Complete LinkedChildren integration and batch DTO optimizations

This commit integrates remaining performance changes:

- Add batch user data fetching in DtoService to reduce N+1 queries
- Add GetNextUpEpisodesBatch in TVSeriesManager for efficient batch retrieval
- Update Video/Movie/BoxSet to use LibraryManager for alternate versions
- Transition LinkedChild to use ItemId instead of Path (obsolete Path/LibraryItemId)
- Update providers and controllers for LinkedChildren-based references
- Add NextUpEpisodeBatchResult for batched episode queries
- Integrate IDescendantQueryProvider in SqliteDatabaseProvider

6 files changed, 302 insertions, 143 deletions

diff --git a/Emby.Server.Implementations/Collections/CollectionManager.cs b/Emby.Server.Implementations/Collections/CollectionManager.cs
index a320a774c6..0ede5665f9 100644
--- a/Emby.Server.Implementations/Collections/CollectionManager.cs
+++ b/Emby.Server.Implementations/Collections/CollectionManager.cs
@@ -272,7 +272,7 @@ namespace Emby.Server.Implementations.Collections
             {
                 var childItem = _libraryManager.GetItemById(guidId);
 
-                var child = collection.LinkedChildren.FirstOrDefault(i => (i.ItemId.HasValue && i.ItemId.Value.Equals(guidId)) || (childItem is not null && string.Equals(childItem.Path, i.Path, StringComparison.OrdinalIgnoreCase)));
+                var child = collection.LinkedChildren.FirstOrDefault(i => i.ItemId.HasValue && i.ItemId.Value.Equals(guidId));
 
                 if (child is null)
                 {
@@ -342,7 +342,7 @@ namespace Emby.Server.Implementations.Collections
                     // this is kind of a performance hack because only Video has alternate versions that should be in a box set?
                     if (item is Video video)
                     {
-                        foreach (var childId in video.GetLocalAlternateVersionIds())
+                        foreach (var childId in _libraryManager.GetLocalAlternateVersionIds(video))
                         {
                             if (!results.ContainsKey(childId))
                             {
diff --git a/Emby.Server.Implementations/Dto/DtoService.cs b/Emby.Server.Implementations/Dto/DtoService.cs
index c5dc3b054c..236b3fabe4 100644
--- a/Emby.Server.Implementations/Dto/DtoService.cs
+++ b/Emby.Server.Implementations/Dto/DtoService.cs
@@ -153,17 +153,42 @@ namespace Emby.Server.Implementations.Dto
         private ILiveTvManager LivetvManager => _livetvManagerFactory.Value;
 
         /// <inheritdoc />
-        public IReadOnlyList<BaseItemDto> GetBaseItemDtos(IReadOnlyList<BaseItem> items, DtoOptions options, User? user = null, BaseItem? owner = null)
+        public IReadOnlyList<BaseItemDto> GetBaseItemDtos(IReadOnlyList<BaseItem> items, DtoOptions options, User? user = null, BaseItem? owner = null, bool skipVisibilityCheck = false)
         {
-            var accessibleItems = user is null ? items : items.Where(x => x.IsVisible(user)).ToList();
+            var accessibleItems = skipVisibilityCheck || user is null ? items : items.Where(x => x.IsVisible(user)).ToList();
             var returnItems = new BaseItemDto[accessibleItems.Count];
             List<(BaseItem, BaseItemDto)>? programTuples = null;
             List<(BaseItemDto, LiveTvChannel)>? channelTuples = null;
 
+            // Batch-fetch user data for all items
+            Dictionary<Guid, UserItemData>? userDataBatch = null;
+            if (user is not null && options.EnableUserData)
+            {
+                userDataBatch = _userDataRepository.GetUserDataBatch(accessibleItems, user);
+            }
+
+            // Pre-compute collection folders once to avoid N+1 queries in CanDelete
+            List<Folder>? allCollectionFolders = null;
+            if (user is not null && options.ContainsField(ItemFields.CanDelete))
+            {
+                allCollectionFolders = _libraryManager.GetUserRootFolder().Children.OfType<Folder>().ToList();
+            }
+
+            // Batch-fetch child counts for all folders to avoid N+1 queries
+            Dictionary<Guid, int>? childCountBatch = null;
+            if (options.ContainsField(ItemFields.ChildCount))
+            {
+                var folderIds = accessibleItems.OfType<Folder>().Select(f => f.Id).ToList();
+                if (folderIds.Count > 0)
+                {
+                    childCountBatch = _libraryManager.GetChildCountBatch(folderIds, user?.Id);
+                }
+            }
+
             for (int index = 0; index < accessibleItems.Count; index++)
             {
                 var item = accessibleItems[index];
-                var dto = GetBaseItemDtoInternal(item, options, user, owner);
+                var dto = GetBaseItemDtoInternal(item, options, user, owner, userDataBatch?.GetValueOrDefault(item.Id), allCollectionFolders, childCountBatch);
 
