diff --git a/.claude/docs/project-structure.md b/.claude/docs/project-structure.md
index d9042081aa..541a8089e9 100644
--- a/.claude/docs/project-structure.md
+++ b/.claude/docs/project-structure.md
@@ -50,6 +50,24 @@
 | `TUnit.PublicAPI` | Snapshot tests for public API |
 | `TUnit.Templates.Tests` | Template instantiation tests |
 
+## Mocking Framework
+
+| Project | Purpose |
+|---------|---------|
+| `TUnit.Mocks` | Source-generated mocking framework (core runtime: `MockEngine<T>`, `Mock<T>`, setup/verification) |
+| `TUnit.Mocks.SourceGenerator` | Roslyn source generator that emits mock implementations and extension methods |
+| `TUnit.Mocks.SourceGenerator.Roslyn414/44/47` | Roslyn version variants (link source from base generator) |
+| `TUnit.Mocks.Analyzers` | Analyzers for mock usage correctness |
+| `TUnit.Mocks.Assertions` | TUnit assertion integration for mocks |
+| `TUnit.Mocks.Http` | HTTP mocking (`MockHttpHandler`, `MockHttpClient`) |
+| `TUnit.Mocks.Logging` | `ILogger` mocking (`MockLogger`, `MockLogger<T>`) |
+| `TUnit.Mocks.Tests` | Runtime mock tests (672 tests) |
+| `TUnit.Mocks.SourceGenerator.Tests` | Snapshot tests for generated code |
+| `TUnit.Mocks.Analyzers.Tests` | Analyzer tests |
+| `TUnit.Mocks.Http.Tests` | HTTP mock tests |
+| `TUnit.Mocks.Logging.Tests` | Logging mock tests |
+| `TUnit.Mocks.Benchmarks` | BenchmarkDotNet performance comparisons vs Moq/NSubstitute/FakeItEasy |
+
 ## Performance & Benchmarking
 
 | Project | Purpose |
diff --git a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_Inheriting_Multiple_Interfaces.verified.txt b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_Inheriting_Multiple_Interfaces.verified.txt
index aae5a4002c..ef90b8fdde 100644
--- a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_Inheriting_Multiple_Interfaces.verified.txt
+++ b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_Inheriting_Multiple_Interfaces.verified.txt
@@ -1,4 +1,4 @@
-// <auto-generated/>
+// <auto-generated/>
 #nullable enable
 
 namespace TUnit.Mocks.Generated
@@ -30,10 +30,13 @@ namespace TUnit.Mocks.Generated
 
 namespace TUnit.Mocks.Generated
 {
-    internal sealed class IReadWriter_MockImpl : global::IReadWriter, global::TUnit.Mocks.IRaisable
+    internal sealed class IReadWriter_MockImpl : global::IReadWriter, global::TUnit.Mocks.IRaisable, global::TUnit.Mocks.IMockObject
     {
         private readonly global::TUnit.Mocks.MockEngine<global::IReadWriter> _engine;
 
+        [global::System.ComponentModel.EditorBrowsable(global::System.ComponentModel.EditorBrowsableState.Never)]
+        global::TUnit.Mocks.IMock? global::TUnit.Mocks.IMockObject.MockWrapper { get; set; }
+
         internal IReadWriter_MockImpl(global::TUnit.Mocks.MockEngine<global::IReadWriter> engine)
         {
             _engine = engine;
@@ -105,7 +108,9 @@ namespace TUnit.Mocks.Generated
         private readonly int _memberId;
         private readonly string _memberName;
         private readonly global::TUnit.Mocks.Arguments.IArgumentMatcher[] _matchers;
-        private readonly global::System.Lazy<global::TUnit.Mocks.Setup.VoidMethodSetupBuilder> _lazyBuilder;
+        private global::TUnit.Mocks.Setup.VoidMethodSetupBuilder? _builder;
+        private bool _builderInitialized;
+        private object? _builderLock;
 
         internal IReadWriter_Write_M2_MockCall(global::TUnit.Mocks.IMockEngineAccess engine, int memberId, string memberName, global::TUnit.Mocks.Arguments.IArgumentMatcher[] matchers)
         {
@@ -113,17 +118,16 @@ namespace TUnit.Mocks.Generated
             _memberId = memberId;
             _memberName = memberName;
             _matchers = matchers;
-            _lazyBuilder = new global::System.Lazy<global::TUnit.Mocks.Setup.VoidMethodSetupBuilder>(() =>
+            _ = EnsureSetup();
+        }
+
+        private global::TUnit.Mocks.Setup.VoidMethodSetupBuilder EnsureSetup() =>
+            global::System.Threading.LazyInitializer.EnsureInitialized(ref _builder, ref _builderInitialized, ref _builderLock, () =>
             {
                 var setup = new global::TUnit.Mocks.Setup.MethodSetup(_memberId, _matchers, _memberName);
                 _engine.AddSetup(setup);
                 return new global::TUnit.Mocks.Setup.VoidMethodSetupBuilder(setup);
-            }
-            );
-            _ = _lazyBuilder.Value;
-        }
-
-        private global::TUnit.Mocks.Setup.VoidMethodSetupBuilder EnsureSetup() => _lazyBuilder.Value;
+            })!;
 
         /// <inheritdoc />
         public IReadWriter_Write_M2_MockCall Throws<TException>() where TException : global::System.Exception, new() { EnsureSetup().Throws<TException>(); return this; }
diff --git a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Async_Methods.verified.txt b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Async_Methods.verified.txt
index 8df17a1351..6dd209e2bc 100644
--- a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Async_Methods.verified.txt
+++ b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Async_Methods.verified.txt
@@ -1,4 +1,4 @@
-// <auto-generated/>
+// <auto-generated/>
 #nullable enable
 
 namespace TUnit.Mocks.Generated
@@ -30,10 +30,13 @@ namespace TUnit.Mocks.Generated
 
 namespace TUnit.Mocks.Generated
 {
-    internal sealed class IAsyncService_MockImpl : global::IAsyncService, global::TUnit.Mocks.IRaisable
+    internal sealed class IAsyncService_MockImpl : global::IAsyncService, global::TUnit.Mocks.IRaisable, global::TUnit.Mocks.IMockObject
     {
         private readonly global::TUnit.Mocks.MockEngine<global::IAsyncService> _engine;
 
+        [global::System.ComponentModel.EditorBrowsable(global::System.ComponentModel.EditorBrowsableState.Never)]
+        global::TUnit.Mocks.IMock? global::TUnit.Mocks.IMockObject.MockWrapper { get; set; }
+
         internal IAsyncService_MockImpl(global::TUnit.Mocks.MockEngine<global::IAsyncService> engine)
         {
             _engine = engine;
@@ -162,7 +165,9 @@ namespace TUnit.Mocks.Generated
         private readonly int _memberId;
         private readonly string _memberName;
         private readonly global::TUnit.Mocks.Arguments.IArgumentMatcher[] _matchers;
-        private readonly global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<string>> _lazyBuilder;
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string>? _builder;
+        private bool _builderInitialized;
+        private object? _builderLock;
 
         internal IAsyncService_GetValueAsync_M0_MockCall(global::TUnit.Mocks.IMockEngineAccess engine, int memberId, string memberName, global::TUnit.Mocks.Arguments.IArgumentMatcher[] matchers)
         {
@@ -170,16 +175,15 @@ namespace TUnit.Mocks.Generated
             _memberId = memberId;
             _memberName = memberName;
             _matchers = matchers;
-            _lazyBuilder = new global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<string>>(() =>
+        }
+
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string> EnsureSetup() =>
+            global::System.Threading.LazyInitializer.EnsureInitialized(ref _builder, ref _builderInitialized, ref _builderLock, () =>
             {
                 var setup = new global::TUnit.Mocks.Setup.MethodSetup(_memberId, _matchers, _memberName);
                 _engine.AddSetup(setup);
                 return new global::TUnit.Mocks.Setup.MethodSetupBuilder<string>(setup);
-            }
-            );
-        }
-
-        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string> EnsureSetup() => _lazyBuilder.Value;
+            })!;
 
         /// <inheritdoc />
         public IAsyncService_GetValueAsync_M0_MockCall Returns(string value) { EnsureSetup().Returns(value); return this; }
@@ -251,7 +255,9 @@ namespace TUnit.Mocks.Generated
         private readonly int _memberId;
         private readonly string _memberName;
         private readonly global::TUnit.Mocks.Arguments.IArgumentMatcher[] _matchers;
-        private readonly global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<int>> _lazyBuilder;
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<int>? _builder;
+        private bool _builderInitialized;
+        private object? _builderLock;
 
         internal IAsyncService_ComputeAsync_M2_MockCall(global::TUnit.Mocks.IMockEngineAccess engine, int memberId, string memberName, global::TUnit.Mocks.Arguments.IArgumentMatcher[] matchers)
         {
@@ -259,16 +265,15 @@ namespace TUnit.Mocks.Generated
             _memberId = memberId;
             _memberName = memberName;
             _matchers = matchers;
-            _lazyBuilder = new global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<int>>(() =>
+        }
+
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<int> EnsureSetup() =>
+            global::System.Threading.LazyInitializer.EnsureInitialized(ref _builder, ref _builderInitialized, ref _builderLock, () =>
             {
                 var setup = new global::TUnit.Mocks.Setup.MethodSetup(_memberId, _matchers, _memberName);
                 _engine.AddSetup(setup);
                 return new global::TUnit.Mocks.Setup.MethodSetupBuilder<int>(setup);
-            }
-            );
-        }
-
-        private global::TUnit.Mocks.Setup.MethodSetupBuilder<int> EnsureSetup() => _lazyBuilder.Value;
+            })!;
 
         /// <inheritdoc />
         public IAsyncService_ComputeAsync_M2_MockCall Returns(int value) { EnsureSetup().Returns(value); return this; }
@@ -340,7 +345,9 @@ namespace TUnit.Mocks.Generated
         private readonly int _memberId;
         private readonly string _memberName;
         private readonly global::TUnit.Mocks.Arguments.IArgumentMatcher[] _matchers;
-        private readonly global::System.Lazy<global::TUnit.Mocks.Setup.VoidMethodSetupBuilder> _lazyBuilder;
+        private global::TUnit.Mocks.Setup.VoidMethodSetupBuilder? _builder;
+        private bool _builderInitialized;
+        private object? _builderLock;
 
         internal IAsyncService_InitializeAsync_M3_MockCall(global::TUnit.Mocks.IMockEngineAccess engine, int memberId, string memberName, global::TUnit.Mocks.Arguments.IArgumentMatcher[] matchers)
         {
@@ -348,17 +355,16 @@ namespace TUnit.Mocks.Generated
             _memberId = memberId;
             _memberName = memberName;
             _matchers = matchers;
-            _lazyBuilder = new global::System.Lazy<global::TUnit.Mocks.Setup.VoidMethodSetupBuilder>(() =>
+            _ = EnsureSetup();
+        }
+
+        private global::TUnit.Mocks.Setup.VoidMethodSetupBuilder EnsureSetup() =>
+            global::System.Threading.LazyInitializer.EnsureInitialized(ref _builder, ref _builderInitialized, ref _builderLock, () =>
             {
                 var setup = new global::TUnit.Mocks.Setup.MethodSetup(_memberId, _matchers, _memberName);
                 _engine.AddSetup(setup);
                 return new global::TUnit.Mocks.Setup.VoidMethodSetupBuilder(setup);
-            }
-            );
-            _ = _lazyBuilder.Value;
-        }
-
-        private global::TUnit.Mocks.Setup.VoidMethodSetupBuilder EnsureSetup() => _lazyBuilder.Value;
+            })!;
 
