Restore the invitations tab, render library tracks on first paint and re-measure the tab indicator

Owners invite existing users to coauthor a track; invitees accept or reject,
and either side can remove a coauthor. Only accepted coauthors appear in track
responses and in the coauthor's public track list. The owner also receives the
full invitation list with statuses on the user tracks response.

.claude/launch.json

@@ -14,6 +14,12 @@
 			"runtimeArgs": ["run", "--project", "backend/Hosts/Musify.Api"],
 			"port": 5111
 		},
+		{
+			"name": "musify-worker",
+			"runtimeExecutable": "dotnet",
+			"runtimeArgs": ["run", "--project", "backend/Hosts/Musify.Worker"],
+			"port": 5112
+		},
 		{
 			"name": "musify-streaming-gateway",
 			"runtimeExecutable": "dotnet",

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

@@ -9,7 +9,6 @@ using Musify.Domain.ValueObjects;
 
 namespace Musify.Application.Albums
 {
-    /// <summary>Appends your own tracks to an album in the given order, skipping the ones it already has.</summary>
     public record AddTracksToAlbumCommand(long UserId, Guid AlbumId, IReadOnlyList<Guid> TrackIds)
         : ICommand<ErrorOr<Success>>;
 
@@ -50,7 +49,6 @@ namespace Musify.Application.Albums
             if (toAdd.Count == 0)
                 return Result.Success;
 
-            // Album track numbers are user-visible, so they start at 1.
             var nextTrackNumber = (await database.AlbumHasTracks
                 .Where(link => link.AlbumId == request.AlbumId)
                 .MaxAsync(link => (int?)link.TrackNumber, cancellationToken) ?? 0) + 1;

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

@@ -19,7 +19,9 @@ namespace Musify.Application.Albums
         string Title,
         string? Description,
         int? ReleaseYear,
-        Guid PictureIntentId)
+        Guid PictureIntentId,
+        AlbumType Type = AlbumType.Album,
+        IReadOnlyList<Guid>? TrackIds = null)
         : ICommand<ErrorOr<AlbumApplicationResponse>>;
 
     public class CreateAlbumCommandHandler(
@@ -38,6 +40,21 @@ namespace Musify.Application.Albums
             if (!userExists)
                 return AppErrors.NotFound("User", request.UserId);
 
+            var trackIds = (request.TrackIds ?? []).Distinct().ToList();
+            var tracks = await database.Tracks
+                .AsNoTracking()
+                .Where(track => trackIds.Contains(track.Id) && track.LifeCycleStatus == LifeCycleStatus.Active)
+                .Select(track => new { track.Id, track.OwnerUserId, track.IsPublished })
+                .ToListAsync(cancellationToken);
+
+            var missing = trackIds.FirstOrDefault(id => tracks.All(track => track.Id != id));
+            if (missing != Guid.Empty)
+                return AppErrors.NotFound("Track", missing);
+
+            var foreign = tracks.FirstOrDefault(track => track.OwnerUserId != request.UserId);
+            if (foreign != null)
+                return AppErrors.Forbidden("Track", foreign.Id);
+
             var prepared = await PictureSourceChange.PrepareAsync(
                 uploadIntentValidator, request.PictureIntentId, request.UserId, UploadIntentPurpose.AlbumPicture, albumConfiguration, cancellationToken);
             if (prepared.IsError)
@@ -53,11 +70,19 @@ namespace Musify.Application.Albums
                 NormalizedTitle = TextNormalizer.Normalize(title),
                 Description = request.Description,
                 ReleaseYear = request.ReleaseYear,
+                Type = request.Type,
                 Pictures = picture.Pictures
             };
 
             await database.Albums.AddAsync(album, cancellationToken);
 
+            for (var index = 0; index < trackIds.Count; index++)
+            {
+                await database.AlbumHasTracks.AddAsync(
+                    new AlbumHasTrack { AlbumId = album.Id, TrackId = trackIds[index], TrackNumber = index + 1 },
+                    cancellationToken);
+            }
+
             await eventBus.PublishAsync(
                 new CreateAlbumResourcesEvent(
                     album.Id, picture.Intent.Id, picture.Intent.Bucket, picture.Intent.Key, picture.FinalKey, picture.Sizes),
@@ -65,9 +90,15 @@ namespace Musify.Application.Albums
 
             await database.SaveChangesAsync(cancellationToken);
 
-            logger.LogInformation("Created album {AlbumId} for user {UserId}", album.Id, request.UserId);
+            logger.LogInformation("Created album {AlbumId} for user {UserId} with {Count} tracks", album.Id, request.UserId, trackIds.Count);
 
-            return AlbumApplicationResponse.FromEntity(album, trackCount: 0);
+            var published = tracks.Where(track => track.IsPublished).Select(track => track.Id).ToHashSet();
+            var visibleTrackIds = trackIds.Where(published.Contains).ToList();
+
+            return AlbumApplicationResponse.FromEntity(
+                album,
+                visibleTrackIds.Count,
+                [.. visibleTrackIds.Take(AlbumProjections.CoverTrackCount)]);
         }
     }
 }

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

@@ -0,0 +1,35 @@
+using ErrorOr;
+using Mediator;
+using Microsoft.EntityFrameworkCore;
+using Musify.Application.Albums.Responses;
+using Musify.Application.Contracts;
+using Musify.Application.Shared;
+using Musify.Domain.ValueObjects;
+
+namespace Musify.Application.Albums
+{
+    public record GetAlbumTrackIdsQuery(long UserId, Guid AlbumId)
+        : IQuery<ErrorOr<AlbumTrackIdsResponse>>;
+
+    public class GetAlbumTrackIdsQueryHandler(IDatabase database)
+        : IQueryHandler<GetAlbumTrackIdsQuery, ErrorOr<AlbumTrackIdsResponse>>
+    {
+        public async ValueTask<ErrorOr<AlbumTrackIdsResponse>> Handle(GetAlbumTrackIdsQuery request, CancellationToken cancellationToken)
+        {
+            var found = await database.Albums.FindOwnedAsync(request.AlbumId, request.UserId, cancellationToken);
+            if (found.IsError)
+                return found.Errors;
+
+            var trackIds = await database.AlbumHasTracks
+                .AsNoTracking()
+                .Where(albumTrack => albumTrack.AlbumId == request.AlbumId
+                    && albumTrack.Track.LifeCycleStatus == LifeCycleStatus.Active)
+                .OrderBy(albumTrack => albumTrack.TrackNumber)
+                .ThenBy(albumTrack => albumTrack.Id)
+                .Select(albumTrack => albumTrack.TrackId)
+                .ToListAsync(cancellationToken);
+
+            return new AlbumTrackIdsResponse(trackIds);
+        }
+    }
+}

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

@@ -28,7 +28,7 @@ namespace Musify.Application.Albums
 
             return await database.AlbumHasTracks
                 .AsNoTracking()
-                .Where(albumTrack => albumTrack.AlbumId == request.AlbumId && albumTrack.Track.LifeCycleStatus == Domain.ValueObjects.LifeCycleStatus.Active)
+                .Where(albumTrack => albumTrack.AlbumId == request.AlbumId && albumTrack.Track.LifeCycleStatus == Domain.ValueObjects.LifeCycleStatus.Active && albumTrack.Track.IsPublished)
                 .OrderBy(albumTrack => albumTrack.TrackNumber)
                 .ThenBy(albumTrack => albumTrack.Id)
                 .Select(albumTrack => albumTrack.Track)

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

@@ -20,6 +20,7 @@ namespace Musify.Application.Albums
             var ranked = await database.AlbumHasTracks
                 .AsNoTracking()
                 .Where(albumTrack => albumTrack.Album.LifeCycleStatus == Domain.ValueObjects.LifeCycleStatus.Active)
+                .Where(albumTrack => albumTrack.Track.LifeCycleStatus == Domain.ValueObjects.LifeCycleStatus.Active && albumTrack.Track.IsPublished)
                 .Join(
                     listens,
                     albumTrack => albumTrack.TrackId,

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

@@ -1,4 +1,5 @@
 using Musify.Domain.Entities;
+using Musify.Domain.ValueObjects;
 
 namespace Musify.Application.Albums.Responses
 {
@@ -14,7 +15,8 @@ namespace Musify.Application.Albums.Responses
         string? LargeImageKeyName,
         DateTime CreatedAt,
         DateTime UpdatedAt,
-        IReadOnlyList<Guid> CoverTrackIds)
+        IReadOnlyList<Guid> CoverTrackIds,
+        AlbumType Type)
     {
         public const int CoverTrackCount = AlbumProjections.CoverTrackCount;
 
@@ -35,7 +37,8 @@ namespace Musify.Application.Albums.Responses
                 album.Pictures?.LargeName,
                 album.CreatedAt,
                 album.UpdatedAt,
-                coverTrackIds ?? []);
+                coverTrackIds ?? [],
+                album.Type);
         }
     }
 }

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

@@ -17,16 +17,18 @@ namespace Musify.Application.Albums.Responses
                 album.Description,
                 album.ReleaseYear,
                 album.OwnerUserId,
-                album.AlbumTracks.Count,
+                album.AlbumTracks.Count(albumTrack => albumTrack.Track.LifeCycleStatus == LifeCycleStatus.Active && albumTrack.Track.IsPublished),
                 album.Pictures!.SmallName,
                 album.Pictures!.MediumName,
                 album.Pictures!.LargeName,
                 album.CreatedAt,
                 album.UpdatedAt,
                 album.AlbumTracks
+                    .Where(albumTrack => albumTrack.Track.LifeCycleStatus == LifeCycleStatus.Active && albumTrack.Track.IsPublished)
                     .OrderBy(albumTrack => albumTrack.TrackNumber)
                     .Take(CoverTrackCount)
                     .Select(albumTrack => albumTrack.TrackId)
-                    .ToList()));
+                    .ToList(),
+                album.Type));
     }
 }

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

@@ -0,0 +1,4 @@
+namespace Musify.Application.Albums.Responses
+{
+    public record AlbumTrackIdsResponse(IReadOnlyList<Guid> TrackIds);
+}

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

@@ -3,11 +3,7 @@ using Mediator;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.Logging;
 using Musify.Application.Albums.Responses;
-using Musify.Application.Configuration;
 using Musify.Application.Contracts;
-using Musify.Application.Events;
-using Musify.Application.Pictures;
-using Musify.Application.Services;
 using Musify.Application.Shared;
 using Musify.Domain.ValueObjects;
 
@@ -19,15 +15,12 @@ namespace Musify.Application.Albums
         string Title,
         string? Description,
         int? ReleaseYear,
-        Guid? NewPictureIntentId)
+        AlbumType? Type = null)
         : ICommand<ErrorOr<AlbumApplicationResponse>>;
 
     public class UpdateAlbumCommandHandler(
-        IEventBus eventBus,
         IDatabase database,
-        UploadIntentValidator uploadIntentValidator,
+        ILogger<UpdateAlbumCommandHandler> logger)
-        ILogger<UpdateAlbumCommandHandler> logger,
-        AlbumConfiguration albumConfiguration)
         : ICommandHandler<UpdateAlbumCommand, ErrorOr<AlbumApplicationResponse>>
     {
         public async ValueTask<ErrorOr<AlbumApplicationResponse>> Handle(UpdateAlbumCommand request, CancellationToken cancellationToken)
@@ -41,24 +34,9 @@ namespace Musify.Application.Albums
 
             album.Title = title;
             album.NormalizedTitle = TextNormalizer.Normalize(title);
-            album.Description = request.Description;
+            album.Description = string.IsNullOrWhiteSpace(request.Description) ? null : request.Description.Trim();
             album.ReleaseYear = request.ReleaseYear;
-
+            album.Type = request.Type ?? album.Type;
-            if (request.NewPictureIntentId is { } intentId)
-            {
-                var prepared = await PictureSourceChange.PrepareAsync(
-                    uploadIntentValidator, intentId, request.UserId, UploadIntentPurpose.AlbumPicture, albumConfiguration, cancellationToken);
-                if (prepared.IsError)
-                    return prepared.Errors;
-
-                var picture = prepared.Value;
-                album.Pictures = picture.Pictures;
-
-                await eventBus.PublishAsync(
-                    new UpdateAlbumPictureSourceEvent(
-                        album.Id, picture.Intent.Id, picture.Intent.Bucket, picture.Intent.Key, picture.FinalKey, picture.Sizes),
-                    cancellationToken);
-            }
 
             await database.SaveChangesAsync(cancellationToken);
 

