Remove YouTube integration from backend and deployment config

Drops the YouTube-backed second catalog source entirely: the
Local/External split on Track/Album collapses into single concrete
entities, Artist/TrackArtist/ExternalTrack/ExternalAlbum and the
YouTube service/download pipeline (yt-dlp, MassTransit consumer,
routing slip) are deleted, and mixes now source discovery only from
local listening history. Includes the RemoveYouTubeIntegration EF
Core migration and matching Worker/deploy/compose cleanup (no more
yt-dlp/python/deno in the Worker image, no thumbnail-cache/YtDlp
config sections).

backend/Core/Musify.Application/Albums/AddTrackToAlbum.cs

@@ -17,7 +17,7 @@ namespace Musify.Application.Albums
     {
         public async ValueTask<ErrorOr<Success>> Handle(AddTrackToAlbumCommand request, CancellationToken cancellationToken)
         {
-            var album = await database.UserAlbums
+            var album = await database.Albums
                 .AsNoTracking()
                 .SingleOrDefaultAsync(a => a.Id == request.AlbumId, cancellationToken);
             if (album is null)
@@ -32,19 +32,16 @@ namespace Musify.Application.Albums
                 return Error.Unauthorized();
             }
 
-            var trackExists = await database.Tracks
+            var track = await database.Tracks
                 .AsNoTracking()
-                .AnyAsync(t => t.Id == request.TrackId, cancellationToken);
-            if (!trackExists)
+                .SingleOrDefaultAsync(t => t.Id == request.TrackId, cancellationToken);
+            if (track is null)
             {
                 logger.LogInformation("Track {TrackId} not found", request.TrackId);
                 return Error.NotFound(description: $"Track {request.TrackId} not found");
             }
 
-            var localTrack = await database.LocalTracks
-                .AsNoTracking()
-                .SingleOrDefaultAsync(t => t.Id == request.TrackId, cancellationToken);
-            if (localTrack is not null && localTrack.OwnerUserId != request.UserId)
+            if (track.OwnerUserId != request.UserId)
             {
                 logger.LogWarning("User {UserId} does not own track {TrackId}", request.UserId, request.TrackId);
                 return Error.Unauthorized();

backend/Core/Musify.Application/Albums/CreateAlbum.cs

@@ -50,7 +50,7 @@ namespace Musify.Application.Albums
             var intent = pictureIntent.Value;
             var title = request.Title.Trim();
 
-            var album = new UserAlbum
+            var album = new Album
             {
                 OwnerUserId = request.UserId,
                 Title = title,
@@ -66,7 +66,7 @@ namespace Musify.Application.Albums
                 }
             };
 
-            await database.UserAlbums.AddAsync(album, cancellationToken);
+            await database.Albums.AddAsync(album, cancellationToken);
 
             var finalPictureKey = albumConfiguration.Routes.BuildOriginalPicturePath(request.UserId, intent.ObjectName);
             var publishResult = await PublishCreateAlbumEventAsync(album.Id, intent, finalPictureKey, cancellationToken);

backend/Core/Musify.Application/Albums/DeleteAlbum.cs

@@ -16,7 +16,7 @@ namespace Musify.Application.Albums
     {
         public async ValueTask<ErrorOr<Success>> Handle(DeleteAlbumCommand request, CancellationToken cancellationToken)
         {
-            var album = await database.UserAlbums
+            var album = await database.Albums
                 .SingleOrDefaultAsync(a => a.Id == request.AlbumId, cancellationToken);
             if (album is null)
             {
@@ -30,7 +30,7 @@ namespace Musify.Application.Albums
                 return Error.Unauthorized();
             }
 
-            database.UserAlbums.Remove(album);
+            database.Albums.Remove(album);
 
             try
             {

backend/Core/Musify.Application/Albums/GetAlbumById.cs

@@ -14,7 +14,7 @@ namespace Musify.Application.Albums
     {
         public async ValueTask<ErrorOr<AlbumApplicationResponse>> Handle(GetAlbumByIdQuery request, CancellationToken cancellationToken)
         {
-            var album = await database.UserAlbums
+            var album = await database.Albums
                 .AsNoTracking()
                 .Where(a => a.Id == request.Id)
                 .Select(a => new

backend/Core/Musify.Application/Albums/GetAlbumTracks.cs

@@ -4,7 +4,6 @@ using Microsoft.EntityFrameworkCore;
 using Musify.Application.Contracts;
 using Musify.Application.Shared;
 using Musify.Application.Tracks.Responses;
-using Musify.Domain.Entities;
 using X.PagedList;
 using X.PagedList.EF;
 
@@ -29,9 +28,7 @@ namespace Musify.Application.Albums
 
             var tracksQuery = database.AlbumHasTracks
                 .AsNoTracking()
-                .Include(albumTrack => ((ExternalTrack)albumTrack.Track).TrackArtists)
-                    .ThenInclude(trackArtist => trackArtist.Artist)
-                .Include(albumTrack => ((LocalTrack)albumTrack.Track).Owner)
+                .Include(albumTrack => albumTrack.Track.Owner)
                 .Where(albumTrack => albumTrack.AlbumId == request.AlbumId);
 
             var totalCount = await tracksQuery.CountAsync(cancellationToken);

backend/Core/Musify.Application/Albums/GetAlbums.cs

@@ -1,29 +1,19 @@
 using ErrorOr;
 using Mediator;
 using Microsoft.EntityFrameworkCore;
-using Microsoft.Extensions.Logging;
 using Musify.Application.Albums.Responses;
 using Musify.Application.Contracts;
-using Musify.Domain.Entities;
-using Musify.Domain.ValueObjects;
 using X.PagedList;
 using X.PagedList.EF;
 
 namespace Musify.Application.Albums
 {
-    public record GetAlbumsQuery(string? Title, int PageNumber, int PageSize, string? YoutubeContinuationToken = null)
+    public record GetAlbumsQuery(string? Title, int PageNumber, int PageSize)
         : IQuery<ErrorOr<AlbumsSearchResponse>>;
 
-    public class GetAlbumsQueryHandler(
-        IDatabase database,
-        IYouTubeMusicService youTubeMusicService,
-        ILogger<GetAlbumsQueryHandler> logger)
+    public class GetAlbumsQueryHandler(IDatabase database)
         : IQueryHandler<GetAlbumsQuery, ErrorOr<AlbumsSearchResponse>>
     {
-        // Mirrors GetTracksQueryHandler's threshold: a title shorter than this is too likely to
-        // still be mid-keystroke to justify a live call to the external search API.
-        private const int MinTitleLengthForYouTubeSearch = 2;
-
         public async ValueTask<ErrorOr<AlbumsSearchResponse>> Handle(GetAlbumsQuery request, CancellationToken cancellationToken)
         {
             var albumsQuery = database.Albums
@@ -52,62 +42,19 @@ namespace Musify.Application.Albums
                 })
                 .ToPagedListAsync(request.PageNumber, request.PageSize, totalCount, cancellationToken);
 
-            var localItems = pagedEntities
+            var items = pagedEntities
                 .Select(entry => AlbumSearchItemResponse.FromAlbum(
                     AlbumApplicationResponse.FromEntity(entry.Album, entry.TrackCount, entry.CoverTrackIds)))
                 .ToList();
 
-            var knownExternalIds = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
-            foreach (var entry in pagedEntities)
-            {
-                if (entry.Album is ExternalAlbum { Source: TrackSource.YouTube } external)
-                    knownExternalIds.Add(external.ExternalId);
-            }
-
-            var youtubeItems = new List<AlbumSearchItemResponse>();
-            string? nextContinuationToken = null;
-            var youtubeUnavailable = false;
-
-            if (request.Title?.Trim().Length >= MinTitleLengthForYouTubeSearch)
-                (youtubeItems, nextContinuationToken, youtubeUnavailable) =
-                    await SearchYouTubeAsync(request.Title, request.YoutubeContinuationToken, knownExternalIds, cancellationToken);
-
-            return AlbumsSearchResponse.Create(
-                [.. localItems, .. youtubeItems],
+            return new AlbumsSearchResponse(
+                items,
                 pagedEntities.PageNumber,
                 pagedEntities.PageSize,
                 pagedEntities.PageCount,
                 pagedEntities.TotalItemCount,
                 pagedEntities.HasPreviousPage,
-                pagedEntities.HasNextPage,
-                nextContinuationToken,
-                youtubeUnavailable);
-        }
-
-        private async Task<(List<AlbumSearchItemResponse> Items, string? NextContinuationToken, bool Unavailable)> SearchYouTubeAsync(
-            string title,
-            string? continuationToken,
-            HashSet<string> knownExternalIds,
-            CancellationToken cancellationToken)
-        {
-            var searchResult = await youTubeMusicService.SearchAlbumsAsync(title, continuationToken ?? string.Empty, cancellationToken);
-            if (searchResult.IsError)
-            {
-                logger.LogInformation(
-                    "YouTube album search unavailable while combining album results: {Error}", searchResult.FirstError.Description);
-                return ([], null, true);
-            }
-
-            var items = searchResult.Value.Items
-                .Where(album => knownExternalIds.Add(album.AlbumId))
-                .Select(AlbumSearchItemResponse.FromYouTubeAlbum)
-                .ToList();
-
-            var nextToken = string.IsNullOrEmpty(searchResult.Value.ContinuationToken)
-                ? null
-                : searchResult.Value.ContinuationToken;
-
-            return (items, nextToken, false);
+                pagedEntities.HasNextPage);
         }
     }
 }

backend/Core/Musify.Application/Albums/GetAlbumsByUserId.cs

@@ -23,7 +23,7 @@ namespace Musify.Application.Albums
             if (!userExists)
                 return Error.NotFound(description: $"User {request.UserId} not found");
 