         /// <inheritdoc />
         public IAsyncService_InitializeAsync_M3_MockCall Throws<TException>() where TException : global::System.Exception, new() { EnsureSetup().Throws<TException>(); return this; }
diff --git a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Events.verified.txt b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Events.verified.txt
index 7040397997..9b5534c09c 100644
--- a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Events.verified.txt
+++ b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Events.verified.txt
@@ -1,4 +1,4 @@
-// <auto-generated/>
+// <auto-generated/>
 #nullable enable
 
 namespace TUnit.Mocks.Generated
@@ -61,10 +61,13 @@ namespace TUnit.Mocks.Generated
 
 namespace TUnit.Mocks.Generated
 {
-    internal sealed class INotifier_MockImpl : global::INotifier, global::TUnit.Mocks.IRaisable
+    internal sealed class INotifier_MockImpl : global::INotifier, global::TUnit.Mocks.IRaisable, global::TUnit.Mocks.IMockObject
     {
         private readonly global::TUnit.Mocks.MockEngine<global::INotifier> _engine;
 
+        [global::System.ComponentModel.EditorBrowsable(global::System.ComponentModel.EditorBrowsableState.Never)]
+        global::TUnit.Mocks.IMock? global::TUnit.Mocks.IMockObject.MockWrapper { get; set; }
+
         internal INotifier_MockImpl(global::TUnit.Mocks.MockEngine<global::INotifier> engine)
         {
             _engine = engine;
@@ -140,7 +143,9 @@ namespace TUnit.Mocks.Generated
         private readonly int _memberId;
         private readonly string _memberName;
         private readonly global::TUnit.Mocks.Arguments.IArgumentMatcher[] _matchers;
-        private readonly global::System.Lazy<global::TUnit.Mocks.Setup.VoidMethodSetupBuilder> _lazyBuilder;
+        private global::TUnit.Mocks.Setup.VoidMethodSetupBuilder? _builder;
+        private bool _builderInitialized;
+        private object? _builderLock;
 
         internal INotifier_Notify_M0_MockCall(global::TUnit.Mocks.IMockEngineAccess engine, int memberId, string memberName, global::TUnit.Mocks.Arguments.IArgumentMatcher[] matchers)
         {
@@ -148,17 +153,16 @@ namespace TUnit.Mocks.Generated
             _memberId = memberId;
             _memberName = memberName;
             _matchers = matchers;
-            _lazyBuilder = new global::System.Lazy<global::TUnit.Mocks.Setup.VoidMethodSetupBuilder>(() =>
+            _ = EnsureSetup();
+        }
+
+        private global::TUnit.Mocks.Setup.VoidMethodSetupBuilder EnsureSetup() =>
+            global::System.Threading.LazyInitializer.EnsureInitialized(ref _builder, ref _builderInitialized, ref _builderLock, () =>
             {
                 var setup = new global::TUnit.Mocks.Setup.MethodSetup(_memberId, _matchers, _memberName);
                 _engine.AddSetup(setup);
                 return new global::TUnit.Mocks.Setup.VoidMethodSetupBuilder(setup);
-            }
-            );
-            _ = _lazyBuilder.Value;
-        }
-
-        private global::TUnit.Mocks.Setup.VoidMethodSetupBuilder EnsureSetup() => _lazyBuilder.Value;
+            })!;
 
         /// <inheritdoc />
         public INotifier_Notify_M0_MockCall Throws<TException>() where TException : global::System.Exception, new() { EnsureSetup().Throws<TException>(); return this; }
diff --git a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Generic_Methods.verified.txt b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Generic_Methods.verified.txt
index 68f87ae580..34307f8987 100644
--- a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Generic_Methods.verified.txt
+++ b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Generic_Methods.verified.txt
@@ -30,10 +30,13 @@ namespace TUnit.Mocks.Generated
 
 namespace TUnit.Mocks.Generated
 {
-    internal sealed class IRepository_MockImpl : global::IRepository, global::TUnit.Mocks.IRaisable
+    internal sealed class IRepository_MockImpl : global::IRepository, global::TUnit.Mocks.IRaisable, global::TUnit.Mocks.IMockObject
     {
         private readonly global::TUnit.Mocks.MockEngine<global::IRepository> _engine;
 
+        [global::System.ComponentModel.EditorBrowsable(global::System.ComponentModel.EditorBrowsableState.Never)]
+        global::TUnit.Mocks.IMock? global::TUnit.Mocks.IMockObject.MockWrapper { get; set; }
+
         internal IRepository_MockImpl(global::TUnit.Mocks.MockEngine<global::IRepository> engine)
         {
             _engine = engine;
diff --git a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Inherited_Static_Abstract_Members.verified.txt b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Inherited_Static_Abstract_Members.verified.txt
index dc8c623623..60df228ce1 100644
--- a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Inherited_Static_Abstract_Members.verified.txt
+++ b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Inherited_Static_Abstract_Members.verified.txt
@@ -63,10 +63,13 @@ namespace TUnit.Mocks.Generated
 
 namespace TUnit.Mocks.Generated
 {
-    internal sealed class IMyService_MockImpl : global::TUnit.Mocks.Generated.IMyService_Mockable, global::TUnit.Mocks.IRaisable
+    internal sealed class IMyService_MockImpl : global::TUnit.Mocks.Generated.IMyService_Mockable, global::TUnit.Mocks.IRaisable, global::TUnit.Mocks.IMockObject
     {
         private readonly global::TUnit.Mocks.MockEngine<global::TUnit.Mocks.Generated.IMyService_Mockable> _engine;
 
+        [global::System.ComponentModel.EditorBrowsable(global::System.ComponentModel.EditorBrowsableState.Never)]
+        global::TUnit.Mocks.IMock? global::TUnit.Mocks.IMockObject.MockWrapper { get; set; }
+
         internal IMyService_MockImpl(global::TUnit.Mocks.MockEngine<global::TUnit.Mocks.Generated.IMyService_Mockable> engine)
         {
             _engine = engine;
diff --git a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Keyword_Parameter_Names.verified.txt b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Keyword_Parameter_Names.verified.txt
index ccc0455c03..8851539fb3 100644
--- a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Keyword_Parameter_Names.verified.txt
+++ b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Keyword_Parameter_Names.verified.txt
@@ -1,4 +1,4 @@
-// <auto-generated/>
+// <auto-generated/>
 #nullable enable
 
 namespace TUnit.Mocks.Generated
@@ -30,10 +30,13 @@ namespace TUnit.Mocks.Generated
 
 namespace TUnit.Mocks.Generated
 {
-    internal sealed class ITest_MockImpl : global::ITest, global::TUnit.Mocks.IRaisable
+    internal sealed class ITest_MockImpl : global::ITest, global::TUnit.Mocks.IRaisable, global::TUnit.Mocks.IMockObject
     {
         private readonly global::TUnit.Mocks.MockEngine<global::ITest> _engine;
 
+        [global::System.ComponentModel.EditorBrowsable(global::System.ComponentModel.EditorBrowsableState.Never)]
+        global::TUnit.Mocks.IMock? global::TUnit.Mocks.IMockObject.MockWrapper { get; set; }
+
         internal ITest_MockImpl(global::TUnit.Mocks.MockEngine<global::ITest> engine)
         {
             _engine = engine;
@@ -116,7 +119,9 @@ namespace TUnit.Mocks.Generated
         private readonly int _memberId;
         private readonly string _memberName;
         private readonly global::TUnit.Mocks.Arguments.IArgumentMatcher[] _matchers;
-        private readonly global::System.Lazy<global::TUnit.Mocks.Setup.VoidMethodSetupBuilder> _lazyBuilder;
+        private global::TUnit.Mocks.Setup.VoidMethodSetupBuilder? _builder;
+        private bool _builderInitialized;
+        private object? _builderLock;
 
         internal ITest_Test_M0_MockCall(global::TUnit.Mocks.IMockEngineAccess engine, int memberId, string memberName, global::TUnit.Mocks.Arguments.IArgumentMatcher[] matchers)
         {
@@ -124,17 +129,16 @@ namespace TUnit.Mocks.Generated
             _memberId = memberId;
             _memberName = memberName;
             _matchers = matchers;
-            _lazyBuilder = new global::System.Lazy<global::TUnit.Mocks.Setup.VoidMethodSetupBuilder>(() =>
+            _ = EnsureSetup();
+        }
+
+        private global::TUnit.Mocks.Setup.VoidMethodSetupBuilder EnsureSetup() =>
+            global::System.Threading.LazyInitializer.EnsureInitialized(ref _builder, ref _builderInitialized, ref _builderLock, () =>
             {
                 var setup = new global::TUnit.Mocks.Setup.MethodSetup(_memberId, _matchers, _memberName);
                 _engine.AddSetup(setup);
                 return new global::TUnit.Mocks.Setup.VoidMethodSetupBuilder(setup);
-            }
-            );
-            _ = _lazyBuilder.Value;
-        }
-
-        private global::TUnit.Mocks.Setup.VoidMethodSetupBuilder EnsureSetup() => _lazyBuilder.Value;
+            })!;
 
         /// <inheritdoc />
         public ITest_Test_M0_MockCall Throws<TException>() where TException : global::System.Exception, new() { EnsureSetup().Throws<TException>(); return this; }
@@ -191,7 +195,9 @@ namespace TUnit.Mocks.Generated
         private readonly int _memberId;
         private readonly string _memberName;
         private readonly global::TUnit.Mocks.Arguments.IArgumentMatcher[] _matchers;
-        private readonly global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<string>> _lazyBuilder;
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string>? _builder;
+        private bool _builderInitialized;
+        private object? _builderLock;
 
         internal ITest_Get_M1_MockCall(global::TUnit.Mocks.IMockEngineAccess engine, int memberId, string memberName, global::TUnit.Mocks.Arguments.IArgumentMatcher[] matchers)
         {
@@ -199,16 +205,15 @@ namespace TUnit.Mocks.Generated
             _memberId = memberId;
             _memberName = memberName;
             _matchers = matchers;
-            _lazyBuilder = new global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<string>>(() =>
+        }
+
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string> EnsureSetup() =>
+            global::System.Threading.LazyInitializer.EnsureInitialized(ref _builder, ref _builderInitialized, ref _builderLock, () =>
             {
                 var setup = new global::TUnit.Mocks.Setup.MethodSetup(_memberId, _matchers, _memberName);
                 _engine.AddSetup(setup);
                 return new global::TUnit.Mocks.Setup.MethodSetupBuilder<string>(setup);
-            }
-            );
-        }
-
-        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string> EnsureSetup() => _lazyBuilder.Value;
+            })!;
 
         /// <inheritdoc />
         public ITest_Get_M1_MockCall Returns(string value) { EnsureSetup().Returns(value); return this; }
diff --git a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Mixed_Members.verified.txt b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Mixed_Members.verified.txt
index 4b83f966ab..8e56e6d8d4 100644
--- a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Mixed_Members.verified.txt
+++ b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Mixed_Members.verified.txt
@@ -1,4 +1,4 @@
-// <auto-generated/>
+// <auto-generated/>
 #nullable enable
 
 namespace TUnit.Mocks.Generated
@@ -61,10 +61,13 @@ namespace TUnit.Mocks.Generated
 
 namespace TUnit.Mocks.Generated
 {
-    internal sealed class IService_MockImpl : global::IService, global::TUnit.Mocks.IRaisable
+    internal sealed class IService_MockImpl : global::IService, global::TUnit.Mocks.IRaisable, global::TUnit.Mocks.IMockObject
     {
         private readonly global::TUnit.Mocks.MockEngine<global::IService> _engine;
 