                 if (item is LiveTvChannel tvChannel)
                 {
@@ -197,7 +222,7 @@ namespace Emby.Server.Implementations.Dto
 
         public BaseItemDto GetBaseItemDto(BaseItem item, DtoOptions options, User? user = null, BaseItem? owner = null)
         {
-            var dto = GetBaseItemDtoInternal(item, options, user, owner);
+            var dto = GetBaseItemDtoInternal(item, options, user, owner, null);
             if (item is LiveTvChannel tvChannel)
             {
                 LivetvManager.AddChannelInfo(new[] { (dto, tvChannel) }, options, user);
@@ -215,7 +240,7 @@ namespace Emby.Server.Implementations.Dto
             return dto;
         }
 
-        private BaseItemDto GetBaseItemDtoInternal(BaseItem item, DtoOptions options, User? user = null, BaseItem? owner = null)
+        private BaseItemDto GetBaseItemDtoInternal(BaseItem item, DtoOptions options, User? user = null, BaseItem? owner = null, UserItemData? userData = null, List<Folder>? allCollectionFolders = null, Dictionary<Guid, int>? childCountBatch = null)
         {
             var dto = new BaseItemDto
             {
@@ -252,7 +277,7 @@ namespace Emby.Server.Implementations.Dto
 
             if (user is not null)
             {
-                AttachUserSpecificInfo(dto, item, user, options);
+                AttachUserSpecificInfo(dto, item, user, options, userData, childCountBatch);
             }
 
             if (item is IHasMediaSources
@@ -274,7 +299,9 @@ namespace Emby.Server.Implementations.Dto
             {
                 dto.CanDelete = user is null
                     ? item.CanDelete()
-                    : item.CanDelete(user);
+                    : allCollectionFolders is not null
+                        ? item.CanDelete(user, allCollectionFolders)
+                        : item.CanDelete(user);
             }
 
             if (options.ContainsField(ItemFields.CanDownload))
@@ -458,7 +485,7 @@ namespace Emby.Server.Implementations.Dto
         /// <summary>
         /// Attaches the user specific info.
         /// </summary>
-        private void AttachUserSpecificInfo(BaseItemDto dto, BaseItem item, User user, DtoOptions options)
+        private void AttachUserSpecificInfo(BaseItemDto dto, BaseItem item, User user, DtoOptions options, UserItemData? userData = null, Dictionary<Guid, int>? childCountBatch = null)
         {
             if (item.IsFolder)
             {
@@ -466,7 +493,17 @@ namespace Emby.Server.Implementations.Dto
 
                 if (options.EnableUserData)
                 {
-                    dto.UserData = _userDataRepository.GetUserDataDto(item, dto, user, options);
+                    if (userData is not null)
+                    {
+                        // Use pre-fetched user data
+                        dto.UserData = GetUserItemDataDto(userData, item.Id);
+                        item.FillUserDataDtoValues(dto.UserData, userData, dto, user, options);
+                    }
+                    else
+                    {
+                        // Fall back to individual fetch
+                        dto.UserData = _userDataRepository.GetUserDataDto(item, dto, user, options);
+                    }
                 }
 
                 if (!dto.ChildCount.HasValue && item.SourceType == SourceType.Library)
@@ -485,7 +522,7 @@ namespace Emby.Server.Implementations.Dto
 
                     if (options.ContainsField(ItemFields.ChildCount))
                     {
-                        dto.ChildCount ??= GetChildCount(folder, user);
+                        dto.ChildCount ??= GetChildCount(folder, user, childCountBatch);
                     }
                 }
 
@@ -503,7 +540,17 @@ namespace Emby.Server.Implementations.Dto
             {
                 if (options.EnableUserData)
                 {
-                    dto.UserData = _userDataRepository.GetUserDataDto(item, user);
+                    if (userData is not null)
+                    {
+                        // Use pre-fetched user data
+                        dto.UserData = GetUserItemDataDto(userData, item.Id);
+                        item.FillUserDataDtoValues(dto.UserData, userData, dto, user, options);
+                    }
+                    else
+                    {
+                        // Fall back to individual fetch
+                        dto.UserData = _userDataRepository.GetUserDataDto(item, user);
+                    }
                 }
             }
 
