +1,348 @@
+using Dapper;
+using ErsatzTV.Core;
+using ErsatzTV.Core.Domain;
+using ErsatzTV.Core.Errors;
+using ErsatzTV.Core.Extensions;
+using ErsatzTV.Core.Interfaces.Repositories;
+using ErsatzTV.Core.Jellyfin;
+using ErsatzTV.Core.Metadata;
+using ErsatzTV.Infrastructure.Extensions;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging;
+
+namespace ErsatzTV.Infrastructure.Data.Repositories;
+
+public class JellyfinMusicVideoRepository : IJellyfinMusicVideoRepository
+{
+    private readonly IDbContextFactory<TvContext> _dbContextFactory;
+    private readonly ILogger<JellyfinMusicVideoRepository> _logger;
+
+    public JellyfinMusicVideoRepository(
+        IDbContextFactory<TvContext> dbContextFactory,
+        ILogger<JellyfinMusicVideoRepository> logger)
+    {
+        _dbContextFactory = dbContextFactory;
+        _logger = logger;
+    }
+
+    public async Task<List<JellyfinItemEtag>> GetExistingMusicVideos(JellyfinLibrary library)
+    {
+        await using TvContext dbContext = await _dbContextFactory.CreateDbContextAsync();
+        return await dbContext.Connection.QueryAsync<JellyfinItemEtag>(
+                @"SELECT ItemId, Etag, MI.State FROM JellyfinMusicVideo
+                      INNER JOIN MusicVideo M on JellyfinMusicVideo.Id = M.Id
+                      INNER JOIN MediaItem MI on M.Id = MI.Id
+                      INNER JOIN LibraryPath LP on MI.LibraryPathId = LP.Id
+                      WHERE LP.LibraryId = @LibraryId",
+                new { LibraryId = library.Id })
+            .Map(result => result.ToList());
+    }
+
+    public async Task<Option<int>> FlagNormal(JellyfinLibrary library, JellyfinMusicVideo musicVideo)
+    {
+        if (musicVideo.State is MediaItemState.Normal)
+        {
+            return Option<int>.None;
+        }
+
+        await using TvContext dbContext = await _dbContextFactory.CreateDbContextAsync();
+
+        musicVideo.State = MediaItemState.Normal;
+
+        Option<int> maybeId = await dbContext.Connection.ExecuteScalarAsync<int>(
+            @"SELECT JellyfinMusicVideo.Id FROM JellyfinMusicVideo
+              INNER JOIN MediaItem MI ON MI.Id = JellyfinMusicVideo.Id
+              INNER JOIN LibraryPath LP on MI.LibraryPathId = LP.Id AND LibraryId = @LibraryId
+              WHERE JellyfinMusicVideo.ItemId = @ItemId",
+            new { LibraryId = library.Id, musicVideo.ItemId });
+
+        foreach (int id in maybeId)
+        {
+            return await dbContext.Connection.ExecuteAsync(
+                "UPDATE MediaItem SET State = 0 WHERE Id = @Id AND State != 0",
+                new { Id = id }).Map(count => count > 0 ? Some(id) : None);
+        }
+
+        return None;
+    }
+
+    public async Task<Option<int>> FlagUnavailable(JellyfinLibrary library, JellyfinMusicVideo musicVideo)
+    {
+        if (musicVideo.State is MediaItemState.Unavailable)
+        {
+            return Option<int>.None;
+        }
+
+        await using TvContext dbContext = await _dbContextFactory.CreateDbContextAsync();
+
+        musicVideo.State = MediaItemState.Unavailable;
+
+        Option<int> maybeId = await dbContext.Connection.ExecuteScalarAsync<int>(
+            @"SELECT JellyfinMusicVideo.Id FROM JellyfinMusicVideo
+              INNER JOIN MediaItem MI ON MI.Id = JellyfinMusicVideo.Id
+              INNER JOIN LibraryPath LP on MI.LibraryPathId = LP.Id AND LibraryId = @LibraryId
+              WHERE JellyfinMusicVideo.ItemId = @ItemId",
+            new { LibraryId = library.Id, musicVideo.ItemId });
+
+        foreach (int id in maybeId)
+        {
+            return await dbContext.Connection.ExecuteAsync(
+                "UPDATE MediaItem SET State = 2 WHERE Id = @Id AND State != 2",
+                new { Id = id }).Map(count => count > 0 ? Some(id) : None);
+        }
+
+        return None;
+    }
+
+    public async Task<List<int>> FlagFileNotFound(JellyfinLibrary library, List<string> musicVideoItemIds)
+    {
+        if (musicVideoItemIds.Count == 0)
+        {
+            return [];
+        }
+
+        await using TvContext dbContext = await _dbContextFactory.CreateDbContextAsync();
+
+        List<int> ids = await dbContext.Connection.QueryAsync<int>(
+                @"SELECT M.Id
+                FROM MediaItem M
+                INNER JOIN JellyfinMusicVideo ON JellyfinMusicVideo.Id = M.Id
+                INNER JOIN LibraryPath LP on M.LibraryPathId = LP.Id AND LP.LibraryId = @LibraryId
+                WHERE JellyfinMusicVideo.ItemId IN @MusicVideoItemIds",
+                new { LibraryId = library.Id, MusicVideoItemIds = musicVideoItemIds })
+            .Map(result => result.ToList());
+
+        await dbContext.Connection.ExecuteAsync(
+            "UPDATE MediaItem SET State = 1 WHERE Id IN @Ids AND State != 1",
+            new { Ids = ids });
+
+        return ids;
+    }
+
+    public async Task<Either<BaseError, MediaItemScanResult<JellyfinMusicVideo>>> GetOrAdd(
+        JellyfinLibrary library,
+        Artist artist,
+        LibraryFolder libraryFolder,
+        JellyfinMusicVideo item,
+        bool deepScan,
+        CancellationToken cancellationToken)
+    {
+        await using TvContext dbContext = await _dbContextFactory.CreateDbContextAsync(cancellationToken);
+
+        string path = item.GetHeadVersion().MediaFiles.Head().Path;
+
+        Option<JellyfinMusicVideo> maybeExisting = await GetByItemId(dbContext, item.ItemId, cancellationToken);
+
+        // ersatztv#496: rows created before this library gained per-item identity (and rows created by the
+        // pre-#496 path-keyed scanner) carry no JellyfinMusicVideo row, so they can never be found by ItemId.
+        // Adopt them IN PLACE — insert the identity row against the SAME MediaItem id — rather than deleting and
+        // re-adding: the MediaItem id is referenced by CollectionItem, playouts, artwork and the search index, so
+        // a delete/re-add would silently drop collection membership and break built playouts.
+        //
+        // Adoption is scoped to THIS library's own library path, which is the whole point of the issue: a music
+        // video owned by a local library (MusicVideoFolderScanner uses the same MusicVideo table) or by a second
+        // Jellyfin library must never be hijacked into this library's identity.
+        if (maybeExisting.IsNone)
+        {
+            Option<int> maybeAdopted = await AdoptExistingMusicVideo(
+                dbContext,
+                library.Paths.Head().Id,
+                path,
+                item.ItemId);
+
+            if (maybeAdopted.IsSome)
+            {
+                _logger.LogDebug(
+                    "ADOPT: existing music video {Path} now carries Jellyfin item id {ItemId}",
+                    path,
+                    item.ItemId);
+
+                // the identity row is written with an empty etag, so the existing-item path below always sees an
+                // etag mismatch and refreshes the adopted row exactly like any other changed item
+                maybeExisting = await GetByItemId(dbContext, item.ItemId, cancellationToken);
+            }
+        }
+
+        foreach (JellyfinMusicVideo existing in maybeExisting)
+        {
+            var result = new MediaItemScanResult<JellyfinMusicVideo>(existing) { IsAdded = false };
+
+            // identity is now the server item id, so the file behind it can move; keep the local path, owning
+            // folder and artist in sync when the server says the item changed
+            if (existing.Etag != item.Etag || deepScan)
+            {
+                await UpdateMusicVideoFile(dbContext, existing.Id, artist.Id, libraryFolder.Id, path);
+                existing.ArtistId = artist.Id;
+                existing.Artist = artist;
+                result.IsUpdated = true;
+            }
+            else if (existing.ArtistId != artist.Id)
+            {
+                await dbContext.Connection.ExecuteAsync(
+                    "UPDATE MusicVideo SET ArtistId = @ArtistId WHERE Id = @Id",
+                    new { Id = existing.Id, ArtistId = artist.Id });
+
+                existing.ArtistId = artist.Id;
+                existing.Artist = artist;
+                result.IsUpdated = true;
+            }
+
+            return result;
+        }
+
+        return await AddMusicVideo(dbContext, library, artist, libraryFolder, item, path, cancellationToken);
+    }
+
+    public async Task<Unit> SetEtag(JellyfinMusicVideo musicVideo, string etag)
+    {
+        await using TvContext dbContext = await _dbContextFactory.CreateDbContextAsync();
+        return await dbContext.Connection.ExecuteAsync(
+            "UPDATE JellyfinMusicVideo SET Etag = @Etag WHERE Id = @Id",
+            new { Etag = etag, musicVideo.Id }).Map(_ => Unit.Default);
+    }
+
+    // Mirrors MusicVideoRepository.GetOrAdd's eager-load set: the scanner's metadata reconcile (ersatztv#497)
+    // only reconciles collections that are loaded here, so this list is load-bearing, not cosmetic.
+    private static async Task<Option<JellyfinMusicVideo>> GetByItemId(
+        TvContext dbContext,
+        string itemId,
+        CancellationToken cancellationToken) =>
+        await dbContext.JellyfinMusicVideos
+            .AsNoTracking()
+            .Include(mv => mv.Artist)
+            .ThenInclude(a => a.ArtistMetadata)
+            .Include(mv => mv.MusicVideoMetadata)
+            .ThenInclude(mvm => mvm.Artwork)
+            .Include(mv => mv.MusicVideoMetadata)
+            .ThenInclude(mvm => mvm.Artists)
+            .Include(mv => mv.MusicVideoMetadata)
+            .ThenInclude(mvm => mvm.Genres)
+            .Include(mv => mv.MusicVideoMetadata)
+            .ThenInclude(mvm => mvm.Tags)
+            .Include(mv => mv.MusicVideoMetadata)
+            .ThenInclude(mvm => mvm.Studios)
+            .Include(mv => mv.MusicVideoMetadata)
+            .ThenInclude(mvm => mvm.Directors)
+            .Include(mv => mv.LibraryPath)
+            .ThenInclude(lp => lp.Library)
+            .Include(mv => mv.MediaVersions)
+            .ThenInclude(mv => mv.MediaFiles)
+            .Include(mv => mv.MediaVersions)
+            .ThenInclude(mv => mv.Streams)
+            .Include(mv => mv.TraktListItems)
+            .ThenInclude(tli => tli.TraktList)
+            .SelectOneAsync(mv => mv.ItemId, mv => mv.ItemId == itemId, cancellationToken);
+
+    private static async Task<Option<int>> AdoptExistingMusicVideo(
+        TvContext dbContext,
+        int libraryPathId,
+        string path,
+        string itemId)
+    {
+        Option<int> maybeId = await dbContext.Connection.QuerySingleOrDefaultAsync<int?>(
+                @"SELECT M.Id
+                    FROM MusicVideo M
+                    INNER JOIN MediaItem MI on M.Id = MI.Id
+                    INNER JOIN MediaVersion MV on M.Id = MV.MusicVideoId
+                    INNER JOIN MediaFile MF on MV.Id = MF.MediaVersionId
+                    WHERE MI.LibraryPathId = @LibraryPathId
+                      AND MF.PathHash = @PathHash
+                      AND NOT EXISTS (SELECT 1 FROM JellyfinMusicVideo J WHERE J.Id = M.Id)",
+                new { LibraryPathId = libraryPathId, PathHash = PathUtils.GetPathHash(path) })
+            .Map(Optional);
+
+        foreach (int id in maybeId)
+        {
+            await dbContext.Connection.ExecuteAsync(
+                "INSERT INTO JellyfinMusicVideo (Id, ItemId, Etag) VALUES (@Id, @ItemId, '')",
+                new { Id = id, ItemId = itemId });
+
+            return id;
+        }
+
+        return None;
+    }
+
+    private static async Task UpdateMusicVideoFile(
+        TvContext dbContext,
+        int musicVideoId,
+        int artistId,
+        int libraryFolderId,
+        string path)
+    {
+        await dbContext.Connection.ExecuteAsync(
+            "UPDATE MusicVideo SET ArtistId = @ArtistId WHERE Id = @Id",
+            new { Id = musicVideoId, ArtistId = artistId });
+
+        await dbContext.Connection.ExecuteAsync(
+            @"UPDATE MediaFile SET Path = @Path, PathHash = @PathHash, LibraryFolderId = @LibraryFolderId
+                WHERE Id IN (SELECT MF.Id
+                               FROM MediaFile MF
+                               INNER JOIN MediaVersion MV on MF.MediaVersionId = MV.Id
+                               WHERE MV.MusicVideoId = @Id)",
+            new
+            {
+                Id = musicVideoId,
+                Path = path,
+                PathHash = PathUtils.GetPathHash(path),
+                LibraryFolderId = libraryFolderId
+            });
+    }
+
+    private async Task<Either<BaseError, MediaItemScanResult<JellyfinMusicVideo>>> AddMusicVideo(
+        TvContext dbContext,
+        JellyfinLibrary library,
+        Artist artist,
+        LibraryFolder libraryFolder,
+        JellyfinMusicVideo musicVideo,
+        string path,
+        CancellationToken cancellationToken)
+    {
+        try
+        {
+            if (await MediaItemRepository.MediaFileAlreadyExists(
+                    path,
+                    library.Paths.Head().Id,
+                    dbContext,
+                    _logger,
+                    cancellationToken))
+            {
+                return new MediaFileAlreadyExists();
+            }
+
+            // blank out etag for initial save in case other updates fail
+            string etag = musicVideo.Etag;
+            musicVideo.Etag = string.Empty;
+
+            musicVideo.ArtistId = artist.Id;
+            musicVideo.LibraryPathId = library.Paths.Head().Id;
+
+            // Music videos store the PATH-REPLACED local path (they always have — the pre-#496 scanner passed the
+            // replaced path straight into GetOrAdd), while the projection fills Path/PathHash from the path the
+            // media server reported. Normalize both here, or the stored hash would be the hash of the server-side
+            // path and every later lookup by PathHash — MediaFileAlreadyExists, and #496's adoption probe — would
+            // miss the row it is meant to find.
+            MediaFile file = musicVideo.GetHeadVersion().MediaFiles.Head();
+            file.Path = path;
+            file.PathHash = PathUtils.GetPathHash(path);
+            file.LibraryFolderId = libraryFolder.Id;
+
+            await dbContext.AddAsync(musicVideo, cancellationToken);
+            await dbContext.SaveChangesAsync(cancellationToken);
+
+            // restore etag
+            musicVideo.Etag = etag;
+
+            await dbContext.Entry(musicVideo).Reference(mv => mv.Artist).LoadAsync(cancellationToken);
+            await dbContext.Entry(musicVideo.Artist).Collection(a => a.ArtistMetadata).LoadAsync(cancellationToken);
+            await dbContext.Entry(musicVideo).Reference(mv => mv.LibraryPath).LoadAsync(cancellationToken);
+            await dbContext.Entry(musicVideo.LibraryPath).Reference(lp => lp.Library).LoadAsync(cancellationToken);
+
+            return new MediaItemScanResult<JellyfinMusicVideo>(musicVideo) { IsAdded = true };
+        }
+        catch (Exception ex)
+        {
+            return BaseError.New(ex.ToString());
+        }
+    }
+}