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

@@ -0,0 +1,59 @@
+using ErrorOr;
+using Mediator;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging;
+using Musify.Application.Albums.Responses;
+using Musify.Application.Configuration;
+using Musify.Application.Contracts;
+using Musify.Application.Events;
+using Musify.Application.Pictures;
+using Musify.Application.Services;
+using Musify.Application.Shared;
+using Musify.Domain.ValueObjects;
+
+namespace Musify.Application.Albums
+{
+    public record UpdateAlbumPictureCommand(long UserId, Guid AlbumId, Guid PictureIntentId)
+        : ICommand<ErrorOr<AlbumApplicationResponse>>;
+
+    public class UpdateAlbumPictureCommandHandler(
+        IEventBus eventBus,
+        IDatabase database,
+        UploadIntentValidator uploadIntentValidator,
+        ILogger<UpdateAlbumPictureCommandHandler> logger,
+        AlbumConfiguration albumConfiguration)
+        : ICommandHandler<UpdateAlbumPictureCommand, ErrorOr<AlbumApplicationResponse>>
+    {
+        public async ValueTask<ErrorOr<AlbumApplicationResponse>> Handle(UpdateAlbumPictureCommand request, CancellationToken cancellationToken)
+        {
+            var found = await database.Albums.FindOwnedAsync(request.AlbumId, request.UserId, cancellationToken);
+            if (found.IsError)
+                return found.Errors;
+
+            var album = found.Value;
+
+            var prepared = await PictureSourceChange.PrepareAsync(
+                uploadIntentValidator, request.PictureIntentId, request.UserId, UploadIntentPurpose.AlbumPicture, albumConfiguration, cancellationToken);
+            if (prepared.IsError)
+                return prepared.Errors;
+
+            var picture = prepared.Value;
+            album.Pictures = picture.Pictures;
+
+            await eventBus.PublishAsync(
+                new UpdateAlbumPictureSourceEvent(
+                    album.Id, picture.Intent.Id, picture.Intent.Bucket, picture.Intent.Key, picture.FinalKey, picture.Sizes),
+                cancellationToken);
+
+            await database.SaveChangesAsync(cancellationToken);
+
+            logger.LogInformation("Updated picture of album {AlbumId}", album.Id);
+
+            return await database.Albums
+                .AsNoTracking()
+                .Where(a => a.Id == album.Id)
+                .SelectResponse()
+                .SingleAsync(cancellationToken);
+        }
+    }
+}

backend/Core/Musify.Application/Coauthors/GetCoauthorInvitations.cs

@@ -0,0 +1,35 @@
+using Mediator;
+using Microsoft.EntityFrameworkCore;
+using Musify.Application.Coauthors.Responses;
+using Musify.Application.Contracts;
+using Musify.Application.Shared;
+using Musify.Domain.ValueObjects;
+
+namespace Musify.Application.Coauthors
+{
+    public record GetCoauthorInvitationsQuery(long UserId, int PageNumber, int PageSize)
+        : IQuery<PaginatedResponse<CoauthorInvitationResponse>>;
+
+    public class GetCoauthorInvitationsQueryHandler(IDatabase database)
+        : IQueryHandler<GetCoauthorInvitationsQuery, PaginatedResponse<CoauthorInvitationResponse>>
+    {
+        public async ValueTask<PaginatedResponse<CoauthorInvitationResponse>> Handle(GetCoauthorInvitationsQuery request, CancellationToken cancellationToken)
+        {
+            return await database.TrackCoauthors
+                .AsNoTracking()
+                .Where(coauthor => coauthor.UserId == request.UserId
+                    && coauthor.Status == CoauthorStatus.Pending
+                    && coauthor.Track.LifeCycleStatus == LifeCycleStatus.Active)
+                .OrderByDescending(coauthor => coauthor.InvitedAt)
+                .ThenBy(coauthor => coauthor.Id)
+                .Select(coauthor => new CoauthorInvitationResponse(
+                    coauthor.Id,
+                    coauthor.TrackId,
+                    coauthor.Track.Title,
+                    coauthor.Track.Owner.Name,
+                    coauthor.Track.OwnerUserId,
+                    coauthor.InvitedAt))
+                .ToPaginatedAsync(new PageRequest(request.PageNumber, request.PageSize), cancellationToken);
+        }
+    }
+}

backend/Core/Musify.Application/Coauthors/InviteCoauthors.cs

@@ -0,0 +1,84 @@
+using ErrorOr;
+using Mediator;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging;
+using Musify.Application.Contracts;
+using Musify.Application.Shared;
+using Musify.Application.Tracks.Responses;
+using Musify.Domain.Entities;
+using Musify.Domain.ValueObjects;
+
+namespace Musify.Application.Coauthors
+{
+    public record InviteCoauthorsCommand(long OwnerId, Guid TrackId, IReadOnlyList<long> UserIds)
+        : ICommand<ErrorOr<IReadOnlyList<TrackCoauthorInviteReference>>>;
+
+    public class InviteCoauthorsCommandHandler(
+        IDatabase database,
+        ILogger<InviteCoauthorsCommandHandler> logger)
+        : ICommandHandler<InviteCoauthorsCommand, ErrorOr<IReadOnlyList<TrackCoauthorInviteReference>>>
+    {
+        public async ValueTask<ErrorOr<IReadOnlyList<TrackCoauthorInviteReference>>> Handle(InviteCoauthorsCommand request, CancellationToken cancellationToken)
+        {
+            var found = await database.Tracks.FindOwnedAsync(request.TrackId, request.OwnerId, cancellationToken);
+            if (found.IsError)
+                return found.Errors;
+
+            var userIds = request.UserIds.Distinct().ToList();
+            if (userIds.Contains(request.OwnerId))
+                return Error.Validation("Coauthor.Self", "You cannot invite yourself as a coauthor.");
+
+            var existingUserIds = await database.Users
+                .AsNoTracking()
+                .Where(user => userIds.Contains(user.Id))
+                .Select(user => user.Id)
+                .ToListAsync(cancellationToken);
+
+            var missing = userIds.Where(id => !existingUserIds.Contains(id)).Select(id => (long?)id).FirstOrDefault();
+            if (missing != null)
+                return AppErrors.NotFound("User", missing.Value);
+
+            var existing = await database.TrackCoauthors
+                .Where(coauthor => coauthor.TrackId == request.TrackId && userIds.Contains(coauthor.UserId))
+                .ToListAsync(cancellationToken);
+
+            var alreadyInvited = existing.FirstOrDefault(coauthor => coauthor.Status != CoauthorStatus.Rejected);
+            if (alreadyInvited != null)
+                return AppErrors.Conflict("Coauthor.AlreadyInvited", $"User {alreadyInvited.UserId} was already invited to this track.");
+
+            var now = DateTime.UtcNow;
+            foreach (var rejected in existing)
+            {
+                rejected.Status = CoauthorStatus.Pending;
+                rejected.InvitedAt = now;
+                rejected.RespondedAt = null;
+            }
+
+            var reinvitedIds = existing.Select(coauthor => coauthor.UserId).ToHashSet();
+            foreach (var userId in userIds.Where(id => !reinvitedIds.Contains(id)))
+            {
+                await database.TrackCoauthors.AddAsync(new TrackCoauthor
+                {
+                    TrackId = request.TrackId,
+                    UserId = userId,
+                    InvitedAt = now
+                }, cancellationToken);
+            }
+
+            var saved = await database.TrySaveChangesAsync(
+                AppErrors.Conflict("Coauthor.AlreadyInvited", "A user was already invited to this track."), cancellationToken);
+            if (saved.IsError)
+                return saved.Errors;
+
+            logger.LogInformation("Owner {OwnerId} invited {Count} coauthors to track {TrackId}", request.OwnerId, userIds.Count, request.TrackId);
+
+            return await database.TrackCoauthors
+                .AsNoTracking()
+                .Where(coauthor => coauthor.TrackId == request.TrackId)
+                .OrderBy(coauthor => coauthor.InvitedAt)
+                .ThenBy(coauthor => coauthor.UserId)
+                .Select(coauthor => new TrackCoauthorInviteReference(coauthor.UserId, coauthor.User.Name, coauthor.Status))
+                .ToListAsync(cancellationToken);
+        }
+    }
+}

backend/Core/Musify.Application/Coauthors/RemoveCoauthor.cs

@@ -0,0 +1,47 @@
+using ErrorOr;
+using Mediator;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging;
+using Musify.Application.Contracts;
+using Musify.Application.Shared;
+using Musify.Domain.ValueObjects;
+
+namespace Musify.Application.Coauthors
+{
+    public record RemoveCoauthorCommand(long UserId, Guid TrackId, long CoauthorUserId)
+        : ICommand<ErrorOr<Success>>;
+
+    public class RemoveCoauthorCommandHandler(
+        IDatabase database,
+        ILogger<RemoveCoauthorCommandHandler> logger)
+        : ICommandHandler<RemoveCoauthorCommand, ErrorOr<Success>>
+    {
+        public async ValueTask<ErrorOr<Success>> Handle(RemoveCoauthorCommand request, CancellationToken cancellationToken)
+        {
+            var ownerUserId = await database.Tracks
+                .AsNoTracking()
+                .Where(track => track.Id == request.TrackId && track.LifeCycleStatus == LifeCycleStatus.Active)
+                .Select(track => (long?)track.OwnerUserId)
+                .SingleOrDefaultAsync(cancellationToken);
+
+            if (ownerUserId == null)
+                return AppErrors.NotFound("Track", request.TrackId);
+
+            if (ownerUserId != request.UserId && request.CoauthorUserId != request.UserId)
+                return AppErrors.Forbidden("Track", request.TrackId);
+
+            var coauthor = await database.TrackCoauthors
+                .SingleOrDefaultAsync(c => c.TrackId == request.TrackId && c.UserId == request.CoauthorUserId, cancellationToken);
+            if (coauthor == null)
+                return AppErrors.NotFound("Coauthor", request.CoauthorUserId);
+
+            database.TrackCoauthors.Remove(coauthor);
+            await database.SaveChangesAsync(cancellationToken);
+
+            logger.LogInformation("User {UserId} removed coauthor {CoauthorUserId} from track {TrackId}",
+                request.UserId, request.CoauthorUserId, request.TrackId);
+
+            return Result.Success;
+        }
+    }
+}

backend/Core/Musify.Application/Coauthors/RespondToCoauthorInvitation.cs

@@ -0,0 +1,44 @@
+using ErrorOr;
+using Mediator;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging;
+using Musify.Application.Contracts;
+using Musify.Application.Shared;
+using Musify.Domain.ValueObjects;
+
+namespace Musify.Application.Coauthors
+{
+    public record RespondToCoauthorInvitationCommand(long UserId, Guid InvitationId, bool Accept)
+        : ICommand<ErrorOr<Success>>;
+
+    public class RespondToCoauthorInvitationCommandHandler(
+        IDatabase database,
+        ILogger<RespondToCoauthorInvitationCommandHandler> logger)
+        : ICommandHandler<RespondToCoauthorInvitationCommand, ErrorOr<Success>>
+    {
+        public async ValueTask<ErrorOr<Success>> Handle(RespondToCoauthorInvitationCommand request, CancellationToken cancellationToken)
+        {
+            var invitation = await database.TrackCoauthors
+                .Include(coauthor => coauthor.Track)
+                .SingleOrDefaultAsync(coauthor => coauthor.Id == request.InvitationId, cancellationToken);
+
+            if (invitation == null || invitation.Track.LifeCycleStatus != LifeCycleStatus.Active)
+                return AppErrors.NotFound("CoauthorInvitation", request.InvitationId);
+
+            if (invitation.UserId != request.UserId)
+                return AppErrors.Forbidden("CoauthorInvitation", request.InvitationId);
+
+            if (invitation.Status != CoauthorStatus.Pending)
+                return AppErrors.Conflict("CoauthorInvitation.NotPending", "The invitation was already answered.");
+
+            invitation.Status = request.Accept ? CoauthorStatus.Accepted : CoauthorStatus.Rejected;
+            invitation.RespondedAt = DateTime.UtcNow;
+            await database.SaveChangesAsync(cancellationToken);
+
+            logger.LogInformation("User {UserId} {Action} coauthor invitation {InvitationId}",
+                request.UserId, request.Accept ? "accepted" : "rejected", request.InvitationId);
+
+            return Result.Success;
+        }
+    }
+}

backend/Core/Musify.Application/Coauthors/Responses/CoauthorInvitationResponse.cs

@@ -0,0 +1,10 @@
+namespace Musify.Application.Coauthors.Responses
+{
+    public record CoauthorInvitationResponse(
+        Guid Id,
+        Guid TrackId,
+        string TrackTitle,
+        string? Artist,
+        long OwnerUserId,
+        DateTime InvitedAt);
+}

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

@@ -83,7 +83,6 @@ namespace Musify.Application.Configuration
 
     public static class PictureSizeParser
     {
-        /// <summary>Parses the <c>size</c> query value; anything unknown means <see cref="PictureSize.Medium"/>.</summary>
         public static PictureSize Parse(string? value) =>
             Enum.TryParse<PictureSize>(value, ignoreCase: true, out var size) && Enum.IsDefined(size)
                 ? size

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

@@ -10,10 +10,10 @@ namespace Musify.Application.Configuration
         public int UploadUrlExpiresInSeconds { get; set; } = 120;
 
         [Range(1, 100)]
-        public int MaxActiveUploadIntentsPerUser { get; set; } = 5;
+        public int MaxActiveUploadIntentsPerUser { get; set; } = 50;
 
         [Range(1, long.MaxValue)]
-        public long MaxActiveUploadBytesPerUser { get; set; } = 200L * 1024 * 1024;
+        public long MaxActiveUploadBytesPerUser { get; set; } = 1024L * 1024 * 1024;
 
         [Range(1, long.MaxValue)]
         public long MaxUploadBytes { get; set; } = 100L * 1024 * 1024;

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

@@ -32,6 +32,8 @@ namespace Musify.Application.Contracts
 
         public DbSet<UserFollow> UserFollows { get; }
 
+        public DbSet<TrackCoauthor> TrackCoauthors { get; }
+
         public Task<IDatabaseTransaction> BeginTransactionAsync(System.Data.IsolationLevel isolationLevel, CancellationToken cancellationToken);
 
         public DbSet<TEntity> Set<TEntity>() where TEntity : class;

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

@@ -2,7 +2,6 @@ namespace Musify.Application.Contracts
 {
     public interface IStorageService
     {
-        /// <summary>Opens an object for reading, or returns null when it does not exist.</summary>
         public Task<Stream?> GetFileAsync(string bucket, string key, CancellationToken cancellationToken);
 
         public Task<ObjectMetaData?> HeadObjectAsync(string bucket, string key, CancellationToken cancellationToken);

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

@@ -4,11 +4,11 @@ namespace Musify.Application.Events
 {
     public record CreateTrackResourcesEvent(
         Guid TrackId,
-        Guid PictureIntentId,
+        Guid? PictureIntentId,
         Guid AudioIntentId,
         string Bucket,
-        string PictureSourceKey,
+        string? PictureSourceKey,
-        string PictureDestinationKey,
+        string? PictureDestinationKey,
         string AudioSourceKey,
         string AudioDestinationKey,
         string AudioProcessedFolderKey,

backend/Core/Musify.Application/Genres/GetAvailableGenres.cs

@@ -11,7 +11,7 @@ namespace Musify.Application.Genres
     {
         public ValueTask<IReadOnlyList<AvailableGenreResponse>> Handle(GetAvailableGenresQuery request, CancellationToken cancellationToken)
         {
-            var all = Enum.GetValues<Genre>();
+            var all = Enum.GetValues<Genre>().Where(genre => genre != Genre.None).ToArray();
 
             IReadOnlyList<AvailableGenreResponse> result = all
                 .Select(genre => new AvailableGenreResponse(

backend/Core/Musify.Application/Genres/GetGenres.cs

@@ -15,7 +15,7 @@ namespace Musify.Application.Genres
         {
             var rows = await database.TrackTags
                 .AsNoTracking()
-                .Where(tag => tag.Track.LifeCycleStatus == LifeCycleStatus.Active)
+                .Where(tag => tag.Track.LifeCycleStatus == LifeCycleStatus.Active && tag.Track.IsPublished)
                 .GroupBy(tag => tag.Tag)
                 .Select(group => new { Genre = group.Key, TrackCount = group.Select(tag => tag.TrackId).Distinct().Count() })
                 .ToListAsync(cancellationToken);