@@ -513,7 +560,25 @@ namespace Emby.Server.Implementations.Dto
             }
         }
 
-        private static int GetChildCount(Folder folder, User user)
+        private static UserItemDataDto GetUserItemDataDto(UserItemData data, Guid itemId)
+        {
+            ArgumentNullException.ThrowIfNull(data);
+
+            return new UserItemDataDto
+            {
+                IsFavorite = data.IsFavorite,
+                Likes = data.Likes,
+                PlaybackPositionTicks = data.PlaybackPositionTicks,
+                PlayCount = data.PlayCount,
+                Rating = data.Rating,
+                Played = data.Played,
+                LastPlayedDate = data.LastPlayedDate,
+                ItemId = itemId,
+                Key = data.Key
+            };
+        }
+
+        private static int GetChildCount(Folder folder, User user, Dictionary<Guid, int>? childCountBatch)
         {
             // Right now this is too slow to calculate for top level folders on a per-user basis
             // Just return something so that apps that are expecting a value won't think the folders are empty
@@ -522,6 +587,13 @@ namespace Emby.Server.Implementations.Dto
                 return Random.Shared.Next(1, 10);
             }
 
+            // Use pre-fetched batch data if available
+            if (childCountBatch is not null && childCountBatch.TryGetValue(folder.Id, out var count))
+            {
+                return count;
+            }
+
+            // Fall back to individual query for special cases (Series, Season, etc.)
             return folder.GetChildCount(user);
         }
 
diff --git a/Emby.Server.Implementations/Library/LibraryManager.cs b/Emby.Server.Implementations/Library/LibraryManager.cs
index f7f5c387e1..2acfd68c36 100644
--- a/Emby.Server.Implementations/Library/LibraryManager.cs
+++ b/Emby.Server.Implementations/Library/LibraryManager.cs
@@ -406,6 +406,37 @@ namespace Emby.Server.Implementations.Library
                     item.Id);
             }
 
+            // If deleting a primary version video, clear PrimaryVersionId from alternate versions
+            if (item is Video video && string.IsNullOrEmpty(video.PrimaryVersionId))
+            {
+                var alternateVersions = GetLocalAlternateVersionIds(video)
+                    .Concat(GetLinkedAlternateVersions(video).Select(v => v.Id))
+                    .Distinct()
+                    .Select(id => GetItemById(id))
+                    .OfType<Video>()
+                    .ToList();
+
+                if (alternateVersions.Count > 0)
+                {
+                    _logger.LogInformation(
+                        "Clearing PrimaryVersionId from {Count} alternate versions of {Name}",
+                        alternateVersions.Count,
+                        item.Name ?? "Unknown name");
+
+                    // Promote the first alternate version to be the new primary
+                    var newPrimary = alternateVersions[0];
+                    newPrimary.SetPrimaryVersionId(null);
+                    newPrimary.UpdateToRepositoryAsync(ItemUpdateType.MetadataEdit, CancellationToken.None).GetAwaiter().GetResult();
+
+                    // Update remaining alternates to point to new primary
+                    foreach (var alternate in alternateVersions.Skip(1))
+                    {
+                        alternate.SetPrimaryVersionId(newPrimary.Id.ToString("N", CultureInfo.InvariantCulture));
+                        alternate.UpdateToRepositoryAsync(ItemUpdateType.MetadataEdit, CancellationToken.None).GetAwaiter().GetResult();
+                    }
+                }
+            }
+
             var children = item.IsFolder
                 ? ((Folder)item).GetRecursiveChildren(false)
                 : [];
@@ -576,6 +607,9 @@ namespace Emby.Server.Implementations.Library
                 // Trickplay
                 list.Add(_pathManager.GetTrickplayDirectory(video));
 
+                // Chapter Images
+                list.Add(_pathManager.GetChapterImageFolderPath(video));
+
                 // Subtitles and attachments
                 foreach (var mediaSource in item.GetMediaSources(false))
                 {
@@ -1421,14 +1455,7 @@ namespace Emby.Server.Implementations.Library
                 AddUserToQuery(query, query.User, allowExternalContent);
             }
 