+        [global::System.ComponentModel.EditorBrowsable(global::System.ComponentModel.EditorBrowsableState.Never)]
+        global::TUnit.Mocks.IMock? global::TUnit.Mocks.IMockObject.MockWrapper { get; set; }
+
         internal IService_MockImpl(global::TUnit.Mocks.MockEngine<global::IService> engine)
         {
             _engine = engine;
@@ -186,7 +189,9 @@ namespace TUnit.Mocks.Generated
         private readonly int _memberId;
         private readonly string _memberName;
         private readonly global::TUnit.Mocks.Arguments.IArgumentMatcher[] _matchers;
-        private readonly global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<string>> _lazyBuilder;
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string>? _builder;
+        private bool _builderInitialized;
+        private object? _builderLock;
 
         internal IService_GetAsync_M3_MockCall(global::TUnit.Mocks.IMockEngineAccess engine, int memberId, string memberName, global::TUnit.Mocks.Arguments.IArgumentMatcher[] matchers)
         {
@@ -194,16 +199,15 @@ namespace TUnit.Mocks.Generated
             _memberId = memberId;
             _memberName = memberName;
             _matchers = matchers;
-            _lazyBuilder = new global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<string>>(() =>
+        }
+
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string> EnsureSetup() =>
+            global::System.Threading.LazyInitializer.EnsureInitialized(ref _builder, ref _builderInitialized, ref _builderLock, () =>
             {
                 var setup = new global::TUnit.Mocks.Setup.MethodSetup(_memberId, _matchers, _memberName);
                 _engine.AddSetup(setup);
                 return new global::TUnit.Mocks.Setup.MethodSetupBuilder<string>(setup);
-            }
-            );
-        }
-
-        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string> EnsureSetup() => _lazyBuilder.Value;
+            })!;
 
         /// <inheritdoc />
         public IService_GetAsync_M3_MockCall Returns(string value) { EnsureSetup().Returns(value); return this; }
@@ -278,7 +282,9 @@ namespace TUnit.Mocks.Generated
         private readonly int _memberId;
         private readonly string _memberName;
         private readonly global::TUnit.Mocks.Arguments.IArgumentMatcher[] _matchers;
-        private readonly global::System.Lazy<global::TUnit.Mocks.Setup.VoidMethodSetupBuilder> _lazyBuilder;
+        private global::TUnit.Mocks.Setup.VoidMethodSetupBuilder? _builder;
+        private bool _builderInitialized;
+        private object? _builderLock;
 
         internal IService_Process_M4_MockCall(global::TUnit.Mocks.IMockEngineAccess engine, int memberId, string memberName, global::TUnit.Mocks.Arguments.IArgumentMatcher[] matchers)
         {
@@ -286,17 +292,16 @@ namespace TUnit.Mocks.Generated
             _memberId = memberId;
             _memberName = memberName;
             _matchers = matchers;
-            _lazyBuilder = new global::System.Lazy<global::TUnit.Mocks.Setup.VoidMethodSetupBuilder>(() =>
+            _ = EnsureSetup();
+        }
+
+        private global::TUnit.Mocks.Setup.VoidMethodSetupBuilder EnsureSetup() =>
+            global::System.Threading.LazyInitializer.EnsureInitialized(ref _builder, ref _builderInitialized, ref _builderLock, () =>
             {
                 var setup = new global::TUnit.Mocks.Setup.MethodSetup(_memberId, _matchers, _memberName);
                 _engine.AddSetup(setup);
                 return new global::TUnit.Mocks.Setup.VoidMethodSetupBuilder(setup);
-            }
-            );
-            _ = _lazyBuilder.Value;
-        }
-
-        private global::TUnit.Mocks.Setup.VoidMethodSetupBuilder EnsureSetup() => _lazyBuilder.Value;
+            })!;
 
         /// <inheritdoc />
         public IService_Process_M4_MockCall Throws<TException>() where TException : global::System.Exception, new() { EnsureSetup().Throws<TException>(); return this; }
diff --git a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Nullable_Reference_Type_Parameters.verified.txt b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Nullable_Reference_Type_Parameters.verified.txt
index 94d54e07ad..c55ec140c1 100644
--- a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Nullable_Reference_Type_Parameters.verified.txt
+++ b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Nullable_Reference_Type_Parameters.verified.txt
@@ -1,4 +1,4 @@
-// <auto-generated/>
+// <auto-generated/>
 #nullable enable
 
 namespace TUnit.Mocks.Generated
@@ -30,10 +30,13 @@ namespace TUnit.Mocks.Generated
 
 namespace TUnit.Mocks.Generated
 {
-    internal sealed class IFoo_MockImpl : global::IFoo, global::TUnit.Mocks.IRaisable
+    internal sealed class IFoo_MockImpl : global::IFoo, global::TUnit.Mocks.IRaisable, global::TUnit.Mocks.IMockObject
     {
         private readonly global::TUnit.Mocks.MockEngine<global::IFoo> _engine;
 
+        [global::System.ComponentModel.EditorBrowsable(global::System.ComponentModel.EditorBrowsableState.Never)]
+        global::TUnit.Mocks.IMock? global::TUnit.Mocks.IMockObject.MockWrapper { get; set; }
+
         internal IFoo_MockImpl(global::TUnit.Mocks.MockEngine<global::IFoo> engine)
         {
             _engine = engine;
@@ -219,7 +222,9 @@ namespace TUnit.Mocks.Generated
         private readonly int _memberId;
         private readonly string _memberName;
         private readonly global::TUnit.Mocks.Arguments.IArgumentMatcher[] _matchers;
-        private readonly global::System.Lazy<global::TUnit.Mocks.Setup.VoidMethodSetupBuilder> _lazyBuilder;
+        private global::TUnit.Mocks.Setup.VoidMethodSetupBuilder? _builder;
+        private bool _builderInitialized;
+        private object? _builderLock;
 
         internal IFoo_Bar_M0_MockCall(global::TUnit.Mocks.IMockEngineAccess engine, int memberId, string memberName, global::TUnit.Mocks.Arguments.IArgumentMatcher[] matchers)
         {
@@ -227,17 +232,16 @@ namespace TUnit.Mocks.Generated
             _memberId = memberId;
             _memberName = memberName;
             _matchers = matchers;
-            _lazyBuilder = new global::System.Lazy<global::TUnit.Mocks.Setup.VoidMethodSetupBuilder>(() =>
+            _ = EnsureSetup();
+        }
+
+        private global::TUnit.Mocks.Setup.VoidMethodSetupBuilder EnsureSetup() =>
+            global::System.Threading.LazyInitializer.EnsureInitialized(ref _builder, ref _builderInitialized, ref _builderLock, () =>
             {
                 var setup = new global::TUnit.Mocks.Setup.MethodSetup(_memberId, _matchers, _memberName);
                 _engine.AddSetup(setup);
                 return new global::TUnit.Mocks.Setup.VoidMethodSetupBuilder(setup);
-            }
-            );
-            _ = _lazyBuilder.Value;
-        }
-
-        private global::TUnit.Mocks.Setup.VoidMethodSetupBuilder EnsureSetup() => _lazyBuilder.Value;
+            })!;
 
         /// <inheritdoc />
         public IFoo_Bar_M0_MockCall Throws<TException>() where TException : global::System.Exception, new() { EnsureSetup().Throws<TException>(); return this; }
@@ -294,7 +298,9 @@ namespace TUnit.Mocks.Generated
         private readonly int _memberId;
         private readonly string _memberName;
         private readonly global::TUnit.Mocks.Arguments.IArgumentMatcher[] _matchers;
-        private readonly global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<string?>> _lazyBuilder;
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string?>? _builder;
+        private bool _builderInitialized;
+        private object? _builderLock;
 
         internal IFoo_GetValue_M1_MockCall(global::TUnit.Mocks.IMockEngineAccess engine, int memberId, string memberName, global::TUnit.Mocks.Arguments.IArgumentMatcher[] matchers)
         {
@@ -302,16 +308,15 @@ namespace TUnit.Mocks.Generated
             _memberId = memberId;
             _memberName = memberName;
             _matchers = matchers;
-            _lazyBuilder = new global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<string?>>(() =>
+        }
+
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string?> EnsureSetup() =>
+            global::System.Threading.LazyInitializer.EnsureInitialized(ref _builder, ref _builderInitialized, ref _builderLock, () =>
             {
                 var setup = new global::TUnit.Mocks.Setup.MethodSetup(_memberId, _matchers, _memberName);
                 _engine.AddSetup(setup);
                 return new global::TUnit.Mocks.Setup.MethodSetupBuilder<string?>(setup);
-            }
-            );
-        }
-
-        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string?> EnsureSetup() => _lazyBuilder.Value;
+            })!;
 
         /// <inheritdoc />
         public IFoo_GetValue_M1_MockCall Returns(string? value) { EnsureSetup().Returns(value); return this; }
@@ -383,7 +388,9 @@ namespace TUnit.Mocks.Generated
         private readonly int _memberId;
         private readonly string _memberName;
         private readonly global::TUnit.Mocks.Arguments.IArgumentMatcher[] _matchers;
-        private readonly global::System.Lazy<global::TUnit.Mocks.Setup.VoidMethodSetupBuilder> _lazyBuilder;
+        private global::TUnit.Mocks.Setup.VoidMethodSetupBuilder? _builder;
+        private bool _builderInitialized;
+        private object? _builderLock;
 
         internal IFoo_Process_M2_MockCall(global::TUnit.Mocks.IMockEngineAccess engine, int memberId, string memberName, global::TUnit.Mocks.Arguments.IArgumentMatcher[] matchers)
         {
@@ -391,17 +398,16 @@ namespace TUnit.Mocks.Generated
             _memberId = memberId;
             _memberName = memberName;
             _matchers = matchers;
-            _lazyBuilder = new global::System.Lazy<global::TUnit.Mocks.Setup.VoidMethodSetupBuilder>(() =>
+            _ = EnsureSetup();
+        }
+
+        private global::TUnit.Mocks.Setup.VoidMethodSetupBuilder EnsureSetup() =>
+            global::System.Threading.LazyInitializer.EnsureInitialized(ref _builder, ref _builderInitialized, ref _builderLock, () =>
             {
                 var setup = new global::TUnit.Mocks.Setup.MethodSetup(_memberId, _matchers, _memberName);
                 _engine.AddSetup(setup);
                 return new global::TUnit.Mocks.Setup.VoidMethodSetupBuilder(setup);
-            }
-            );
-            _ = _lazyBuilder.Value;
-        }
-
-        private global::TUnit.Mocks.Setup.VoidMethodSetupBuilder EnsureSetup() => _lazyBuilder.Value;
+            })!;
 