-            var albumsQuery = database.UserAlbums
+            var albumsQuery = database.Albums
                 .AsNoTracking()
                 .Where(album => album.OwnerUserId == request.UserId);
 

backend/Core/Musify.Application/Albums/RemoveTrackFromAlbum.cs

@@ -16,7 +16,7 @@ namespace Musify.Application.Albums
     {
         public async ValueTask<ErrorOr<Success>> Handle(RemoveTrackFromAlbumCommand request, CancellationToken cancellationToken)
         {
-            var album = await database.UserAlbums
+            var album = await database.Albums
                 .AsNoTracking()
                 .SingleOrDefaultAsync(a => a.Id == request.AlbumId, cancellationToken);
             if (album is null)

backend/Core/Musify.Application/Albums/Responses/AlbumApplicationResponse.cs

@@ -4,15 +4,6 @@ using Musify.Application.Serialization;
 
 namespace Musify.Application.Albums.Responses
 {
-    // [JsonPolymorphic]/[JsonDerivedType] are required here, not optional: without them
-    // System.Text.Json serializes strictly by the declared CLR type at each call site
-    // (AlbumApplicationResponse, both as a bare return type and nested inside
-    // AlbumSearchItemResponse.Album), so an ExternalAlbumApplicationResponse instance would
-    // silently lose ExternalId/ThumbnailUrl on the wire. This also gives every response a
-    // "source" discriminator field for free, matching AlbumSearchItemResponse.Source.
-    [JsonPolymorphic(TypeDiscriminatorPropertyName = "source")]
-    [JsonDerivedType(typeof(AlbumApplicationResponse), typeDiscriminator: "Local")]
-    [JsonDerivedType(typeof(ExternalAlbumApplicationResponse), typeDiscriminator: "YouTube")]
     public record AlbumApplicationResponse(
         Guid Id,
         string Title,
@@ -30,7 +21,7 @@ namespace Musify.Application.Albums.Responses
         public const int CoverTrackCount = 4;
 
         public static AlbumApplicationResponse FromEntity(
-            UserAlbum album,
+            Album album,
             int trackCount,
             IReadOnlyList<Guid>? coverTrackIds = null)
         {
@@ -48,18 +39,5 @@ namespace Musify.Application.Albums.Responses
                 album.UpdatedAt,
                 coverTrackIds ?? []);
         }
-
-        public static AlbumApplicationResponse FromEntity(
-            Album album,
-            int trackCount,
-            IReadOnlyList<Guid>? coverTrackIds = null)
-        {
-            return album switch
-            {
-                ExternalAlbum externalAlbum => ExternalAlbumApplicationResponse.FromEntity(externalAlbum, trackCount, coverTrackIds),
-                UserAlbum userAlbum => FromEntity(userAlbum, trackCount, coverTrackIds),
-                _ => throw new NotSupportedException($"Unsupported album entity type '{album.GetType().Name}'.")
-            };
-        }
     }
 }

backend/Core/Musify.Application/Albums/Responses/AlbumSearchItemResponse.cs

@@ -1,22 +1,7 @@
-using Musify.Application.Contracts;
-using Musify.Domain.ValueObjects;
-
 namespace Musify.Application.Albums.Responses
 {
-    /// <summary>One item of a combined local/external album listing. Exactly one of
-    /// <see cref="Album"/> or <see cref="YouTubeAlbum"/> is populated: <see cref="Album"/> for
-    /// anything already in the catalog (locally created albums and external albums materialized
-    /// earlier), <see cref="YouTubeAlbum"/> for a live external search hit that hasn't been
-    /// materialized yet, so it has no album id.</summary>
-    public record AlbumSearchItemResponse(
-        TrackSource Source,
-        AlbumApplicationResponse? Album,
-        YouTubeAlbumResult? YouTubeAlbum)
+    public record AlbumSearchItemResponse(AlbumApplicationResponse Album)
     {
-        public static AlbumSearchItemResponse FromAlbum(AlbumApplicationResponse album) =>
-            new(album is ExternalAlbumApplicationResponse ? TrackSource.YouTube : TrackSource.Local, album, null);
-
-        public static AlbumSearchItemResponse FromYouTubeAlbum(YouTubeAlbumResult album) =>
-            new(TrackSource.YouTube, null, album);
+        public static AlbumSearchItemResponse FromAlbum(AlbumApplicationResponse album) => new(album);
     }
 }

backend/Core/Musify.Application/Albums/Responses/AlbumsSearchResponse.cs

@@ -1,11 +1,6 @@
 namespace Musify.Application.Albums.Responses
 {
-    /// <summary>Result of a combined albums listing/search: a page of local catalog albums
-    /// (user-created and previously materialized external albums), plus, when a search term was
-    /// given, live external hits appended after them. Pagination metadata (<see cref="PageNumber"/>,
-    /// <see cref="PageSize"/>, <see cref="PageCount"/>, <see cref="TotalItemCount"/>) describes only
-    /// the local page — the external source has no stable total, so its continuation is tracked
-    /// separately via <see cref="NextYoutubeContinuationToken"/>.</summary>
+    /// <summary>A page of the user's catalog albums (their own).</summary>
     public record AlbumsSearchResponse(
         IReadOnlyList<AlbumSearchItemResponse> Items,
         int PageNumber,
@@ -13,26 +8,5 @@ namespace Musify.Application.Albums.Responses
         int PageCount,
         int TotalItemCount,
         bool HasPreviousPage,
-        bool HasNextLocalPage,
-        string? NextYoutubeContinuationToken,
-        bool YoutubeUnavailable,
-        bool HasNextPage)
-    {
-        // HasNextPage is a real field (not a computed property) so it shows up as a required member
-        // of the generated OpenAPI schema, same as every other field here — a get-only property added
-        // outside the primary constructor gets reflected as optional instead, which is never true here.
-        public static AlbumsSearchResponse Create(
-            IReadOnlyList<AlbumSearchItemResponse> items,
-            int pageNumber,
-            int pageSize,
-            int pageCount,
-            int totalItemCount,
-            bool hasPreviousPage,
-            bool hasNextLocalPage,
-            string? nextYoutubeContinuationToken,
-            bool youtubeUnavailable) =>
-            new(items, pageNumber, pageSize, pageCount, totalItemCount, hasPreviousPage, hasNextLocalPage,
-                nextYoutubeContinuationToken, youtubeUnavailable,
-                HasNextPage: hasNextLocalPage || !string.IsNullOrEmpty(nextYoutubeContinuationToken));
-    }
+        bool HasNextPage);
 }

backend/Core/Musify.Application/Albums/Responses/ExternalAlbumApplicationResponse.cs

@@ -1,47 +0,0 @@
-using Musify.Domain.Entities;
-
-namespace Musify.Application.Albums.Responses
-{
-    public record ExternalAlbumApplicationResponse(
-        Guid Id,
-        string Title,
-        string? Description,
-        int? ReleaseYear,
-        long OwnerUserId,
-        int TrackCount,
-        string? SmallImageKeyName,
-        string? MediumImageKeyName,
-        string? LargeImageKeyName,
-        DateTime CreatedAt,
-        DateTime UpdatedAt,
-        IReadOnlyList<Guid> CoverTrackIds,
-        string ExternalId,
-        string? ThumbnailUrl)
-        : AlbumApplicationResponse(
-            Id, Title, Description, ReleaseYear, OwnerUserId, TrackCount,
-            SmallImageKeyName, MediumImageKeyName, LargeImageKeyName,
-            CreatedAt, UpdatedAt, CoverTrackIds)
-    {
-        public static ExternalAlbumApplicationResponse FromEntity(
-            ExternalAlbum album,
-            int trackCount,
-            IReadOnlyList<Guid>? coverTrackIds = null)
-        {
-            return new ExternalAlbumApplicationResponse(
-                album.Id,
-                album.Title,
-                album.Description,
-                album.ReleaseYear,
-                0,
-                trackCount,
-                album.Pictures?.SmallName,
-                album.Pictures?.MediumName,
-                album.Pictures?.LargeName,
-                album.CreatedAt,
-                album.UpdatedAt,
-                coverTrackIds ?? [],
-                album.ExternalId,
-                album.ThumbnailUrl);
-        }
-    }
-}

backend/Core/Musify.Application/Albums/UpdateAlbum.cs

@@ -34,7 +34,7 @@ namespace Musify.Application.Albums
     {
         public async ValueTask<ErrorOr<AlbumApplicationResponse>> Handle(UpdateAlbumCommand request, CancellationToken cancellationToken)
         {
-            var album = await database.UserAlbums
+            var album = await database.Albums
                 .SingleOrDefaultAsync(a => a.Id == request.AlbumId, cancellationToken);
             if (album is null)
             {
@@ -77,7 +77,7 @@ namespace Musify.Application.Albums
                 finalPictureKey = albumConfiguration.Routes.BuildOriginalPicturePath(request.UserId, pictureIntent.ObjectName);
             }
 
-            database.UserAlbums.Update(album);
+            database.Albums.Update(album);
 
             if (pictureIntent != null && finalPictureKey != null)
             {

backend/Core/Musify.Application/ApplicationDependencyInjection.cs

@@ -12,7 +12,6 @@ public static class ApplicationDependencyInjection
         services.AddMediator();
         services.AddScoped<UploadIntentValidator>();
         services.AddScoped<TrackStreamIssuer>();
-        services.AddScoped<YouTubeTrackProvisioner>();
 
         services.AddValidatedOptions<ApplicationStorageConfiguration>(configuration, ApplicationStorageConfiguration.SectionName);
         services.AddValidatedOptions<PlayListConfiguration>(configuration, PlayListConfiguration.SectionName);

backend/Core/Musify.Application/Configuration/MixConfiguration.cs

@@ -6,16 +6,7 @@ namespace Musify.Application.Configuration
     {
         public const string SectionName = "Mix";
 
-        [Range(1, 20)]
-        public int ArtistMixCount { get; set; } = 3;
-
         [Range(4, 100)]
         public int ItemsPerMix { get; set; } = 12;
-
-        [Range(1, 10)]
-        public int SeedArtistCount { get; set; } = 3;
-
-        [Range(1, 100)]
-        public int YouTubeResultsPerSeed { get; set; } = 12;
     }
 }

backend/Core/Musify.Application/Contracts/IDatabase.cs

@@ -11,22 +11,10 @@ namespace Musify.Application.Contracts
 
         DbSet<Album> Albums { get; }
 
-        DbSet<UserAlbum> UserAlbums { get; }
-
-        DbSet<ExternalAlbum> ExternalAlbums { get; }
-
         DbSet<AlbumHasTrack> AlbumHasTracks { get; }
 
         DbSet<Track> Tracks { get; }
 
-        DbSet<LocalTrack> LocalTracks { get; }
-
-        DbSet<ExternalTrack> ExternalTracks { get; }
-
-        DbSet<Artist> Artists { get; }
-
-        DbSet<TrackArtist> TrackArtists { get; }
-
         DbSet<UserHasTrack> UserHasTracks { get; }
 
         DbSet<PlayListHasTrack> PlayListHasTracks { get; }

backend/Core/Musify.Application/Contracts/IYouTubeDownloaderService.cs

@@ -1,9 +0,0 @@
-namespace Musify.Application.Contracts
-{
-    public record YouTubeDownloadResult(int ExitCode, string StandardError);
-
-    public interface IYouTubeDownloaderService
-    {
-        Task<YouTubeDownloadResult> DownloadAudioAsync(string videoId, string destinationFilePath, CancellationToken cancellationToken);
-    }
-}

backend/Core/Musify.Application/Contracts/IYouTubeMusicService.cs

@@ -1,64 +0,0 @@
-using ErrorOr;
-
-namespace Musify.Application.Contracts
-{
-    public record YouTubeArtistRef(string? Id, string Name);
-
-    public record YouTubeSongResult(
-        string VideoId,
-        string Title,
-        string Artist,
-        string Album,
-        int DurationSeconds,
-        string ThumbnailUrl,
-        bool IsExplicit,
-        IReadOnlyList<YouTubeArtistRef> Artists);
-
-    public record YouTubeSearchResult(
-        IReadOnlyList<YouTubeSongResult> Items,
-        string ContinuationToken);
-
-    public record YouTubeAlbumResult(
-        string AlbumId,
-        string Title,
-        string Artist,
-        string ThumbnailUrl,
-        int? ReleaseYear,
-        bool IsSingle,
-        bool IsEp,
-        IReadOnlyList<YouTubeArtistRef> Artists);
-
-    public record YouTubeAlbumSearchResult(
-        IReadOnlyList<YouTubeAlbumResult> Items,
-        string ContinuationToken);
-
-    public record YouTubeAlbumTrack(
-        string VideoId,
-        string Title,
-        int DurationSeconds,
-        int TrackNumber,
-        bool IsExplicit);
-
-    public record YouTubeAlbumDetail(
-        YouTubeAlbumResult Album,
-        string Description,
-        int TotalDurationSeconds,
-        IReadOnlyList<YouTubeAlbumTrack> Tracks);
-
-    public record YouTubeStreamInfo(string Url, int ExpiresInSeconds);
-
-    public interface IYouTubeMusicService
-    {
-        Task<ErrorOr<YouTubeSearchResult>> SearchSongsAsync(string query, string continuationToken, CancellationToken cancellationToken);
-
-        Task<ErrorOr<YouTubeAlbumSearchResult>> SearchAlbumsAsync(string query, string continuationToken, CancellationToken cancellationToken);
-
-        Task<ErrorOr<YouTubeAlbumDetail>> GetAlbumAsync(string albumId, CancellationToken cancellationToken);
-
-        Task<ErrorOr<YouTubeStreamInfo>> GetAudioStreamAsync(string videoId, CancellationToken cancellationToken);
-
-        Task<ErrorOr<YouTubeSongResult>> GetSongAsync(string videoId, CancellationToken cancellationToken);
-
-        string ResolveArtworkUrl(string thumbnailUrl);
-    }
-}