ErsatzTV.Infrastructure/Data/TvContext.cs

@@ -92,6 +92,7 @@ public class TvContext : DbContext
     public DbSet<PlexEpisode> PlexEpisodes { get; set; }
     public DbSet<PlexCollection> PlexCollections { get; set; }
     public DbSet<JellyfinMovie> JellyfinMovies { get; set; }
+    public DbSet<JellyfinMusicVideo> JellyfinMusicVideos { get; set; }
     public DbSet<JellyfinShow> JellyfinShows { get; set; }
     public DbSet<JellyfinSeason> JellyfinSeasons { get; set; }
     public DbSet<JellyfinEpisode> JellyfinEpisodes { get; set; }

ErsatzTV.Infrastructure/Jellyfin/JellyfinApiClient.cs

@@ -95,7 +95,7 @@ public class JellyfinApiClient : IJellyfinApiClient
             (maybeLibrary, item) => WithLibrary(maybeLibrary, lib => ProjectToMovie(lib, item)),
             projectionFailures);
 
-    public IAsyncEnumerable<Tuple<MusicVideo, int>> GetMusicVideoLibraryItems(
+    public IAsyncEnumerable<Tuple<JellyfinMusicVideo, int>> GetMusicVideoLibraryItems(
         string address,
         string authorizationHeader,
         JellyfinLibrary library,
@@ -701,7 +701,7 @@ public class JellyfinApiClient : IJellyfinApiClient
         return metadata;
     }
 
-    private MediaServerProjectionResult<MusicVideo> ProjectToMusicVideo(
+    private MediaServerProjectionResult<JellyfinMusicVideo> ProjectToMusicVideo(
         JellyfinLibrary library,
         JellyfinLibraryItemResponse item)
     {
@@ -709,13 +709,13 @@ public class JellyfinApiClient : IJellyfinApiClient
         {
             if (item.LocationType != "FileSystem")
             {
-                return MediaServerProjectionResult<MusicVideo>.Skipped();
+                return MediaServerProjectionResult<JellyfinMusicVideo>.Skipped();
             }
 
             if (Path.GetExtension(item.Path)?.ToLowerInvariant() == ".strm")
             {
                 _logger.LogInformation("STRM files are not supported; skipping {Path}", item.Path);
-                return MediaServerProjectionResult<MusicVideo>.Skipped();
+                return MediaServerProjectionResult<JellyfinMusicVideo>.Skipped();
             }
 
             string path = item.Path ?? string.Empty;
@@ -752,8 +752,10 @@ public class JellyfinApiClient : IJellyfinApiClient
 
             MusicVideoMetadata metadata = ProjectToMusicVideoMetadata(item);
 
-            var musicVideo = new MusicVideo
+            var musicVideo = new JellyfinMusicVideo
             {
+                ItemId = item.Id,
+                Etag = item.Etag,
                 MediaVersions = [version],
                 MusicVideoMetadata = [metadata],
                 TraktListItems = []
@@ -764,7 +766,7 @@ public class JellyfinApiClient : IJellyfinApiClient
         catch (Exception ex)
         {
             _logger.LogWarning(ex, "Error projecting Jellyfin music video");
-            return MediaServerProjectionResult<MusicVideo>.Failed();
+            return MediaServerProjectionResult<JellyfinMusicVideo>.Failed();
         }
     }
 

ErsatzTV.Scanner/Core/Jellyfin/JellyfinMusicVideoLibraryScanner.cs

@@ -1,6 +1,6 @@
+using System.IO.Abstractions;
 using ErsatzTV.Core;
 using ErsatzTV.Core.Domain;
-using ErsatzTV.Core.Errors;
 using ErsatzTV.Core.Extensions;
 using ErsatzTV.Core.Interfaces.Jellyfin;
 using ErsatzTV.Core.Interfaces.Repositories;
@@ -12,40 +12,44 @@ using Microsoft.Extensions.Logging;
 
 namespace ErsatzTV.Scanner.Core.Jellyfin;
 
-public class JellyfinMusicVideoLibraryScanner : IJellyfinMusicVideoLibraryScanner
+public class JellyfinMusicVideoLibraryScanner :
+    MediaServerMusicVideoLibraryScanner<JellyfinConnectionParameters, JellyfinLibrary, JellyfinMusicVideo,
+        JellyfinItemEtag>,
+    IJellyfinMusicVideoLibraryScanner
 {
-    private const string UnknownArtist = "Unknown Artist";
-
-    private readonly IArtistRepository _artistRepository;
     private readonly IJellyfinApiClient _jellyfinApiClient;
-    private readonly IJellyfinPathReplacementService _pathReplacementService;
+    private readonly IJellyfinMusicVideoRepository _jellyfinMusicVideoRepository;
-    private readonly ILibraryRepository _libraryRepository;
-    private readonly ILogger<JellyfinMusicVideoLibraryScanner> _logger;
     private readonly IMediaSourceRepository _mediaSourceRepository;
     private readonly IMetadataRepository _metadataRepository;
     private readonly IMusicVideoRepository _musicVideoRepository;
-    private readonly IScannerProxy _scannerProxy;
+    private readonly IJellyfinPathReplacementService _pathReplacementService;
 
     public JellyfinMusicVideoLibraryScanner(
         IScannerProxy scannerProxy,
         IJellyfinApiClient jellyfinApiClient,
+        IJellyfinMusicVideoRepository jellyfinMusicVideoRepository,
         IJellyfinPathReplacementService pathReplacementService,
         IMediaSourceRepository mediaSourceRepository,
         IArtistRepository artistRepository,
         IMusicVideoRepository musicVideoRepository,
         ILibraryRepository libraryRepository,
         IMetadataRepository metadataRepository,
+        IFileSystem fileSystem,
         ILogger<JellyfinMusicVideoLibraryScanner> logger)
+        : base(
+            scannerProxy,
+            fileSystem,
+            artistRepository,
+            libraryRepository,
+            metadataRepository,
+            logger)
     {
-        _scannerProxy = scannerProxy;
         _jellyfinApiClient = jellyfinApiClient;
+        _jellyfinMusicVideoRepository = jellyfinMusicVideoRepository;
         _pathReplacementService = pathReplacementService;
         _mediaSourceRepository = mediaSourceRepository;
-        _artistRepository = artistRepository;
         _musicVideoRepository = musicVideoRepository;
-        _libraryRepository = libraryRepository;
         _metadataRepository = metadataRepository;
-        _logger = logger;
     }
 
     public async Task<Either<BaseError, Unit>> ScanLibrary(
@@ -53,212 +57,50 @@ public class JellyfinMusicVideoLibraryScanner : IJellyfinMusicVideoLibraryScanne
         JellyfinLibrary library,
         bool deepScan,
         CancellationToken cancellationToken)
-    {
-        try
     {
         Option<LibraryPath> maybeLibraryPath = Optional(library.Paths).Flatten().HeadOrNone();
-            return await maybeLibraryPath.Match(
+        foreach (LibraryPath libraryPath in maybeLibraryPath)
-                libraryPath => ScanLibrary(connectionParameters, library, libraryPath, cancellationToken),
-                () => Task.FromResult<Either<BaseError, Unit>>(
-                    BaseError.New($"Jellyfin library {library.Id} has no library path")));
-        }
-        catch (Exception ex) when (ex is TaskCanceledException or OperationCanceledException)
-        {
-            return new ScanCanceled();
-        }
-    }
-
-    private async Task<Either<BaseError, Unit>> ScanLibrary(
-        JellyfinConnectionParameters connectionParameters,
-        JellyfinLibrary library,
-        LibraryPath libraryPath,
-        CancellationToken cancellationToken)
         {
             List<JellyfinPathReplacement> pathReplacements =
                 await _mediaSourceRepository.GetJellyfinPathReplacements(library.MediaSourceId);
 
-        var processed = 0;
+            string GetLocalPath(JellyfinMusicVideo musicVideo) =>
-        var incomingPaths = new List<string>();
-
-        // #484: one counter per enumeration, created here and read only after the enumeration completes.
-        // It is never a field on the (singleton) api client, so concurrent scans of different libraries
-        // cannot leak failures into each other's sweep decision.
-        var projectionFailures = new MediaServerProjectionFailureCounter();
-
-        await foreach ((MusicVideo incoming, int totalCount) in _jellyfinApiClient
-                           .GetMusicVideoLibraryItems(
-                               connectionParameters.Address,
-                               connectionParameters.AuthorizationHeader,
-                               library,
-                               projectionFailures)
-                           .WithCancellation(cancellationToken))
-        {
-            if (cancellationToken.IsCancellationRequested)
-            {
-                return new ScanCanceled();
-            }
-
-            processed++;
-            decimal percentCompletion = totalCount == 0 ? 1 : Math.Clamp((decimal)processed / totalCount, 0, 1);
-            if (!await _scannerProxy.UpdateProgress(percentCompletion, cancellationToken))
-            {
-                return new ScanCanceled();
-            }
-
-            incomingPaths.Add(GetLocalPath(pathReplacements, incoming));
-
-            Either<BaseError, MediaItemScanResult<MusicVideo>> maybeMusicVideo =
-                await ProcessMusicVideo(library, libraryPath, pathReplacements, incoming, cancellationToken);
-
-            foreach (BaseError error in maybeMusicVideo.LeftToSeq())
-            {
-                _logger.LogWarning("Error processing Jellyfin music video: {Error}", error.Value);
-            }
-
-            foreach (MediaItemScanResult<MusicVideo> result in maybeMusicVideo.RightToSeq()
-                         .Filter(result => result.IsAdded || result.IsUpdated))
-            {
-                if (!await _scannerProxy.ReindexMediaItems([result.Item.Id], cancellationToken))
-                {
-                    _logger.LogWarning("Failed to reindex media items from scanner process");
-                }
-            }
-        }
-
-        await TrashMissingMusicVideos(
-            library,
-            libraryPath,
-            incomingPaths,
-            projectionFailures,
-            cancellationToken);
-
-        return Unit.Default;
-    }
-
-    // ersatztv#494: remove music videos (and now-empty artists) that Jellyfin no longer reports.
-    //
-    // Identity is LIBRARY-SCOPED by (LibraryPathId, path): FindMusicVideoPaths and DeleteByPath both filter
-    // LibraryPathId AND join the concrete MusicVideo table, so this can never touch a Movie/Show that shares
-    // the same LibraryPath (a mixed library) — the cross-delete safety is a property of those queries, not of
-    // the media kind. Unlike the MediaServer{Movie,Television,OtherVideo} base scanners, music videos carry no
-    // server ItemId/Etag (there is no JellyfinMusicVideo entity), so we diff on the local path instead of the
-    // server item id, and hard-delete rather than soft-trash (there is no per-item FileNotFound seam here).
-    //
-    // Known limitation: MusicVideoRepository.GetOrAdd dedups a path GLOBALLY (no LibraryPathId predicate), so a
-    // file served by two libraries with overlapping local paths is a single row owned by whichever library
-    // scanned it first. If that owning library later stops reporting the file while another library still
-    // serves it, this sweep removes the shared row. A proper fix needs per-library music-video identity (a
-    // JellyfinMusicVideo etag entity + migration) — the issue's deferred "option 2"; tracked as a follow-up.
-    private async Task TrashMissingMusicVideos(
-        JellyfinLibrary library,
-        LibraryPath libraryPath,
-        List<string> incomingPaths,
-        MediaServerProjectionFailureCounter projectionFailures,
-        CancellationToken cancellationToken)
-    {
-        var existingPaths = (await _musicVideoRepository.FindMusicVideoPaths(libraryPath)).ToList();
-
-        // #477: refuse the sweep when a successful fetch returned zero items but rows exist locally — an empty
-        // incoming set is indistinguishable from a transient error and would otherwise wipe the whole library.
-        // #484: also refuse when the api client silently dropped items whose projection threw — those are
-        // items Jellyfin DID return, so treating them as deletions would hard-delete healthy rows.
-        if (!MediaServerReconciliationGuard.ShouldFlagMissing(
-                _logger,
-                library.Name,
-                incomingPaths.Count,
-                existingPaths.Count,
-                projectionFailures.Count))
-        {
-            return;
-        }
-
-        foreach (string path in existingPaths.Except(incomingPaths))
-        {
-            List<int> musicVideoIds = await _musicVideoRepository.DeleteByPath(libraryPath, path);
-            if (musicVideoIds.Count > 0 &&
-                !await _scannerProxy.RemoveMediaItems(musicVideoIds.ToArray(), cancellationToken))
-            {
-                _logger.LogWarning("Failed to remove media items from scanner process");
-            }
-        }
-
-        List<int> artistIds = await _artistRepository.DeleteEmptyArtists(libraryPath);
-        if (artistIds.Count > 0 &&
-            !await _scannerProxy.RemoveMediaItems(artistIds.ToArray(), cancellationToken))
-        {
-            _logger.LogWarning("Failed to remove empty artists from scanner process");
-        }
-    }
-
-    private async Task<Either<BaseError, MediaItemScanResult<MusicVideo>>> ProcessMusicVideo(
-        JellyfinLibrary library,
-        LibraryPath libraryPath,
-        List<JellyfinPathReplacement> pathReplacements,
-        MusicVideo incoming,
-        CancellationToken cancellationToken)
-    {
-        string localPath = GetLocalPath(pathReplacements, incoming);
-        string folder = Path.GetDirectoryName(localPath) ?? libraryPath.Path;
-        Option<int> maybeParentFolder = await _libraryRepository.GetParentFolderId(libraryPath, folder, cancellationToken);
-        LibraryFolder libraryFolder = await _libraryRepository.GetOrAddFolder(libraryPath, maybeParentFolder, folder);
-
-        return await GetOrAddArtist(libraryPath, incoming)
-            .BindT(artist => _musicVideoRepository.GetOrAdd(artist, libraryPath, libraryFolder, localPath))
-            .BindT(result => UpdateMusicVideo(result, incoming, localPath, cancellationToken));
-    }
-
-    private string GetLocalPath(List<JellyfinPathReplacement> pathReplacements, MusicVideo musicVideo) =>
                 _pathReplacementService.GetReplacementJellyfinPath(
                     pathReplacements,
                     musicVideo.GetHeadVersion().MediaFiles.Head().Path,
                     false);
 
-    private async Task<Either<BaseError, Artist>> GetOrAddArtist(LibraryPath libraryPath, MusicVideo musicVideo)
+            return await ScanLibrary(
-    {
+                _jellyfinMusicVideoRepository,
-        string artistName = musicVideo.MusicVideoMetadata
+                connectionParameters,
-            .HeadOrNone()
+                library,
-            .Bind(metadata => Optional(metadata.Artists).Flatten().HeadOrNone())
+                libraryPath,
-            .Map(artist => artist.Name)
+                GetLocalPath,
-            .IfNone(UnknownArtist);
+                deepScan,
-
+                cancellationToken);
-        var metadata = new ArtistMetadata
-        {
-            MetadataKind = MetadataKind.External,
-            Title = artistName,
-            SortTitle = SortTitle.GetSortTitle(artistName),
-            DateAdded = DateTime.UtcNow,
-            Genres = [],
-            Styles = [],
-            Moods = [],
-            Artwork = [],
-            Guids = [],
-            Subtitles = []
-        };
-
-        Option<Artist> maybeArtist = await _artistRepository.GetArtistByMetadata(libraryPath.Id, metadata);
-        foreach (Artist artist in maybeArtist)
-        {
-            return artist;
         }
 
-        Either<BaseError, MediaItemScanResult<Artist>> result =
+        return BaseError.New($"Jellyfin library {library.Id} has no library path");
-            await _artistRepository.AddArtist(libraryPath.Id, artistName, metadata);
-        return result.Map(scanResult => scanResult.Item);
     }
 
