fix(api): normalise the Next Up cutoff to UTC

The query-string cutoff binds as DateTimeKind.Unspecified, which Npgsql
refuses to write to timestamp with time zone, so /Shows/NextUp 500s.

Jellyfin.Api/Controllers/TvShowsController.cs

@@ -108,7 +108,7 @@ public class TvShowsController : BaseJellyfinApiController
                 StartIndex = startIndex,
                 User = user,
                 EnableTotalRecordCount = enableTotalRecordCount,
-                NextUpDateCutoff = nextUpDateCutoff ?? DateTime.MinValue,
+                NextUpDateCutoff = nextUpDateCutoff?.ToUniversalTime() ?? DateTime.SpecifyKind(DateTime.MinValue, DateTimeKind.Utc),
                 EnableResumable = enableResumable,
                 EnableRewatching = enableRewatching
             },

MediaBrowser.Model/Querying/NextUpQuery.cs

@@ -12,7 +12,7 @@ public class NextUpQuery
     {
         EnableImageTypes = Array.Empty<ImageType>();
         EnableTotalRecordCount = true;
-        NextUpDateCutoff = DateTime.MinValue;
+        NextUpDateCutoff = DateTime.SpecifyKind(DateTime.MinValue, DateTimeKind.Utc);
         EnableResumable = false;
         EnableRewatching = false;
     }
@@ -56,7 +56,7 @@ public class NextUpQuery
     public bool EnableTotalRecordCount { get; set; }
 
     /// <summary>
-    /// Gets or sets a value indicating the oldest date for a show to appear in Next Up.
+    /// Gets or sets a value indicating the oldest date, in UTC, for a show to appear in Next Up.
     /// </summary>
     public DateTime NextUpDateCutoff { get; set; }
 