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

@@ -20,7 +20,7 @@ namespace Musify.Application.Likes
         {
             return await database.TrackLikes
                 .AsNoTracking()
-                .Where(like => like.UserId == request.UserId && like.Track.LifeCycleStatus == LifeCycleStatus.Active)
+                .Where(like => like.UserId == request.UserId && like.Track.LifeCycleStatus == LifeCycleStatus.Active && like.Track.IsPublished)
                 .OrderByDescending(like => like.CreatedAt)
                 .ThenBy(like => like.Id)
                 .Select(like => like.Track)

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

@@ -21,7 +21,7 @@ namespace Musify.Application.Likes
         {
             var trackExists = await database.Tracks
                 .AsNoTracking()
-                .AnyAsync(t => t.Id == request.TrackId && t.LifeCycleStatus == LifeCycleStatus.Active, cancellationToken);
+                .AnyAsync(t => t.Id == request.TrackId && t.LifeCycleStatus == LifeCycleStatus.Active && t.IsPublished, cancellationToken);
             if (!trackExists)
                 return AppErrors.NotFound("Track", request.TrackId);
 
@@ -44,7 +44,6 @@ namespace Musify.Application.Likes
                 nowLiked = true;
             }
 
-            // A concurrent double click can hit the unique index; the outcome is already in place, so treat it as a no-op.
             var saved = await database.TrySaveChangesAsync(
                 AppErrors.Conflict("TrackLike.Duplicate", "Track is already liked."), cancellationToken);
             if (saved.IsError)

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

@@ -25,7 +25,7 @@ namespace Musify.Application.Mixes
 
             var libraryTrackIds = await database.Tracks
                 .AsNoTracking()
-                .Where(track => track.OwnerUserId == userId && track.LifeCycleStatus == LifeCycleStatus.Active)
+                .Where(track => track.OwnerUserId == userId && track.LifeCycleStatus == LifeCycleStatus.Active && track.IsPublished)
                 .Select(track => track.Id)
                 .ToListAsync(cancellationToken);
 

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

@@ -25,7 +25,13 @@ namespace Musify.Application.Mixes
                 mix => mix.Id,
                 mix => mix.Items.OrderBy(item => item.Position).ToList());
 
-            var coverItems = orderedItemsByMix.Values
+            var visibleTrackIds = await MixItemMapper.VisibleTrackIdsAsync(
+                database, orderedItemsByMix.Values.SelectMany(items => items), cancellationToken);
+            var visibleItemsByMix = orderedItemsByMix.ToDictionary(
+                entry => entry.Key,
+                entry => entry.Value.Where(item => visibleTrackIds.Contains(item.TrackId)).ToList());
+
+            var coverItems = visibleItemsByMix.Values
                 .SelectMany(items => items.Take(MixApplicationResponse.CoverItemCount))
                 .ToList();
             var coverResponses = (await MixItemMapper.ToResponsesAsync(database, coverItems, cancellationToken))
@@ -35,7 +41,7 @@ namespace Musify.Application.Mixes
             var responses = new List<MixApplicationResponse>(mixes.Count);
             foreach (var mix in mixes)
             {
-                var orderedItems = orderedItemsByMix[mix.Id];
+                var orderedItems = visibleItemsByMix[mix.Id];
                 var covers = orderedItems
                     .Take(MixApplicationResponse.CoverItemCount)
                     .Where(item => coverResponses.ContainsKey(item.TrackId))

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

@@ -9,6 +9,22 @@ namespace Musify.Application.Mixes
 
     internal static class MixItemMapper
     {
+        public static async Task<HashSet<Guid>> VisibleTrackIdsAsync(
+            IDatabase database,
+            IEnumerable<MixItem> items,
+            CancellationToken cancellationToken)
+        {
+            var trackIds = items.Select(item => item.TrackId).Distinct().ToList();
+
+            var visible = await database.Tracks
+                .AsNoTracking()
+                .Where(track => trackIds.Contains(track.Id) && track.LifeCycleStatus == LifeCycleStatus.Active && track.IsPublished)
+                .Select(track => track.Id)
+                .ToListAsync(cancellationToken);
+
+            return [.. visible];
+        }
+
         public static async Task<List<MixItemApplicationResponse>> ToResponsesAsync(
             IDatabase database,
             IReadOnlyList<MixItem> orderedItems,
@@ -19,7 +35,7 @@ namespace Musify.Application.Mixes
             var tracksById = await database.Tracks
                 .AsNoTracking()
                 .Include(track => track.Owner)
-                .Where(track => trackIds.Contains(track.Id) && track.LifeCycleStatus == LifeCycleStatus.Active)
+                .Where(track => trackIds.Contains(track.Id) && track.LifeCycleStatus == LifeCycleStatus.Active && track.IsPublished)
                 .Select(track => new { Track = track, ListensCount = track.ListeningHistories.Count(l => l.IsCounted) })
                 .ToDictionaryAsync(x => x.Track.Id, cancellationToken);
 

backend/Core/Musify.Application/Pictures/GetCover.cs

@@ -35,10 +35,7 @@ namespace Musify.Application.Pictures
         {
             var (source, routes) = request.Owner switch
             {
-                CoverOwner.Track => (await database.Tracks.AsNoTracking()
+                CoverOwner.Track => await FindTrackSourceAsync(request.Id, cancellationToken),
-                    .Where(t => t.Id == request.Id && t.LifeCycleStatus == LifeCycleStatus.Active)
-                    .Select(t => new CoverSource(t.OwnerUserId, t.Pictures.OriginalName, t.Pictures.SmallName, t.Pictures.MediumName, t.Pictures.LargeName))
-                    .SingleOrDefaultAsync(cancellationToken), trackConfiguration.Routes),
                 CoverOwner.Album => (await database.Albums.AsNoTracking()
                     .Where(a => a.Id == request.Id && a.LifeCycleStatus == LifeCycleStatus.Active && a.Pictures != null)
                     .Select(a => new CoverSource(a.OwnerUserId, a.Pictures!.OriginalName, a.Pictures.SmallName, a.Pictures.MediumName, a.Pictures.LargeName))
@@ -60,7 +57,6 @@ namespace Musify.Application.Pictures
                 _ => source.Medium
             };
 
-            // The resized files only exist once processing has finished; until then serve the original.
             var (name, key) = !string.IsNullOrEmpty(resizedName)
                 ? (resizedName, routes.BuildPicturePath(request.Size, resizedName))
                 : !string.IsNullOrEmpty(source.Original)
@@ -72,5 +68,34 @@ namespace Musify.Application.Pictures
 
             return new CoverLocation(storageConfiguration.Bucket, key, MimeUtility.GetMimeMapping(name));
         }
+
+        private async Task<(CoverSource? Source, PictureRoutes Routes)> FindTrackSourceAsync(Guid trackId, CancellationToken cancellationToken)
+        {
+            var track = await database.Tracks.AsNoTracking()
+                .Where(t => t.Id == trackId && t.LifeCycleStatus == LifeCycleStatus.Active)
+                .Select(t => new
+                {
+                    Own = new CoverSource(t.OwnerUserId, t.Pictures.OriginalName, t.Pictures.SmallName, t.Pictures.MediumName, t.Pictures.LargeName),
+                    Album = t.AlbumTracks
+                        .Where(albumTrack => albumTrack.Album.LifeCycleStatus == LifeCycleStatus.Active && albumTrack.Album.Pictures != null)
+                        .OrderBy(albumTrack => albumTrack.AddedAt)
+                        .ThenBy(albumTrack => albumTrack.AlbumId)
+                        .Select(albumTrack => new CoverSource(
+                            albumTrack.Album.OwnerUserId,
+                            albumTrack.Album.Pictures!.OriginalName,
+                            albumTrack.Album.Pictures.SmallName,
+                            albumTrack.Album.Pictures.MediumName,
+                            albumTrack.Album.Pictures.LargeName))
+                        .FirstOrDefault()
+                })
+                .SingleOrDefaultAsync(cancellationToken);
+
+            if (track == null)
+                return (null, trackConfiguration.Routes);
+
+            return string.IsNullOrEmpty(track.Own.Original) && track.Album != null
+                ? (track.Album, albumConfiguration.Routes)
+                : (track.Own, trackConfiguration.Routes);
+        }
     }
 }

backend/Core/Musify.Application/Pictures/PictureSourceChange.cs

@@ -7,7 +7,6 @@ using Musify.Domain.ValueObjects;
 
 namespace Musify.Application.Pictures
 {
-    /// <summary>What an album or playlist needs to switch to a freshly uploaded picture.</summary>
     public sealed record PreparedPicture(UploadIntent Intent, EntityPictures Pictures, string FinalKey, ImageSizes Sizes);
 
     public static class PictureSourceChange

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

@@ -0,0 +1,81 @@
+using ErrorOr;
+using Mediator;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging;
+using Musify.Application.Albums.Responses;
+using Musify.Application.Contracts;
+using Musify.Application.PlayLists.Responses;
+using Musify.Application.Shared;
+using Musify.Domain.Entities;
+using Musify.Domain.ValueObjects;
+
+namespace Musify.Application.PlayLists
+{
+    public record AddAlbumToPlayListCommand(long UserId, Guid PlayListId, Guid AlbumId)
+        : ICommand<ErrorOr<AddAlbumToPlayListResponse>>;
+
+    public class AddAlbumToPlayListCommandHandler(
+        IDatabase database,
+        ILogger<AddAlbumToPlayListCommandHandler> logger)
+        : ICommandHandler<AddAlbumToPlayListCommand, ErrorOr<AddAlbumToPlayListResponse>>
+    {
+        public async ValueTask<ErrorOr<AddAlbumToPlayListResponse>> Handle(AddAlbumToPlayListCommand request, CancellationToken cancellationToken)
+        {
+            var playList = await database.PlayLists.FindOwnedAsync(request.PlayListId, request.UserId, cancellationToken);
+            if (playList.IsError)
+                return playList.Errors;
+
+            var albumExists = await database.Albums
+                .AsNoTracking()
+                .Active()
+                .AnyAsync(album => album.Id == request.AlbumId, cancellationToken);
+            if (!albumExists)
+                return AppErrors.NotFound("Album", request.AlbumId);
+
+            var albumTrackIds = await database.AlbumHasTracks
+                .AsNoTracking()
+                .Where(albumTrack => albumTrack.AlbumId == request.AlbumId && albumTrack.Track.LifeCycleStatus == LifeCycleStatus.Active && albumTrack.Track.IsPublished)
+                .OrderBy(albumTrack => albumTrack.TrackNumber)
+                .Select(albumTrack => albumTrack.TrackId)
+                .ToListAsync(cancellationToken);
+
+            var playListTracksQuery = database.PlayListHasTracks
+                .Where(link => link.PlayListId == request.PlayListId);
+
+            var existingTrackIds = (await playListTracksQuery
+                .Select(link => link.TrackId)
+                .ToListAsync(cancellationToken)).ToHashSet();
+
+            var newTrackIds = albumTrackIds
+                .Where(trackId => !existingTrackIds.Contains(trackId))
+                .ToList();
+
+            if (newTrackIds.Count == 0)
+                return new AddAlbumToPlayListResponse(0);
+
+            var nextPosition = existingTrackIds.Count > 0
+               ? await playListTracksQuery.MaxAsync(link => link.Position, cancellationToken) + 1
+                : 0;
+
+            foreach (var trackId in newTrackIds)
+            {
+                await database.PlayListHasTracks.AddAsync(new PlayListHasTrack
+                {
+                    PlayListId = request.PlayListId,
+                    TrackId = trackId,
+                    Position = nextPosition++
+                }, cancellationToken);
+            }
+
+            var saved = await database.TrySaveChangesAsync(
+                AppErrors.Conflict("PlayList.ConcurrentChange", "The playlist changed while adding tracks. Try again."), cancellationToken);
+            if (saved.IsError)
+                return saved.Errors;
+
+            logger.LogInformation("Added {Count} tracks from album {AlbumId} to playlist {PlayListId}",
+                newTrackIds.Count, request.AlbumId, request.PlayListId);
+
+            return new AddAlbumToPlayListResponse(newTrackIds.Count);
+        }
+    }
+}

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

@@ -9,7 +9,6 @@ using Musify.Domain.ValueObjects;
 
 namespace Musify.Application.PlayLists
 {
-    /// <summary>Appends tracks to a playlist in the given order, skipping the ones it already has.</summary>
     public record AddTracksToPlayListCommand(long UserId, Guid PlayListId, IReadOnlyList<Guid> TrackIds)
         : ICommand<ErrorOr<Success>>;
 
@@ -28,7 +27,7 @@ namespace Musify.Application.PlayLists
 
             var existingIds = await database.Tracks
                 .AsNoTracking()
-                .Where(track => requestedIds.Contains(track.Id) && track.LifeCycleStatus == LifeCycleStatus.Active)
+                .Where(track => requestedIds.Contains(track.Id) && track.LifeCycleStatus == LifeCycleStatus.Active && track.IsPublished)
                 .Select(track => track.Id)
                 .ToListAsync(cancellationToken);
 
@@ -46,10 +45,12 @@ namespace Musify.Application.PlayLists
             if (toAdd.Count == 0)
                 return Result.Success;
 
-            // Playlist positions are internal indexes, so they start at 0.
+            var playListTracksQuery = database.PlayListHasTracks
-            var nextPosition = (await database.PlayListHasTracks
+                .Where(link => link.PlayListId == request.PlayListId);
-                .Where(link => link.PlayListId == request.PlayListId)
+
-                .MaxAsync(link => (int?)link.Position, cancellationToken) ?? -1) + 1;
+            var nextPosition = await playListTracksQuery.AnyAsync(cancellationToken)
+               ? await playListTracksQuery.MaxAsync(link => link.Position, cancellationToken) + 1
+                : 0;
 
             foreach (var trackId in toAdd)
             {

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

@@ -39,10 +39,10 @@ namespace Musify.Application.PlayLists
                 return AppErrors.NotFound("User", request.UserId);
 
             PreparedPicture? picture = null;
-            if (request.PictureIntentId is { } intentId)
+            if (request.PictureIntentId.HasValue)
             {
                 var prepared = await PictureSourceChange.PrepareAsync(
-                    uploadIntentValidator, intentId, request.UserId, UploadIntentPurpose.PlayListPicture, playListConfiguration, cancellationToken);
+                    uploadIntentValidator, request.PictureIntentId.Value, request.UserId, UploadIntentPurpose.PlayListPicture, playListConfiguration, cancellationToken);
                 if (prepared.IsError)
                     return prepared.Errors;
 