-            var itemList = _itemRepository.GetItemList(query);
-            var user = query.User;
-            if (user is not null)
-            {
-                return itemList.Where(i => i.IsVisible(user)).ToList();
-            }
-
-            return itemList;
+            return _itemRepository.GetItemList(query);
         }
 
         public IReadOnlyList<BaseItem> GetItemList(InternalItemsQuery query)
@@ -1474,6 +1501,11 @@ namespace Emby.Server.Implementations.Library
             return _itemRepository.GetItemCounts(query);
         }
 
+        public Dictionary<Guid, int> GetChildCountBatch(IReadOnlyList<Guid> parentIds, Guid? userId)
+        {
+            return _itemRepository.GetChildCountBatch(parentIds, userId);
+        }
+
         public IReadOnlyList<BaseItem> GetItemList(InternalItemsQuery query, List<BaseItem> parents)
         {
             SetTopParentIdsOrAncestors(query, parents);
@@ -1519,6 +1551,16 @@ namespace Emby.Server.Implementations.Library
             return _itemRepository.GetNextUpSeriesKeys(query, dateCutoff);
         }
 
+        /// <inheritdoc />
+        public IReadOnlyDictionary<string, MediaBrowser.Controller.Persistence.NextUpEpisodeBatchResult> GetNextUpEpisodesBatch(
+            InternalItemsQuery query,
+            IReadOnlyList<string> seriesKeys,
+            bool includeSpecials,
+            bool includeWatchedForRewatching)
+        {
+            return _itemRepository.GetNextUpEpisodesBatch(query, seriesKeys, includeSpecials, includeWatchedForRewatching);
+        }
+
         public QueryResult<BaseItem> QueryItems(InternalItemsQuery query)
         {
             if (query.User is not null)
@@ -1700,6 +1742,11 @@ namespace Emby.Server.Implementations.Library
 
         private void AddUserToQuery(InternalItemsQuery query, User user, bool allowExternalContent = true)
         {
+            if (query.User is null)
+            {
+                query.SetUser(user);
+            }
+
             if (query.AncestorIds.Length == 0 &&
                 query.ParentId.IsEmpty() &&
                 query.ChannelIds.Count == 0 &&
@@ -1725,6 +1772,15 @@ namespace Emby.Server.Implementations.Library
             }
         }
 
+        /// <inheritdoc/>
+        public void ConfigureUserAccess(InternalItemsQuery query, User user)
+        {
+            ArgumentNullException.ThrowIfNull(query);
+            ArgumentNullException.ThrowIfNull(user);
+
+            AddUserToQuery(query, user);
+        }
+
         private IEnumerable<Guid> GetTopParentIdsForQuery(BaseItem item, User? user)
         {
             if (item is UserView view)
@@ -1890,6 +1946,38 @@ namespace Emby.Server.Implementations.Library
         }
 
         /// <inheritdoc />
+        public IEnumerable<Guid> GetLocalAlternateVersionIds(Video video)
+        {
+            ArgumentNullException.ThrowIfNull(video);
+
+            var linkedIds = _itemRepository.GetLinkedChildrenIds(video.Id, (int)MediaBrowser.Controller.Entities.LinkedChildType.LocalAlternateVersion);
+            if (linkedIds.Count > 0)
+            {
+                return linkedIds;
+            }
+
+            return [];
+        }
+
+        /// <inheritdoc />
+        public IEnumerable<Video> GetLinkedAlternateVersions(Video video)
+        {
+            ArgumentNullException.ThrowIfNull(video);
+
+            var linkedIds = _itemRepository.GetLinkedChildrenIds(video.Id, (int)MediaBrowser.Controller.Entities.LinkedChildType.LinkedAlternateVersion);
+            if (linkedIds.Count > 0)
+            {
+                return linkedIds
+                    .Select(id => GetItemById(id))
+                    .Where(i => i is not null)
+                    .OfType<Video>()
+                    .OrderBy(i => i.SortName);
+            }
+
+            return [];
+        }
+
+        /// <inheritdoc />
         public IEnumerable<BaseItem> Sort(IEnumerable<BaseItem> items, User? user, IEnumerable<ItemSortBy> sortBy, SortOrder sortOrder)
         {
             IOrderedEnumerable<BaseItem>? orderedItems = null;
@@ -2896,10 +2984,17 @@ namespace Emby.Server.Implementations.Library
                     extra.ExtraType = extraType;
                 }
 