backend/Core/Musify.Application/Events/DownloadYouTubeTrackEvent.cs

@@ -1,14 +0,0 @@
-using Musify.Application.Shared;
-
-namespace Musify.Application.Events
-{
-    public record DownloadYouTubeTrackEvent(
-        Guid TrackId,
-        string VideoId,
-        string ThumbnailUrl,
-        string Bucket,
-        string AudioProcessedFolderKey,
-        ImageSize Small,
-        ImageSize Medium,
-        ImageSize Large);
-}

backend/Core/Musify.Application/Likes/GetLikedTracks.cs

@@ -4,7 +4,6 @@ using Microsoft.EntityFrameworkCore;
 using Musify.Application.Contracts;
 using Musify.Application.Shared;
 using Musify.Application.Tracks.Responses;
-using Musify.Domain.Entities;
 using X.PagedList;
 using X.PagedList.EF;
 
@@ -23,9 +22,7 @@ namespace Musify.Application.Likes
         {
             var likesQuery = database.TrackLikes
                 .AsNoTracking()
-                .Include(like => ((ExternalTrack)like.Track).TrackArtists)
-                    .ThenInclude(trackArtist => trackArtist.Artist)
-                .Include(like => ((LocalTrack)like.Track).Owner)
+                .Include(like => like.Track.Owner)
                 .Where(like => like.UserId == request.UserId);
 
             var totalCount = await likesQuery.CountAsync(cancellationToken);

backend/Core/Musify.Application/Likes/ToggleTrackLike.cs

@@ -3,35 +3,31 @@ using Mediator;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.Logging;
 using Musify.Application.Contracts;
-using Musify.Application.Services;
 using Musify.Domain.Entities;
-using Musify.Domain.ValueObjects;
 
 namespace Musify.Application.Likes
 {
-    public record ToggleTrackLikeCommand(
-        long UserId,
-        Guid? TrackId,
-        TrackSource? Source,
-        string? ExternalId)
+    public record ToggleTrackLikeCommand(long UserId, Guid TrackId)
         : ICommand<ErrorOr<bool>>;
 
     public class ToggleTrackLikeCommandHandler(
         IDatabase database,
-        YouTubeTrackProvisioner provisioner,
         ILogger<ToggleTrackLikeCommandHandler> logger)
         : ICommandHandler<ToggleTrackLikeCommand, ErrorOr<bool>>
     {
         public async ValueTask<ErrorOr<bool>> Handle(ToggleTrackLikeCommand request, CancellationToken cancellationToken)
         {
-            var trackIdResult = await ResolveTrackIdAsync(request, cancellationToken);
-            if (trackIdResult.IsError)
-                return trackIdResult.Errors;
-
-            var trackId = trackIdResult.Value;
+            var trackExists = await database.Tracks
+                .AsNoTracking()
+                .AnyAsync(t => t.Id == request.TrackId, cancellationToken);
+            if (!trackExists)
+            {
+                logger.LogInformation("Track {TrackId} not found", request.TrackId);
+                return Error.NotFound(description: $"Track {request.TrackId} not found");
+            }
 
             var existingLike = await database.TrackLikes
-                .SingleOrDefaultAsync(like => like.UserId == request.UserId && like.TrackId == trackId, cancellationToken);
+                .SingleOrDefaultAsync(like => like.UserId == request.UserId && like.TrackId == request.TrackId, cancellationToken);
 
             bool nowLiked;
             if (existingLike is not null)
@@ -44,7 +40,7 @@ namespace Musify.Application.Likes
                 await database.TrackLikes.AddAsync(new TrackLike
                 {
                     UserId = request.UserId,
-                    TrackId = trackId
+                    TrackId = request.TrackId
                 }, cancellationToken);
                 nowLiked = true;
             }
@@ -52,32 +48,9 @@ namespace Musify.Application.Likes
             await database.SaveChangesAsync(cancellationToken);
 
             logger.LogInformation("User {UserId} {Action} track {TrackId}",
-                request.UserId, nowLiked ? "liked" : "unliked", trackId);
+                request.UserId, nowLiked ? "liked" : "unliked", request.TrackId);
 
             return nowLiked;
         }
-
-        private async ValueTask<ErrorOr<Guid>> ResolveTrackIdAsync(ToggleTrackLikeCommand request, CancellationToken cancellationToken)
-        {
-            if (request.TrackId.HasValue)
-            {
-                var trackExists = await database.Tracks
-                    .AsNoTracking()
-                    .AnyAsync(t => t.Id == request.TrackId.Value, cancellationToken);
-                if (!trackExists)
-                {
-                    logger.LogInformation("Track {TrackId} not found", request.TrackId);
-                    return Error.NotFound(description: $"Track {request.TrackId} not found");
-                }
-
-                return request.TrackId.Value;
-            }
-
-            var provisionResult = await provisioner.GetOrCreateAsync(request.ExternalId!, cancellationToken);
-            if (provisionResult.IsError)
-                return provisionResult.Errors;
-
-            return provisionResult.Value.Track.Id;
-        }
     }
 }

backend/Core/Musify.Application/Mixes/GenerateMixesForUser.cs

@@ -4,7 +4,6 @@ using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.Logging;
 using Musify.Application.Configuration;
 using Musify.Application.Contracts;
-using Musify.Application.Tracks.Responses;
 using Musify.Domain.Entities;
 using Musify.Domain.ValueObjects;
 
@@ -13,28 +12,35 @@ namespace Musify.Application.Mixes
     public record GenerateMixesForUserCommand(long UserId)
         : ICommand<ErrorOr<Success>>;
 
+    /// <summary>Builds each user's mixes purely from their own library: a "Descubrimiento" mix of
+    /// tracks they own but haven't listened to yet, and a "Tu mezcla diaria" mix blending recently
+    /// listened tracks with unheard ones. There's no artist/genre metadata for local uploads today,
+    /// so mixes can't be seeded by "similar artist" the way the old YouTube-backed discovery did —
+    /// once a tagging system exists, this is the place to seed mixes by tag instead.</summary>
     public class GenerateMixesForUserCommandHandler(
         IDatabase database,
-        IYouTubeMusicService youTubeMusicService,
         MixConfiguration mixConfiguration,
         ILogger<GenerateMixesForUserCommandHandler> logger)
         : ICommandHandler<GenerateMixesForUserCommand, ErrorOr<Success>>
     {
-        private sealed record SeedArtist(Guid Id, string Name);
-
-        private sealed record LocalCandidate(Guid TrackId, string Title, string? Artist, double DurationSeconds);
-
-        private sealed record MixDraft(string Title, string? Subtitle, IReadOnlyList<MixItem> Items);
-
-        private const int TitleLength = 300;
-        private const int ArtistLength = 300;
-        private const int ThumbnailUrlLength = 512;
-        private const int MixTitleLength = 100;
+        private sealed record MixDraft(string Title, string? Subtitle, IReadOnlyList<Guid> TrackIds);
 
         public async ValueTask<ErrorOr<Success>> Handle(GenerateMixesForUserCommand request, CancellationToken cancellationToken)
         {
             var userId = request.UserId;
 
+            var libraryTrackIds = await database.UserHasTracks
+                .AsNoTracking()
+                .Where(userTrack => userTrack.UserId == userId && userTrack.Track.LifeCycleStatus == LifeCycleStatus.Active)
+                .Select(userTrack => userTrack.TrackId)
+                .ToListAsync(cancellationToken);
+
+            if (libraryTrackIds.Count == 0)
+            {
+                logger.LogInformation("User {UserId} has no tracks yet, skipping mix generation", userId);
+                return new Success();
+            }
+
             var historyTrackIds = await database.ListeningHistories
                 .AsNoTracking()
                 .Where(history => history.UserId == userId)
@@ -42,33 +48,29 @@ namespace Musify.Application.Mixes
                 .Distinct()
                 .ToListAsync(cancellationToken);
 
-            if (historyTrackIds.Count == 0)
+            var historySet = new HashSet<Guid>(historyTrackIds);
+            var unheardTrackIds = libraryTrackIds.Where(id => !historySet.Contains(id)).ToList();
+
+            var drafts = new List<MixDraft>();
+
+            var discovery = Take(Shuffle(unheardTrackIds));
+            if (discovery.Count > 0)
             {
-                logger.LogInformation("User {UserId} has no listening history yet, skipping mix generation", userId);
-                return new Success();
+                drafts.Add(new MixDraft(
+                    "Descubrimiento",
+                    "Canciones de tu biblioteca que todavía no has escuchado.",
+                    discovery));
             }
 
-            var seedArtists = await GetSeedArtistsAsync(historyTrackIds, cancellationToken);
-
-            if (seedArtists.Count == 0)
+            var daily = Take(Interleave(Shuffle(historyTrackIds), Shuffle(unheardTrackIds)));
+            if (daily.Count > 0)
             {
-                logger.LogInformation("User {UserId} has no artists to seed mixes from, skipping mix generation", userId);
-                return new Success();
+                drafts.Add(new MixDraft(
+                    "Tu mezcla diaria",
+                    "Lo que más escuchas, con alguna sorpresa de tu biblioteca.",
+                    daily));
             }
 
-            var knownVideoIds = await database.ExternalTracks
-                .AsNoTracking()
-                .Where(track => track.Source == TrackSource.YouTube && historyTrackIds.Contains(track.Id))
-                .Select(track => track.ExternalId)
-                .ToListAsync(cancellationToken);
-
-            var excludedVideoIds = new HashSet<string>(knownVideoIds, StringComparer.OrdinalIgnoreCase);
-
-            var youTubeByArtist = await SearchYouTubeAsync(seedArtists, excludedVideoIds, cancellationToken);
-            var localByArtist = await GetLocalCandidatesAsync(seedArtists, historyTrackIds, cancellationToken);
-
-            var drafts = BuildDrafts(seedArtists, localByArtist, youTubeByArtist);
-
             if (drafts.Count == 0)
             {
                 logger.LogInformation("No candidate songs found for user {UserId}, skipping mix generation", userId);
@@ -91,197 +93,21 @@ namespace Musify.Application.Mixes
             return new Success();
         }
 