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

@@ -31,7 +31,7 @@ namespace Musify.Application.PlayLists
 
             return await database.PlayListHasTracks
                 .AsNoTracking()
-                .Where(playListTrack => playListTrack.PlayListId == request.PlayListId && playListTrack.Track.LifeCycleStatus == LifeCycleStatus.Active)
+                .Where(playListTrack => playListTrack.PlayListId == request.PlayListId && playListTrack.Track.LifeCycleStatus == LifeCycleStatus.Active && playListTrack.Track.IsPublished)
                 .OrderBy(playListTrack => playListTrack.Position)
                 .ThenBy(playListTrack => playListTrack.Id)
                 .Select(playListTrack => playListTrack.Track)

backend/Core/Musify.Application/PlayLists/Responses/AddAlbumToPlayListResponse.cs

@@ -0,0 +1,4 @@
+namespace Musify.Application.PlayLists.Responses
+{
+    public record AddAlbumToPlayListResponse(int AddedCount);
+}

backend/Core/Musify.Application/PlayLists/Responses/PlayListProjections.cs

@@ -25,14 +25,15 @@ namespace Musify.Application.PlayLists.Responses
                 playList.CreatedAt,
                 playList.UpdatedAt,
                 playList.PlayListTracks
+                    .Where(playListTrack => playListTrack.Track.LifeCycleStatus == LifeCycleStatus.Active && playListTrack.Track.IsPublished)
                     .OrderBy(playListTrack => playListTrack.Position)
                     .Take(CoverTrackCount)
                     .Select(playListTrack => playListTrack.TrackId)
                     .ToList(),
                 playList.OwnerUserId,
-                playList.PlayListTracks.Count(playListTrack => playListTrack.Track.LifeCycleStatus == LifeCycleStatus.Active),
+                playList.PlayListTracks.Count(playListTrack => playListTrack.Track.LifeCycleStatus == LifeCycleStatus.Active && playListTrack.Track.IsPublished),
                 playList.PlayListTracks
-                    .Where(playListTrack => playListTrack.Track.LifeCycleStatus == LifeCycleStatus.Active)
+                    .Where(playListTrack => playListTrack.Track.LifeCycleStatus == LifeCycleStatus.Active && playListTrack.Track.IsPublished)
                     .Sum(playListTrack => playListTrack.Track.DurationSeconds)));
     }
 }

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

@@ -2,12 +2,8 @@ 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.Pictures;
 using Musify.Application.PlayLists.Responses;
-using Musify.Application.Services;
 using Musify.Application.Shared;
 using Musify.Domain.ValueObjects;
 
@@ -16,18 +12,14 @@ namespace Musify.Application.PlayLists
     public record UpdatePlayListCommand(
         long UserId,
         Guid PlayListId,
-        string? NewName,
+        string NewName,
         string? NewDescription,
-        Guid? NewPictureIntentId,
+        PlayListVisibility NewVisibility)
-        PlayListVisibility? NewVisibility = null)
         : ICommand<ErrorOr<PlayListApplicationResponse>>;
 
     public class UpdatePlayListCommandHandler(
-        IEventBus eventBus,
         IDatabase database,
-        UploadIntentValidator uploadIntentValidator,
+        ILogger<UpdatePlayListCommandHandler> logger)
-        ILogger<UpdatePlayListCommandHandler> logger,
-        PlayListConfiguration playListConfiguration)
         : ICommandHandler<UpdatePlayListCommand, ErrorOr<PlayListApplicationResponse>>
     {
         public async ValueTask<ErrorOr<PlayListApplicationResponse>> Handle(UpdatePlayListCommand request, CancellationToken cancellationToken)
@@ -38,34 +30,10 @@ namespace Musify.Application.PlayLists
 
             var playList = found.Value;
 
-            if (!string.IsNullOrWhiteSpace(request.NewName))
-            {
             playList.Name = request.NewName.Trim();
             playList.NormalizedName = TextNormalizer.Normalize(request.NewName);
-            }
-
-            // null means "unchanged"; a blank description clears it.
-            if (request.NewDescription != null)
             playList.Description = string.IsNullOrWhiteSpace(request.NewDescription) ? null : request.NewDescription.Trim();
-
+            playList.Visibility = request.NewVisibility;
-            if (request.NewVisibility is { } visibility)
-                playList.Visibility = visibility;
-
-            if (request.NewPictureIntentId is { } intentId)
-            {
-                var prepared = await PictureSourceChange.PrepareAsync(
-                    uploadIntentValidator, intentId, request.UserId, UploadIntentPurpose.PlayListPicture, playListConfiguration, cancellationToken);
-                if (prepared.IsError)
-                    return prepared.Errors;
-
-                var picture = prepared.Value;
-                playList.Pictures = picture.Pictures;
-
-                await eventBus.PublishAsync(
-                    new UpdatePlayListPictureSourceEvent(
-                        playList.Id, picture.Intent.Id, picture.Intent.Bucket, picture.Intent.Key, picture.FinalKey, picture.Sizes),
-                    cancellationToken);
-            }
 
             await database.SaveChangesAsync(cancellationToken);
 

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

@@ -0,0 +1,59 @@
+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.Pictures;
+using Musify.Application.PlayLists.Responses;
+using Musify.Application.Services;
+using Musify.Application.Shared;
+using Musify.Domain.ValueObjects;
+
+namespace Musify.Application.PlayLists
+{
+    public record UpdatePlayListPictureCommand(long UserId, Guid PlayListId, Guid PictureIntentId)
+        : ICommand<ErrorOr<PlayListApplicationResponse>>;
+
+    public class UpdatePlayListPictureCommandHandler(
+        IEventBus eventBus,
+        IDatabase database,
+        UploadIntentValidator uploadIntentValidator,
+        ILogger<UpdatePlayListPictureCommandHandler> logger,
+        PlayListConfiguration playListConfiguration)
+        : ICommandHandler<UpdatePlayListPictureCommand, ErrorOr<PlayListApplicationResponse>>
+    {
+        public async ValueTask<ErrorOr<PlayListApplicationResponse>> Handle(UpdatePlayListPictureCommand request, CancellationToken cancellationToken)
+        {
+            var found = await database.PlayLists.FindOwnedAsync(request.PlayListId, request.UserId, cancellationToken);
+            if (found.IsError)
+                return found.Errors;
+
+            var playList = found.Value;
+
+            var prepared = await PictureSourceChange.PrepareAsync(
+                uploadIntentValidator, request.PictureIntentId, request.UserId, UploadIntentPurpose.PlayListPicture, playListConfiguration, cancellationToken);
+            if (prepared.IsError)
+                return prepared.Errors;
+
+            var picture = prepared.Value;
+            playList.Pictures = picture.Pictures;
+
+            await eventBus.PublishAsync(
+                new UpdatePlayListPictureSourceEvent(
+                    playList.Id, picture.Intent.Id, picture.Intent.Bucket, picture.Intent.Key, picture.FinalKey, picture.Sizes),
+                cancellationToken);
+
+            await database.SaveChangesAsync(cancellationToken);
+
+            logger.LogInformation("Updated picture of playlist {PlayListId}", playList.Id);
+
+            return await database.PlayLists
+                .AsNoTracking()
+                .Where(p => p.Id == playList.Id)
+                .SelectResponse()
+                .SingleAsync(cancellationToken);
+        }
+    }
+}

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

@@ -4,7 +4,6 @@ using Musify.Application.Tracks.Responses;
 
 namespace Musify.Application.Services
 {
-    /// <summary>Builds the stream URL and signed ticket for a processed track. It never touches the database.</summary>
     public sealed class TrackStreamIssuer(
         IStreamTicketService ticketService,
         TrackConfiguration trackConfiguration,

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

@@ -15,7 +15,8 @@ namespace Musify.Application.Services
         PictureRoutes Routes,
         string FileType,
         string ContentType,
-        long? ExpectedSizeBytes);
+        long? ExpectedSizeBytes,
+        int? SharedKeyGroup = null);
 
     public sealed record IssuedUpload(
         Guid IntentId,
@@ -24,7 +25,6 @@ namespace Musify.Application.Services
         string ContentType,
         string UploadUrl);
 
-    /// <summary>Issues pre-signed upload URLs and the upload intents that track them, checking the user quota first.</summary>
     public sealed class UploadIntentIssuer(
         IDatabase database,
         IStorageService storageService,
@@ -44,11 +44,15 @@ namespace Musify.Application.Services
             if (!userExists)
                 return AppErrors.NotFound("User", userId);
 
+            var sharedKeys = new Dictionary<int, string>();
             var planned = requests
                 .Select(request =>
                 {
                     var objectName = $"{Guid.NewGuid()}.{request.FileType.TrimStart('.').ToLowerInvariant()}";
                     var key = request.Routes.BuildTempPath(uploadIntentConfiguration.TempRootPrefix, userId, objectName);
+                    if (request.SharedKeyGroup is { } group)
+                        key = sharedKeys.TryAdd(group, key) ? key : sharedKeys[group];
+
                     var size = request.ExpectedSizeBytes ?? DefaultSize(request.Purpose);
                     return (Request: request, ObjectName: objectName, Key: key, Size: size);
                 })

backend/Core/Musify.Application/Shared/OwnershipExtensions.cs

@@ -7,10 +7,6 @@ namespace Musify.Application.Shared
 {
     public static class OwnershipExtensions
     {
-        /// <summary>
-        /// Loads an active, tracked entity owned by <paramref name="userId"/>: NotFound when it is missing
-        /// or not active, Forbidden when someone else owns it.
-        /// </summary>
         public static async Task<ErrorOr<T>> FindOwnedAsync<T>(
             this DbSet<T> set, Guid id, long userId, CancellationToken cancellationToken)
             where T : class, IOwnedEntity, IHasLifeCycle

backend/Core/Musify.Application/Shared/Pagination.cs

@@ -18,7 +18,6 @@ namespace Musify.Application.Shared
 
     public static class PaginationExtensions
     {
-        /// <summary>Counts and pages the same (already filtered, ordered and projected) query.</summary>
         public static async Task<PaginatedResponse<T>> ToPaginatedAsync<T>(
             this IQueryable<T> query, PageRequest page, CancellationToken cancellationToken)
         {

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

@@ -16,7 +16,7 @@ namespace Musify.Application.Tracks
     public record CreateTrackCommand(
         long UserId,
         string Title,
-        Guid PictureIntentId,
+        Guid? PictureIntentId,
         Guid AudioIntentId,
         IReadOnlyCollection<Genre> Tags,
         bool IsExplicit = false)
@@ -45,20 +45,27 @@ namespace Musify.Application.Tracks
             if (request.PictureIntentId == request.AudioIntentId)
                 return Error.Validation(description: "Picture and audio must use different upload intents.");
 
+            UploadIntent? pictureIntent = null;
+            if (request.PictureIntentId is { } pictureIntentId)
+            {
                 var pictureValidation = await uploadIntentValidator.ValidateAndLoadAsync(
-                request.PictureIntentId, request.UserId, UploadIntentPurpose.TrackPicture, cancellationToken);
+                    pictureIntentId, request.UserId, UploadIntentPurpose.TrackPicture, cancellationToken);
                 if (pictureValidation.IsError)
                     return pictureValidation.Errors;
 
+                pictureIntent = pictureValidation.Value;
+            }
+
             var audioValidation = await uploadIntentValidator.ValidateAndLoadAsync(
                 request.AudioIntentId, request.UserId, UploadIntentPurpose.TrackAudio, cancellationToken);
             if (audioValidation.IsError)
                 return audioValidation.Errors;
 
-            var pictureIntent = pictureValidation.Value;
             var audioIntent = audioValidation.Value;
 
-            var finalPictureKey = trackConfiguration.Routes.BuildOriginalPicturePath(request.UserId, pictureIntent.ObjectName);
+            var finalPictureKey = pictureIntent == null
+                ? null
+                : trackConfiguration.Routes.BuildOriginalPicturePath(request.UserId, pictureIntent.ObjectName);
             var finalAudioKey = trackConfiguration.Routes.BuildOriginalAudioPath(request.UserId, audioIntent.ObjectName);
             var audioProcessedFolderKey = trackConfiguration.Routes.BuildProcessedAudioPath(Guid.NewGuid().ToString());
 
@@ -71,11 +78,11 @@ namespace Musify.Application.Tracks
                 IsExplicit = request.IsExplicit,
                 Pictures = new TrackPictures
                 {
-                    OriginalName = pictureIntent.ObjectName,
+                    OriginalName = pictureIntent?.ObjectName,
                     SmallName = trackConfiguration.Routes.PresetSmallPicture,
                     MediumName = trackConfiguration.Routes.PresetMediumPicture,
                     LargeName = trackConfiguration.Routes.PresetLargePicture,
-                    ProcessingStatus = ProcessingStatus.Pending
+                    ProcessingStatus = pictureIntent == null ? ProcessingStatus.Completed : ProcessingStatus.Pending
                 },
                 Audio = new TrackAudio
                 {
@@ -90,15 +97,14 @@ namespace Musify.Application.Tracks
 
             await database.Tracks.AddAsync(trackEntity, cancellationToken);
 
-
             var sizes = trackConfiguration.PicturesSizes.ToImageSizes(trackConfiguration.Routes);
             await eventBus.PublishAsync(
                 new CreateTrackResourcesEvent(
                     trackEntity.Id,
-                    pictureIntent.Id,
+                    pictureIntent?.Id,
                     audioIntent.Id,
-                    pictureIntent.Bucket,
+                    audioIntent.Bucket,
-                    pictureIntent.Key,
+                    pictureIntent?.Key,
                     finalPictureKey,
                     audioIntent.Key,
                     finalAudioKey,

