diff --git a/CMakePresets.json b/CMakePresets.json
index 69bc7f1..b41e3a3 100644
--- a/CMakePresets.json
+++ b/CMakePresets.json
@@ -38,6 +38,15 @@
       "cacheVariables": { "DIRECTX_ARCH": "arm64" },
       "hidden": true
     },
+    {
+      "name": "ARM64EC",
+      "architecture": {
+        "value": "arm64ec",
+        "strategy": "external"
+      },
+      "cacheVariables": { "DIRECTX_ARCH": "arm64ec" },
+      "hidden": true
+    },
 
     {
       "name": "Debug",
@@ -180,6 +189,8 @@
     { "name": "x86-Release"  , "description": "MSVC for x86 (Release) with DX12", "inherits": [ "base", "x86", "Release", "MSVC" ] },
     { "name": "arm64-Debug"  , "description": "MSVC for ARM64 (Debug) with DX12", "inherits": [ "base", "ARM64", "Debug", "MSVC" ] },
     { "name": "arm64-Release", "description": "MSVC for ARM64 (Release) with DX12", "inherits": [ "base", "ARM64", "Release", "MSVC" ] },
+    { "name": "arm64ec-Debug"  , "description": "MSVC for ARM64EC (Debug) with DX12", "inherits": [ "base", "ARM64EC", "Debug", "MSVC" ], "environment": { "CXXFLAGS": "/arm64EC" }  },
+    { "name": "arm64ec-Release", "description": "MSVC for ARM64EC (Release) with DX12", "inherits": [ "base", "ARM64EC", "Release", "MSVC" ], "environment": { "CXXFLAGS": "/arm64EC" }  },
 
     { "name": "x64-Debug-UWP"    , "description": "MSVC for x64 (Debug) for UWP", "inherits": [ "base", "x64", "Debug", "MSVC", "UWP" ] },
     { "name": "x64-Release-UWP"  , "description": "MSVC for x64 (Release) for UWP", "inherits": [ "base", "x64", "Release", "MSVC", "UWP" ] },
diff --git a/build/DirectXMesh-GitHub-Test-Dev17.yml b/build/DirectXMesh-GitHub-Test-Dev17.yml
index 25cf8cd..536bc8c 100644
--- a/build/DirectXMesh-GitHub-Test-Dev17.yml
+++ b/build/DirectXMesh-GitHub-Test-Dev17.yml
@@ -152,9 +152,11 @@ jobs:
       configuration: Release
       msbuildArchitecture: x64
 
-- job: CMAKE_BUILD
-  displayName: 'CMake BUILD_TESTING=ON'
+- job: CMAKE_BUILD_X64
+  displayName: 'CMake for X64 BUILD_TESTING=ON'
   timeoutInMinutes: 60
+  workspace:
+    clean: all
   steps:
   - checkout: self
     clean: true
@@ -236,16 +238,70 @@ jobs:
     inputs:
       cwd: '$(Build.SourcesDirectory)'
       cmakeArgs: --build out/build/x64-Release-Clang -v
+
+- job: CMAKE_BUILD_ARM64
+  displayName: 'CMake for ARM64 BUILD_TESTING=ON'
+  timeoutInMinutes: 60
+  workspace:
+    clean: all
+  steps:
+  - checkout: self
+    clean: true
+    fetchTags: false
   - task: DeleteFiles@1
+    displayName: Delete files from Tests
     inputs:
-      Contents: 'out'
+      SourceFolder: Tests
+      Contents: '**'
+      RemoveSourceFolder: true
+      RemoveDotFiles: true
   - task: CmdLine@2
-    displayName: Switch compiler to ARM64
+    displayName: Fetch Tests
+    inputs:
+      script: git clone --quiet --no-tags https://%GITHUB_PAT%@github.com/walbourn/directxmeshtest.git Tests
+      workingDirectory: $(Build.SourcesDirectory)
+      failOnStderr: true
+  - task: CmdLine@2
+    displayName: Setup environment for CMake to use VS
     inputs:
       script: |
         call "$(VC_PATH)\Auxiliary\Build\vcvarsamd64_arm64.bat"
+        echo ##vso[task.setvariable variable=WindowsSdkVerBinPath;]%WindowsSdkVerBinPath%
+        echo ##vso[task.prependpath]%VSINSTALLDIR%Common7\IDE\CommonExtensions\Microsoft\CMake\Ninja
+        echo ##vso[task.prependpath]%VCINSTALLDIR%Tools\Llvm\x64\bin
+        echo ##vso[task.prependpath]%WindowsSdkBinPath%x64
+        echo ##vso[task.prependpath]%WindowsSdkVerBinPath%x64
+        echo ##vso[task.prependpath]%VCToolsInstallDir%bin\Hostx64\arm64
+        echo ##vso[task.setvariable variable=EXTERNAL_INCLUDE;]%EXTERNAL_INCLUDE%
+        echo ##vso[task.setvariable variable=INCLUDE;]%INCLUDE%
         echo ##vso[task.setvariable variable=LIB;]%LIB%
 
+  - task: CMake@1
+    displayName: CMake (MSVC; arm64-Debug) Config
+    inputs:
+      cwd: '$(Build.SourcesDirectory)'
+      cmakeArgs: --preset=arm64-Debug
+  - task: CMake@1
+    displayName: CMake (MSVC; arm64-Debug) Build
+    inputs:
+      cwd: '$(Build.SourcesDirectory)'
+      cmakeArgs: --build out/build/arm64-Debug -v
+  - task: DeleteFiles@1
+    inputs:
+      Contents: 'out'
+  - task: CMake@1
+    displayName: CMake (MSVC; arm64-Release) Config
+    inputs:
+      cwd: '$(Build.SourcesDirectory)'
+      cmakeArgs: --preset=arm64-Release
+  - task: CMake@1
+    displayName: CMake (MSVC; arm64-Release) Build
+    inputs:
+      cwd: '$(Build.SourcesDirectory)'
+      cmakeArgs: --build out/build/arm64-Release -v
+  - task: DeleteFiles@1
+    inputs:
+      Contents: 'out'
   - task: CMake@1
     displayName: CMake (clang/LLVM; arm64-Debug) Config
     inputs:
@@ -269,3 +325,29 @@ jobs:
     inputs:
       cwd: '$(Build.SourcesDirectory)'
       cmakeArgs: --build out/build/arm64-Release-Clang -v
+  - task: DeleteFiles@1
+    inputs:
+      Contents: 'out'
+  - task: CMake@1
+    displayName: CMake (MSVC; arm64ec-Debug) Config
+    inputs:
+      cwd: '$(Build.SourcesDirectory)'
+      cmakeArgs: --preset=arm64ec-Debug
+  - task: CMake@1
+    displayName: CMake (MSVC; arm64ec-Debug) Build
+    inputs:
+      cwd: '$(Build.SourcesDirectory)'
+      cmakeArgs: --build out/build/arm64ec-Debug -v
+  - task: DeleteFiles@1
+    inputs:
+      Contents: 'out'
+  - task: CMake@1
+    displayName: CMake (MSVC; arm64ec-Release) Config
+    inputs:
+      cwd: '$(Build.SourcesDirectory)'
+      cmakeArgs: --preset=arm64ec-Release
+  - task: CMake@1
+    displayName: CMake (MSVC; arm64ec-Release) Build
+    inputs:
+      cwd: '$(Build.SourcesDirectory)'
+      cmakeArgs: --build out/build/arm64ec-Release -v