         /// <inheritdoc />
         public IFoo_Process_M2_MockCall Throws<TException>() where TException : global::System.Exception, new() { EnsureSetup().Throws<TException>(); return this; }
@@ -458,7 +464,9 @@ namespace TUnit.Mocks.Generated
         private readonly int _memberId;
         private readonly string _memberName;
         private readonly global::TUnit.Mocks.Arguments.IArgumentMatcher[] _matchers;
-        private readonly global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<string?>> _lazyBuilder;
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string?>? _builder;
+        private bool _builderInitialized;
+        private object? _builderLock;
 
         internal IFoo_GetAsync_M3_MockCall(global::TUnit.Mocks.IMockEngineAccess engine, int memberId, string memberName, global::TUnit.Mocks.Arguments.IArgumentMatcher[] matchers)
         {
@@ -466,16 +474,15 @@ namespace TUnit.Mocks.Generated
             _memberId = memberId;
             _memberName = memberName;
             _matchers = matchers;
-            _lazyBuilder = new global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<string?>>(() =>
+        }
+
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string?> EnsureSetup() =>
+            global::System.Threading.LazyInitializer.EnsureInitialized(ref _builder, ref _builderInitialized, ref _builderLock, () =>
             {
                 var setup = new global::TUnit.Mocks.Setup.MethodSetup(_memberId, _matchers, _memberName);
                 _engine.AddSetup(setup);
                 return new global::TUnit.Mocks.Setup.MethodSetupBuilder<string?>(setup);
-            }
-            );
-        }
-
-        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string?> EnsureSetup() => _lazyBuilder.Value;
+            })!;
 
         /// <inheritdoc />
         public IFoo_GetAsync_M3_MockCall Returns(string? value) { EnsureSetup().Returns(value); return this; }
diff --git a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Out_Ref_Parameters.verified.txt b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Out_Ref_Parameters.verified.txt
index fdb45bb5ea..c2d2bbb4fe 100644
--- a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Out_Ref_Parameters.verified.txt
+++ b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Out_Ref_Parameters.verified.txt
@@ -1,4 +1,4 @@
-// <auto-generated/>
+// <auto-generated/>
 #nullable enable
 
 namespace TUnit.Mocks.Generated
@@ -30,10 +30,13 @@ namespace TUnit.Mocks.Generated
 
 namespace TUnit.Mocks.Generated
 {
-    internal sealed class IDictionary_MockImpl : global::IDictionary, global::TUnit.Mocks.IRaisable
+    internal sealed class IDictionary_MockImpl : global::IDictionary, global::TUnit.Mocks.IRaisable, global::TUnit.Mocks.IMockObject
     {
         private readonly global::TUnit.Mocks.MockEngine<global::IDictionary> _engine;
 
+        [global::System.ComponentModel.EditorBrowsable(global::System.ComponentModel.EditorBrowsableState.Never)]
+        global::TUnit.Mocks.IMock? global::TUnit.Mocks.IMockObject.MockWrapper { get; set; }
+
         internal IDictionary_MockImpl(global::TUnit.Mocks.MockEngine<global::IDictionary> engine)
         {
             _engine = engine;
@@ -107,7 +110,9 @@ namespace TUnit.Mocks.Generated
         private readonly int _memberId;
         private readonly string _memberName;
         private readonly global::TUnit.Mocks.Arguments.IArgumentMatcher[] _matchers;
-        private readonly global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<bool>> _lazyBuilder;
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<bool>? _builder;
+        private bool _builderInitialized;
+        private object? _builderLock;
 
         internal IDictionary_TryGetValue_M0_MockCall(global::TUnit.Mocks.IMockEngineAccess engine, int memberId, string memberName, global::TUnit.Mocks.Arguments.IArgumentMatcher[] matchers)
         {
@@ -115,16 +120,15 @@ namespace TUnit.Mocks.Generated
             _memberId = memberId;
             _memberName = memberName;
             _matchers = matchers;
-            _lazyBuilder = new global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<bool>>(() =>
+        }
+
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<bool> EnsureSetup() =>
+            global::System.Threading.LazyInitializer.EnsureInitialized(ref _builder, ref _builderInitialized, ref _builderLock, () =>
             {
                 var setup = new global::TUnit.Mocks.Setup.MethodSetup(_memberId, _matchers, _memberName);
                 _engine.AddSetup(setup);
                 return new global::TUnit.Mocks.Setup.MethodSetupBuilder<bool>(setup);
-            }
-            );
-        }
-
-        private global::TUnit.Mocks.Setup.MethodSetupBuilder<bool> EnsureSetup() => _lazyBuilder.Value;
+            })!;
 
         /// <inheritdoc />
         public IDictionary_TryGetValue_M0_MockCall Returns(bool value) { EnsureSetup().Returns(value); return this; }
@@ -200,7 +204,9 @@ namespace TUnit.Mocks.Generated
         private readonly int _memberId;
         private readonly string _memberName;
         private readonly global::TUnit.Mocks.Arguments.IArgumentMatcher[] _matchers;
-        private readonly global::System.Lazy<global::TUnit.Mocks.Setup.VoidMethodSetupBuilder> _lazyBuilder;
+        private global::TUnit.Mocks.Setup.VoidMethodSetupBuilder? _builder;
+        private bool _builderInitialized;
+        private object? _builderLock;
 
         internal IDictionary_Swap_M1_MockCall(global::TUnit.Mocks.IMockEngineAccess engine, int memberId, string memberName, global::TUnit.Mocks.Arguments.IArgumentMatcher[] matchers)
         {
@@ -208,17 +214,16 @@ namespace TUnit.Mocks.Generated
             _memberId = memberId;
             _memberName = memberName;
             _matchers = matchers;
-            _lazyBuilder = new global::System.Lazy<global::TUnit.Mocks.Setup.VoidMethodSetupBuilder>(() =>
+            _ = EnsureSetup();
+        }
+
+        private global::TUnit.Mocks.Setup.VoidMethodSetupBuilder EnsureSetup() =>
+            global::System.Threading.LazyInitializer.EnsureInitialized(ref _builder, ref _builderInitialized, ref _builderLock, () =>
             {
                 var setup = new global::TUnit.Mocks.Setup.MethodSetup(_memberId, _matchers, _memberName);
                 _engine.AddSetup(setup);
                 return new global::TUnit.Mocks.Setup.VoidMethodSetupBuilder(setup);
-            }
-            );
-            _ = _lazyBuilder.Value;
-        }
-
-        private global::TUnit.Mocks.Setup.VoidMethodSetupBuilder EnsureSetup() => _lazyBuilder.Value;
+            })!;
 
         /// <inheritdoc />
         public IDictionary_Swap_M1_MockCall Throws<TException>() where TException : global::System.Exception, new() { EnsureSetup().Throws<TException>(); return this; }
diff --git a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Overloaded_Methods.verified.txt b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Overloaded_Methods.verified.txt
index cc74b2811e..7198477d00 100644
--- a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Overloaded_Methods.verified.txt
+++ b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Overloaded_Methods.verified.txt
@@ -1,4 +1,4 @@
-// <auto-generated/>
+// <auto-generated/>
 #nullable enable
 
 namespace TUnit.Mocks.Generated
@@ -30,10 +30,13 @@ namespace TUnit.Mocks.Generated
 
 namespace TUnit.Mocks.Generated
 {
-    internal sealed class IFormatter_MockImpl : global::IFormatter, global::TUnit.Mocks.IRaisable
+    internal sealed class IFormatter_MockImpl : global::IFormatter, global::TUnit.Mocks.IRaisable, global::TUnit.Mocks.IMockObject
     {
         private readonly global::TUnit.Mocks.MockEngine<global::IFormatter> _engine;
 
+        [global::System.ComponentModel.EditorBrowsable(global::System.ComponentModel.EditorBrowsableState.Never)]
+        global::TUnit.Mocks.IMock? global::TUnit.Mocks.IMockObject.MockWrapper { get; set; }
+
         internal IFormatter_MockImpl(global::TUnit.Mocks.MockEngine<global::IFormatter> engine)
         {
             _engine = engine;
@@ -199,7 +202,9 @@ namespace TUnit.Mocks.Generated
         private readonly int _memberId;
         private readonly string _memberName;
         private readonly global::TUnit.Mocks.Arguments.IArgumentMatcher[] _matchers;
-        private readonly global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<string>> _lazyBuilder;
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string>? _builder;
+        private bool _builderInitialized;
+        private object? _builderLock;
 
         internal IFormatter_Format_M0_MockCall(global::TUnit.Mocks.IMockEngineAccess engine, int memberId, string memberName, global::TUnit.Mocks.Arguments.IArgumentMatcher[] matchers)
         {
@@ -207,16 +212,15 @@ namespace TUnit.Mocks.Generated
             _memberId = memberId;
             _memberName = memberName;
             _matchers = matchers;
-            _lazyBuilder = new global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<string>>(() =>
+        }
+
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string> EnsureSetup() =>
+            global::System.Threading.LazyInitializer.EnsureInitialized(ref _builder, ref _builderInitialized, ref _builderLock, () =>
             {
                 var setup = new global::TUnit.Mocks.Setup.MethodSetup(_memberId, _matchers, _memberName);
                 _engine.AddSetup(setup);
                 return new global::TUnit.Mocks.Setup.MethodSetupBuilder<string>(setup);
-            }
-            );
-        }
-
-        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string> EnsureSetup() => _lazyBuilder.Value;
+            })!;
 
         /// <inheritdoc />
         public IFormatter_Format_M0_MockCall Returns(string value) { EnsureSetup().Returns(value); return this; }
@@ -288,7 +292,9 @@ namespace TUnit.Mocks.Generated
         private readonly int _memberId;
         private readonly string _memberName;
         private readonly global::TUnit.Mocks.Arguments.IArgumentMatcher[] _matchers;
-        private readonly global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<string>> _lazyBuilder;
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string>? _builder;
+        private bool _builderInitialized;
+        private object? _builderLock;
 
         internal IFormatter_Format_M1_MockCall(global::TUnit.Mocks.IMockEngineAccess engine, int memberId, string memberName, global::TUnit.Mocks.Arguments.IArgumentMatcher[] matchers)
         {
@@ -296,16 +302,15 @@ namespace TUnit.Mocks.Generated
             _memberId = memberId;
             _memberName = memberName;
             _matchers = matchers;
-            _lazyBuilder = new global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<string>>(() =>
+        }
+
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string> EnsureSetup() =>
+            global::System.Threading.LazyInitializer.EnsureInitialized(ref _builder, ref _builderInitialized, ref _builderLock, () =>
             {
                 var setup = new global::TUnit.Mocks.Setup.MethodSetup(_memberId, _matchers, _memberName);
                 _engine.AddSetup(setup);
                 return new global::TUnit.Mocks.Setup.MethodSetupBuilder<string>(setup);
-            }
-            );
-        }
-
-        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string> EnsureSetup() => _lazyBuilder.Value;
+            })!;
 
         /// <inheritdoc />
         public IFormatter_Format_M1_MockCall Returns(string value) { EnsureSetup().Returns(value); return this; }
@@ -377,7 +382,9 @@ namespace TUnit.Mocks.Generated
         private readonly int _memberId;
         private readonly string _memberName;
         private readonly global::TUnit.Mocks.Arguments.IArgumentMatcher[] _matchers;
-        private readonly global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<string>> _lazyBuilder;
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string>? _builder;
+        private bool _builderInitialized;
+        private object? _builderLock;
 
         internal IFormatter_Format_M2_MockCall(global::TUnit.Mocks.IMockEngineAccess engine, int memberId, string memberName, global::TUnit.Mocks.Arguments.IArgumentMatcher[] matchers)
         {
@@ -385,16 +392,15 @@ namespace TUnit.Mocks.Generated
             _memberId = memberId;
             _memberName = memberName;
             _matchers = matchers;
-            _lazyBuilder = new global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<string>>(() =>
+        }
+
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string> EnsureSetup() =>
+            global::System.Threading.LazyInitializer.EnsureInitialized(ref _builder, ref _builderInitialized, ref _builderLock, () =>
             {
                 var setup = new global::TUnit.Mocks.Setup.MethodSetup(_memberId, _matchers, _memberName);
                 _engine.AddSetup(setup);
                 return new global::TUnit.Mocks.Setup.MethodSetupBuilder<string>(setup);
-            }
-            );
-        }
-
-        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string> EnsureSetup() => _lazyBuilder.Value;
+            })!;
 