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

@@ -0,0 +1,60 @@
+using ErrorOr;
+using Mediator;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging;
+using Musify.Application.Contracts;
+using Musify.Application.Events;
+using Musify.Application.Shared;
+using Musify.Application.Tracks.Responses;
+using Musify.Domain.ValueObjects;
+
+namespace Musify.Application.Tracks
+{
+    public record DeleteTracksCommand(long UserId, IReadOnlyList<Guid> TrackIds)
+        : ICommand<ErrorOr<DeleteTracksResponse>>;
+
+    public class DeleteTracksCommandHandler(
+        IDatabase database,
+        IEventBus eventBus,
+        ILogger<DeleteTracksCommandHandler> logger)
+        : ICommandHandler<DeleteTracksCommand, ErrorOr<DeleteTracksResponse>>
+    {
+        public async ValueTask<ErrorOr<DeleteTracksResponse>> Handle(DeleteTracksCommand request, CancellationToken cancellationToken)
+        {
+            var requestedIds = request.TrackIds.Distinct().ToList();
+
+            var tracks = await database.Tracks
+                .Where(track => requestedIds.Contains(track.Id) && track.LifeCycleStatus == LifeCycleStatus.Active)
+                .ToListAsync(cancellationToken);
+
+            var foreign = tracks.FirstOrDefault(track => track.OwnerUserId != request.UserId);
+            if (foreign != null)
+                return AppErrors.Forbidden("Track", foreign.Id);
+
+            var deleted = new List<Guid>();
+            var failed = new List<Guid>();
+
+            foreach (var trackId in requestedIds)
+            {
+                var track = tracks.SingleOrDefault(candidate => candidate.Id == trackId);
+                if (track == null || track.Audio.IsInProgress)
+                {
+                    failed.Add(trackId);
+                    continue;
+                }
+
+                track.LifeCycleStatus = LifeCycleStatus.Removing;
+                await eventBus.PublishAsync(new DeleteTrackEvent(track.Id, request.UserId), cancellationToken);
+                deleted.Add(trackId);
+            }
+
+            if (deleted.Count > 0)
+            {
+                await database.SaveChangesAsync(cancellationToken);
+                logger.LogInformation("Marked {Count} tracks of user {UserId} as removing", deleted.Count, request.UserId);
+            }
+
+            return new DeleteTracksResponse(deleted, failed);
+        }
+    }
+}

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

@@ -15,12 +15,11 @@ namespace Musify.Application.Tracks
         {
             return await database.ListeningHistories
                 .AsNoTracking()
-                .Include(t => t.Track.Owner)
+                .Where(t => t.UserId == query.UserId && t.IsCounted && t.Track.LifeCycleStatus == LifeCycleStatus.Active && t.Track.IsPublished)
-                .Include(t => t.Track.Tags)
-                .Where(t => t.UserId == query.UserId && t.IsCounted && t.Track.LifeCycleStatus == LifeCycleStatus.Active)
                 .OrderByDescending(t => t.ListenedAt)
                 .ThenBy(t => t.Id)
-                .Select(t => TrackApplicationResponse.FromEntity(t.Track, t.Track.ListeningHistories.Count(l => l.IsCounted)))
+                .Select(t => t.Track)
+                .SelectResponse()
                 .FirstOrDefaultAsync(cancellationToken);
         }
     }

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

@@ -27,6 +27,7 @@ namespace Musify.Application.Tracks
             var tracksById = await database.Tracks
                 .AsNoTracking()
                 .Active()
+                .WherePublished()
                 .Where(t => recentTrackIds.Contains(t.Id))
                 .SelectResponse()
                 .ToDictionaryAsync(t => t.Id, cancellationToken);

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

@@ -7,7 +7,7 @@ using Musify.Application.Tracks.Responses;
 
 namespace Musify.Application.Tracks
 {
-    public record GetTrackByIdQuery(Guid TrackId)
+    public record GetTrackByIdQuery(Guid TrackId, long? ViewerId = null)
         : IQuery<ErrorOr<TrackApplicationResponse>>;
 
     public class GetTrackByIdQueryHandler(IDatabase database)
@@ -18,6 +18,7 @@ namespace Musify.Application.Tracks
             var track = await database.Tracks
                 .AsNoTracking()
                 .Active()
+                .VisibleTo(request.ViewerId)
                 .Where(t => t.Id == request.TrackId)
                 .SelectResponse()
                 .SingleOrDefaultAsync(cancellationToken);

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

@@ -0,0 +1,40 @@
+using Mediator;
+using Microsoft.EntityFrameworkCore;
+using Musify.Application.Contracts;
+using Musify.Application.Tracks.Responses;
+using Musify.Domain.ValueObjects;
+
+namespace Musify.Application.Tracks
+{
+    public record GetTrackStatusCountsQuery(long UserId)
+        : IQuery<TrackStatusCountsResponse>;
+
+    public class GetTrackStatusCountsQueryHandler(IDatabase database)
+        : IQueryHandler<GetTrackStatusCountsQuery, TrackStatusCountsResponse>
+    {
+        public async ValueTask<TrackStatusCountsResponse> Handle(GetTrackStatusCountsQuery request, CancellationToken cancellationToken)
+        {
+            var counts = await database.Tracks
+                .AsNoTracking()
+                .Active()
+                .Where(track => track.OwnerUserId == request.UserId)
+                .GroupBy(track => new { track.Audio.TranscodeStatus, track.IsPublished })
+                .Select(group => new { group.Key.TranscodeStatus, group.Key.IsPublished, Count = group.Count() })
+                .ToListAsync(cancellationToken);
+
+            int CountOf(ProcessingStatus status) => counts.Where(c => c.TranscodeStatus == status).Sum(c => c.Count);
+
+            var published = counts.Where(c => c.IsPublished).Sum(c => c.Count);
+            var total = counts.Sum(c => c.Count);
+
+            return new TrackStatusCountsResponse(
+                total,
+                CountOf(ProcessingStatus.Pending),
+                CountOf(ProcessingStatus.Processing),
+                CountOf(ProcessingStatus.Completed),
+                CountOf(ProcessingStatus.Failed),
+                published,
+                total - published);
+        }
+    }
+}

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

@@ -17,7 +17,8 @@ namespace Musify.Application.Tracks
         {
             var tracksQuery = database.Tracks
                 .AsNoTracking()
-                .Active();
+                .Active()
+                .WherePublished();
 
             if (!string.IsNullOrWhiteSpace(request.Name))
             {

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

@@ -4,6 +4,7 @@ using Microsoft.EntityFrameworkCore;
 using Musify.Application.Contracts;
 using Musify.Application.Shared;
 using Musify.Application.Tracks.Responses;
+using Musify.Domain.ValueObjects;
 
 namespace Musify.Application.Tracks
 {
@@ -11,18 +12,33 @@ namespace Musify.Application.Tracks
         long UserId,
         string? Name,
         int PageNumber,
-        int PageSize)
+        int PageSize,
-        : IQuery<ErrorOr<PaginatedResponse<TrackApplicationResponse>>>;
+        IReadOnlyList<ProcessingStatus>? Statuses = null,
+        long? ViewerId = null,
+        bool? IsPublished = null,
+        bool? IncludeCoauthored = null)
+        : IQuery<ErrorOr<PaginatedResponse<UserTrackApplicationResponse>>>;
 
     public class GetTracksByUserIdQueryHandler(IDatabase database)
-        : IQueryHandler<GetTracksByUserIdQuery, ErrorOr<PaginatedResponse<TrackApplicationResponse>>>
+        : IQueryHandler<GetTracksByUserIdQuery, ErrorOr<PaginatedResponse<UserTrackApplicationResponse>>>
     {
-        public async ValueTask<ErrorOr<PaginatedResponse<TrackApplicationResponse>>> Handle(GetTracksByUserIdQuery request, CancellationToken cancellationToken)
+        public async ValueTask<ErrorOr<PaginatedResponse<UserTrackApplicationResponse>>> Handle(GetTracksByUserIdQuery request, CancellationToken cancellationToken)
         {
             var tracksQuery = database.Tracks
                 .AsNoTracking()
-                .Active()
+                .Active();
-                .Where(track => track.OwnerUserId == request.UserId);
+
+            var isOwnerView = request.ViewerId == request.UserId;
+            var includeCoauthored = request.IncludeCoauthored ?? !isOwnerView;
+
+            tracksQuery = includeCoauthored
+                ? tracksQuery.Where(track => track.OwnerUserId == request.UserId
+                    || track.Coauthors.Any(coauthor => coauthor.UserId == request.UserId && coauthor.Status == CoauthorStatus.Accepted))
+                : tracksQuery.Where(track => track.OwnerUserId == request.UserId);
+
+            tracksQuery = isOwnerView
+                ? tracksQuery.Where(track => track.OwnerUserId == request.UserId || track.IsPublished)
+                : tracksQuery.WherePublished();
 
             if (!string.IsNullOrWhiteSpace(request.Name))
             {
@@ -30,11 +46,27 @@ namespace Musify.Application.Tracks
                 tracksQuery = tracksQuery.Where(track => track.NormalizedTitle.Contains(normalizedName));
             }
 
-            return await tracksQuery
+            if (request.Statuses is { Count: > 0 } statuses)
+            {
+                var statusList = statuses.Distinct().ToList();
+                tracksQuery = tracksQuery.Where(track => statusList.Contains(track.Audio.TranscodeStatus));
+            }
+
+            if (request.IsPublished is { } isPublished)
+                tracksQuery = tracksQuery.Where(track => track.IsPublished == isPublished);
+
+            var page = await tracksQuery
                 .OrderByDescending(track => track.CreatedAt)
                 .ThenBy(track => track.Id)
-                .SelectResponse()
+                .SelectUserResponse(includeInvites: request.ViewerId != null)
                 .ToPaginatedAsync(new PageRequest(request.PageNumber, request.PageSize), cancellationToken);
+
+            // Invitations are private to the track owner.
+            var items = page.Items
+                .Select(track => track.OwnerUserId == request.ViewerId ? track : track with { CoauthorInvites = [] })
+                .ToList();
+
+            return page with { Items = items };
         }
     }
 }

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

@@ -7,14 +7,17 @@ using Musify.Domain.ValueObjects;
 
 namespace Musify.Application.Tracks
 {
+    public record AudioUploadSpec(string FileType, string ContentType, long? ExpectedSizeBytes = null);
+
     public record RequestTrackUploadUrlsCommand(
         long UserId,
-        string PictureFileType,
+        string? PictureFileType,
-        string PictureContentType,
+        string? PictureContentType,
-        string AudioFileType,
+        string? AudioFileType = null,
-        string AudioContentType,
+        string? AudioContentType = null,
         long? ExpectedPictureSizeBytes = null,
-        long? ExpectedAudioSizeBytes = null)
+        long? ExpectedAudioSizeBytes = null,
+        IReadOnlyList<AudioUploadSpec>? Audios = null)
         : ICommand<ErrorOr<TrackUploadUrlsResponse>>;
 
     public class RequestTrackUploadUrlsCommandHandler(
@@ -24,35 +27,75 @@ namespace Musify.Application.Tracks
         UploadIntentConfiguration uploadIntentConfiguration)
         : ICommandHandler<RequestTrackUploadUrlsCommand, ErrorOr<TrackUploadUrlsResponse>>
     {
+        private const int PictureKeyGroup = 1;
+
         public async ValueTask<ErrorOr<TrackUploadUrlsResponse>> Handle(RequestTrackUploadUrlsCommand request, CancellationToken cancellationToken)
         {
+            var audios = ResolveAudios(request);
+            if (audios.Count == 0)
+                return Error.Validation(description: "At least one audio file is required.");
+
+            var hasPicture = request.PictureFileType != null && request.PictureContentType != null;
             var routes = trackConfiguration.Routes;
-            var issued = await issuer.IssueAsync(
+
-                request.UserId,
+            var uploads = new List<UploadRequest>();
-                [
+            if (hasPicture)
-                    new UploadRequest(UploadIntentPurpose.TrackPicture, routes, request.PictureFileType, request.PictureContentType, request.ExpectedPictureSizeBytes),
+            {
-                    new UploadRequest(UploadIntentPurpose.TrackAudio, routes, request.AudioFileType, request.AudioContentType, request.ExpectedAudioSizeBytes)
+                for (var index = 0; index < audios.Count; index++)
-                ],
+                {
-                cancellationToken);
+                    uploads.Add(new UploadRequest(
+                        UploadIntentPurpose.TrackPicture, routes, request.PictureFileType!, request.PictureContentType!,
+                        request.ExpectedPictureSizeBytes, PictureKeyGroup));
+                }
+            }
+
+            uploads.AddRange(audios.Select(audio =>
+                new UploadRequest(UploadIntentPurpose.TrackAudio, routes, audio.FileType, audio.ContentType, audio.ExpectedSizeBytes)));
+
+            var issued = await issuer.IssueAsync(request.UserId, uploads, cancellationToken);
             if (issued.IsError)
                 return issued.Errors;
 
-            var picture = issued.Value[0];
+            var pictures = hasPicture ? issued.Value.Take(audios.Count).ToList() : [];
-            var audio = issued.Value[1];
+            var audioUploads = issued.Value.Skip(pictures.Count).ToList();
 
-            return new TrackUploadUrlsResponse(
+            var items = audioUploads
-                picture.IntentId,
+                .Select((audio, index) => new TrackAudioUpload(
                     audio.IntentId,
-                storageConfiguration.Bucket,
+                    hasPicture ? pictures[index].IntentId : null,
-                picture.Key,
-                picture.ObjectName,
-                picture.ContentType,
-                picture.UploadUrl,
                     audio.Key,
                     audio.ObjectName,
                     audio.ContentType,
-                audio.UploadUrl,
+                    audio.UploadUrl))
-                uploadIntentConfiguration.UploadUrlExpiresInSeconds);
+                .ToList();
+
+            var firstPicture = pictures.Count > 0 ? pictures[0] : null;
+            var firstAudio = audioUploads[0];
+
+            return new TrackUploadUrlsResponse(
+                firstPicture?.IntentId,
+                firstAudio.IntentId,
+                storageConfiguration.Bucket,
+                firstPicture?.Key,
+                firstPicture?.ObjectName,
+                firstPicture?.ContentType,
+                firstPicture?.UploadUrl,
+                firstAudio.Key,
+                firstAudio.ObjectName,
+                firstAudio.ContentType,
+                firstAudio.UploadUrl,
+                uploadIntentConfiguration.UploadUrlExpiresInSeconds,
+                items);
+        }
+
+        private static IReadOnlyList<AudioUploadSpec> ResolveAudios(RequestTrackUploadUrlsCommand request)
+        {
+            if (request.Audios is { Count: > 0 } audios)
+                return audios;
+
+            return request.AudioFileType != null && request.AudioContentType != null
+                ? [new AudioUploadSpec(request.AudioFileType, request.AudioContentType, request.ExpectedAudioSizeBytes)]
+                : [];
         }
     }
 }

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

@@ -0,0 +1,6 @@
+namespace Musify.Application.Tracks.Responses
+{
+    public record DeleteTracksResponse(
+        IReadOnlyList<Guid> DeletedTrackIds,
+        IReadOnlyList<Guid> FailedTrackIds);
+}

