Merge branch 'master' into fix/create_library_thumbs_on_first_scan

16 files changed, 1515 insertions, 22 deletions

diff --git a/tests/Jellyfin.Server.Implementations.Tests/Dto/DtoServiceTests.cs b/tests/Jellyfin.Server.Implementations.Tests/Dto/DtoServiceTests.cs
index a5de0a4416..9c247d54b9 100644
--- a/tests/Jellyfin.Server.Implementations.Tests/Dto/DtoServiceTests.cs
+++ b/tests/Jellyfin.Server.Implementations.Tests/Dto/DtoServiceTests.cs
@@ -11,6 +11,7 @@ using MediaBrowser.Controller.LiveTv;
 using MediaBrowser.Controller.Providers;
 using MediaBrowser.Controller.Trickplay;
 using MediaBrowser.Model.Entities;
+using MediaBrowser.Model.Querying;
 using Microsoft.Extensions.Logging.Abstractions;
 using Moq;
 using Xunit;
@@ -56,57 +57,63 @@ public class DtoServiceTests
     }
 
     [Fact]
-    public void GetBaseItemDto_PreferEpisodeParentPoster_PrefersSeasonPosterOverEpisodeAndSeries()
+    public void GetBaseItemDto_Episode_AttachesSeasonPosterAsParentPrimaryImage()
     {
-        var (episode, season, series) = BuildEpisode(seasonHasPoster: true);
-        var options = new DtoOptions(false) { PreferEpisodeParentPoster = true };
+        var (episode, season, _) = BuildEpisode(seasonHasPoster: true);
+        var options = new DtoOptions(false) { Fields = [ItemFields.PrimaryImageAspectRatio] };
 
         var dto = _dtoService.GetBaseItemDto(episode, options);
 
-        // The episode's own 16:9 primary is dropped in favor of the season's portrait poster.
-        Assert.False(dto.ImageTags is not null && dto.ImageTags.ContainsKey(ImageType.Primary));
-        Assert.Null(dto.SeriesPrimaryImageTag);
+        // The season poster is attached additively; the episode keeps its own primary and 16:9 ratio,
+        // and clients decide per view whether to prefer the parent/series poster over the episode still.
+        Assert.NotNull(dto.ImageTags);
+        Assert.True(dto.ImageTags.ContainsKey(ImageType.Primary));
+        Assert.NotNull(dto.SeriesPrimaryImageTag);
         Assert.Equal(season.Id, dto.ParentPrimaryImageItemId);
         Assert.Equal("tag:" + season.GetImageInfo(ImageType.Primary, 0)!.Path, dto.ParentPrimaryImageTag);
-        // Aspect ratio follows the (portrait) poster, not the episode's 16:9 image.
-        Assert.Equal(season.GetDefaultPrimaryImageAspectRatio(), dto.PrimaryImageAspectRatio);
+        // Aspect ratio stays the episode's own image, not the poster's.
+        Assert.Equal(episode.GetDefaultPrimaryImageAspectRatio(), dto.PrimaryImageAspectRatio);
     }
 
     [Fact]
-    public void GetBaseItemDto_PreferEpisodeParentPoster_FallsBackToSeriesWhenSeasonHasNoPoster()
+    public void GetBaseItemDto_Episode_ParentPrimaryImageFallsBackToSeriesWhenSeasonHasNoPoster()
     {
         var (episode, _, series) = BuildEpisode(seasonHasPoster: false);
-        var options = new DtoOptions(false) { PreferEpisodeParentPoster = true };
+        var options = new DtoOptions(false);
 
         var dto = _dtoService.GetBaseItemDto(episode, options);
 
-        Assert.False(dto.ImageTags is not null && dto.ImageTags.ContainsKey(ImageType.Primary));
-        Assert.Null(dto.SeriesPrimaryImageTag);
+        // Episode image is retained; ParentPrimaryImage falls back to the series poster.
+        Assert.NotNull(dto.ImageTags);
+        Assert.True(dto.ImageTags.ContainsKey(ImageType.Primary));
+        Assert.NotNull(dto.SeriesPrimaryImageTag);
         Assert.Equal(series.Id, dto.ParentPrimaryImageItemId);
         Assert.Equal("tag:" + series.GetImageInfo(ImageType.Primary, 0)!.Path, dto.ParentPrimaryImageTag);
     }
 
     [Fact]
-    public void GetBaseItemDto_WithoutPreferEpisodeParentPoster_KeepsEpisodePrimary()
+    public void GetBaseItemDto_Episode_WithoutParentPosters_KeepsOnlyEpisodePrimary()
     {
-        var (episode, _, _) = BuildEpisode(seasonHasPoster: true);
+        var (episode, _, _) = BuildEpisode(seasonHasPoster: false, seriesHasPoster: false);
         var options = new DtoOptions(false);
 
         var dto = _dtoService.GetBaseItemDto(episode, options);
 
-        // Default behavior: the episode keeps its own primary and exposes the series poster as a tag.
+        // With no season or series poster there is nothing to attach; the episode keeps its own primary.
         Assert.NotNull(dto.ImageTags);
         Assert.True(dto.ImageTags.ContainsKey(ImageType.Primary));
-        Assert.NotNull(dto.SeriesPrimaryImageTag);
         Assert.Null(dto.ParentPrimaryImageItemId);
     }
 
-    private (Episode Episode, Season Season, Series Series) BuildEpisode(bool seasonHasPoster)
+    private (Episode Episode, Season Season, Series Series) BuildEpisode(bool seasonHasPoster, bool seriesHasPoster = true)
     {
         // Non-local (http) paths keep aspect-ratio resolution off the image processor and on the
         // item's default ratio, which is portrait (2/3) for Season/Series and 16:9 for Episode.
         var series = new Series { Id = Guid.NewGuid(), Name = "Series" };
-        series.SetImage(new ItemImageInfo { Type = ImageType.Primary, Path = "http://test/series.jpg" }, 0);
+        if (seriesHasPoster)
+        {
+            series.SetImage(new ItemImageInfo { Type = ImageType.Primary, Path = "http://test/series.jpg" }, 0);
+        }
 
         var season = new Season { Id = Guid.NewGuid(), Name = "Season", SeriesId = series.Id };
         if (seasonHasPoster)
diff --git a/tests/Jellyfin.Server.Implementations.Tests/FullSystemBackup/BackupServiceTests.cs b/tests/Jellyfin.Server.Implementations.Tests/FullSystemBackup/BackupServiceTests.cs
new file mode 100644
index 0000000000..66c392a6ad
--- /dev/null
+++ b/tests/Jellyfin.Server.Implementations.Tests/FullSystemBackup/BackupServiceTests.cs
@@ -0,0 +1,182 @@
+using System;
+using System.IO;
+using System.IO.Compression;
+using System.Linq;
+using System.Text.Json;
+using System.Threading;
+using System.Threading.Tasks;
+using Jellyfin.Database.Implementations;
+using Jellyfin.Database.Implementations.Entities;
+using Jellyfin.Database.Implementations.Locking;
+using Jellyfin.Database.Providers.Sqlite;
+using Jellyfin.Server.Implementations.FullSystemBackup;
+using MediaBrowser.Controller;
+using MediaBrowser.Controller.Library;
+using MediaBrowser.Controller.SystemBackupService;
+using Microsoft.Data.Sqlite;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging.Abstractions;
+using Moq;
+using Xunit;
+using BaseItemKind = Jellyfin.Data.Enums.BaseItemKind;
+
+namespace Jellyfin.Server.Implementations.Tests.FullSystemBackup;
+
+/// <summary>
+/// Tests for <see cref="BackupService"/>, in particular that a single row of corrupt
+/// <see cref="KeyframeData"/> (e.g. malformed <c>KeyframeTicks</c> JSON) does not abort
+/// an otherwise healthy backup. See https://github.com/jellyfin/jellyfin/issues/17216.
+/// </summary>
+public sealed class BackupServiceTests : IDisposable
+{
+    private readonly SqliteConnection _connection;
+    private readonly DbContextOptions<JellyfinDbContext> _dbOptions;
+    private readonly string _testRoot;
+    private readonly string _backupPath;
+    private readonly string _configurationDirectoryPath;
+
+    public BackupServiceTests()
+    {
+        _connection = new SqliteConnection("Data Source=:memory:");
+        _connection.Open();
+
+        _dbOptions = new DbContextOptionsBuilder<JellyfinDbContext>()
+            .UseSqlite(_connection)
+            .Options;
+
+        using (var ctx = CreateDbContext())
+        {
+            ctx.Database.EnsureCreated();
+        }
+
+        // Use the test assembly's own output directory instead of Path.GetTempPath(). On GitHub-hosted
+        // windows-latest runners, the system temp directory lives on the constrained C: drive, which can have
+        // less than the 5GiB BackupService requires free, causing spurious failures. AppContext.BaseDirectory
+        // is under the repo checkout (the much larger D: drive on Windows runners) on all platforms.
+        _testRoot = Path.Combine(AppContext.BaseDirectory, "jellyfin-backup-service-tests-" + Guid.NewGuid().ToString("N"));
+        _backupPath = Path.Combine(_testRoot, "Backup");
+        _configurationDirectoryPath = Path.Combine(_testRoot, "Config");
+        Directory.CreateDirectory(_backupPath);
+        Directory.CreateDirectory(_configurationDirectoryPath);
+    }
+
+    public void Dispose()
+    {
+        _connection.Dispose();
+
+        if (Directory.Exists(_testRoot))
+        {
+            Directory.Delete(_testRoot, true);
+        }
+    }
+
+    [Fact]
+    public async Task CreateBackupAsync_WithCorruptKeyframeDataRow_SkipsRowAndCompletesBackup()
+    {
+        var cancellationToken = TestContext.Current.CancellationToken;
+        var validItemId = Guid.Parse("11111111-1111-1111-1111-111111111111");
+        var corruptItemId = Guid.Parse("22222222-2222-2222-2222-222222222222");
+
+        await using (var ctx = CreateDbContext())
+        {
+            // A healthy item + keyframe row, written the normal way.
+            ctx.BaseItems.Add(CreateMovieEntity(validItemId, "Good Movie"));
+            ctx.BaseItems.Add(CreateMovieEntity(corruptItemId, "Corrupt Movie"));
+            await ctx.SaveChangesAsync(cancellationToken).ConfigureAwait(true);
+
+            ctx.KeyframeData.Add(new KeyframeData
+            {
+                ItemId = validItemId,
+                TotalDuration = 60_000,
+                KeyframeTicks = [0, 1000, 2000]
+            });
+            await ctx.SaveChangesAsync(cancellationToken).ConfigureAwait(true);
+
+            // Simulate a corrupted database row: truncated JSON array for KeyframeTicks,
+            // written directly via SQL to bypass EF's normal (well-formed) write path.
+            await ctx.Database.ExecuteSqlInterpolatedAsync(
+                $"INSERT INTO KeyframeData (ItemId, TotalDuration, KeyframeTicks) VALUES ({corruptItemId.ToString()}, {5000L}, {"[1,2,3"})",
+                cancellationToken).ConfigureAwait(true);
+        }
+
+        var backupService = CreateBackupService();
+
+        var manifest = await backupService.CreateBackupAsync(new BackupOptionsDto()).ConfigureAwait(true);
+
+        Assert.True(File.Exists(manifest.Path));
+
+        using var archive = await ZipFile.OpenReadAsync(manifest.Path, cancellationToken).ConfigureAwait(true);
+        var keyframeEntry = archive.GetEntry("Database/KeyframeData.json");
+        Assert.NotNull(keyframeEntry);
+
+        await using var entryStream = await keyframeEntry!.OpenAsync(cancellationToken).ConfigureAwait(true);
+        using var document = await JsonDocument.ParseAsync(entryStream, cancellationToken: cancellationToken).ConfigureAwait(true);
+
+        var rows = document.RootElement.EnumerateArray().ToList();
+
+        // The corrupt row must be skipped, but the valid row must still make it into the backup.
+        var singleRow = Assert.Single(rows);
+        Assert.Equal(validItemId, singleRow.GetProperty("ItemId").GetGuid());
+    }
+
+    private BackupService CreateBackupService()
+    {
+        var factory = new Mock<IDbContextFactory<JellyfinDbContext>>();
+        factory.Setup(f => f.CreateDbContext()).Returns(CreateDbContext);
+        factory.Setup(f => f.CreateDbContextAsync(It.IsAny<CancellationToken>())).ReturnsAsync(CreateDbContext);
+
+        var applicationHost = new Mock<IServerApplicationHost>();
+        applicationHost.Setup(a => a.ApplicationVersion).Returns(new Version(10, 11, 0));
+
+        var applicationPaths = new Mock<IServerApplicationPaths>();
+        applicationPaths.Setup(a => a.BackupPath).Returns(_backupPath);
+        applicationPaths.Setup(a => a.ConfigurationDirectoryPath).Returns(_configurationDirectoryPath);
+        applicationPaths.Setup(a => a.DataPath).Returns(Path.Combine(_testRoot, "Data"));
+        applicationPaths.Setup(a => a.RootFolderPath).Returns(Path.Combine(_testRoot, "Root"));
+        applicationPaths.Setup(a => a.InternalMetadataPath).Returns(Path.Combine(_testRoot, "Metadata"));
+        applicationPaths.Setup(a => a.DefaultInternalMetadataPath).Returns(Path.Combine(_testRoot, "MetadataDefault"));
+
+        var jellyfinDatabaseProvider = new Mock<IJellyfinDatabaseProvider>();
+        jellyfinDatabaseProvider.Setup(p => p.RunScheduledOptimisation(It.IsAny<CancellationToken>())).Returns(Task.CompletedTask);
+        jellyfinDatabaseProvider.Setup(p => p.PurgeDatabase(It.IsAny<JellyfinDbContext>(), It.IsAny<System.Collections.Generic.IEnumerable<string>>())).Returns(Task.CompletedTask);
+
+        var applicationLifetime = new Mock<IHostApplicationLifetime>();
+
+        var libraryManager = new Mock<ILibraryManager>();
+        libraryManager.Setup(l => l.IsScanRunning).Returns(false);
+
+        return new BackupService(
+            NullLogger<BackupService>.Instance,
+            factory.Object,
+            applicationHost.Object,
+            applicationPaths.Object,
+            jellyfinDatabaseProvider.Object,
+            applicationLifetime.Object,
+            libraryManager.Object);
+    }
+
+    private static BaseItemEntity CreateMovieEntity(Guid id, string name)
+    {
+        return new BaseItemEntity
+        {
+            Id = id,
+            Type = "Movie",
+            Name = name,
+            PresentationUniqueKey = id.ToString("N"),
+            MediaType = "Video",
+            IsMovie = true,
+            IsFolder = false,
+            IsVirtualItem = false
+        };
+    }
+
+    private JellyfinDbContext CreateDbContext()
+    {
+        return new JellyfinDbContext(
+            _dbOptions,
+            NullLogger<JellyfinDbContext>.Instance,
+            new SqliteDatabaseProvider(null!, NullLogger<SqliteDatabaseProvider>.Instance),
+            new NoLockBehavior(NullLogger<NoLockBehavior>.Instance));
+    }
+}
diff --git a/tests/Jellyfin.Server.Implementations.Tests/IO/ManagedFileSystemTests.cs b/tests/Jellyfin.Server.Implementations.Tests/IO/ManagedFileSystemTests.cs
index c06279af2d..6cadfacce8 100644
--- a/tests/Jellyfin.Server.Implementations.Tests/IO/ManagedFileSystemTests.cs
+++ b/tests/Jellyfin.Server.Implementations.Tests/IO/ManagedFileSystemTests.cs
@@ -10,7 +10,7 @@ using Xunit;
 