-    private async Task<Either<BaseError, MediaItemScanResult<MusicVideo>>> UpdateMusicVideo(
+    protected override string MediaServerItemId(JellyfinMusicVideo musicVideo) => musicVideo.ItemId;
-        MediaItemScanResult<MusicVideo> result,
+
-        MusicVideo incoming,
+    protected override string MediaServerEtag(JellyfinMusicVideo musicVideo) => musicVideo.Etag;
-        string localPath,
+
+    protected override IAsyncEnumerable<Tuple<JellyfinMusicVideo, int>> GetMusicVideoLibraryItems(
+        JellyfinConnectionParameters connectionParameters,
+        JellyfinLibrary library) =>
+        _jellyfinApiClient.GetMusicVideoLibraryItems(
+            connectionParameters.Address,
+            connectionParameters.AuthorizationHeader,
+            library);
+
+    protected override async Task<Either<BaseError, MediaItemScanResult<JellyfinMusicVideo>>> UpdateMetadata(
+        MediaItemScanResult<JellyfinMusicVideo> result,
+        JellyfinMusicVideo incoming,
         CancellationToken cancellationToken)
     {
-        result.LocalPath = localPath;
+        if (await UpdateMetadata(result.Item, incoming.MusicVideoMetadata.Head()))
-        MusicVideoMetadata incomingMetadata = incoming.MusicVideoMetadata.Head();
-
-        bool updated = await UpdateMetadata(result.Item, incomingMetadata);
-        updated = await _metadataRepository.UpdateStatistics(result.Item, incoming.GetHeadVersion()) || updated;
-
-        if (updated)
         {
             result.IsUpdated = true;
         }
@@ -289,7 +131,7 @@ public class JellyfinMusicVideoLibraryScanner : IJellyfinMusicVideoLibraryScanne
             bool updated = await _metadataRepository.Update(existing);
 
             // ersatztv#497: the scalar Update above marks only the metadata row Modified; it does NOT touch
-            // child collections, and MusicVideoRepository.GetOrAdd loads them AsNoTracking — so tag/genre/studio/
+            // child collections, and the repository's GetOrAdd loads them AsNoTracking — so tag/genre/studio/
             // artist edits made in Jellyfin never reached an EXISTING music video (only the Add path persisted
             // them). Reconcile the collections that BOTH the Add path persists AND GetOrAdd eager-loads:
             // Genres, Tags, Studios, Artists. (Guids are add-persisted but not eager-loaded here — reconciling

ErsatzTV.Scanner/Core/Metadata/MediaServerMusicVideoLibraryScanner.cs

@@ -0,0 +1,376 @@
+using System.Collections.Immutable;
+using System.IO.Abstractions;
+using ErsatzTV.Core;
+using ErsatzTV.Core.Domain;
+using ErsatzTV.Core.Domain.MediaServer;
+using ErsatzTV.Core.Errors;
+using ErsatzTV.Core.Extensions;
+using ErsatzTV.Core.Interfaces.Repositories;
+using ErsatzTV.Core.Metadata;
+using ErsatzTV.Scanner.Core.Interfaces;
+using Microsoft.Extensions.Logging;
+
+namespace ErsatzTV.Scanner.Core.Metadata;
+
+// ersatztv#496: music videos used to be reconciled by a LIBRARY-SCOPED local-path diff plus hard delete, because
+// they carried no server identity. They now carry one (JellyfinMusicVideo.ItemId/Etag), so this scanner is the
+// music-video sibling of MediaServer{Movie,Television,OtherVideo}LibraryScanner: it diffs on the server item id
+// and soft-trashes (FileNotFound) instead of deleting, which is reversible and EmptyTrash-governed.
+public abstract class MediaServerMusicVideoLibraryScanner<TConnectionParameters, TLibrary, TMusicVideo, TEtag>
+    where TConnectionParameters : MediaServerConnectionParameters
+    where TLibrary : Library
+    where TMusicVideo : MusicVideo
+    where TEtag : MediaServerItemEtag
+{
+    private const string UnknownArtist = "Unknown Artist";
+
+    private readonly IArtistRepository _artistRepository;
+    private readonly IFileSystem _fileSystem;
+    private readonly ILibraryRepository _libraryRepository;
+    private readonly ILogger _logger;
+    private readonly IMetadataRepository _metadataRepository;
+    private readonly IScannerProxy _scannerProxy;
+
+    protected MediaServerMusicVideoLibraryScanner(
+        IScannerProxy scannerProxy,
+        IFileSystem fileSystem,
+        IArtistRepository artistRepository,
+        ILibraryRepository libraryRepository,
+        IMetadataRepository metadataRepository,
+        ILogger logger)
+    {
+        _scannerProxy = scannerProxy;
+        _fileSystem = fileSystem;
+        _artistRepository = artistRepository;
+        _libraryRepository = libraryRepository;
+        _metadataRepository = metadataRepository;
+        _logger = logger;
+    }
+
+    protected async Task<Either<BaseError, Unit>> ScanLibrary(
+        IMediaServerMusicVideoRepository<TLibrary, TMusicVideo, TEtag> musicVideoRepository,
+        TConnectionParameters connectionParameters,
+        TLibrary library,
+        LibraryPath libraryPath,
+        Func<TMusicVideo, string> getLocalPath,
+        bool deepScan,
+        CancellationToken cancellationToken)
+    {
+        try
+        {
+            return await ScanLibrary(
+                musicVideoRepository,
+                connectionParameters,
+                library,
+                libraryPath,
+                getLocalPath,
+                GetMusicVideoLibraryItems(connectionParameters, library),
+                deepScan,
+                cancellationToken);
+        }
+        catch (Exception ex) when (ex is TaskCanceledException or OperationCanceledException)
+        {
+            return new ScanCanceled();
+        }
+    }
+
+    private async Task<Either<BaseError, Unit>> ScanLibrary(
+        IMediaServerMusicVideoRepository<TLibrary, TMusicVideo, TEtag> musicVideoRepository,
+        TConnectionParameters connectionParameters,
+        TLibrary library,
+        LibraryPath libraryPath,
+        Func<TMusicVideo, string> getLocalPath,
+        IAsyncEnumerable<Tuple<TMusicVideo, int>> musicVideoEntries,
+        bool deepScan,
+        CancellationToken cancellationToken)
+    {
+        var incomingItemIds = new List<string>();
+        var existingMusicVideos = (await musicVideoRepository.GetExistingMusicVideos(library))
+            .ToImmutableDictionary(e => e.MediaServerItemId, e => e);
+
+        await foreach ((TMusicVideo incoming, int totalMusicVideoCount) in musicVideoEntries.WithCancellation(
+                           cancellationToken))
+        {
+            if (cancellationToken.IsCancellationRequested)
+            {
+                return new ScanCanceled();
+            }
+
+            incomingItemIds.Add(MediaServerItemId(incoming));
+
+            decimal percentCompletion = totalMusicVideoCount == 0
+                ? 1
+                : Math.Clamp((decimal)incomingItemIds.Count / totalMusicVideoCount, 0, 1);
+            if (!await _scannerProxy.UpdateProgress(percentCompletion, cancellationToken))
+            {
+                return new ScanCanceled();
+            }
+
+            string localPath = getLocalPath(incoming);
+
+            if (!await ShouldScanItem(
+                    musicVideoRepository,
+                    library,
+                    existingMusicVideos,
+                    incoming,
+                    localPath,
+                    deepScan))
+            {
+                continue;
+            }
+
+            Either<BaseError, MediaItemScanResult<TMusicVideo>> maybeMusicVideo =
+                await ProcessMusicVideo(
+                    musicVideoRepository,
+                    library,
+                    libraryPath,
+                    incoming,
+                    localPath,
+                    deepScan,
+                    cancellationToken);
+
+            if (maybeMusicVideo.IsLeft)
+            {
+                foreach (BaseError error in maybeMusicVideo.LeftToSeq())
+                {
+                    _logger.LogWarning("Error processing music video: {Error}", error.Value);
+                }
+
+                continue;
+            }
+
+            foreach (MediaItemScanResult<TMusicVideo> result in maybeMusicVideo.RightToSeq())
+            {
+                await musicVideoRepository.SetEtag(result.Item, MediaServerEtag(incoming));
+
+                if (_fileSystem.File.Exists(result.LocalPath))
+                {
+                    Option<int> flagResult = await musicVideoRepository.FlagNormal(library, result.Item);
+                    if (flagResult.IsSome)
+                    {
+                        result.IsUpdated = true;
+                    }
+                }
+                else
+                {
+                    Option<int> flagResult = await musicVideoRepository.FlagUnavailable(library, result.Item);
+                    if (flagResult.IsSome)
+                    {
+                        result.IsUpdated = true;
+                    }
+                }
+
+                if (result.IsAdded || result.IsUpdated)
+                {
+                    if (!await _scannerProxy.ReindexMediaItems([result.Item.Id], cancellationToken))
+                    {
+                        _logger.LogWarning("Failed to reindex media items from scanner process");
+                    }
+                }
+            }
+        }
+
+        await TrashMissingMusicVideos(
+            musicVideoRepository,
+            library,
+            libraryPath,
+            incomingItemIds,
+            existingMusicVideos,
+            cancellationToken);
+
+        return Unit.Default;
+    }
+
+    // Soft-trash music videos the media server no longer reports. Identity is the SERVER ITEM ID, scoped to this
+    // library by GetExistingMusicVideos/FlagFileNotFound (both join LibraryPath.LibraryId), so a file served by two
+    // libraries with overlapping local paths is two independent identities and one library's sweep can no longer
+    // reach the other's row — the ersatztv#496 cross-library false-trash this replaced.
+    private async Task TrashMissingMusicVideos(
+        IMediaServerMusicVideoRepository<TLibrary, TMusicVideo, TEtag> musicVideoRepository,
+        TLibrary library,
+        LibraryPath libraryPath,
+        List<string> incomingItemIds,
+        ImmutableDictionary<string, TEtag> existingMusicVideos,
+        CancellationToken cancellationToken)
+    {
+        // ersatztv#477: refuse the sweep when a successful fetch returned zero items but rows exist locally — an
+        // empty incoming set is indistinguishable from a transient error and would otherwise flag a whole library.
+        if (!MediaServerReconciliationGuard.ShouldFlagMissing(
+                _logger,
+                library.Name,
+                incomingItemIds.Count,
+                existingMusicVideos.Count))
+        {
+            return;
+        }
+
+        var fileNotFoundItemIds = existingMusicVideos.Keys.Except(incomingItemIds).ToList();
+        List<int> ids = await musicVideoRepository.FlagFileNotFound(library, fileNotFoundItemIds);
+        if (ids.Count > 0 && !await _scannerProxy.ReindexMediaItems(ids.ToArray(), cancellationToken))
+        {
+            _logger.LogWarning("Failed to reindex media items from scanner process");
+        }
+
+        // Trashed music videos are still rows, so an artist only becomes empty once the trash is emptied (or its
+        // items are removed some other way); this keeps ersatztv#494's empty-artist cleanup without the delete.
+        List<int> artistIds = await _artistRepository.DeleteEmptyArtists(libraryPath);
+        if (artistIds.Count > 0 && !await _scannerProxy.RemoveMediaItems(artistIds.ToArray(), cancellationToken))
+        {
+            _logger.LogWarning("Failed to remove empty artists from scanner process");
+        }
+    }
+
+    private async Task<Either<BaseError, MediaItemScanResult<TMusicVideo>>> ProcessMusicVideo(
+        IMediaServerMusicVideoRepository<TLibrary, TMusicVideo, TEtag> musicVideoRepository,
+        TLibrary library,
+        LibraryPath libraryPath,
+        TMusicVideo incoming,
+        string localPath,
+        bool deepScan,
+        CancellationToken cancellationToken)
+    {
+        // ersatztv#488: resolve the owning folder from the DB, never from libraryPath.LibraryFolders (that
+        // navigation is only eager-loaded on the local scan path and is null for media-server callers).
+        string folder = Path.GetDirectoryName(localPath) ?? libraryPath.Path;
+        Option<int> maybeParentFolder =
+            await _libraryRepository.GetParentFolderId(libraryPath, folder, cancellationToken);
+        LibraryFolder libraryFolder = await _libraryRepository.GetOrAddFolder(libraryPath, maybeParentFolder, folder);
+
+        return await GetOrAddArtist(libraryPath, incoming)
+            .BindT(artist => musicVideoRepository.GetOrAdd(
+                library,
+                artist,
+                libraryFolder,
+                incoming,
+                deepScan,
+                cancellationToken))
+            .MapT(result =>
+            {
+                result.LocalPath = localPath;
+                return result;
+            })
+            .BindT(result => UpdateMetadata(result, incoming, cancellationToken))
+            .BindT(result => UpdateStatistics(result, incoming));
+    }
+
+    private async Task<Either<BaseError, Artist>> GetOrAddArtist(LibraryPath libraryPath, TMusicVideo musicVideo)
+    {
+        string artistName = musicVideo.MusicVideoMetadata
+            .HeadOrNone()
+            .Bind(metadata => Optional(metadata.Artists).Flatten().HeadOrNone())
+            .Map(artist => artist.Name)
+            .IfNone(UnknownArtist);
+
+        var metadata = new ArtistMetadata
+        {
+            MetadataKind = MetadataKind.External,
+            Title = artistName,
+            SortTitle = SortTitle.GetSortTitle(artistName),
+            DateAdded = DateTime.UtcNow,
+            Genres = [],
+            Styles = [],
+            Moods = [],
+            Artwork = [],
+            Guids = [],
+            Subtitles = []
+        };
+
+        Option<Artist> maybeArtist = await _artistRepository.GetArtistByMetadata(libraryPath.Id, metadata);
+        foreach (Artist artist in maybeArtist)
+        {
+            return artist;
+        }
+
+        Either<BaseError, MediaItemScanResult<Artist>> result =
+            await _artistRepository.AddArtist(libraryPath.Id, artistName, metadata);
+        return result.Map(scanResult => scanResult.Item);
+    }
+
+    private async Task<Either<BaseError, MediaItemScanResult<TMusicVideo>>> UpdateStatistics(
+        MediaItemScanResult<TMusicVideo> result,
+        TMusicVideo incoming)
+    {
+        if (await _metadataRepository.UpdateStatistics(result.Item, incoming.GetHeadVersion()))
+        {
+            result.IsUpdated = true;
+        }
+
+        return result;
+    }
+
+    private async Task<bool> ShouldScanItem(
+        IMediaServerMusicVideoRepository<TLibrary, TMusicVideo, TEtag> musicVideoRepository,
+        TLibrary library,
+        ImmutableDictionary<string, TEtag> existingMusicVideos,
+        TMusicVideo incoming,
+        string localPath,
+        bool deepScan)
+    {
+        // deep scan will always pull every music video
+        if (deepScan)
+        {
+            return true;
+        }
+
+        string existingEtag = string.Empty;
+        MediaItemState existingState = MediaItemState.Normal;
+        if (existingMusicVideos.TryGetValue(MediaServerItemId(incoming), out TEtag? existingEntry))
+        {
+            existingEtag = existingEntry.Etag;
+            existingState = existingEntry.State;
+        }
+
+        if (existingState is MediaItemState.Unavailable or MediaItemState.FileNotFound &&
+            existingEtag == MediaServerEtag(incoming))
+        {
+            // skip scanning unavailable/file not found items that are unchanged and still don't exist locally
+            if (!_fileSystem.File.Exists(localPath))
+            {
+                return false;
+            }
+        }
+        else if (existingEtag == MediaServerEtag(incoming))
+        {
+            // item is unchanged, but file does not exist
+            // don't scan, but mark as unavailable
+            if (!_fileSystem.File.Exists(localPath))
+            {
+                if (existingState is not MediaItemState.Unavailable)
+                {
+                    foreach (int id in await musicVideoRepository.FlagUnavailable(library, incoming))
+                    {
+                        if (!await _scannerProxy.ReindexMediaItems([id], CancellationToken.None))
+                        {
+                            _logger.LogWarning("Failed to reindex media items from scanner process");
+                        }
+                    }
+                }
+            }
+
+            return false;
+        }
+
+        if (existingEntry is null)
+        {
+            _logger.LogDebug("INSERT: new music video {Path}", localPath);
+        }
+        else
+        {
+            _logger.LogDebug("UPDATE: Etag has changed for music video {Path}", localPath);
+        }
+
+        return true;
+    }
+
+    protected abstract string MediaServerItemId(TMusicVideo musicVideo);
+    protected abstract string MediaServerEtag(TMusicVideo musicVideo);
+
+    protected abstract IAsyncEnumerable<Tuple<TMusicVideo, int>> GetMusicVideoLibraryItems(
+        TConnectionParameters connectionParameters,
+        TLibrary library);
+
+    protected abstract Task<Either<BaseError, MediaItemScanResult<TMusicVideo>>> UpdateMetadata(
+        MediaItemScanResult<TMusicVideo> result,
+        TMusicVideo incoming,
+        CancellationToken cancellationToken);
+}