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

@@ -0,0 +1,6 @@
+namespace Musify.Application.Tracks.Responses
+{
+    public record SetTracksPublishedResponse(
+        IReadOnlyList<Guid> UpdatedTrackIds,
+        IReadOnlyList<Guid> SkippedTrackIds);
+}

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

@@ -14,7 +14,9 @@ namespace Musify.Application.Tracks.Responses
         DateTime UpdatedAt,
         long OwnerUserId,
         IReadOnlyCollection<Genre> Tags,
-        bool IsExplicit)
+        bool IsExplicit,
+        bool IsPublished,
+        IReadOnlyList<TrackCoauthorReference> Coauthors)
     {
         public static TrackApplicationResponse FromEntity(Track track, int listensCount) =>
             new(
@@ -28,6 +30,8 @@ namespace Musify.Application.Tracks.Responses
                 track.UpdatedAt,
                 track.OwnerUserId,
                 track.Tags.Select(tag => tag.Tag).ToList(),
-                track.IsExplicit);
+                track.IsExplicit,
+                track.IsPublished,
+                []);
     }
 }

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

@@ -0,0 +1,8 @@
+using Musify.Domain.ValueObjects;
+
+namespace Musify.Application.Tracks.Responses
+{
+    public record TrackCoauthorReference(long Id, string Name);
+
+    public record TrackCoauthorInviteReference(long UserId, string Name, CoauthorStatus Status);
+}

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

@@ -8,6 +8,12 @@ namespace Musify.Application.Tracks.Responses
         public static IQueryable<Track> Active(this IQueryable<Track> query) =>
             query.Where(track => track.LifeCycleStatus == LifeCycleStatus.Active);
 
+        public static IQueryable<Track> WherePublished(this IQueryable<Track> query) =>
+            query.Where(track => track.IsPublished);
+
+        public static IQueryable<Track> VisibleTo(this IQueryable<Track> query, long? viewerId) =>
+            query.Where(track => track.IsPublished || track.OwnerUserId == viewerId);
+
         public static IQueryable<TrackApplicationResponse> SelectResponse(this IQueryable<Track> query) =>
             query.Select(track => new TrackApplicationResponse(
                 track.Id,
@@ -20,6 +26,47 @@ namespace Musify.Application.Tracks.Responses
                 track.UpdatedAt,
                 track.OwnerUserId,
                 track.Tags.Select(tag => tag.Tag).ToList(),
-                track.IsExplicit));
+                track.IsExplicit,
+                track.IsPublished,
+                track.Coauthors
+                    .Where(coauthor => coauthor.Status == CoauthorStatus.Accepted)
+                    .OrderBy(coauthor => coauthor.RespondedAt)
+                    .ThenBy(coauthor => coauthor.UserId)
+                    .Select(coauthor => new TrackCoauthorReference(coauthor.UserId, coauthor.User.Name))
+                    .ToList()));
+
+        public static IQueryable<UserTrackApplicationResponse> SelectUserResponse(this IQueryable<Track> query, bool includeInvites = false) =>
+            query.Select(track => new UserTrackApplicationResponse(
+                track.Id,
+                track.Title,
+                track.Owner.Name,
+                track.Audio.TranscodeStatus,
+                track.DurationSeconds,
+                track.ListeningHistories.Count(listen => listen.IsCounted),
+                track.CreatedAt,
+                track.UpdatedAt,
+                track.OwnerUserId,
+                track.Tags.Select(tag => tag.Tag).ToList(),
+                track.IsExplicit,
+                track.IsPublished,
+                track.AlbumTracks
+                    .Where(albumTrack => albumTrack.Album.LifeCycleStatus == LifeCycleStatus.Active)
+                    .OrderBy(albumTrack => albumTrack.AddedAt)
+                    .ThenBy(albumTrack => albumTrack.AlbumId)
+                    .Select(albumTrack => new TrackAlbumReference(albumTrack.AlbumId, albumTrack.Album.Title))
+                    .ToList(),
+                track.Coauthors
+                    .Where(coauthor => coauthor.Status == CoauthorStatus.Accepted)
+                    .OrderBy(coauthor => coauthor.RespondedAt)
+                    .ThenBy(coauthor => coauthor.UserId)
+                    .Select(coauthor => new TrackCoauthorReference(coauthor.UserId, coauthor.User.Name))
+                    .ToList(),
+                includeInvites
+                    ? track.Coauthors
+                        .OrderBy(coauthor => coauthor.InvitedAt)
+                        .ThenBy(coauthor => coauthor.UserId)
+                        .Select(coauthor => new TrackCoauthorInviteReference(coauthor.UserId, coauthor.User.Name, coauthor.Status))
+                        .ToList()
+                    : new List<TrackCoauthorInviteReference>()));
     }
 }

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

@@ -0,0 +1,11 @@
+namespace Musify.Application.Tracks.Responses
+{
+    public record TrackStatusCountsResponse(
+        int Total,
+        int Pending,
+        int Processing,
+        int Completed,
+        int Failed,
+        int Published,
+        int Unpublished);
+}

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

@@ -1,16 +1,25 @@
 namespace Musify.Application.Tracks.Responses
 {
+    public record TrackAudioUpload(
+        Guid IntentId,
+        Guid? PictureIntentId,
+        string Key,
+        string Name,
+        string ContentType,
+        string UploadUrl);
+
     public record TrackUploadUrlsResponse(
-        Guid PictureIntentId,
+        Guid? PictureIntentId,
         Guid AudioIntentId,
         string Bucket,
-        string PictureKey,
+        string? PictureKey,
-        string PictureName,
+        string? PictureName,
-        string PictureContentType,
+        string? PictureContentType,
-        string PictureUploadUrl,
+        string? PictureUploadUrl,
         string AudioKey,
         string AudioName,
         string AudioContentType,
         string AudioUploadUrl,
-        int ExpiresInSeconds);
+        int ExpiresInSeconds,
+        IReadOnlyList<TrackAudioUpload> Audios);
 }

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

@@ -0,0 +1,23 @@
+using Musify.Domain.ValueObjects;
+
+namespace Musify.Application.Tracks.Responses
+{
+    public record TrackAlbumReference(Guid Id, string Title);
+
+    public record UserTrackApplicationResponse(
+        Guid Id,
+        string Title,
+        string? Artist,
+        ProcessingStatus AudioStatus,
+        double Duration,
+        int ListensCount,
+        DateTime CreatedAt,
+        DateTime UpdatedAt,
+        long OwnerUserId,
+        IReadOnlyCollection<Genre> Tags,
+        bool IsExplicit,
+        bool IsPublished,
+        IReadOnlyList<TrackAlbumReference> Albums,
+        IReadOnlyList<TrackCoauthorReference> Coauthors,
+        IReadOnlyList<TrackCoauthorInviteReference> CoauthorInvites);
+}

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

@@ -0,0 +1,38 @@
+using ErrorOr;
+using Mediator;
+using Microsoft.Extensions.Logging;
+using Musify.Application.Contracts;
+using Musify.Application.Shared;
+
+namespace Musify.Application.Tracks
+{
+    public record SetTrackPublishedCommand(long UserId, Guid TrackId, bool IsPublished)
+        : ICommand<ErrorOr<Success>>;
+
+    public class SetTrackPublishedCommandHandler(
+        IDatabase database,
+        ILogger<SetTrackPublishedCommandHandler> logger)
+        : ICommandHandler<SetTrackPublishedCommand, ErrorOr<Success>>
+    {
+        public async ValueTask<ErrorOr<Success>> Handle(SetTrackPublishedCommand request, CancellationToken cancellationToken)
+        {
+            var found = await database.Tracks.FindOwnedAsync(request.TrackId, request.UserId, cancellationToken);
+            if (found.IsError)
+                return found.Errors;
+
+            var track = found.Value;
+            if (request.IsPublished && !track.Audio.IsProcessed)
+                return Error.Validation("Track.NotProcessed", "Only tracks whose audio finished processing can be published.");
+
+            if (track.IsPublished == request.IsPublished)
+                return Result.Success;
+
+            track.IsPublished = request.IsPublished;
+            await database.SaveChangesAsync(cancellationToken);
+
+            logger.LogInformation("{Action} track {TrackId}", request.IsPublished ? "Published" : "Unpublished", track.Id);
+
+            return Result.Success;
+        }
+    }
+}

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

@@ -0,0 +1,58 @@
+using ErrorOr;
+using Mediator;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging;
+using Musify.Application.Contracts;
+using Musify.Application.Shared;
+using Musify.Application.Tracks.Responses;
+using Musify.Domain.ValueObjects;
+
+namespace Musify.Application.Tracks
+{
+    public record SetTracksPublishedCommand(long UserId, IReadOnlyList<Guid> TrackIds, bool IsPublished)
+        : ICommand<ErrorOr<SetTracksPublishedResponse>>;
+
+    public class SetTracksPublishedCommandHandler(
+        IDatabase database,
+        ILogger<SetTracksPublishedCommandHandler> logger)
+        : ICommandHandler<SetTracksPublishedCommand, ErrorOr<SetTracksPublishedResponse>>
+    {
+        public async ValueTask<ErrorOr<SetTracksPublishedResponse>> Handle(SetTracksPublishedCommand request, CancellationToken cancellationToken)
+        {
+            var requestedIds = request.TrackIds.Distinct().ToList();
+
+            var tracks = await database.Tracks
+                .Where(track => requestedIds.Contains(track.Id) && track.LifeCycleStatus == LifeCycleStatus.Active)
+                .ToListAsync(cancellationToken);
+
+            var foreign = tracks.FirstOrDefault(track => track.OwnerUserId != request.UserId);
+            if (foreign != null)
+                return AppErrors.Forbidden("Track", foreign.Id);
+
+            var updated = new List<Guid>();
+            var skipped = new List<Guid>();
+
+            foreach (var trackId in requestedIds)
+            {
+                var track = tracks.SingleOrDefault(candidate => candidate.Id == trackId);
+                if (track == null || (request.IsPublished && !track.Audio.IsProcessed))
+                {
+                    skipped.Add(trackId);
+                    continue;
+                }
+
+                track.IsPublished = request.IsPublished;
+                updated.Add(trackId);
+            }
+
+            if (updated.Count > 0)
+            {
+                await database.SaveChangesAsync(cancellationToken);
+                logger.LogInformation("{Action} {Count} tracks of user {UserId}",
+                    request.IsPublished ? "Published" : "Unpublished", updated.Count, request.UserId);
+            }
+
+            return new SetTracksPublishedResponse(updated, skipped);
+        }
+    }
+}

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

@@ -13,7 +13,6 @@ using Musify.Domain.ValueObjects;
 
 namespace Musify.Application.Tracks
 {
-    /// <summary>Starts a listen: records it for signed-in users and issues the stream ticket.</summary>
     public record StartListeningCommand(Guid TrackId, long? UserId)
         : ICommand<ErrorOr<TrackStreamResponse>>;
 
@@ -31,6 +30,7 @@ namespace Musify.Application.Tracks
 
             var track = await database.Tracks.AsNoTracking()
                 .Where(t => t.Id == request.TrackId && t.LifeCycleStatus == LifeCycleStatus.Active)
+                .VisibleTo(request.UserId)
                 .Select(t => new { t.Id, t.Audio })
                 .SingleOrDefaultAsync(cancellationToken);
 

backend/Core/Musify.Application/UploadIntents/DeleteStaleTempUploads.cs

@@ -5,7 +5,6 @@ using Musify.Application.Contracts;
 
 namespace Musify.Application.UploadIntents
 {
-    /// <summary>Deletes temporary upload objects that nobody claimed within the retention window.</summary>
     public record DeleteStaleTempUploadsCommand : ICommand<int>;
 
     public class DeleteStaleTempUploadsCommandHandler(

backend/Core/Musify.Application/UploadIntents/ExpireUploadIntents.cs

@@ -7,7 +7,6 @@ using Musify.Domain.ValueObjects;
 
 namespace Musify.Application.UploadIntents
 {
-    /// <summary>Marks overdue upload intents as expired and deletes the ones expired for longer than the retention window.</summary>
     public record ExpireUploadIntentsCommand : ICommand<int>;
 
     public class ExpireUploadIntentsCommandHandler(

backend/Core/Musify.Application/Users/FollowUser.cs

@@ -38,7 +38,6 @@ namespace Musify.Application.Users
                 FollowedId = request.FollowedId
             }, cancellationToken);
 
