Extract truncation logic to helper and add tests

Emby.Server.Implementations/Localization/LocalizationManager.cs

@@ -261,6 +261,24 @@ namespace Emby.Server.Implementations.Localization
                 _cultures);
         }
 
+        /// <inheritdoc />
+        public string? GetLanguageDisplayName(string language)
+        {
+            if (string.IsNullOrEmpty(language))
+            {
+                return null;
+            }
+
+            var displayName = FindLanguageInfo(language)?.DisplayName;
+            if (displayName is null)
+            {
+                return null;
+            }
+
+            // Truncate at the first delimiter to avoid cluttered display names
+            return displayName.Split([';', ','], StringSplitOptions.None)[0].Trim();
+        }
+
         /// <inheritdoc />
         public IReadOnlyList<CountryInfo> GetCountries()
         {

Jellyfin.Server.Implementations/Item/MediaStreamRepository.cs

@@ -172,11 +172,7 @@ public class MediaStreamRepository : IMediaStreamRepository
 
             if (!string.IsNullOrEmpty(dto.Language))
             {
-                var culture = _localization.FindLanguageInfo(dto.Language);
-                // Truncate at the first delimiter to avoid cluttered display names
-                dto.LocalizedLanguage = culture?.DisplayName is { } name
-                    ? name.Split([';', ','])[0].Trim()
-                    : null;
+                dto.LocalizedLanguage = _localization.GetLanguageDisplayName(dto.Language);
             }
 
             if (dto.Type is MediaStreamType.Audio)

MediaBrowser.MediaEncoding/Probing/ProbeResultNormalizer.cs

@@ -732,9 +732,7 @@ namespace MediaBrowser.MediaEncoding.Probing
                 stream.LocalizedOriginal = _localization.GetLocalizedString("Original");
                 if (!string.IsNullOrEmpty(stream.Language))
                 {
-                    stream.LocalizedLanguage = _localization.FindLanguageInfo(stream.Language)?.DisplayName is { } name
-                        ? name.Split([';', ','])[0].Trim()
-                        : null;
+                    stream.LocalizedLanguage = _localization.GetLanguageDisplayName(stream.Language);
                 }
 
                 stream.Channels = streamInfo.Channels;
@@ -776,9 +774,7 @@ namespace MediaBrowser.MediaEncoding.Probing
                 stream.LocalizedHearingImpaired = _localization.GetLocalizedString("HearingImpaired");
                 if (!string.IsNullOrEmpty(stream.Language))
                 {
-                    stream.LocalizedLanguage = _localization.FindLanguageInfo(stream.Language)?.DisplayName is { } name
-                        ? name.Split([';', ','])[0].Trim()
-                        : null;
+                    stream.LocalizedLanguage = _localization.GetLanguageDisplayName(stream.Language);
                 }
 
                 if (string.IsNullOrEmpty(stream.Title))

MediaBrowser.Model/Globalization/ILocalizationManager.cs

@@ -72,6 +72,14 @@ public interface ILocalizationManager
     /// <returns>The correct <see cref="CultureDto" /> for the given language.</returns>
     CultureDto? FindLanguageInfo(string language);
 
+    /// <summary>
+    /// Gets a human-readable display name for the given language code.
+    /// Truncates at the first semicolon or comma to avoid cluttered ISO-639-2 names.
+    /// </summary>
+    /// <param name="language">An ISO language code.</param>
+    /// <returns>The display name, or null if not found.</returns>
+    string? GetLanguageDisplayName(string language);
+
     /// <summary>
     /// Returns the language in ISO 639-2/T when the input is ISO 639-2/B.
     /// </summary>

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()
         {