diff --git a/tests/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer.IntegrationTests/Sdk2HostConcurrentDisposalTests.cs b/tests/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer.IntegrationTests/Sdk2HostConcurrentDisposalTests.cs
new file mode 100644
index 00000000..12414b79
--- /dev/null
+++ b/tests/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer.IntegrationTests/Sdk2HostConcurrentDisposalTests.cs
@@ -0,0 +1,99 @@
+using Opc.Ua;
+using Opc.Ua.Configuration;
+using Opc.Ua.Server;
+using Shouldly;
+using Xunit;
+using ClientSession = Opc.Ua.Client.ISession;
+
+namespace ZB.MOM.WW.OtOpcUa.OpcUaServer.IntegrationTests;
+
+public sealed partial class Sdk2LifecycleSoakTests
+{
+    /// <summary>Concurrent host disposal awaits real encrypted-session shutdown before clearing ownership.</summary>
+    [Fact]
+    public async Task Concurrent_host_disposal_waits_for_the_actual_encrypted_session_to_close()
+    {
+        var ct = TestContext.Current.CancellationToken;
+        var clientRoot = Path.Combine(Path.GetTempPath(), $"otua-dispose-client-{Guid.NewGuid():N}");
+        ApplicationInstance? application = null;
+        ServerEventRig? rig = null;
+        ClientSession? client = null;
+        ISessionManager? sessionManager = null;
+        SessionEventHandler? closing = null;
+        using var release = new ManualResetEventSlim(false);
+        var entered = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
+        var calls = new List<Task>();
+        var timedOut = 0;
+        var callbackCount = 0;
+        try
+        {
+            var telemetry = DefaultTelemetry.Create(_ => { });
+            var security = TestClientSecurity.Build(clientRoot);
+            security.ApplicationCertificate!.SubjectName = "CN=SDK2LifecycleSoak";
+            var config = new ApplicationConfiguration(telemetry)
+            {
+                ApplicationName = "SDK2LifecycleSoak", ApplicationUri = $"urn:SDK2LifecycleSoak:{Guid.NewGuid():N}",
+                ApplicationType = ApplicationType.Client, SecurityConfiguration = security,
+                ClientConfiguration = new ClientConfiguration { DefaultSessionTimeout = 15_000 },
+                TransportQuotas = new TransportQuotas { OperationTimeout = 5000 },
+            };
+            application = new ApplicationInstance(telemetry) { ApplicationConfiguration = config };
+            await config.ValidateAsync(ApplicationType.Client, ct);
+            await application.CheckApplicationInstanceCertificatesAsync(true, null, ct);
+            rig = await ServerEventRig.StartAsync("SDK2ConcurrentDisposal", encrypted: true, ct);
+            Configure(rig);
+            client = await ConnectAsync(rig, config, null, ct);
+            sessionManager = rig.Server.CurrentInstance.SessionManager;
+            sessionManager.GetSessions().Count.ShouldBe(1);
+            var sessionId = client.SessionId;
+            closing = (session, reason) =>
+            {
+                if (session.Id != sessionId || reason != SessionEventReason.Closing) return;
+                Interlocked.Increment(ref callbackCount);
+                entered.TrySetResult();
+                // SDK swallows event exceptions; keep an explicit failure flag for this bounded barrier.
+                if (!release.Wait(TimeSpan.FromSeconds(15))) Interlocked.Exchange(ref timedOut, 1);
+            };
+            sessionManager.SessionClosing += closing;
+            var host = RequiredField<OpcUaApplicationHost>(rig, "_host");
+            var manager = rig.Server.CertificateManager!;
+            calls.Add(Task.Run(async () => await host.DisposeAsync(), ct));
+            await entered.Task.WaitAsync(TimeSpan.FromSeconds(10), ct);
+            for (var i = 0; i < 3; i++) calls.Add(host.DisposeAsync().AsTask());
+            calls.ShouldAllBe(call => !call.IsCompleted, "every caller must await the actual shutdown owner");
+            host.Server.ShouldBeSameAs(rig.Server);
+            RequiredField<bool>(manager, "m_disposed").ShouldBeFalse();
+            release.Set();
+            await Task.WhenAll(calls).WaitAsync(TimeSpan.FromSeconds(20), ct);
+            Volatile.Read(ref timedOut).ShouldBe(0);
+            Volatile.Read(ref callbackCount).ShouldBe(1);
+            host.Server.ShouldBeNull();
+            host.ApplicationInstance.ShouldBeNull();
+            RequiredField<bool>(manager, "m_disposed").ShouldBeTrue();
+            CertificateCores(manager).Sum(CachedStores).ShouldBe(0);
+        }
+        finally
+        {
+            // Removing a handler takes the SDK's event lock: release before awaiting or unsubscribing.
+            release.Set();
+            try { await Task.WhenAll(calls).WaitAsync(TimeSpan.FromSeconds(20), CancellationToken.None); }
+            finally
+            {
+                try { if (sessionManager is not null && closing is not null) sessionManager.SessionClosing -= closing; }
+                finally
+                {
+                    try { client?.Dispose(); }
+                    finally
+                    {
+                        try { if (rig is not null) await rig.DisposeAsync().AsTask().WaitAsync(TimeSpan.FromSeconds(20), CancellationToken.None); }
+                        finally
+                        {
+                            try { if (application is not null) await application.DisposeAsync().AsTask().WaitAsync(TimeSpan.FromSeconds(20), CancellationToken.None); }
+                            finally { if (Directory.Exists(clientRoot)) Directory.Delete(clientRoot, true); }
+                        }
+                    }
+                }
+            }
+        }
+    }
+}