Fix external API response handling (#684)

code/backend/Cleanuparr.Api/Json/CleanuparrJsonConfiguration.cs

@@ -1,6 +1,7 @@
 using System.Text.Json;
 using System.Text.Json.Serialization;
 using System.Text.Json.Serialization.Metadata;
+using Cleanuparr.Infrastructure.Json;
 
 namespace Cleanuparr.Api.Json;
 
@@ -23,31 +24,7 @@ public static class CleanuparrJsonConfiguration
     public static void ConfigureApiInbound(JsonSerializerOptions options)
     {
         ConfigureApi(options);
-        options.TypeInfoResolver = options.TypeInfoResolver!.WithAddedModifier(IgnoreNullForNonNullable);
-    }
-
-    private static void IgnoreNullForNonNullable(JsonTypeInfo typeInfo)
-    {
-        if (typeInfo.Kind != JsonTypeInfoKind.Object)
-        {
-            return;
-        }
-
-        foreach (JsonPropertyInfo property in typeInfo.Properties)
-        {
-            if (property.Set is null || property.IsSetNullable)
-            {
-                continue;
-            }
-
-            Action<object, object?> originalSet = property.Set;
-            property.Set = (obj, value) =>
-            {
-                if (value is not null)
-                {
-                    originalSet(obj, value);
-                }
-            };
-        }
+        options.TypeInfoResolver = options.TypeInfoResolver!
+            .WithAddedModifier(CleanuparrJsonOptions.IgnoreNullForNonNullable);
     }
 }

code/backend/Cleanuparr.Domain/Entities/Arr/Queue/Image.cs

@@ -1,8 +1,17 @@
-namespace Cleanuparr.Domain.Entities.Arr.Queue;
+namespace Cleanuparr.Domain.Entities.Arr.Queue;
 
+/// <summary>
+/// An image of a series or a movie in Sonarr, Radarr or Whisparr.
+/// </summary>
 public record Image
 {
-    public required string CoverType { get; init; }
-    
-    public required Uri RemoteUrl { get; init; }
-}
+    /// <summary>
+    /// The type of the image, for example "poster" or "screenshot".
+    /// </summary>
+    public string CoverType { get; init; } = string.Empty;
+
+    /// <summary>
+    /// The address of the image on the server of the metadata provider.
+    /// </summary>
+    public Uri? RemoteUrl { get; init; }
+}

code/backend/Cleanuparr.Domain/Entities/Arr/Queue/LidarrImage.cs

@@ -1,8 +1,17 @@
-namespace Cleanuparr.Domain.Entities.Arr.Queue;
+namespace Cleanuparr.Domain.Entities.Arr.Queue;
 
+/// <summary>
+/// An image of an album in Lidarr.
+/// </summary>
 public record LidarrImage
 {
-    public required string CoverType { get; init; }
-    
-    public required Uri Url { get; init; }
-}
+    /// <summary>
+    /// The type of the image, for example "cover".
+    /// </summary>
+    public string CoverType { get; init; } = string.Empty;
+
+    /// <summary>
+    /// The address of the image.
+    /// </summary>
+    public Uri? Url { get; init; }
+}

code/backend/Cleanuparr.Domain/Entities/Arr/Queue/QueueListResponse.cs

@@ -1,7 +1,17 @@
-namespace Cleanuparr.Domain.Entities.Arr.Queue;
+namespace Cleanuparr.Domain.Entities.Arr.Queue;
 
+/// <summary>
+/// One page of the queue of an *arr application.
+/// </summary>
 public record QueueListResponse
 {
-    public required int TotalRecords { get; init; }
-    public required IReadOnlyList<QueueRecord> Records { get; init; }
-}
+    /// <summary>
+    /// The number of items in the queue, on this page and on the other pages.
+    /// </summary>
+    public int TotalRecords { get; init; }
+
+    /// <summary>
+    /// The items on this page.
+    /// </summary>
+    public IReadOnlyList<QueueRecord> Records { get; init; } = [];
+}

code/backend/Cleanuparr.Domain/Entities/Arr/Queue/QueueRecord.cs

@@ -1,42 +1,126 @@
 namespace Cleanuparr.Domain.Entities.Arr.Queue;
 