tests/Jellyfin.Server.Tests/Item/PostgreSqlNextUpServiceTests.cs

@@ -0,0 +1,234 @@
+using System;
+using System.Collections.Generic;
+using System.Security.Claims;
+using System.Threading;
+using System.Threading.Tasks;
+using Emby.Server.Implementations.Data;
+using Jellyfin.Api.Constants;
+using Jellyfin.Api.Controllers;
+using Jellyfin.Database.Implementations;
+using Jellyfin.Database.Implementations.DbConfiguration;
+using Jellyfin.Database.Implementations.Entities;
+using Jellyfin.Database.Implementations.Locking;
+using Jellyfin.Database.Providers.PostgreSQL;
+using Jellyfin.Server.Implementations.Item;
+using Jellyfin.Server.Tests.Migrations;
+using MediaBrowser.Controller.Dto;
+using MediaBrowser.Controller.Entities;
+using MediaBrowser.Controller.Library;
+using MediaBrowser.Controller.Persistence;
+using MediaBrowser.Controller.TV;
+using MediaBrowser.Model.Querying;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging.Abstractions;
+using Moq;
+using Npgsql;
+using Xunit;
+using BaseItemKind = Jellyfin.Data.Enums.BaseItemKind;
+using User = Jellyfin.Database.Implementations.Entities.User;
+
+namespace Jellyfin.Server.Tests.Item;
+
+/// <summary>
+/// Drives the Next Up cutoff from the controller into a real PostgreSQL. The model binder hands a
+/// query-string date over as <see cref="DateTimeKind.Unspecified"/>, and Npgsql refuses to write anything
+/// but <see cref="DateTimeKind.Utc"/> to <c>timestamp with time zone</c>; SQLite takes every kind, so an
+/// unnormalised cutoff only ever fails here.
+/// </summary>
+[Trait("Category", "RequiresDocker")]
+public sealed class PostgreSqlNextUpServiceTests : IAsyncLifetime
+{
+    private static readonly Guid _libraryId = Guid.Parse("aaaaaaaa-0000-0000-0000-000000000001");
+    private static readonly Guid _otherLibraryId = Guid.Parse("aaaaaaaa-0000-0000-0000-000000000002");
+    private static readonly Guid _userId = Guid.Parse("bbbbbbbb-0000-0000-0000-000000000001");
+
+    private static readonly Guid _recentWatchedId = Guid.Parse("cccccccc-0000-0000-0000-000000000001");
+    private static readonly Guid _recentOlderId = Guid.Parse("cccccccc-0000-0000-0000-000000000002");
+    private static readonly Guid _staleWatchedId = Guid.Parse("cccccccc-0000-0000-0000-000000000003");
+    private static readonly Guid _unwatchedId = Guid.Parse("cccccccc-0000-0000-0000-000000000004");
+    private static readonly Guid _foreignLibraryId = Guid.Parse("cccccccc-0000-0000-0000-000000000005");
+
+    private static readonly DateTime _recentPlayedAt = new DateTime(2026, 3, 1, 12, 0, 0, DateTimeKind.Utc);
+    private static readonly DateTime _stalePlayedAt = new DateTime(2020, 1, 1, 12, 0, 0, DateTimeKind.Utc);
+
+    private readonly ItemTypeLookup _itemTypeLookup = new();
+    private readonly User _user = new User("next-up", "auth", "reset") { Id = _userId };
+
+    private PostgreSqlTestServer _server = null!;
+    private NpgsqlDataSource _dataSource = null!;
+    private NextUpService _service = null!;
+
+    public async ValueTask InitializeAsync()
+    {
+        _server = await PostgreSqlTestServer.StartAsync().ConfigureAwait(false);
+        var connectionString = await _server.CreateDatabaseAsync("next_up_service", TestContext.Current.CancellationToken).ConfigureAwait(false);
+        _dataSource = new NpgsqlDataSourceBuilder(connectionString).Build();
+
+        var context = CreateDbContext();
+        await using (context.ConfigureAwait(false))
+        {
+            await context.Database.EnsureCreatedAsync(TestContext.Current.CancellationToken).ConfigureAwait(false);
+        }
+
+        var factory = new Mock<IDbContextFactory<JellyfinDbContext>>();
+        factory.Setup(f => f.CreateDbContext()).Returns(CreateDbContext);
+        factory.Setup(f => f.CreateDbContextAsync(It.IsAny<CancellationToken>())).ReturnsAsync(CreateDbContext);
+
+        _service = new NextUpService(factory.Object, _itemTypeLookup, new Mock<IItemQueryHelpers>().Object);
+
+        await SeedAsync().ConfigureAwait(false);
+    }
+
+    public async ValueTask DisposeAsync()
+    {
+        await _dataSource.DisposeAsync().ConfigureAwait(false);
+        await _server.DisposeAsync().ConfigureAwait(false);
+    }
+
+    /// <summary>
+    /// A cutoff on the query string, which the model binder leaves unspecified.
+    /// </summary>
+    [Fact]
+    public void GetNextUpSeriesKeys_WithSuppliedCutoff_DropsSeriesPlayedBeforeIt()
+    {
+        var cutoff = RunController(new DateTime(2025, 1, 1, 0, 0, 0, DateTimeKind.Unspecified)).NextUpDateCutoff;
+
+        var keys = _service.GetNextUpSeriesKeys(CreateFilter(), cutoff);
+
+        Assert.Equal(new[] { "series-recent" }, keys);
+    }
+
+    /// <summary>
+    /// The home-screen row, where the client sends no cutoff and the query default stands in.
+    /// </summary>
+    [Fact]
+    public void GetNextUpSeriesKeys_WithoutSuppliedCutoff_ReturnsWatchedSeriesNewestFirst()
+    {