         /// <inheritdoc />
         public IFormatter_Format_M2_MockCall Returns(string value) { EnsureSetup().Returns(value); return this; }
@@ -466,7 +472,9 @@ namespace TUnit.Mocks.Generated
         private readonly int _memberId;
         private readonly string _memberName;
         private readonly global::TUnit.Mocks.Arguments.IArgumentMatcher[] _matchers;
-        private readonly global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<string>> _lazyBuilder;
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string>? _builder;
+        private bool _builderInitialized;
+        private object? _builderLock;
 
         internal IFormatter_Format_M3_MockCall(global::TUnit.Mocks.IMockEngineAccess engine, int memberId, string memberName, global::TUnit.Mocks.Arguments.IArgumentMatcher[] matchers)
         {
@@ -474,16 +482,15 @@ namespace TUnit.Mocks.Generated
             _memberId = memberId;
             _memberName = memberName;
             _matchers = matchers;
-            _lazyBuilder = new global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<string>>(() =>
+        }
+
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string> EnsureSetup() =>
+            global::System.Threading.LazyInitializer.EnsureInitialized(ref _builder, ref _builderInitialized, ref _builderLock, () =>
             {
                 var setup = new global::TUnit.Mocks.Setup.MethodSetup(_memberId, _matchers, _memberName);
                 _engine.AddSetup(setup);
                 return new global::TUnit.Mocks.Setup.MethodSetupBuilder<string>(setup);
-            }
-            );
-        }
-
-        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string> EnsureSetup() => _lazyBuilder.Value;
+            })!;
 
         /// <inheritdoc />
         public IFormatter_Format_M3_MockCall Returns(string value) { EnsureSetup().Returns(value); return this; }
diff --git a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Properties.verified.txt b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Properties.verified.txt
index 75d2bee750..1408e0e6d0 100644
--- a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Properties.verified.txt
+++ b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Properties.verified.txt
@@ -30,10 +30,13 @@ namespace TUnit.Mocks.Generated
 
 namespace TUnit.Mocks.Generated
 {
-    internal sealed class IRepository_MockImpl : global::IRepository, global::TUnit.Mocks.IRaisable
+    internal sealed class IRepository_MockImpl : global::IRepository, global::TUnit.Mocks.IRaisable, global::TUnit.Mocks.IMockObject
     {
         private readonly global::TUnit.Mocks.MockEngine<global::IRepository> _engine;
 
+        [global::System.ComponentModel.EditorBrowsable(global::System.ComponentModel.EditorBrowsableState.Never)]
+        global::TUnit.Mocks.IMock? global::TUnit.Mocks.IMockObject.MockWrapper { get; set; }
+
         internal IRepository_MockImpl(global::TUnit.Mocks.MockEngine<global::IRepository> engine)
         {
             _engine = engine;
diff --git a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_RefStruct_Parameters.verified.txt b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_RefStruct_Parameters.verified.txt
index 4603818ba5..47ff789005 100644
--- a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_RefStruct_Parameters.verified.txt
+++ b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_RefStruct_Parameters.verified.txt
@@ -30,10 +30,13 @@ namespace TUnit.Mocks.Generated
 
 namespace TUnit.Mocks.Generated
 {
-    internal sealed class IBufferProcessor_MockImpl : global::IBufferProcessor, global::TUnit.Mocks.IRaisable
+    internal sealed class IBufferProcessor_MockImpl : global::IBufferProcessor, global::TUnit.Mocks.IRaisable, global::TUnit.Mocks.IMockObject
     {
         private readonly global::TUnit.Mocks.MockEngine<global::IBufferProcessor> _engine;
 
+        [global::System.ComponentModel.EditorBrowsable(global::System.ComponentModel.EditorBrowsableState.Never)]
+        global::TUnit.Mocks.IMock? global::TUnit.Mocks.IMockObject.MockWrapper { get; set; }
+
         internal IBufferProcessor_MockImpl(global::TUnit.Mocks.MockEngine<global::IBufferProcessor> engine)
         {
             _engine = engine;
diff --git a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Static_Abstract_Members.verified.txt b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Static_Abstract_Members.verified.txt
index 9a09752e23..4f298aeab3 100644
--- a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Static_Abstract_Members.verified.txt
+++ b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Static_Abstract_Members.verified.txt
@@ -79,10 +79,13 @@ namespace TUnit.Mocks.Generated
 
 namespace TUnit.Mocks.Generated
 {
-    internal sealed class IServiceFactory_MockImpl : global::TUnit.Mocks.Generated.IServiceFactory_Mockable, global::TUnit.Mocks.IRaisable
+    internal sealed class IServiceFactory_MockImpl : global::TUnit.Mocks.Generated.IServiceFactory_Mockable, global::TUnit.Mocks.IRaisable, global::TUnit.Mocks.IMockObject
     {
         private readonly global::TUnit.Mocks.MockEngine<global::TUnit.Mocks.Generated.IServiceFactory_Mockable> _engine;
 
+        [global::System.ComponentModel.EditorBrowsable(global::System.ComponentModel.EditorBrowsableState.Never)]
+        global::TUnit.Mocks.IMock? global::TUnit.Mocks.IMockObject.MockWrapper { get; set; }
+
         internal IServiceFactory_MockImpl(global::TUnit.Mocks.MockEngine<global::TUnit.Mocks.Generated.IServiceFactory_Mockable> engine)
         {
             _engine = engine;
diff --git a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Static_Abstract_Transitive_Return_Type.verified.txt b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Static_Abstract_Transitive_Return_Type.verified.txt
index bee541a03d..2545746aa2 100644
--- a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Static_Abstract_Transitive_Return_Type.verified.txt
+++ b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Interface_With_Static_Abstract_Transitive_Return_Type.verified.txt
@@ -1,4 +1,4 @@
-// <auto-generated/>
+// <auto-generated/>
 #nullable enable
 
 namespace TUnit.Mocks.Generated
@@ -30,10 +30,13 @@ namespace TUnit.Mocks.Generated
 
 namespace TUnit.Mocks.Generated
 {
-    internal sealed class IMyService_MockImpl : global::IMyService, global::TUnit.Mocks.IRaisable
+    internal sealed class IMyService_MockImpl : global::IMyService, global::TUnit.Mocks.IRaisable, global::TUnit.Mocks.IMockObject
     {
         private readonly global::TUnit.Mocks.MockEngine<global::IMyService> _engine;
 
+        [global::System.ComponentModel.EditorBrowsable(global::System.ComponentModel.EditorBrowsableState.Never)]
+        global::TUnit.Mocks.IMock? global::TUnit.Mocks.IMockObject.MockWrapper { get; set; }
+
         internal IMyService_MockImpl(global::TUnit.Mocks.MockEngine<global::IMyService> engine)
         {
             _engine = engine;
@@ -100,7 +103,9 @@ namespace TUnit.Mocks.Generated
         private readonly int _memberId;
         private readonly string _memberName;
         private readonly global::TUnit.Mocks.Arguments.IArgumentMatcher[] _matchers;
-        private readonly global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<string>> _lazyBuilder;
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string>? _builder;
+        private bool _builderInitialized;
+        private object? _builderLock;
 
         internal IMyService_GetValue_M0_MockCall(global::TUnit.Mocks.IMockEngineAccess engine, int memberId, string memberName, global::TUnit.Mocks.Arguments.IArgumentMatcher[] matchers)
         {
@@ -108,16 +113,15 @@ namespace TUnit.Mocks.Generated
             _memberId = memberId;
             _memberName = memberName;
             _matchers = matchers;
-            _lazyBuilder = new global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<string>>(() =>
+        }
+
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string> EnsureSetup() =>
+            global::System.Threading.LazyInitializer.EnsureInitialized(ref _builder, ref _builderInitialized, ref _builderLock, () =>
             {
                 var setup = new global::TUnit.Mocks.Setup.MethodSetup(_memberId, _matchers, _memberName);
                 _engine.AddSetup(setup);
                 return new global::TUnit.Mocks.Setup.MethodSetupBuilder<string>(setup);
-            }
-            );
-        }
-
-        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string> EnsureSetup() => _lazyBuilder.Value;
+            })!;
 
         /// <inheritdoc />
         public IMyService_GetValue_M0_MockCall Returns(string value) { EnsureSetup().Returns(value); return this; }
diff --git a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Multi_Method_Interface.verified.txt b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Multi_Method_Interface.verified.txt
index 1b4c77e37f..f7429cf72c 100644
--- a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Multi_Method_Interface.verified.txt
+++ b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Multi_Method_Interface.verified.txt
@@ -1,4 +1,4 @@
-// <auto-generated/>
+// <auto-generated/>
 #nullable enable
 
 namespace TUnit.Mocks.Generated
@@ -30,10 +30,13 @@ namespace TUnit.Mocks.Generated
 
 namespace TUnit.Mocks.Generated
 {
-    internal sealed class ICalculator_MockImpl : global::ICalculator, global::TUnit.Mocks.IRaisable
+    internal sealed class ICalculator_MockImpl : global::ICalculator, global::TUnit.Mocks.IRaisable, global::TUnit.Mocks.IMockObject
     {
         private readonly global::TUnit.Mocks.MockEngine<global::ICalculator> _engine;
 
+        [global::System.ComponentModel.EditorBrowsable(global::System.ComponentModel.EditorBrowsableState.Never)]
+        global::TUnit.Mocks.IMock? global::TUnit.Mocks.IMockObject.MockWrapper { get; set; }
+
         internal ICalculator_MockImpl(global::TUnit.Mocks.MockEngine<global::ICalculator> engine)
         {
             _engine = engine;
@@ -142,7 +145,9 @@ namespace TUnit.Mocks.Generated
         private readonly int _memberId;
         private readonly string _memberName;
         private readonly global::TUnit.Mocks.Arguments.IArgumentMatcher[] _matchers;
-        private readonly global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<int>> _lazyBuilder;
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<int>? _builder;
+        private bool _builderInitialized;
+        private object? _builderLock;
 
         internal ICalculator_Add_M0_MockCall(global::TUnit.Mocks.IMockEngineAccess engine, int memberId, string memberName, global::TUnit.Mocks.Arguments.IArgumentMatcher[] matchers)
         {
@@ -150,16 +155,15 @@ namespace TUnit.Mocks.Generated
             _memberId = memberId;
             _memberName = memberName;
             _matchers = matchers;
-            _lazyBuilder = new global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<int>>(() =>
+        }
+
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<int> EnsureSetup() =>
+            global::System.Threading.LazyInitializer.EnsureInitialized(ref _builder, ref _builderInitialized, ref _builderLock, () =>
             {
                 var setup = new global::TUnit.Mocks.Setup.MethodSetup(_memberId, _matchers, _memberName);
                 _engine.AddSetup(setup);
                 return new global::TUnit.Mocks.Setup.MethodSetupBuilder<int>(setup);
-            }
-            );
-        }
-
-        private global::TUnit.Mocks.Setup.MethodSetupBuilder<int> EnsureSetup() => _lazyBuilder.Value;
+            })!;
 