+/// <summary>
+/// One item in the queue of an *arr application.
+/// The *arr applications share this type, and each one sets only its own fields.
+/// </summary>
 public sealed record QueueRecord
 {
     // Sonarr and Whisparr v2
+    /// <summary>
+    /// The ID of the series.
+    /// </summary>
     public long SeriesId { get; init; }
+
+    /// <summary>
+    /// The ID of the episode.
+    /// </summary>
     public long EpisodeId { get; init; }
+
+    /// <summary>
+    /// The number of the season.
+    /// </summary>
     public long SeasonNumber { get; init; }
-    
+
+    /// <summary>
+    /// The data about the series.
+    /// </summary>
     public QueueSeries? Series { get; init; }
-    
+
     // Radarr and Whisparr v3
+    /// <summary>
+    /// The ID of the movie.
+    /// </summary>
     public long MovieId { get; init; }
-    
+
+    /// <summary>
+    /// The data about the movie.
+    /// </summary>
     public QueueMovie? Movie { get; init; }
-    
+
     // Lidarr
+    /// <summary>
+    /// The ID of the artist.
+    /// </summary>
     public long ArtistId { get; init; }
-    
+
+    /// <summary>
+    /// The ID of the album.
+    /// </summary>
     public long AlbumId { get; init; }
-    
+
+    /// <summary>
+    /// The data about the album.
+    /// </summary>
     public QueueAlbum? Album { get; init; }
-    
+
     // Readarr
+    /// <summary>
+    /// The ID of the author.
+    /// </summary>
     public long AuthorId { get; init; }
-    
+
+    /// <summary>
+    /// The ID of the book.
+    /// </summary>
     public long BookId { get; init; }
-    
+
+    /// <summary>
+    /// The data about the book.
+    /// </summary>
     public QueueBook? Book { get; init; }
-    
+
     // common
-    public required string Title { get; init; }
-    public string Status { get; init; }
-    public string TrackedDownloadStatus { get; init; }
-    public string TrackedDownloadState { get; init; }
+    /// <summary>
+    /// The name of the release.
+    /// </summary>
+    public string Title { get; init; } = string.Empty;
+
+    /// <summary>
+    /// The status of the queue item, for example "downloading" or "delay".
+    /// </summary>
+    public string Status { get; init; } = string.Empty;
+
+    /// <summary>
+    /// The status of the tracked download, for example "warning".
+    /// A pending release does not have a tracked download, and the value is then empty.
+    /// </summary>
+    public string TrackedDownloadStatus { get; init; } = string.Empty;
+
+    /// <summary>
+    /// The state of the tracked download, for example "importBlocked".
+    /// A pending release does not have a tracked download, and the value is then empty.
+    /// </summary>
+    public string TrackedDownloadState { get; init; } = string.Empty;
+
+    /// <summary>
+    /// The messages that tell more about the status of the queue item.
+    /// </summary>
     public List<TrackedDownloadStatusMessage>? StatusMessages { get; init; }
-    public required string DownloadId { get; init; }
+
+    /// <summary>
+    /// The hash that the download client uses for the item.
+    /// A pending release is not in a download client, and the value is then empty.
+    /// </summary>
+    public string DownloadId { get; init; } = string.Empty;
+
+    /// <summary>
+    /// The name of the download client that has the item.
+    /// </summary>
     public string? DownloadClient { get; init; }
-    public required string Protocol { get; init; }
-    public required long Id { get; init; }
+
+    /// <summary>
+    /// The protocol of the release, for example "torrent" or "usenet".
+    /// </summary>
+    public string Protocol { get; init; } = string.Empty;
+
+    /// <summary>
+    /// The ID of the queue item.
+    /// </summary>
+    public long Id { get; init; }
+
+    /// <summary>
+    /// The number of bytes that the download client must still get.
+    /// </summary>
     public long SizeLeft { get; init; }
-}
+}

code/backend/Cleanuparr.Domain/Entities/Arr/Queue/ReadarrImage.cs

@@ -1,8 +1,17 @@
-namespace Cleanuparr.Domain.Entities.Arr.Queue;
+namespace Cleanuparr.Domain.Entities.Arr.Queue;
 
