diff --git a/build/NuSpecs/WindowsAppSDK-Nuget-Native.AutoInitializer.targets b/build/NuSpecs/WindowsAppSDK-Nuget-Native.AutoInitializer.targets
index ae3313a43a..84d201c520 100644
--- a/build/NuSpecs/WindowsAppSDK-Nuget-Native.AutoInitializer.targets
+++ b/build/NuSpecs/WindowsAppSDK-Nuget-Native.AutoInitializer.targets
@@ -2,14 +2,31 @@
 <!-- Copyright (c) Microsoft Corporation. All rights reserved. Licensed under the MIT License. See LICENSE in the project root for license information. -->
 <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
 
+  <ItemDefinitionGroup>
+    <!-- Add the appropriate definition to the ClCompile ItemDefinitionGroup to apply to all compilations -->
+    <ClCompile>
+      <PreprocessorDefinitions Condition="'$(WindowsAppSdkBootstrapInitialize)'=='true'">MICROSOFT_WINDOWSAPPSDK_AUTOINITIALIZE_BOOTSTRAP;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions Condition="'$(WindowsAppSdkDeploymentManagerInitialize)'=='true'">MICROSOFT_WINDOWSAPPSDK_AUTOINITIALIZE_DEPLOYMENTMANAGER;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions Condition="'$(WindowsAppSdkUndockedRegFreeWinRTInitialize)'=='true'">MICROSOFT_WINDOWSAPPSDK_AUTOINITIALIZE_UNDOCKEDREGFREEWINRT;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions Condition="'$(WindowsAppSdkCompatibilityInitialize)'=='true'">MICROSOFT_WINDOWSAPPSDK_AUTOINITIALIZE_COMPATIBILITY;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+    </ClCompile>
+  </ItemDefinitionGroup>
+
+  <!-- ARM64EC + LTCG ICE workaround: auto-enabled when conditions met, customers can override -->
+  <PropertyGroup>
+    <WindowsAppSDK_Arm64EcCompilerWorkaround Condition="'$(WindowsAppSDK_Arm64EcCompilerWorkaround)'==''
+        And '$(Platform)'=='ARM64EC'
+        And ('$(WholeProgramOptimization)'=='true' Or '$(LinkTimeCodeGeneration)'=='true')">true</WindowsAppSDK_Arm64EcCompilerWorkaround>
+  </PropertyGroup>
+
   <Target Name="WindowsAppRuntimeAutoInitializer">
     <ItemGroup>
       <ClCompile Include="$(MSBuildThisFileDirectory)..\..\include\WindowsAppRuntimeAutoInitializer.cpp">
         <PrecompiledHeader>NotUsing</PrecompiledHeader>
-        <PreprocessorDefinitions Condition="'$(WindowsAppSdkBootstrapInitialize)'=='true'">MICROSOFT_WINDOWSAPPSDK_AUTOINITIALIZE_BOOTSTRAP;%(PreprocessorDefinitions)</PreprocessorDefinitions>
-        <PreprocessorDefinitions Condition="'$(WindowsAppSdkDeploymentManagerInitialize)'=='true'">MICROSOFT_WINDOWSAPPSDK_AUTOINITIALIZE_DEPLOYMENTMANAGER;%(PreprocessorDefinitions)</PreprocessorDefinitions>
-        <PreprocessorDefinitions Condition="'$(WindowsAppSdkUndockedRegFreeWinRTInitialize)'=='true'">MICROSOFT_WINDOWSAPPSDK_AUTOINITIALIZE_UNDOCKEDREGFREEWINRT;%(PreprocessorDefinitions)</PreprocessorDefinitions>
-        <PreprocessorDefinitions Condition="'$(WindowsAppSdkCompatibilityInitialize)'=='true'">MICROSOFT_WINDOWSAPPSDK_AUTOINITIALIZE_COMPATIBILITY;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      </ClCompile>
+      <ClCompile Include="$(MSBuildThisFileDirectory)..\..\include\WindowsAppRuntimeAutoInitializer.cpp" Condition="'$(WindowsAppSDK_Arm64EcCompilerWorkaround)'=='true'">
+        <PrecompiledHeader>NotUsing</PrecompiledHeader>
+        <ObjectFileName>$(IntDir)WindowsAppRuntimeAutoInitializer_dup.obj</ObjectFileName>
