From 33496c16932b115c7f628d8aa3cb52e3522c4874 Mon Sep 17 00:00:00 2001
From: MBR#0001 <mbr@mbr.pw>
Date: Sun, 8 Feb 2026 11:10:09 +0100
Subject: [PATCH] Fix broken library subtitle download settings

---
 .../FixLibrarySubtitleDownloadLanguages.cs    | 106 ++++++++++++++++++
 1 file changed, 106 insertions(+)
 create mode 100644 Jellyfin.Server/Migrations/Routines/FixLibrarySubtitleDownloadLanguages.cs

diff --git a/Jellyfin.Server/Migrations/Routines/FixLibrarySubtitleDownloadLanguages.cs b/Jellyfin.Server/Migrations/Routines/FixLibrarySubtitleDownloadLanguages.cs
new file mode 100644
index 0000000000..e82123e5ac
--- /dev/null
+++ b/Jellyfin.Server/Migrations/Routines/FixLibrarySubtitleDownloadLanguages.cs
@@ -0,0 +1,106 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Jellyfin.Server.ServerSetupApp;
+using MediaBrowser.Controller.Entities;
+using MediaBrowser.Controller.Library;
+using MediaBrowser.Model.Globalization;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging;
+
+namespace Jellyfin.Server.Migrations.Routines;
+
+/// <summary>
+/// Migration to fix broken library subtitle download languages.
+/// </summary>
+[JellyfinMigration("2026-02-06T20:00:00", nameof(FixLibrarySubtitleDownloadLanguages))]
+internal class FixLibrarySubtitleDownloadLanguages : IAsyncMigrationRoutine
+{
+    private readonly ILocalizationManager _localizationManager;
+    private readonly ILibraryManager _libraryManager;
+    private readonly ILogger _logger;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="FixLibrarySubtitleDownloadLanguages"/> class.
+    /// </summary>
+    /// <param name="localizationManager">The Localization manager.</param>
+    /// <param name="startupLogger">The startup logger for Startup UI integration.</param>
+    /// <param name="libraryManager">The Library manager.</param>
+    /// <param name="logger">The logger.</param>
+    public FixLibrarySubtitleDownloadLanguages(
+        ILocalizationManager localizationManager,
+        IStartupLogger<FixLibrarySubtitleDownloadLanguages> startupLogger,
+        ILibraryManager libraryManager,
+        ILogger<FixLibrarySubtitleDownloadLanguages> logger)
+    {
+        _localizationManager = localizationManager;
+        _libraryManager = libraryManager;
+        _logger = startupLogger.With(logger);
+    }
+
+    /// <inheritdoc />
+    public Task PerformAsync(CancellationToken cancellationToken)
+    {
+        _logger.LogInformation("Starting to fix library subtitle download languages.");
+
+        var virtualFolders = _libraryManager.GetVirtualFolders(false);
+
+        foreach (var virtualFolder in virtualFolders)
+        {
+            var options = virtualFolder.LibraryOptions;
+            if (options.SubtitleDownloadLanguages is null || options.SubtitleDownloadLanguages.Length == 0)
+            {
+                continue;
+            }
+
+            // Some virtual folders don't have a proper item id.
+            if (!Guid.TryParse(virtualFolder.ItemId, out var folderId))
+            {
+                continue;
+            }
+
+            var collectionFolder = _libraryManager.GetItemById<CollectionFolder>(folderId);
+            if (collectionFolder is null)
+            {
+                _logger.LogWarning("Could not find collection folder for virtual folder '{LibraryName}' with id '{FolderId}'. Skipping.", virtualFolder.Name, folderId);
+                continue;
+            }
+
+            var fixedLanguages = new List<string>();
+
+            foreach (var language in options.SubtitleDownloadLanguages)
+            {
+                var foundLanguage = _localizationManager.FindLanguageInfo(language)?.ThreeLetterISOLanguageName;
+                if (foundLanguage is not null)
+                {
+                    // Converted ISO 639-2/B to T (ger to deu)
+                    if (!string.Equals(foundLanguage, language, StringComparison.OrdinalIgnoreCase))
+                    {
+                        _logger.LogInformation("Converted '{Language}' to '{ResolvedLanguage}' in library '{LibraryName}'.", language, foundLanguage, virtualFolder.Name);
+                    }
+
+                    if (fixedLanguages.Contains(foundLanguage, StringComparer.OrdinalIgnoreCase))
+                    {
+                        _logger.LogInformation("Language '{Language}' already exists for library '{LibraryName}'. Skipping duplicate.", foundLanguage, virtualFolder.Name);
+                        continue;
+                    }
+
+                    fixedLanguages.Add(foundLanguage);
+                }
+                else
+                {
+                    _logger.LogInformation("Could not resolve language '{Language}' in library '{LibraryName}'. Skipping.", language, virtualFolder.Name);
+                }
+            }
+
+            options.SubtitleDownloadLanguages = [.. fixedLanguages];
+            collectionFolder.UpdateLibraryOptions(options);
+        }
+
+        _logger.LogInformation("Library subtitle download languages fixed.");
+
+        return Task.CompletedTask;
+    }
+}