Emby.Server.Implementations/MediaEncoding/TranscodeStoreConnectivityProbe.cs

@@ -0,0 +1,56 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using MediaBrowser.Controller.MediaEncoding;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging;
+using StackExchange.Redis;
+
+namespace Emby.Server.Implementations.MediaEncoding;
+
+/// <summary>
+/// Pings the configured Redis transcode session store once at startup so an unreachable store is
+/// reported there instead of being discovered as a silent loss of cross-pod takeover.
+/// </summary>
+public sealed class TranscodeStoreConnectivityProbe : IHostedService
+{
+    private readonly IServiceProvider _serviceProvider;
+    private readonly ILogger<TranscodeStoreConnectivityProbe> _logger;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="TranscodeStoreConnectivityProbe"/> class.
+    /// </summary>
+    /// <param name="serviceProvider">The service provider used to resolve the Redis connection.</param>
+    /// <param name="logger">The logger.</param>
+    public TranscodeStoreConnectivityProbe(IServiceProvider serviceProvider, ILogger<TranscodeStoreConnectivityProbe> logger)
+    {
+        _serviceProvider = serviceProvider;
+        _logger = logger;
+    }
+
+    /// <inheritdoc />
+    public async Task StartAsync(CancellationToken cancellationToken)
+    {
+        try
+        {
+            // Resolved here rather than injected: connecting must not be able to abort startup.
+            var redis = _serviceProvider.GetRequiredService<IConnectionMultiplexer>();
+            var roundTrip = await redis.GetDatabase().PingAsync().ConfigureAwait(false);
+
+            _logger.LogInformation(
+                "Redis transcode session store is reachable ({RoundTripMs}ms round trip). HA transcode takeover is active.",
+                (long)roundTrip.TotalMilliseconds);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(
+                ex,
+                "Redis transcode session store is configured but UNREACHABLE. HA transcode takeover is not working: sessions stay local to this instance and are lost when it restarts. Check {Key}.",
+                TranscodeStoreOptions.RedisConnectionStringKey);
+        }
+    }
+
+    /// <inheritdoc />
+    public Task StopAsync(CancellationToken cancellationToken) => Task.CompletedTask;
+}

Jellyfin.Server/CoreAppHost.cs

@@ -2,7 +2,6 @@ using System;
 using System.Collections.Generic;
 using System.Reflection;
 using Emby.Server.Implementations;
-using Emby.Server.Implementations.MediaEncoding;
 using Emby.Server.Implementations.ScheduledTasks;
 using Emby.Server.Implementations.Session;
 using Jellyfin.Api.WebSocketListeners;
@@ -10,6 +9,7 @@ using Jellyfin.Database.Implementations;
 using Jellyfin.Drawing;
 using Jellyfin.Drawing.Skia;
 using Jellyfin.LiveTv;
+using Jellyfin.Server.Extensions;
 using Jellyfin.Server.Implementations.Activity;
 using Jellyfin.Server.Implementations.Devices;
 using Jellyfin.Server.Implementations.Events;
@@ -35,7 +35,6 @@ using MediaBrowser.Providers.Lyric;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Logging;
-using StackExchange.Redis;
 
 namespace Jellyfin.Server
 {
@@ -107,29 +106,8 @@ namespace Jellyfin.Server
             serviceCollection.AddScoped<IAuthenticationManager, AuthenticationManager>();
 
             // Transcode session store: Redis-backed when configured, no-op otherwise.
-            serviceCollection.Configure<TranscodeStoreOptions>(_startupConfig.GetSection("Jellyfin:TranscodeStore"));
-            var redisConnectionString = _startupConfig["Jellyfin:TranscodeStore:RedisConnectionString"];
-            if (!string.IsNullOrEmpty(redisConnectionString))
-            {
-                serviceCollection.AddSingleton<IConnectionMultiplexer>(sp =>
-                {
-                    try
-                    {
-                        return ConnectionMultiplexer.Connect(redisConnectionString);
-                    }
-                    catch (Exception ex)
-                    {
-                        sp.GetRequiredService<ILogger<CoreAppHost>>()
-                            .LogError(ex, "Failed to connect to Redis. Check the Jellyfin:TranscodeStore:RedisConnectionString configuration.");
-                        throw;
-                    }
-                });
-                serviceCollection.AddSingleton<ITranscodeSessionStore, RedisTranscodeSessionStore>();
-            }
-            else
-            {
-                serviceCollection.AddSingleton<ITranscodeSessionStore, NullTranscodeSessionStore>();
-            }
+            var redisConnectionString = _startupConfig[TranscodeStoreOptions.RedisConnectionStringKey];
+            serviceCollection.AddTranscodeSessionStore(_startupConfig, Logger);
 