+        var cutoff = RunController(null).NextUpDateCutoff;
+
+        var keys = _service.GetNextUpSeriesKeys(CreateFilter(), cutoff);
+
+        Assert.Equal(new[] { "series-recent", "series-stale" }, keys);
+    }
+
+    /// <summary>
+    /// Calls <c>GET /Shows/NextUp</c> and hands back the query it built for the series lookup.
+    /// </summary>
+    private NextUpQuery RunController(DateTime? nextUpDateCutoff)
+    {
+        var userManager = new Mock<IUserManager>();
+        userManager.Setup(m => m.GetUserById(_userId)).Returns(_user);
+
+        var dtoService = new Mock<IDtoService>();
+        dtoService.Setup(s => s.GetBaseItemDtos(
+                It.IsAny<IReadOnlyList<BaseItem>>(),
+                It.IsAny<DtoOptions>(),
+                It.IsAny<User>(),
+                It.IsAny<BaseItem>(),
+                It.IsAny<bool>()))
+            .Returns([]);
+
+        NextUpQuery? captured = null;
+        var tvSeriesManager = new Mock<ITVSeriesManager>();
+        tvSeriesManager.Setup(m => m.GetNextUp(It.IsAny<NextUpQuery>(), It.IsAny<DtoOptions>()))
+            .Callback<NextUpQuery, DtoOptions>((query, _) => captured = query)
+            .Returns(new QueryResult<BaseItem>());
+
+        var controller = new TvShowsController(
+            userManager.Object,
+            new Mock<ILibraryManager>().Object,
+            dtoService.Object,
+            tvSeriesManager.Object)
+        {
+            ControllerContext = new ControllerContext
+            {
+                HttpContext = new DefaultHttpContext
+                {
+                    User = new ClaimsPrincipal(new ClaimsIdentity([new Claim(InternalClaimTypes.UserId, _userId.ToString("D"))], "Test"))
+                }
+            }
+        };
+
+        controller.GetNextUp(null, null, null, [], null, null, null, null, [], null, nextUpDateCutoff);
+
+        return captured!;
+    }
+
+    private InternalItemsQuery CreateFilter()
+    {
+        return new InternalItemsQuery(_user) { TopParentIds = [_libraryId] };
+    }
+
+    private JellyfinDbContext CreateDbContext()
+    {
+        var optionsBuilder = new DbContextOptionsBuilder<JellyfinDbContext>();
+        var provider = new PostgreSqlDatabaseProvider(_dataSource);
+        provider.Initialise(optionsBuilder, new DatabaseConfigurationOptions { DatabaseType = "PostgreSQL" });
+        return new JellyfinDbContext(
+            optionsBuilder.Options,
+            NullLogger<JellyfinDbContext>.Instance,
+            provider,
+            new NoLockBehavior(NullLogger<NoLockBehavior>.Instance));
+    }
+
+    private async Task SeedAsync()
+    {
+        var context = CreateDbContext();
+        await using (context.ConfigureAwait(false))
+        {
+            context.Users.Add(_user);
+
+            // The newest play of a series decides its place, so the older episode must not pull it down.
+            var recentWatched = AddEpisode(context, _recentWatchedId, "series-recent", _libraryId);
+            AddUserData(context, recentWatched, _recentPlayedAt);
+            var recentOlder = AddEpisode(context, _recentOlderId, "series-recent", _libraryId);
+            AddUserData(context, recentOlder, _stalePlayedAt);
+
+            var staleWatched = AddEpisode(context, _staleWatchedId, "series-stale", _libraryId);
+            AddUserData(context, staleWatched, _stalePlayedAt);
+
+            // Never played, and played but outside the requested libraries: both stay out.
+            AddEpisode(context, _unwatchedId, "series-unwatched", _libraryId);
+            var foreign = AddEpisode(context, _foreignLibraryId, "series-foreign", _otherLibraryId);
+            AddUserData(context, foreign, _recentPlayedAt);
+
+            await context.SaveChangesAsync(TestContext.Current.CancellationToken).ConfigureAwait(false);
+        }
+    }
+
+    private BaseItemEntity AddEpisode(JellyfinDbContext context, Guid id, string seriesKey, Guid topParentId)
+    {
+        var episode = new BaseItemEntity
+        {
+            Id = id,
+            Type = _itemTypeLookup.BaseItemKindNames[BaseItemKind.Episode],
+            Name = seriesKey + "-" + id.ToString("N"),
+            SeriesPresentationUniqueKey = seriesKey,
+            PresentationUniqueKey = id.ToString("N"),
+            TopParentId = topParentId,
+            MediaType = "Video",
+            IsFolder = false,
+            IsVirtualItem = false
+        };
+
+        context.BaseItems.Add(episode);
+        return episode;
+    }
+
+    private void AddUserData(JellyfinDbContext context, BaseItemEntity item, DateTime lastPlayedDate)
+    {
+        context.UserData.Add(new UserData
+        {
+            CustomDataKey = item.Id.ToString("N"),
+            ItemId = item.Id,
+            Item = item,
+            UserId = _userId,
+            User = _user,
+            LastPlayedDate = lastPlayedDate,
+            Played = true,
+            PlayCount = 1
+        });
+    }
+}