+/// <summary>
+/// An image of a book in Readarr.
+/// </summary>
 public sealed record ReadarrImage
 {
-    public required string CoverType { get; init; }
-    
-    public required Uri Url { get; init; }
-}
+    /// <summary>
+    /// The type of the image, for example "cover".
+    /// </summary>
+    public string CoverType { get; init; } = string.Empty;
+
+    /// <summary>
+    /// The address of the image.
+    /// </summary>
+    public Uri? Url { get; init; }
+}

code/backend/Cleanuparr.Domain/Entities/Arr/Tag.cs

@@ -1,8 +1,17 @@
 namespace Cleanuparr.Domain.Entities.Arr;
 
+/// <summary>
+/// A tag of an *arr application.
+/// </summary>
 public sealed record Tag
 {
-    public required long Id { get; init; }
-    
-    public required string Label { get; init; }
-}
+    /// <summary>
+    /// The ID of the tag.
+    /// </summary>
+    public long Id { get; init; }
+
+    /// <summary>
+    /// The name of the tag.
+    /// </summary>
+    public string Label { get; init; } = string.Empty;
+}

code/backend/Cleanuparr.Domain/Entities/Deluge/Response/DelugeContents.cs

@@ -2,11 +2,21 @@
 
 namespace Cleanuparr.Domain.Entities.Deluge.Response;
 
+/// <summary>
+/// The root of the file tree of a torrent in Deluge.
+/// </summary>
 public sealed record DelugeContents
 {
+    /// <summary>
+    /// The child nodes of the root.
+    /// </summary>
     [JsonPropertyName("contents")]
     public Dictionary<string, DelugeFileOrDirectory>? Contents { get; set; }
 
+    /// <summary>
+    /// The type of the root.
+    /// The value is always "dir".
+    /// </summary>
     [JsonPropertyName("type")]
-    public string Type { get; set; } // Always "dir" for the root
+    public string Type { get; set; } = string.Empty;
 }

code/backend/Cleanuparr.Domain/Entities/Deluge/Response/DelugeError.cs

@@ -2,11 +2,20 @@
 
 namespace Cleanuparr.Domain.Entities.Deluge.Response;
 
+/// <summary>
+/// The error of a response from Deluge.
+/// </summary>
 public sealed record DelugeError
 {
+    /// <summary>
+    /// The text of the error.
+    /// </summary>
     [JsonPropertyName("message")]
-    public String Message { get; set; }
+    public string Message { get; set; } = string.Empty;
 
+    /// <summary>
+    /// The code of the error.
+    /// </summary>
     [JsonPropertyName("code")]
     public int Code { get; set; }
 }

code/backend/Cleanuparr.Domain/Entities/Deluge/Response/DelugeFileOrDirectory.cs

@@ -1,33 +1,68 @@
-using System.Text.Json.Serialization;
+using System.Text.Json.Serialization;
 
 namespace Cleanuparr.Domain.Entities.Deluge.Response;
 
+/// <summary>
+/// One node in the file tree of a torrent in Deluge.
+/// A node is a file or a directory, and the value of <see cref="Type"/> tells which one it is.
+/// Deluge sends the file fields only on a file node.
+/// </summary>
 public class DelugeFileOrDirectory
 {
+    /// <summary>
+    /// The type of the node.
+    /// The value is "file" or "dir".
+    /// </summary>
     [JsonPropertyName("type")]
-    public string Type { get; set; } // "file" or "dir"
+    public string Type { get; set; } = string.Empty;
 
+    /// <summary>
+    /// The child nodes of a directory node.
+    /// </summary>
     [JsonPropertyName("contents")]
-    public Dictionary<string, DelugeFileOrDirectory>? Contents { get; set; } // Recursive property for directories
+    public Dictionary<string, DelugeFileOrDirectory>? Contents { get; set; }
 
+    /// <summary>
+    /// The position of the file in the list of files of the torrent.
+    /// Deluge sends this field only on a file node, and the value is 0 on a directory node.
+    /// </summary>
     [JsonPropertyName("index")]
-    public required int Index { get; set; }
+    public int Index { get; set; }
 
+    /// <summary>
+    /// The path of the node in the torrent.
+    /// </summary>
     [JsonPropertyName("path")]
-    public string Path { get; set; }
+    public string Path { get; set; } = string.Empty;
 
+    /// <summary>
+    /// The size of the node in bytes.
+    /// </summary>
     [JsonPropertyName("size")]
     public int? Size { get; set; }
 
+    /// <summary>
+    /// The offset of the file in the data of the torrent.
+    /// </summary>
     [JsonPropertyName("offset")]
     public int? Offset { get; set; }
 