ErsatzTV.Scanner/Program.cs

@@ -241,6 +241,7 @@ public class Program
                 services.AddScoped<IJellyfinApiClient, JellyfinApiClient>();
                 services.AddScoped<IJellyfinCollectionRepository, JellyfinCollectionRepository>();
                 services.AddScoped<IJellyfinMovieRepository, JellyfinMovieRepository>();
+                services.AddScoped<IJellyfinMusicVideoRepository, JellyfinMusicVideoRepository>();
                 services.AddScoped<IJellyfinTelevisionRepository, JellyfinTelevisionRepository>();
                 services.AddScoped<IJellyfinPathReplacementService, JellyfinPathReplacementService>();
 

ErsatzTV.Tests/Integration/JellyfinMusicVideoLibraryScannerTests.cs

@@ -24,9 +24,13 @@ namespace ErsatzTV.Tests.Integration;
 // End-to-end regression for ersatztv#488. Unlike the existing MediaServer*LibraryScanner tests (which
 // substitute every repository, and therefore could never have exhibited the null-navigation bug — see the
 // mocked GetOrAddFolder in MovieFolderScannerTests), this test wires the REAL LibraryRepository /
-// ArtistRepository / MusicVideoRepository against in-memory SQLite so the actual crash path runs. The
+// ArtistRepository / JellyfinMusicVideoRepository against in-memory SQLite so the actual crash path runs. The
 // deviation from the mock-and-verify house style is deliberate and required: a substituted
 // ILibraryRepository cannot exhibit the defect this issue is about.
+//
+// ersatztv#496 reshaped this suite: music videos now carry a per-library server identity
+// (JellyfinMusicVideo.ItemId/Etag), so reconciliation diffs on the item id and SOFT-trashes (FileNotFound)
+// instead of hard-deleting by path. The #494 "row disappears" assertions became "row is flagged" assertions.
 [TestFixture]
 public class JellyfinMusicVideoLibraryScannerTests
 {
@@ -44,55 +48,18 @@ public class JellyfinMusicVideoLibraryScannerTests
         int libraryPathId = await SeedLibraryPath("/data/music");
 
         // the remote-path shape that used to crash: Paths is populated, LibraryFolders is null
-        var libraryPath = new LibraryPath { Id = libraryPathId, Path = "/data/music", LibraryFolders = null };
+        JellyfinLibrary library = BuildLibrary(libraryPathId, "/data/music");
-        var library = new JellyfinLibrary
-        {
-            Id = 42,
-            MediaSourceId = 1,
-            ItemId = "lib15",
-            ShouldSyncItems = true,
-            Paths = new List<LibraryPath> { libraryPath }
-        };
 
         const string VideoPath = "/data/music/artist1/song1.mkv";
-        MusicVideo incoming = BuildIncoming(VideoPath, artistName: "Artist 1", title: "Song 1");
 
-        var apiClient = Substitute.For<IJellyfinApiClient>();
+        (JellyfinMusicVideoLibraryScanner scanner, _) = BuildScanner(FakeApi(
-        apiClient.GetMusicVideoLibraryItems(
+            () => BuildIncoming(VideoPath, "Artist 1", "Song 1")));
-            Arg.Any<string>(),
-            Arg.Any<string>(),
-            Arg.Any<JellyfinLibrary>(),
-            Arg.Any<MediaServerProjectionFailureCounter>())
-            .Returns(OneItem(incoming));
 
-        var pathReplacement = Substitute.For<IJellyfinPathReplacementService>();
+        Either<BaseError, Unit> result = await scanner.ScanLibrary(
-        pathReplacement
+            ConnectionParameters,
-            .GetReplacementJellyfinPath(Arg.Any<List<JellyfinPathReplacement>>(), Arg.Any<string>(), Arg.Any<bool>())
+            library,
-            .Returns(ci => ci.ArgAt<string>(1));
+            deepScan: false,
-
+            CancellationToken.None);
-        var mediaSourceRepository = Substitute.For<IMediaSourceRepository>();
-        mediaSourceRepository.GetJellyfinPathReplacements(Arg.Any<int>())
-            .Returns(Task.FromResult(new List<JellyfinPathReplacement>()));
-
-        var scannerProxy = Substitute.For<IScannerProxy>();
-        scannerProxy.UpdateProgress(Arg.Any<decimal>(), Arg.Any<CancellationToken>()).Returns(true);
-        scannerProxy.ReindexMediaItems(Arg.Any<int[]>(), Arg.Any<CancellationToken>()).Returns(true);
-
-        var scanner = new JellyfinMusicVideoLibraryScanner(
-            scannerProxy,
-            apiClient,
-            pathReplacement,
-            mediaSourceRepository,
-            new ArtistRepository(_db.Factory),
-            new MusicVideoRepository(_db.Factory),
-            new LibraryRepository(Substitute.For<IFileSystem>(), _db.Factory),
-            Substitute.For<IMetadataRepository>(),
-            NullLogger<JellyfinMusicVideoLibraryScanner>.Instance);
-
-        var connectionParameters = new JellyfinConnectionParameters("http://jellyfin", "api-key", 1);
-
-        Either<BaseError, Unit> result =
-            await scanner.ScanLibrary(connectionParameters, library, deepScan: false, CancellationToken.None);
 
         // the scan runs to completion instead of crashing on GetOrAddFolder
         result.IsRight.ShouldBeTrue(result.Match(Right: _ => "", Left: e => e.Value));
@@ -122,21 +89,27 @@ public class JellyfinMusicVideoLibraryScannerTests
         LibraryFolder folder = await context.LibraryFolders.SingleAsync(f => f.Id == file.LibraryFolderId);
         folder.Path.ShouldBe("/data/music/artist1");
         folder.LibraryPathId.ShouldBe(libraryPathId);
+
+        // ersatztv#496: the row carries the server item id, so it is no longer identified by its path
+        List<JellyfinMusicVideo> identities = await context.JellyfinMusicVideos.ToListAsync();
+        identities.Count.ShouldBe(1);
+        identities[0].ItemId.ShouldBe(ItemIdFor(VideoPath));
     }
 
-    // ersatztv#494: a music video removed from Jellyfin must be removed from ErsatzTV on the next scan.
+    // ersatztv#494 as reshaped by ersatztv#496: a music video removed from Jellyfin is SOFT-trashed
+    // (State = FileNotFound), not hard-deleted, matching the movie/TV/other-video scanners. The row survives, so
+    // collection membership and playout references survive with it and EmptyTrash governs the real removal.
     [Test]
-    public async Task ScanLibrary_Should_Remove_MusicVideo_Missing_From_Jellyfin()
+    public async Task ScanLibrary_Should_Flag_FileNotFound_For_MusicVideo_Missing_From_Jellyfin()
     {
         int id = await SeedLibraryPath("/data/music");
         JellyfinLibrary library = BuildLibrary(id, "/data/music");
-        var connectionParameters = new JellyfinConnectionParameters("http://jellyfin", "api-key", 1);
 
         // first scan seeds two music videos
         (JellyfinMusicVideoLibraryScanner seed, _) = BuildScanner(FakeApi(
             () => BuildIncoming("/data/music/artist1/keep.mkv", "Artist 1", "Keep"),
             () => BuildIncoming("/data/music/artist2/gone.mkv", "Artist 2", "Gone")));
-        (await seed.ScanLibrary(connectionParameters, library, deepScan: false, CancellationToken.None))
+        (await seed.ScanLibrary(ConnectionParameters, library, deepScan: false, CancellationToken.None))
             .IsRight.ShouldBeTrue();
         (await MusicVideoPaths(id)).Count.ShouldBe(2);
         int goneId = await MusicVideoId("/data/music/artist2/gone.mkv");
@@ -144,44 +117,155 @@ public class JellyfinMusicVideoLibraryScannerTests
         // second scan: only "keep" is still present upstream
         (JellyfinMusicVideoLibraryScanner scanner, IScannerProxy scannerProxy) = BuildScanner(FakeApi(
             () => BuildIncoming("/data/music/artist1/keep.mkv", "Artist 1", "Keep")));
-        (await scanner.ScanLibrary(connectionParameters, library, deepScan: false, CancellationToken.None))
+        (await scanner.ScanLibrary(ConnectionParameters, library, deepScan: false, CancellationToken.None))
             .IsRight.ShouldBeTrue();
 
-        List<string> paths = await MusicVideoPaths(id);
+        // both rows still exist — the missing one is flagged, not deleted
-        paths.ShouldBe(new[] { "/data/music/artist1/keep.mkv" });
+        (await MusicVideoPaths(id)).Count.ShouldBe(2);
-        await scannerProxy.Received().RemoveMediaItems(
+        (await MediaItemStateOf(goneId)).ShouldBe(MediaItemState.FileNotFound);
+        (await MediaItemStateOf(await MusicVideoId("/data/music/artist1/keep.mkv")))
+            .ShouldBe(MediaItemState.Normal);
+
+        await scannerProxy.Received().ReindexMediaItems(
+            Arg.Is<int[]>(ids => ids.Contains(goneId)),
+            Arg.Any<CancellationToken>());
+        await scannerProxy.DidNotReceive().RemoveMediaItems(
             Arg.Is<int[]>(ids => ids.Contains(goneId)),
             Arg.Any<CancellationToken>());
     }
 
-    // ersatztv#494: an artist left with zero music videos is cleaned up.
+    // ersatztv#496: the artist of a soft-trashed music video is NOT emptied, because the music video row is still
+    // there. This is the deliberate consequence of replacing #494's hard delete — artist cleanup now happens only
+    // once the trash is actually emptied.
     [Test]
-    public async Task ScanLibrary_Should_Cleanup_Empty_Artist()
+    public async Task ScanLibrary_Should_Keep_Artist_Of_Trashed_MusicVideo()
     {
         int id = await SeedLibraryPath("/data/music");
         JellyfinLibrary library = BuildLibrary(id, "/data/music");
-        var connectionParameters = new JellyfinConnectionParameters("http://jellyfin", "api-key", 1);
 
         (JellyfinMusicVideoLibraryScanner seed, _) = BuildScanner(FakeApi(
             () => BuildIncoming("/data/music/artist1/keep.mkv", "Artist 1", "Keep"),
             () => BuildIncoming("/data/music/artist2/gone.mkv", "Artist 2", "Gone")));
-        (await seed.ScanLibrary(connectionParameters, library, deepScan: false, CancellationToken.None))
+        (await seed.ScanLibrary(ConnectionParameters, library, deepScan: false, CancellationToken.None))
             .IsRight.ShouldBeTrue();
         (await ArtistTitles(id)).Count.ShouldBe(2);
 
-        // "Artist 2" loses its only music video
+        // "Artist 2" loses its only music video from the server's point of view
         (JellyfinMusicVideoLibraryScanner scanner, _) = BuildScanner(FakeApi(
             () => BuildIncoming("/data/music/artist1/keep.mkv", "Artist 1", "Keep")));
-        (await scanner.ScanLibrary(connectionParameters, library, deepScan: false, CancellationToken.None))
+        (await scanner.ScanLibrary(ConnectionParameters, library, deepScan: false, CancellationToken.None))
             .IsRight.ShouldBeTrue();
 
-        (await ArtistTitles(id)).ShouldBe(new[] { "Artist 1" });
+        (await ArtistTitles(id)).ShouldBe(new[] { "Artist 1", "Artist 2" });
     }
 
-    // ersatztv#494 (Done-when 3): the music-video sweep must never delete a Movie or Show that shares the
+    // ersatztv#496 (the issue's Done-when 2): one library's sweep must never reach another library's music
-    // same LibraryPath — the cross-delete risk is a LibraryPathId property, not a Mixed-library property.
+    // videos. Identity is now (server item id, owning library), so library B reporting nothing cannot flag a row
+    // owned by library A — even though both libraries point at the SAME local path.
+    //
+    // Under the pre-#496 path diff this was the live hazard: the sweep resolved rows by (LibraryPathId, path) and
+    // HARD-deleted them, so the row a second library still served was destroyed outright.
     [Test]
-    public async Task ScanLibrary_Should_Not_CrossDelete_Movie_Or_Show_Sharing_The_LibraryPath()
+    public async Task ScanLibrary_Should_Not_Flag_MusicVideos_Owned_By_Another_Library()
+    {
+        int pathA = await SeedLibraryPath("/data/music", libraryId: 42);
+        int pathB = await SeedLibraryPath("/data/music-overlap", libraryId: 43);
+
+        JellyfinLibrary libraryA = BuildLibrary(pathA, "/data/music", libraryId: 42);
+        JellyfinLibrary libraryB = BuildLibrary(pathB, "/data/music-overlap", libraryId: 43);
+
+        // library A owns the row
+        (JellyfinMusicVideoLibraryScanner seedA, _) = BuildScanner(FakeApi(
+            () => BuildIncoming("/data/music/artist1/song.mkv", "Artist 1", "Song")));
+        (await seedA.ScanLibrary(ConnectionParameters, libraryA, deepScan: false, CancellationToken.None))
+            .IsRight.ShouldBeTrue();
+        int ownedId = await MusicVideoId("/data/music/artist1/song.mkv");
+
+        // library B has its own, different item and reports only that one
+        (JellyfinMusicVideoLibraryScanner seedB, _) = BuildScanner(FakeApi(
+            () => BuildIncoming("/data/music-overlap/artist9/other.mkv", "Artist 9", "Other")));
+        (await seedB.ScanLibrary(ConnectionParameters, libraryB, deepScan: false, CancellationToken.None))
+            .IsRight.ShouldBeTrue();
+
+        // library B now reports nothing but its own item disappearing — A's row must be untouched
+        (JellyfinMusicVideoLibraryScanner scannerB, _) = BuildScanner(FakeApi(
+            () => BuildIncoming("/data/music-overlap/artist9/other2.mkv", "Artist 9", "Other 2")));
+        (await scannerB.ScanLibrary(ConnectionParameters, libraryB, deepScan: false, CancellationToken.None))
+            .IsRight.ShouldBeTrue();
+
+        (await MediaItemStateOf(ownedId)).ShouldBe(MediaItemState.Normal);
+        (await MediaItemStateOf(await MusicVideoId("/data/music-overlap/artist9/other.mkv")))
+            .ShouldBe(MediaItemState.FileNotFound);
+    }
+
+    // ersatztv#496: rows that predate per-item identity (created by the path-keyed scanner, or by the local
+    // MusicVideoFolderScanner) must be ADOPTED in place — the same MediaItem id gains a JellyfinMusicVideo
+    // identity row. A delete-and-re-add would silently drop collection membership, which is exactly what a
+    // populated music collection depends on.
+    [Test]
+    public async Task ScanLibrary_Should_Adopt_PreExisting_MusicVideo_Preserving_Identity_And_Collections()
+    {
+        int libraryPathId = await SeedLibraryPath("/data/music");
+        const string VideoPath = "/data/music/artist1/song1.mkv";
+
+        int existingId = await SeedPlainMusicVideo(libraryPathId, VideoPath, "Artist 1");
+        int collectionId = await SeedCollectionWith(existingId);
+
+        JellyfinLibrary library = BuildLibrary(libraryPathId, "/data/music");
+        (JellyfinMusicVideoLibraryScanner scanner, _) = BuildScanner(FakeApi(
+            () => BuildIncoming(VideoPath, "Artist 1", "Song 1")));
+        (await scanner.ScanLibrary(ConnectionParameters, library, deepScan: false, CancellationToken.None))
+            .IsRight.ShouldBeTrue();
+
+        await using TvContext context = _db.CreateContext();
+
+        // no duplicate row was created
+        (await context.MusicVideos.CountAsync(mv => mv.LibraryPathId == libraryPathId)).ShouldBe(1);
+
+        // the SAME row now carries the server identity
+        List<JellyfinMusicVideo> identities = await context.JellyfinMusicVideos.ToListAsync();
+        identities.Count.ShouldBe(1);
+        identities[0].Id.ShouldBe(existingId);
+        identities[0].ItemId.ShouldBe(ItemIdFor(VideoPath));
+
+        // and collection membership survived the adoption
+        List<CollectionItem> items = await context.CollectionItems
+            .Where(ci => ci.CollectionId == collectionId)
+            .ToListAsync();
+        items.Count.ShouldBe(1);
+        items[0].MediaItemId.ShouldBe(existingId);
+    }
+
+    // ersatztv#496: adoption is scoped to the scanned library's own library path, so a music video owned by a
+    // LOCAL library (MusicVideoFolderScanner writes the same MusicVideo table) is never hijacked into a Jellyfin
+    // library's identity.
+    [Test]
+    public async Task ScanLibrary_Should_Not_Adopt_A_MusicVideo_Owned_By_Another_LibraryPath()
+    {
+        int localPathId = await SeedLibraryPath("/data/local-music", libraryId: 99);
+        int jellyfinPathId = await SeedLibraryPath("/data/music", libraryId: 42);
+        const string VideoPath = "/data/shared/song1.mkv";
+
+        int localId = await SeedPlainMusicVideo(localPathId, VideoPath, "Artist 1");
+
+        JellyfinLibrary library = BuildLibrary(jellyfinPathId, "/data/music");
+        (JellyfinMusicVideoLibraryScanner scanner, _) = BuildScanner(FakeApi(
+            () => BuildIncoming(VideoPath, "Artist 1", "Song 1")));
+        (await scanner.ScanLibrary(ConnectionParameters, library, deepScan: false, CancellationToken.None))
+            .IsRight.ShouldBeTrue();
+
+        await using TvContext context = _db.CreateContext();
+
+        // the local row was left alone: no identity row, still owned by the local library path
+        (await context.JellyfinMusicVideos.CountAsync()).ShouldBe(0);
+        MusicVideo local = await context.MusicVideos.SingleAsync(mv => mv.Id == localId);
+        local.LibraryPathId.ShouldBe(localPathId);
+    }
+
+    // ersatztv#494 (Done-when 3): the music-video sweep must never touch a Movie or Show that shares the
+    // same LibraryPath — the cross-flag risk is a LibraryPathId property, not a Mixed-library property.
+    [Test]
+    public async Task ScanLibrary_Should_Not_CrossFlag_Movie_Or_Show_Sharing_The_LibraryPath()
     {
         int id = await SeedLibraryPath("/data/mixed");
 