-        private async Task<List<SeedArtist>> GetSeedArtistsAsync(
-            IReadOnlyList<Guid> historyTrackIds,
-            CancellationToken cancellationToken)
+        private List<Guid> Take(IEnumerable<Guid> trackIds) =>
+            [.. trackIds.Take(mixConfiguration.ItemsPerMix)];
+
+        private static List<Guid> Shuffle(IEnumerable<Guid> trackIds) =>
+            [.. trackIds.OrderBy(_ => Guid.NewGuid())];
+
+        private static List<Guid> Interleave(IReadOnlyList<Guid> first, IReadOnlyList<Guid> second)
         {
-            var ranked = await database.TrackArtists
-                .AsNoTracking()
-                .Where(trackArtist => historyTrackIds.Contains(trackArtist.TrackId))
-                .GroupBy(trackArtist => trackArtist.ArtistId)
-                .Select(group => new { ArtistId = group.Key, Listens = group.Count() } )
-                .OrderByDescending(entry => entry.Listens)
-                .Take(mixConfiguration.SeedArtistCount)
-                .ToListAsync(cancellationToken);
-
-            var artistIds = ranked.Select(entry => entry.ArtistId).ToList();
-
-            var names = await database.Artists
-                .AsNoTracking()
-                .Where(artist => artistIds.Contains(artist.Id))
-                .ToDictionaryAsync(artist => artist.Id, artist => artist.Name, cancellationToken);
-
-            return [.. ranked
-                .Where(entry => names.ContainsKey(entry.ArtistId))
-                .Select(entry => new SeedArtist(entry.ArtistId, names[entry.ArtistId])) ];
-        }
-
-        private async Task<Dictionary<Guid, List<MixItem>> > SearchYouTubeAsync(
-            IReadOnlyList<SeedArtist> seedArtists,
-            HashSet<string> excludedVideoIds,
-            CancellationToken cancellationToken)
-        {
-            var byArtist = new Dictionary<Guid, List<MixItem>>();
-
-            foreach (var seed in seedArtists)
-            {
-                var searchResult = await youTubeMusicService.SearchSongsAsync(seed.Name, string.Empty, cancellationToken);
-                if (searchResult.IsError)
-                {
-                    logger.LogWarning("YouTube Music search failed for seed artist {Artist}: {Error}",
-                        seed.Name, searchResult.FirstError.Description);
-                    byArtist[seed.Id] = [];
-                    continue;
-                }
-
-                var songs = new List<MixItem>();
-                foreach (var song in searchResult.Value.Items.Take(mixConfiguration.YouTubeResultsPerSeed))
-                {
-                    if (!excludedVideoIds.Add(song.VideoId))
-                        continue;
-
-                    songs.Add(new MixItem
-                    {
-                        MixId = Guid.Empty,
-                        Source = MixItemSource.YouTube,
-                        VideoId = song.VideoId,
-                        Title = Truncate(song.Title, TitleLength),
-                        Artist = Truncate(song.Artist, ArtistLength),
-                        ThumbnailUrl = Truncate(youTubeMusicService.ResolveArtworkUrl(song.ThumbnailUrl), ThumbnailUrlLength),
-                        DurationSeconds = song.DurationSeconds,
-                        IsExplicit = song.IsExplicit
-                    } );
-                }
-
-                byArtist[seed.Id] = songs;
-            }
-
-            return byArtist;
-        }
-
-        private async Task<Dictionary<Guid, List<MixItem>> > GetLocalCandidatesAsync(
-            IReadOnlyList<SeedArtist> seedArtists,
-            IReadOnlyList<Guid> historyTrackIds,
-            CancellationToken cancellationToken)
-        {
-            var artistIds = seedArtists.Select(seed => seed.Id).ToList();
-
-            var links = await database.TrackArtists
-                .AsNoTracking()
-                .Where(trackArtist => artistIds.Contains(trackArtist.ArtistId) && !historyTrackIds.Contains(trackArtist.TrackId))
-                .Select(trackArtist => new { trackArtist.ArtistId, trackArtist.TrackId } )
-                .ToListAsync(cancellationToken);
-
-            var trackIds = links.Select(link => link.TrackId).Distinct().ToList();
-
-            var candidates = await LoadCandidatesAsync(trackIds, cancellationToken);
-
-            var byArtist = new Dictionary<Guid, List<MixItem>>();
-            foreach (var seed in seedArtists)
-            {
-                byArtist[seed.Id] = [.. links
-                    .Where(link => link.ArtistId == seed.Id)
-                    .Select(link => candidates.GetValueOrDefault(link.TrackId))
-                    .Where(candidate => candidate is not null)
-                    .Select(candidate => ToMixItem(candidate!))];
-            }
-
-            return byArtist;
-        }
-
-        private async Task<Dictionary<Guid, LocalCandidate>> LoadCandidatesAsync(
-            IReadOnlyList<Guid> trackIds,
-            CancellationToken cancellationToken)
-        {
-            if (trackIds.Count == 0)
-                return [];
-
-            var tracks = await database.Tracks
-                .AsNoTracking()
-                .Where(track => trackIds.Contains(track.Id) && track.LifeCycleStatus == LifeCycleStatus.Active)
-                .Include(track => ((ExternalTrack)track).TrackArtists)
-                    .ThenInclude(trackArtist => trackArtist.Artist)
-                .Include(track => ((LocalTrack)track).Owner)
-                .ToListAsync(cancellationToken);
-
-            return tracks
-                .Select(track => TrackApplicationResponse.FromEntity(track, 0))
-                .ToDictionary(
-                    response => response.Id,
-                    response => new LocalCandidate(response.Id, response.Title, response.Artist, response.Duration));
-        }
-
-        private static MixItem ToMixItem(LocalCandidate candidate) => new()
-        {
-            MixId = Guid.Empty,
-            Source = MixItemSource.Musify,
-            TrackId = candidate.TrackId,
-            Title = candidate.Title,
-            Artist = candidate.Artist,
-            DurationSeconds = candidate.DurationSeconds
-        };
-
-        private List<MixDraft> BuildDrafts(
-            IReadOnlyList<SeedArtist> seedArtists,
-            IReadOnlyDictionary<Guid, List<MixItem>> localByArtist,
-            IReadOnlyDictionary<Guid, List<MixItem>> youTubeByArtist)
-        {
-            var drafts = new List<MixDraft>();
-
-            var everyYouTube = seedArtists.SelectMany(seed => youTubeByArtist[seed.Id]).ToList();
-            var everyLocal = seedArtists.SelectMany(seed => localByArtist[seed.Id]).ToList();
-
-            var discovery = Take(Shuffle(everyYouTube));
-            if (discovery.Count > 0)
-            {
-                drafts.Add(new MixDraft(
-                    "Descubrimiento",
-                    "Canciones nuevas que todavía no has escuchado.",
-                    discovery));
-            }
-
-            var daily = Take(Interleave(Shuffle(everyLocal), Shuffle(everyYouTube)));
-            if (daily.Count > 0)
-            {
-                drafts.Add(new MixDraft(
-                    "Tu mezcla diaria",
-                    "Lo que más escuchas, con alguna sorpresa nueva.",
-                    daily));
-            }
-
-            foreach (var seed in seedArtists.Take(mixConfiguration.ArtistMixCount))
-            {
-                var items = Take(Interleave(Shuffle(localByArtist[seed.Id]), Shuffle(youTubeByArtist[seed.Id])));
-                if (items.Count == 0)
-                    continue;
-
-                drafts.Add(new MixDraft(
-                    Truncate(seed.Name, MixTitleLength),
-                    $"Canciones de {seed.Name} y de artistas parecidos.",
-                    items));
-            }
-
-            return drafts;
-        }
-
-        private List<MixItem> Take(IEnumerable<MixItem> items) =>
-            [.. items.Take(mixConfiguration.ItemsPerMix)];
-
-        private static string Truncate(string value, int maxLength) =>
-            value.Length <= maxLength ? value : value[..maxLength];
-
-        private static List<MixItem> Shuffle(IEnumerable<MixItem> items) =>
-            [.. items.OrderBy(_ => Guid.NewGuid())];
-
-        private static List<MixItem> Interleave(IReadOnlyList<MixItem> first, IReadOnlyList<MixItem> second)
-        {
-            var merged = new List<MixItem>(first.Count + second.Count);
+            var merged = new List<Guid>(first.Count + second.Count);
             for (var index = 0; index < Math.Max(first.Count, second.Count); index++)
             {
                 if (index < first.Count)
-                    merged.Add(first[index] );
+                    merged.Add(first[index]);
                 if (index < second.Count)
-                    merged.Add(second[index] );
+                    merged.Add(second[index]);
             }
 
             return merged;
@@ -317,21 +143,13 @@ namespace Musify.Application.Mixes
 
                 await database.Mixes.AddAsync(mix, cancellationToken);
 
-                for (var itemPosition = 0; itemPosition < draft.Items.Count; itemPosition++)
+                for (var itemPosition = 0; itemPosition < draft.TrackIds.Count; itemPosition++)
                 {
-                    var item = draft.Items[itemPosition];
                     await database.MixItems.AddAsync(new MixItem
                     {
                         MixId = mix.Id,
                         Position = itemPosition,
-                        Source = item.Source,
-                        TrackId = item.TrackId,
-                        VideoId = item.VideoId,
-                        Title = item.Title,
-                        Artist = item.Artist,
-                        ThumbnailUrl = item.ThumbnailUrl,
-                        DurationSeconds = item.DurationSeconds,
-                        IsExplicit = item.IsExplicit
+                        TrackId = draft.TrackIds[itemPosition]
                     }, cancellationToken);
                 }
             }

backend/Core/Musify.Application/Mixes/GetMixById.cs

@@ -22,9 +22,10 @@ namespace Musify.Application.Mixes
             if (mix is null)
                 return Error.NotFound(description: $"Mix {request.MixId} was not found");
 
-            var items = mix.Items.OrderBy(item => item.Position).ToList();
+            var orderedItems = mix.Items.OrderBy(item => item.Position).ToList();
+            var items = await MixItemMapper.ToResponsesAsync(database, orderedItems, cancellationToken);
 
-            return MixApplicationResponse.FromEntity(mix, items.Count, items);
+            return new MixApplicationResponse(mix.Id, mix.Title, mix.Subtitle, items.Count, items);
         }
     }
 }

backend/Core/Musify.Application/Mixes/GetMixesByUserId.cs

@@ -14,24 +14,24 @@ namespace Musify.Application.Mixes
     {
         public async ValueTask<ErrorOr<IReadOnlyList<MixApplicationResponse>>> Handle(GetMixesByUserIdQuery request, CancellationToken cancellationToken)
         {
-            var entries = await database.Mixes
+            var mixes = await database.Mixes
                 .AsNoTracking()
                 .Where(mix => mix.UserId == request.UserId)
+                .Include(mix => mix.Items)
                 .OrderBy(mix => mix.Position)
-                .Select(mix => new
-                {
-                    Mix = mix,
-                    ItemCount = mix.Items.Count,
-                    CoverItems = mix.Items
-                        .OrderBy(item => item.Position)
-                        .Take(MixApplicationResponse.CoverItemCount)
-                        .ToList()
-                })
                 .ToListAsync(cancellationToken);
 