-                extra.ParentId = Guid.Empty;
-                extra.OwnerId = owner.Id;
-                extra.IsInMixedFolder = isInMixedFolder;
-                return extra;
+                // Only set OwnerId if this is actually an extra (not Unknown or null)
+                if (extra.ExtraType is not null)
+                {
+                    extra.ParentId = Guid.Empty;
+                    extra.OwnerId = owner.Id;
+                    extra.IsInMixedFolder = isInMixedFolder;
+
+                    return extra;
+                }
+
+                return null;
             }
         }
 
diff --git a/Emby.Server.Implementations/ScheduledTasks/Tasks/CleanupCollectionAndPlaylistPathsTask.cs b/Emby.Server.Implementations/ScheduledTasks/Tasks/CleanupCollectionAndPlaylistPathsTask.cs
index 7f68f7701e..1c2038d839 100644
--- a/Emby.Server.Implementations/ScheduledTasks/Tasks/CleanupCollectionAndPlaylistPathsTask.cs
+++ b/Emby.Server.Implementations/ScheduledTasks/Tasks/CleanupCollectionAndPlaylistPathsTask.cs
@@ -1,9 +1,9 @@
 using System;
 using System.Collections.Generic;
-using System.IO;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
+using Jellyfin.Extensions;
 using MediaBrowser.Controller.Collections;
 using MediaBrowser.Controller.Entities;
 using MediaBrowser.Controller.Entities.Movies;
@@ -11,7 +11,6 @@ using MediaBrowser.Controller.Library;
 using MediaBrowser.Controller.Playlists;
 using MediaBrowser.Controller.Providers;
 using MediaBrowser.Model.Globalization;
-using MediaBrowser.Model.IO;
 using MediaBrowser.Model.Tasks;
 using Microsoft.Extensions.Logging;
 
@@ -27,6 +26,7 @@ public class CleanupCollectionAndPlaylistPathsTask : IScheduledTask
     private readonly IPlaylistManager _playlistManager;
     private readonly ILogger<CleanupCollectionAndPlaylistPathsTask> _logger;
     private readonly IProviderManager _providerManager;
+    private readonly ILibraryManager _libraryManager;
 
     /// <summary>
     /// Initializes a new instance of the <see cref="CleanupCollectionAndPlaylistPathsTask"/> class.
@@ -36,18 +36,21 @@ public class CleanupCollectionAndPlaylistPathsTask : IScheduledTask
     /// <param name="playlistManager">Instance of the <see cref="IPlaylistManager"/> interface.</param>
     /// <param name="logger">Instance of the <see cref="ILogger"/> interface.</param>
     /// <param name="providerManager">Instance of the <see cref="IProviderManager"/> interface.</param>
+    /// <param name="libraryManager">Instance of the <see cref="ILibraryManager"/> interface.</param>
     public CleanupCollectionAndPlaylistPathsTask(
         ILocalizationManager localization,
         ICollectionManager collectionManager,
         IPlaylistManager playlistManager,
         ILogger<CleanupCollectionAndPlaylistPathsTask> logger,
-        IProviderManager providerManager)
+        IProviderManager providerManager,
+        ILibraryManager libraryManager)
     {
         _localization = localization;
         _collectionManager = collectionManager;
         _playlistManager = playlistManager;
         _logger = logger;
         _providerManager = providerManager;
+        _libraryManager = libraryManager;
     }
 
     /// <inheritdoc />
@@ -111,12 +114,15 @@ public class CleanupCollectionAndPlaylistPathsTask : IScheduledTask
         List<LinkedChild>? itemsToRemove = null;
         foreach (var linkedChild in folder.LinkedChildren)
         {
-            var path = linkedChild.Path;
-            if (!File.Exists(path) && !Directory.Exists(path))
+            if (linkedChild.ItemId.HasValue
+                && !linkedChild.ItemId.Value.IsEmpty()
+                && _libraryManager.GetItemById(linkedChild.ItemId.Value) is not null)
             {
-                _logger.LogInformation("Item in {FolderName} cannot be found at {ItemPath}", folder.Name, path);
-                (itemsToRemove ??= new List<LinkedChild>()).Add(linkedChild);
+                continue;
             }
+
+            _logger.LogInformation("Item in {FolderName} with ItemId {ItemId} no longer exists in library", folder.Name, linkedChild.ItemId);
+            (itemsToRemove ??= []).Add(linkedChild);
         }
 
         if (itemsToRemove is not null)
diff --git a/Emby.Server.Implementations/Session/SessionManager.cs b/Emby.Server.Implementations/Session/SessionManager.cs
index cf2ca047cf..6f576146e4 100644
--- a/Emby.Server.Implementations/Session/SessionManager.cs
+++ b/Emby.Server.Implementations/Session/SessionManager.cs
@@ -1820,7 +1820,6 @@ namespace Emby.Server.Implementations.Session
                 fields.Remove(ItemFields.Settings);
                 fields.Remove(ItemFields.SortName);
                 fields.Remove(ItemFields.Tags);
-                fields.Remove(ItemFields.ExtraIds);
 