         /// <inheritdoc />
         public ICalculator_Add_M0_MockCall Returns(int value) { EnsureSetup().Returns(value); return this; }
@@ -231,7 +235,9 @@ namespace TUnit.Mocks.Generated
         private readonly int _memberId;
         private readonly string _memberName;
         private readonly global::TUnit.Mocks.Arguments.IArgumentMatcher[] _matchers;
-        private readonly global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<int>> _lazyBuilder;
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<int>? _builder;
+        private bool _builderInitialized;
+        private object? _builderLock;
 
         internal ICalculator_Subtract_M1_MockCall(global::TUnit.Mocks.IMockEngineAccess engine, int memberId, string memberName, global::TUnit.Mocks.Arguments.IArgumentMatcher[] matchers)
         {
@@ -239,16 +245,15 @@ namespace TUnit.Mocks.Generated
             _memberId = memberId;
             _memberName = memberName;
             _matchers = matchers;
-            _lazyBuilder = new global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<int>>(() =>
+        }
+
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<int> EnsureSetup() =>
+            global::System.Threading.LazyInitializer.EnsureInitialized(ref _builder, ref _builderInitialized, ref _builderLock, () =>
             {
                 var setup = new global::TUnit.Mocks.Setup.MethodSetup(_memberId, _matchers, _memberName);
                 _engine.AddSetup(setup);
                 return new global::TUnit.Mocks.Setup.MethodSetupBuilder<int>(setup);
-            }
-            );
-        }
-
-        private global::TUnit.Mocks.Setup.MethodSetupBuilder<int> EnsureSetup() => _lazyBuilder.Value;
+            })!;
 
         /// <inheritdoc />
         public ICalculator_Subtract_M1_MockCall Returns(int value) { EnsureSetup().Returns(value); return this; }
diff --git a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Simple_Interface_With_One_Method.verified.txt b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Simple_Interface_With_One_Method.verified.txt
index 4ed109f3f2..dbb7feef84 100644
--- a/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Simple_Interface_With_One_Method.verified.txt
+++ b/TUnit.Mocks.SourceGenerator.Tests/Snapshots/Simple_Interface_With_One_Method.verified.txt
@@ -1,4 +1,4 @@
-// <auto-generated/>
+// <auto-generated/>
 #nullable enable
 
 namespace TUnit.Mocks.Generated
@@ -30,10 +30,13 @@ namespace TUnit.Mocks.Generated
 
 namespace TUnit.Mocks.Generated
 {
-    internal sealed class IGreeter_MockImpl : global::IGreeter, global::TUnit.Mocks.IRaisable
+    internal sealed class IGreeter_MockImpl : global::IGreeter, global::TUnit.Mocks.IRaisable, global::TUnit.Mocks.IMockObject
     {
         private readonly global::TUnit.Mocks.MockEngine<global::IGreeter> _engine;
 
+        [global::System.ComponentModel.EditorBrowsable(global::System.ComponentModel.EditorBrowsableState.Never)]
+        global::TUnit.Mocks.IMock? global::TUnit.Mocks.IMockObject.MockWrapper { get; set; }
+
         internal IGreeter_MockImpl(global::TUnit.Mocks.MockEngine<global::IGreeter> engine)
         {
             _engine = engine;
@@ -83,7 +86,9 @@ namespace TUnit.Mocks.Generated
         private readonly int _memberId;
         private readonly string _memberName;
         private readonly global::TUnit.Mocks.Arguments.IArgumentMatcher[] _matchers;
-        private readonly global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<string>> _lazyBuilder;
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string>? _builder;
+        private bool _builderInitialized;
+        private object? _builderLock;
 
         internal IGreeter_Greet_M0_MockCall(global::TUnit.Mocks.IMockEngineAccess engine, int memberId, string memberName, global::TUnit.Mocks.Arguments.IArgumentMatcher[] matchers)
         {
@@ -91,16 +96,15 @@ namespace TUnit.Mocks.Generated
             _memberId = memberId;
             _memberName = memberName;
             _matchers = matchers;
-            _lazyBuilder = new global::System.Lazy<global::TUnit.Mocks.Setup.MethodSetupBuilder<string>>(() =>
+        }
+
+        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string> EnsureSetup() =>
+            global::System.Threading.LazyInitializer.EnsureInitialized(ref _builder, ref _builderInitialized, ref _builderLock, () =>
             {
                 var setup = new global::TUnit.Mocks.Setup.MethodSetup(_memberId, _matchers, _memberName);
                 _engine.AddSetup(setup);
                 return new global::TUnit.Mocks.Setup.MethodSetupBuilder<string>(setup);
-            }
-            );
-        }
-
-        private global::TUnit.Mocks.Setup.MethodSetupBuilder<string> EnsureSetup() => _lazyBuilder.Value;
+            })!;
 
         /// <inheritdoc />
         public IGreeter_Greet_M0_MockCall Returns(string value) { EnsureSetup().Returns(value); return this; }
diff --git a/TUnit.Mocks.SourceGenerator/Builders/MockImplBuilder.cs b/TUnit.Mocks.SourceGenerator/Builders/MockImplBuilder.cs
index 518deccb33..99c83d7e4b 100644
--- a/TUnit.Mocks.SourceGenerator/Builders/MockImplBuilder.cs
+++ b/TUnit.Mocks.SourceGenerator/Builders/MockImplBuilder.cs
@@ -45,11 +45,13 @@ private static void BuildInterfaceMockImpl(CodeWriter writer, MockTypeModel mode
             baseTypes += ", " + string.Join(", ", model.AdditionalInterfaceNames);
         }
 
-        using (writer.Block($"internal sealed class {safeName}_MockImpl : {baseTypes}, global::TUnit.Mocks.IRaisable"))
+        using (writer.Block($"internal sealed class {safeName}_MockImpl : {baseTypes}, global::TUnit.Mocks.IRaisable, global::TUnit.Mocks.IMockObject"))
         {
             writer.AppendLine($"private readonly global::TUnit.Mocks.MockEngine<{mockableType}> _engine;");
             writer.AppendLine();
 
+            EmitIMockObjectProperty(writer);
+
             // Constructor
             using (writer.Block($"internal {safeName}_MockImpl(global::TUnit.Mocks.MockEngine<{mockableType}> engine)"))
             {
@@ -95,12 +97,14 @@ private static void BuildWrapMockImpl(CodeWriter writer, MockTypeModel model, st
     {
         var mockableType = GetMockableTypeName(model);
 
-        using (writer.Block($"internal sealed class {safeName}_WrapMockImpl : {model.FullyQualifiedName}, global::TUnit.Mocks.IRaisable"))
+        using (writer.Block($"internal sealed class {safeName}_WrapMockImpl : {model.FullyQualifiedName}, global::TUnit.Mocks.IRaisable, global::TUnit.Mocks.IMockObject"))
         {
             writer.AppendLine($"private readonly global::TUnit.Mocks.MockEngine<{mockableType}> _engine;");
             writer.AppendLine($"private readonly {model.FullyQualifiedName} _wrappedInstance;");
             writer.AppendLine();
 
+            EmitIMockObjectProperty(writer);
+
             // Generate constructors that pass through to base + accept wrapped instance
             GenerateWrapConstructors(writer, model, safeName);
 
@@ -421,11 +425,13 @@ private static void BuildPartialMockImpl(CodeWriter writer, MockTypeModel model,
     {
         var mockableType = GetMockableTypeName(model);
 
-        using (writer.Block($"internal sealed class {safeName}_MockImpl : {model.FullyQualifiedName}, global::TUnit.Mocks.IRaisable"))
+        using (writer.Block($"internal sealed class {safeName}_MockImpl : {model.FullyQualifiedName}, global::TUnit.Mocks.IRaisable, global::TUnit.Mocks.IMockObject"))
         {
             writer.AppendLine($"private readonly global::TUnit.Mocks.MockEngine<{mockableType}> _engine;");
             writer.AppendLine();
 
+            EmitIMockObjectProperty(writer);
+
             // Generate constructors that pass through to base
             GeneratePartialConstructors(writer, model, safeName);
 
@@ -1268,6 +1274,13 @@ public static string GetMockableTypeName(MockTypeModel model)
     /// Emits the static engine assignment with a guard that detects multiple mocks of the same
     /// static-abstract interface type within a single test context.
     /// </summary>
+    private static void EmitIMockObjectProperty(CodeWriter writer)
+    {
+        writer.AppendLine("[global::System.ComponentModel.EditorBrowsable(global::System.ComponentModel.EditorBrowsableState.Never)]");
+        writer.AppendLine("global::TUnit.Mocks.IMock? global::TUnit.Mocks.IMockObject.MockWrapper { get; set; }");
+        writer.AppendLine();
+    }
+
     internal static void EmitStaticEngineAssignment(CodeWriter writer, string safeName)
     {
         writer.AppendLine($"if ({safeName}_StaticEngine.Engine is not null)");
diff --git a/TUnit.Mocks.SourceGenerator/Builders/MockMembersBuilder.cs b/TUnit.Mocks.SourceGenerator/Builders/MockMembersBuilder.cs
index 2de65e25f4..c3339ed0a2 100644
--- a/TUnit.Mocks.SourceGenerator/Builders/MockMembersBuilder.cs
+++ b/TUnit.Mocks.SourceGenerator/Builders/MockMembersBuilder.cs
@@ -153,10 +153,12 @@ private static void GenerateReturnUnifiedClass(CodeWriter writer, string wrapper
             writer.AppendLine("private readonly int _memberId;");
             writer.AppendLine("private readonly string _memberName;");
             writer.AppendLine("private readonly global::TUnit.Mocks.Arguments.IArgumentMatcher[] _matchers;");
-            writer.AppendLine($"private readonly global::System.Lazy<{builderType}> _lazyBuilder;");
+            writer.AppendLine($"private {builderType}? _builder;");
+            writer.AppendLine("private bool _builderInitialized;");
+            writer.AppendLine("private object? _builderLock;");
             writer.AppendLine();
 
-            // Constructor — lazy registration via Lazy<T> for thread safety
+            // Constructor
             writer.AppendLine($"internal {wrapperName}(global::TUnit.Mocks.IMockEngineAccess engine, int memberId, string memberName, global::TUnit.Mocks.Arguments.IArgumentMatcher[] matchers)");
             using (writer.Block())
             {
@@ -164,19 +166,12 @@ private static void GenerateReturnUnifiedClass(CodeWriter writer, string wrapper
                 writer.AppendLine("_memberId = memberId;");
                 writer.AppendLine("_memberName = memberName;");
                 writer.AppendLine("_matchers = matchers;");
-                using (writer.Block($"_lazyBuilder = new global::System.Lazy<{builderType}>(() =>"))
-                {
-                    writer.AppendLine("var setup = new global::TUnit.Mocks.Setup.MethodSetup(_memberId, _matchers, _memberName);");
-                    writer.AppendLine("_engine.AddSetup(setup);");
-                    writer.AppendLine($"return new {builderType}(setup);");
-                }
-                writer.AppendLine(");");
             }
 
             writer.AppendLine();
 