@@ -193,54 +277,54 @@ public class JellyfinMusicVideoLibraryScannerTests
         }
 
         JellyfinLibrary library = BuildLibrary(id, "/data/mixed");
-        var connectionParameters = new JellyfinConnectionParameters("http://jellyfin", "api-key", 1);
 
         // seed one music video under the same LibraryPath
         (JellyfinMusicVideoLibraryScanner seed, _) = BuildScanner(FakeApi(
             () => BuildIncoming("/data/mixed/song.mkv", "Artist 1", "Song")));
-        (await seed.ScanLibrary(connectionParameters, library, deepScan: false, CancellationToken.None))
+        (await seed.ScanLibrary(ConnectionParameters, library, deepScan: false, CancellationToken.None))
             .IsRight.ShouldBeTrue();
 
-        // next scan drops "song.mkv" and adds "song2.mkv" — the sweep removes song.mkv
+        // next scan drops "song.mkv" and adds "song2.mkv" — the sweep flags song.mkv only
         (JellyfinMusicVideoLibraryScanner scanner, _) = BuildScanner(FakeApi(
             () => BuildIncoming("/data/mixed/song2.mkv", "Artist 1", "Song 2")));
-        (await scanner.ScanLibrary(connectionParameters, library, deepScan: false, CancellationToken.None))
+        (await scanner.ScanLibrary(ConnectionParameters, library, deepScan: false, CancellationToken.None))
             .IsRight.ShouldBeTrue();
 
         await using TvContext context = _db.CreateContext();
         (await context.Movies.CountAsync(m => m.LibraryPathId == id)).ShouldBe(1);
         (await context.Shows.CountAsync(s => s.LibraryPathId == id)).ShouldBe(1);
-        (await MusicVideoPaths(id)).ShouldBe(new[] { "/data/mixed/song2.mkv" });
+        (await context.MediaItems.CountAsync(mi => mi.LibraryPathId == id && mi.State != MediaItemState.Normal))
+            .ShouldBe(1);
+        (await MediaItemStateOf(await MusicVideoId("/data/mixed/song.mkv")))
+            .ShouldBe(MediaItemState.FileNotFound);
     }
 
-    // ersatztv#477 guard: a successful-but-empty fetch must NOT wipe the library. Negative control — if the
+    // ersatztv#477 guard: a successful-but-empty fetch must NOT flag the library. Negative control — if the
-    // sweep were ungated, an empty incoming set would remove every existing music video.
+    // sweep were ungated, an empty incoming set would flag every existing music video.
     [Test]
     public async Task ScanLibrary_Should_Not_Sweep_When_Jellyfin_Returns_Zero_Items()
     {
         int id = await SeedLibraryPath("/data/music");
         JellyfinLibrary library = BuildLibrary(id, "/data/music");
-        var connectionParameters = new JellyfinConnectionParameters("http://jellyfin", "api-key", 1);
 
         (JellyfinMusicVideoLibraryScanner seed, _) = BuildScanner(FakeApi(
             () => BuildIncoming("/data/music/artist1/keep.mkv", "Artist 1", "Keep")));
-        (await seed.ScanLibrary(connectionParameters, library, deepScan: false, CancellationToken.None))
+        (await seed.ScanLibrary(ConnectionParameters, library, deepScan: false, CancellationToken.None))
             .IsRight.ShouldBeTrue();
+        int keepId = await MusicVideoId("/data/music/artist1/keep.mkv");
 
         // Jellyfin returns zero items (mid-restore / transient) — the sweep must be skipped
-        (JellyfinMusicVideoLibraryScanner scanner, IScannerProxy scannerProxy) = BuildScanner(FakeApi());
+        (JellyfinMusicVideoLibraryScanner scanner, _) = BuildScanner(FakeApi());
-        (await scanner.ScanLibrary(connectionParameters, library, deepScan: false, CancellationToken.None))
+        (await scanner.ScanLibrary(ConnectionParameters, library, deepScan: false, CancellationToken.None))
             .IsRight.ShouldBeTrue();
 
         (await MusicVideoPaths(id)).ShouldBe(new[] { "/data/music/artist1/keep.mkv" });
-        await scannerProxy.DidNotReceive().RemoveMediaItems(Arg.Any<int[]>(), Arg.Any<CancellationToken>());
+        (await MediaItemStateOf(keepId)).ShouldBe(MediaItemState.Normal);
     }
 
     // #493 session field data: a MIXED Jellyfin library runs the music-video arm with a legitimately EMPTY
     // incoming set on every scan while Movies/Shows exist under the same LibraryPath (the real "Standup" case).
-    // If existing were computed by LibraryPathId alone, existing.Except([]) would wipe the movies/episodes; the
+    // Identity is now per-item and per-library, so a movie can never enter the music-video diff at all.
-    // MusicVideo-joined FindMusicVideoPaths (not just the empty-fetch guard) is what protects them. Seed a Movie
-    // that even carries a MediaFile path, to prove the sweep never touches a non-music-video row.
     [Test]
     public async Task ScanLibrary_Should_Not_Touch_Movies_Or_Shows_When_No_MusicVideos_Present()
     {
@@ -269,16 +353,17 @@ public class JellyfinMusicVideoLibraryScannerTests
         }
 
         JellyfinLibrary library = BuildLibrary(id, "/data/standup");
-        var connectionParameters = new JellyfinConnectionParameters("http://jellyfin", "api-key", 1);
 
         // the music-video arm returns zero incoming — steady state for a mixed library
         (JellyfinMusicVideoLibraryScanner scanner, IScannerProxy scannerProxy) = BuildScanner(FakeApi());
-        (await scanner.ScanLibrary(connectionParameters, library, deepScan: false, CancellationToken.None))
+        (await scanner.ScanLibrary(ConnectionParameters, library, deepScan: false, CancellationToken.None))
             .IsRight.ShouldBeTrue();
 
         await using TvContext context = _db.CreateContext();
         (await context.Movies.CountAsync(m => m.LibraryPathId == id)).ShouldBe(1);
         (await context.Shows.CountAsync(s => s.LibraryPathId == id)).ShouldBe(1);
+        (await context.MediaItems.CountAsync(mi => mi.LibraryPathId == id && mi.State != MediaItemState.Normal))
+            .ShouldBe(0);
         await scannerProxy.DidNotReceive().RemoveMediaItems(Arg.Any<int[]>(), Arg.Any<CancellationToken>());
     }
 
@@ -286,24 +371,20 @@ public class JellyfinMusicVideoLibraryScannerTests
     // must reach ErsatzTV on the next scan. Before the fix, UpdateMetadata copied only scalar fields, so the
     // update path silently dropped every child collection — add-new AND remove-stale. This is an interaction
     // test: the repositories are substituted and GetOrAdd returns a canned existing item so we can verify the
-    // scanner issues the exact reconcile calls. (The real-DB double-scan approach can't drive this here: the
+    // scanner issues the exact reconcile calls.
-    // in-memory harness shares ONE SQLite connection across contexts, and mid-scan GetOrAdd's
-    // `MediaVersions.First().MediaFiles.First().Path` predicate mis-resolves once the existing item carries
-    // metadata children — a harness-only quirk; prod uses per-context pooled connections and looks music videos
-    // up by that predicate only because they carry no server ItemId. See the #497 close comment.)
     // Non-vacuous: reverting the Reconcile* calls in UpdateMetadata drops every Received() below.
     [Test]
     public async Task ScanLibrary_Should_Reconcile_Metadata_Collections_On_Rescan_Of_Existing_Item()
     {
-        JellyfinLibrary library = BuildLibrary(1, "/data/music");
-        var connectionParameters = new JellyfinConnectionParameters("http://jellyfin", "api-key", 1);
         const string VideoPath = "/data/music/artist1/song1.mkv";
 
         // the EXISTING item already in ErsatzTV, with the collections Jellyfin first gave it
-        var existing = new MusicVideo
+        var existing = new JellyfinMusicVideo
         {
             Id = 7,
             ArtistId = 3,
+            ItemId = ItemIdFor(VideoPath),
+            Etag = "old-etag",
             MediaVersions = new List<MediaVersion>
             {
                 new() { MediaFiles = new List<MediaFile> { new() { Path = VideoPath } }, Streams = new List<MediaStream>() }
@@ -321,51 +402,19 @@ public class JellyfinMusicVideoLibraryScannerTests
             }
         };
 
-        var artistRepository = Substitute.For<IArtistRepository>();
+        (JellyfinMusicVideoLibraryScanner scanner, IMusicVideoRepository musicVideoRepository,
-        artistRepository.GetArtistByMetadata(Arg.Any<int>(), Arg.Any<ArtistMetadata>())
+                IMetadataRepository metadataRepository) =
-            .Returns(Some(new Artist { Id = 3, ArtistMetadata = new List<ArtistMetadata>() }));
+            BuildScannerWithSubstitutes(
-        artistRepository.DeleteEmptyArtists(Arg.Any<LibraryPath>()).Returns(new List<int>());
+                existing,
-
-        var musicVideoRepository = Substitute.For<IMusicVideoRepository>();
-        musicVideoRepository
-            .GetOrAdd(Arg.Any<Artist>(), Arg.Any<LibraryPath>(), Arg.Any<LibraryFolder>(), Arg.Any<string>())
-            .Returns(Right<BaseError, MediaItemScanResult<MusicVideo>>(
-                new MediaItemScanResult<MusicVideo>(existing) { IsAdded = false }));
-        musicVideoRepository.FindMusicVideoPaths(Arg.Any<LibraryPath>())
-            .Returns(new List<string> { VideoPath }.AsEnumerable());
-        musicVideoRepository.AddGenre(Arg.Any<MusicVideoMetadata>(), Arg.Any<Genre>()).Returns(true);
-        musicVideoRepository.AddTag(Arg.Any<MusicVideoMetadata>(), Arg.Any<Tag>()).Returns(true);
-        musicVideoRepository.AddStudio(Arg.Any<MusicVideoMetadata>(), Arg.Any<Studio>()).Returns(true);
-        musicVideoRepository.AddArtist(Arg.Any<MusicVideoMetadata>(), Arg.Any<MusicVideoArtist>()).Returns(true);
-        musicVideoRepository.RemoveArtist(Arg.Any<MusicVideoArtist>()).Returns(true);
-
-        var metadataRepository = Substitute.For<IMetadataRepository>();
-        metadataRepository.Update(Arg.Any<ErsatzTV.Core.Domain.Metadata>()).Returns(true);
-        metadataRepository.UpdateStatistics(Arg.Any<MediaItem>(), Arg.Any<MediaVersion>(), Arg.Any<bool>()).Returns(false);
-        metadataRepository.RemoveGenre(Arg.Any<Genre>()).Returns(true);
-        metadataRepository.RemoveTag(Arg.Any<Tag>()).Returns(true);
-        metadataRepository.RemoveStudio(Arg.Any<Studio>()).Returns(true);
-
-        var libraryRepository = Substitute.For<ILibraryRepository>();
-        libraryRepository.GetParentFolderId(Arg.Any<LibraryPath>(), Arg.Any<string>(), Arg.Any<CancellationToken>())
-            .Returns(Option<int>.None);
-        libraryRepository.GetOrAddFolder(Arg.Any<LibraryPath>(), Arg.Any<Option<int>>(), Arg.Any<string>())
-            .Returns(new LibraryFolder { Id = 5, Path = "/data/music/artist1" });
-
-        JellyfinMusicVideoLibraryScanner scanner = BuildScannerWith(
                 FakeApi(() => BuildIncoming(
                     VideoPath, "Artist 1", "Song 1",
                     genres: new[] { "Synthwave", "Vaporwave" },
                     tags: new[] { "KeepTag", "NewTag" },
                     studios: new[] { "NewStudio" },
-                artists: new[] { "Artist 1", "Featured Y" })),
+                    artists: new[] { "Artist 1", "Featured Y" })));
-            artistRepository,
-            musicVideoRepository,
-            libraryRepository,
-            metadataRepository);
 
-        (await scanner.ScanLibrary(connectionParameters, library, deepScan: false, CancellationToken.None))
+        (await scanner.ScanLibrary(ConnectionParameters, BuildLibrary(1, "/data/music"), deepScan: false,
-            .IsRight.ShouldBeTrue();
+            CancellationToken.None)).IsRight.ShouldBeTrue();
 
         // remove-stale: Retro / DropTag / OldStudio / "Featured X" gone; kept items are NOT removed
         await metadataRepository.Received(1).RemoveGenre(Arg.Is<Genre>(g => g.Name == "Retro"));
@@ -478,8 +527,6 @@ public class JellyfinMusicVideoLibraryScannerTests
     [Test]
     public async Task ScanLibrary_Should_Update_Album_And_Track_On_Rescan_Of_Existing_Item()
     {
-        JellyfinLibrary library = BuildLibrary(1, "/data/music");
-        var connectionParameters = new JellyfinConnectionParameters("http://jellyfin", "api-key", 1);
         const string VideoPath = "/data/music/artist1/song1.mkv";
 
         var existingMetadata = new MusicVideoMetadata
@@ -493,10 +540,12 @@ public class JellyfinMusicVideoLibraryScannerTests
             Artists = [new MusicVideoArtist { Name = "Artist 1" }]
         };
 