 namespace Jellyfin.Server.Implementations.Tests.IO;
 
-public class ManagedFileSystemTests
+public partial class ManagedFileSystemTests
 {
     private readonly IFixture _fixture;
     private readonly ManagedFileSystem _sut;
@@ -117,7 +117,7 @@ public class ManagedFileSystemTests
     }
 
     [SuppressMessage("Naming Rules", "SA1300:ElementMustBeginWithUpperCaseLetter", Justification = "Have to")]
-    [DllImport("libc", SetLastError = true, CharSet = CharSet.Ansi)]
+    [LibraryImport("libc", SetLastError = true)]
     [DefaultDllImportSearchPaths(DllImportSearchPath.UserDirectories)]
-    private static extern int symlink(string target, string linkpath);
+    private static partial int symlink([MarshalAs(UnmanagedType.LPStr)] string target, [MarshalAs(UnmanagedType.LPStr)] string linkpath);
 }
diff --git a/tests/Jellyfin.Server.Implementations.Tests/Item/AlternateVersionQueryTranslationTests.cs b/tests/Jellyfin.Server.Implementations.Tests/Item/AlternateVersionQueryTranslationTests.cs
new file mode 100644
index 0000000000..b7fca74310
--- /dev/null
+++ b/tests/Jellyfin.Server.Implementations.Tests/Item/AlternateVersionQueryTranslationTests.cs
@@ -0,0 +1,237 @@
+#pragma warning disable RS0030 // Do not use banned APIs: Guid == is required inside EF expression trees to mirror the production query shapes.
+
+using System;
+using System.Linq;
+using Jellyfin.Database.Implementations;
+using Jellyfin.Database.Implementations.Entities;
+using Jellyfin.Database.Implementations.Locking;
+using Jellyfin.Database.Providers.Sqlite;
+using Microsoft.Data.Sqlite;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging.Abstractions;
+using Xunit;
+
+namespace Jellyfin.Server.Implementations.Tests.Item;
+
+/// <summary>
+/// Verifies that the alternate-version-aware query shapes used by the resume filter
+/// (BaseItemRepository.TranslateQuery) and the DatePlayed ordering (OrderMapper) translate
+/// and evaluate correctly on the SQLite provider.
+/// </summary>
+public sealed class AlternateVersionQueryTranslationTests : IDisposable
+{
+    private readonly SqliteConnection _connection;
+    private readonly DbContextOptions<JellyfinDbContext> _dbOptions;
+
+    public AlternateVersionQueryTranslationTests()
+    {
+        _connection = new SqliteConnection("Data Source=:memory:");
+        _connection.Open();
+
+        _dbOptions = new DbContextOptionsBuilder<JellyfinDbContext>()
+            .UseSqlite(_connection)
+            .Options;
+
+        using var ctx = CreateDbContext();
+        ctx.Database.EnsureCreated();
+    }
+
+    [Fact]
+    public void ResumeFilter_VersionProgress_SurfacesPlayedVersion()
+    {
+        Guid userId, primaryId, versionId, otherId;
+
+        using (var ctx = CreateDbContext())
+        {
+            (userId, primaryId, versionId, otherId) = Seed(ctx);
+        }
+
+        using (var ctx = CreateDbContext())
+        {
+            var inProgress = ctx.UserData
+                .Where(ud => ud.UserId == userId && ud.PlaybackPositionTicks > 0);
+
+            // Scope to the seeded items; EnsureCreated also seeds a placeholder row.
+            var seededIds = new[] { primaryId, versionId, otherId };
+
+            // Mirrors the resumable=true filter in BaseItemRepository.TranslateQuery.
+            var inProgressIds = inProgress.Select(ud => ud.ItemId);
+            var resumable = ctx.BaseItems
+                .Where(e => seededIds.Contains(e.Id))
+                .Where(e => inProgressIds.Contains(e.Id))
+                .Where(e => !ctx.BaseItems
+                    .Where(s => s.Id != e.Id
+                        && inProgressIds.Contains(s.Id)
+                        && (s.PrimaryVersionId ?? s.Id) == (e.PrimaryVersionId ?? e.Id))
+                    .Any(s =>
+                        inProgress.Where(su => su.ItemId == s.Id).Max(su => su.LastPlayedDate)
+                            > inProgress.Where(eu => eu.ItemId == e.Id).Max(eu => eu.LastPlayedDate)
+                        || (inProgress.Where(su => su.ItemId == s.Id).Max(su => su.LastPlayedDate)
+                                == inProgress.Where(eu => eu.ItemId == e.Id).Max(eu => eu.LastPlayedDate)
+                            && s.Id.CompareTo(e.Id) < 0)))
+                .Select(e => e.Id)
+                .ToList();
+
+            Assert.Equal([versionId], resumable);
+
+            // The not-resumable direction keeps primaries only.
+            var resumableMovieIds = inProgress
+                .Join(ctx.BaseItems, ud => ud.ItemId, bi => bi.Id, (ud, bi) => bi.PrimaryVersionId ?? bi.Id);
+            var notResumable = ctx.BaseItems
+                .Where(e => seededIds.Contains(e.Id) && e.PrimaryVersionId == null)
+                .Where(e => !resumableMovieIds.Contains(e.Id))
+                .Select(e => e.Id)
+                .ToList();
+
+            Assert.Equal([otherId], notResumable);
+        }
+    }
+
+    [Fact]
+    public void ResumeFilter_TiedLastPlayedDate_KeepsSingleVersion()
+    {
+        Guid userId, primaryId, versionAId, versionBId;
+
+        using (var ctx = CreateDbContext())
+        {
+            (userId, primaryId, versionAId, versionBId) = SeedTiedVersions(ctx);
+        }
+
+        using (var ctx = CreateDbContext())
+        {
+            var inProgress = ctx.UserData
+                .Where(ud => ud.UserId == userId && ud.PlaybackPositionTicks > 0);
+
+            var seededIds = new[] { primaryId, versionAId, versionBId };
+            var inProgressIds = inProgress.Select(ud => ud.ItemId);
+
+            // The exact production dedup, including the Guid.CompareTo tie-break. This asserts the
+            // expression translates on SQLite and that two versions sharing an identical LastPlayedDate
+            // collapse to a single row instead of double-listing the item in Continue Watching.
+            var resumable = ctx.BaseItems
+                .Where(e => seededIds.Contains(e.Id))
+                .Where(e => inProgressIds.Contains(e.Id))
+                .Where(e => !ctx.BaseItems
+                    .Where(s => s.Id != e.Id
+                        && inProgressIds.Contains(s.Id)
+                        && (s.PrimaryVersionId ?? s.Id) == (e.PrimaryVersionId ?? e.Id))
+                    .Any(s =>
+                        inProgress.Where(su => su.ItemId == s.Id).Max(su => su.LastPlayedDate)
+                            > inProgress.Where(eu => eu.ItemId == e.Id).Max(eu => eu.LastPlayedDate)
+                        || (inProgress.Where(su => su.ItemId == s.Id).Max(su => su.LastPlayedDate)
+                                == inProgress.Where(eu => eu.ItemId == e.Id).Max(eu => eu.LastPlayedDate)
+                            && s.Id.CompareTo(e.Id) < 0)))
+                .Select(e => e.Id)
+                .ToList();
+
+            var survivor = Assert.Single(resumable);
+            Assert.Contains(survivor, new[] { versionAId, versionBId });
+        }
+    }
+
+    [Fact]
+    public void DatePlayedOrdering_VersionProgress_SortsPrimaryByVersionDate()
+    {
+        Guid userId, primaryId, otherId;
+
+        using (var ctx = CreateDbContext())
+        {
+            (userId, primaryId, _, otherId) = Seed(ctx);
+        }
+
+        using (var ctx = CreateDbContext())
+        {
+            // Scope to the seeded items; EnsureCreated also seeds a placeholder row.
+            var seededIds = new[] { primaryId, otherId };
+
+            // Mirrors the DatePlayed mapping in OrderMapper.
+            var ordered = ctx.BaseItems
+                .Where(e => seededIds.Contains(e.Id) && e.PrimaryVersionId == null)
+                .OrderByDescending(e => ctx.UserData
+                    .Where(w => w.UserId == userId && (w.ItemId == e.Id || w.Item!.PrimaryVersionId == e.Id))
+                    .Max(f => f.LastPlayedDate))
+                .Select(e => e.Id)
+                .ToList();
+
+            // The movie whose only progress is on its alternate version sorts before the unplayed one.
+            Assert.Equal([primaryId, otherId], ordered);
+        }
+    }
+
+    private static (Guid UserId, Guid PrimaryId, Guid VersionId, Guid OtherId) Seed(JellyfinDbContext ctx)
+    {
+        var user = new User("test", "auth-provider", "reset-provider");
+        ctx.Users.Add(user);
+
+        var primary = new BaseItemEntity { Id = Guid.NewGuid(), Type = "MediaBrowser.Controller.Entities.Movies.Movie" };
+        var version = new BaseItemEntity { Id = Guid.NewGuid(), Type = "MediaBrowser.Controller.Entities.Movies.Movie", PrimaryVersionId = primary.Id };
+        var other = new BaseItemEntity { Id = Guid.NewGuid(), Type = "MediaBrowser.Controller.Entities.Movies.Movie" };
+        ctx.BaseItems.AddRange(primary, version, other);
+
+        // Progress only on the alternate version.
+        ctx.UserData.Add(new UserData
+        {
+            ItemId = version.Id,
+            Item = version,
+            UserId = user.Id,
+            User = user,
+            CustomDataKey = version.Id.ToString("N"),
+            PlaybackPositionTicks = 1000,
+            LastPlayedDate = new DateTime(2026, 1, 2, 0, 0, 0, DateTimeKind.Utc)
+        });
+
+        ctx.SaveChanges();
+        return (user.Id, primary.Id, version.Id, other.Id);
+    }
+
+    private static (Guid UserId, Guid PrimaryId, Guid VersionAId, Guid VersionBId) SeedTiedVersions(JellyfinDbContext ctx)
+    {
+        var user = new User("test", "auth-provider", "reset-provider");
+        ctx.Users.Add(user);
+
+        var primary = new BaseItemEntity { Id = Guid.NewGuid(), Type = "MediaBrowser.Controller.Entities.Movies.Movie" };
+        var versionA = new BaseItemEntity { Id = Guid.NewGuid(), Type = "MediaBrowser.Controller.Entities.Movies.Movie", PrimaryVersionId = primary.Id };
+        var versionB = new BaseItemEntity { Id = Guid.NewGuid(), Type = "MediaBrowser.Controller.Entities.Movies.Movie", PrimaryVersionId = primary.Id };
+        ctx.BaseItems.AddRange(primary, versionA, versionB);
+
+        // Both versions in progress with the exact same LastPlayedDate - the tie that a strict '>' cannot break.
+        var tied = new DateTime(2026, 1, 2, 0, 0, 0, DateTimeKind.Utc);
+        ctx.UserData.Add(new UserData
+        {
+            ItemId = versionA.Id,
+            Item = versionA,
+            UserId = user.Id,
+            User = user,
+            CustomDataKey = versionA.Id.ToString("N"),
+            PlaybackPositionTicks = 1000,
+            LastPlayedDate = tied
+        });
+        ctx.UserData.Add(new UserData
+        {
+            ItemId = versionB.Id,
+            Item = versionB,
+            UserId = user.Id,
+            User = user,
+            CustomDataKey = versionB.Id.ToString("N"),
+            PlaybackPositionTicks = 2000,
+            LastPlayedDate = tied
+        });
+
+        ctx.SaveChanges();
+        return (user.Id, primary.Id, versionA.Id, versionB.Id);
+    }
+
+    private JellyfinDbContext CreateDbContext()
+    {
+        return new JellyfinDbContext(
+            _dbOptions,
+            NullLogger<JellyfinDbContext>.Instance,
+            new SqliteDatabaseProvider(null!, NullLogger<SqliteDatabaseProvider>.Instance),