-            return entries
-                .Select(entry => MixApplicationResponse.FromEntity(entry.Mix, entry.ItemCount, entry.CoverItems))
-                .ToList();
+            var responses = new List<MixApplicationResponse>(mixes.Count);
+            foreach (var mix in mixes)
+            {
+                var orderedItems = mix.Items.OrderBy(item => item.Position).ToList();
+                var coverItems = await MixItemMapper.ToResponsesAsync(
+                    database, orderedItems.Take(MixApplicationResponse.CoverItemCount).ToList(), cancellationToken);
+
+                responses.Add(new MixApplicationResponse(mix.Id, mix.Title, mix.Subtitle, orderedItems.Count, coverItems));
+            }
+
+            return responses;
         }
     }
 }

backend/Core/Musify.Application/Mixes/MixItemMapper.cs

@@ -0,0 +1,36 @@
+using Microsoft.EntityFrameworkCore;
+using Musify.Application.Contracts;
+using Musify.Application.Mixes.Responses;
+using Musify.Domain.Entities;
+
+namespace Musify.Application.Mixes
+{
+    /// <summary>Resolves MixItem rows to their MixItemApplicationResponse shape via a single batched
+    /// track lookup, instead of an EF Include chain deep enough (Mix -&gt; Items -&gt; Track -&gt; Owner) to
+    /// force a correlated-subquery translation some providers (SQLite, notably) can't produce.</summary>
+    internal static class MixItemMapper
+    {
+        public static async Task<List<MixItemApplicationResponse>> ToResponsesAsync(
+            IDatabase database,
+            IReadOnlyList<MixItem> orderedItems,
+            CancellationToken cancellationToken)
+        {
+            var trackIds = orderedItems.Select(item => item.TrackId).Distinct().ToList();
+
+            var tracksById = await database.Tracks
+                .AsNoTracking()
+                .Include(track => track.Owner)
+                .Where(track => trackIds.Contains(track.Id))
+                .ToDictionaryAsync(track => track.Id, cancellationToken);
+
+            return orderedItems
+                .Where(item => tracksById.ContainsKey(item.TrackId))
+                .Select(item =>
+                {
+                    var track = tracksById[item.TrackId];
+                    return new MixItemApplicationResponse(item.TrackId, track.Title, track.Owner.Name, track.DurationSeconds);
+                })
+                .ToList();
+        }
+    }
+}

backend/Core/Musify.Application/Mixes/Responses/MixApplicationResponse.cs

@@ -1,5 +1,3 @@
-using Musify.Domain.Entities;
-
 namespace Musify.Application.Mixes.Responses
 {
     public record MixApplicationResponse(
@@ -10,16 +8,5 @@ namespace Musify.Application.Mixes.Responses
         IReadOnlyList<MixItemApplicationResponse> Items)
     {
         public const int CoverItemCount = 4;
-
-        public static MixApplicationResponse FromEntity(
-            Mix mix,
-            int itemCount,
-            IReadOnlyList<MixItem> items) =>
-            new(
-                mix.Id,
-                mix.Title,
-                mix.Subtitle,
-                itemCount,
-                [.. items.Select(MixItemApplicationResponse.FromEntity)]);
     }
 }

backend/Core/Musify.Application/Mixes/Responses/MixItemApplicationResponse.cs

@@ -1,27 +1,8 @@
-using Musify.Domain.Entities;
-using Musify.Domain.ValueObjects;
-
 namespace Musify.Application.Mixes.Responses
 {
     public record MixItemApplicationResponse(
-        MixItemSource Source,
-        Guid? TrackId,
-        string? VideoId,
+        Guid TrackId,
         string Title,
         string? Artist,
-        string? ThumbnailUrl,
-        double DurationSeconds,
-        bool IsExplicit)
-    {
-        public static MixItemApplicationResponse FromEntity(MixItem item) =>
-            new(
-                item.Source,
-                item.TrackId,
-                item.VideoId,
-                item.Title ?? string.Empty,
-                item.Artist,
-                item.ThumbnailUrl,
-                item.DurationSeconds,
-                item.IsExplicit);
-    }
+        double DurationSeconds);
 }

backend/Core/Musify.Application/PlayLists/AddYouTubeTrackToPlayList.cs

@@ -1,149 +0,0 @@
-using ErrorOr;
-using Mediator;
-using Microsoft.EntityFrameworkCore;
-using Microsoft.Extensions.Logging;
-using Musify.Application.Configuration;
-using Musify.Application.Contracts;
-using Musify.Application.Events;
-using Musify.Application.Services;
-using Musify.Application.Shared;
-using Musify.Application.Tracks.Responses;
-using Musify.Domain.Entities;
-using Musify.Domain.ValueObjects;
-
-namespace Musify.Application.PlayLists
-{
-    public record AddYouTubeTrackToPlayListCommand(
-        long UserId,
-        Guid PlayListId,
-        string VideoId)
-        : ICommand<ErrorOr<TrackApplicationResponse>>;
-
-    public class AddYouTubeTrackToPlayListCommandHandler(
-        IDatabase database,
-        IEventBus eventBus,
-        IYouTubeMusicService youTubeMusicService,
-        YouTubeTrackProvisioner provisioner,
-        ApplicationStorageConfiguration storageConfiguration,
-        TrackConfiguration trackConfiguration,
-        ILogger<AddYouTubeTrackToPlayListCommandHandler> logger)
-        : ICommandHandler<AddYouTubeTrackToPlayListCommand, ErrorOr<TrackApplicationResponse>>
-    {
-        public async ValueTask<ErrorOr<TrackApplicationResponse>> Handle(AddYouTubeTrackToPlayListCommand request, CancellationToken cancellationToken)
-        {
-            var playList = await database.PlayLists.AsNoTracking()
-                .SingleOrDefaultAsync(pl => pl.Id == request.PlayListId, cancellationToken);
-            if (playList is null)
-            {
-                logger.LogInformation("Playlist {PlayListId} not found", request.PlayListId);
-                return Error.NotFound();
-            }
-
-            if (playList.UserId != request.UserId)
-            {
-                logger.LogWarning("User {UserId} is not the owner of playlist {PlayListId}", request.UserId, request.PlayListId);
-                return Error.Unauthorized();
-            }
-
-            var provisionResult = await provisioner.GetOrCreateAsync(request.VideoId, cancellationToken);
-            if (provisionResult.IsError)
-                return provisionResult.Errors;
-
-            var track = provisionResult.Value.Track;
-
-            var failed = track.Audio.IsFailed;
-            var neverQueued = !track.Audio.DownloadRequested && !track.Audio.IsProcessed;
-            if (failed || neverQueued)
-            {
-                if (failed)
-                {
-                    track.Audio.TranscodeStatus = ProcessingStatus.Pending;
-                    track.Pictures.ProcessingStatus = ProcessingStatus.Pending;
-                    track.LifeCycleStatus = LifeCycleStatus.Active;
-                    track.Audio.RetryCount += 1;
-                    track.Audio.LastRetryAt = DateTime.UtcNow;
-                }
-                track.Audio.DownloadRequested = true;
-
-                var thumbnailUrl = await ResolveThumbnailUrlAsync(request.VideoId, provisionResult.Value.Song, cancellationToken);
-                if (thumbnailUrl.IsError)
-                    return thumbnailUrl.Errors;
-
-                await PublishDownloadEventAsync(track.Id, request.VideoId, thumbnailUrl.Value, cancellationToken);
-                await database.SaveChangesAsync(cancellationToken);
-                logger.LogInformation("Queued YouTube track {VideoId} for download", request.VideoId);
-            }
-
-            var alreadyAdded = await database.PlayListHasTracks.AsNoTracking()
-                .AnyAsync(plt => plt.PlayListId == request.PlayListId && plt.TrackId == track.Id, cancellationToken);
-            if (alreadyAdded)
-            {
-                logger.LogInformation("Track {TrackId} already in playlist {PlayListId}", track.Id, request.PlayListId);
-                return Error.Conflict(description: "Track is already in the playlist.");
-            }
-
-            var playListTracksQuery = database.PlayListHasTracks
-                .Where(plt => plt.PlayListId == request.PlayListId);
-
-            var hasTracks = await playListTracksQuery.AnyAsync(cancellationToken);
-            var nextPosition = hasTracks
-                ? await playListTracksQuery.MaxAsync(plt => plt.Position, cancellationToken) + 1
-                : 0;
-
-            await database.PlayListHasTracks.AddAsync(new PlayListHasTrack
-            {
-                PlayListId = request.PlayListId,
-                TrackId = track.Id,
-                Position = nextPosition
-            }, cancellationToken);
-
-            await database.SaveChangesAsync(cancellationToken);
-
-            logger.LogInformation("Added YouTube track {VideoId} ({TrackId}) to playlist {PlayListId} at position {Position}",
-                request.VideoId, track.Id, request.PlayListId, nextPosition);
-
-            var listensCount = await database.ListeningHistories.AsNoTracking()
-                .CountAsync(lh => lh.TrackId == track.Id, cancellationToken);
-
-            return TrackApplicationResponse.FromEntity(track, listensCount);
-        }
-
-        private async Task<ErrorOr<string>> ResolveThumbnailUrlAsync(string videoId, YouTubeSongResult? song, CancellationToken cancellationToken)
-        {
-            if (!string.IsNullOrEmpty(song?.ThumbnailUrl))
-                return youTubeMusicService.ResolveArtworkUrl(song.ThumbnailUrl);
-
-            var songResult = await youTubeMusicService.GetSongAsync(videoId, cancellationToken);
-            if (songResult.IsError)
-                return songResult.Errors;
-
-            return youTubeMusicService.ResolveArtworkUrl(songResult.Value.ThumbnailUrl);
-        }
-
-        private async Task PublishDownloadEventAsync(Guid trackId, string videoId, string thumbnailUrl, CancellationToken cancellationToken)
-        {
-            var audioProcessedFolderKey = trackConfiguration.Routes.BuildProcessedAudioPath(Guid.NewGuid().ToString());
-
-            await eventBus.PublishAsync(
-                new DownloadYouTubeTrackEvent(
-                    trackId,
-                    videoId,
-                    thumbnailUrl,
-                    storageConfiguration.Bucket,
-                    audioProcessedFolderKey,
-                    new ImageSize(
-                        trackConfiguration.Routes.SmallPicturesPath,
-                        trackConfiguration.PicturesSizes.SmallPictureWidth,
-                        trackConfiguration.PicturesSizes.SmallPictureHeight),
-                    new ImageSize(
-                        trackConfiguration.Routes.MediumPicturesPath,
-                        trackConfiguration.PicturesSizes.MediumPictureWidth,
-                        trackConfiguration.PicturesSizes.MediumPictureHeight),
-                    new ImageSize(
-                        trackConfiguration.Routes.LargePicturesPath,
-                        trackConfiguration.PicturesSizes.LargePictureWidth,
-                        trackConfiguration.PicturesSizes.LargePictureHeight)),
-                cancellationToken);
-        }
-    }
-}

backend/Core/Musify.Application/PlayLists/GetPlayListTracks.cs

@@ -4,7 +4,6 @@ using Microsoft.EntityFrameworkCore;
 using Musify.Application.Contracts;
 using Musify.Application.Shared;
 using Musify.Application.Tracks.Responses;
-using Musify.Domain.Entities;
 using X.PagedList;
 using X.PagedList.EF;
 