             // Scan-leader lease: gates periodic library-mutating scheduled tasks to a single leader
             // instance. Redis-backed when enabled and a Redis connection is configured, no-op otherwise.

Jellyfin.Server/Extensions/ConfigurationBuilderExtensions.cs

@@ -0,0 +1,51 @@
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.Extensions.Configuration;
+
+namespace Jellyfin.Server.Extensions;
+
+/// <summary>
+/// Extensions for building the application configuration.
+/// </summary>
+public static class ConfigurationBuilderExtensions
+{
+    /// <summary>
+    /// The environment variable prefix that maps onto this fork's own <c>Jellyfin:*</c> configuration
+    /// keys, for example <c>Jellyfin__TranscodeStore__RedisConnectionString</c>.
+    /// </summary>
+    public const string JellyfinSectionEnvironmentPrefix = "Jellyfin__";
+
+    /// <summary>
+    /// The configuration section root this fork keeps its own settings under.
+    /// </summary>
+    public const string JellyfinSectionRoot = "Jellyfin";
+
+    /// <summary>
+    /// Adds environment variables named <c>Jellyfin__Section__Key</c> as the configuration keys
+    /// <c>Jellyfin:Section:Key</c>.
+    /// </summary>
+    /// <remarks>
+    /// The base configuration only reads <c>JELLYFIN_</c> prefixed environment variables, so the
+    /// unprefixed form every manifest, chart and document uses would otherwise be dropped and the
+    /// feature it configures would stay off with no error.
+    /// </remarks>
+    /// <param name="builder">The configuration builder.</param>
+    /// <returns>The updated configuration builder.</returns>
+    public static IConfigurationBuilder AddJellyfinSectionEnvironmentVariables(this IConfigurationBuilder builder)
+    {
+        // Read through the framework provider so "__" to ":" normalisation and case handling match the
+        // prefixed form exactly; the prefix it strips is then put back as the section root.
+        var scoped = new ConfigurationBuilder()
+            .AddEnvironmentVariables(JellyfinSectionEnvironmentPrefix)
+            .Build();
+
+        var entries = scoped.AsEnumerable()
+            .Where(entry => entry.Value is not null)
+            .Select(entry => new KeyValuePair<string, string?>(
+                ConfigurationPath.Combine(JellyfinSectionRoot, entry.Key),
+                entry.Value))
+            .ToList();
+
+        return builder.AddInMemoryCollection(entries);
+    }
+}