+            new NoLockBehavior(NullLogger<NoLockBehavior>.Instance));
+    }
+
+    public void Dispose()
+    {
+        _connection.Dispose();
+    }
+}
diff --git a/tests/Jellyfin.Server.Implementations.Tests/Item/BaseItemRepositoryGroupingTests.cs b/tests/Jellyfin.Server.Implementations.Tests/Item/BaseItemRepositoryGroupingTests.cs
new file mode 100644
index 0000000000..083f725db9
--- /dev/null
+++ b/tests/Jellyfin.Server.Implementations.Tests/Item/BaseItemRepositoryGroupingTests.cs
@@ -0,0 +1,144 @@
+using System;
+using System.Linq;
+using Emby.Server.Implementations.Data;
+using Jellyfin.Database.Implementations;
+using Jellyfin.Database.Implementations.Entities;
+using Jellyfin.Database.Implementations.Locking;
+using Jellyfin.Database.Providers.Sqlite;
+using Jellyfin.Server.Implementations.Item;
+using MediaBrowser.Controller;
+using MediaBrowser.Controller.Configuration;
+using MediaBrowser.Controller.Entities;
+using MediaBrowser.Model.Configuration;
+using MediaBrowser.Model.Entities;
+using Microsoft.Data.Sqlite;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging.Abstractions;
+using Moq;
+using Xunit;
+using BaseItemKind = Jellyfin.Data.Enums.BaseItemKind;
+
+namespace Jellyfin.Server.Implementations.Tests.Item;
+
+public sealed class BaseItemRepositoryGroupingTests : IDisposable
+{
+    private readonly SqliteConnection _connection;
+    private readonly DbContextOptions<JellyfinDbContext> _dbOptions;
+    private readonly BaseItemRepository _repository;
+    private readonly string _movieTypeName;
+
+    public BaseItemRepositoryGroupingTests()
+    {
+        _connection = new SqliteConnection("Data Source=:memory:");
+        _connection.Open();
+
+        _dbOptions = new DbContextOptionsBuilder<JellyfinDbContext>()
+            .UseSqlite(_connection)
+            .Options;
+
+        using (var ctx = CreateDbContext())
+        {
+            ctx.Database.EnsureCreated();
+        }
+
+        var factory = new Mock<IDbContextFactory<JellyfinDbContext>>();
+        factory.Setup(f => f.CreateDbContext()).Returns(CreateDbContext);
+
+        var itemTypeLookup = new ItemTypeLookup();
+        _movieTypeName = itemTypeLookup.BaseItemKindNames[BaseItemKind.Movie];
+
+        var serverConfigurationManager = new Mock<IServerConfigurationManager>();
+        serverConfigurationManager.Setup(c => c.Configuration).Returns(new ServerConfiguration());
+
+        _repository = new BaseItemRepository(
+            factory.Object,
+            new Mock<IServerApplicationHost>().Object,
+            itemTypeLookup,
+            serverConfigurationManager.Object,
+            NullLogger<BaseItemRepository>.Instance);
+    }
+
+    public void Dispose()
+    {
+        _connection.Dispose();
+    }
+
+    [Fact]
+    public void GetItemList_VersionGroup_ReturnsPrimaryVersion()
+    {
+        // The alternate version sorts before the primary by id, so a plain Min(Id) per
+        // presentation key would wrongly pick the alternate as the group representative.
+        var primaryId = Guid.Parse("eeeeeeee-eeee-eeee-eeee-eeeeeeeeeeee");
+        var alternateId = Guid.Parse("11111111-1111-1111-1111-111111111111");
+        var presentationKey = primaryId.ToString("N");
+
+        using (var ctx = CreateDbContext())
+        {
+            ctx.BaseItems.Add(CreateMovieEntity(primaryId, "Movie", presentationKey, null));
+            ctx.BaseItems.Add(CreateMovieEntity(alternateId, "Movie - 1080p", presentationKey, primaryId));
+            ctx.SaveChanges();
+        }
+
+        var result = _repository.GetItemList(CreateQuery());
+
+        var item = Assert.Single(result);
+        Assert.Equal(primaryId, item.Id);
+    }
+
+    [Fact]
+    public void GetItemList_GroupWithoutPrimary_FallsBackToMinId()
+    {
+        var firstId = Guid.Parse("22222222-2222-2222-2222-222222222222");
+        var secondId = Guid.Parse("dddddddd-dddd-dddd-dddd-dddddddddddd");
+        var otherPrimaryId = Guid.Parse("cccccccc-cccc-cccc-cccc-cccccccccccc");
+        var presentationKey = otherPrimaryId.ToString("N");
+
+        using (var ctx = CreateDbContext())
+        {
+            ctx.BaseItems.Add(CreateMovieEntity(firstId, "Movie", presentationKey, otherPrimaryId));
+            ctx.BaseItems.Add(CreateMovieEntity(secondId, "Movie - 4K", presentationKey, otherPrimaryId));
+            ctx.SaveChanges();
+        }
+
+        var result = _repository.GetItemList(CreateQuery());
+
+        var item = Assert.Single(result);
+        Assert.Equal(firstId, item.Id);
+    }
+
+    private static InternalItemsQuery CreateQuery()
+    {
+        // IncludeOwnedItems keeps the alternate version rows in the query so the
+        // grouping collapse is what picks the group representative.
+        return new InternalItemsQuery(new Database.Implementations.Entities.User("test", "auth", "reset"))
+        {
+            IncludeItemTypes = [BaseItemKind.Movie],
+            IncludeOwnedItems = true
+        };
+    }
+
+    private BaseItemEntity CreateMovieEntity(Guid id, string name, string presentationKey, Guid? primaryVersionId)
+    {
+        return new BaseItemEntity
+        {
+            Id = id,
+            Type = _movieTypeName,
+            Name = name,
+            PresentationUniqueKey = presentationKey,
+            PrimaryVersionId = primaryVersionId,
+            MediaType = "Video",
+            IsMovie = true,
+            IsFolder = false,
+            IsVirtualItem = false
+        };
+    }
+
+    private JellyfinDbContext CreateDbContext()
+    {
+        return new JellyfinDbContext(
+            _dbOptions,
+            NullLogger<JellyfinDbContext>.Instance,
+            new SqliteDatabaseProvider(null!, NullLogger<SqliteDatabaseProvider>.Instance),
+            new NoLockBehavior(NullLogger<NoLockBehavior>.Instance));
+    }
+}
diff --git a/tests/Jellyfin.Server.Implementations.Tests/Jellyfin.Server.Implementations.Tests.csproj b/tests/Jellyfin.Server.Implementations.Tests/Jellyfin.Server.Implementations.Tests.csproj
index 958ffb8b6e..29de52a2ba 100644
--- a/tests/Jellyfin.Server.Implementations.Tests/Jellyfin.Server.Implementations.Tests.csproj
+++ b/tests/Jellyfin.Server.Implementations.Tests/Jellyfin.Server.Implementations.Tests.csproj
@@ -4,6 +4,7 @@
   <PropertyGroup>
     <ProjectGuid>{2E3A1B4B-4225-4AAA-8B29-0181A84E7AEE}</ProjectGuid>
     <OutputType>Exe</OutputType>
+    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/tests/Jellyfin.Server.Implementations.Tests/Library/LibraryManagerSortTests.cs b/tests/Jellyfin.Server.Implementations.Tests/Library/LibraryManagerSortTests.cs
new file mode 100644
index 0000000000..65ec41291d
--- /dev/null
+++ b/tests/Jellyfin.Server.Implementations.Tests/Library/LibraryManagerSortTests.cs
@@ -0,0 +1,89 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using AutoFixture;
+using AutoFixture.AutoMoq;
+using Emby.Naming.Common;
+using Emby.Server.Implementations.Library;
+using Emby.Server.Implementations.Sorting;
+using Jellyfin.Data.Enums;
+using Jellyfin.Database.Implementations.Enums;
+using MediaBrowser.Controller.Configuration;
+using MediaBrowser.Controller.Entities;
+using MediaBrowser.Controller.Entities.Audio;
+using MediaBrowser.Controller.Library;
+using MediaBrowser.Controller.Persistence;
+using MediaBrowser.Controller.Resolvers;
+using MediaBrowser.Controller.Sorting;
+using MediaBrowser.Model.IO;
+using Moq;
+using Xunit;
+using BaseItem = MediaBrowser.Controller.Entities.BaseItem;
+
+namespace Jellyfin.Server.Implementations.Tests.Library;
+
+public class LibraryManagerSortTests
+{
+    [Fact]
+    public void Sort_UserDependentKey_NullUser_ThrowsArgumentException()
+    {
+        var libraryManager = CreateLibraryManager(
+            new IBaseItemComparer[] { new PlayCountComparer(), new SortNameComparer() });
+
+        BaseItem[] items =
+        {
+            new Audio { Name = "Zulu", SortName = "Zulu", Id = Guid.NewGuid() },
+            new Audio { Name = "Alpha", SortName = "Alpha", Id = Guid.NewGuid() },
+        };
+
+        Assert.Throws<ArgumentException>(() => libraryManager.Sort(
+            items,
+            user: null,
+            new[] { (ItemSortBy.PlayCount, SortOrder.Descending) }).ToArray());
+    }
+
+    [Fact]
+    public void Sort_DateLastContentAdded_NullUser_OrdersByDateNotSortName()
+    {
+        var libraryManager = CreateLibraryManager(
+            new IBaseItemComparer[] { new DateLastMediaAddedComparer(), new SortNameComparer() });
+
+        BaseItem[] items =
+        {
+            MakeFolder("Alpha", new DateTime(2026, 1, 1)),
+            MakeFolder("Mike", new DateTime(2025, 1, 1)),
+            MakeFolder("Zulu", new DateTime(2024, 1, 1))
+        };
+
+        var sorted = libraryManager.Sort(
+            items,
+            user: null,
+            new[] { (ItemSortBy.DateLastContentAdded, SortOrder.Descending) }).ToArray();
+
+        Assert.Equal(new[] { "Alpha", "Mike", "Zulu" }, sorted.Select(i => i.Name));
+    }
+
+    private static Folder MakeFolder(string name, DateTime dateLastMediaAdded)
+        => new() { Name = name, Id = Guid.NewGuid(), DateLastMediaAdded = dateLastMediaAdded };
+
+    private static Emby.Server.Implementations.Library.LibraryManager CreateLibraryManager(IReadOnlyCollection<IBaseItemComparer> comparers)
+    {
+        var fixture = new Fixture().Customize(new AutoMoqCustomization());
+        fixture.Register(() => new NamingOptions());
+        var configMock = fixture.Freeze<Mock<IServerConfigurationManager>>();
+        configMock.Setup(c => c.ApplicationPaths.ProgramDataPath).Returns("/data");
+        BaseItem.ConfigurationManager ??= configMock.Object;
+        var itemRepository = fixture.Freeze<Mock<IItemRepository>>();
+        itemRepository.Setup(i => i.RetrieveItem(It.IsAny<Guid>())).Returns<BaseItem>(null);
+        var fileSystemMock = fixture.Freeze<Mock<IFileSystem>>();
+        fileSystemMock.Setup(f => f.GetFileInfo(It.IsAny<string>())).Returns<string>(path => new FileSystemMetadata { FullName = path });
+
+        return fixture.Build<Emby.Server.Implementations.Library.LibraryManager>().Do(s => s.AddParts(
+                fixture.Create<IEnumerable<IResolverIgnoreRule>>(),
+                fixture.Create<IEnumerable<IItemResolver>>(),
+                fixture.Create<IEnumerable<IIntroProvider>>(),
+                comparers,
+                fixture.Create<IEnumerable<ILibraryPostScanTask>>()))
+            .Create();
+    }
+}
diff --git a/tests/Jellyfin.Server.Implementations.Tests/Library/MediaSourceManagerTests.cs b/tests/Jellyfin.Server.Implementations.Tests/Library/MediaSourceManagerTests.cs
index facdb2bc2e..c80f899498 100644
--- a/tests/Jellyfin.Server.Implementations.Tests/Library/MediaSourceManagerTests.cs
+++ b/tests/Jellyfin.Server.Implementations.Tests/Library/MediaSourceManagerTests.cs
@@ -1,4 +1,6 @@
 using System;
+using System.Collections.Generic;
+using System.Linq;
 using AutoFixture;
 using AutoFixture.AutoMoq;
 using Castle.Components.DictionaryAdapter;
@@ -7,6 +9,8 @@ using Emby.Server.Implementations.Library;
 using Jellyfin.Database.Implementations.Entities;