+    /// <summary>
+    /// The part of the node that Deluge has, as a value from 0 to 100.
+    /// </summary>
     [JsonPropertyName("progress")]
     public double? Progress { get; set; }
 
+    /// <summary>
+    /// The download priority of the node.
+    /// A value of 0 tells Deluge to skip the file.
+    /// </summary>
     [JsonPropertyName("priority")]
-    public required int Priority { get; set; }
+    public int Priority { get; set; }
 
+    /// <summary>
+    /// The progress of each file below a directory node.
+    /// </summary>
     [JsonPropertyName("progresses")]
-    public List<double> Progresses { get; set; }
-}
+    public List<double> Progresses { get; set; } = [];
+}

code/backend/Cleanuparr.Domain/Entities/Deluge/Response/DownloadStatus.cs

@@ -1,49 +1,104 @@
-using Cleanuparr.Domain.Enums;
+using Cleanuparr.Domain.Enums;
 using System.Text.Json.Serialization;
 
 namespace Cleanuparr.Domain.Entities.Deluge.Response;
 
+/// <summary>
+/// The status of a torrent in Deluge.
+/// Deluge sends only the fields that the request asks for.
+/// </summary>
 public sealed record DownloadStatus
 {
+    /// <summary>
+    /// The hash of the torrent.
+    /// </summary>
     public string? Hash { get; init; }
 
+    /// <summary>
+    /// The state of the torrent, for example <see cref="DelugeState.Seeding"/>.
+    /// </summary>
     public DelugeState State { get; init; }
 
+    /// <summary>
+    /// The name of the torrent.
+    /// </summary>
     public string? Name { get; init; }
 
+    /// <summary>
+    /// The number of seconds that the download needs to finish.
+    /// </summary>
     public ulong Eta { get; init; }
 
+    /// <summary>
+    /// The download speed in bytes each second.
+    /// </summary>
     [JsonPropertyName("download_payload_rate")]
     public long DownloadSpeed { get; init; }
 
+    /// <summary>
+    /// True if the tracker of the torrent is private.
+    /// </summary>
     public bool Private { get; init; }
 
+    /// <summary>
+    /// The size of the torrent in bytes.
+    /// </summary>
     [JsonPropertyName("total_size")]
     public long Size { get; init; }
 
+    /// <summary>
+    /// The number of bytes that Deluge has.
+    /// </summary>
     [JsonPropertyName("total_done")]
     public long TotalDone { get; init; }
 
+    /// <summary>
+    /// True if the download is complete.
+    /// </summary>
     [JsonPropertyName("is_finished")]
     public bool IsFinished { get; init; }
 
+    /// <summary>
+    /// The label of the torrent.
+    /// </summary>
     public string? Label { get; set; }
 
+    /// <summary>
+    /// The number of seconds that the torrent has been in the seed state.
+    /// </summary>
     [JsonPropertyName("seeding_time")]
     public long SeedingTime { get; init; }
 
+    /// <summary>
+    /// The number of bytes that Deluge sent, divided by the number of bytes that Deluge got.
+    /// </summary>
     public float Ratio { get; init; }
 
+    /// <summary>
+    /// The number of seeds that the tracker reports.
+    /// </summary>
     [JsonPropertyName("total_seeds")]
     public int TotalSeeds { get; init; }
 
-    public required IReadOnlyList<Tracker> Trackers { get; init; }
+    /// <summary>
+    /// The trackers of the torrent.
+    /// </summary>
+    public IReadOnlyList<Tracker> Trackers { get; init; } = [];
 
+    /// <summary>
+    /// The directory that holds the data of the torrent.
+    /// </summary>
     [JsonPropertyName("download_location")]
-    public required string DownloadLocation { get; init; }
+    public string DownloadLocation { get; init; } = string.Empty;
 }
 
+/// <summary>
+/// A tracker of a torrent in Deluge.
+/// </summary>
 public sealed record Tracker
 {
-    public required string Url { get; init; }
+    /// <summary>
+    /// The address of the tracker.
+    /// </summary>
+    public string Url { get; init; } = string.Empty;
 }

code/backend/Cleanuparr.Domain/Entities/Radarr/Movie.cs

@@ -1,8 +1,17 @@
-namespace Cleanuparr.Domain.Entities.Radarr;
+namespace Cleanuparr.Domain.Entities.Radarr;
 