       </ClCompile>
     </ItemGroup>
   </Target>
@@ -21,3 +38,4 @@
   </PropertyGroup>
 
 </Project>
+
diff --git a/build/NuSpecs/WindowsAppSDK-Nuget-Native.Bootstrap.targets b/build/NuSpecs/WindowsAppSDK-Nuget-Native.Bootstrap.targets
index b6d6b2c7c5..94bd3c8544 100644
--- a/build/NuSpecs/WindowsAppSDK-Nuget-Native.Bootstrap.targets
+++ b/build/NuSpecs/WindowsAppSDK-Nuget-Native.Bootstrap.targets
@@ -1,17 +1,23 @@
 <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
 
+    <ItemDefinitionGroup>
+        <!-- Add the appropriate definition to the ClCompile ItemDefinitionGroup to apply to all compilations -->
+        <ClCompile>
+            <PreprocessorDefinitions Condition="'$(WindowsAppSDKBootstrapAutoInitializeOptions_Default)'=='true'">MICROSOFT_WINDOWSAPPSDK_BOOTSTRAP_AUTO_INITIALIZE_OPTIONS_DEFAULT;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+            <PreprocessorDefinitions Condition="'$(WindowsAppSDKBootstrapAutoInitializeOptions_None)'=='true'">MICROSOFT_WINDOWSAPPSDK_BOOTSTRAP_AUTO_INITIALIZE_OPTIONS_NONE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+            <PreprocessorDefinitions Condition="'$(WindowsAppSDKBootstrapAutoInitializeOptions_OnError_DebugBreak)'=='true'">MICROSOFT_WINDOWSAPPSDK_BOOTSTRAP_AUTO_INITIALIZE_OPTIONS_ONERROR_DEBUGBREAK;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+            <PreprocessorDefinitions Condition="'$(WindowsAppSDKBootstrapAutoInitializeOptions_OnError_DebugBreak_IfDebuggerAttached)'=='true'">MICROSOFT_WINDOWSAPPSDK_BOOTSTRAP_AUTO_INITIALIZE_OPTIONS_ONERROR_DEBUGBREAK_IFDEBUGGERATTACHED;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+            <PreprocessorDefinitions Condition="'$(WindowsAppSDKBootstrapAutoInitializeOptions_OnError_FailFast)'=='true'">MICROSOFT_WINDOWSAPPSDK_BOOTSTRAP_AUTO_INITIALIZE_OPTIONS_ONERROR_FAILFAST;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+            <PreprocessorDefinitions Condition="'$(WindowsAppSDKBootstrapAutoInitializeOptions_OnNoMatch_ShowUI)'=='true'">MICROSOFT_WINDOWSAPPSDK_BOOTSTRAP_AUTO_INITIALIZE_OPTIONS_ONNOMATCH_SHOWUI;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+            <PreprocessorDefinitions Condition="'$(WindowsAppSDKBootstrapAutoInitializeOptions_OnPackageIdentity_NoOp)'=='true'">MICROSOFT_WINDOWSAPPSDK_BOOTSTRAP_AUTO_INITIALIZE_OPTIONS_ONPACKAGEIDENTITY_NOOP;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+            <PreprocessorDefinitions>%(PreprocessorDefinitions);MICROSOFT_WINDOWSAPPSDK_BOOTSTRAP_AUTO_INITIALIZE=1</PreprocessorDefinitions>
+        </ClCompile>
+    </ItemDefinitionGroup>
+
     <Target Name="GenerateBootstrapCpp">
         <ItemGroup>
             <ClCompile Include="$(MSBuildThisFileDirectory)..\..\include\MddBootstrapAutoInitializer.cpp">
                 <PrecompiledHeader>NotUsing</PrecompiledHeader>
-                <PreprocessorDefinitions Condition="'$(WindowsAppSDKBootstrapAutoInitializeOptions_Default)'=='true'">MICROSOFT_WINDOWSAPPSDK_BOOTSTRAP_AUTO_INITIALIZE_OPTIONS_DEFAULT;%(PreprocessorDefinitions)</PreprocessorDefinitions>
-                <PreprocessorDefinitions Condition="'$(WindowsAppSDKBootstrapAutoInitializeOptions_None)'=='true'">MICROSOFT_WINDOWSAPPSDK_BOOTSTRAP_AUTO_INITIALIZE_OPTIONS_NONE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