-            // EnsureSetup method
-            writer.AppendLine($"private {builderType} EnsureSetup() => _lazyBuilder.Value;");
+            // EnsureSetup method — uses LazyInitializer to guarantee exactly-once AddSetup
+            EmitEnsureSetup(writer, builderType);
 
             writer.AppendLine();
 
@@ -290,10 +285,12 @@ private static void GenerateVoidUnifiedClass(CodeWriter writer, string wrapperNa
             writer.AppendLine("private readonly int _memberId;");
             writer.AppendLine("private readonly string _memberName;");
             writer.AppendLine("private readonly global::TUnit.Mocks.Arguments.IArgumentMatcher[] _matchers;");
-            writer.AppendLine($"private readonly global::System.Lazy<{builderType}> _lazyBuilder;");
+            writer.AppendLine($"private {builderType}? _builder;");
+            writer.AppendLine("private bool _builderInitialized;");
+            writer.AppendLine("private object? _builderLock;");
             writer.AppendLine();
 
-            // Constructor — Lazy<T> for thread safety, eagerly materialized because void methods
+            // Constructor — eagerly registers because void methods
             // are commonly used without chaining (e.g., mock.Log(Arg.Any<string>()) in strict mode).
             writer.AppendLine($"internal {wrapperName}(global::TUnit.Mocks.IMockEngineAccess engine, int memberId, string memberName, global::TUnit.Mocks.Arguments.IArgumentMatcher[] matchers)");
             using (writer.Block())
@@ -302,20 +299,13 @@ private static void GenerateVoidUnifiedClass(CodeWriter writer, string wrapperNa
                 writer.AppendLine("_memberId = memberId;");
                 writer.AppendLine("_memberName = memberName;");
                 writer.AppendLine("_matchers = matchers;");
-                using (writer.Block($"_lazyBuilder = new global::System.Lazy<{builderType}>(() =>"))
-                {
-                    writer.AppendLine("var setup = new global::TUnit.Mocks.Setup.MethodSetup(_memberId, _matchers, _memberName);");
-                    writer.AppendLine("_engine.AddSetup(setup);");
-                    writer.AppendLine($"return new {builderType}(setup);");
-                }
-                writer.AppendLine(");");
-                writer.AppendLine("_ = _lazyBuilder.Value;");
+                writer.AppendLine("_ = EnsureSetup();");
             }
 
             writer.AppendLine();
 
-            // EnsureSetup method
-            writer.AppendLine($"private {builderType} EnsureSetup() => _lazyBuilder.Value;");
+            // EnsureSetup method — uses LazyInitializer to guarantee exactly-once AddSetup
+            EmitEnsureSetup(writer, builderType);
 
             writer.AppendLine();
 
@@ -869,4 +859,17 @@ private static string GetArgParameterList(MockMemberModel method, bool includeRe
         return string.Join(", ", parts);
     }
 
+    private static void EmitEnsureSetup(CodeWriter writer, string builderType)
+    {
+        writer.AppendLine($"private {builderType} EnsureSetup() =>");
+        writer.IncreaseIndent();
+        writer.AppendLine($"global::System.Threading.LazyInitializer.EnsureInitialized(ref _builder, ref _builderInitialized, ref _builderLock, () =>");
+        writer.OpenBrace();
+        writer.AppendLine("var setup = new global::TUnit.Mocks.Setup.MethodSetup(_memberId, _matchers, _memberName);");
+        writer.AppendLine("_engine.AddSetup(setup);");
+        writer.AppendLine($"return new {builderType}(setup);");
+        writer.CloseBrace(")!;");
+        writer.DecreaseIndent();
+    }
+
 }
diff --git a/TUnit.Mocks/IMockObject.cs b/TUnit.Mocks/IMockObject.cs
new file mode 100644
index 0000000000..214e94ea20
--- /dev/null
+++ b/TUnit.Mocks/IMockObject.cs
@@ -0,0 +1,25 @@
+using System.ComponentModel;
+
+namespace TUnit.Mocks;
+
+/// <summary>
+/// Implemented by generated mock impl classes to allow reverse-lookup
+/// from a mock object to its <see cref="Mock{T}"/> wrapper without using
+/// ConditionalWeakTable. Not intended for direct use.
+/// </summary>
+/// <remarks>
+/// This interface is public because it must be implemented by source-generated code
+/// in the user's assembly. The setter is required because the wrapper is assigned by
+/// <see cref="Mock{T}"/>'s constructor after the impl object is created.
+/// <see cref="EditorBrowsableAttribute"/> hides it from IDE autocompletion.
+/// </remarks>
+[EditorBrowsable(EditorBrowsableState.Never)]
+public interface IMockObject
+{
+    /// <summary>
+    /// The <see cref="IMock"/> wrapper for this mock object.
+    /// Set once by the <see cref="Mock{T}"/> constructor; should not be reassigned.
+    /// </summary>
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    IMock? MockWrapper { get; set; }
+}
diff --git a/TUnit.Mocks/Mock.cs b/TUnit.Mocks/Mock.cs
index 132c7eb29c..2553ea2e6d 100644
--- a/TUnit.Mocks/Mock.cs
+++ b/TUnit.Mocks/Mock.cs
@@ -1,5 +1,4 @@
 using System.Collections.Concurrent;
-using System.Runtime.CompilerServices;
 using TUnit.Mocks.Diagnostics;
 using TUnit.Mocks.Verification;
 
@@ -10,10 +9,6 @@ namespace TUnit.Mocks;
 /// </summary>
 public static class Mock
 {
-    // Maps mock implementation objects back to their Mock<T> wrappers.
-    // ConditionalWeakTable so mocks can be GC'd normally.
-    private static readonly ConditionalWeakTable<object, IMock> _objectToMock = new();
-
     // The source generator registers factories via this method at module initialization time.
     // ConcurrentDictionary is used because module initializers from multiple assemblies
     // can run concurrently when test assemblies are loaded in parallel.
@@ -31,21 +26,6 @@ public static class Mock
     // Separate registry for wrap mock factories that accept a real instance.
     private static readonly ConcurrentDictionary<Type, Func<MockBehavior, object, object>> _wrapFactories = new();
 
-    /// <summary>
-    /// Registers the mapping from a mock implementation object to its <see cref="Mock{T}"/> wrapper.
-    /// Called from the <see cref="Mock{T}"/> constructor. Not intended for direct use.
-    /// </summary>
-    internal static void Register(object mockObject, IMock mockWrapper)
-    {
-#if NET7_0_OR_GREATER
-        _objectToMock.AddOrUpdate(mockObject, mockWrapper);
-#else
-        // ConditionalWeakTable.AddOrUpdate not available before .NET 7.
-        // Each mock object is unique (created by new), so Add will not throw.
-        _objectToMock.Add(mockObject, mockWrapper);
-#endif
-    }
-
     /// <summary>
     /// Retrieves the <see cref="Mock{T}"/> wrapper for a mock implementation object.
     /// Use this to access the mock wrapper from auto-mocked return values or any mocked object.
@@ -60,13 +40,15 @@ internal static void Register(object mockObject, IMock mockWrapper)
     /// </example>
     public static Mock<T> Get<T>(T mockedObject) where T : class
     {
-        if (_objectToMock.TryGetValue(mockedObject, out var mock))
+        if (mockedObject is IMockObject { MockWrapper: { } wrapper })
         {
-            if (mock is Mock<T> typed)
+            if (wrapper is Mock<T> typed)
+            {
                 return typed;
+            }
 
             throw new InvalidOperationException(
-                $"The object is a mock of '{mock.GetType().GenericTypeArguments[0].Name}', not '{typeof(T).Name}'.");
+                $"The object is a mock of '{wrapper.GetType().GenericTypeArguments[0].Name}', not '{typeof(T).Name}'.");
         }
 
         throw new InvalidOperationException(
@@ -81,7 +63,7 @@ public static Mock<T> Get<T>(T mockedObject) where T : class
     [System.ComponentModel.EditorBrowsable(System.ComponentModel.EditorBrowsableState.Never)]
     public static void RegisterFactory<T>(Func<MockBehavior, Mock<T>> factory) where T : class
     {
-        _factories[typeof(T)] = behavior => factory(behavior);
+        _factories[typeof(T)] = factory;
     }
 
     /// <summary>
@@ -91,7 +73,7 @@ public static void RegisterFactory<T>(Func<MockBehavior, Mock<T>> factory) where
     [System.ComponentModel.EditorBrowsable(System.ComponentModel.EditorBrowsableState.Never)]
     public static void RegisterPartialFactory<T>(Func<MockBehavior, object[], Mock<T>> factory) where T : class
     {
-        _partialFactories[typeof(T)] = (behavior, args) => factory(behavior, args);
+        _partialFactories[typeof(T)] = factory;
     }
 
     /// <summary>
@@ -111,7 +93,7 @@ public static void RegisterMultiFactory(string key, Func<MockBehavior, object> f
     [System.ComponentModel.EditorBrowsable(System.ComponentModel.EditorBrowsableState.Never)]
     public static void RegisterDelegateFactory<T>(Func<MockBehavior, Mock<T>> factory) where T : class
     {
-        _delegateFactories[typeof(T)] = behavior => factory(behavior);
+        _delegateFactories[typeof(T)] = factory;
     }
 
     /// <summary>
diff --git a/TUnit.Mocks/MockEngine.cs b/TUnit.Mocks/MockEngine.cs
index b431cd82ab..2e69abad53 100644
--- a/TUnit.Mocks/MockEngine.cs
+++ b/TUnit.Mocks/MockEngine.cs
@@ -22,9 +22,9 @@ internal static class MockCallSequence
 [EditorBrowsable(EditorBrowsableState.Never)]
 public sealed class MockEngine<T> : IMockEngineAccess where T : class
 {
-    private readonly Dictionary<int, List<MethodSetup>> _setupsByMember = new();
     private readonly Lock _setupLock = new();
-    private readonly ConcurrentQueue<CallRecord> _callHistory = new();
+    private Dictionary<int, List<MethodSetup>>? _setupsByMember;
+    private ConcurrentQueue<CallRecord>? _callHistory;
 
     private ConcurrentDictionary<string, object?>? _autoTrackValues;
     private ConcurrentQueue<(string EventName, bool IsSubscribe)>? _eventSubscriptions;
@@ -119,9 +119,11 @@ public void AddSetup(MethodSetup setup)
                 setup.RequiredState = PendingRequiredState;
             }
 
-            if (!_setupsByMember.TryGetValue(setup.MemberId, out var list))
+            var dict = _setupsByMember ??= new();
+
+            if (!dict.TryGetValue(setup.MemberId, out var list))
             {
-                _setupsByMember[setup.MemberId] = list = new();
+                dict[setup.MemberId] = list = new();
             }
 
             list.Add(setup);
@@ -384,8 +386,13 @@ public bool TryHandleCallWithReturn<TReturn>(int memberId, string memberName, ob
     /// </summary>
     public IReadOnlyList<CallRecord> GetCallsFor(int memberId)
     {
+        if (Volatile.Read(ref _callHistory) is not { } history)
+        {
+            return [];
+        }
+
         var result = new List<CallRecord>();
-        foreach (var record in _callHistory)
+        foreach (var record in history)
         {
             if (record.MemberId == memberId)
             {
@@ -400,7 +407,7 @@ public IReadOnlyList<CallRecord> GetCallsFor(int memberId)
     /// </summary>
     public IReadOnlyList<CallRecord> GetAllCalls()
     {
-        return _callHistory.ToArray();
+        return Volatile.Read(ref _callHistory)?.ToArray() ?? [];
     }
 