+/// <summary>
+/// A movie in Radarr or Whisparr v3.
+/// </summary>
 public sealed record Movie
 {
-    public required long Id { get; init; }
-    
-    public required string Title { get; init; }
-}
+    /// <summary>
+    /// The ID of the movie.
+    /// </summary>
+    public long Id { get; init; }
+
+    /// <summary>
+    /// The name of the movie.
+    /// </summary>
+    public string Title { get; init; } = string.Empty;
+}

code/backend/Cleanuparr.Domain/Entities/Readarr/Book.cs

@@ -1,12 +1,27 @@
 namespace Cleanuparr.Domain.Entities.Readarr;
 
+/// <summary>
+/// A book in Readarr.
+/// </summary>
 public sealed record Book
 {
-    public required long Id { get; init; }
-    
-    public required string Title { get; init; }
-    
+    /// <summary>
+    /// The ID of the book.
+    /// </summary>
+    public long Id { get; init; }
+
+    /// <summary>
+    /// The name of the book.
+    /// </summary>
+    public string Title { get; init; } = string.Empty;
+
+    /// <summary>
+    /// The ID of the author of the book.
+    /// </summary>
     public long AuthorId { get; set; }
-    
+
+    /// <summary>
+    /// The data about the author of the book.
+    /// </summary>
     public Author Author { get; set; } = new();
-} 
+}

code/backend/Cleanuparr.Domain/Entities/Sonarr/Series.cs

@@ -1,8 +1,17 @@
-namespace Cleanuparr.Domain.Entities.Sonarr;
+namespace Cleanuparr.Domain.Entities.Sonarr;
 
+/// <summary>
+/// A series in Sonarr or Whisparr v2.
+/// </summary>
 public sealed record Series
 {
-    public required long Id { get; init; }
-            
-    public required string Title { get; init; }
-}
+    /// <summary>
+    /// The ID of the series.
+    /// </summary>
+    public long Id { get; init; }
+
+    /// <summary>
+    /// The name of the series.
+    /// </summary>
+    public string Title { get; init; } = string.Empty;
+}

code/backend/Cleanuparr.Infrastructure.Tests/Features/DownloadClient/Deluge/DelugeClientSerializationTests.cs

@@ -109,4 +109,47 @@ public class DelugeClientSerializationTests
         status.State.ShouldBe(DelugeState.Seeding);
         status.IsFinished.ShouldBeTrue();
     }
+
+    [Fact]
+    public async Task GetTorrentFiles_WithNestedDirectory_DeserializesWithoutIndex()
+    {
+        const string response = """
+            {
+                "id": 1,
+                "result": {
+                    "type": "dir",
+                    "contents": {
+                        "Some.Release": {
+                            "type": "dir",
+                            "priority": 1,
+                            "progress": 1.0,
+                            "progresses": [1.0],
+                            "size": 200,
+                            "path": "Some.Release",
+                            "contents": {
+                                "video.mkv": {
+                                    "type": "file",
+                                    "index": 0,
+                                    "offset": 0,
+                                    "path": "Some.Release/video.mkv",
+                                    "priority": 1,
+                                    "progress": 1.0,
+                                    "size": 200
+                                }
+                            }
+                        }
+                    }
+                },
+                "error": null
+            }
+            """;
+        (DelugeClient client, _) = CreateClient(response);
+
+        DelugeContents? contents = await client.GetTorrentFiles("abc");
+
+        contents.ShouldNotBeNull();
+        DelugeFileOrDirectory directory = contents.Contents!["Some.Release"];
+        directory.Type.ShouldBe("dir");
+        directory.Contents!["video.mkv"].Index.ShouldBe(0);
+    }
 }

code/backend/Cleanuparr.Infrastructure.Tests/Features/Jobs/SeekerTests.cs

@@ -359,6 +359,67 @@ public class SeekerTests : IDisposable
         instanceConfig.LastProcessedAt.ShouldNotBeNull();
     }
 