 using MediaBrowser.Controller.Entities;
 using MediaBrowser.Controller.Library;
+using MediaBrowser.Controller.LiveTv;
+using MediaBrowser.Controller.MediaSegments;
 using MediaBrowser.Model.Dto;
 using MediaBrowser.Model.Entities;
 using MediaBrowser.Model.Globalization;
@@ -144,5 +148,105 @@ namespace Jellyfin.Server.Implementations.Tests.Library
             _mediaSourceManager.SetDefaultAudioAndSubtitleStreamIndices(_item, mediaInfo, _user);
             Assert.Equal(expectedIndex, mediaInfo.DefaultAudioStreamIndex);
         }
+
+        [Fact]
+        public void GetStaticMediaSources_PrimaryQueried_DefaultsToMostRecentlyPlayedVersion()
+        {
+            var (primary, alt1, alt2) = SetupVersionGroup();
+            SetupUserDataBatch(new Dictionary<Guid, UserItemData>
+            {
+                [alt1.Id] = new UserItemData { Key = "alt1", PlaybackPositionTicks = 10, LastPlayedDate = new DateTime(2026, 1, 1, 0, 0, 0, DateTimeKind.Utc) },
+                [alt2.Id] = new UserItemData { Key = "alt2", PlaybackPositionTicks = 20, LastPlayedDate = new DateTime(2026, 1, 2, 0, 0, 0, DateTimeKind.Utc) }
+            });
+
+            var sources = _mediaSourceManager.GetStaticMediaSources(primary, false, _user);
+
+            // The most recently played version is the default source, so resuming plays the right file.
+            // Per-user positions live in each version's UserData, not on the source.
+            Assert.Equal(alt2.Id.ToString("N"), sources[0].Id);
+        }
+
+        [Fact]
+        public void GetStaticMediaSources_AlternateQueried_KeepsOwnSourceFirst()
+        {
+            var (primary, alt1, alt2) = SetupVersionGroup();
+            SetupUserDataBatch(new Dictionary<Guid, UserItemData>
+            {
+                [alt2.Id] = new UserItemData { Key = "alt2", PlaybackPositionTicks = 20, LastPlayedDate = new DateTime(2026, 1, 2, 0, 0, 0, DateTimeKind.Utc) }
+            });
+
+            var sources = _mediaSourceManager.GetStaticMediaSources(alt1, false, _user);
+
+            // An explicitly opened version keeps its own source first, even when a sibling was
+            // played more recently.
+            Assert.Equal(alt1.Id.ToString("N"), sources[0].Id);
+            Assert.Equal(3, sources.Count);
+        }
+
+        [Fact]
+        public void GetStaticMediaSources_NoProgress_KeepsQueriedItemFirst()
+        {
+            var (primary, _, _) = SetupVersionGroup();
+            SetupUserDataBatch([]);
+
+            var sources = _mediaSourceManager.GetStaticMediaSources(primary, false, _user);
+
+            Assert.Equal(primary.Id.ToString("N"), sources[0].Id);
+        }
+
+        [Fact]
+        public void GetStaticMediaSources_NoUser_DoesNotTouchUserData()
+        {
+            var (primary, _, _) = SetupVersionGroup();
+
+            var sources = _mediaSourceManager.GetStaticMediaSources(primary, false);
+
+            Assert.Equal(primary.Id.ToString("N"), sources[0].Id);
+            _mockUserDataManager.Verify(x => x.GetUserDataBatch(It.IsAny<IReadOnlyList<BaseItem>>(), It.IsAny<User>()), Times.Never);
+        }
+
+        private void SetupUserDataBatch(Dictionary<Guid, UserItemData> userData)
+        {
+            _mockUserDataManager
+                .Setup(x => x.GetUserDataBatch(It.IsAny<IReadOnlyList<BaseItem>>(), It.IsAny<User>()))
+                .Returns((IReadOnlyList<BaseItem> items, User _) => items
+                    .Where(i => userData.ContainsKey(i.Id))
+                    .ToDictionary(i => i.Id, i => userData[i.Id]));
+        }
+
+        private static (Video Primary, Video Alt1, Video Alt2) SetupVersionGroup()
+        {
+            var primary = new Video { Id = Guid.NewGuid(), Path = "/Movies/Movie/Movie.mkv" };
+            var alt1 = new Video { Id = Guid.NewGuid(), Path = "/Movies/Movie/Movie - 1080p.mkv", PrimaryVersionId = primary.Id };
+            var alt2 = new Video { Id = Guid.NewGuid(), Path = "/Movies/Movie/Movie - 4K.mkv", PrimaryVersionId = primary.Id };
+
+            // BaseItem.GetMediaSources runs against the static service locators.
+            var mediaSourceManager = new Mock<IMediaSourceManager>();
+            mediaSourceManager.Setup(x => x.GetPathProtocol(It.IsAny<string>())).Returns(MediaProtocol.File);
+            mediaSourceManager.Setup(x => x.GetMediaStreams(It.IsAny<Guid>())).Returns(new List<MediaStream>());
+            mediaSourceManager.Setup(x => x.GetMediaAttachments(It.IsAny<Guid>())).Returns(new List<MediaAttachment>());
+
+            var segmentManager = new Mock<IMediaSegmentManager>();
+            segmentManager.Setup(x => x.IsTypeSupported(It.IsAny<BaseItem>())).Returns(false);
+
+            var libraryManager = new Mock<ILibraryManager>();
+            libraryManager.Setup(x => x.GetLinkedAlternateVersions(It.IsAny<Video>())).Returns(Array.Empty<Video>());
+            libraryManager.Setup(x => x.GetLocalAlternateVersionIds(primary)).Returns(new[] { alt1.Id, alt2.Id });
+            libraryManager.Setup(x => x.GetLocalAlternateVersionIds(alt1)).Returns(Array.Empty<Guid>());
+            libraryManager.Setup(x => x.GetLocalAlternateVersionIds(alt2)).Returns(Array.Empty<Guid>());
+            libraryManager.Setup(x => x.GetItemById(primary.Id)).Returns(primary);
+            libraryManager.Setup(x => x.GetItemById(alt1.Id)).Returns(alt1);
+            libraryManager.Setup(x => x.GetItemById(alt2.Id)).Returns(alt2);
+
+            var recordingsManager = new Mock<IRecordingsManager>();
+            recordingsManager.Setup(x => x.GetActiveRecordingInfo(It.IsAny<string>())).Returns((ActiveRecordingInfo?)null);
+
+            BaseItem.MediaSegmentManager = segmentManager.Object;
+            BaseItem.MediaSourceManager = mediaSourceManager.Object;
+            BaseItem.LibraryManager = libraryManager.Object;
+            Video.RecordingsManager = recordingsManager.Object;
+
+            return (primary, alt1, alt2);
+        }
     }
 }
diff --git a/tests/Jellyfin.Server.Implementations.Tests/Library/PathExtensionsTests.cs b/tests/Jellyfin.Server.Implementations.Tests/Library/PathExtensionsTests.cs
index 650d67b195..e65bc1d31f 100644
--- a/tests/Jellyfin.Server.Implementations.Tests/Library/PathExtensionsTests.cs
+++ b/tests/Jellyfin.Server.Implementations.Tests/Library/PathExtensionsTests.cs
@@ -9,44 +9,105 @@ namespace Jellyfin.Server.Implementations.Tests.Library
     {
         [Theory]
         [InlineData("Superman: Red Son [imdbid=tt10985510]", "imdbid", "tt10985510")]
+        [InlineData("Superman: Red Son [imdb=tt10985510]", "imdbid", "tt10985510")]
         [InlineData("Superman: Red Son [imdbid-tt10985510]", "imdbid", "tt10985510")]
+        [InlineData("Superman: Red Son [imdb-tt10985510]", "imdbid", "tt10985510")]
         [InlineData("Superman: Red Son - tt10985510", "imdbid", "tt10985510")]
         [InlineData("Superman: Red Son {imdbid=tt10985510}", "imdbid", "tt10985510")]
+        [InlineData("Superman: Red Son {imdb=tt10985510}", "imdbid", "tt10985510")]
+        [InlineData("Superman: Red Son {imdbid-tt10985510}", "imdbid", "tt10985510")]
+        [InlineData("Superman: Red Son {imdb-tt10985510}", "imdbid", "tt10985510")]
+        [InlineData("Superman: Red Son (imdbid=tt10985510)", "imdbid", "tt10985510")]
+        [InlineData("Superman: Red Son (imdb=tt10985510)", "imdbid", "tt10985510")]
         [InlineData("Superman: Red Son (imdbid-tt10985510)", "imdbid", "tt10985510")]
+        [InlineData("Superman: Red Son (imdb-tt10985510)", "imdbid", "tt10985510")]
         [InlineData("Superman: Red Son", "imdbid", null)]
         [InlineData("Superman: Red Son [imdbid1=tt11111111][imdbid=tt10985510]", "imdbid", "tt10985510")]
+        [InlineData("Superman: Red Son [imdbid1=tt11111111][imdb=tt10985510]", "imdbid", "tt10985510")]
         [InlineData("Superman: Red Son {imdbid1=tt11111111}(imdbid=tt10985510)", "imdbid", "tt10985510")]
+        [InlineData("Superman: Red Son {imdbid1=tt11111111}(imdb=tt10985510)", "imdbid", "tt10985510")]
         [InlineData("Superman: Red Son (imdbid1-tt11111111)[imdbid=tt10985510]", "imdbid", "tt10985510")]
+        [InlineData("Superman: Red Son (imdbid1-tt11111111)[imdb=tt10985510]", "imdbid", "tt10985510")]
         [InlineData("Superman: Red Son [tmdbid=618355][imdbid=tt10985510]", "imdbid", "tt10985510")]
+        [InlineData("Superman: Red Son [tmdbid=618355][imdb=tt10985510]", "imdbid", "tt10985510")]
         [InlineData("Superman: Red Son [tmdbid-618355]{imdbid-tt10985510}", "imdbid", "tt10985510")]
+        [InlineData("Superman: Red Son [tmdbid-618355]{imdb-tt10985510}", "imdbid", "tt10985510")]
         [InlineData("Superman: Red Son (tmdbid-618355)[imdbid-tt10985510]", "tmdbid", "618355")]
+        [InlineData("Superman: Red Son (tmdbid-618355)[imdb-tt10985510]", "tmdbid", "618355")]
         [InlineData("Superman: Red Son [providera-id=1]", "providera-id", "1")]
         [InlineData("Superman: Red Son [providerb-id=2]", "providerb-id", "2")]
         [InlineData("Superman: Red Son [providera id=4]", "providera id", "4")]
         [InlineData("Superman: Red Son [providerb id=5]", "providerb id", "5")]
+        [InlineData("Superman: Red Son [provider=99][providerid=5]", "providerid", "5")]
         [InlineData("Superman: Red Son [tmdbid=3]", "tmdbid", "3")]
-        [InlineData("Superman: Red Son [tvdbid-6]", "tvdbid", "6")]
+        [InlineData("Superman: Red Son [tmdb=3]", "tmdbid", "3")]
+        [InlineData("Superman: Red Son [tmdbid-3]", "tmdbid", "3")]
+        [InlineData("Superman: Red Son [tmdb-3]", "tmdbid", "3")]
         [InlineData("Superman: Red Son {tmdbid=3}", "tmdbid", "3")]
+        [InlineData("Superman: Red Son {tmdb=3}", "tmdbid", "3")]
+        [InlineData("Superman: Red Son {tmdbid-3}", "tmdbid", "3")]
+        [InlineData("Superman: Red Son {tmdb-3}", "tmdbid", "3")]
+        [InlineData("Superman: Red Son (tmdbid=6)", "tmdbid", "6")]
+        [InlineData("Superman: Red Son (tmdb=6)", "tmdbid", "6")]
+        [InlineData("Superman: Red Son (tmdbid-6)", "tmdbid", "6")]
+        [InlineData("Superman: Red Son (tmdb-6)", "tmdbid", "6")]
+        [InlineData("Superman: Red Son [tvdbid=6]", "tvdbid", "6")]
+        [InlineData("Superman: Red Son [tvdb=6]", "tvdbid", "6")]
+        [InlineData("Superman: Red Son [tvdbid-6]", "tvdbid", "6")]
+        [InlineData("Superman: Red Son [tvdb-6]", "tvdbid", "6")]
+        [InlineData("Superman: Red Son {tvdbid=3}", "tvdbid", "3")]
+        [InlineData("Superman: Red Son {tvdb=3}", "tvdbid", "3")]
+        [InlineData("Superman: Red Son {tvdbid-3}", "tvdbid", "3")]
+        [InlineData("Superman: Red Son {tvdb-3}", "tvdbid", "3")]
+        [InlineData("Superman: Red Son (tvdbid=6)", "tvdbid", "6")]
+        [InlineData("Superman: Red Son (tvdb=6)", "tvdbid", "6")]
         [InlineData("Superman: Red Son (tvdbid-6)", "tvdbid", "6")]
+        [InlineData("Superman: Red Son (tvdb-6)", "tvdbid", "6")]
         [InlineData("[tmdbid=618355]", "tmdbid", "618355")]
+        [InlineData("[tmdb=618355]", "tmdbid", "618355")]
         [InlineData("{tmdbid=618355}", "tmdbid", "618355")]