-            // A concurrent double click can hit the unique index; already following is a successful no-op.
             var saved = await database.TrySaveChangesAsync(
                 AppErrors.Conflict("UserFollow.Duplicate", "Already following this user."), cancellationToken);
             if (saved.IsError)

backend/Core/Musify.Domain/Entities/Album.cs

@@ -22,6 +22,8 @@ namespace Musify.Domain.Entities
 
         public int? ReleaseYear { get; set; }
 
+        public AlbumType Type { get; set; }
+
         public EntityPictures? Pictures { get; set; }
 
         public required long OwnerUserId { get; set; }

backend/Core/Musify.Domain/Entities/Track.cs

@@ -28,6 +28,8 @@ namespace Musify.Domain.Entities
 
         public bool IsExplicit { get; set; }
 
+        public bool IsPublished { get; set; }
+
         public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
 
         public DateTime UpdatedAt { get; set; } = DateTime.UtcNow;
@@ -43,5 +45,7 @@ namespace Musify.Domain.Entities
         public ICollection<ListeningHistory> ListeningHistories { get; set; } = new List<ListeningHistory>();
 
         public ICollection<TrackTag> Tags { get; set; } = new List<TrackTag>();
+
+        public ICollection<TrackCoauthor> Coauthors { get; set; } = new List<TrackCoauthor>();
     }
 }

backend/Core/Musify.Domain/Entities/TrackCoauthor.cs

@@ -0,0 +1,29 @@
+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+using Musify.Domain.ValueObjects;
+
+namespace Musify.Domain.Entities
+{
+    [Table("TrackCoauthors")]
+    public class TrackCoauthor
+    {
+        [Key]
+        public Guid Id { get; set; } = Guid.NewGuid();
+
+        public required Guid TrackId { get; set; }
+
+        public required long UserId { get; set; }
+
+        public CoauthorStatus Status { get; set; } = CoauthorStatus.Pending;
+
+        public DateTime InvitedAt { get; set; } = DateTime.UtcNow;
+
+        public DateTime? RespondedAt { get; set; }
+
+        [ForeignKey(nameof(TrackId))]
+        public Track Track { get; set; } = null!;
+
+        [ForeignKey(nameof(UserId))]
+        public User User { get; set; } = null!;
+    }
+}

backend/Core/Musify.Domain/ValueObjects/AlbumType.cs

@@ -0,0 +1,12 @@
+using System.Diagnostics.CodeAnalysis;
+
+namespace Musify.Domain.ValueObjects
+{
+    public enum AlbumType
+    {
+        Album = 0,
+        EP = 1,
+        [SuppressMessage("Naming", "CA1720:Identifier contains type name", Justification = "Part of the public API contract.")]
+        Single = 2
+    }
+}

backend/Core/Musify.Domain/ValueObjects/CoauthorStatus.cs

@@ -0,0 +1,9 @@
+namespace Musify.Domain.ValueObjects
+{
+    public enum CoauthorStatus
+    {
+        Pending = 0,
+        Accepted = 1,
+        Rejected = 2
+    }
+}

backend/Core/Musify.Domain/ValueObjects/EntityPictures.cs

@@ -2,7 +2,6 @@ using System.ComponentModel.DataAnnotations;
 
 namespace Musify.Domain.ValueObjects
 {
-    /// <summary>The picture file names of an album or playlist. Resized names stay null until processing finishes.</summary>
     public class EntityPictures
     {
         [Required]

backend/Core/Musify.Domain/ValueObjects/Genre.cs

@@ -2,31 +2,32 @@ namespace Musify.Domain.ValueObjects
 {
     public enum Genre
     {
-        Pop = 0,
+        None = 0,
-        Rock = 1,
+        Pop = 1,
-        HipHop = 2,
+        Rock = 2,
-        RnB = 3,
+        HipHop = 3,
-        Jazz = 4,
+        RnB = 4,
-        Blues = 5,
+        Jazz = 5,
-        Classical = 6,
+        Blues = 6,
-        Electronic = 7,
+        Classical = 7,
-        House = 8,
+        Electronic = 8,
-        Techno = 9,
+        House = 9,
-        Trance = 10,
+        Techno = 10,
-        Dubstep = 11,
+        Trance = 11,
-        DrumAndBass = 12,
+        Dubstep = 12,
-        Metal = 13,
+        DrumAndBass = 13,
-        Punk = 14,
+        Metal = 14,
-        Reggae = 15,
+        Punk = 15,
-        Reggaeton = 16,
+        Reggae = 16,
-        Country = 17,
+        Reggaeton = 17,
-        Folk = 18,
+        Country = 18,
-        Indie = 19,
+        Folk = 19,
-        KPop = 20,
+        Indie = 20,
-        Latin = 21,
+        KPop = 21,
-        Soul = 22,
+        Latin = 22,
-        Funk = 23,
+        Soul = 23,
-        Ambient = 24,
+        Funk = 24,
-        Lofi = 25
+        Ambient = 25,
+        Lofi = 26
     }
 }

backend/Core/Musify.Infrastructure/Jobs/RecurringJobsRegistrar.cs

@@ -4,7 +4,6 @@ using Musify.Application.Configuration;
 
 namespace Musify.Infrastructure.Jobs
 {
-    /// <summary>Registers every recurring Hangfire job when the host starts.</summary>
     public sealed class RecurringJobsRegistrar(
         IRecurringJobManager recurringJobManager,
         UploadIntentConfiguration uploadIntentConfiguration)
@@ -30,7 +29,6 @@ namespace Musify.Infrastructure.Jobs
 
         public Task StopAsync(CancellationToken cancellationToken) => Task.CompletedTask;
 
-        /// <summary>Hangfire cron has a one-minute resolution, so the interval is rounded up to whole minutes.</summary>
         internal static string EveryCron(int intervalSeconds)
         {
             var minutes = Math.Max(1, (int)Math.Ceiling(intervalSeconds / 60.0));

backend/Core/Musify.Infrastructure/MassTransit/Activities/Audio/TrackAudioStatus.cs

@@ -5,7 +5,6 @@ using Musify.Domain.ValueObjects;
 
 namespace Musify.Infrastructure.MassTransit.Activities.Audio
 {
-    /// <summary>Shared bookkeeping of the audio processing activities.</summary>
     internal static class TrackAudioStatus
     {
         public static async Task<Track> LoadAsync(IDatabase database, Guid trackId, CancellationToken cancellationToken) =>

backend/Core/Musify.Infrastructure/MassTransit/Activities/LifeCycle/LifeCycleActivities.cs

@@ -8,7 +8,6 @@ using Musify.Infrastructure.MassTransit.Arguments;
 
 namespace Musify.Infrastructure.MassTransit.Activities.LifeCycle
 {
-    /// <summary>Sets the life-cycle status of an entity (removing, failed, ...). A missing entity is skipped.</summary>
     internal abstract class MarkLifeCycleActivity<TEntity>(IDatabase database, ILogger logger)
         : IExecuteActivity<MarkLifeCycleArguments>
         where TEntity : class, IHasLifeCycle
@@ -33,7 +32,6 @@ namespace Musify.Infrastructure.MassTransit.Activities.LifeCycle
         }
     }
 
-    /// <summary>Deletes an entity row. A missing entity is skipped.</summary>
     internal abstract class DeleteEntityActivity<TEntity>(IDatabase database, ILogger logger)
         : IExecuteActivity<DeleteEntityArguments>
         where TEntity : class, IHasLifeCycle
@@ -58,8 +56,6 @@ namespace Musify.Infrastructure.MassTransit.Activities.LifeCycle
         }
     }
 
-    // One concrete activity per entity keeps a separate queue for each of them:
-    // the endpoint name is the kebab-cased class name.
     internal sealed class MarkTrackLifeCycleActivity(IDatabase database, ILogger<MarkTrackLifeCycleActivity> logger)
         : MarkLifeCycleActivity<Track>(database, logger)
     {

backend/Core/Musify.Infrastructure/MassTransit/Activities/Pictures/UpdatePicturesActivity.cs

@@ -12,7 +12,6 @@ namespace Musify.Infrastructure.MassTransit.Activities.Pictures
 {
     internal sealed record PictureNames(string? Original, string? Small, string? Medium, string? Large);
 
-    /// <summary>Stores the processed picture names on the owner and reports it; compensation restores the previous names.</summary>
     internal abstract class UpdatePicturesActivity<TEntity>(
         IDatabase database,
         IPublishEndpoint publishEndpoint,
@@ -24,7 +23,6 @@ namespace Musify.Infrastructure.MassTransit.Activities.Pictures
 
         protected abstract Task<TEntity?> FindAsync(Guid id, CancellationToken cancellationToken);
 
-        /// <summary>Reads the current names; throws when the entity has no pending picture.</summary>
         protected abstract PictureNames Read(TEntity entity);
 
         protected abstract void Write(TEntity entity, PictureNames names, bool succeeded);

backend/Core/Musify.Infrastructure/MassTransit/Activities/Tracks/PublishTrackProcessingEventsActivity.cs

@@ -16,6 +16,8 @@ namespace Musify.Infrastructure.MassTransit.Activities.Tracks
         {
             var arguments = executeContext.Arguments;
 
+            if (arguments.FinalPictureKey != null)
+            {
                 await publishEndpoint.Publish(
                     new UpdateTrackPictureEvent(
                         arguments.TrackId,
@@ -23,6 +25,7 @@ namespace Musify.Infrastructure.MassTransit.Activities.Tracks
                         arguments.FinalPictureKey,
                         arguments.Sizes),
                     executeContext.CancellationToken);
+            }
 
             await publishEndpoint.Publish(
                 new UpdateTrackAudioEvent(

backend/Core/Musify.Infrastructure/MassTransit/Arguments/PublishTrackProcessingEventsArguments.cs

@@ -5,7 +5,7 @@ namespace Musify.Infrastructure.MassTransit.Arguments
     public record PublishTrackProcessingEventsArguments(
         Guid TrackId,
         string Bucket,
-        string FinalPictureKey,
+        string? FinalPictureKey,
         string FinalAudioKey,
         string AudioDestinationFolderKey,
         ImageSizes Sizes);

backend/Core/Musify.Infrastructure/MassTransit/Consumers/ProcessingFailedCleanup.cs

@@ -7,7 +7,6 @@ namespace Musify.Infrastructure.MassTransit.Consumers
 {
     internal static class ProcessingFailedCleanup
     {
-        /// <summary>Removes whatever files were left behind and marks the entity as failed.</summary>
         public static Task ExecuteAsync(
             IBus bus,
             Guid subjectId,

backend/Core/Musify.Infrastructure/MassTransit/RoutingSlip/Builders/CreateTrackRoutingSlipBuilder.cs

@@ -11,11 +11,21 @@ namespace Musify.Infrastructure.MassTransit.RoutingSlip.Builders
     {
         public RoutingSlipBuilder Build(CreateTrackResourcesEvent message, Guid? correlationId)
         {
-            var builder = RoutingSlips.Create(correlationId)
+            var builder = RoutingSlips.Create(correlationId);
-                .AddStep(
+
+            var hasPicture = message.PictureIntentId != null
+                && message.PictureSourceKey != null
+                && message.PictureDestinationKey != null;
+
+            if (hasPicture)
+            {
+                builder.AddStep(
                     ActivityNames.CopyPictureToFinal,
                     CopyFileInBucketActivity.ExecuteEndpointName,
-                    new CopyFileInBucketArguments(message.Bucket, message.PictureSourceKey, message.Bucket, message.PictureDestinationKey))
+                    new CopyFileInBucketArguments(message.Bucket, message.PictureSourceKey!, message.Bucket, message.PictureDestinationKey!));
+            }
+
+            builder
                 .AddStep(
                     ActivityNames.CopyAudioToFinal,
                     CopyFileInBucketActivity.ExecuteEndpointName,
@@ -23,21 +33,23 @@ namespace Musify.Infrastructure.MassTransit.RoutingSlip.Builders
                 .AddStep(
                     ActivityNames.ConsumeUploadIntents,
                     ConsumeUploadIntentsActivity.ExecuteEndpointName,
-                    new ConsumeUploadIntentsArguments([message.PictureIntentId, message.AudioIntentId]))
+                    new ConsumeUploadIntentsArguments(
+                        hasPicture ? [message.PictureIntentId!.Value, message.AudioIntentId] : [message.AudioIntentId]))
                 .AddStep(
                     ActivityNames.PublishTrackProcessingEvents,
                     PublishTrackProcessingEventsActivity.ExecuteEndpointName,
                     new PublishTrackProcessingEventsArguments(
                         message.TrackId,
                         message.Bucket,
-                        message.PictureDestinationKey,
+                        hasPicture ? message.PictureDestinationKey : null,
                         message.AudioDestinationKey,
                         message.AudioProcessedFolderKey,
                         message.Sizes))
                 .TrackFaults(message.TrackId, RoutingSlipVariableNames.ProcessKinds.TrackCreation);
 
             builder.AddVariable(RoutingSlipVariableNames.Workflow.Bucket, message.Bucket);
-            builder.AddVariable(RoutingSlipVariableNames.Workflow.PictureKey, message.PictureDestinationKey);
+            if (hasPicture)
+                builder.AddVariable(RoutingSlipVariableNames.Workflow.PictureKey, message.PictureDestinationKey!);
             builder.AddVariable(RoutingSlipVariableNames.Workflow.AudioKey, message.AudioDestinationKey);
 
             return builder;

backend/Core/Musify.Infrastructure/MassTransit/RoutingSlip/Builders/DeleteRoutingSlipBuilder.cs

@@ -8,7 +8,6 @@ using Musify.Infrastructure.MassTransit.Arguments;
 
 namespace Musify.Infrastructure.MassTransit.RoutingSlip.Builders
 {
-    /// <summary>Marks an entity as removing, deletes its files from the bucket and finally deletes its row.</summary>
     public class DeleteRoutingSlipBuilder(
         IDatabase database,
         TrackConfiguration trackConfiguration,
@@ -48,8 +47,7 @@ namespace Musify.Infrastructure.MassTransit.RoutingSlip.Builders
                         routes.BuildOriginalPicturePath(userId, track.Pictures.OriginalName));
                 }
 
-                // Unprocessed tracks still point at the shared preset pictures, which must never be deleted.
+                if (track.Pictures.IsProcessed && !string.IsNullOrEmpty(track.Pictures.OriginalName))
-                if (track.Pictures.IsProcessed)
                 {
                     builder.AddRemoveFile(ActivityNames.RemoveTrackSmallPicture, bucket, routes.BuildPicturePath(PictureSize.Small, track.Pictures.SmallName));
                     builder.AddRemoveFile(ActivityNames.RemoveTrackMediumPicture, bucket, routes.BuildPicturePath(PictureSize.Medium, track.Pictures.MediumName));

backend/Core/Musify.Infrastructure/MassTransit/RoutingSlip/Builders/PictureSourceRoutingSlipBuilder.cs

@@ -8,10 +8,6 @@ using Musify.Infrastructure.MassTransit.Arguments;
 
 namespace Musify.Infrastructure.MassTransit.RoutingSlip.Builders
 {
-    /// <summary>
-    /// Moves an uploaded album/playlist picture to its final key, consumes the upload intent and hands over to the picture workflow.
-    /// Creation faults mark the whole entity as failed; update faults only report the picture as failed.
-    /// </summary>
     public class PictureSourceRoutingSlipBuilder
     {
         public RoutingSlipBuilder Build(CreateAlbumResourcesEvent message, Guid? correlationId) =>

backend/Core/Musify.Infrastructure/MassTransit/RoutingSlip/Builders/PictureWorkflowRoutingSlipBuilder.cs

@@ -8,7 +8,6 @@ using Musify.Infrastructure.MassTransit.Arguments;
 
 namespace Musify.Infrastructure.MassTransit.RoutingSlip.Builders
 {
-    /// <summary>Downloads a picture, resizes it to the three sizes, uploads them and records the result on the owner.</summary>
     public class PictureWorkflowRoutingSlipBuilder(WorkerConfiguration workerConfiguration)
     {
         public RoutingSlipBuilder Build(UpdateTrackPictureEvent message, Guid? correlationId) =>

backend/Core/Musify.Infrastructure/MassTransit/RoutingSlip/RoutingSlips.cs

@@ -6,14 +6,12 @@ using Musify.Infrastructure.MassTransit.Consumers;
 
 namespace Musify.Infrastructure.MassTransit.RoutingSlip
 {
-    /// <summary>Shared building blocks for every routing slip in the worker.</summary>
     internal static class RoutingSlips
     {
         public static Uri ExecuteUri(string endpointName) => new($"queue:{endpointName}_execute");
 
         public static Uri ConsumerUri(string queueName) => new($"queue:{queueName}");
 