@@ -29,9 +28,7 @@ namespace Musify.Application.PlayLists
 
             var tracksQuery = database.PlayListHasTracks
                 .AsNoTracking()
-                .Include(plt => ((ExternalTrack)plt.Track).TrackArtists)
-                    .ThenInclude(trackArtist => trackArtist.Artist)
-                .Include(plt => ((LocalTrack)plt.Track).Owner)
+                .Include(plt => plt.Track.Owner)
                 .Where(plt => plt.PlayListId == request.PlayListId);
 
             var totalCount = await tracksQuery.CountAsync(cancellationToken);

backend/Core/Musify.Application/Services/YouTubeTrackProvisioner.cs

@@ -1,265 +0,0 @@
-using ErrorOr;
-using Microsoft.EntityFrameworkCore;
-using Microsoft.Extensions.Logging;
-using Musify.Application.Configuration;
-using Musify.Application.Contracts;
-using Musify.Domain.Entities;
-using Musify.Domain.ValueObjects;
-
-namespace Musify.Application.Services;
-
-public sealed record YouTubeTrackProvision(ExternalTrack Track, YouTubeSongResult? Song);
-
-public sealed class YouTubeTrackProvisioner(
-    IDatabase database,
-    IYouTubeMusicService youTubeMusicService,
-    TrackConfiguration trackConfiguration,
-    ILogger<YouTubeTrackProvisioner> logger)
-{
-    public Task<ExternalTrack?> FindAsync(string videoId, CancellationToken cancellationToken) =>
-        database.ExternalTracks
-            .Include(track => track.TrackArtists)
-            .ThenInclude(trackArtist => trackArtist.Artist)
-            .SingleOrDefaultAsync(t => t.Source == TrackSource.YouTube && t.ExternalId == videoId, cancellationToken);
-
-    public async Task<ErrorOr<YouTubeTrackProvision>> GetOrCreateAsync(string videoId, CancellationToken cancellationToken)
-    {
-        var existing = await FindAsync(videoId, cancellationToken);
-        if (existing is not null)
-            return new YouTubeTrackProvision(existing, Song: null);
-
-        var songResult = await youTubeMusicService.GetSongAsync(videoId, cancellationToken);
-        if (songResult.IsError)
-            return songResult.Errors;
-
-        var song = songResult.Value;
-
-        var artistRefs = song.Artists
-            .GroupBy(artistRef => artistRef.Id ?? artistRef.Name.ToUpperInvariant())
-            .Select(group => group.First())
-            .ToList();
-
-        var artists = new List<Artist>();
-        foreach (var artistRef in artistRefs)
-            artists.Add(await GetOrCreateArtistAsync(artistRef, cancellationToken));
-
-        var title = Truncate(song.Title, 200);
-        var track = new ExternalTrack
-        {
-            Title = title,
-            NormalizedTitle = title.ToUpperInvariant(),
-            Source = TrackSource.YouTube,
-            ExternalId = videoId,
-            DurationSeconds = song.DurationSeconds,
-            Pictures = new TrackPictures
-            {
-                SmallName = trackConfiguration.Routes.PresetSmallPicture,
-                MediumName = trackConfiguration.Routes.PresetMediumPicture,
-                LargeName = trackConfiguration.Routes.PresetLargePicture,
-                ProcessingStatus = ProcessingStatus.Pending
-            },
-            Audio = new TrackAudio
-            {
-                DownloadRequested = false,
-                TranscodeStatus = ProcessingStatus.Pending
-            }
-        };
-
-        await database.ExternalTracks.AddAsync(track, cancellationToken);
-
-        for (var position = 0; position < artists.Count; position++)
-        {
-            await database.TrackArtists.AddAsync(new TrackArtist
-            {
-                TrackId = track.Id,
-                ArtistId = artists[position].Id,
-                Position = position
-            }, cancellationToken);
-        }
-
-        try
-        {
-            await database.SaveChangesAsync(cancellationToken);
-            logger.LogInformation("Created YouTube track {VideoId} ({TrackId})", videoId, track.Id);
-            return new YouTubeTrackProvision(track, Song: song);
-        }
-        catch (DbUpdateException)
-        {
-            database.ExternalTracks.Remove(track);
-            var refetched = await FindAsync(videoId, cancellationToken);
-            if (refetched is null)
-            {
-                logger.LogWarning("YouTube track {VideoId} creation raced but could not be refetched", videoId);
-                return Error.Conflict(description: "The track was just created by another request. Retry the operation.");
-            }
-            return new YouTubeTrackProvision(refetched, Song: null);
-        }
-    }
-
-    public async Task MaterializeAlbumAsync(string albumExternalId, YouTubeAlbumDetail detail, CancellationToken cancellationToken)
-    {
-        var validTracks = detail.Tracks
-            .Where(track => !string.IsNullOrEmpty(track.VideoId))
-            .ToList();
-        if (validTracks.Count == 0)
-            return;
-
-        var album = await GetOrCreateExternalAlbumAsync(albumExternalId, detail.Album.Title, detail.Album.ThumbnailUrl, cancellationToken);
-
-        var videoIds = validTracks.Select(track => track.VideoId).ToList();
-
-        var tracksByVideoId = await database.ExternalTracks
-            .Where(track => track.Source == TrackSource.YouTube && videoIds.Contains(track.ExternalId))
-            .ToDictionaryAsync(track => track.ExternalId, cancellationToken);
-
-        var linkedTrackIds = (await database.AlbumHasTracks
-            .Where(albumTrack => albumTrack.AlbumId == album.Id)
-            .Select(albumTrack => albumTrack.TrackId)
-            .ToListAsync(cancellationToken))
-            .ToHashSet();
-
-        if (tracksByVideoId.Count == validTracks.Count && linkedTrackIds.Count >= validTracks.Count)
-            return;
-
-        var artistRefs = detail.Album.Artists
-            .GroupBy(artistRef => artistRef.Id ?? artistRef.Name.ToUpperInvariant())
-            .Select(group => group.First())
-            .ToList();
-
-        var albumArtists = new List<Artist>();
-        foreach (var artistRef in artistRefs)
-            albumArtists.Add(await GetOrCreateArtistAsync(artistRef, cancellationToken));
-
-        foreach (var albumTrack in validTracks)
-        {
-            if (!tracksByVideoId.TryGetValue(albumTrack.VideoId, out var track))
-            {
-                track = BuildStubTrack(albumTrack);
-                await database.ExternalTracks.AddAsync(track, cancellationToken);
-
-                for (var position = 0; position < albumArtists.Count; position++)
-                {
-                    await database.TrackArtists.AddAsync(new TrackArtist
-                    {
-                        TrackId = track.Id,
-                        ArtistId = albumArtists[position].Id,
-                        Position = position
-                    }, cancellationToken);
-                }
-
-                tracksByVideoId[albumTrack.VideoId] = track;
-            }
-
-            if (linkedTrackIds.Contains(track.Id))
-                continue;
-
-            await database.AlbumHasTracks.AddAsync(new AlbumHasTrack
-            {
-                AlbumId = album.Id,
-                TrackId = track.Id,
-                TrackNumber = albumTrack.TrackNumber
-            }, cancellationToken);
-            linkedTrackIds.Add(track.Id);
-        }
-
-        try
-        {
-            await database.SaveChangesAsync(cancellationToken);
-            logger.LogInformation("Materialized YouTube album {AlbumId} ({TrackCount} tracks)", albumExternalId, validTracks.Count);
-        }
-        catch (DbUpdateException exception)
-        {
-            logger.LogWarning(exception, "Race while materializing YouTube album {AlbumId}", albumExternalId);
-        }
-    }
-
-    private ExternalTrack BuildStubTrack(YouTubeAlbumTrack albumTrack)
-    {
-        var title = Truncate(albumTrack.Title, 200);
-        return new ExternalTrack
-        {
-            Title = title,
-            NormalizedTitle = title.ToUpperInvariant(),
-            Source = TrackSource.YouTube,
-            ExternalId = albumTrack.VideoId,
-            DurationSeconds = albumTrack.DurationSeconds,
-            Pictures = new TrackPictures
-            {
-                SmallName = trackConfiguration.Routes.PresetSmallPicture,
-                MediumName = trackConfiguration.Routes.PresetMediumPicture,
-                LargeName = trackConfiguration.Routes.PresetLargePicture,
-                ProcessingStatus = ProcessingStatus.Pending
-            },
-            Audio = new TrackAudio
-            {
-                DownloadRequested = false,
-                TranscodeStatus = ProcessingStatus.Pending
-            }
-        };
-    }
-
-    private async Task<Artist> GetOrCreateArtistAsync(YouTubeArtistRef reference, CancellationToken cancellationToken)
-    {
-        var name = Truncate(reference.Name, 200);
-        var normalized = name.ToUpperInvariant();
-        var externalId = reference.Id ?? $"name:{normalized}";
-
-        var existing = await database.Artists.SingleOrDefaultAsync(a => a.ExternalId == externalId, cancellationToken);
-        if (existing is not null)
-            return existing;
-
-        var artist = new Artist
-        {
-            Name = name,
-            NormalizedName = normalized,
-            ExternalId = externalId
-        };
-
-        await database.Artists.AddAsync(artist, cancellationToken);
-
-        try
-        {
-            await database.SaveChangesAsync(cancellationToken);
-            return artist;
-        }
-        catch (DbUpdateException)
-        {
-            database.Artists.Remove(artist);
-            return await database.Artists.SingleAsync(a => a.ExternalId == externalId, cancellationToken);
-        }
-    }
-
-    private async Task<ExternalAlbum> GetOrCreateExternalAlbumAsync(string externalId, string name, string? thumbnailUrl, CancellationToken cancellationToken)
-    {
-        var existing = await database.ExternalAlbums
-            .SingleOrDefaultAsync(album => album.Source == TrackSource.YouTube && album.ExternalId == externalId, cancellationToken);
-        if (existing is not null)
-            return existing;
-
-        var title = Truncate(name, 200);
-        var album = new ExternalAlbum
-        {
-            Title = title,
-            NormalizedTitle = title.ToUpperInvariant(),
-            Source = TrackSource.YouTube,
-            ExternalId = externalId,
-            ThumbnailUrl = string.IsNullOrEmpty(thumbnailUrl) ? null : Truncate(thumbnailUrl, 512)
-        };
-
-        await database.ExternalAlbums.AddAsync(album, cancellationToken);
-
-        try
-        {
-            await database.SaveChangesAsync(cancellationToken);
-            return album;
-        }
-        catch (DbUpdateException)
-        {
-            database.ExternalAlbums.Remove(album);
-            return await database.ExternalAlbums.SingleAsync(a => a.Source == TrackSource.YouTube && a.ExternalId == externalId, cancellationToken);
-        }
-    }
-
-    private static string Truncate(string value, int maxLength) =>
-        value.Length <= maxLength ? value : value[..maxLength];
-}

backend/Core/Musify.Application/Tracks/CreateTrack.cs

@@ -59,7 +59,7 @@ namespace Musify.Application.Tracks
             var finalAudioKey = trackConfiguration.Routes.BuildOriginalAudioPath(request.UserId, audioIntent.ObjectName);
             var audioProcessedFolderKey = trackConfiguration.Routes.BuildProcessedAudioPath(Guid.NewGuid().ToString());
 
-            var trackEntity = new LocalTrack
+            var trackEntity = new Track
             {
                 Title = request.Title,
                 NormalizedTitle = request.Title.ToUpperInvariant(),
@@ -80,7 +80,7 @@ namespace Musify.Application.Tracks
                 }
             };
 
-            await database.LocalTracks.AddAsync(trackEntity, cancellationToken);
+            await database.Tracks.AddAsync(trackEntity, cancellationToken);
 
             await database.UserHasTracks.AddAsync(new UserHasTrack
             {

backend/Core/Musify.Application/Tracks/DeleteTrack.cs

@@ -29,7 +29,7 @@ namespace Musify.Application.Tracks
                 return Error.NotFound();
             }
 