+        [InlineData("{tmdb=618355}", "tmdbid", "618355")]
         [InlineData("(tmdbid=618355)", "tmdbid", "618355")]
+        [InlineData("(tmdb=618355)", "tmdbid", "618355")]
         [InlineData("[tmdbid-618355]", "tmdbid", "618355")]
+        [InlineData("[tmdb-618355]", "tmdbid", "618355")]
         [InlineData("{tmdbid-618355)", "tmdbid", null)]
+        [InlineData("{tmdb-618355)", "tmdbid", null)]
         [InlineData("[tmdbid-618355}", "tmdbid", null)]
+        [InlineData("[tmdb-618355}", "tmdbid", null)]
         [InlineData("tmdbid=111111][tmdbid=618355]", "tmdbid", "618355")]
+        [InlineData("tmdbid=111111][tmdb=618355]", "tmdbid", "618355")]
         [InlineData("[tmdbid=618355]tmdbid=111111]", "tmdbid", "618355")]
+        [InlineData("[tmdb=618355]tmdbid=111111]", "tmdbid", "618355")]
         [InlineData("tmdbid=618355]", "tmdbid", null)]
+        [InlineData("tmdb=618355]", "tmdbid", null)]
         [InlineData("[tmdbid=618355", "tmdbid", null)]
+        [InlineData("[tmdb=618355", "tmdbid", null)]
         [InlineData("tmdbid=618355", "tmdbid", null)]
+        [InlineData("tmdb=618355", "tmdbid", null)]
         [InlineData("tmdbid=", "tmdbid", null)]
+        [InlineData("tmdb=", "tmdbid", null)]
         [InlineData("tmdbid", "tmdbid", null)]
+        [InlineData("tmdb", "tmdbid", null)]
+        [InlineData("[tmdbid= ][tmdbid=223344]", "tmdbid", "223344")]
+        [InlineData("[tmdb= ][tmdb=223344]", "tmdbid", "223344")]
+        [InlineData("[tmdbid=  ][tmdb=223344]", "tmdbid", "223344")]
+        [InlineData("[tmdb=   ][tmdbid=223344]", "tmdbid", "223344")]
         [InlineData("[tmdbid=][imdbid=tt10985510]", "tmdbid", null)]
+        [InlineData("[tmdb=][imdbid=tt10985510]", "tmdbid", null)]
         [InlineData("[tmdbid-][imdbid-tt10985510]", "tmdbid", null)]
+        [InlineData("[tmdb-][imdbid-tt10985510]", "tmdbid", null)]
         [InlineData("Superman: Red Son [tmdbid-618355][tmdbid=1234567]", "tmdbid", "618355")]
+        [InlineData("Superman: Red Son [tmdb-618355][tmdbid=1234567]", "tmdbid", "618355")]
         [InlineData("{tmdbid=}{imdbid=tt10985510}", "tmdbid", null)]
+        [InlineData("{tmdb=}{imdbid=tt10985510}", "tmdbid", null)]
         [InlineData("(tmdbid-)(imdbid-tt10985510)", "tmdbid", null)]
+        [InlineData("(tmdb-)(imdbid-tt10985510)", "tmdbid", null)]
         [InlineData("Superman: Red Son {tmdbid-618355}{tmdbid=1234567}", "tmdbid", "618355")]
+        [InlineData("Superman: Red Son {tmdb-618355}{tmdbid=1234567}", "tmdbid", "618355")]
+        [InlineData("Superman: Red Son - tt10985510 [imdbid1=tt11]", "imdbid", "tt10985510")]
+        [InlineData("Superman: Red Son [tmdb=618355][tmdbid1=1]", "tmdbid", "618355")]
+        [InlineData("Superman: Red Son [tmdb=618355][tmdbid=12345]", "tmdbid", "618355")]
         public void GetAttributeValue_ValidArgs_Correct(string input, string attribute, string? expectedResult)
         {
             Assert.Equal(expectedResult, PathExtensions.GetAttributeValue(input, attribute));
diff --git a/tests/Jellyfin.Server.Implementations.Tests/Library/UserDataManagerTests.cs b/tests/Jellyfin.Server.Implementations.Tests/Library/UserDataManagerTests.cs
new file mode 100644
index 0000000000..ba3127bc08
--- /dev/null
+++ b/tests/Jellyfin.Server.Implementations.Tests/Library/UserDataManagerTests.cs
@@ -0,0 +1,216 @@
+using System;
+using System.Collections.Generic;
+using Emby.Server.Implementations.Library;
+using Jellyfin.Database.Implementations;
+using Jellyfin.Database.Implementations.Entities;
+using Jellyfin.Database.Implementations.Locking;
+using Jellyfin.Database.Providers.Sqlite;
+using MediaBrowser.Controller.Configuration;
+using MediaBrowser.Controller.Entities;
+using MediaBrowser.Model.Configuration;
+using Microsoft.Data.Sqlite;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging.Abstractions;
+using Moq;
+using Xunit;
+using AudioBook = MediaBrowser.Controller.Entities.AudioBook;
+
+namespace Jellyfin.Server.Implementations.Tests.Library;
+
+public sealed class UserDataManagerTests : IDisposable
+{
+    private readonly SqliteConnection _connection;
+    private readonly DbContextOptions<JellyfinDbContext> _dbOptions;
+    private readonly UserDataManager _userDataManager;
+    private readonly User _user;
+
+    public UserDataManagerTests()
+    {
+        _connection = new SqliteConnection("Data Source=:memory:");
+        _connection.Open();
+
+        _dbOptions = new DbContextOptionsBuilder<JellyfinDbContext>()
+            .UseSqlite(_connection)
+            .Options;
+
+        using (var ctx = CreateDbContext())
+        {
+            ctx.Database.EnsureCreated();
+        }
+
+        var factory = new Mock<IDbContextFactory<JellyfinDbContext>>();
+        factory.Setup(f => f.CreateDbContext()).Returns(CreateDbContext);
+
+        var config = new Mock<IServerConfigurationManager>();
+        config.SetupGet(c => c.Configuration).Returns(new ServerConfiguration());
+
+        _userDataManager = new UserDataManager(config.Object, factory.Object);
+        _user = new User("user", "auth-provider", "reset-provider")
+        {
+            Id = Guid.NewGuid()
+        };
+    }
+
+    public void Dispose()
+    {
+        _connection.Dispose();
+    }
+
+    private JellyfinDbContext CreateDbContext()
+    {
+        return new JellyfinDbContext(
+            _dbOptions,
+            NullLogger<JellyfinDbContext>.Instance,
+            new SqliteDatabaseProvider(null!, NullLogger<SqliteDatabaseProvider>.Instance),
+            new NoLockBehavior(NullLogger<NoLockBehavior>.Instance));
+    }
+
+    private AudioBook CreateAudioBook()
+    {
+        // GetUserDataKeys(): ["Author-Series-0001Book Title", "<item id N>"]
+        return new AudioBook
+        {
+            Id = Guid.NewGuid(),
+            Name = "Book Title",
+            Album = "Series",
+            AlbumArtists = new[] { "Author" },
+            IndexNumber = 1
+        };
+    }
+
+    private UserData CreateUserDataRow(AudioBook item, string key, long positionTicks)
+    {
+        return new UserData
+        {
+            ItemId = item.Id,
+            Item = null,
+            UserId = _user.Id,
+            User = null,
+            CustomDataKey = key,
+            PlaybackPositionTicks = positionTicks
+        };
+    }
+
+    [Fact]
+    public void GetUserData_RowsUnderCurrentAndRetiredKeys_PrefersCurrentKeyRow()
+    {
+        var item = CreateAudioBook();
+        var currentKey = item.GetUserDataKeys()[0];
+
+        // the retired-key row comes first to ensure selection is by key, not row order
+        item.UserData = new List<UserData>
+        {
+            CreateUserDataRow(item, "Author-Old Album-0001Old File Name", 111),
+            CreateUserDataRow(item, currentKey, 222)
+        };
+
+        var userData = _userDataManager.GetUserData(_user, item);
+
+        Assert.NotNull(userData);
+        Assert.Equal(currentKey, userData.Key);
+        Assert.Equal(222, userData.PlaybackPositionTicks);
+    }
+
+    [Fact]
+    public void GetUserData_NoPrimaryKeyRow_UsesNextCurrentKeyRow()
+    {
+        var item = CreateAudioBook();
+        var idKey = item.GetUserDataKeys()[1];
+
+        item.UserData = new List<UserData>
+        {
+            CreateUserDataRow(item, "Author-Old Album-0001Old File Name", 111),
+            CreateUserDataRow(item, idKey, 333)
+        };
+
+        var userData = _userDataManager.GetUserData(_user, item);
+
+        Assert.NotNull(userData);
+        Assert.Equal(idKey, userData.Key);
+        Assert.Equal(333, userData.PlaybackPositionTicks);
+    }
+
+    [Fact]
+    public void GetUserData_OnlyRetiredKeyRows_ReturnsRetiredKeyRow()
+    {
+        var item = CreateAudioBook();
+
+        item.UserData = new List<UserData>
+        {
+            CreateUserDataRow(item, "Author-Old Album-0001Old File Name", 111)
+        };
+
+        var userData = _userDataManager.GetUserData(_user, item);
+
+        Assert.NotNull(userData);
+        Assert.Equal(111, userData.PlaybackPositionTicks);
+    }
+
+    [Fact]
+    public void GetUserData_NoRows_ReturnsDefaultWithPrimaryKey()
+    {
+        var item = CreateAudioBook();
+        item.UserData = new List<UserData>();
+
+        var userData = _userDataManager.GetUserData(_user, item);
+
+        Assert.NotNull(userData);
+        Assert.Equal(item.GetUserDataKeys()[0], userData.Key);
+        Assert.Equal(0, userData.PlaybackPositionTicks);
+    }
+
+    [Fact]
+    public void GetUserData_RowsForOtherUsers_AreIgnored()
+    {
+        var item = CreateAudioBook();
+        var currentKey = item.GetUserDataKeys()[0];
+
+        var otherUserRow = CreateUserDataRow(item, currentKey, 999);
+        otherUserRow.UserId = Guid.NewGuid();
+
+        item.UserData = new List<UserData>
+        {
+            otherUserRow,
+            CreateUserDataRow(item, currentKey, 222)
+        };
+
+        var userData = _userDataManager.GetUserData(_user, item);
+
+        Assert.NotNull(userData);
+        Assert.Equal(222, userData.PlaybackPositionTicks);
+    }
+
+    [Fact]
+    public void GetUserDataBatch_DatabaseFallback_ResolvesRowsByKeyOrder()
+    {
+        // no preloaded navigation data, so the batch takes the database fallback
+        var fossilItem = CreateAudioBook();
+        var retiredItem = CreateAudioBook();
+
+        using (var ctx = CreateDbContext())
+        {
+            ctx.Users.Add(_user);
+            ctx.BaseItems.Add(new BaseItemEntity { Id = fossilItem.Id, Type = typeof(AudioBook).FullName! });
+            ctx.BaseItems.Add(new BaseItemEntity { Id = retiredItem.Id, Type = typeof(AudioBook).FullName! });
+
+            // the stale id-key row is inserted first so selection by row order would return it
+            ctx.UserData.AddRange(
+                CreateUserDataRow(fossilItem, fossilItem.GetUserDataKeys()[1], 111),
+                CreateUserDataRow(fossilItem, fossilItem.GetUserDataKeys()[0], 222),
+                CreateUserDataRow(retiredItem, "Author-Old Album-0001Old File Name", 333));
+            ctx.SaveChanges();
+        }
+
+        var result = _userDataManager.GetUserDataBatch([fossilItem, retiredItem], _user);
+
+        Assert.Equal(222, result[fossilItem.Id].PlaybackPositionTicks);
+        Assert.Equal(333, result[retiredItem.Id].PlaybackPositionTicks);
+    }
+
+    [Fact]
+    public void GetUserData_NullUser_ThrowsArgumentNullException()
+    {
+        var item = CreateAudioBook();
+        Assert.Throws<ArgumentNullException>(() => _userDataManager.GetUserData(null!, item));
+    }
+}
diff --git a/tests/Jellyfin.Server.Implementations.Tests/Localization/LocalizationManagerTests.cs b/tests/Jellyfin.Server.Implementations.Tests/Localization/LocalizationManagerTests.cs
index 3b8fe5ca60..2ed880ed9c 100644
--- a/tests/Jellyfin.Server.Implementations.Tests/Localization/LocalizationManagerTests.cs
+++ b/tests/Jellyfin.Server.Implementations.Tests/Localization/LocalizationManagerTests.cs
@@ -119,6 +119,40 @@ namespace Jellyfin.Server.Implementations.Tests.Localization
             Assert.Equal(code, culture.ThreeLetterISOLanguageName);
         }
 