Jellyfin.Server/Extensions/TranscodeStoreServiceCollectionExtensions.cs

@@ -0,0 +1,87 @@
+using System;
+using System.Linq;
+using Emby.Server.Implementations.MediaEncoding;
+using MediaBrowser.Controller.MediaEncoding;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+using StackExchange.Redis;
+
+namespace Jellyfin.Server.Extensions;
+
+/// <summary>
+/// Extensions for registering the transcode session store.
+/// </summary>
+public static class TranscodeStoreServiceCollectionExtensions
+{
+    /// <summary>
+    /// Registers the transcode session store, Redis-backed when a connection string is configured and
+    /// no-op otherwise, and reports the selected store at <see cref="LogLevel.Information"/>.
+    /// </summary>
+    /// <param name="serviceCollection">The service collection.</param>
+    /// <param name="configuration">The configuration to read <c>Jellyfin:TranscodeStore</c> from.</param>
+    /// <param name="logger">The logger to report the selected store on.</param>
+    /// <returns>The updated service collection.</returns>
+    public static IServiceCollection AddTranscodeSessionStore(
+        this IServiceCollection serviceCollection,
+        IConfiguration configuration,
+        ILogger logger)
+    {
+        ArgumentNullException.ThrowIfNull(configuration);
+        ArgumentNullException.ThrowIfNull(logger);
+
+        serviceCollection.Configure<TranscodeStoreOptions>(configuration.GetSection(TranscodeStoreOptions.ConfigurationSection));
+
+        var redisConnectionString = configuration[TranscodeStoreOptions.RedisConnectionStringKey];
+        if (string.IsNullOrEmpty(redisConnectionString))
+        {
+            logger.LogInformation(
+                "Transcode session store: {Store}. Cross-pod transcode takeover is off; set {Key} to enable it.",
+                nameof(NullTranscodeSessionStore),
+                TranscodeStoreOptions.RedisConnectionStringKey);
+
+            return serviceCollection.AddSingleton<ITranscodeSessionStore, NullTranscodeSessionStore>();
+        }
+
+        logger.LogInformation(
+            "Transcode session store: {Store} on {Endpoints}.",
+            nameof(RedisTranscodeSessionStore),
+            DescribeEndpoints(redisConnectionString));
+
+        serviceCollection.AddSingleton<IConnectionMultiplexer>(sp =>
+        {
+            try
+            {
+                return ConnectionMultiplexer.Connect(redisConnectionString);
+            }
+            catch (Exception ex)
+            {
+                sp.GetRequiredService<ILogger<CoreAppHost>>()
+                    .LogError(ex, "Failed to connect to Redis. Check the {Key} configuration.", TranscodeStoreOptions.RedisConnectionStringKey);
+                throw;
+            }
+        });
+        serviceCollection.AddSingleton<ITranscodeSessionStore, RedisTranscodeSessionStore>();
+        serviceCollection.AddHostedService<TranscodeStoreConnectivityProbe>();
+
+        return serviceCollection;
+    }
+
+    /// <summary>
+    /// Renders the endpoints of a connection string for logging. The connection string itself is never
+    /// logged because it can carry a password.
+    /// </summary>
+    private static string DescribeEndpoints(string redisConnectionString)
+    {
+        try
+        {
+            return string.Join(
+                ',',
+                ConfigurationOptions.Parse(redisConnectionString).EndPoints.Select(endpoint => endpoint.ToString()));
+        }
+        catch (ArgumentException)
+        {
+            return "(unparsable connection string)";
+        }
+    }
+}

Jellyfin.Server/Program.cs

@@ -391,6 +391,8 @@ namespace Jellyfin.Server
                 .AddInMemoryCollection(inMemoryDefaultConfig)
                 .AddJsonFile(LoggingConfigFileDefault, optional: false, reloadOnChange: true)
                 .AddJsonFile(LoggingConfigFileSystem, optional: true, reloadOnChange: true)
+                // Added before the prefixed source so an explicit JELLYFIN_ variable still wins.
+                .AddJellyfinSectionEnvironmentVariables()
                 .AddEnvironmentVariables("JELLYFIN_")
                 .AddInMemoryCollection(commandLineOpts.ConvertToConfig());
         }

MediaBrowser.Controller/MediaEncoding/TranscodeStoreOptions.cs

@@ -5,6 +5,16 @@ namespace MediaBrowser.Controller.MediaEncoding;
 /// </summary>
 public sealed class TranscodeStoreOptions
 {
+    /// <summary>
+    /// The configuration section these options bind from.
+    /// </summary>
+    public const string ConfigurationSection = "Jellyfin:TranscodeStore";
+
+    /// <summary>
+    /// The configuration key holding the Redis connection string.
+    /// </summary>
+    public const string RedisConnectionStringKey = ConfigurationSection + ":RedisConnectionString";
+
     /// <summary>
     /// Gets or sets the Redis connection string.
     /// A <c>null</c> or empty value indicates single-instance mode, where

README.md

@@ -72,7 +72,7 @@ dotnet run --project Jellyfin.Server/Jellyfin.Server.csproj -- \
 
 ### HA mode with Redis
 
-Set the `Jellyfin:TranscodeStore:RedisConnectionString` configuration key. You can pass it as an environment variable, a `DOTNET_` prefixed env var, or in a JSON config file.
+Set the `Jellyfin:TranscodeStore:RedisConnectionString` configuration key. You can pass it as a `Jellyfin__TranscodeStore__RedisConnectionString` environment variable, as the equivalent `JELLYFIN_` prefixed variable, or in a JSON config file.
 