-        /// <summary>A new slip that carries the correlation id and always cleans its temporary directory up.</summary>
         public static RoutingSlipBuilder Create(Guid? correlationId)
         {
             var builder = new RoutingSlipBuilder(NewId.NextGuid());
@@ -32,7 +30,6 @@ namespace Musify.Infrastructure.MassTransit.RoutingSlip
             return builder;
         }
 
-        /// <summary>Publishes a failure event for the subject when the slip faults.</summary>
         public static RoutingSlipBuilder TrackFaults(
             this RoutingSlipBuilder builder, Guid subjectId, string processKind)
         {

backend/Core/Musify.Infrastructure/MassTransit/Sagas/TrackProcessingStateMachine.cs

@@ -48,6 +48,7 @@ namespace Musify.Infrastructure.MassTransit.Sagas
                         context.Saga.UpdatedAt = DateTime.UtcNow;
                         context.Saga.Bucket = context.Message.Bucket;
                         context.Saga.PictureKey = context.Message.PictureDestinationKey;
+                        context.Saga.PictureProcessed = context.Message.PictureDestinationKey == null;
                         context.Saga.AudioKey = context.Message.AudioDestinationKey;
                     })
                     .TransitionTo(Processing));

backend/Core/Musify.Infrastructure/Persistence/Database.cs

@@ -59,6 +59,8 @@ namespace Musify.Infrastructure.Persistence
 
         public DbSet<UserFollow> UserFollows => Set<UserFollow>();
 
+        public DbSet<TrackCoauthor> TrackCoauthors => Set<TrackCoauthor>();
+
         public async Task<IDatabaseTransaction> BeginTransactionAsync(System.Data.IsolationLevel isolationLevel, CancellationToken cancellationToken)
         {
             var transaction = await Database.BeginTransactionAsync(isolationLevel, cancellationToken);

backend/Core/Musify.Infrastructure/Persistence/Migrations/20260924154218_GenreNone.cs

@@ -0,0 +1,26 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace Musify.Infrastructure.Persistence.Migrations
+{
+    /// <inheritdoc />
+    public partial class GenreNone : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AlterDatabase()
+                .Annotation("Npgsql:Enum:genre", "ambient,blues,classical,country,drum_and_bass,dubstep,electronic,folk,funk,hip_hop,house,indie,jazz,k_pop,latin,lofi,metal,none,pop,punk,reggae,reggaeton,rn_b,rock,soul,techno,trance")
+                .OldAnnotation("Npgsql:Enum:genre", "ambient,blues,classical,country,drum_and_bass,dubstep,electronic,folk,funk,hip_hop,house,indie,jazz,k_pop,latin,lofi,metal,pop,punk,reggae,reggaeton,rn_b,rock,soul,techno,trance");
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AlterDatabase()
+                .Annotation("Npgsql:Enum:genre", "ambient,blues,classical,country,drum_and_bass,dubstep,electronic,folk,funk,hip_hop,house,indie,jazz,k_pop,latin,lofi,metal,pop,punk,reggae,reggaeton,rn_b,rock,soul,techno,trance")
+                .OldAnnotation("Npgsql:Enum:genre", "ambient,blues,classical,country,drum_and_bass,dubstep,electronic,folk,funk,hip_hop,house,indie,jazz,k_pop,latin,lofi,metal,none,pop,punk,reggae,reggaeton,rn_b,rock,soul,techno,trance");
+        }
+    }
+}

backend/Core/Musify.Infrastructure/Persistence/Migrations/20260924231849_TrackPublicationAndAlbumType.cs

@@ -0,0 +1,42 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace Musify.Infrastructure.Persistence.Migrations
+{
+    /// <inheritdoc />
+    public partial class TrackPublicationAndAlbumType : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<bool>(
+                name: "IsPublished",
+                table: "Tracks",
+                type: "boolean",
+                nullable: false,
+                defaultValue: false);
+
+            migrationBuilder.Sql("UPDATE \"Tracks\" SET \"IsPublished\" = TRUE;");
+
+            migrationBuilder.AddColumn<int>(
+                name: "Type",
+                table: "Albums",
+                type: "integer",
+                nullable: false,
+                defaultValue: 0);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropColumn(
+                name: "IsPublished",
+                table: "Tracks");
+
+            migrationBuilder.DropColumn(
+                name: "Type",
+                table: "Albums");
+        }
+    }
+}

backend/Core/Musify.Infrastructure/Persistence/Migrations/20260925001154_AddTrackCoauthors.cs

@@ -0,0 +1,61 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace Musify.Infrastructure.Persistence.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddTrackCoauthors : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.CreateTable(
+                name: "TrackCoauthors",
+                columns: table => new
+                {
+                    Id = table.Column<Guid>(type: "uuid", nullable: false),
+                    TrackId = table.Column<Guid>(type: "uuid", nullable: false),
+                    UserId = table.Column<long>(type: "bigint", nullable: false),
+                    Status = table.Column<int>(type: "integer", nullable: false),
+                    InvitedAt = table.Column<DateTime>(type: "timestamp with time zone", nullable: false),
+                    RespondedAt = table.Column<DateTime>(type: "timestamp with time zone", nullable: true)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_TrackCoauthors", x => x.Id);
+                    table.ForeignKey(
+                        name: "FK_TrackCoauthors_Tracks_TrackId",
+                        column: x => x.TrackId,
+                        principalTable: "Tracks",
+                        principalColumn: "Id",
+                        onDelete: ReferentialAction.Cascade);
+                    table.ForeignKey(
+                        name: "FK_TrackCoauthors_User_UserId",
+                        column: x => x.UserId,
+                        principalTable: "User",
+                        principalColumn: "Id",
+                        onDelete: ReferentialAction.Cascade);
+                });
+
+            migrationBuilder.CreateIndex(
+                name: "IX_TrackCoauthors_TrackId_UserId",
+                table: "TrackCoauthors",
+                columns: new[] { "TrackId", "UserId" },
+                unique: true);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_TrackCoauthors_UserId_Status",
+                table: "TrackCoauthors",
+                columns: new[] { "UserId", "Status" });
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropTable(
+                name: "TrackCoauthors");
+        }
+    }
+}

backend/Core/Musify.Infrastructure/Persistence/Migrations/DatabaseModelSnapshot.cs

@@ -21,7 +21,7 @@ namespace Musify.Infrastructure.Persistence.Migrations
                 .HasAnnotation("ProductVersion", "10.0.12")
                 .HasAnnotation("Relational:MaxIdentifierLength", 63);
 
-            NpgsqlModelBuilderExtensions.HasPostgresEnum(modelBuilder, "genre", new[] { "ambient", "blues", "classical", "country", "drum_and_bass", "dubstep", "electronic", "folk", "funk", "hip_hop", "house", "indie", "jazz", "k_pop", "latin", "lofi", "metal", "pop", "punk", "reggae", "reggaeton", "rn_b", "rock", "soul", "techno", "trance" });
+            NpgsqlModelBuilderExtensions.HasPostgresEnum(modelBuilder, "genre", new[] { "ambient", "blues", "classical", "country", "drum_and_bass", "dubstep", "electronic", "folk", "funk", "hip_hop", "house", "indie", "jazz", "k_pop", "latin", "lofi", "metal", "none", "pop", "punk", "reggae", "reggaeton", "rn_b", "rock", "soul", "techno", "trance" });
             NpgsqlModelBuilderExtensions.UseIdentityByDefaultColumns(modelBuilder);
 
             modelBuilder.Entity("MassTransit.EntityFrameworkCoreIntegration.InboxState", b =>
@@ -224,6 +224,9 @@ namespace Musify.Infrastructure.Persistence.Migrations
                         .HasMaxLength(200)
                         .HasColumnType("character varying(200)");
 
+                    b.Property<int>("Type")
+                        .HasColumnType("integer");
+
                     b.Property<DateTime>("UpdatedAt")
                         .HasColumnType("timestamp with time zone");
 
@@ -435,6 +438,9 @@ namespace Musify.Infrastructure.Persistence.Migrations
                     b.Property<bool>("IsExplicit")
                         .HasColumnType("boolean");
 
+                    b.Property<bool>("IsPublished")
+                        .HasColumnType("boolean");
+
                     b.Property<int>("LifeCycleStatus")
                         .HasColumnType("integer");
 
@@ -461,6 +467,37 @@ namespace Musify.Infrastructure.Persistence.Migrations
                     b.ToTable("Tracks");
                 });
 
+            modelBuilder.Entity("Musify.Domain.Entities.TrackCoauthor", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<DateTime>("InvitedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<DateTime?>("RespondedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<int>("Status")
+                        .HasColumnType("integer");
+
+                    b.Property<Guid>("TrackId")
+                        .HasColumnType("uuid");
+
+                    b.Property<long>("UserId")
+                        .HasColumnType("bigint");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("TrackId", "UserId")
+                        .IsUnique();
+
+                    b.HasIndex("UserId", "Status");
+
+                    b.ToTable("TrackCoauthors");
+                });
+
             modelBuilder.Entity("Musify.Domain.Entities.TrackLike", b =>
                 {
                     b.Property<Guid>("Id")
@@ -983,6 +1020,25 @@ namespace Musify.Infrastructure.Persistence.Migrations
                         .IsRequired();
                 });
 
+            modelBuilder.Entity("Musify.Domain.Entities.TrackCoauthor", b =>
+                {
+                    b.HasOne("Musify.Domain.Entities.Track", "Track")
+                        .WithMany("Coauthors")
+                        .HasForeignKey("TrackId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("Musify.Domain.Entities.User", "User")
+                        .WithMany()
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Track");
+
+                    b.Navigation("User");
+                });
+
             modelBuilder.Entity("Musify.Domain.Entities.TrackLike", b =>
                 {
                     b.HasOne("Musify.Domain.Entities.Track", "Track")
@@ -1062,6 +1118,8 @@ namespace Musify.Infrastructure.Persistence.Migrations
                 {
                     b.Navigation("AlbumTracks");
 
+                    b.Navigation("Coauthors");
+
                     b.Navigation("ListeningHistories");
 
                     b.Navigation("PlayListTracks");

backend/Core/Musify.Infrastructure/Persistence/ModelConfiguration.cs

@@ -5,9 +5,6 @@ using Musify.Infrastructure.MassTransit.Sagas;
 
 namespace Musify.Infrastructure.Persistence
 {
-    /// <summary>
-    /// Entity model shared by <see cref="Database"/> and the in-memory test database, so both always agree.
-    /// </summary>
     public static class ModelConfiguration
     {
         public static void Apply(ModelBuilder modelBuilder)
@@ -125,6 +122,25 @@ namespace Musify.Infrastructure.Persistence
                 .HasIndex(trackTag => new { trackTag.TrackId, trackTag.Tag })
                 .IsUnique();
 
+            modelBuilder.Entity<TrackCoauthor>()
+                .HasOne(coauthor => coauthor.Track)
+                .WithMany(track => track.Coauthors)
+                .HasForeignKey(coauthor => coauthor.TrackId)
+                .OnDelete(DeleteBehavior.Cascade);
+
+            modelBuilder.Entity<TrackCoauthor>()
+                .HasOne(coauthor => coauthor.User)
+                .WithMany()
+                .HasForeignKey(coauthor => coauthor.UserId)
+                .OnDelete(DeleteBehavior.Cascade);
+
+            modelBuilder.Entity<TrackCoauthor>()
+                .HasIndex(coauthor => new { coauthor.TrackId, coauthor.UserId })
+                .IsUnique();
+
+            modelBuilder.Entity<TrackCoauthor>()
+                .HasIndex(coauthor => new { coauthor.UserId, coauthor.Status });
+
             modelBuilder.Entity<UserFollow>()
                 .HasOne(follow => follow.Follower)
                 .WithMany()

backend/Hosts/Musify.Api/DataTransferObjects/Albums/CreateAlbumRequest.cs

@@ -1,8 +1,12 @@
+using Musify.Domain.ValueObjects;
+
 namespace Musify.Api.DataTransferObjects.Albums
 {
     public record CreateAlbumRequest(
         string Title,
         string? Description,
         int? ReleaseYear,
-        Guid PictureIntentId);
+        Guid PictureIntentId,
+        AlbumType Type = AlbumType.Album,
+        IReadOnlyList<Guid>? TrackIds = null);
 }

backend/Hosts/Musify.Api/DataTransferObjects/Albums/UpdateAlbumPictureRequest.cs

@@ -0,0 +1,4 @@
+namespace Musify.Api.DataTransferObjects.Albums
+{
+    public record UpdateAlbumPictureRequest(Guid PictureIntentId);
+}

backend/Hosts/Musify.Api/DataTransferObjects/Albums/UpdateAlbumRequest.cs

@@ -1,8 +1,10 @@
+using Musify.Domain.ValueObjects;
+
 namespace Musify.Api.DataTransferObjects.Albums
 {
     public record UpdateAlbumRequest(
         string Title,
         string? Description,
         int? ReleaseYear,
-        Guid? PictureIntentId);
+        AlbumType? Type = null);
 }

backend/Hosts/Musify.Api/DataTransferObjects/PlayLists/UpdatePlayListPictureRequest.cs

@@ -0,0 +1,4 @@
+namespace Musify.Api.DataTransferObjects.PlayLists
+{
+    public record UpdatePlayListPictureRequest(Guid PictureIntentId);
+}

backend/Hosts/Musify.Api/DataTransferObjects/PlayLists/UpdatePlayListRequest.cs

@@ -3,8 +3,7 @@ using Musify.Domain.ValueObjects;
 namespace Musify.Api.DataTransferObjects.PlayLists
 {
     public record UpdatePlayListRequest(
-        string? Name,
+        string Name,
         string? Description,
-        Guid? PictureIntentId,
+        PlayListVisibility? Visibility);
-        PlayListVisibility? Visibility = null);
 }

backend/Hosts/Musify.Api/DataTransferObjects/Tracks/CreateTrackRequest.cs

@@ -4,7 +4,7 @@ namespace Musify.Api.DataTransferObjects.Tracks
 {
     public record CreateTrackRequest(
         string Title,
-        Guid PictureIntentId,
+        Guid? PictureIntentId,
         Guid AudioIntentId,
         IReadOnlyCollection<Genre> Tags,
         bool IsExplicit = false);