-        var existing = new MusicVideo
+        var existing = new JellyfinMusicVideo
         {
             Id = 7,
             ArtistId = 3,
+            ItemId = ItemIdFor(VideoPath),
+            Etag = "old-etag",
             MediaVersions =
             [
                 new MediaVersion
@@ -508,43 +557,15 @@ public class JellyfinMusicVideoLibraryScannerTests
             MusicVideoMetadata = [existingMetadata]
         };
 
-        var artistRepository = Substitute.For<IArtistRepository>();
+        JellyfinMusicVideo incoming = BuildIncoming(VideoPath, "Artist 1", "Song 1");
-        artistRepository.GetArtistByMetadata(Arg.Any<int>(), Arg.Any<ArtistMetadata>())
-            .Returns(Some(new Artist { Id = 3, ArtistMetadata = new List<ArtistMetadata>() }));
-        artistRepository.DeleteEmptyArtists(Arg.Any<LibraryPath>()).Returns(new List<int>());
-
-        var musicVideoRepository = Substitute.For<IMusicVideoRepository>();
-        musicVideoRepository
-            .GetOrAdd(Arg.Any<Artist>(), Arg.Any<LibraryPath>(), Arg.Any<LibraryFolder>(), Arg.Any<string>())
-            .Returns(Right<BaseError, MediaItemScanResult<MusicVideo>>(
-                new MediaItemScanResult<MusicVideo>(existing) { IsAdded = false }));
-        musicVideoRepository.FindMusicVideoPaths(Arg.Any<LibraryPath>())
-            .Returns(new List<string> { VideoPath }.AsEnumerable());
-
-        var metadataRepository = Substitute.For<IMetadataRepository>();
-        metadataRepository.Update(Arg.Any<ErsatzTV.Core.Domain.Metadata>()).Returns(true);
-        metadataRepository.UpdateStatistics(Arg.Any<MediaItem>(), Arg.Any<MediaVersion>(), Arg.Any<bool>())
-            .Returns(false);
-
-        var libraryRepository = Substitute.For<ILibraryRepository>();
-        libraryRepository.GetParentFolderId(Arg.Any<LibraryPath>(), Arg.Any<string>(), Arg.Any<CancellationToken>())
-            .Returns(Option<int>.None);
-        libraryRepository.GetOrAddFolder(Arg.Any<LibraryPath>(), Arg.Any<Option<int>>(), Arg.Any<string>())
-            .Returns(new LibraryFolder { Id = 5, Path = "/data/music/artist1" });
-
-        MusicVideo incoming = BuildIncoming(VideoPath, "Artist 1", "Song 1");
         incoming.MusicVideoMetadata[0].Album = "Corrected Album";
         incoming.MusicVideoMetadata[0].Track = 4;
 
-        JellyfinMusicVideoLibraryScanner scanner = BuildScannerWith(
+        (JellyfinMusicVideoLibraryScanner scanner, _, _) =
-            FakeApi(() => incoming),
+            BuildScannerWithSubstitutes(existing, FakeApi(() => incoming));
-            artistRepository,
-            musicVideoRepository,
-            libraryRepository,
-            metadataRepository);
 
-        (await scanner.ScanLibrary(connectionParameters, library, deepScan: false, CancellationToken.None))
+        (await scanner.ScanLibrary(ConnectionParameters, BuildLibrary(1, "/data/music"), deepScan: false,
-            .IsRight.ShouldBeTrue();
+            CancellationToken.None)).IsRight.ShouldBeTrue();
 
         existingMetadata.Album.ShouldBe("Corrected Album");
         existingMetadata.Track.ShouldBe(4);
@@ -558,15 +579,15 @@ public class JellyfinMusicVideoLibraryScannerTests
     [Test]
     public async Task ScanLibrary_Should_Not_Double_Insert_Duplicate_Named_Incoming_Collection_Entries()
     {
-        JellyfinLibrary library = BuildLibrary(1, "/data/music");
-        var connectionParameters = new JellyfinConnectionParameters("http://jellyfin", "api-key", 1);
         const string VideoPath = "/data/music/artist1/song1.mkv";
 
         // the existing item carries NONE of the incoming names, so every incoming entry is an "add"
-        var existing = new MusicVideo
+        var existing = new JellyfinMusicVideo
         {
             Id = 7,
             ArtistId = 3,
+            ItemId = ItemIdFor(VideoPath),
+            Etag = "old-etag",
             MediaVersions =
             [
                 new MediaVersion
@@ -588,49 +609,19 @@ public class JellyfinMusicVideoLibraryScannerTests
             ]
         };
 
-        var artistRepository = Substitute.For<IArtistRepository>();
-        artistRepository.GetArtistByMetadata(Arg.Any<int>(), Arg.Any<ArtistMetadata>())
-            .Returns(Some(new Artist { Id = 3, ArtistMetadata = new List<ArtistMetadata>() }));
-        artistRepository.DeleteEmptyArtists(Arg.Any<LibraryPath>()).Returns(new List<int>());
-
-        var musicVideoRepository = Substitute.For<IMusicVideoRepository>();
-        musicVideoRepository
-            .GetOrAdd(Arg.Any<Artist>(), Arg.Any<LibraryPath>(), Arg.Any<LibraryFolder>(), Arg.Any<string>())
-            .Returns(Right<BaseError, MediaItemScanResult<MusicVideo>>(
-                new MediaItemScanResult<MusicVideo>(existing) { IsAdded = false }));
-        musicVideoRepository.FindMusicVideoPaths(Arg.Any<LibraryPath>())
-            .Returns(new List<string> { VideoPath }.AsEnumerable());
-        musicVideoRepository.AddGenre(Arg.Any<MusicVideoMetadata>(), Arg.Any<Genre>()).Returns(true);
-        musicVideoRepository.AddTag(Arg.Any<MusicVideoMetadata>(), Arg.Any<Tag>()).Returns(true);
-        musicVideoRepository.AddStudio(Arg.Any<MusicVideoMetadata>(), Arg.Any<Studio>()).Returns(true);
-        musicVideoRepository.AddArtist(Arg.Any<MusicVideoMetadata>(), Arg.Any<MusicVideoArtist>()).Returns(true);
-
-        var metadataRepository = Substitute.For<IMetadataRepository>();
-        metadataRepository.Update(Arg.Any<ErsatzTV.Core.Domain.Metadata>()).Returns(true);
-        metadataRepository.UpdateStatistics(Arg.Any<MediaItem>(), Arg.Any<MediaVersion>(), Arg.Any<bool>())
-            .Returns(false);
-
-        var libraryRepository = Substitute.For<ILibraryRepository>();
-        libraryRepository.GetParentFolderId(Arg.Any<LibraryPath>(), Arg.Any<string>(), Arg.Any<CancellationToken>())
-            .Returns(Option<int>.None);
-        libraryRepository.GetOrAddFolder(Arg.Any<LibraryPath>(), Arg.Any<Option<int>>(), Arg.Any<string>())
-            .Returns(new LibraryFolder { Id = 5, Path = "/data/music/artist1" });
-
         // Jellyfin reports each name TWICE for the same item
-        JellyfinMusicVideoLibraryScanner scanner = BuildScannerWith(
+        (JellyfinMusicVideoLibraryScanner scanner, IMusicVideoRepository musicVideoRepository, _) =
+            BuildScannerWithSubstitutes(
+                existing,
                 FakeApi(() => BuildIncoming(
                     VideoPath, "Artist 1", "Song 1",
                     genres: ["Synthwave", "Synthwave"],
                     tags: ["DupTag", "DupTag"],
                     studios: ["DupStudio", "DupStudio"],
-                artists: ["Artist 1", "Artist 1"])),
+                    artists: ["Artist 1", "Artist 1"])));
-            artistRepository,
-            musicVideoRepository,
-            libraryRepository,
-            metadataRepository);
 
-        (await scanner.ScanLibrary(connectionParameters, library, deepScan: false, CancellationToken.None))
+        (await scanner.ScanLibrary(ConnectionParameters, BuildLibrary(1, "/data/music"), deepScan: false,
-            .IsRight.ShouldBeTrue();
+            CancellationToken.None)).IsRight.ShouldBeTrue();
 
         await musicVideoRepository.Received(1)
             .AddGenre(Arg.Any<MusicVideoMetadata>(), Arg.Is<Genre>(g => g.Name == "Synthwave"));
@@ -649,37 +640,131 @@ public class JellyfinMusicVideoLibraryScannerTests
         metadata.Artists.Count.ShouldBe(1);
     }
 
-    private JellyfinMusicVideoLibraryScanner BuildScannerWith(
+    private static JellyfinConnectionParameters ConnectionParameters =>
-        IJellyfinApiClient apiClient,
+        new("http://jellyfin", "api-key", 1);
-        IArtistRepository artistRepository,
+
-        IMusicVideoRepository musicVideoRepository,
+    // A stable per-file server item id, so a re-scan of the same file is the same identity.
-        ILibraryRepository libraryRepository,
+    private static string ItemIdFor(string path) => $"item-{PathUtils.GetPathHash(path)}";
-        IMetadataRepository metadataRepository)
+
+    private (JellyfinMusicVideoLibraryScanner Scanner, IMusicVideoRepository MusicVideoRepository,
+        IMetadataRepository MetadataRepository) BuildScannerWithSubstitutes(
+            JellyfinMusicVideo existing,
+            IJellyfinApiClient apiClient)
+    {
+        var artistRepository = Substitute.For<IArtistRepository>();
+        artistRepository.GetArtistByMetadata(Arg.Any<int>(), Arg.Any<ArtistMetadata>())
+            .Returns(Some(new Artist { Id = 3, ArtistMetadata = new List<ArtistMetadata>() }));
+        artistRepository.DeleteEmptyArtists(Arg.Any<LibraryPath>()).Returns(new List<int>());
+
+        var jellyfinMusicVideoRepository = Substitute.For<IJellyfinMusicVideoRepository>();
+        jellyfinMusicVideoRepository.GetOrAdd(
+                Arg.Any<JellyfinLibrary>(),
+                Arg.Any<Artist>(),
+                Arg.Any<LibraryFolder>(),
+                Arg.Any<JellyfinMusicVideo>(),
+                Arg.Any<bool>(),
+                Arg.Any<CancellationToken>())
+            .Returns(Right<BaseError, MediaItemScanResult<JellyfinMusicVideo>>(
+                new MediaItemScanResult<JellyfinMusicVideo>(existing) { IsAdded = false }));
+        jellyfinMusicVideoRepository.GetExistingMusicVideos(Arg.Any<JellyfinLibrary>())
+            .Returns(new List<JellyfinItemEtag>
+            {
+                new() { ItemId = existing.ItemId, Etag = existing.Etag, State = MediaItemState.Normal }
+            });
+        jellyfinMusicVideoRepository.FlagFileNotFound(Arg.Any<JellyfinLibrary>(), Arg.Any<List<string>>())
+            .Returns(new List<int>());
+
+        var musicVideoRepository = Substitute.For<IMusicVideoRepository>();
+        musicVideoRepository.AddGenre(Arg.Any<MusicVideoMetadata>(), Arg.Any<Genre>()).Returns(true);
+        musicVideoRepository.AddTag(Arg.Any<MusicVideoMetadata>(), Arg.Any<Tag>()).Returns(true);
+        musicVideoRepository.AddStudio(Arg.Any<MusicVideoMetadata>(), Arg.Any<Studio>()).Returns(true);
+        musicVideoRepository.AddArtist(Arg.Any<MusicVideoMetadata>(), Arg.Any<MusicVideoArtist>()).Returns(true);
+        musicVideoRepository.RemoveArtist(Arg.Any<MusicVideoArtist>()).Returns(true);
+
+        var metadataRepository = Substitute.For<IMetadataRepository>();
+        metadataRepository.Update(Arg.Any<ErsatzTV.Core.Domain.Metadata>()).Returns(true);
+        metadataRepository.UpdateStatistics(Arg.Any<MediaItem>(), Arg.Any<MediaVersion>(), Arg.Any<bool>())
+            .Returns(false);
+        metadataRepository.RemoveGenre(Arg.Any<Genre>()).Returns(true);
+        metadataRepository.RemoveTag(Arg.Any<Tag>()).Returns(true);
+        metadataRepository.RemoveStudio(Arg.Any<Studio>()).Returns(true);
+
+        var libraryRepository = Substitute.For<ILibraryRepository>();
+        libraryRepository.GetParentFolderId(Arg.Any<LibraryPath>(), Arg.Any<string>(), Arg.Any<CancellationToken>())
+            .Returns(Option<int>.None);
+        libraryRepository.GetOrAddFolder(Arg.Any<LibraryPath>(), Arg.Any<Option<int>>(), Arg.Any<string>())
+            .Returns(new LibraryFolder { Id = 5, Path = "/data/music/artist1" });
+
+        var scanner = new JellyfinMusicVideoLibraryScanner(
+            BuildScannerProxy(),
+            apiClient,
+            jellyfinMusicVideoRepository,
+            BuildPathReplacement(),
+            BuildMediaSourceRepository(),
+            artistRepository,
+            musicVideoRepository,
+            libraryRepository,
+            metadataRepository,
+            BuildFileSystem(),
+            NullLogger<JellyfinMusicVideoLibraryScanner>.Instance);
+
+        return (scanner, musicVideoRepository, metadataRepository);
+    }
+
+    private (JellyfinMusicVideoLibraryScanner Scanner, IScannerProxy ScannerProxy) BuildScanner(
+        IJellyfinApiClient apiClient)
+    {
+        IScannerProxy scannerProxy = BuildScannerProxy();
+
+        var scanner = new JellyfinMusicVideoLibraryScanner(
+            scannerProxy,
+            apiClient,
+            new JellyfinMusicVideoRepository(_db.Factory, NullLogger<JellyfinMusicVideoRepository>.Instance),
+            BuildPathReplacement(),
+            BuildMediaSourceRepository(),
+            new ArtistRepository(_db.Factory),
+            new MusicVideoRepository(_db.Factory),
+            new LibraryRepository(Substitute.For<IFileSystem>(), _db.Factory),
+            Substitute.For<IMetadataRepository>(),
+            BuildFileSystem(),
+            NullLogger<JellyfinMusicVideoLibraryScanner>.Instance);
+
+        return (scanner, scannerProxy);
+    }
+
+    private static IScannerProxy BuildScannerProxy()
+    {
+        var scannerProxy = Substitute.For<IScannerProxy>();
+        scannerProxy.UpdateProgress(Arg.Any<decimal>(), Arg.Any<CancellationToken>()).Returns(true);
+        scannerProxy.ReindexMediaItems(Arg.Any<int[]>(), Arg.Any<CancellationToken>()).Returns(true);
+        scannerProxy.RemoveMediaItems(Arg.Any<int[]>(), Arg.Any<CancellationToken>()).Returns(true);
+        return scannerProxy;
+    }
+
+    private static IJellyfinPathReplacementService BuildPathReplacement()
     {
         var pathReplacement = Substitute.For<IJellyfinPathReplacementService>();
         pathReplacement
             .GetReplacementJellyfinPath(Arg.Any<List<JellyfinPathReplacement>>(), Arg.Any<string>(), Arg.Any<bool>())
             .Returns(ci => ci.ArgAt<string>(1));
+        return pathReplacement;
+    }
 
+    private static IMediaSourceRepository BuildMediaSourceRepository()
+    {
         var mediaSourceRepository = Substitute.For<IMediaSourceRepository>();
         mediaSourceRepository.GetJellyfinPathReplacements(Arg.Any<int>())
             .Returns(Task.FromResult(new List<JellyfinPathReplacement>()));
+        return mediaSourceRepository;
+    }
 