 **Environment variable:**
 
@@ -98,7 +98,14 @@ dotnet run --project Jellyfin.Server/Jellyfin.Server.csproj -- \
 }
 ```
 
-When `RedisConnectionString` is set, `RedisTranscodeSessionStore` is registered in DI. If the Redis connection fails at startup, the server throws and refuses to start — this is intentional so you don't silently fall back to broken HA behavior.
+The selected store is logged at startup, so HA transcoding is never on or off without a signal:
+
+```
+Transcode session store: RedisTranscodeSessionStore on valkey:6379.
+Redis transcode session store is reachable (2ms round trip). HA transcode takeover is active.
+```
+
+Without a connection string the line reads `Transcode session store: NullTranscodeSessionStore`. A configured but unreachable store is logged at `Error`; the server keeps serving with per-instance sessions rather than refusing to start.
 
 ---
 

docs/FORK-DIFF.md

@@ -37,6 +37,9 @@ auth or plugin logic is rewritten.
 | `MediaBrowser.Controller/MediaEncoding/TranscodeStoreOptions.cs` | `RedisConnectionString`, `LeaseDurationSeconds` and `SessionRetentionSeconds` |
 | `MediaBrowser.Controller/MediaEncoding/NullTranscodeSessionStore.cs` | No-op store used when no Redis connection is configured |
 | `Emby.Server.Implementations/MediaEncoding/RedisTranscodeSessionStore.cs` | Redis store; sessions under `jellyfin:transcode:{playSessionId}`, key TTL is the retention window so an orphaned session outlives its lease |
+| `Emby.Server.Implementations/MediaEncoding/TranscodeStoreConnectivityProbe.cs` | Startup ping; an unreachable configured store is logged at `Error` instead of failing open silently |
+| `Jellyfin.Server/Extensions/TranscodeStoreServiceCollectionExtensions.cs` | Store selection, logged at `Information` so the active store is visible at startup |
+| `Jellyfin.Server/Extensions/ConfigurationBuilderExtensions.cs` | Reads bare `Jellyfin__*` environment variables into the `Jellyfin:*` configuration root |
 
 Lease takeover and renewal each run as a single Lua script, so concurrent pods cannot both
 claim an expired lease and a renewal cannot revert a takeover. The expiry is stored as unix

tests/Jellyfin.Server.Implementations.Tests/MediaEncoding/TranscodeStoreWiringTests.cs

@@ -0,0 +1,103 @@
+using System;
+using System.IO;
+using System.Threading.Tasks;
+using Emby.Server.Implementations.MediaEncoding;
+using Jellyfin.Server;
+using Jellyfin.Server.Extensions;
+using MediaBrowser.Common.Configuration;
+using MediaBrowser.Controller.MediaEncoding;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging.Abstractions;
+using Moq;
+using StackExchange.Redis;
+using Testcontainers.Redis;
+using Xunit;
+
+namespace Jellyfin.Server.Implementations.Tests.MediaEncoding;
+
+/// <summary>
+/// Drives the whole configuration path a deployment uses: a bare <c>Jellyfin__TranscodeStore__*</c>
+/// environment variable, the server's own configuration builder, the store registration, and a
+/// session round-trip against a real Valkey server.
+/// </summary>
+[Trait("Category", "RequiresDocker")]
+public sealed class TranscodeStoreWiringTests : IAsyncLifetime
+{
+    private const string RedisConnectionStringVariable = "Jellyfin__TranscodeStore__RedisConnectionString";
+
+    private readonly RedisContainer _container;
+    private string _configDirectory = string.Empty;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="TranscodeStoreWiringTests"/> class.
+    /// </summary>
+    public TranscodeStoreWiringTests()
+    {
+        _container = new RedisBuilder("valkey/valkey:8-alpine").Build();
+    }
+
+    /// <summary>
+    /// Starts Valkey and lays out the configuration directory the server reads at startup.
+    /// </summary>
+    /// <returns>A <see cref="ValueTask"/> representing the asynchronous operation.</returns>
+    public async ValueTask InitializeAsync()
