diff --git a/src/Server/ZB.MOM.WW.OtOpcUa.Security/Auth/AutoLoginAuthenticationHandler.cs b/src/Server/ZB.MOM.WW.OtOpcUa.Security/Auth/AutoLoginAuthenticationHandler.cs
index 7e130725..0ef99825 100644
--- a/src/Server/ZB.MOM.WW.OtOpcUa.Security/Auth/AutoLoginAuthenticationHandler.cs
+++ b/src/Server/ZB.MOM.WW.OtOpcUa.Security/Auth/AutoLoginAuthenticationHandler.cs
@@ -15,7 +15,7 @@ namespace ZB.MOM.WW.OtOpcUa.Security.Auth;
 ///     The minted principal mirrors the shape the real login (AuthEndpoints) produces.
 /// </summary>
 public sealed class AutoLoginAuthenticationHandler
-    : AuthenticationHandler<AuthenticationSchemeOptions>
+    : AuthenticationHandler<AuthenticationSchemeOptions>, IAuthenticationSignInHandler
 {
     private readonly AuthDisableLoginOptions _opts;
 
@@ -32,6 +32,12 @@ public sealed class AutoLoginAuthenticationHandler
         : base(options, logger, encoder)
         => _opts = disableLoginOptions.Value;
 
+    /// <summary>No-op: auto-login writes no cookie, so an explicit sign-in has nothing to persist.</summary>
+    public Task SignInAsync(ClaimsPrincipal user, AuthenticationProperties? properties) => Task.CompletedTask;
+
+    /// <summary>No-op: there is no auth cookie to clear; the next request re-authenticates via this handler.</summary>
+    public Task SignOutAsync(AuthenticationProperties? properties) => Task.CompletedTask;
+
     /// <inheritdoc />
     protected override Task<AuthenticateResult> HandleAuthenticateAsync()
     {
diff --git a/tests/Server/ZB.MOM.WW.OtOpcUa.Security.Tests/AutoLoginAuthenticationHandlerTests.cs b/tests/Server/ZB.MOM.WW.OtOpcUa.Security.Tests/AutoLoginAuthenticationHandlerTests.cs
index 145044ec..8f3e9f52 100644
--- a/tests/Server/ZB.MOM.WW.OtOpcUa.Security.Tests/AutoLoginAuthenticationHandlerTests.cs
+++ b/tests/Server/ZB.MOM.WW.OtOpcUa.Security.Tests/AutoLoginAuthenticationHandlerTests.cs
@@ -1,3 +1,4 @@
+using System.Security.Claims;
 using System.Text.Encodings.Web;
 using Microsoft.AspNetCore.Authentication;
 using Microsoft.AspNetCore.Authentication.Cookies;
@@ -12,7 +13,7 @@ namespace ZB.MOM.WW.OtOpcUa.Security.Tests;
 
 public class AutoLoginAuthenticationHandlerTests
 {
-    private static async Task<AuthenticateResult> AuthenticateAsync(string user = "multi-role-test")
+    private static async Task<AutoLoginAuthenticationHandler> BuildHandlerAsync(string user = "multi-role-test")
     {
         var schemeOpts = new StubOptionsMonitor<AuthenticationSchemeOptions>(new AuthenticationSchemeOptions());
         var disableOpts = Options.Create(new AuthDisableLoginOptions { DisableLogin = true, User = user });
@@ -23,6 +24,12 @@ public class AutoLoginAuthenticationHandlerTests
             new AuthenticationScheme(
                 CookieAuthenticationDefaults.AuthenticationScheme, null, typeof(AutoLoginAuthenticationHandler)),
             new DefaultHttpContext());
+        return handler;
+    }
+
+    private static async Task<AuthenticateResult> AuthenticateAsync(string user = "multi-role-test")
+    {
+        var handler = await BuildHandlerAsync(user);
         return await handler.AuthenticateAsync();
     }
 
@@ -48,6 +55,17 @@ public class AutoLoginAuthenticationHandlerTests
         result.Principal!.Identity!.Name.ShouldBe("custom-dev");
     }
 
+    [Fact]
+    public async Task SignIn_and_SignOut_are_noops_and_do_not_throw()
+    {
+        var handler = await BuildHandlerAsync();
+        await Should.NotThrowAsync(async () =>
+        {
+            await ((IAuthenticationSignInHandler)handler).SignInAsync(new ClaimsPrincipal(), null);
+            await ((IAuthenticationSignOutHandler)handler).SignOutAsync(null);
+        });
+    }
+
     /// <summary>
     ///     Minimal <see cref="IOptionsMonitor{TOptions}"/> stub returning a fixed value for any
     ///     name. The test project does not reference Moq, so the scheme-options monitor the base