diff --git a/.github/workflows/Windows.yml b/.github/workflows/Windows.yml
index 9a5d09153..460b248fe 100644
--- a/.github/workflows/Windows.yml
+++ b/.github/workflows/Windows.yml
@@ -21,13 +21,13 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - name: win2025-msvc-clang-repl-19
+          - name: win2025-shared-lib
             os: windows-2025
-            compiler: msvc
-            clang-runtime: '19'
+            compiler: clang
+            clang-runtime: '18'
             cling: Off
             llvm_enable_projects: "clang"
-            llvm_targets_to_build: "host;NVPTX"
+            llvm_targets_to_build: "host"
             
     steps:
     - uses: actions/checkout@v4
@@ -73,7 +73,7 @@ jobs:
         path: |
           llvm-project
           ${{ matrix.cling=='On' && 'cling' || '' }}
-        key: ${{ env.CLING_HASH }}-${{ runner.os }}-${{ matrix.os }}-${{ matrix.compiler }}-clang-${{ matrix.clang-runtime }}.x-patch-${{ hashFiles(format('patches/llvm/clang{0}-*.patch', matrix.clang-runtime)) || 'none' }}
+        key: ${{ env.CLING_HASH }}-${{ runner.os }}-${{ matrix.os }}-${{ matrix.compiler }}-clang-${{ matrix.clang-runtime }}.x-patch-${{ hashFiles(format('patches/llvm/clang{0}-*.patch', matrix.clang-runtime)) || 'none' }}-shared-lib
         lookup-only: true
 
     - name: Setup default Build Type on Windows
@@ -93,10 +93,10 @@ jobs:
           choco install llvm --version=$ver --no-progress -my
           clang --version
           #
-          $env:CC="clang"
-          $env:CXX="clang++"
-          echo "CC=clang" >> $env:GITHUB_ENV
-          echo "CXX=clang++" >> $env:GITHUB_ENV
+          $env:CC="clang-cl"
+          $env:CXX="clang-cl"
+          echo "CC=clang-cl" >> $env:GITHUB_ENV
+          echo "CXX=clang-cl" >> $env:GITHUB_ENV
         }
         elseif ( "${{ matrix.compiler }}" -imatch "msvc" )
         {
@@ -130,7 +130,7 @@ jobs:
         }
         else
         {
-          git clone --depth=1 -b release/${{ matrix.clang-runtime }}.x https://github.com/llvm/llvm-project.git
+          git clone --depth=1 -b llvm-export-api-20.0 https://github.com/fsfod/llvm-project.git
         }
 
         cd llvm-project
@@ -139,20 +139,24 @@ jobs:
         if ( "${{ matrix.cling }}" -imatch "On" )
         {
           cd build
-          cmake -DLLVM_ENABLE_PROJECTS="${{ matrix.llvm_enable_projects}}" `
+          cmake -G Ninja -DLLVM_ENABLE_PROJECTS="${{ matrix.llvm_enable_projects}}" `
                 -DLLVM_EXTERNAL_PROJECTS=cling                `
                 -DLLVM_EXTERNAL_CLING_SOURCE_DIR="$env:CLING_DIR"   `
                 -DLLVM_TARGETS_TO_BUILD="${{ matrix.llvm_targets_to_build }}" `
                 -DCMAKE_BUILD_TYPE=Release                         `
                 -DLLVM_ENABLE_ASSERTIONS=ON                        `
                 -DCLANG_ENABLE_STATIC_ANALYZER=OFF                 `
+                -DLLVM_ENABLE_PLUGINS=On                           `
                 -DCLANG_ENABLE_ARCMT=OFF                           `
                 -DCLANG_ENABLE_FORMAT=OFF                          `
                 -DCLANG_ENABLE_BOOTSTRAP=OFF                       `
                 -DLLVM_ENABLE_ZSTD=OFF                             `
                 -DLLVM_ENABLE_TERMINFO=OFF                         `
                 -DLLVM_ENABLE_LIBXML2=OFF                          `
-                ..\llvm
+                -DLLVM_BUILD_LLVM_DYLIB_VIS=On                     `
+                -DLLVM_DYLIB_COMPONENTS="BinaryFormat;Core;Object;OrcJit;Support;FrontendDriver;OrcDebugging;Coverage;FrontendHLSL;LTO;clangCodeGen;clangStaticAnalyzerCore"               `
+                -DLLVM_LINK_LLVM_DYLIB=On                          `
+                -DCLANG_LINK_CLANG_DYLIB=On -DCMAKE_ASM_MASM_COMPILER=llvm-ml -DCMAKE_ASM_MASM_FLAGS="-m64" ..\llvm
           cmake --build . --config Release --target clang --parallel ${{ env.ncpus }}
           cmake --build . --config Release --target cling --parallel ${{ env.ncpus }}
           # Now build gtest.a and gtest_main for CppInterOp to run its tests.
@@ -174,18 +178,19 @@ jobs:
           }
           cd build
           echo "Apply clang${{ matrix.clang-runtime }}-*.patch patches:"
-          cmake -DLLVM_ENABLE_PROJECTS="${{ matrix.llvm_enable_projects}}"                   `
+          cmake -G Ninja -DLLVM_ENABLE_PROJECTS="${{ matrix.llvm_enable_projects}}"                   `
                 -DLLVM_TARGETS_TO_BUILD="${{ matrix.llvm_targets_to_build }}"          `
-                -DCMAKE_BUILD_TYPE=Release                          `
-                -DLLVM_ENABLE_ASSERTIONS=ON                         `
+                -DCMAKE_BUILD_TYPE=Release           `
+                -DLLVM_ENABLE_ASSERTIONS=ON                        `
+                -DCMAKE_CXX_COMPILER=clang-cl               `
+                -DCMAKE_C_COMPILER=clang-cl                 `
                 -DCLANG_ENABLE_STATIC_ANALYZER=OFF                  `
                 -DCLANG_ENABLE_ARCMT=OFF                            `
-                -DCLANG_ENABLE_FORMAT=OFF                           `
-                -DCLANG_ENABLE_BOOTSTRAP=OFF                        `
-                -DLLVM_ENABLE_ZSTD=OFF                              `
-                -DLLVM_ENABLE_TERMINFO=OFF                          `
-                -DLLVM_ENABLE_LIBXML2=OFF                           `
-                ..\llvm
+                -DLLVM_ENABLE_PLUGINS=On                            `
+                -DLLVM_BUILD_LLVM_DYLIB_VIS=On                      `
+                -DLLVM_BUILD_LLVM_DYLIB=On                         `
+                -DLLVM_LINK_LLVM_DYLIB=On                           `
+                -DCLANG_LINK_CLANG_DYLIB=On -DCMAKE_ASM_MASM_COMPILER=llvm-ml -DCMAKE_ASM_MASM_FLAGS="-m64" ..\llvm
           cmake --build . --config Release --target clang clangInterpreter clangStaticAnalyzerCore --parallel ${{ env.ncpus }}
         }
         cd ..\
@@ -224,10 +229,10 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - name: win2025-msvc-clang-repl-19
+          - name: win2025-shared-lib
             os: windows-2025
-            compiler: msvc
-            clang-runtime: '19'
+            compiler: clang
+            clang-runtime: '18'
             cling: Off
             cppyy: Off
 
