diff --git a/build/BuildWindowsTask.cs b/build/BuildWindowsTask.cs
index 98f45d1..93c9bdc 100644
--- a/build/BuildWindowsTask.cs
+++ b/build/BuildWindowsTask.cs
@@ -9,10 +9,40 @@ public sealed class BuildWindowsTask : FrostingTask<BuildContext>
 
     public override void Run(BuildContext context)
     {
+        // Apply ARM64 compatibility patches to crunch source
+        ApplyArm64Patches(context);
+
         BuildForArchitecture(context, "x64", "windows-x64");
         BuildForArchitecture(context, "ARM64", "windows-arm64");
     }
 
+    private void ApplyArm64Patches(BuildContext context)
+    {
+        // Fix crn_core.h: Ensure WIN32 is defined when _WIN32 is defined (MSVC defines _WIN32, not WIN32)
+        context.ReplaceTextInFiles(
+            "crunch/crnlib/crn_core.h",
+            "// File: crn_core.h\r\n// See Copyright Notice and license at the end of inc/crnlib.h\r\n#pragma once",
+            "// File: crn_core.h\r\n// See Copyright Notice and license at the end of inc/crnlib.h\r\n#pragma once\r\n\r\n// Ensure WIN32 is defined when _WIN32 is defined (MSVC defines _WIN32, not WIN32)\r\n#if defined(_WIN32) && !defined(WIN32)\r\n#define WIN32 1\r\n#endif");
+
+        // Fix crn_core.h: Add ARM64 platform detection before x64 check
+        context.ReplaceTextInFiles(
+            "crunch/crnlib/crn_core.h",
+            "#define CRNLIB_PLATFORM_PC 1\r\n\r\n#if defined(_WIN64) || defined(__MINGW64__) || defined(_LP64) || defined(__LP64__)\r\n#define CRNLIB_PLATFORM_PC_X64 1",
+            "#define CRNLIB_PLATFORM_PC 1\r\n\r\n#if defined(_M_ARM64)\r\n// Windows ARM64\r\n#define CRNLIB_PLATFORM_PC_ARM64 1\r\n#define CRNLIB_64BIT_POINTERS 1\r\n#define CRNLIB_CPU_HAS_64BIT_REGISTERS 1\r\n#define CRNLIB_LITTLE_ENDIAN_CPU 1\r\n#elif defined(_WIN64) || defined(__MINGW64__) || defined(_LP64) || defined(__LP64__)\r\n#define CRNLIB_PLATFORM_PC_X64 1");
+
+        // Fix crn_core.h: Disable MSVC x86 intrinsics on ARM64
+        context.ReplaceTextInFiles(
+            "crunch/crnlib/crn_core.h",
+            "#if defined(_MSC_VER) || defined(__MINGW32__) || defined(__MINGW64__)\r\n#define CRNLIB_USE_MSVC_INTRINSICS 1\r\n#endif",
+            "#if defined(_MSC_VER) || defined(__MINGW32__) || defined(__MINGW64__)\r\n#if !defined(_M_ARM64)\r\n#define CRNLIB_USE_MSVC_INTRINSICS 1\r\n#endif\r\n#endif");
+
+        // Fix crn_atomics.h: Add ARM64 yield processor support
+        context.ReplaceTextInFiles(
+            "crunch/crnlib/crn_atomics.h",
+            "#if defined(__GNUC__) && CRNLIB_PLATFORM_PC\r\nextern __inline__ __attribute__((__always_inline__, __gnu_inline__)) void crnlib_yield_processor() {\r\n  __asm__ __volatile__(\"pause\");\r\n}\r\n#else\r\nCRNLIB_FORCE_INLINE void crnlib_yield_processor() {\r\n#if CRNLIB_USE_MSVC_INTRINSICS\r\n#if CRNLIB_PLATFORM_PC_X64\r\n  _mm_pause();\r\n#else\r\n  YieldProcessor();\r\n#endif\r\n#else\r\n// No implementation\r\n#endif\r\n}",
+            "#if defined(__GNUC__) && CRNLIB_PLATFORM_PC\r\nextern __inline__ __attribute__((__always_inline__, __gnu_inline__)) void crnlib_yield_processor() {\r\n#if defined(__aarch64__)\r\n  __asm__ __volatile__(\"yield\");\r\n#else\r\n  __asm__ __volatile__(\"pause\");\r\n#endif\r\n}\r\n#else\r\nCRNLIB_FORCE_INLINE void crnlib_yield_processor() {\r\n#if defined(_M_ARM64)\r\n  __yield();\r\n#elif CRNLIB_USE_MSVC_INTRINSICS\r\n#if CRNLIB_PLATFORM_PC_X64\r\n  _mm_pause();\r\n#else\r\n  YieldProcessor();\r\n#endif\r\n#else\r\n// No implementation\r\n#endif\r\n}");
+    }
+
     private void BuildForArchitecture(BuildContext context, string cmakeArch, string rid, string cmakeOptions = "")
     {
         var buildWorkingDir = $"crunch_build_{rid}";