+        [Theory]
+        [InlineData("ell", "Greek")] // Comma truncation
+        [InlineData("nld", "Dutch")] // Semicolon truncation
+        [InlineData("ron", "Romanian")] // Semicolon truncation, multiple
+        [InlineData("eng", "English")] // No truncation
+        [InlineData("zh-CN", "Chinese (Simplified)")] // No truncation, with parentheses
+        public async Task GetLanguageDisplayName_DelimitedName_ReturnsTruncatedName(string language, string expected)
+        {
+            var localizationManager = Setup(new ServerConfiguration
+            {
+                UICulture = "en-US"
+            });
+            await localizationManager.LoadAll();
+
+            var result = localizationManager.GetLanguageDisplayName(language);
+            Assert.Equal(expected, result);
+        }
+
+        [Theory]
+        [InlineData(null)]
+        [InlineData("")]
+        [InlineData("xyz")]
+        public async Task GetLanguageDisplayName_InvalidInput_ReturnsNull(string? language)
+        {
+            var localizationManager = Setup(new ServerConfiguration
+            {
+                UICulture = "en-US"
+            });
+            await localizationManager.LoadAll();
+
+            var result = localizationManager.GetLanguageDisplayName(language!);
+            Assert.Null(result);
+        }
+
         [Fact]
         public async Task GetParentalRatings_Default_Success()
         {
@@ -345,6 +379,20 @@ namespace Jellyfin.Server.Implementations.Tests.Localization
         }
 