-        var scannerProxy = Substitute.For<IScannerProxy>();
+    // every scanned file "exists" locally, so scanned items settle in Normal and a FileNotFound state can only
-        scannerProxy.UpdateProgress(Arg.Any<decimal>(), Arg.Any<CancellationToken>()).Returns(true);
+    // come from the sweep under test
-        scannerProxy.ReindexMediaItems(Arg.Any<int[]>(), Arg.Any<CancellationToken>()).Returns(true);
+    private static IFileSystem BuildFileSystem()
-        scannerProxy.RemoveMediaItems(Arg.Any<int[]>(), Arg.Any<CancellationToken>()).Returns(true);
+    {
-
+        var fileSystem = Substitute.For<IFileSystem>();
-        return new JellyfinMusicVideoLibraryScanner(
+        fileSystem.File.Exists(Arg.Any<string>()).Returns(true);
-            scannerProxy,
+        return fileSystem;
-            apiClient,
-            pathReplacement,
-            mediaSourceRepository,
-            artistRepository,
-            musicVideoRepository,
-            libraryRepository,
-            metadataRepository,
-            NullLogger<JellyfinMusicVideoLibraryScanner>.Instance);
     }
 
     private async Task<int> MusicVideoId(string path)
@@ -694,6 +779,13 @@ public class JellyfinMusicVideoLibraryScannerTests
             .Id;
     }
 
+    private async Task<MediaItemState> MediaItemStateOf(int mediaItemId)
+    {
+        await using TvContext context = _db.CreateContext();
+        MediaItem mediaItem = await context.MediaItems.SingleAsync(mi => mi.Id == mediaItemId);
+        return mediaItem.State;
+    }
+
     private async Task<List<string>> MusicVideoPaths(int libraryPathId)
     {
         await using TvContext context = _db.CreateContext();
@@ -718,78 +810,9 @@ public class JellyfinMusicVideoLibraryScannerTests
         return artists.Select(a => a.ArtistMetadata.Single().Title).OrderBy(t => t).ToList();
     }
 
-    private (JellyfinMusicVideoLibraryScanner Scanner, IScannerProxy ScannerProxy) BuildScanner(
+    // Each Func builds a fresh music video so the async stream can be re-enumerated across ScanLibrary calls
-        IJellyfinApiClient apiClient)
-    {
-        var pathReplacement = Substitute.For<IJellyfinPathReplacementService>();
-        pathReplacement
-            .GetReplacementJellyfinPath(Arg.Any<List<JellyfinPathReplacement>>(), Arg.Any<string>(), Arg.Any<bool>())
-            .Returns(ci => ci.ArgAt<string>(1));
-
-        var mediaSourceRepository = Substitute.For<IMediaSourceRepository>();
-        mediaSourceRepository.GetJellyfinPathReplacements(Arg.Any<int>())
-            .Returns(Task.FromResult(new List<JellyfinPathReplacement>()));
-
-        var scannerProxy = Substitute.For<IScannerProxy>();
-        scannerProxy.UpdateProgress(Arg.Any<decimal>(), Arg.Any<CancellationToken>()).Returns(true);
-        scannerProxy.ReindexMediaItems(Arg.Any<int[]>(), Arg.Any<CancellationToken>()).Returns(true);
-        scannerProxy.RemoveMediaItems(Arg.Any<int[]>(), Arg.Any<CancellationToken>()).Returns(true);
-
-        var scanner = new JellyfinMusicVideoLibraryScanner(
-            scannerProxy,
-            apiClient,
-            pathReplacement,
-            mediaSourceRepository,
-            new ArtistRepository(_db.Factory),
-            new MusicVideoRepository(_db.Factory),
-            new LibraryRepository(Substitute.For<IFileSystem>(), _db.Factory),
-            Substitute.For<IMetadataRepository>(),
-            NullLogger<JellyfinMusicVideoLibraryScanner>.Instance);
-
-        return (scanner, scannerProxy);
-    }
-
-    // #484 finding 3: the api client records projection failures into the counter the SCANNER created and
-    // handed it. This fake does the same, so the test exercises the same-instance join that
-    // JellyfinMusicVideoLibraryScanner.ScanLibrary makes between GetMusicVideoLibraryItems and the sweep.
-    private static IJellyfinApiClient FakeApiWithProjectionFailures(
-        int projectionFailureCount,
-        params Func<MusicVideo>[] items)
-    {
-        var apiClient = Substitute.For<IJellyfinApiClient>();
-        apiClient.GetMusicVideoLibraryItems(
-                Arg.Any<string>(),
-                Arg.Any<string>(),
-                Arg.Any<JellyfinLibrary>(),
-                Arg.Any<MediaServerProjectionFailureCounter>())
-            .Returns(ci => ItemsWithFailures(
-                items,
-                projectionFailureCount,
-                ci.ArgAt<MediaServerProjectionFailureCounter>(3)));
-        return apiClient;
-    }
-
-    private static async IAsyncEnumerable<Tuple<MusicVideo, int>> ItemsWithFailures(
-        Func<MusicVideo>[] items,
-        int projectionFailureCount,
-        MediaServerProjectionFailureCounter projectionFailures)
-    {
-        for (var i = 0; i < projectionFailureCount; i++)
-        {
-            projectionFailures.RecordFailure();
-        }
-
-        foreach (Func<MusicVideo> item in items)
-        {
-            yield return new Tuple<MusicVideo, int>(item(), items.Length + projectionFailureCount);
-        }
-
-        await Task.CompletedTask;
-    }
-
-    // Each Func builds a fresh MusicVideo so the async stream can be re-enumerated across ScanLibrary calls
     // (an IAsyncEnumerable iterator is single-use, and the scanner mutates the incoming item).
-    private static IJellyfinApiClient FakeApi(params Func<MusicVideo>[] items)
+    private static IJellyfinApiClient FakeApi(params Func<JellyfinMusicVideo>[] items)
     {
         var apiClient = Substitute.For<IJellyfinApiClient>();
         apiClient.GetMusicVideoLibraryItems(
@@ -801,31 +824,31 @@ public class JellyfinMusicVideoLibraryScannerTests
         return apiClient;
     }
 
-    private static async IAsyncEnumerable<Tuple<MusicVideo, int>> Items(Func<MusicVideo>[] items)
+    private static async IAsyncEnumerable<Tuple<JellyfinMusicVideo, int>> Items(Func<JellyfinMusicVideo>[] items)
     {
-        foreach (Func<MusicVideo> item in items)
+        foreach (Func<JellyfinMusicVideo> item in items)
         {
-            yield return new Tuple<MusicVideo, int>(item(), items.Length);
+            yield return new Tuple<JellyfinMusicVideo, int>(item(), items.Length);
         }
 
         await Task.CompletedTask;
     }
 
-    private static JellyfinLibrary BuildLibrary(int libraryPathId, string path)
+    private static JellyfinLibrary BuildLibrary(int libraryPathId, string path, int libraryId = 42)
     {
         var libraryPath = new LibraryPath { Id = libraryPathId, Path = path, LibraryFolders = null };
         return new JellyfinLibrary
         {
-            Id = 42,
+            Id = libraryId,
             MediaSourceId = 1,
-            ItemId = "lib15",
+            ItemId = $"lib{libraryId}",
             Name = "Music",
             ShouldSyncItems = true,
             Paths = new List<LibraryPath> { libraryPath }
         };
     }
 
-    private static MusicVideo BuildIncoming(
+    private static JellyfinMusicVideo BuildIncoming(
         string path,
         string artistName,
         string title,
@@ -835,6 +858,8 @@ public class JellyfinMusicVideoLibraryScannerTests
         IEnumerable<string> artists = null) =>
         new()
         {
+            ItemId = ItemIdFor(path),
+            Etag = $"etag-{title}",
             MediaVersions = new List<MediaVersion>
             {
                 new()
@@ -858,18 +883,76 @@ public class JellyfinMusicVideoLibraryScannerTests
             }
         };
 
-    private static async IAsyncEnumerable<Tuple<MusicVideo, int>> OneItem(MusicVideo musicVideo)
+    // Seeds a real JellyfinLibrary row owning the LibraryPath. ersatztv#496 made this load-bearing: identity
-    {
+    // lookups and the sweep are scoped per LIBRARY (GetExistingMusicVideos / FlagFileNotFound both join
-        yield return new Tuple<MusicVideo, int>(musicVideo, 1);
+    // LibraryPath.LibraryId), so a dangling LibraryPath with no owning library would silently match nothing.
-        await Task.CompletedTask;
+    private async Task<int> SeedLibraryPath(string path, int libraryId = 42)
-    }
-
-    private async Task<int> SeedLibraryPath(string path)
     {
         await using TvContext context = _db.CreateContext();
+
         var libraryPath = new LibraryPath { Path = path };
-        await context.LibraryPaths.AddAsync(libraryPath);
+        var library = new JellyfinLibrary
+        {
+            Id = libraryId,
+            MediaSourceId = 1,
+            ItemId = $"lib{libraryId}",
+            Name = "Music",
+            ShouldSyncItems = true,
+            Paths = new List<LibraryPath> { libraryPath }
+        };
+
+        await context.Libraries.AddAsync(library);
         await context.SaveChangesAsync();
         return libraryPath.Id;
     }
+
+    // a MusicVideo row with NO JellyfinMusicVideo identity — what the pre-#496 scanner (and the local
+    // MusicVideoFolderScanner) leaves behind
+    private async Task<int> SeedPlainMusicVideo(int libraryPathId, string path, string artistName)
+    {
+        await using TvContext context = _db.CreateContext();
+
+        var artist = new Artist
+        {
+            LibraryPathId = libraryPathId,
+            ArtistMetadata = new List<ArtistMetadata> { new() { Title = artistName } }
+        };
+        await context.Artists.AddAsync(artist);
+        await context.SaveChangesAsync();
+
+        var musicVideo = new MusicVideo
+        {
+            ArtistId = artist.Id,
+            LibraryPathId = libraryPathId,
+            MusicVideoMetadata = new List<MusicVideoMetadata> { new() { Title = "Song 1" } },
+            MediaVersions = new List<MediaVersion>
+            {
+                new()
+                {
+                    MediaFiles = new List<MediaFile>
+                    {
+                        new() { Path = path, PathHash = PathUtils.GetPathHash(path) }
+                    },
+                    Streams = new List<MediaStream>()
+                }
+            }
+        };
+        await context.MusicVideos.AddAsync(musicVideo);
+        await context.SaveChangesAsync();
+
+        return musicVideo.Id;
+    }
+
+    private async Task<int> SeedCollectionWith(int mediaItemId)
+    {
+        await using TvContext context = _db.CreateContext();
+        var collection = new Collection
+        {
+            Name = "Vaporwave",
+            CollectionItems = new List<CollectionItem> { new() { MediaItemId = mediaItemId } }
+        };
+        await context.Collections.AddAsync(collection);
+        await context.SaveChangesAsync();
+        return collection.Id;
+    }
 }

ErsatzTV/Startup.cs

@@ -1127,6 +1127,7 @@ public class Startup
         services.AddScoped<IJellyfinTelevisionRepository, JellyfinTelevisionRepository>();
         services.AddScoped<IJellyfinCollectionRepository, JellyfinCollectionRepository>();
         services.AddScoped<IJellyfinMovieRepository, JellyfinMovieRepository>();
+        services.AddScoped<IJellyfinMusicVideoRepository, JellyfinMusicVideoRepository>();
         services.AddScoped<IEmbyApiClient, EmbyApiClient>();
         services.AddScoped<IEmbyPathReplacementService, EmbyPathReplacementService>();
         services.AddScoped<IEmbyTelevisionRepository, EmbyTelevisionRepository>();

docs/decisions.md

@@ -2530,47 +2530,6 @@ remote scanner tripped it, and the feature had never run in prod, CI, or locally
   still reads `libraryPath.LibraryFolders` directly, but it is only reached on the local (eager-loaded) path, so
   it is not affected; left as-is (out of #488 scope).
 