+    {
+        await _container.StartAsync().ConfigureAwait(false);
+        _configDirectory = Directory.CreateTempSubdirectory("jellyfin-wiring-test").FullName;
+        await File.WriteAllTextAsync(Path.Combine(_configDirectory, "logging.default.json"), "{}").ConfigureAwait(false);
+    }
+
+    /// <summary>
+    /// Removes the environment variable, configuration directory and container.
+    /// </summary>
+    /// <returns>A <see cref="ValueTask"/> representing the asynchronous operation.</returns>
+    public async ValueTask DisposeAsync()
+    {
+        Environment.SetEnvironmentVariable(RedisConnectionStringVariable, null);
+
+        if (_configDirectory.Length > 0)
+        {
+            Directory.Delete(_configDirectory, true);
+        }
+
+        await _container.DisposeAsync().ConfigureAwait(false);
+    }
+
+    /// <summary>
+    /// The variable form deployments set selects the Redis store and that store really talks to Valkey.
+    /// </summary>
+    /// <returns>A <see cref="Task"/> representing the asynchronous operation.</returns>
+    [Fact]
+    public async Task ManifestStyleEnvironmentVariable_Should_Reach_Valkey()
+    {
+        Environment.SetEnvironmentVariable(
+            RedisConnectionStringVariable,
+            _container.GetConnectionString() + ",abortConnect=false");
+
+        var appPaths = new Mock<IApplicationPaths>();
+        appPaths.Setup(paths => paths.ConfigurationDirectoryPath).Returns(_configDirectory);
+        var configuration = Program.CreateAppConfiguration(new StartupOptions(), appPaths.Object);
+
+        var services = new ServiceCollection();
+        services.AddLogging();
+        services.AddTranscodeSessionStore(configuration, NullLogger.Instance);
+
+        await using var provider = services.BuildServiceProvider();
+
+        var store = provider.GetRequiredService<ITranscodeSessionStore>();
+        Assert.IsType<RedisTranscodeSessionStore>(store);
+
+        var playSessionId = Guid.NewGuid().ToString("N");
+        await store.SetAsync(
+            TranscodeSession.CreateForPlaylist(playSessionId, "media-1", "pod-a", "/transcodes/abc.m3u8", TimeSpan.FromSeconds(30)),
+            TestContext.Current.CancellationToken);
+
+        var stored = await store.TryGetAsync(playSessionId, TestContext.Current.CancellationToken);
+
+        Assert.NotNull(stored);
+        Assert.Equal("pod-a", stored.OwnerPod);
+
+        var redis = provider.GetRequiredService<IConnectionMultiplexer>();
+        Assert.True(await redis.GetDatabase().KeyExistsAsync("jellyfin:transcode:" + playSessionId));
+    }
+}

tests/Jellyfin.Server.Tests/HighAvailability/JellyfinSectionConfigurationTests.cs

@@ -0,0 +1,95 @@
+using System;
+using System.IO;
+using MediaBrowser.Common.Configuration;
+using Microsoft.Extensions.Configuration;
+using Moq;
+using Xunit;
+
+namespace Jellyfin.Server.Tests.HighAvailability;
+
+/// <summary>
+/// The fork's own settings live under the <c>Jellyfin:*</c> configuration root and every manifest,
+/// chart and document sets them as bare <c>Jellyfin__Section__Key</c> environment variables. The
+/// startup configuration the host reads them from must therefore accept that form; when it does not,
+/// a correctly set variable is dropped and the feature it configures stays off without any error.
+/// </summary>
+public sealed class JellyfinSectionConfigurationTests : IDisposable
+{
+    private const string RedisKey = "Jellyfin:TranscodeStore:RedisConnectionString";
+    private const string UnprefixedVariable = "Jellyfin__TranscodeStore__RedisConnectionString";
+    private const string PrefixedVariable = "JELLYFIN_Jellyfin__TranscodeStore__RedisConnectionString";
+    private const string LeaseUnprefixedVariable = "Jellyfin__TranscodeStore__LeaseDurationSeconds";
+
+    private readonly string _configDirectory;