-            if (track is not LocalTrack localTrack || localTrack.OwnerUserId != request.UserId)
+            if (track.OwnerUserId != request.UserId)
             {
                 logger.LogWarning("User {UserId} unauthorized to delete track {TrackId}", request.UserId, request.TrackId);
                 return Error.Unauthorized();

backend/Core/Musify.Application/Tracks/GetListeningHistory.cs

@@ -2,7 +2,6 @@
 using Microsoft.EntityFrameworkCore;
 using Musify.Application.Contracts;
 using Musify.Application.Tracks.Responses;
-using Musify.Domain.Entities;
 
 namespace Musify.Application.Tracks
 {
@@ -25,9 +24,7 @@ namespace Musify.Application.Tracks
                 .ToListAsync(cancellationToken);
 
             var tracksById = await database.Tracks
-                .Include(t => ((ExternalTrack)t).TrackArtists)
-                    .ThenInclude(trackArtist => trackArtist.Artist)
-                .Include(t => ((LocalTrack)t).Owner)
+                .Include(t => t.Owner)
                 .Where(t => recentTrackIds.Contains(t.Id))
                 .Select(t => new { t.Id, Track = t, ListensCount = t.ListeningHistories.Count } )
                 .ToDictionaryAsync(t => t.Id, cancellationToken);

backend/Core/Musify.Application/Tracks/GetTrackById.cs

@@ -3,7 +3,6 @@ using Mediator;
 using Microsoft.EntityFrameworkCore;
 using Musify.Application.Contracts;
 using Musify.Application.Tracks.Responses;
-using Musify.Domain.Entities;
 
 namespace Musify.Application.Tracks
 {
@@ -16,9 +15,7 @@ namespace Musify.Application.Tracks
         public async ValueTask<ErrorOr<TrackApplicationResponse>> Handle(GetTrackByIdQuery request, CancellationToken cancellationToken)
         {
             var entity = await database.Tracks.AsNoTracking()
-                .Include(t => ((ExternalTrack)t).TrackArtists)
-                    .ThenInclude(trackArtist => trackArtist.Artist)
-                .Include(t => ((LocalTrack)t).Owner)
+                .Include(t => t.Owner)
                 .Where(t => t.Id == request.TrackId)
                 .Select(t => new { Track = t, ListensCount = t.ListeningHistories.Count })
                 .SingleOrDefaultAsync(cancellationToken);

backend/Core/Musify.Application/Tracks/GetTracks.cs

@@ -1,37 +1,24 @@
 using ErrorOr;
 using Mediator;
 using Microsoft.EntityFrameworkCore;
-using Microsoft.Extensions.Logging;
 using Musify.Application.Tracks.Responses;
 using X.PagedList;
 using X.PagedList.EF;
 using Musify.Application.Contracts;
-using Musify.Domain.Entities;
-using Musify.Domain.ValueObjects;
 
 namespace Musify.Application.Tracks
 {
-    public record GetTracksQuery(string? Name, int PageNumber, int PageSize, string? YoutubeContinuationToken = null)
+    public record GetTracksQuery(string? Name, int PageNumber, int PageSize)
         : IQuery<ErrorOr<TracksSearchResponse>>;
 
-    public class GetTracksQueryHandler(
-        IDatabase database,
-        IYouTubeMusicService youTubeMusicService,
-        ILogger<GetTracksQueryHandler> logger)
+    public class GetTracksQueryHandler(IDatabase database)
         : IQueryHandler<GetTracksQuery, ErrorOr<TracksSearchResponse>>
     {
-        // Mirrors the web client's search-box debounce threshold: a query shorter than this is too
-        // likely to still be mid-keystroke to justify a live call to the YouTube Music API for every
-        // client that hits this endpoint.
-        private const int MinNameLengthForYouTubeSearch = 2;
-
         public async ValueTask<ErrorOr<TracksSearchResponse>> Handle(GetTracksQuery request, CancellationToken cancellationToken)
         {
             var tracksQuery = database.UserHasTracks
                 .AsNoTracking()
-                .Include(ut => ((ExternalTrack)ut.Track).TrackArtists)
-                    .ThenInclude(trackArtist => trackArtist.Artist)
-                .Include(ut => ((LocalTrack)ut.Track).Owner)
+                .Include(ut => ut.Track.Owner)
                 .AsQueryable();
 
             if (!string.IsNullOrEmpty(request.Name))
@@ -48,61 +35,18 @@ namespace Musify.Application.Tracks
                 .Select(t => new { t.Track, ListensCount = t.Track.ListeningHistories.Count })
                 .ToPagedListAsync(request.PageNumber, request.PageSize, totalCount, cancellationToken);
 
-            var localItems = pagedEntities
+            var items = pagedEntities
                 .Select(x => TrackSearchItemResponse.FromTrack(TrackApplicationResponse.FromEntity(x.Track, x.ListensCount)))
                 .ToList();
 
-            var knownVideoIds = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
-            foreach (var entry in pagedEntities)
-            {
-                if (entry.Track is ExternalTrack { Source: TrackSource.YouTube } external)
-                    knownVideoIds.Add(external.ExternalId);
-            }
-
-            var youtubeItems = new List<TrackSearchItemResponse>();
-            string? nextContinuationToken = null;
-            var youtubeUnavailable = false;
-
-            if (request.Name?.Trim().Length >= MinNameLengthForYouTubeSearch)
-                (youtubeItems, nextContinuationToken, youtubeUnavailable) =
-                    await SearchYouTubeAsync(request.Name, request.YoutubeContinuationToken, knownVideoIds, cancellationToken);
-
-            return TracksSearchResponse.Create(
-                [.. localItems, .. youtubeItems],
+            return new TracksSearchResponse(
+                items,
                 pagedEntities.PageNumber,
                 pagedEntities.PageSize,
                 pagedEntities.PageCount,
                 pagedEntities.TotalItemCount,
                 pagedEntities.HasPreviousPage,
-                pagedEntities.HasNextPage,
-                nextContinuationToken,
-                youtubeUnavailable);
-        }
-
-        private async Task<(List<TrackSearchItemResponse> Items, string? NextContinuationToken, bool Unavailable)> SearchYouTubeAsync(
-            string name,
-            string? continuationToken,
-            HashSet<string> knownVideoIds,
-            CancellationToken cancellationToken)
-        {
-            var searchResult = await youTubeMusicService.SearchSongsAsync(name, continuationToken ?? string.Empty, cancellationToken);
-            if (searchResult.IsError)
-            {
-                logger.LogInformation(
-                    "YouTube search unavailable while combining track results: {Error}", searchResult.FirstError.Description);
-                return ([], null, true);
-            }
-
-            var items = searchResult.Value.Items
-                .Where(song => knownVideoIds.Add(song.VideoId))
-                .Select(TrackSearchItemResponse.FromYouTubeSong)
-                .ToList();
-
-            var nextToken = string.IsNullOrEmpty(searchResult.Value.ContinuationToken)
-                ? null
-                : searchResult.Value.ContinuationToken;
-
-            return (items, nextToken, false);
+                pagedEntities.HasNextPage);
         }
     }
 }

backend/Core/Musify.Application/Tracks/GetTracksByUserId.cs

@@ -6,7 +6,6 @@ using Musify.Application.Tracks.Responses;
 using X.PagedList;
 using X.PagedList.EF;
 using Musify.Application.Contracts;
-using Musify.Domain.Entities;
 
 namespace Musify.Application.Tracks
 {
@@ -27,9 +26,7 @@ namespace Musify.Application.Tracks
 
             var tracksQuery = database.UserHasTracks
                 .AsNoTracking()
-                .Include(ut => ((ExternalTrack)ut.Track).TrackArtists)
-                    .ThenInclude(trackArtist => trackArtist.Artist)
-                .Include(ut => ((LocalTrack)ut.Track).Owner)
+                .Include(ut => ut.Track.Owner)
                 .Where(p => p.UserId == request.UserId);
 
             if (!string.IsNullOrEmpty(request.Name))

backend/Core/Musify.Application/Tracks/Responses/ExternalTrackApplicationResponse.cs

@@ -1,30 +0,0 @@
-using Musify.Domain.Entities;
-using Musify.Domain.ValueObjects;
-
-namespace Musify.Application.Tracks.Responses
-{
-    public record ExternalTrackApplicationResponse(
-        Guid Id,
-        string Title,
-        string? Artist,
-        ProcessingStatus AudioStatus,
-        double Duration,
-        int ListensCount,
-        DateTime CreatedAt,
-        DateTime UpdatedAt,
-        string ExternalId)
-        : TrackApplicationResponse(Id, Title, Artist, AudioStatus, Duration, ListensCount, CreatedAt, UpdatedAt)
-    {
-        public static ExternalTrackApplicationResponse FromEntity(ExternalTrack track, int listensCount) =>
-            new(
-                track.Id,
-                track.Title,
-                FormatArtist(track),
-                track.Audio.TranscodeStatus,
-                track.DurationSeconds,
-                listensCount,
-                track.CreatedAt,
-                track.UpdatedAt,
-                track.ExternalId);
-    }
-}

backend/Core/Musify.Application/Tracks/Responses/LocalTrackApplicationResponse.cs

@@ -1,32 +0,0 @@
-using System.Text.Json.Serialization;
-using Musify.Application.Serialization;
-using Musify.Domain.Entities;
-using Musify.Domain.ValueObjects;
-
-namespace Musify.Application.Tracks.Responses
-{
-    public record LocalTrackApplicationResponse(
-        Guid Id,
-        string Title,
-        string? Artist,
-        ProcessingStatus AudioStatus,
-        double Duration,
-        int ListensCount,
-        DateTime CreatedAt,
-        DateTime UpdatedAt,
-        [property: JsonConverter(typeof(LongAsStringConverter))] long OwnerUserId)
-        : TrackApplicationResponse(Id, Title, Artist, AudioStatus, Duration, ListensCount, CreatedAt, UpdatedAt)
-    {
-        public static LocalTrackApplicationResponse FromEntity(LocalTrack track, int listensCount) =>
-            new(
-                track.Id,
-                track.Title,
-                FormatArtist(track),
-                track.Audio.TranscodeStatus,
-                track.DurationSeconds,
-                listensCount,
-                track.CreatedAt,
-                track.UpdatedAt,
-                track.OwnerUserId);
-    }
-}

backend/Core/Musify.Application/Tracks/Responses/TrackApplicationResponse.cs

@@ -1,24 +1,11 @@
-using System.Text.Json.Serialization;
+using Musify.Application.Serialization;
 using Musify.Domain.Entities;
 using Musify.Domain.ValueObjects;
+using System.Text.Json.Serialization;
 