     /// <summary>
@@ -409,8 +416,13 @@ public IReadOnlyList<CallRecord> GetAllCalls()
     [EditorBrowsable(EditorBrowsableState.Never)]
     public IReadOnlyList<CallRecord> GetUnverifiedCalls()
     {
+        if (Volatile.Read(ref _callHistory) is not { } history)
+        {
+            return [];
+        }
+
         var result = new List<CallRecord>();
-        foreach (var record in _callHistory)
+        foreach (var record in history)
         {
             if (!record.IsVerified)
             {
@@ -428,8 +440,13 @@ public IReadOnlyList<MethodSetup> GetSetups()
     {
         lock (_setupLock)
         {
+            if (_setupsByMember is not { } setups)
+            {
+                return [];
+            }
+
             var all = new List<MethodSetup>();
-            foreach (var list in _setupsByMember.Values)
+            foreach (var list in setups.Values)
             {
                 all.AddRange(list);
             }
@@ -465,11 +482,14 @@ public Diagnostics.MockDiagnostics GetDiagnostics()
         }
 
         var unmatchedCalls = new List<CallRecord>();
-        foreach (var call in _callHistory)
+        if (Volatile.Read(ref _callHistory) is { } history)
         {
-            if (call.IsUnmatched)
+            foreach (var call in history)
             {
-                unmatchedCalls.Add(call);
+                if (call.IsUnmatched)
+                {
+                    unmatchedCalls.Add(call);
+                }
             }
         }
 
@@ -497,14 +517,12 @@ public void Reset()
     {
         lock (_setupLock)
         {
-            _setupsByMember.Clear();
+            _setupsByMember = null;
             _currentState = null;
             PendingRequiredState = null;
         }
 
-        // Drain the queue
-        while (_callHistory.TryDequeue(out _)) { }
-
+        Volatile.Write(ref _callHistory, null);
         Volatile.Write(ref _autoTrackValues, null);
         Volatile.Write(ref _eventSubscriptions, null);
         Volatile.Write(ref _onSubscribeCallbacks, null);
@@ -591,7 +609,7 @@ private CallRecord RecordCall(int memberId, string memberName, object?[] args)
     {
         var seq = MockCallSequence.Next();
         var record = new CallRecord(memberId, memberName, args, seq);
-        _callHistory.Enqueue(record);
+        LazyInitializer.EnsureInitialized(ref _callHistory)!.Enqueue(record);
         return record;
     }
 
@@ -610,7 +628,7 @@ private void RaiseEventsForSetup(MethodSetup setup)
     {
         lock (_setupLock)
         {
-            if (!_setupsByMember.TryGetValue(memberId, out var setups))
+            if (_setupsByMember is not { } setupDict || !setupDict.TryGetValue(memberId, out var setups))
             {
                 return (false, null, null);
             }
diff --git a/TUnit.Mocks/MockMethodCall.cs b/TUnit.Mocks/MockMethodCall.cs
index f624192f7f..0faeac9627 100644
--- a/TUnit.Mocks/MockMethodCall.cs
+++ b/TUnit.Mocks/MockMethodCall.cs
@@ -20,7 +20,9 @@ public sealed class MockMethodCall<TReturn> : IMethodSetup<TReturn>, ISetupChain
     private readonly int _memberId;
     private readonly string _memberName;
     private readonly IArgumentMatcher[] _matchers;
-    private readonly Lazy<MethodSetupBuilder<TReturn>> _lazyBuilder;
+    private MethodSetupBuilder<TReturn>? _builder;
+    private bool _builderInitialized;
+    private object? _builderLock;
 
     [EditorBrowsable(EditorBrowsableState.Never)]
     public MockMethodCall(IMockEngineAccess engine, int memberId, string memberName, IArgumentMatcher[] matchers)
@@ -29,15 +31,15 @@ public MockMethodCall(IMockEngineAccess engine, int memberId, string memberName,
         _memberId = memberId;
         _memberName = memberName;
         _matchers = matchers;
-        _lazyBuilder = new Lazy<MethodSetupBuilder<TReturn>>(() =>
+    }
+
+    private MethodSetupBuilder<TReturn> EnsureSetup() =>
+        LazyInitializer.EnsureInitialized(ref _builder, ref _builderInitialized, ref _builderLock, () =>
         {
             var setup = new MethodSetup(_memberId, _matchers, _memberName);
             _engine.AddSetup(setup);
             return new MethodSetupBuilder<TReturn>(setup);
-        });
-    }
-
-    private MethodSetupBuilder<TReturn> EnsureSetup() => _lazyBuilder.Value;
+        })!;
 
     // IMethodSetup<TReturn> implementation
 
diff --git a/TUnit.Mocks/MockOfT.cs b/TUnit.Mocks/MockOfT.cs
index 4f9550ca11..8675f9179c 100644
--- a/TUnit.Mocks/MockOfT.cs
+++ b/TUnit.Mocks/MockOfT.cs
@@ -27,7 +27,10 @@ public Mock(T mockObject, MockEngine<T> engine)
     {
         _engine = engine;
         Object = mockObject;
-        Mock.Register(mockObject, this);
+        if (mockObject is IMockObject mockObj)
+        {
+            mockObj.MockWrapper = this;
+        }
     }
 
     /// <inheritdoc />
diff --git a/TUnit.Mocks/Setup/MethodSetup.cs b/TUnit.Mocks/Setup/MethodSetup.cs
index ac52557340..0370b2f8c2 100644
--- a/TUnit.Mocks/Setup/MethodSetup.cs
+++ b/TUnit.Mocks/Setup/MethodSetup.cs
@@ -11,12 +11,15 @@ namespace TUnit.Mocks.Setup;
 public sealed class MethodSetup
 {
     private readonly IArgumentMatcher[] _matchers;
-    private readonly Lock _behaviorLock = new();
-    private readonly List<IBehavior> _behaviors = new();
-    private readonly List<EventRaiseInfo> _eventRaises = new();
+    private Lock? _behaviorLock;
+    private List<IBehavior>? _behaviors;
+    private List<EventRaiseInfo>? _eventRaises;
+    private EventRaiseInfo[]? _eventRaisesSnapshot;
     private Dictionary<int, object?>? _outRefAssignments;
     private int _callIndex;
 
+    private Lock EnsureBehaviorLock() => LazyInitializer.EnsureInitialized(ref _behaviorLock)!;
+
     public int MemberId { get; }
 
     /// <summary>
@@ -59,9 +62,10 @@ public MethodSetup(int memberId, IArgumentMatcher[] matchers, string memberName
 
     public void AddBehavior(IBehavior behavior)
     {
-        lock (_behaviorLock)
+        lock (EnsureBehaviorLock())
         {
-            _behaviors.Add(behavior);
+            var list = _behaviors ??= new();
+            list.Add(behavior);
         }
     }
 
@@ -80,18 +84,30 @@ public bool Matches(object?[] actualArgs)
 
     public void AddEventRaise(EventRaiseInfo raiseInfo)
     {
-        lock (_behaviorLock)
+        lock (EnsureBehaviorLock())
         {
-            _eventRaises.Add(raiseInfo);
+            var list = _eventRaises ??= new();
+            list.Add(raiseInfo);
+            _eventRaisesSnapshot = null;
         }
     }
 
     [EditorBrowsable(EditorBrowsableState.Never)]
     public IReadOnlyList<EventRaiseInfo> GetEventRaises()
     {
-        lock (_behaviorLock)
+        if (Volatile.Read(ref _eventRaises) is null)
+        {
+            return [];
+        }
+
+        if (Volatile.Read(ref _eventRaisesSnapshot) is { } snapshot)
         {
-            return _eventRaises.ToList();
+            return snapshot;
+        }
+
+        lock (EnsureBehaviorLock())
+        {
+            return _eventRaisesSnapshot ??= _eventRaises!.ToArray();
         }
     }
 
@@ -118,7 +134,7 @@ public void ApplyCaptures(object?[] args)
     /// <param name="value">The value to assign.</param>
     public void SetOutRefValue(int paramIndex, object? value)
     {
-        lock (_behaviorLock)
+        lock (EnsureBehaviorLock())
         {
             _outRefAssignments ??= new Dictionary<int, object?>();
             _outRefAssignments[paramIndex] = value;
@@ -133,7 +149,13 @@ public void SetOutRefValue(int paramIndex, object? value)
     {
         get
         {
-            lock (_behaviorLock)
+            var lck = Volatile.Read(ref _behaviorLock);
+            if (lck is null)
+            {
+                return null;
+            }
+
+            lock (lck)
             {
                 return _outRefAssignments;
             }
@@ -156,15 +178,22 @@ public string[] GetMatcherDescriptions()
 
     public IBehavior? GetNextBehavior()
     {
-        lock (_behaviorLock)
+        if (Volatile.Read(ref _behaviors) is null)
+        {
+            return null;
+        }
+
+        lock (EnsureBehaviorLock())
         {
-            if (_behaviors.Count == 0)
+            if (_behaviors is not { Count: > 0 } behaviors)
+            {
                 return null;
+            }
 
             var index = _callIndex;
             if (_callIndex < int.MaxValue) _callIndex++;
             // Clamp to last behavior (last one repeats)
-            return _behaviors[Math.Min(index, _behaviors.Count - 1)];
+            return behaviors[Math.Min(index, behaviors.Count - 1)];
         }
     }
 }
diff --git a/TUnit.Mocks/VoidMockMethodCall.cs b/TUnit.Mocks/VoidMockMethodCall.cs
index 2df33a2ea5..c2bf80012c 100644
--- a/TUnit.Mocks/VoidMockMethodCall.cs
+++ b/TUnit.Mocks/VoidMockMethodCall.cs
@@ -22,7 +22,9 @@ public sealed class VoidMockMethodCall : IVoidMethodSetup, IVoidSetupChain, ICal
     private readonly int _memberId;
     private readonly string _memberName;
     private readonly IArgumentMatcher[] _matchers;
-    private readonly Lazy<VoidMethodSetupBuilder> _lazyBuilder;
+    private VoidMethodSetupBuilder? _builder;
+    private bool _builderInitialized;
+    private object? _builderLock;
 
     [EditorBrowsable(EditorBrowsableState.Never)]
     public VoidMockMethodCall(IMockEngineAccess engine, int memberId, string memberName, IArgumentMatcher[] matchers)
@@ -37,19 +39,19 @@ internal VoidMockMethodCall(IMockEngineAccess engine, int memberId, string membe
         _memberId = memberId;
         _memberName = memberName;
         _matchers = matchers;
-        _lazyBuilder = new Lazy<VoidMethodSetupBuilder>(() =>
-        {
-            var setup = new MethodSetup(_memberId, _matchers, _memberName);
-            _engine.AddSetup(setup);
-            return new VoidMethodSetupBuilder(setup);
-        });
         if (eagerRegister)
         {
-            _ = _lazyBuilder.Value;
+            _ = EnsureSetup();
         }
     }
 
-    private VoidMethodSetupBuilder EnsureSetup() => _lazyBuilder.Value;
+    private VoidMethodSetupBuilder EnsureSetup() =>
+        LazyInitializer.EnsureInitialized(ref _builder, ref _builderInitialized, ref _builderLock, () =>
+        {
+            var setup = new MethodSetup(_memberId, _matchers, _memberName);
+            _engine.AddSetup(setup);
+            return new VoidMethodSetupBuilder(setup);
+        })!;
 
     // IVoidMethodSetup implementation