diff --git a/src/ZB.MOM.WW.MxGateway.Tests/Gateway/Dashboard/DashboardCookieOptionsTests.cs b/src/ZB.MOM.WW.MxGateway.Tests/Gateway/Dashboard/DashboardCookieOptionsTests.cs
index a28acff..95ed26c 100644
--- a/src/ZB.MOM.WW.MxGateway.Tests/Gateway/Dashboard/DashboardCookieOptionsTests.cs
+++ b/src/ZB.MOM.WW.MxGateway.Tests/Gateway/Dashboard/DashboardCookieOptionsTests.cs
@@ -5,11 +5,9 @@ using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Options;
 using ZB.MOM.WW.MxGateway.Server;
 using ZB.MOM.WW.MxGateway.Server.Dashboard;
-using ZB.MOM.WW.MxGateway.Tests.Gateway;
 
 namespace ZB.MOM.WW.MxGateway.Tests.Gateway.Dashboard;
 
-[Collection(HostBuildingCollection.Name)]
 public sealed class DashboardCookieOptionsTests
 {
     /// <summary>Verifies that the application configures secure dashboard authentication cookies.</summary>
diff --git a/src/ZB.MOM.WW.MxGateway.Tests/Gateway/Dashboard/DashboardHubsRegistrationTests.cs b/src/ZB.MOM.WW.MxGateway.Tests/Gateway/Dashboard/DashboardHubsRegistrationTests.cs
index ff6f2fa..3348029 100644
--- a/src/ZB.MOM.WW.MxGateway.Tests/Gateway/Dashboard/DashboardHubsRegistrationTests.cs
+++ b/src/ZB.MOM.WW.MxGateway.Tests/Gateway/Dashboard/DashboardHubsRegistrationTests.cs
@@ -4,11 +4,9 @@ using Microsoft.Extensions.DependencyInjection;
 using ZB.MOM.WW.MxGateway.Server;
 using ZB.MOM.WW.MxGateway.Server.Dashboard;
 using ZB.MOM.WW.MxGateway.Server.Dashboard.Hubs;
-using ZB.MOM.WW.MxGateway.Tests.Gateway;
 
 namespace ZB.MOM.WW.MxGateway.Tests.Gateway.Dashboard;
 
-[Collection(HostBuildingCollection.Name)]
 public sealed class DashboardHubsRegistrationTests
 {
     /// <summary>Verifies that dashboard build maps all three hubs and token endpoint.</summary>
diff --git a/src/ZB.MOM.WW.MxGateway.Tests/Gateway/GatewayApplicationTests.cs b/src/ZB.MOM.WW.MxGateway.Tests/Gateway/GatewayApplicationTests.cs
index 0890398..5f2c746 100644
--- a/src/ZB.MOM.WW.MxGateway.Tests/Gateway/GatewayApplicationTests.cs
+++ b/src/ZB.MOM.WW.MxGateway.Tests/Gateway/GatewayApplicationTests.cs
@@ -9,7 +9,6 @@ using ZB.MOM.WW.MxGateway.Server.Metrics;
 
 namespace ZB.MOM.WW.MxGateway.Tests.Gateway;
 
-[Collection(HostBuildingCollection.Name)]
 public sealed class GatewayApplicationTests
 {
     /// <summary>Verifies that Build maps the live health check endpoint.</summary>
diff --git a/src/ZB.MOM.WW.MxGateway.Tests/Gateway/HostBuildingCollection.cs b/src/ZB.MOM.WW.MxGateway.Tests/Gateway/HostBuildingCollection.cs
deleted file mode 100644
index fce3f29..0000000
--- a/src/ZB.MOM.WW.MxGateway.Tests/Gateway/HostBuildingCollection.cs
+++ /dev/null
@@ -1,21 +0,0 @@
-namespace ZB.MOM.WW.MxGateway.Tests.Gateway;
-
-/// <summary>
-/// Groups every test that constructs a full gateway host via <c>GatewayApplication.Build</c> into a
-/// single, non-parallel xUnit collection.
-///
-/// <para>
-/// The shared <c>ZB.MOM.WW.Telemetry.Serilog</c> bootstrap (<c>AddZbSerilog</c>) installs a global
-/// <see cref="global::Serilog.Log.Logger"/> bootstrap logger on each host build and freezes it during
-/// <c>builder.Build()</c>. That global is process-wide, so two host builds racing in parallel
-/// collections interleave on it and the loser throws "The logger is already frozen." Serializing the
-/// host-building tests (which is the only place a full host is built) removes the race without
-/// changing any production behaviour — the gateway process only ever builds one host.
-/// </para>
-/// </summary>
-[CollectionDefinition(Name, DisableParallelization = true)]
-public sealed class HostBuildingCollection
-{
-    /// <summary>Collection name shared by every host-building test class.</summary>
-    public const string Name = "Gateway host building";
-}
diff --git a/src/ZB.MOM.WW.MxGateway.Tests/Security/Authentication/SqliteAuthStoreTests.cs b/src/ZB.MOM.WW.MxGateway.Tests/Security/Authentication/SqliteAuthStoreTests.cs
index 11e70e0..fd8076d 100644
--- a/src/ZB.MOM.WW.MxGateway.Tests/Security/Authentication/SqliteAuthStoreTests.cs
+++ b/src/ZB.MOM.WW.MxGateway.Tests/Security/Authentication/SqliteAuthStoreTests.cs
@@ -5,14 +5,12 @@ using Microsoft.Extensions.DependencyInjection;
 using ZB.MOM.WW.MxGateway.Server;
 using ZB.MOM.WW.MxGateway.Server.Configuration;
 using ZB.MOM.WW.MxGateway.Server.Security.Authentication;
-using ZB.MOM.WW.MxGateway.Tests.Gateway;
 
 namespace ZB.MOM.WW.MxGateway.Tests.Security.Authentication;
 
 /// <summary>
 /// Tests for <see cref="SqliteAuthStore"/>.
 /// </summary>
-[Collection(HostBuildingCollection.Name)]
 public sealed class SqliteAuthStoreTests : IDisposable
 {
     private readonly List<TempDatabaseDirectory> _tempDirectories = [];