+
+    public JellyfinSectionConfigurationTests()
+    {
+        _configDirectory = Directory.CreateTempSubdirectory("jellyfin-config-test").FullName;
+        File.WriteAllText(Path.Combine(_configDirectory, "logging.default.json"), "{}");
+    }
+
+    public void Dispose()
+    {
+        Environment.SetEnvironmentVariable(UnprefixedVariable, null);
+        Environment.SetEnvironmentVariable(PrefixedVariable, null);
+        Environment.SetEnvironmentVariable(LeaseUnprefixedVariable, null);
+        Directory.Delete(_configDirectory, true);
+    }
+
+    [Fact]
+    public void CreateAppConfiguration_Should_Read_UnprefixedVariable()
+    {
+        Environment.SetEnvironmentVariable(UnprefixedVariable, "valkey-cheeztv-valkey:6379,abortConnect=false");
+
+        var config = CreateConfiguration();
+
+        Assert.Equal("valkey-cheeztv-valkey:6379,abortConnect=false", config[RedisKey]);
+    }
+
+    [Fact]
+    public void CreateAppConfiguration_Should_Read_UnprefixedNonStringValue()
+    {
+        Environment.SetEnvironmentVariable(LeaseUnprefixedVariable, "45");
+
+        var config = CreateConfiguration();
+
+        Assert.Equal("45", config["Jellyfin:TranscodeStore:LeaseDurationSeconds"]);
+    }
+
+    [Fact]
+    public void CreateAppConfiguration_Should_Read_PrefixedVariable()
+    {
+        Environment.SetEnvironmentVariable(PrefixedVariable, "redis:6379");
+
+        var config = CreateConfiguration();
+
+        Assert.Equal("redis:6379", config[RedisKey]);
+    }
+
+    [Fact]
+    public void CreateAppConfiguration_Should_Prefer_PrefixedVariable()
+    {
+        Environment.SetEnvironmentVariable(UnprefixedVariable, "unprefixed:6379");
+        Environment.SetEnvironmentVariable(PrefixedVariable, "prefixed:6379");
+
+        var config = CreateConfiguration();
+
+        Assert.Equal("prefixed:6379", config[RedisKey]);
+    }
+
+    [Fact]
+    public void CreateAppConfiguration_Should_Leave_Key_Unset_Without_Variables()
+    {
+        var config = CreateConfiguration();
+
+        Assert.Null(config[RedisKey]);
+    }
+
+    private IConfiguration CreateConfiguration()
+    {
+        var appPaths = new Mock<IApplicationPaths>();
+        appPaths.Setup(paths => paths.ConfigurationDirectoryPath).Returns(_configDirectory);
+
+        return Program.CreateAppConfiguration(new StartupOptions(), appPaths.Object);
+    }
+}

tests/Jellyfin.Server.Tests/HighAvailability/RecordingLogger.cs

@@ -0,0 +1,42 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.Extensions.Logging;
+
+namespace Jellyfin.Server.Tests.HighAvailability;
+
+/// <summary>
+/// An <see cref="ILogger"/> that keeps every formatted entry so tests can assert on the startup
+/// signals operators rely on.
+/// </summary>
+/// <typeparam name="T">The category type.</typeparam>
+internal sealed class RecordingLogger<T> : ILogger<T>
+{
+    private readonly List<(LogLevel Level, string Message, Exception? Exception)> _entries = new();
+
+    public IReadOnlyList<(LogLevel Level, string Message, Exception? Exception)> Entries => _entries;
+
+    public IDisposable BeginScope<TState>(TState state)
+        where TState : notnull
+        => NoopScope.Instance;
+
+    public bool IsEnabled(LogLevel logLevel) => true;
+
+    public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception? exception, Func<TState, Exception?, string> formatter)
+    {
+        ArgumentNullException.ThrowIfNull(formatter);
+        _entries.Add((logLevel, formatter(state, exception), exception));
+    }
+
+    public bool HasEntry(LogLevel level, string substring)
+        => _entries.Any(entry => entry.Level == level && entry.Message.Contains(substring, StringComparison.Ordinal));
+
+    private sealed class NoopScope : IDisposable
+    {
+        public static readonly NoopScope Instance = new();
+
+        public void Dispose()
