diff --git a/Emby.Server.Implementations/Dto/DtoService.cs b/Emby.Server.Implementations/Dto/DtoService.cs
index 062c19a1d4..6fa057702c 100644
--- a/Emby.Server.Implementations/Dto/DtoService.cs
+++ b/Emby.Server.Implementations/Dto/DtoService.cs
@@ -261,7 +261,7 @@ namespace Emby.Server.Implementations.Dto
                 var versionItemIds = accessibleItems.OfType<Video>().Select(i => i.Id).ToList();
                 if (versionItemIds.Count > 0)
                 {
-                    alternateVersionItemIds = _libraryManager.GetItemsWithAlternateVersions(versionItemIds);
+                    alternateVersionItemIds = _libraryManager.GetItemIdsWithAlternateVersions(versionItemIds);
                 }
             }
 
@@ -1314,13 +1314,15 @@ namespace Emby.Server.Implementations.Dto
                 if (options.ContainsField(ItemFields.MediaSourceCount))
                 {
                     // A video with no primary version and no alternate versions always has a single
-                    // media source. When the batch has already determined this item owns no alternate
-                    // versions, skip the per-item alternate-version queries entirely (the common case).
-                    var hasNoAlternateVersions = alternateVersionItemIds is not null
-                        && !video.PrimaryVersionId.HasValue
-                        && !alternateVersionItemIds.Contains(video.Id);
+                    // media source. Only compute the count for videos that might have more: a primary
+                    // version, or membership in the batch's set of items that own alternate versions.
+                    // Without the batch we can't rule it out, so fall back to computing (the single-item
+                    // path). Everything else is the common case and keeps the default count of one.
+                    var mayHaveAlternateVersions = alternateVersionItemIds is null
+                        || video.PrimaryVersionId.HasValue
+                        || alternateVersionItemIds.Contains(video.Id);
 
-                    if (!hasNoAlternateVersions)
+                    if (mayHaveAlternateVersions)
                     {
                         // Match the per-user filtering of the media sources: versions the user cannot
                         // access are not selectable, so they must not count towards the badge either.
diff --git a/Emby.Server.Implementations/Library/LibraryManager.cs b/Emby.Server.Implementations/Library/LibraryManager.cs
index 9bb962c504..0c7c411d0c 100644
--- a/Emby.Server.Implementations/Library/LibraryManager.cs
+++ b/Emby.Server.Implementations/Library/LibraryManager.cs
@@ -2235,9 +2235,9 @@ namespace Emby.Server.Implementations.Library
         }
 
         /// <inheritdoc />
-        public IReadOnlySet<Guid> GetItemsWithAlternateVersions(IReadOnlyList<Guid> itemIds)
+        public IReadOnlySet<Guid> GetItemIdsWithAlternateVersions(IReadOnlyList<Guid> itemIds)
         {
-            return _linkedChildrenService.GetItemsWithAlternateVersions(itemIds);
+            return _linkedChildrenService.GetItemIdsWithAlternateVersions(itemIds);
         }
 
         /// <inheritdoc />
diff --git a/Jellyfin.Server.Implementations/Item/LinkedChildrenService.cs b/Jellyfin.Server.Implementations/Item/LinkedChildrenService.cs
index 2452f8e3c6..a96e941c88 100644
--- a/Jellyfin.Server.Implementations/Item/LinkedChildrenService.cs
+++ b/Jellyfin.Server.Implementations/Item/LinkedChildrenService.cs
@@ -60,7 +60,7 @@ public class LinkedChildrenService : ILinkedChildrenService
     }
 
     /// <inheritdoc/>
-    public IReadOnlySet<Guid> GetItemsWithAlternateVersions(IReadOnlyList<Guid> itemIds)
+    public IReadOnlySet<Guid> GetItemIdsWithAlternateVersions(IReadOnlyList<Guid> itemIds)
     {
         if (itemIds.Count == 0)
         {
@@ -69,15 +69,13 @@ public class LinkedChildrenService : ILinkedChildrenService
 
         using var dbContext = _dbProvider.CreateDbContext();
 
-        var parentIds = dbContext.LinkedChildren
+        return dbContext.LinkedChildren
             .Where(lc => (lc.ChildType == DbLinkedChildType.LocalAlternateVersion
                     || lc.ChildType == DbLinkedChildType.LinkedAlternateVersion)
                 && itemIds.Contains(lc.ParentId))
             .Select(lc => lc.ParentId)
             .Distinct()
-            .ToArray();
-
-        return parentIds.ToHashSet();
+            .ToHashSet();
     }
 
     /// <inheritdoc/>
diff --git a/MediaBrowser.Controller/Library/ILibraryManager.cs b/MediaBrowser.Controller/Library/ILibraryManager.cs
index f6bd948b99..ca686fbd9d 100644
--- a/MediaBrowser.Controller/Library/ILibraryManager.cs
+++ b/MediaBrowser.Controller/Library/ILibraryManager.cs
@@ -261,7 +261,7 @@ namespace MediaBrowser.Controller.Library
         /// </summary>
         /// <param name="itemIds">The item IDs to check.</param>
         /// <returns>The set of item IDs that have alternate versions.</returns>
-        IReadOnlySet<Guid> GetItemsWithAlternateVersions(IReadOnlyList<Guid> itemIds);
+        IReadOnlySet<Guid> GetItemIdsWithAlternateVersions(IReadOnlyList<Guid> itemIds);
 