-                <PreprocessorDefinitions Condition="'$(WindowsAppSDKBootstrapAutoInitializeOptions_OnError_DebugBreak)'=='true'">MICROSOFT_WINDOWSAPPSDK_BOOTSTRAP_AUTO_INITIALIZE_OPTIONS_ONERROR_DEBUGBREAK;%(PreprocessorDefinitions)</PreprocessorDefinitions>
-                <PreprocessorDefinitions Condition="'$(WindowsAppSDKBootstrapAutoInitializeOptions_OnError_DebugBreak_IfDebuggerAttached)'=='true'">MICROSOFT_WINDOWSAPPSDK_BOOTSTRAP_AUTO_INITIALIZE_OPTIONS_ONERROR_DEBUGBREAK_IFDEBUGGERATTACHED;%(PreprocessorDefinitions)</PreprocessorDefinitions>
-                <PreprocessorDefinitions Condition="'$(WindowsAppSDKBootstrapAutoInitializeOptions_OnError_FailFast)'=='true'">MICROSOFT_WINDOWSAPPSDK_BOOTSTRAP_AUTO_INITIALIZE_OPTIONS_ONERROR_FAILFAST;%(PreprocessorDefinitions)</PreprocessorDefinitions>
-                <PreprocessorDefinitions Condition="'$(WindowsAppSDKBootstrapAutoInitializeOptions_OnNoMatch_ShowUI)'=='true'">MICROSOFT_WINDOWSAPPSDK_BOOTSTRAP_AUTO_INITIALIZE_OPTIONS_ONNOMATCH_SHOWUI;%(PreprocessorDefinitions)</PreprocessorDefinitions>
-                <PreprocessorDefinitions Condition="'$(WindowsAppSDKBootstrapAutoInitializeOptions_OnPackageIdentity_NoOp)'=='true'">MICROSOFT_WINDOWSAPPSDK_BOOTSTRAP_AUTO_INITIALIZE_OPTIONS_ONPACKAGEIDENTITY_NOOP;%(PreprocessorDefinitions)</PreprocessorDefinitions>
-                <PreprocessorDefinitions>%(PreprocessorDefinitions);MICROSOFT_WINDOWSAPPSDK_BOOTSTRAP_AUTO_INITIALIZE=1</PreprocessorDefinitions>
             </ClCompile>
         </ItemGroup>
     </Target>
diff --git a/build/NuSpecs/WindowsAppSDK-Nuget-Native.DeploymentManager.targets b/build/NuSpecs/WindowsAppSDK-Nuget-Native.DeploymentManager.targets
index cfbd8687c4..7ecd503811 100644
--- a/build/NuSpecs/WindowsAppSDK-Nuget-Native.DeploymentManager.targets
+++ b/build/NuSpecs/WindowsAppSDK-Nuget-Native.DeploymentManager.targets
@@ -1,12 +1,18 @@
 <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
 
+    <ItemDefinitionGroup>
+        <!-- Add the appropriate definition to the ClCompile ItemDefinitionGroup to apply to all compilations -->
+        <ClCompile>
+            <PreprocessorDefinitions Condition="'$(WindowsAppSDKDeploymentManagerAutoInitializeOptions_Default)'=='true'">MICROSOFT_WINDOWSAPPSDK_DEPLOYMENTMANAGER_AUTO_INITIALIZE_OPTIONS_DEFAULT;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+            <PreprocessorDefinitions Condition="'$(WindowsAppSDKDeploymentManagerAutoInitializeOptions_None)'=='true'">MICROSOFT_WINDOWSAPPSDK_DEPLOYMENTMANAGER_AUTO_INITIALIZE_OPTIONS_NONE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+            <PreprocessorDefinitions Condition="'$(WindowsAppSDKDeploymentManagerAutoInitializeOptions_OnErrorShowUI)'=='true'">MICROSOFT_WINDOWSAPPSDK_DEPLOYMENTMANAGER_AUTO_INITIALIZE_OPTIONS_ONERRORSHOWUI;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+        </ClCompile>
+    </ItemDefinitionGroup>
+
     <Target Name="GenerateDeploymentManagerCpp">
         <ItemGroup>
             <ClCompile Include="$(MSBuildThisFileDirectory)..\..\include\DeploymentManagerAutoInitializer.cpp">
                 <PrecompiledHeader>NotUsing</PrecompiledHeader>