         [Fact]
+        public void GetLocalizedString_WithBcp47NormalizationToUppercaseRegion_ReturnsTranslation()
+        {
+            var localizationManager = Setup(new ServerConfiguration
+            {
+                UICulture = "en-US"
+            });
+
+            // he-IL normalizes to the underscore resource he_IL. The resource lookup is case-sensitive,
+            // so the region casing has to be preserved or the file is not found and we fall back to en-US.
+            var translated = localizationManager.GetLocalizedString("Books", "he-IL");
+            Assert.Equal("ספרים", translated);
+        }
+
+        [Fact]
         public void GetServerLocalizedString_UsesServerCulture()
         {
             var localizationManager = Setup(new ServerConfiguration
diff --git a/tests/Jellyfin.Server.Implementations.Tests/SyncPlay/GroupTests.cs b/tests/Jellyfin.Server.Implementations.Tests/SyncPlay/GroupTests.cs
new file mode 100644
index 0000000000..bd9e680cd9
--- /dev/null
+++ b/tests/Jellyfin.Server.Implementations.Tests/SyncPlay/GroupTests.cs
@@ -0,0 +1,80 @@
+using System;
+using System.Collections.Generic;
+using Emby.Server.Implementations.SyncPlay;
+using Jellyfin.Database.Implementations.Entities;
+using MediaBrowser.Controller.Entities;
+using MediaBrowser.Controller.Library;
+using MediaBrowser.Controller.Session;
+using Microsoft.Extensions.Logging;
+using Moq;
+using Xunit;
+
+namespace Jellyfin.Server.Implementations.Tests.SyncPlay;
+
+public class GroupTests
+{
+    public GroupTests()
+    {
+        var mockLogger = new Mock<ILogger<Emby.Server.Implementations.SyncPlay.Group>>();
+        MockLoggerFactory = new Mock<ILoggerFactory>();
+        MockLoggerFactory.Setup(x => x.CreateLogger(It.IsAny<string>())).Returns(mockLogger.Object);
+
+        MockUserManager = new Mock<IUserManager>();
+        MockSessionManager = new Mock<ISessionManager>();
+        MockLibraryManager = new Mock<ILibraryManager>();
+        MockItem = new Mock<BaseItem>();
+        MockItem.Setup(i => i.IsVisibleStandalone(It.IsAny<User>())).Returns(true);
+    }
+
+    private Mock<ILoggerFactory> MockLoggerFactory { get; }
+
+    private Mock<IUserManager> MockUserManager { get; }
+
+    private Mock<ISessionManager> MockSessionManager { get; }
+
+    private Mock<ILibraryManager> MockLibraryManager { get; }
+
+    private Mock<BaseItem> MockItem { get; }
+
+    [Fact]
+    public void HasAccessToPlayQueue_ReturnsTrue_WhenItemsAreVisible()
+    {
+        MockLibraryManager.Setup(m => m.GetItemById(It.IsAny<Guid>())).Returns(MockItem.Object);
+
+        var group = new Emby.Server.Implementations.SyncPlay.Group(MockLoggerFactory.Object, MockUserManager.Object, MockSessionManager.Object, MockLibraryManager.Object);
+        var itemId = Guid.NewGuid();
+        var playlist = new List<Guid> { itemId };
+        group.PlayQueue.Reset();
+        group.PlayQueue.SetPlaylist(playlist);
+
+        Assert.Single(group.PlayQueue.GetPlaylist());
+        Assert.Equal(itemId, group.PlayQueue.GetPlaylist()[0].ItemId);
+
+        var user = new User("test-user", "auth-provider", "pwdreset-provider");
+        var result = group.HasAccessToPlayQueue(user);
+
+        Assert.True(result);
+    }
+
+    [Fact]
+    public void HasAccessToPlayQueue_ReturnsFalse_WhenLibraryReturnsNullForItem()
+    {
+        MockLibraryManager.Setup(m => m.GetItemById(It.IsAny<Guid>())).Returns((BaseItem?)null);
+
+        Assert.Null(MockLibraryManager.Object.GetItemById(Guid.NewGuid()));
+
+        var group = new Emby.Server.Implementations.SyncPlay.Group(MockLoggerFactory.Object, MockUserManager.Object, MockSessionManager.Object, MockLibraryManager.Object);
+        var itemId = Guid.NewGuid();
+        var playlist = new List<Guid> { itemId };
+        group.PlayQueue.Reset();
+        group.PlayQueue.SetPlaylist(playlist);
+
+        Assert.Single(group.PlayQueue.GetPlaylist());
+        Assert.Equal(itemId, group.PlayQueue.GetPlaylist()[0].ItemId);
+
+        var user = new User("test-user", "auth-provider", "pwdreset-provider");
+        var result = group.HasAccessToPlayQueue(user);
+
+        Assert.False(result);
+    }
+}
diff --git a/tests/Jellyfin.Server.Implementations.Tests/SyncPlay/PlayQueueManagerTests.cs b/tests/Jellyfin.Server.Implementations.Tests/SyncPlay/PlayQueueManagerTests.cs
new file mode 100644
index 0000000000..32685556b2
--- /dev/null
+++ b/tests/Jellyfin.Server.Implementations.Tests/SyncPlay/PlayQueueManagerTests.cs
@@ -0,0 +1,156 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using MediaBrowser.Controller.SyncPlay.Queue;
+using MediaBrowser.Model.SyncPlay;
+using Xunit;
+
+namespace Jellyfin.Server.Implementations.Tests.SyncPlay;
+
+public class PlayQueueManagerTests
+{
+    private static PlayQueueManager CreateQueue(int itemCount)
+    {
+        var items = Enumerable.Range(0, itemCount).Select(_ => Guid.NewGuid()).ToList();
+        var queue = new PlayQueueManager();
+        queue.SetPlaylist(items);
+        return queue;
+    }
+
+    [Fact]
+    public void RemoveFromPlaylist_PlayingItemAndPrecedingItemRemoved_PicksPreviousItem()
+    {
+        var queue = CreateQueue(5);
+        queue.SetPlayingItemByIndex(3);
+
+        var playlist = queue.GetPlaylist();
+        var expectedItemId = playlist[2].ItemId;
+        var toRemove = new List<Guid> { playlist[0].PlaylistItemId, playlist[3].PlaylistItemId };
+        var playingItemRemoved = queue.RemoveFromPlaylist(toRemove);
+
+        Assert.True(playingItemRemoved);
+        Assert.Equal(3, queue.GetPlaylist().Count);
+        Assert.Equal(1, queue.PlayingItemIndex);
+        Assert.Equal(expectedItemId, queue.GetPlayingItemId());
+    }
+
+    [Fact]
+    public void RemoveFromPlaylist_PlayingItemAndAllPrecedingItemsRemoved_PicksFirstRemainingItem()
+    {
+        var queue = CreateQueue(3);
+        queue.SetPlayingItemByIndex(2);
+
+        var playlist = queue.GetPlaylist();
+        var expectedItemId = playlist[1].ItemId;
+        var toRemove = new List<Guid> { playlist[0].PlaylistItemId, playlist[2].PlaylistItemId };
+        var playingItemRemoved = queue.RemoveFromPlaylist(toRemove);
+
+        Assert.True(playingItemRemoved);
+        Assert.Single(queue.GetPlaylist());
+        Assert.Equal(0, queue.PlayingItemIndex);
+        Assert.Equal(expectedItemId, queue.GetPlayingItemId());
+    }
+
+    [Fact]
+    public void RemoveFromPlaylist_AllItemsRemoved_ResetsPlayingItem()
+    {
+        var queue = CreateQueue(2);
+        queue.SetPlayingItemByIndex(1);
+
+        var toRemove = queue.GetPlaylist().Select(item => item.PlaylistItemId).ToList();
+        var playingItemRemoved = queue.RemoveFromPlaylist(toRemove);
+
+        Assert.True(playingItemRemoved);
+        Assert.Empty(queue.GetPlaylist());
+        Assert.False(queue.IsItemPlaying());
+        Assert.Equal(Guid.Empty, queue.GetPlayingItemPlaylistId());
+    }
+
+    [Fact]
+    public void RemoveFromPlaylist_ShuffleMode_PicksPreviousItem()
+    {
+        var queue = CreateQueue(5);
+        queue.SetShuffleMode(GroupShuffleMode.Shuffle);
+        queue.SetPlayingItemByIndex(3);
+
+        var playlist = queue.GetPlaylist();
+        var expectedItemId = playlist[2].ItemId;
+        var toRemove = new List<Guid> { playlist[0].PlaylistItemId, playlist[3].PlaylistItemId };
+        var playingItemRemoved = queue.RemoveFromPlaylist(toRemove);
+
+        Assert.True(playingItemRemoved);
+        Assert.Equal(3, queue.GetPlaylist().Count);
+        Assert.Equal(1, queue.PlayingItemIndex);
+        Assert.Equal(expectedItemId, queue.GetPlayingItemId());
+    }
+
+    [Fact]
+    public void RemoveFromPlaylist_PlayingItemNotRemoved_RestoresPlayingItem()
+    {
+        var queue = CreateQueue(3);
+        queue.SetPlayingItemByIndex(2);
+
+        var playlist = queue.GetPlaylist();
+        var expectedItemId = playlist[2].ItemId;
+        var toRemove = new List<Guid> { playlist[0].PlaylistItemId };
+        var playingItemRemoved = queue.RemoveFromPlaylist(toRemove);
+
+        Assert.False(playingItemRemoved);
+        Assert.Equal(1, queue.PlayingItemIndex);
+        Assert.Equal(expectedItemId, queue.GetPlayingItemId());
+    }
+
+    [Theory]
+    [InlineData(GroupRepeatMode.RepeatNone)]
+    [InlineData(GroupRepeatMode.RepeatOne)]
+    [InlineData(GroupRepeatMode.RepeatAll)]
+    public void Next_EmptyPlaylist_ReturnsFalse(GroupRepeatMode repeatMode)
+    {
+        var queue = new PlayQueueManager();
+        queue.SetRepeatMode(repeatMode);
+
+        Assert.False(queue.Next());
+        Assert.False(queue.IsItemPlaying());
+        Assert.Equal(Guid.Empty, queue.GetPlayingItemPlaylistId());
+    }
+
+    [Theory]
+    [InlineData(GroupRepeatMode.RepeatNone)]
+    [InlineData(GroupRepeatMode.RepeatOne)]
+    [InlineData(GroupRepeatMode.RepeatAll)]
+    public void Previous_EmptyPlaylist_ReturnsFalse(GroupRepeatMode repeatMode)
+    {
+        var queue = new PlayQueueManager();
+        queue.SetRepeatMode(repeatMode);
+
+        Assert.False(queue.Previous());
+        Assert.False(queue.IsItemPlaying());
+        Assert.Equal(Guid.Empty, queue.GetPlayingItemPlaylistId());
+    }
+
+    [Theory]
+    [InlineData(-1)]
+    [InlineData(2)]
+    [InlineData(3)]