-## 2026-07-20 — `JellyfinMusicVideoLibraryScanner` reconciles by library-scoped path diff + hard delete, not server itemId soft-trash (#494)
-`key: scan.musicvideo-reconciliation` · `status: active` · `since: 2026-07-20` · `supersedes: none` · `superseded-by: none`
-**Rule:** `JellyfinMusicVideoLibraryScanner` reconciles removed music videos by a library-scoped local-path diff plus hard delete (`TrashMissingMusicVideos`), not the server-itemId soft-trash pattern the other media-server scanners use, because music videos carry no server identity.
-**Signals:** music-video trash sweep, path-based identity, cross-kind safety, path-keyed identity, empty-fetch guard reuse, remove-stale+add-new dedup · paths: `JellyfinMusicVideoLibraryScanner.TrashMissingMusicVideos`, `FindMusicVideoPaths`/`DeleteByPath`, `IMusicVideoRepository`, `MediaServerReconciliationGuard` · issues: #494, #477, #488, #496, #500
-**Mechanics:** `ScanLibrary_Should_Not_CrossDelete_Movie_Or_Show_Sharing_The_LibraryPath`; `ScanLibrary_Should_Not_Sweep_When_Jellyfin_Returns_Zero_Items`; integration tests extending the #488 harness. #500 — when mirroring the remove-stale + add-new idiom, dedup the incoming set on **the same key its add filter compares** (the filter is materialized before the loop mutates `existing`, so duplicates both pass): `Name`, `Guid` for guids, and for Plex `Actors` an artwork-preferring dedup shared with the remove filter (whose key is `(Name, artwork-presence)`). Remaining un-deduped copies of the idiom: #600.
-
-The Jellyfin music-video scanner did add/update only — a music video removed on the Jellyfin side lingered in
-ErsatzTV forever and could still be scheduled. It now runs a trash sweep at the end of `ScanLibrary`
-(`TrashMissingMusicVideos`), mirroring the `MediaServer{Movie,Television,OtherVideo}LibraryScanner` "gone
-upstream ⇒ remove" pattern but with a deliberately different identity function, because music videos lack the
-media-server identity those base scanners rely on.
-
-- **Identity is (LibraryPathId, path), not server itemId.** The base scanners diff `GetExisting*` (keyed by
-  `MediaServerItemId`) against the incoming server item ids, then soft-trash via `FlagFileNotFound`. Music videos
-  have **no `JellyfinMusicVideo` entity and no `ItemId`/`Etag`** — the scanner is a standalone
-  `IJellyfinMusicVideoLibraryScanner` that injects the *local* `IMusicVideoRepository`, which offers no
-  itemId-keyed existing-set or flag seam. So the sweep diffs the **local path** set instead: existing =
-  `FindMusicVideoPaths(libraryPath)` `.Except` the incoming items' replaced local paths, then hard-deletes the
-  remainder with `DeleteByPath` + `IScannerProxy.RemoveMediaItems`, and cleans now-empty artists with
-  `IArtistRepository.DeleteEmptyArtists`. Hard delete (not soft `FileNotFound` trash) because there is no
-  per-item FileNotFound seam on this path and the issue's Done-when is "removed".
-- **Cross-kind safety is a property of the queries, not the media kind.** `MediaItem` is TPT with `LibraryPathId`
-  on the abstract base, so a Movie, Show and MusicVideo can share one `LibraryPath` (a mixed Jellyfin library).
-  Both `FindMusicVideoPaths` and `DeleteByPath` filter `LibraryPathId` **and** join the concrete `MusicVideo`
-  table, so the sweep can only ever see/delete music videos — a Movie/Show under the same `LibraryPath` is
-  invisible to it. Pinned by `ScanLibrary_Should_Not_CrossDelete_Movie_Or_Show_Sharing_The_LibraryPath`.
-- **Reuses the #477 empty-fetch guard.** The sweep is gated by `MediaServerReconciliationGuard.ShouldFlagMissing`
-  — a successful fetch that returns zero items (server mid-restore / transient) is indistinguishable from a real
-  emptying, so the whole-library wipe is refused and logged. Pinned as a negative control by
-  `ScanLibrary_Should_Not_Sweep_When_Jellyfin_Returns_Zero_Items` (removing the guard flips it red).
-- **Known limitation (deferred to per-library identity).** `MusicVideoRepository.GetOrAdd` dedups a path
-  **globally** (no `LibraryPathId` predicate), so a file served by two libraries with overlapping local paths is
-  a single row owned by whichever library scanned it first. If that owner later stops reporting the file while
-  another library still serves it, this sweep removes the shared row. A proper fix needs per-library music-video
-  identity (a `JellyfinMusicVideo` etag entity + migration) — the issue's "option 2 / fold into the base
-  scanner" refactor — tracked as #496.
-- **Tests.** Integration tests (real `ArtistRepository`/`MusicVideoRepository`/`LibraryRepository` over in-memory
-  SQLite, extending the #488 harness) pin removal, empty-artist cleanup, cross-kind safety, and the empty-fetch
-  guard. Proven non-vacuous: all four fail against the pre-fix scanner except the guard control, which only
-  earns its keep once the sweep exists.
-
 ## 2026-07-20 (#489) — Jellyfin mixed-content libraries map to one library holding many kinds
 `key: scan.jellyfin-mixed-content-library` · `status: active` · `since: 2026-07-20` · `supersedes: none` · `superseded-by: none`
 **Rule:** A Jellyfin library whose collection type is `mixed` (or absent) maps to one ErsatzTV library of `LibraryMediaKind.Mixed`, scanned by running the movie/television/music-video scanners in sequence against that single library — a library is a place, not a media kind.
@@ -3895,3 +3854,41 @@ This is a **second, independent** refusal on the same guard, plus a decision not
   Sweep`, the two nested TV cases, and `JellyfinMusicVideoLibraryScannerTests
   .MusicVideo_Sweep_Respects_Projection_Failures` all drive the real `ScanLibrary` entry point and record
   the failure from *inside* the enumeration, so same-instance wiring is what makes them pass.
+## 2026-07-25 — Music videos carry a per-library server identity; reconciliation is an itemId diff + soft trash (#496)
+`key: scan.musicvideo-server-identity` · `status: active` · `since: 2026-07-25` · `supersedes: scan.musicvideo-reconciliation@2026-07-20` · `superseded-by: none`
+**Rule:** Jellyfin music videos carry a per-library server identity (`JellyfinMusicVideo : MusicVideo` with `ItemId`/`Etag`, TPT table + ItemId index), so `JellyfinMusicVideoLibraryScanner` folds onto a shared `MediaServerMusicVideoLibraryScanner` base that diffs the **server item id** and soft-trashes (`FlagFileNotFound`) instead of diffing local paths and hard-deleting. Rows predating the identity are **adopted in place** — the identity row is inserted against the same `MediaItem` id, scoped to the scanned library's own `LibraryPath` — never deleted and re-added.
+**Signals:** music-video server identity, JellyfinMusicVideo ItemId/Etag, itemId diff, soft FileNotFound trash, adoption of pre-identity rows, cross-library false-trash, path-replaced PathHash · paths: `JellyfinMusicVideo`, `JellyfinMusicVideoRepository`, `IMediaServerMusicVideoRepository`, `MediaServerMusicVideoLibraryScanner`, `JellyfinMusicVideoLibraryScanner` · issues: #496, #494, #477, #488, #497, #500
+**Mechanics:** dual-provider migration `Add_JellyfinMusicVideo`; adoption probe joins `MediaFile.PathHash` + `NOT EXISTS (JellyfinMusicVideo)` filtered to the library's `LibraryPath`; `AddMusicVideo` normalizes `Path`/`PathHash` to the path-REPLACED local path; `ScanLibrary_Should_Adopt_PreExisting_MusicVideo_Preserving_Identity_And_Collections`, `ScanLibrary_Should_Not_Adopt_A_MusicVideo_Owned_By_Another_LibraryPath`, `ScanLibrary_Should_Not_Flag_MusicVideos_Owned_By_Another_Library`
+
+#494 gave music videos a trash sweep but had to key it on `(LibraryPathId, path)` and hard-delete, because
+music videos carried no server identity. That left the known limitation this issue is named for: a file served
+by two libraries with overlapping local paths is one row owned by whichever library scanned it first, and that
+owner's sweep **destroyed** the row the other library still served. This is the deferred "option 2".
+
+- **Identity is the server item id, per library.** `JellyfinMusicVideo` mirrors `JellyfinMovie` exactly (TPT
+  table, `ItemId`/`Etag` `varchar(36)`, index on `ItemId`). `GetExistingMusicVideos` and `FlagFileNotFound` both
+  join `LibraryPath.LibraryId`, so the existing-set and the flag set are scoped to the scanning library — one
+  library's sweep can no longer resolve, let alone remove, another library's row.
+- **Soft trash replaces hard delete.** The sweep now flags `FileNotFound` (`State = 1`) like the
+  movie/TV/other-video base scanners. The row survives, so collection membership, playout references and
+  artwork survive with it, and removal is `EmptyTrash`-governed and reversible. The visible consequence is that
+  `DeleteEmptyArtists` no longer fires from a sweep — a trashed music video still belongs to its artist.
+- **Pre-identity rows are ADOPTED, not re-added.** Every music video on an existing install has no
+  `JellyfinMusicVideo` row and so can never be found by item id. Deleting and re-adding would mint a new
+  `MediaItem` id and silently drop `CollectionItem` membership; `MediaItemRepository.MediaFileAlreadyExists`
+  would in fact block the re-add outright and the item would error on every scan forever. So `GetOrAdd` probes
+  for an identity-less `MusicVideo` at the same `PathHash` **within the scanned library's own `LibraryPath`**
+  and inserts the identity row against that same id. The scoping is the point: the local
+  `MusicVideoFolderScanner` writes the same `MusicVideo` table, and a local (or second-library) row must never
+  be hijacked into this library's identity.
+- **The adopted row is written with an empty etag** so the ordinary "etag changed ⇒ refresh" path picks it up
+  once, rather than needing a second adoption-specific update path.
+- **`Path`/`PathHash` are normalized to the path-REPLACED local path on add.** The projection fills them from
+  the path Jellyfin reported, but music videos have always stored the replaced local path. Storing the
+  projection's hash would break every later `PathHash` lookup — `MediaFileAlreadyExists` and the adoption probe
+  above. Caught by the #488 integration test failing on a `NOT NULL`/`UNIQUE` `PathHash` constraint.
+- **Scope honesty: this is parity, not a total fix.** One file path is still one `MediaItem` row globally
+  (`MediaFileAlreadyExists` is a global path-hash guard), so a second library serving the same file still gets
+  no row of its own — exactly as for movies/TV. What changes is that the first library's sweep now *flags*
+  rather than *destroys* that shared row. The unrecoverable data loss is gone; the shared-row limitation is a
+  whole-app property, not a music-video one.

docs/decisions/README.md

@@ -115,6 +115,7 @@ the link for rationale. Superseded/retired history lives in `archive/`. Regenera
 | `scan.jellyfin-mixed-content-library` | A Jellyfin library whose collection type is `mixed` (or absent) maps to one ErsatzTV library of `LibraryMediaKind.Mixed`, scanned by running the movie/television/music-video scanners in sequence against that single library — a library is a place, not a media kind. | 2026-07-20 | [link](../decisions.md#2026-07-20-489--jellyfin-mixed-content-libraries-map-to-one-library-holding-many-kinds) |
 | `scan.musicvideo-reconciliation` | `JellyfinMusicVideoLibraryScanner` reconciles removed music videos by a library-scoped local-path diff plus hard delete (`TrashMissingMusicVideos`), not the server-itemId soft-trash pattern the other media-server scanners use, because music videos carry no server identity. | 2026-07-20 | [link](../decisions.md#2026-07-20--jellyfinmusicvideolibraryscanner-reconciles-by-library-scoped-path-diff--hard-delete-not-server-itemid-soft-trash-494) |
 | `scan.projection-failure-sweep-guard` | `MediaServerReconciliationGuard` takes a per-enumeration projection-failure count and refuses the file-not-found sweep (logged loudly) whenever it is non-zero against a non-empty existing set — at all six sweeps, including the nested per-show season and per-season episode ones #477 left unguarded (via `ShouldFlagMissingDescendants`, which applies the failure refusal but not #477's empty-fetch branch). Deliberate guard-clause skips (STRM, virtual, unsupported type) are explicitly **not** failures and never suppress a sweep. The missing-fraction / ratio threshold floated by #477 is **rejected**, not deferred. | 2026-07-25 | [link](../decisions.md#2026-07-25--a-media-server-sweep-also-refuses-when-the-api-client-silently-dropped-items-whose-projection-threw-the-ratio-threshold-is-rejected-484) |
+| `scan.musicvideo-server-identity` | Jellyfin music videos carry a per-library server identity (`JellyfinMusicVideo : MusicVideo` with `ItemId`/`Etag`, TPT table + ItemId index), so `JellyfinMusicVideoLibraryScanner` folds onto a shared `MediaServerMusicVideoLibraryScanner` base that diffs the **server item id** and soft-trashes (`FlagFileNotFound`) instead of diffing local paths and hard-deleting. Rows predating the identity are **adopted in place** — the identity row is inserted against the same `MediaItem` id, scoped to the scanned library's own `LibraryPath` — never deleted and re-added. | 2026-07-25 | [link](../decisions.md#2026-07-25--music-videos-carry-a-per-library-server-identity-reconciliation-is-an-itemid-diff--soft-trash-496) |
 | `scan.zero-item-fetch-guard` | A media-server library sweep refuses to flag missing items when a successful fetch returns zero incoming items against a non-empty existing set (`MediaServerReconciliationGuard.ShouldFlagMissing`), rather than treating an ambiguous empty result as a full-library deletion. | 2026-07-19 | [link](../decisions.md#2026-07-19--a-media-server-library-sweep-refuses-to-flag-when-a-successful-fetch-returns-zero-items-rather-than-nuking-the-whole-library-477) |
 | `sched.auto-tune-foundation` | Auto-tune preview enumeration uses EF distinct+count queries for exact counts, while each created channel is persisted as a live SmartCollection; coexistence with existing channels/numbers is additive-only, never mutating. | 2026-07-16 | [link](../decisions.md#2026-07-16--auto-tuning-enumerates-via-ef-persists-via-smartcollection-additive-coexistence-69) |
 | `sched.autotune-detailpanel-members` | The Auto-Tune DetailPanel's per-channel content-source list is a live `ISearchIndex.Search` roll-up through the server-owned `AutoTuneAxisMap.GenerateQuery`, not an EF distinct+count query, so the preview matches exactly what the built channel's SmartCollection will contain. | 2026-07-17 | [link](../decisions.md#2026-07-17--auto-tune-detailpanel-member-list--live-search-index-roll-up-not-ef-enumeration-384) |

docs/decisions/archive/scan.md

@@ -0,0 +1,49 @@
+# Archive — library scanning / media-server reconciliation
+
+Superseded/retired records for the media-server library scanners and their reconciliation
+strategies. See `docs/decisions/archive/README.md` for the archive's general rules (rationale kept
+verbatim, never in the active read-path). Active successor for music-video reconciliation:
+`scan.musicvideo-server-identity` in `docs/decisions.md`.
+
+---
+
+## 2026-07-20 — `JellyfinMusicVideoLibraryScanner` reconciles by library-scoped path diff + hard delete, not server itemId soft-trash (#494)
+`key: scan.musicvideo-reconciliation` · `status: superseded` · `since: 2026-07-20` · `supersedes: none` · `superseded-by: scan.musicvideo-server-identity@2026-07-25`
+**Rule:** (superseded) `JellyfinMusicVideoLibraryScanner` reconciles removed music videos by a library-scoped local-path diff plus hard delete (`TrashMissingMusicVideos`), not the server-itemId soft-trash pattern the other media-server scanners use, because music videos carry no server identity.
+**Signals:** music-video trash sweep, path-based identity, cross-kind safety, path-keyed identity, empty-fetch guard reuse, remove-stale+add-new dedup · paths: `JellyfinMusicVideoLibraryScanner.TrashMissingMusicVideos`, `FindMusicVideoPaths`/`DeleteByPath`, `IMusicVideoRepository`, `MediaServerReconciliationGuard` · issues: #494, #477, #488, #496, #500
+**Mechanics:** `ScanLibrary_Should_Not_CrossDelete_Movie_Or_Show_Sharing_The_LibraryPath`; `ScanLibrary_Should_Not_Sweep_When_Jellyfin_Returns_Zero_Items`; integration tests extending the #488 harness. #500 — when mirroring the remove-stale + add-new idiom, dedup the incoming set on **the same key its add filter compares** (the filter is materialized before the loop mutates `existing`, so duplicates both pass): `Name`, `Guid` for guids, and for Plex `Actors` an artwork-preferring dedup shared with the remove filter (whose key is `(Name, artwork-presence)`). Remaining un-deduped copies of the idiom: #600. Superseded by `scan.musicvideo-server-identity` (ersatztv#496): music videos gained a `JellyfinMusicVideo` ItemId/Etag identity, so the path diff + hard delete became an itemId diff + soft `FileNotFound` trash.
+
+The Jellyfin music-video scanner did add/update only — a music video removed on the Jellyfin side lingered in
+ErsatzTV forever and could still be scheduled. It now runs a trash sweep at the end of `ScanLibrary`
+(`TrashMissingMusicVideos`), mirroring the `MediaServer{Movie,Television,OtherVideo}LibraryScanner` "gone
+upstream ⇒ remove" pattern but with a deliberately different identity function, because music videos lack the
+media-server identity those base scanners rely on.
+
+- **Identity is (LibraryPathId, path), not server itemId.** The base scanners diff `GetExisting*` (keyed by
+  `MediaServerItemId`) against the incoming server item ids, then soft-trash via `FlagFileNotFound`. Music videos
+  have **no `JellyfinMusicVideo` entity and no `ItemId`/`Etag`** — the scanner is a standalone
+  `IJellyfinMusicVideoLibraryScanner` that injects the *local* `IMusicVideoRepository`, which offers no
+  itemId-keyed existing-set or flag seam. So the sweep diffs the **local path** set instead: existing =
+  `FindMusicVideoPaths(libraryPath)` `.Except` the incoming items' replaced local paths, then hard-deletes the
+  remainder with `DeleteByPath` + `IScannerProxy.RemoveMediaItems`, and cleans now-empty artists with
+  `IArtistRepository.DeleteEmptyArtists`. Hard delete (not soft `FileNotFound` trash) because there is no
+  per-item FileNotFound seam on this path and the issue's Done-when is "removed".
+- **Cross-kind safety is a property of the queries, not the media kind.** `MediaItem` is TPT with `LibraryPathId`
+  on the abstract base, so a Movie, Show and MusicVideo can share one `LibraryPath` (a mixed Jellyfin library).
+  Both `FindMusicVideoPaths` and `DeleteByPath` filter `LibraryPathId` **and** join the concrete `MusicVideo`
+  table, so the sweep can only ever see/delete music videos — a Movie/Show under the same `LibraryPath` is
+  invisible to it. Pinned by `ScanLibrary_Should_Not_CrossDelete_Movie_Or_Show_Sharing_The_LibraryPath`.
+- **Reuses the #477 empty-fetch guard.** The sweep is gated by `MediaServerReconciliationGuard.ShouldFlagMissing`
+  — a successful fetch that returns zero items (server mid-restore / transient) is indistinguishable from a real
+  emptying, so the whole-library wipe is refused and logged. Pinned as a negative control by
+  `ScanLibrary_Should_Not_Sweep_When_Jellyfin_Returns_Zero_Items` (removing the guard flips it red).
+- **Known limitation (deferred to per-library identity).** `MusicVideoRepository.GetOrAdd` dedups a path
+  **globally** (no `LibraryPathId` predicate), so a file served by two libraries with overlapping local paths is
+  a single row owned by whichever library scanned it first. If that owner later stops reporting the file while
+  another library still serves it, this sweep removes the shared row. A proper fix needs per-library music-video
+  identity (a `JellyfinMusicVideo` etag entity + migration) — the issue's "option 2 / fold into the base
+  scanner" refactor — tracked as #496.
+- **Tests.** Integration tests (real `ArtistRepository`/`MusicVideoRepository`/`LibraryRepository` over in-memory
+  SQLite, extending the #488 harness) pin removal, empty-artist cleanup, cross-kind safety, and the empty-fetch
+  guard. Proven non-vacuous: all four fail against the pre-fix scanner except the guard control, which only
+  earns its keep once the sweep exists.