+        {
+        }
+    }
+}

tests/Jellyfin.Server.Tests/HighAvailability/TranscodeStoreConnectivityProbeTests.cs

@@ -0,0 +1,75 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using Emby.Server.Implementations.MediaEncoding;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+using Moq;
+using StackExchange.Redis;
+using Xunit;
+
+namespace Jellyfin.Server.Tests.HighAvailability;
+
+/// <summary>
+/// A Redis store that cannot be reached degrades silently: the client is configured not to abort the
+/// connection and every call site swallows failures. The probe is the only startup signal, so both of
+/// its outcomes are pinned here.
+/// </summary>
+public sealed class TranscodeStoreConnectivityProbeTests
+{
+    [Fact]
+    public async Task StartAsync_Should_Log_Information_When_Reachable()
+    {
+        var database = new Mock<IDatabase>();
+        database.Setup(db => db.PingAsync(It.IsAny<CommandFlags>())).ReturnsAsync(TimeSpan.FromMilliseconds(3));
+
+        var (logger, probe) = CreateProbe(database.Object);
+
+        await probe.StartAsync(CancellationToken.None);
+
+        Assert.True(logger.HasEntry(LogLevel.Information, "reachable"));
+        Assert.DoesNotContain(logger.Entries, entry => entry.Level >= LogLevel.Warning);
+    }
+
+    [Fact]
+    public async Task StartAsync_Should_Log_Error_When_Unreachable()
+    {
+        var database = new Mock<IDatabase>();
+        database.Setup(db => db.PingAsync(It.IsAny<CommandFlags>()))
+            .ThrowsAsync(new RedisConnectionException(ConnectionFailureType.UnableToConnect, "no route to host"));
+
+        var (logger, probe) = CreateProbe(database.Object);
+
+        await probe.StartAsync(CancellationToken.None);
+
+        Assert.True(logger.HasEntry(LogLevel.Error, "UNREACHABLE"));
+    }
+
+    [Fact]
+    public async Task StartAsync_Should_Log_Error_Instead_Of_Aborting_Startup()
+    {
+        var services = new ServiceCollection();
+        services.AddSingleton<IConnectionMultiplexer>(_ => throw new RedisConnectionException(ConnectionFailureType.UnableToConnect, "no route to host"));
+        using var provider = services.BuildServiceProvider();
+
+        var logger = new RecordingLogger<TranscodeStoreConnectivityProbe>();
+        var probe = new TranscodeStoreConnectivityProbe(provider, logger);
+
+        await probe.StartAsync(CancellationToken.None);
+
+        Assert.True(logger.HasEntry(LogLevel.Error, "UNREACHABLE"));
+    }
+
+    private static (RecordingLogger<TranscodeStoreConnectivityProbe> Logger, TranscodeStoreConnectivityProbe Probe) CreateProbe(IDatabase database)
+    {
+        var multiplexer = new Mock<IConnectionMultiplexer>();
+        multiplexer.Setup(redis => redis.GetDatabase(It.IsAny<int>(), It.IsAny<object>())).Returns(database);
+
+        var services = new ServiceCollection();
+        services.AddSingleton(multiplexer.Object);
+        var provider = services.BuildServiceProvider();
+
+        var logger = new RecordingLogger<TranscodeStoreConnectivityProbe>();
+        return (logger, new TranscodeStoreConnectivityProbe(provider, logger));
+    }
+}

tests/Jellyfin.Server.Tests/HighAvailability/TranscodeStoreRegistrationTests.cs

@@ -0,0 +1,104 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Emby.Server.Implementations.MediaEncoding;
+using Jellyfin.Server.Extensions;
+using MediaBrowser.Controller.MediaEncoding;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;
+using Xunit;
+
+namespace Jellyfin.Server.Tests.HighAvailability;
+
+/// <summary>
+/// Which transcode session store was selected is invisible at runtime — the Redis client does not
+/// abort on an unreachable server and every call site swallows failures — so the selection is
+/// asserted here together with the startup log line that reports it.
+/// </summary>
+public sealed class TranscodeStoreRegistrationTests
