Fix ArgumentException on NZB titles containing quote characters

listenarr.infrastructure/Downloads/Submission/GenericUsenetSourceResolver.cs

@@ -48,7 +48,15 @@ public async Task<PreparedDownloadSubmission> ResolveAsync(
             candidate.SourceDescriptor.FileName ?? $"{SanitizeFileName(candidate.Title)}.nzb");
     }
 
+    // Beyond filesystem-invalid characters, '"' and '\\' must also be stripped: this
+    // filename is later passed as the multipart Content-Disposition "filename" parameter
+    // when submitting to a download client (e.g. SABnzbd), and both characters are valid
+    // on Linux/macOS filesystems but break .NET's ContentDispositionHeaderValue quoting,
+    // throwing ArgumentException and silently failing the whole download. See
+    // https://github.com/Listenarrs/Listenarr/issues/808.
     private static string SanitizeFileName(string value)
         => string.Concat(value.Select(character =>
-            Path.GetInvalidFileNameChars().Contains(character) ? '_' : character));
+            Path.GetInvalidFileNameChars().Contains(character) || character is '"' or '\\'
+                ? '_'
+                : character));
 }

tests/Features/Infrastructure/DownloadClients/Sabnzbd/SabnzbdAdapterTests.cs

@@ -43,6 +43,50 @@ public override async Task InitializeAsync()
                 .Build());
         }
 
+        /// <summary>
+        /// Regression test for https://github.com/Listenarrs/Listenarr/issues/808
+        /// Release titles containing '"' (common in usenet subject lines) crashed
+        /// AddAsync with an ArgumentException from ContentDispositionHeaderValue
+        /// before the request ever reached SABnzbd.
+        /// </summary>
+        [Fact]
+        public async Task AddAsync_TitleContainsQuotesAndCommas_SendsNzbWithoutHeaderEncodingError()
+        {
+            // Given: a real-world release title (from DrunkenSlug/NZBgeek) with embedded
+            // quotes and a comma-decimal size, resolved the way the production pipeline does
+            var title = "DBS #0762 \"J.K. Rowling - Harry Potter 1-7 Audio Book (english)\" - " +
+                "\"Audio book - Harry Potter And The Deathly Hallows - J.K. Rowling.part01.rar\" (02_22) - 672,05 MB";
+            var candidate = new TrustedDownloadCandidate(
+                "release-1",
+                title,
+                "J.K. Rowling",
+                "Harry Potter",
+                "DrunkenSlug (Prowlarr)",
+                "MP3",
+                "en",
+                700_000_000,
+                null,
+                new DownloadSourceDescriptor(
+                    IndexerId: null,
+                    IndexerImplementation: "Newznab",
+                    Protocol: DownloadProtocol.Usenet,
+                    Locators: [new DownloadSourceLocator(DownloadSourceLocatorKind.NzbUrl, "https://indexer.example/nzb/1")]));
+            var downloader = new Mock<INzbFileDownloader>();
+            downloader
+                .Setup(d => d.DownloadAsync(It.IsAny<string>(), It.IsAny<int?>(), It.IsAny<CancellationToken>()))
+                .ReturnsAsync([1, 2, 3]);
+            var resolver = new GenericUsenetSourceResolver(downloader.Object);
+
+            // When: the title is resolved into a prepared submission and sent to SABnzbd
+            var submission = await resolver.ResolveAsync(candidate, provisionalDownloadId: null, CancellationToken.None);
+            var adapter = MockUtils.CreateSabnzbdAdapter(_provider);
+            var result = await adapter.AddAsync(_client, submission);
+
+            // Then: no ArgumentException, and SABnzbd actually received the addfile request
+            Assert.Equal("SABnzbd_nzo_addfile_test", result.ExternalId);
+            Assert.Single(sabnzbdApiMock.AddFileRequests);
+        }
+
         [Fact]
         public async Task TestConnectionAsync_NormalizesHostWithSchemeAndPath()
         {

tests/Mocks/Api/SabnzbdApiMock.cs

@@ -14,10 +14,12 @@ public class SabnzbdApiMock : BaseApiMock
         public System.Net.HttpStatusCode HistoryStatusCode { get; set; } = System.Net.HttpStatusCode.OK;
         public string? HistoryResponseOverride { get; set; }
         public List<Uri> RemovalRequests { get; } = [];
+        public List<Uri> AddFileRequests { get; } = [];
 
         public SabnzbdApiMock()
         {
             AddRoute("api", ProcessRequest, HttpMethod.Get);
+            AddRoute("api", ProcessRequest, HttpMethod.Post);
         }
 
         public async Task<HttpResponseMessage> GetHistory(HttpRequestMessage request, CancellationToken ct)
@@ -101,6 +103,17 @@ public async Task<HttpResponseMessage> GetVersion(HttpRequestMessage request, Ca
             """);
         }
 
+        public async Task<HttpResponseMessage> AddFile(HttpRequestMessage request, CancellationToken ct)
+        {
+            AddFileRequests.Add(request.RequestUri!);
+            return MockUtils.GetCannedResponse("""
+            {
+                "status": true,
+                "nzo_ids": ["SABnzbd_nzo_addfile_test"]
+            }
+            """);
+        }
+
         public async Task<HttpResponseMessage> ProcessRequest(HttpRequestMessage request, CancellationToken ct)
         {
             var query = HttpUtility.ParseQueryString(request.RequestUri.Query);
@@ -110,6 +123,10 @@ public async Task<HttpResponseMessage> ProcessRequest(HttpRequestMessage request
             {
                 return await GetVersion(request, ct);
             }
+            else if (string.Equals("addfile", mode))
+            {
+                return await AddFile(request, ct);
+            }
             else if (string.Equals("history", mode))
             {
                 if (string.Equals("delete", query["name"], StringComparison.Ordinal))