+    [Fact]
+    public async Task ExecuteAsync_ActiveDownloadLimit_IgnoresRecordsWithoutDownloadId()
+    {
+        // Arrange — pending releases have no download id and are not in a download client
+        var config = await _fixture.DataContext.SeekerConfigs.FirstAsync();
+        config.SearchEnabled = true;
+        config.ProactiveSearchEnabled = true;
+        await _fixture.DataContext.SaveChangesAsync();
+        await _fixture.EventsContext.SaveChangesAsync();
+
+        var radarrInstance = TestDataContextFactory.AddRadarrInstance(_fixture.DataContext);
+
+        _fixture.DataContext.SeekerInstanceConfigs.Add(new SeekerInstanceConfig
+        {
+            ArrInstanceId = radarrInstance.Id,
+            ArrInstance = radarrInstance,
+            Enabled = true,
+            ActiveDownloadLimit = 1
+        });
+        await _fixture.DataContext.SaveChangesAsync();
+        await _fixture.EventsContext.SaveChangesAsync();
+
+        var mockArrClient = Substitute.For<IArrClient>();
+
+        QueueRecord[] pendingReleases =
+        [
+            new() { Id = 1, Title = "Pending 1", Protocol = "torrent", SizeLeft = 1000, MovieId = 10, Status = "delay" },
+            new() { Id = 2, Title = "Pending 2", Protocol = "torrent", SizeLeft = 2000, MovieId = 20, Status = "delay" }
+        ];
+        _fixture.ArrQueueIterator
+            .Iterate(mockArrClient, Arg.Any<ArrInstance>(), Arg.Any<Func<IReadOnlyList<QueueRecord>, Task>>())
+            .Returns(ci => ci.ArgAt<Func<IReadOnlyList<QueueRecord>, Task>>(2)(pendingReleases));
+
+        _radarrClient
+            .StreamAllMoviesAsync(radarrInstance, Arg.Any<CancellationToken>())
+            .Returns(
+            ToAsyncEnumerable<SearchableMovie>([
+                new SearchableMovie { Id = 1, Title = "Movie 1", Status = "released", Monitored = true, Tags = [] }
+            ]));
+
+        mockArrClient
+            .SearchItemAsync(radarrInstance, Arg.Any<SearchItem>())
+            .Returns(100L);
+
+        _fixture.ArrClientFactory
+            .GetClient(InstanceType.Radarr, Arg.Any<float>())
+            .Returns(mockArrClient);
+
+        var sut = CreateSut();
+
+        // Act
+        await sut.ExecuteAsync();
+
+        // Assert — the limit of 1 must not be tripped by records that have no download id
+        await mockArrClient.Received(1)
+            .SearchItemAsync(radarrInstance, Arg.Any<SearchItem>());
+
+        var instanceConfig = await _fixture.DataContext.SeekerInstanceConfigs.FirstAsync();
+        instanceConfig.LastProcessedAt.ShouldNotBeNull();
+    }
+
     [Fact]
     public async Task ExecuteAsync_Radarr_ExcludesMoviesAlreadyInQueue()
     {