-                <PreprocessorDefinitions Condition="'$(WindowsAppSDKDeploymentManagerAutoInitializeOptions_Default)'=='true'">MICROSOFT_WINDOWSAPPSDK_DEPLOYMENTMANAGER_AUTO_INITIALIZE_OPTIONS_DEFAULT;%(PreprocessorDefinitions)</PreprocessorDefinitions>
-                <PreprocessorDefinitions Condition="'$(WindowsAppSDKDeploymentManagerAutoInitializeOptions_None)'=='true'">MICROSOFT_WINDOWSAPPSDK_DEPLOYMENTMANAGER_AUTO_INITIALIZE_OPTIONS_NONE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
-                <PreprocessorDefinitions Condition="'$(WindowsAppSDKDeploymentManagerAutoInitializeOptions_OnErrorShowUI)'=='true'">MICROSOFT_WINDOWSAPPSDK_DEPLOYMENTMANAGER_AUTO_INITIALIZE_OPTIONS_ONERRORSHOWUI;%(PreprocessorDefinitions)</PreprocessorDefinitions>
             </ClCompile>
         </ItemGroup>
     </Target>
diff --git a/build/NuSpecs/WindowsAppSDK-Nuget-Native.UndockedRegFreeWinRT.targets b/build/NuSpecs/WindowsAppSDK-Nuget-Native.UndockedRegFreeWinRT.targets
index 10db792396..0558be2365 100644
--- a/build/NuSpecs/WindowsAppSDK-Nuget-Native.UndockedRegFreeWinRT.targets
+++ b/build/NuSpecs/WindowsAppSDK-Nuget-Native.UndockedRegFreeWinRT.targets
@@ -1,20 +1,17 @@
 <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
 
-    <Target Name="AddUndockedRegFreeWinRTCppDefines" BeforeTargets="ClCompile" Condition="'$(WindowsAppSdkUndockedRegFreeWinRTInitialize)' == 'true'">
-        <ItemGroup>
-            <ClCompile>
-                <PreprocessorDefinitions>MICROSOFT_WINDOWSAPPSDK_UNDOCKEDREGFREEWINRT_AUTO_INITIALIZE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
-                <PreprocessorDefinitions Condition="'$(WindowsAppSdkUndockedRegFreeWinRTInitializeLoadLibrary)' == 'true'">MICROSOFT_WINDOWSAPPSDK_UNDOCKEDREGFREEWINRT_AUTO_INITIALIZE_LOADLIBRARY;%(PreprocessorDefinitions)</PreprocessorDefinitions>
-            </ClCompile>
-        </ItemGroup>
-    </Target>
+    <ItemDefinitionGroup>
+        <!-- Add the appropriate definition to the ClCompile ItemDefinitionGroup to apply to all compilations -->
+        <ClCompile>
+            <PreprocessorDefinitions>MICROSOFT_WINDOWSAPPSDK_UNDOCKEDREGFREEWINRT_AUTO_INITIALIZE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+            <PreprocessorDefinitions Condition="'$(WindowsAppSdkUndockedRegFreeWinRTInitializeLoadLibrary)' == 'true'">MICROSOFT_WINDOWSAPPSDK_UNDOCKEDREGFREEWINRT_AUTO_INITIALIZE_LOADLIBRARY;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+        </ClCompile>
+    </ItemDefinitionGroup>
 
-    <Target Name="GenerateUndockedRegFreeWinRTCpp" Condition="'$(WindowsAppSdkUndockedRegFreeWinRTInitialize)' == 'true'">
+    <Target Name="GenerateUndockedRegFreeWinRTCpp">
         <ItemGroup>
             <ClCompile Include="$(MSBuildThisFileDirectory)..\..\include\UndockedRegFreeWinRT-AutoInitializer.cpp">
                 <PrecompiledHeader>NotUsing</PrecompiledHeader>
-                <PreprocessorDefinitions>MICROSOFT_WINDOWSAPPSDK_UNDOCKEDREGFREEWINRT_AUTO_INITIALIZE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
-                <PreprocessorDefinitions Condition="'$(WindowsAppSdkUndockedRegFreeWinRTInitializeLoadLibrary)' == 'true'">MICROSOFT_WINDOWSAPPSDK_UNDOCKEDREGFREEWINRT_AUTO_INITIALIZE_LOADLIBRARY;%(PreprocessorDefinitions)</PreprocessorDefinitions>
             </ClCompile>
         </ItemGroup>
     </Target>