1 files changed, 45 insertions, 0 deletions
diff --git a/Emby.Server.Implementations/Library/LibraryManager.cs b/Emby.Server.Implementations/Library/LibraryManager.cs
index 11f1496086..f2480679d9 100644
--- a/Emby.Server.Implementations/Library/LibraryManager.cs
+++ b/Emby.Server.Implementations/Library/LibraryManager.cs
@@ -13,6 +13,7 @@ using System.Threading.Tasks;
 using BitFaster.Caching.Lru;
 using Emby.Naming.Common;
 using Emby.Naming.TV;
+using Emby.Naming.Video;
 using Emby.Server.Implementations.Library.Resolvers;
 using Emby.Server.Implementations.Library.Validators;
 using Emby.Server.Implementations.Playlists;
@@ -787,6 +788,42 @@ namespace Emby.Server.Implementations.Library
             CollectionType? collectionType = null)
             => ResolvePath(fileInfo, directoryService ?? new DirectoryService(_fileSystem), null, parent, collectionType);
 
+        private void SetAdditionalPartsFromStack(Video altVideo, string path)
+        {
+            if (altVideo.AdditionalParts is { Length: > 0 })
+            {
+                return;
+            }
+
+            var directory = Path.GetDirectoryName(path);
+            if (string.IsNullOrEmpty(directory))
+            {
+                return;
+            }
+
+            IEnumerable<FileSystemMetadata> siblings;
+            try
+            {
+                siblings = _fileSystem.GetFiles(directory);
+            }
+            catch (Exception ex)
+            {
+                _logger.LogWarning(ex, "Failed to enumerate siblings to detect stack for {Path}", path);
+                return;
+            }
+
+            var stacks = StackResolver.Resolve(siblings, _namingOptions);
+            foreach (var stack in stacks)
+            {
+                if (stack.Files.Count > 1
+                    && string.Equals(stack.Files[0], path, StringComparison.OrdinalIgnoreCase))
+                {
+                    altVideo.AdditionalParts = stack.Files.Skip(1).ToArray();
+                    return;
+                }
+            }
+        }
+
         /// <inheritdoc />
         public Video? ResolveAlternateVersion(string path, Type expectedVideoType, Folder? parent, CollectionType? collectionType)
         {
@@ -2307,6 +2344,10 @@ namespace Emby.Server.Implementations.Library
                             {
                                 altVideo.OwnerId = video.Id;
                                 altVideo.SetPrimaryVersionId(video.Id);
+                                // ResolveAlternateVersion only sees the alternate's primary file.
+                                // If the alternate is itself a stack (e.g. 1080p part1 + part2),
+                                // detect its parts from sibling files so its AdditionalParts persist.
+                                SetAdditionalPartsFromStack(altVideo, path);
                                 allItems.Add(altVideo);
                             }
                         }
@@ -2510,6 +2551,10 @@ namespace Emby.Server.Implementations.Library
                             {
                                 altVideo.OwnerId = video.Id;
                                 altVideo.SetPrimaryVersionId(video.Id);
+                                // ResolveAlternateVersion only sees the alternate's primary file.
+                                // If the alternate is itself a stack (e.g. 1080p part1 + part2),
+                                // detect its parts from sibling files so its AdditionalParts persist.
+                                SetAdditionalPartsFromStack(altVideo, path);
                                 allItems.Add(altVideo);
                             }
                         }