         /// <summary>
         /// Creates or updates a LinkedChild entry linking a parent to a child item.
diff --git a/MediaBrowser.Controller/Persistence/ILinkedChildrenService.cs b/MediaBrowser.Controller/Persistence/ILinkedChildrenService.cs
index c1fe3231f4..79c29410e4 100644
--- a/MediaBrowser.Controller/Persistence/ILinkedChildrenService.cs
+++ b/MediaBrowser.Controller/Persistence/ILinkedChildrenService.cs
@@ -26,7 +26,7 @@ public interface ILinkedChildrenService
     /// </summary>
     /// <param name="itemIds">The item IDs to check.</param>
     /// <returns>The set of item IDs that have alternate versions.</returns>
-    IReadOnlySet<Guid> GetItemsWithAlternateVersions(IReadOnlyList<Guid> itemIds);
+    IReadOnlySet<Guid> GetItemIdsWithAlternateVersions(IReadOnlyList<Guid> itemIds);
 
     /// <summary>
     /// Gets all artist matches from the database.
diff --git a/tests/Jellyfin.Server.Implementations.Tests/Dto/DtoServiceImageInheritanceTests.cs b/tests/Jellyfin.Server.Implementations.Tests/Dto/DtoServiceImageInheritanceTests.cs
index fa94250287..6a3dcab57a 100644
--- a/tests/Jellyfin.Server.Implementations.Tests/Dto/DtoServiceImageInheritanceTests.cs
+++ b/tests/Jellyfin.Server.Implementations.Tests/Dto/DtoServiceImageInheritanceTests.cs
@@ -222,11 +222,11 @@ public class DtoServiceImageInheritanceTests
         var libraryManager = new Mock<ILibraryManager>();
 
         // DtoService detects which videos own alternate versions in ONE batch
-        // (GetItemsWithAlternateVersions) before the per-item loop. Videos absent from that set have a
+        // (GetItemIdsWithAlternateVersions) before the per-item loop. Videos absent from that set have a
         // single media source, so the per-item GetLinkedAlternateVersions/GetLocalAlternateVersionIds
         // queries (the N+1) must be skipped entirely. Here neither movie has alternate versions.
         libraryManager
-            .Setup(x => x.GetItemsWithAlternateVersions(It.IsAny<IReadOnlyList<Guid>>()))
+            .Setup(x => x.GetItemIdsWithAlternateVersions(It.IsAny<IReadOnlyList<Guid>>()))
             .Returns(new HashSet<Guid>());
 
         var dtoService = BuildDtoService(libraryManager);
@@ -236,13 +236,54 @@ public class DtoServiceImageInheritanceTests
 
         Assert.Equal(2, dtos.Count);
 
+        // A single media source is the default, so the count is left unset (the client treats null as one).
+        foreach (var dto in dtos)
+        {
+            Assert.Null(dto.MediaSourceCount);
+        }
+
         // The alternate-version check is batched once for the whole set, and the per-item lookups are
         // never reached because the batch already ruled out alternate versions.
-        libraryManager.Verify(x => x.GetItemsWithAlternateVersions(It.IsAny<IReadOnlyList<Guid>>()), Times.Once);
+        libraryManager.Verify(x => x.GetItemIdsWithAlternateVersions(It.IsAny<IReadOnlyList<Guid>>()), Times.Once);
         libraryManager.Verify(x => x.GetLinkedAlternateVersions(It.IsAny<Video>()), Times.Never);
         libraryManager.Verify(x => x.GetLocalAlternateVersionIds(It.IsAny<Video>()), Times.Never);
     }
 
+    [Fact]
+    public void GetBaseItemDtos_VideoInAlternateVersionBatch_ResolvesRealCount()
+    {
+        var movie = new Movie
+        {
+            Id = Guid.NewGuid(),
+            Name = "Movie",
+            ImageInfos = []
+        };
+
+        var libraryManager = new Mock<ILibraryManager>();
+
+        // This movie IS in the batch set, so the fast path must not short-circuit it: the per-item
+        // lookups still run and the count is computed exactly as it was before batching. Two linked
+        // alternate versions plus the movie itself is a count of three.
+        libraryManager
+            .Setup(x => x.GetItemIdsWithAlternateVersions(It.IsAny<IReadOnlyList<Guid>>()))
+            .Returns(new HashSet<Guid> { movie.Id });
+        libraryManager
+            .Setup(x => x.GetLinkedAlternateVersions(It.IsAny<Video>()))
+            .Returns([new Movie { Id = Guid.NewGuid() }, new Movie { Id = Guid.NewGuid() }]);
+        libraryManager
+            .Setup(x => x.GetLocalAlternateVersionIds(It.IsAny<Video>()))
+            .Returns([]);
+
+        var dtoService = BuildDtoService(libraryManager);
+
+        var options = new DtoOptions(false) { Fields = [ItemFields.MediaSourceCount] };
+        var dtos = dtoService.GetBaseItemDtos([movie], options);
+
+        Assert.Single(dtos);
+        Assert.Equal(3, dtos[0].MediaSourceCount);
+        libraryManager.Verify(x => x.GetItemIdsWithAlternateVersions(It.IsAny<IReadOnlyList<Guid>>()), Times.Once);
+    }
+
     private static DtoService BuildDtoService(BaseItem displayParent)
     {
         var libraryManager = new Mock<ILibraryManager>();