code/backend/Cleanuparr.Infrastructure.Tests/Json/ExternalApiReadTests.cs

@@ -0,0 +1,113 @@
+using System.Text.Json;
+using Cleanuparr.Domain.Entities.Arr;
+using Cleanuparr.Domain.Entities.Arr.Queue;
+using Cleanuparr.Infrastructure.Json;
+using Shouldly;
+using Xunit;
+
+namespace Cleanuparr.Infrastructure.Tests.Json;
+
+public class ExternalApiReadTests
+{
+    [Fact]
+    public void QueueRecord_WithoutDownloadId_Deserializes()
+    {
+        const string payload = """
+        {
+            "totalRecords": 1,
+            "records": [
+                {
+                    "id": 42,
+                    "seriesId": 7,
+                    "title": "Some Release",
+                    "status": "delay",
+                    "protocol": "torrent"
+                }
+            ]
+        }
+        """;
+
+        QueueListResponse result = JsonSerializer.Deserialize<QueueListResponse>(payload, CleanuparrJsonOptions.ExternalApiRead)!;
+
+        result.TotalRecords.ShouldBe(1);
+        result.Records.Count.ShouldBe(1);
+        result.Records[0].Id.ShouldBe(42);
+        result.Records[0].DownloadId.ShouldBeEmpty();
+    }
+
+    [Fact]
+    public void QueueRecord_WithExplicitNulls_FallsBackToDefaults()
+    {
+        const string payload = """
+        {
+            "totalRecords": 1,
+            "records": [{ "id": 1, "title": "T", "downloadId": null, "protocol": null, "trackedDownloadState": null }]
+        }
+        """;
+
+        QueueListResponse result = JsonSerializer.Deserialize<QueueListResponse>(payload, CleanuparrJsonOptions.ExternalApiRead)!;
+
+        result.Records[0].DownloadId.ShouldBeEmpty();
+        result.Records[0].Protocol.ShouldBeEmpty();
+        result.Records[0].TrackedDownloadState.ShouldBeEmpty();
+    }
+
+    [Fact]
+    public void QueueRecord_WithExplicitNullOnNullableProperty_StaysNull()
+    {
+        const string payload = """
+        {
+            "totalRecords": 1,
+            "records": [{ "id": 1, "title": "T", "downloadId": "ABC", "downloadClient": null }]
+        }
+        """;
+
+        QueueListResponse result = JsonSerializer.Deserialize<QueueListResponse>(payload, CleanuparrJsonOptions.ExternalApiRead)!;
+
+        result.Records[0].DownloadClient.ShouldBeNull();
+    }
+
+    [Fact]
+    public void Tag_WithoutLabel_UsesEmptyDefault()
+    {
+        List<Tag> result = JsonSerializer.Deserialize<List<Tag>>("""[{"id": 3}]""", CleanuparrJsonOptions.ExternalApiRead)!;
+
+        result[0].Id.ShouldBe(3);
+        result[0].Label.ShouldBeEmpty();
+    }
+
+    [Fact]
+    public void QueueRecord_WithAllProperties_StillDeserializes()
+    {
+        const string payload = """
+        {
+            "totalRecords": 1,
+            "records": [{ "id": 1, "title": "T", "downloadId": "ABC", "protocol": "torrent", "sizeleft": 100 }]
+        }
+        """;
+
+        QueueListResponse result = JsonSerializer.Deserialize<QueueListResponse>(payload, CleanuparrJsonOptions.ExternalApiRead)!;
+
+        result.Records[0].DownloadId.ShouldBe("ABC");
+        result.Records[0].Title.ShouldBe("T");
+        result.Records[0].SizeLeft.ShouldBe(100);
+    }
+
+    [Fact]
+    public void EmptyQueueResponse_Deserializes()
+    {
+        QueueListResponse result = JsonSerializer.Deserialize<QueueListResponse>("{}", CleanuparrJsonOptions.ExternalApiRead)!;
+
+        result.TotalRecords.ShouldBe(0);
+        result.Records.ShouldBeEmpty();
+    }
+
+    [Fact]
+    public void PositionalRecord_WithMissingConstructorParameter_Deserializes()
+    {
+        ArrCommandStatus result = JsonSerializer.Deserialize<ArrCommandStatus>("""{"id": 5}""", CleanuparrJsonOptions.ExternalApiRead)!;
+
+        result.Id.ShouldBe(5);
+        result.Status.ShouldBeNull();
+    }
+}

code/backend/Cleanuparr.Infrastructure/Features/Arr/JsonStreamReader.cs

@@ -1,5 +1,6 @@
 using System.Runtime.CompilerServices;
 using System.Text.Json;
+using Cleanuparr.Infrastructure.Json;
 
 namespace Cleanuparr.Infrastructure.Features.Arr;
 
@@ -8,14 +9,6 @@ namespace Cleanuparr.Infrastructure.Features.Arr;
 /// </summary>
 internal static class JsonStreamReader
 {
-    private static readonly JsonSerializerOptions Options = new()
-    {
-        PropertyNameCaseInsensitive = true,
-        NumberHandling = System.Text.Json.Serialization.JsonNumberHandling.AllowReadingFromString,
-        AllowTrailingCommas = true,
-        ReadCommentHandling = JsonCommentHandling.Skip,
-    };
-
     /// <summary>
     /// Streams items out of a top-level JSON array.
     /// </summary>
@@ -23,7 +16,7 @@ internal static class JsonStreamReader
         Stream stream,
         [EnumeratorCancellation] CancellationToken cancellationToken = default)
     {
-        await foreach (T? item in JsonSerializer.DeserializeAsyncEnumerable<T>(stream, Options, cancellationToken))
+        await foreach (T? item in JsonSerializer.DeserializeAsyncEnumerable<T>(stream, CleanuparrJsonOptions.ExternalApiRead, cancellationToken))
         {
             if (item is not null)
             {