+    public void SetPlayingItemByIndex_OutOfBounds_ResetsPlayingItem(int playlistIndex)
+    {
+        var queue = CreateQueue(2);
+
+        queue.SetPlayingItemByIndex(playlistIndex);
+
+        Assert.False(queue.IsItemPlaying());
+        Assert.Equal(Guid.Empty, queue.GetPlayingItemPlaylistId());
+    }
+
+    [Fact]
+    public void SetPlayingItemByIndex_InBounds_SetsPlayingItem()
+    {
+        var queue = CreateQueue(2);
+        var expectedItemId = queue.GetPlaylist()[1].ItemId;
+
+        queue.SetPlayingItemByIndex(1);
+
+        Assert.True(queue.IsItemPlaying());
+        Assert.Equal(expectedItemId, queue.GetPlayingItemId());
+    }
+}
diff --git a/tests/Jellyfin.Server.Implementations.Tests/Updates/InstallationManagerTests.cs b/tests/Jellyfin.Server.Implementations.Tests/Updates/InstallationManagerTests.cs
index 92e10c9f92..4a10b2f607 100644
--- a/tests/Jellyfin.Server.Implementations.Tests/Updates/InstallationManagerTests.cs
+++ b/tests/Jellyfin.Server.Implementations.Tests/Updates/InstallationManagerTests.cs
@@ -109,5 +109,29 @@ namespace Jellyfin.Server.Implementations.Tests.Updates
             var ex = await Record.ExceptionAsync(() => _installationManager.InstallPackage(packageInfo, CancellationToken.None));
             Assert.Null(ex);
         }
+
+        [Theory]
+        [InlineData("../evil")]
+        [InlineData("..\\evil")]
+        [InlineData("../../escape_attempt")]
+        [InlineData("..")]
+        [InlineData(".")]
+        [InlineData("")]
+        [InlineData("   ")]
+        [InlineData("foo/bar")]
+        [InlineData("foo\\bar")]
+        [InlineData("/absolute")]
+        [InlineData("foo\0bar")]
+        public async Task InstallPackage_InvalidName_ThrowsInvalidDataException(string name)
+        {
+            var packageInfo = new InstallationInfo()
+            {
+                Name = name,
+                SourceUrl = "https://repo.jellyfin.org/releases/plugin/empty/empty.zip",
+                Checksum = "11b5b2f1a9ebc4f66d6ef19018543361"
+            };
+
+            await Assert.ThrowsAsync<InvalidDataException>(() => _installationManager.InstallPackage(packageInfo, CancellationToken.None));
+        }
     }
 }
diff --git a/tests/Jellyfin.Server.Implementations.Tests/Users/UserManagerProfileImageTests.cs b/tests/Jellyfin.Server.Implementations.Tests/Users/UserManagerProfileImageTests.cs
new file mode 100644
index 0000000000..cb714a4014
--- /dev/null
+++ b/tests/Jellyfin.Server.Implementations.Tests/Users/UserManagerProfileImageTests.cs
@@ -0,0 +1,142 @@
+using System;
+using System.IO;
+using System.Threading;
+using System.Threading.Tasks;
+using Jellyfin.Database.Implementations;
+using Jellyfin.Database.Implementations.Entities;
+using Jellyfin.Database.Implementations.Locking;
+using Jellyfin.Database.Providers.Sqlite;
+using Jellyfin.Server.Implementations.Users;
+using MediaBrowser.Common;
+using MediaBrowser.Common.Net;
+using MediaBrowser.Controller;
+using MediaBrowser.Controller.Authentication;
+using MediaBrowser.Controller.Configuration;
+using MediaBrowser.Controller.Drawing;
+using MediaBrowser.Controller.Events;
+using MediaBrowser.Controller.Library;
+using MediaBrowser.Model.Cryptography;
+using Microsoft.Data.Sqlite;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging.Abstractions;
+using Moq;
+using Xunit;
+
+namespace Jellyfin.Server.Implementations.Tests.Users
+{
+    public sealed class UserManagerProfileImageTests : IDisposable
+    {
+        private readonly SqliteConnection _connection;
+        private readonly DbContextOptions<JellyfinDbContext> _dbOptions;
+        private readonly UserManager _userManager;
+
+        public UserManagerProfileImageTests()
+        {
+            _connection = new SqliteConnection("Data Source=:memory:");
+            _connection.Open();
+
+            _dbOptions = new DbContextOptionsBuilder<JellyfinDbContext>()
+                .UseSqlite(_connection)
+                .Options;
+
+            // Create the schema
+            using var ctx = CreateDbContext();
+            ctx.Database.EnsureCreated();
+
+            var factory = new Mock<IDbContextFactory<JellyfinDbContext>>();
+            factory.Setup(f => f.CreateDbContext()).Returns(CreateDbContext);
+            factory.Setup(f => f.CreateDbContextAsync(It.IsAny<CancellationToken>()))
+                .ReturnsAsync(CreateDbContext);
+
+            var cryptoProvider = new Mock<ICryptoProvider>();
+            var configManager = new Mock<IServerConfigurationManager>();
+            var appPaths = new Mock<IServerApplicationPaths>();
+            appPaths.Setup(x => x.ProgramDataPath).Returns(Path.GetTempPath());
+            configManager.Setup(x => x.ApplicationPaths).Returns(appPaths.Object);
+
+            var appHost = new Mock<IApplicationHost>();
+
+            var defaultAuthProvider = new DefaultAuthenticationProvider(
+                NullLogger<DefaultAuthenticationProvider>.Instance,
+                cryptoProvider.Object);
+            var invalidAuthProvider = new InvalidAuthProvider();
+            var defaultPasswordResetProvider = new DefaultPasswordResetProvider(
+                configManager.Object,
+                appHost.Object);
+
+            _userManager = new UserManager(
+                factory.Object,
+                new NoopEventManager(),
+                new Mock<INetworkManager>().Object,
+                appHost.Object,
+                new Mock<IImageProcessor>().Object,
+                NullLogger<UserManager>.Instance,
+                configManager.Object,
+                new IPasswordResetProvider[] { defaultPasswordResetProvider },
+                new IAuthenticationProvider[] { defaultAuthProvider, invalidAuthProvider });
+        }
+
+        public void Dispose()
+        {
+            _userManager.Dispose();
+            _connection.Dispose();
+        }
+
+        private JellyfinDbContext CreateDbContext()
+        {
+            return new JellyfinDbContext(
+                _dbOptions,
+                NullLogger<JellyfinDbContext>.Instance,
+                new SqliteDatabaseProvider(null!, NullLogger<SqliteDatabaseProvider>.Instance),
+                new NoLockBehavior(NullLogger<NoLockBehavior>.Instance));
+        }
+
+        [Fact]
+        public async Task ClearProfileImageAsync_WhenInMemoryImageHasTemporaryKey_RemovesPersistedImage()
+        {
+            var user = await _userManager.CreateUserAsync("profileimageuser");
+
+            // Assign a profile image the same way the image endpoint does and persist it.
+            // UpdateUserAsync creates the persisted ImageInfo on a separately loaded db entity,
+            // so the in-memory instance below is never assigned the database generated key.
+            user.ProfileImage = new ImageInfo(Path.Combine(Path.GetTempPath(), "profile.png"));
+            await _userManager.UpdateUserAsync(user);
+
+            // Precondition reproducing the bug: the in-memory image still carries the default,
+            // never-persisted (temporary) key, while a real image row exists in the database.
+            Assert.Equal(0, user.ProfileImage.Id);
+            Assert.NotNull(_userManager.GetUserById(user.Id)!.ProfileImage);
+
+            // This used to throw InvalidOperationException:
+            // "The property 'ImageInfo.Id' has a temporary value while attempting to change the entity's state to 'Deleted'."
+            var exception = await Record.ExceptionAsync(() => _userManager.ClearProfileImageAsync(user));
+
+            Assert.Null(exception);
+            Assert.Null(user.ProfileImage);
+            Assert.Null(_userManager.GetUserById(user.Id)!.ProfileImage);
+        }
+
+        [Fact]
+        public async Task ClearProfileImageAsync_WhenNoProfileImage_DoesNothing()
+        {
+            var user = await _userManager.CreateUserAsync("noprofileimageuser");
+
+            var exception = await Record.ExceptionAsync(() => _userManager.ClearProfileImageAsync(user));
+
+            Assert.Null(exception);
+            Assert.Null(user.ProfileImage);
+        }
+
+        private sealed class NoopEventManager : IEventManager
+        {
+            public void Publish<T>(T eventArgs)
+                where T : EventArgs
+            {
+            }
+
+            public Task PublishAsync<T>(T eventArgs)
+                where T : EventArgs
+                => Task.CompletedTask;
+        }
+    }
+}
diff --git a/tests/Jellyfin.Server.Implementations.Tests/Users/UserManagerTests.cs b/tests/Jellyfin.Server.Implementations.Tests/Users/UserManagerTests.cs
index 4cea53bd3d..2bf1d1d05b 100644
--- a/tests/Jellyfin.Server.Implementations.Tests/Users/UserManagerTests.cs
+++ b/tests/Jellyfin.Server.Implementations.Tests/Users/UserManagerTests.cs
@@ -27,6 +27,8 @@ namespace Jellyfin.Server.Implementations.Tests.Users
         [InlineData(" thishasaspaceatthestart")]
         [InlineData(" thishasaspaceatbothends ")]
         [InlineData(" this has a space at both ends and inbetween ")]
+        [InlineData(".")]
+        [InlineData("..")]
         public void ThrowIfInvalidUsername_WhenInvalidUsername_ThrowsArgumentException(string username)
         {
             Assert.Throws<ArgumentException>(() => UserManager.ThrowIfInvalidUsername(username));