                 dtoOptions.Fields = fields.ToArray();
 
diff --git a/Emby.Server.Implementations/TV/TVSeriesManager.cs b/Emby.Server.Implementations/TV/TVSeriesManager.cs
index cd98dbe86e..ebabb4ca2f 100644
--- a/Emby.Server.Implementations/TV/TVSeriesManager.cs
+++ b/Emby.Server.Implementations/TV/TVSeriesManager.cs
@@ -47,7 +47,7 @@ namespace Emby.Server.Implementations.TV
 
             if (!string.IsNullOrEmpty(presentationUniqueKey))
             {
-                return GetResult(GetNextUpEpisodes(query, user, new[] { presentationUniqueKey }, options), query);
+                return GetNextUpBatched(query, user, [presentationUniqueKey], options);
             }
 
             BaseItem[] parents;
@@ -58,11 +58,11 @@ namespace Emby.Server.Implementations.TV
 
                 if (parent is not null)
                 {
-                    parents = new[] { parent };
+                    parents = [parent];
                 }
                 else
                 {
-                    parents = Array.Empty<BaseItem>();
+                    parents = [];
                 }
             }
             else
@@ -93,7 +93,7 @@ namespace Emby.Server.Implementations.TV
 
             if (!string.IsNullOrEmpty(presentationUniqueKey))
             {
-                return GetResult(GetNextUpEpisodes(request, user, [presentationUniqueKey], options), request);
+                return GetNextUpBatched(request, user, [presentationUniqueKey], options);
             }
 
             if (limit.HasValue)
@@ -103,151 +103,138 @@ namespace Emby.Server.Implementations.TV
 
             var nextUpSeriesKeys = _libraryManager.GetNextUpSeriesKeys(new InternalItemsQuery(user) { Limit = limit }, parentsFolders, request.NextUpDateCutoff);
 
-            var episodes = GetNextUpEpisodes(request, user, nextUpSeriesKeys, options);
-
-            return GetResult(episodes, request);
+            return GetNextUpBatched(request, user, nextUpSeriesKeys, options);
         }
 
-        private IEnumerable<Episode> GetNextUpEpisodes(NextUpQuery request, User user, IReadOnlyList<string> seriesKeys, DtoOptions dtoOptions)
+        private QueryResult<BaseItem> GetNextUpBatched(NextUpQuery request, User user, IReadOnlyList<string> seriesKeys, DtoOptions dtoOptions)
         {
-            var allNextUp = seriesKeys.Select(i => GetNextUp(i, user, dtoOptions, request.EnableResumable, false));
-
-            if (request.EnableRewatching)
+            if (seriesKeys.Count == 0)
             {
-                allNextUp = allNextUp
-                    .Concat(seriesKeys.Select(i => GetNextUp(i, user, dtoOptions, false, true)))
-                    .OrderByDescending(i => i.LastWatchedDate);
+                return new QueryResult<BaseItem>();
             }
 
-            return allNextUp
-                .Select(i => i.GetEpisodeFunction())
-                .Where(i => i is not null)!;
-        }
-
-        private static string GetUniqueSeriesKey(Series series)
-        {
-            return series.GetPresentationUniqueKey();
-        }
+            var includeSpecials = _configurationManager.Configuration.DisplaySpecialsWithinSeasons;
+            var includeRewatching = request.EnableRewatching;
 
-        /// <summary>
-        /// Gets the next up.
-        /// </summary>
-        /// <returns>Task{Episode}.</returns>
-        private (DateTime LastWatchedDate, Func<Episode?> GetEpisodeFunction) GetNextUp(string seriesKey, User user, DtoOptions dtoOptions, bool includeResumable, bool includePlayed)
-        {
-            var lastQuery = new InternalItemsQuery(user)
+            var query = new InternalItemsQuery(user)
             {
-                AncestorWithPresentationUniqueKey = null,
-                SeriesPresentationUniqueKey = seriesKey,
-                IncludeItemTypes = [BaseItemKind.Episode],
-                IsPlayed = true,
-                Limit = 1,
-                ParentIndexNumberNotEquals = 0,
-                DtoOptions = new DtoOptions
-                {
-                    Fields = [ItemFields.SortName],
-                    EnableImages = false
-                }
+                DtoOptions = dtoOptions
             };
 