 namespace Musify.Application.Tracks.Responses
 {
-    // See AlbumApplicationResponse for why [JsonPolymorphic]/[JsonDerivedType] are required
-    // (not optional) whenever a base type carries subtype-only data across the wire. Track is a
-    // cleaner case than Album: both OwnerUserId (local-only) and ExternalId (external-only) are
-    // genuinely exclusive to one side, so the base has no "meaningless sentinel" field at all —
-    // every real value is one of the two derived types, hence base is abstract.
-    //
-    // No explicit Source property here (unlike the domain entities): STJ's polymorphism support
-    // already injects a "source" discriminator property with the same "Local"/"YouTube" values a
-    // hand-written TrackSource field would have, and a real property with that exact name would
-    // collide with it ("contains property 'source' that conflicts with an existing metadata
-    // property name"). Use the discriminator (or a type check) instead of a Source field.
-    [JsonPolymorphic(TypeDiscriminatorPropertyName = "source")]
-    [JsonDerivedType(typeof(LocalTrackApplicationResponse), typeDiscriminator: "Local")]
-    [JsonDerivedType(typeof(ExternalTrackApplicationResponse), typeDiscriminator: "YouTube")]
-    public abstract record TrackApplicationResponse(
+    public record TrackApplicationResponse(
         Guid Id,
         string Title,
         string? Artist,
@@ -26,24 +13,19 @@ namespace Musify.Application.Tracks.Responses
         double Duration,
         int ListensCount,
         DateTime CreatedAt,
-        DateTime UpdatedAt)
+        DateTime UpdatedAt,
+        [property: JsonConverter(typeof(LongAsStringConverter))] long OwnerUserId)
     {
         public static TrackApplicationResponse FromEntity(Track track, int listensCount) =>
-            track switch
-            {
-                LocalTrack local => LocalTrackApplicationResponse.FromEntity(local, listensCount),
-                ExternalTrack external => ExternalTrackApplicationResponse.FromEntity(external, listensCount),
-                _ => throw new NotSupportedException($"Unsupported track entity type '{track.GetType().Name}'.")
-            };
-
-        protected static string? FormatArtist(Track track) => track switch
-        {
-            LocalTrack local => local.Owner.Name,
-            ExternalTrack { TrackArtists.Count: > 0 } external =>
-                string.Join(", ", external.TrackArtists
-                    .OrderBy(trackArtist => trackArtist.Position)
-                    .Select(trackArtist => trackArtist.Artist.Name)),
-            _ => null
-        };
+            new(
+                track.Id,
+                track.Title,
+                track.Owner.Name,
+                track.Audio.TranscodeStatus,
+                track.DurationSeconds,
+                listensCount,
+                track.CreatedAt,
+                track.UpdatedAt,
+                track.OwnerUserId);
     }
 }

backend/Core/Musify.Application/Tracks/Responses/TrackSearchItemResponse.cs

@@ -1,22 +1,7 @@
-using Musify.Application.Contracts;
-using Musify.Domain.ValueObjects;
-
 namespace Musify.Application.Tracks.Responses
 {
-    /// <summary>One item of a combined local/YouTube track listing. Exactly one of
-    /// <see cref="Track"/> or <see cref="YouTubeSong"/> is populated: <see cref="Track"/> for
-    /// anything already in the catalog (local uploads and YouTube tracks provisioned earlier),
-    /// <see cref="YouTubeSong"/> for a live YouTube Music search hit that has not been
-    /// provisioned yet, so it has no track id.</summary>
-    public record TrackSearchItemResponse(
-        TrackSource Source,
-        TrackApplicationResponse? Track,
-        YouTubeSongResult? YouTubeSong)
+    public record TrackSearchItemResponse(TrackApplicationResponse Track)
     {
-        public static TrackSearchItemResponse FromTrack(TrackApplicationResponse track) =>
-            new(track is ExternalTrackApplicationResponse ? TrackSource.YouTube : TrackSource.Local, track, null);
-
-        public static TrackSearchItemResponse FromYouTubeSong(YouTubeSongResult song) =>
-            new(TrackSource.YouTube, null, song);
+        public static TrackSearchItemResponse FromTrack(TrackApplicationResponse track) => new(track);
     }
 }

backend/Core/Musify.Application/Tracks/Responses/TracksSearchResponse.cs

@@ -1,11 +1,6 @@
 namespace Musify.Application.Tracks.Responses
 {
-    /// <summary>Result of a combined tracks listing/search: a page of local catalog tracks
-    /// (uploads and previously provisioned YouTube tracks), plus, when a search term was given,
-    /// live YouTube Music hits appended after them. Pagination metadata (<see cref="PageNumber"/>,
-    /// <see cref="PageSize"/>, <see cref="PageCount"/>, <see cref="TotalItemCount"/>) describes only
-    /// the local page — YouTube has no stable total, so its continuation is tracked separately via
-    /// <see cref="NextYoutubeContinuationToken"/>.</summary>
+    /// <summary>A page of the user's catalog tracks (their own uploads).</summary>
     public record TracksSearchResponse(
         IReadOnlyList<TrackSearchItemResponse> Items,
         int PageNumber,
@@ -13,26 +8,5 @@ namespace Musify.Application.Tracks.Responses
         int PageCount,
         int TotalItemCount,
         bool HasPreviousPage,
-        bool HasNextLocalPage,
-        string? NextYoutubeContinuationToken,
-        bool YoutubeUnavailable,
-        bool HasNextPage)
-    {
-        // HasNextPage is a real field (not a computed property) so it shows up as a required member
-        // of the generated OpenAPI schema, same as every other field here — a get-only property added
-        // outside the primary constructor gets reflected as optional instead, which is never true here.
-        public static TracksSearchResponse Create(
-            IReadOnlyList<TrackSearchItemResponse> items,
-            int pageNumber,
-            int pageSize,
-            int pageCount,
-            int totalItemCount,
-            bool hasPreviousPage,
-            bool hasNextLocalPage,
-            string? nextYoutubeContinuationToken,
-            bool youtubeUnavailable) =>
-            new(items, pageNumber, pageSize, pageCount, totalItemCount, hasPreviousPage, hasNextLocalPage,
-                nextYoutubeContinuationToken, youtubeUnavailable,
-                HasNextPage: hasNextLocalPage || !string.IsNullOrEmpty(nextYoutubeContinuationToken));
-    }
+        bool HasNextPage);
 }

backend/Core/Musify.Application/YouTube/GetYouTubeAlbum.cs

@@ -1,36 +0,0 @@
-using ErrorOr;
-using Mediator;
-using Microsoft.Extensions.Logging;
-using Musify.Application.Contracts;
-using Musify.Application.Services;
-
-namespace Musify.Application.YouTube
-{
-    public record GetYouTubeAlbumQuery(string AlbumId)
-        : IQuery<ErrorOr<YouTubeAlbumDetail>>;
-
-    public class GetYouTubeAlbumQueryHandler(
-        IYouTubeMusicService youTubeMusicService,
-        YouTubeTrackProvisioner provisioner,
-        ILogger<GetYouTubeAlbumQueryHandler> logger)
-        : IQueryHandler<GetYouTubeAlbumQuery, ErrorOr<YouTubeAlbumDetail>>
-    {
-        public async ValueTask<ErrorOr<YouTubeAlbumDetail>> Handle(GetYouTubeAlbumQuery request, CancellationToken cancellationToken)
-        {
-            var result = await youTubeMusicService.GetAlbumAsync(request.AlbumId, cancellationToken);
-            if (result.IsError)
-                return result;
-
-            try
-            {
-                await provisioner.MaterializeAlbumAsync(request.AlbumId, result.Value, cancellationToken);
-            }
-            catch (Exception exception)
-            {
-                logger.LogWarning(exception, "Failed to materialize YouTube album {AlbumId}", request.AlbumId);
-            }
-
-            return result;
-        }
-    }
-}

backend/Core/Musify.Application/YouTube/ResolveYouTubeTrackStream.cs

@@ -1,85 +0,0 @@
-using ErrorOr;
-using Mediator;
-using Microsoft.EntityFrameworkCore;
-using Microsoft.Extensions.Logging;
-using Musify.Application.Configuration;
-using Musify.Application.Contracts;
-using Musify.Application.Services;
-using Musify.Application.YouTube.Responses;
-using Musify.Domain.Entities;
-
-namespace Musify.Application.YouTube
-{
-    public record ResolveYouTubeTrackStreamCommand(string VideoId, long? UserId)
-        : ICommand<ErrorOr<YouTubeStreamResponse>>;
-
-    public class ResolveYouTubeTrackStreamCommandHandler(
-        IDatabase database,
-        IYouTubeMusicService youTubeMusicService,
-        YouTubeTrackProvisioner provisioner,
-        TrackStreamIssuer streamIssuer,
-        PlaybackConfiguration playbackConfiguration,
-        ILogger<ResolveYouTubeTrackStreamCommandHandler> logger)
-        : ICommandHandler<ResolveYouTubeTrackStreamCommand, ErrorOr<YouTubeStreamResponse>>
-    {
-        public async ValueTask<ErrorOr<YouTubeStreamResponse>> Handle(ResolveYouTubeTrackStreamCommand request, CancellationToken cancellationToken)
-        {
-            var isAnonymous = !request.UserId.HasValue;
-            if (isAnonymous && !playbackConfiguration.AllowAnonymousListening)
-                return Error.Unauthorized(description: "Sign in to stream music, or ask an administrator to enable anonymous listening.");
-
-            var track = await provisioner.FindAsync(request.VideoId, cancellationToken);
-
-            if (track != null && track.Audio.IsProcessed)
-            {
-                var serverStream = await streamIssuer.IssueAsync(track.Id, track.Audio.FolderName, request.UserId, cancellationToken);
-                return new YouTubeStreamResponse(
-                    track.Id,
-                    YouTubeStreamMode.Server,
-                    serverStream.ManifestUrl,
-                    serverStream.Ticket,
-                    serverStream.ExpiresInSeconds);
-            }
-
-            if (isAnonymous && playbackConfiguration.AnonymousFragmentSeconds > 0)
-                return Error.Conflict(description: "This track isn't available for anonymous preview yet. Try again in a moment.");
-
-            var streamInfo = await youTubeMusicService.GetAudioStreamAsync(request.VideoId, cancellationToken);
-            if (streamInfo.IsError)
-                return streamInfo.Errors;
-
-            if (track == null)
-            {
-                var provisionResult = await provisioner.GetOrCreateAsync(request.VideoId, cancellationToken);
-                if (!provisionResult.IsError)
-                    track = provisionResult.Value.Track;
-                else
-                    logger.LogWarning("Could not provision YouTube track {VideoId}: {Error}", request.VideoId, provisionResult.FirstError.Description);
-            }
-
-            if (track != null&& request.UserId != null)
-            {
-                await database.ListeningHistories.AddAsync(new ListeningHistory
-                {
-                    UserId = request.UserId.Value,
-                    TrackId = track.Id,
-                }, cancellationToken);
-
-                try
-                {
-                    await database.SaveChangesAsync(cancellationToken);
-                }
-                catch (DbUpdateException exception)
-                {
-                    logger.LogWarning(exception, "Failed to record listening history for YouTube video {VideoId}", request.VideoId);
-                }
-            }
-
-            return new YouTubeStreamResponse(
-                track?.Id,
-                YouTubeStreamMode.YouTube,
-                streamInfo.Value.Url, null,
-                streamInfo.Value.ExpiresInSeconds);
-        }
-    }
-}

backend/Core/Musify.Application/YouTube/Responses/YouTubeStreamResponse.cs

@@ -1,15 +0,0 @@
-namespace Musify.Application.YouTube.Responses
-{
-    public enum YouTubeStreamMode
-    {
-        Server = 0,
-        YouTube = 1
-    }
-
-    public record YouTubeStreamResponse(
-        Guid? TrackId,
-        YouTubeStreamMode Mode,
-        string StreamUrl,
-        string? Ticket,
-        int ExpiresInSeconds);
-}