+{
+    [Fact]
+    public void AddTranscodeSessionStore_Should_Select_RedisStore_From_UnprefixedEnvironmentKeyShape()
+    {
+        var services = new ServiceCollection();
+        var logger = new RecordingLogger<TranscodeStoreRegistrationTests>();
+
+        services.AddTranscodeSessionStore(BuildConfiguration("valkey-cheeztv-valkey:6379,abortConnect=false"), logger);
+
+        Assert.Equal(typeof(RedisTranscodeSessionStore), StoreImplementation(services));
+        Assert.True(logger.HasEntry(LogLevel.Information, nameof(RedisTranscodeSessionStore)));
+    }
+
+    [Fact]
+    public void AddTranscodeSessionStore_Should_Select_NullStore_Without_ConnectionString()
+    {
+        var services = new ServiceCollection();
+        var logger = new RecordingLogger<TranscodeStoreRegistrationTests>();
+
+        services.AddTranscodeSessionStore(BuildConfiguration(null), logger);
+
+        Assert.Equal(typeof(NullTranscodeSessionStore), StoreImplementation(services));
+        Assert.True(logger.HasEntry(LogLevel.Information, nameof(NullTranscodeSessionStore)));
+    }
+
+    [Fact]
+    public void AddTranscodeSessionStore_Should_Log_Endpoints_Without_Password()
+    {
+        var services = new ServiceCollection();
+        var logger = new RecordingLogger<TranscodeStoreRegistrationTests>();
+
+        services.AddTranscodeSessionStore(BuildConfiguration("valkey:6379,password=hunter2"), logger);
+
+        var message = Assert.Single(logger.Entries, entry => entry.Level == LogLevel.Information).Message;
+        Assert.Contains("valkey:6379", message, StringComparison.Ordinal);
+        Assert.DoesNotContain("hunter2", message, StringComparison.Ordinal);
+    }
+
+    [Fact]
+    public void AddTranscodeSessionStore_Should_Register_ConnectivityProbe_Only_With_Redis()
+    {
+        var withRedis = new ServiceCollection();
+        withRedis.AddTranscodeSessionStore(BuildConfiguration("valkey:6379"), new RecordingLogger<TranscodeStoreRegistrationTests>());
+
+        var withoutRedis = new ServiceCollection();
+        withoutRedis.AddTranscodeSessionStore(BuildConfiguration(null), new RecordingLogger<TranscodeStoreRegistrationTests>());
+
+        Assert.Contains(withRedis, descriptor => descriptor.ImplementationType == typeof(TranscodeStoreConnectivityProbe));
+        Assert.DoesNotContain(withoutRedis, descriptor => descriptor.ServiceType == typeof(IHostedService));
+    }
+
+    [Fact]
+    public void AddTranscodeSessionStore_Should_Bind_Options()
+    {
+        var services = new ServiceCollection();
+        var configuration = new ConfigurationBuilder()
+            .AddInMemoryCollection(new Dictionary<string, string?>
+            {
+                [TranscodeStoreOptions.RedisConnectionStringKey] = "valkey:6379",
+                ["Jellyfin:TranscodeStore:LeaseDurationSeconds"] = "45"
+            })
+            .Build();
+
+        services.AddTranscodeSessionStore(configuration, new RecordingLogger<TranscodeStoreRegistrationTests>());
+
+        using var provider = services.BuildServiceProvider();
+        var options = provider.GetRequiredService<IOptions<TranscodeStoreOptions>>().Value;
+
+        Assert.Equal(45, options.LeaseDurationSeconds);
+        Assert.Equal("valkey:6379", options.RedisConnectionString);
+    }
+
+    private static IConfiguration BuildConfiguration(string? redisConnectionString)
+        => new ConfigurationBuilder()
+            .AddInMemoryCollection(new Dictionary<string, string?>
+            {
+                [TranscodeStoreOptions.RedisConnectionStringKey] = redisConnectionString
+            })
+            .Build();
+
+    private static Type? StoreImplementation(IServiceCollection services)
+        => services.Single(descriptor => descriptor.ServiceType == typeof(ITranscodeSessionStore)).ImplementationType;
+}