-            // If including played results, sort first by date played and then by season and episode numbers
-            lastQuery.OrderBy = includePlayed
-                ? new[] { (ItemSortBy.DatePlayed, SortOrder.Descending), (ItemSortBy.ParentIndexNumber, SortOrder.Descending), (ItemSortBy.IndexNumber, SortOrder.Descending) }
-                : new[] { (ItemSortBy.ParentIndexNumber, SortOrder.Descending), (ItemSortBy.IndexNumber, SortOrder.Descending) };
+            var batchResult = _libraryManager.GetNextUpEpisodesBatch(query, seriesKeys, includeSpecials, includeRewatching);
 
-            var lastWatchedEpisode = _libraryManager.GetItemList(lastQuery).Cast<Episode>().FirstOrDefault();
+            var nextUpList = new List<(DateTime LastWatchedDate, Episode Episode)>();
 
-            Episode? GetEpisode()
+            foreach (var seriesKey in seriesKeys)
             {
-                var nextQuery = new InternalItemsQuery(user)
+                if (!batchResult.TryGetValue(seriesKey, out var result))
                 {
-                    AncestorWithPresentationUniqueKey = null,
-                    SeriesPresentationUniqueKey = seriesKey,
-                    IncludeItemTypes = [BaseItemKind.Episode],
-                    OrderBy = [(ItemSortBy.ParentIndexNumber, SortOrder.Ascending), (ItemSortBy.IndexNumber, SortOrder.Ascending)],
-                    Limit = 1,
-                    IsPlayed = includePlayed,
-                    IsVirtualItem = false,
-                    ParentIndexNumberNotEquals = 0,
-                    DtoOptions = dtoOptions
-                };
-
-                // Locate the next up episode based on the last watched episode's season and episode number
-                var lastWatchedParentIndexNumber = lastWatchedEpisode?.ParentIndexNumber;
-                var lastWatchedIndexNumber = lastWatchedEpisode?.IndexNumberEnd ?? lastWatchedEpisode?.IndexNumber;
-                if (lastWatchedParentIndexNumber.HasValue && lastWatchedIndexNumber.HasValue)
-                {
-                    nextQuery.MinParentAndIndexNumber = (lastWatchedParentIndexNumber.Value, lastWatchedIndexNumber.Value + 1);
+                    continue;
                 }
 
-                var nextEpisode = _libraryManager.GetItemList(nextQuery).Cast<Episode>().FirstOrDefault();
+                var nextEpisode = DetermineNextEpisode(result, user, includeSpecials, request.EnableResumable, false);
 
-                if (_configurationManager.Configuration.DisplaySpecialsWithinSeasons)
+                if (nextEpisode is not null)
                 {
-                    var consideredEpisodes = _libraryManager.GetItemList(new InternalItemsQuery(user)
+                    DateTime lastWatchedDate = DateTime.MinValue;
+                    if (result.LastWatched is not null)
                     {
-                        AncestorWithPresentationUniqueKey = null,
-                        SeriesPresentationUniqueKey = seriesKey,
-                        ParentIndexNumber = 0,
-                        IncludeItemTypes = [BaseItemKind.Episode],
-                        IsPlayed = includePlayed,
-                        IsVirtualItem = false,
-                        DtoOptions = dtoOptions
-                    })
-                    .Cast<Episode>()
-                    .Where(episode => episode.AirsBeforeSeasonNumber is not null || episode.AirsAfterSeasonNumber is not null)
-                    .ToList();
-
-                    if (lastWatchedEpisode is not null)
-                    {
-                        // Last watched episode is added, because there could be specials that aired before the last watched episode
-                        consideredEpisodes.Add(lastWatchedEpisode);
+                        var userData = _userDataManager.GetUserData(user, result.LastWatched);
+                        lastWatchedDate = userData?.LastPlayedDate ?? DateTime.MinValue.AddDays(1);
                     }
 
-                    if (nextEpisode is not null)
-                    {
-                        consideredEpisodes.Add(nextEpisode);
-                    }
+                    nextUpList.Add((lastWatchedDate, nextEpisode));
+                }
 