code/backend/Cleanuparr.Infrastructure/Features/Jobs/Seeker.cs

@@ -284,7 +284,7 @@ public sealed class Seeker : IHandler
         if (instanceConfig.ActiveDownloadLimit > 0)
         {
             int activeDownloads = queueRecords
-                .Where(r => r.SizeLeft > 0)
+                .Where(r => r.SizeLeft > 0 && !string.IsNullOrEmpty(r.DownloadId))
                 .Select(r => r.DownloadId)
                 .Distinct()
                 .Count();

code/backend/Cleanuparr.Infrastructure/Json/CleanuparrJsonOptions.cs

@@ -1,25 +1,45 @@
 using System.Text.Encodings.Web;
 using System.Text.Json;
 using System.Text.Json.Serialization;
+using System.Text.Json.Serialization.Metadata;
 
 namespace Cleanuparr.Infrastructure.Json;
 
+/// <summary>
+/// The options that the application uses for JSON.
+/// </summary>
 public static class CleanuparrJsonOptions
 {
+    /// <summary>
+    /// The options to read a response from an external API.
+    /// These options do not make a property necessary, because an external API can omit a field.
+    /// A field that is absent or null gets the default value of the property.
+    /// </summary>
     public static readonly JsonSerializerOptions ExternalApiRead = new()
     {
         PropertyNameCaseInsensitive = true,
         NumberHandling = JsonNumberHandling.AllowReadingFromString,
         AllowTrailingCommas = true,
         ReadCommentHandling = JsonCommentHandling.Skip,
+        RespectRequiredConstructorParameters = false,
+        TypeInfoResolver = new DefaultJsonTypeInfoResolver
+        {
+            Modifiers = { IgnoreRequiredProperties, IgnoreNullForNonNullable },
+        },
     };
 
+    /// <summary>
+    /// The options to write a request to an external API.
+    /// </summary>
     public static readonly JsonSerializerOptions Outbound = new()
     {
         DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
         Encoder = JavaScriptEncoder.UnsafeRelaxedJsonEscaping,
     };
 
+    /// <summary>
+    /// The options to write a payload for a notification provider.
+    /// </summary>
     public static readonly JsonSerializerOptions Notification = new()
     {
         PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
@@ -27,9 +47,54 @@ public static class CleanuparrJsonOptions
         Encoder = JavaScriptEncoder.UnsafeRelaxedJsonEscaping,
     };
 
+    /// <summary>
+    /// The options to write a payload for a notification provider that needs the null fields.
+    /// </summary>
     public static readonly JsonSerializerOptions NotificationIncludeNulls = new()
     {
         PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
         Encoder = JavaScriptEncoder.UnsafeRelaxedJsonEscaping,
     };
+
+    private static void IgnoreRequiredProperties(JsonTypeInfo typeInfo)
+    {
+        if (typeInfo.Kind is not JsonTypeInfoKind.Object)
+        {
+            return;
+        }
+
+        foreach (JsonPropertyInfo property in typeInfo.Properties)
+        {
+            property.IsRequired = false;
+        }
+    }
+
+    /// <summary>
+    /// Keeps the default value of a property that is not nullable if the JSON field is null.
+    /// </summary>
+    /// <param name="typeInfo">The metadata of the type to change.</param>
+    public static void IgnoreNullForNonNullable(JsonTypeInfo typeInfo)
+    {
+        if (typeInfo.Kind is not JsonTypeInfoKind.Object)
+        {
+            return;
+        }
+
+        foreach (JsonPropertyInfo property in typeInfo.Properties)
+        {
+            if (property.Set is null || property.IsSetNullable)
+            {
+                continue;
+            }
+
+            Action<object, object?> originalSet = property.Set;
+            property.Set = (obj, value) =>
+            {
+                if (value is not null)
+                {
+                    originalSet(obj, value);
+                }
+            };
+        }
+    }
 }

code/backend/Cleanuparr.Persistence/Models/Configuration/Seeker/SeekerInstanceConfig.cs

@@ -54,6 +54,7 @@ public sealed record SeekerInstanceConfig
     /// <summary>
     /// Skip proactive search cycles when the number of actively downloading items
     /// (SizeLeft > 0) in the arr queue is at or above this threshold. 0 = disabled.
+    /// The count includes only the items that a download client has.
     /// </summary>
     public int ActiveDownloadLimit { get; set; } = 3;