-                    var sortedConsideredEpisodes = _libraryManager.Sort(consideredEpisodes, user, [(ItemSortBy.AiredEpisodeOrder, SortOrder.Ascending)])
-                        .Cast<Episode>();
-                    if (lastWatchedEpisode is not null)
+                if (includeRewatching)
+                {
+                    var nextPlayedEpisode = DetermineNextEpisodeForRewatching(result, user, includeSpecials);
+
+                    if (nextPlayedEpisode is not null)
                     {
-                        sortedConsideredEpisodes = sortedConsideredEpisodes.SkipWhile(episode => !episode.Id.Equals(lastWatchedEpisode.Id)).Skip(1);
+                        DateTime rewatchLastWatchedDate = DateTime.MinValue;
+                        if (result.LastWatchedForRewatching is not null)
+                        {
+                            var userData = _userDataManager.GetUserData(user, result.LastWatchedForRewatching);
+                            rewatchLastWatchedDate = userData?.LastPlayedDate ?? DateTime.MinValue.AddDays(1);
+                        }
+
+                        nextUpList.Add((rewatchLastWatchedDate, nextPlayedEpisode));
                     }
+                }
+            }
 
-                    nextEpisode = sortedConsideredEpisodes.FirstOrDefault();
+            var sortedEpisodes = nextUpList
+                .OrderByDescending(x => x.LastWatchedDate)
+                .Select(x => (BaseItem)x.Episode);
+
+            return GetResult(sortedEpisodes, request);
+        }
+
+        private Episode? DetermineNextEpisode(
+            MediaBrowser.Controller.Persistence.NextUpEpisodeBatchResult result,
+            User user,
+            bool includeSpecials,
+            bool includeResumable,
+            bool includePlayed)
+        {
+            var nextEpisode = (includePlayed ? result.NextPlayedForRewatching : result.NextUp) as Episode;
+            var lastWatchedEpisode = (includePlayed ? result.LastWatchedForRewatching : result.LastWatched) as Episode;
+
+            if (includeSpecials && result.Specials?.Count > 0)
+            {
+                var consideredEpisodes = result.Specials
+                    .Cast<Episode>()
+                    .Where(episode => episode.AirsBeforeSeasonNumber is not null || episode.AirsAfterSeasonNumber is not null)
+                    .ToList();
+
+                if (lastWatchedEpisode is not null)
+                {
+                    consideredEpisodes.Add(lastWatchedEpisode);
                 }
 
-                if (nextEpisode is not null && !includeResumable)
+                if (nextEpisode is not null)
                 {
-                    var userData = _userDataManager.GetUserData(user, nextEpisode);
+                    consideredEpisodes.Add(nextEpisode);
+                }
 
-                    if (userData?.PlaybackPositionTicks > 0)
+                if (consideredEpisodes.Count > 0)
+                {
+                    var sortedEpisodes = _libraryManager.Sort(consideredEpisodes, user, [(ItemSortBy.AiredEpisodeOrder, SortOrder.Ascending)])
+                        .Cast<Episode>();
+
+                    if (lastWatchedEpisode is not null)
                     {
-                        return null;
+                        sortedEpisodes = sortedEpisodes.SkipWhile(episode => !episode.Id.Equals(lastWatchedEpisode.Id)).Skip(1);
                     }
-                }
 
-                return nextEpisode;
+                    nextEpisode = sortedEpisodes.FirstOrDefault();
+                }
             }
 
-            if (lastWatchedEpisode is not null)
+            if (nextEpisode is not null && !includeResumable)
             {
-                var userData = _userDataManager.GetUserData(user, lastWatchedEpisode);
-
-                if (userData is null)
+                var userData = _userDataManager.GetUserData(user, nextEpisode);
+                if (userData?.PlaybackPositionTicks > 0)
                 {
-                    return (DateTime.MinValue, GetEpisode);
+                    return null;
                 }
+            }
 
-                var lastWatchedDate = userData.LastPlayedDate ?? DateTime.MinValue.AddDays(1);
+            return nextEpisode;
+        }
 
-                return (lastWatchedDate, GetEpisode);
-            }
+        private Episode? DetermineNextEpisodeForRewatching(
+            MediaBrowser.Controller.Persistence.NextUpEpisodeBatchResult result,
+            User user,
+            bool includeSpecials)
+        {
+            return DetermineNextEpisode(result, user, includeSpecials, includeResumable: false, includePlayed: true);
+        }
 
-            // Return the first episode
-            return (DateTime.MinValue, GetEpisode);
+        private static string GetUniqueSeriesKey(Series series)
+        {
+            return series.GetPresentationUniqueKey();
         }
 
         private static QueryResult<BaseItem> GetResult(IEnumerable<BaseItem> items, NextUpQuery query)