@@ -283,10 +288,10 @@ jobs:
           choco install llvm --version=$ver --no-progress -my
           clang --version
           #
-          $env:CC="clang"
-          $env:CXX="clang++"
-          echo "CC=clang" >> $env:GITHUB_ENV
-          echo "CXX=clang++" >> $env:GITHUB_ENV
+          $env:CC="clang-cl"
+          $env:CXX="clang-cl"
+          echo "CC=clang-cl" >> $env:GITHUB_ENV
+          echo "CXX=clang-cl" >> $env:GITHUB_ENV
         }
         elseif ( "${{ matrix.compiler }}" -imatch "msvc" )
         {
@@ -304,7 +309,7 @@ jobs:
         path: |
           llvm-project
           ${{ matrix.cling=='On' && 'cling' || '' }}
-        key: ${{ env.CLING_HASH }}-${{ runner.os }}-${{ matrix.os }}-${{ matrix.compiler }}-clang-${{ matrix.clang-runtime }}.x-patch-${{ hashFiles(format('patches/llvm/clang{0}-*.patch', matrix.clang-runtime)) || 'none' }}
+        key: ${{ env.CLING_HASH }}-${{ runner.os }}-${{ matrix.os }}-${{ matrix.compiler }}-clang-${{ matrix.clang-runtime }}.x-patch-${{ hashFiles(format('patches/llvm/clang{0}-*.patch', matrix.clang-runtime)) || 'none' }}-shared-lib
          
     - name: Build and Test/Install CppInterOp on Windows systems
       run: |
@@ -356,23 +361,28 @@ jobs:
         echo "CPPINTEROP_BUILD_DIR=$env:CPPINTEROP_BUILD_DIR" >> $env:GITHUB_ENV  
         if ( "${{ matrix.cling }}" -imatch "On" )
         {
-          cmake -DCMAKE_BUILD_TYPE=${{ env.BUILD_TYPE }}    `
+          cmake -G Ninja -DCMAKE_BUILD_TYPE=${{ env.BUILD_TYPE }}    `
                 -DUSE_CLING=ON                                  `
                 -DUSE_REPL=OFF                                  `
+                -DBUILD_SHARED_LIBS=ON                          `
                 -DCling_DIR="$env:LLVM_BUILD_DIR\tools\cling"   `
                 -DLLVM_DIR="$env:LLVM_BUILD_DIR" `
                 -DLLVM_ENABLE_WERROR=On                          `
+                -DLLVM_BUILD_LLVM_DYLIB_VIS=On -DLLVM_LINK_LLVM_DYLIB=On -DCLANG_LINK_CLANG_DYLIB=On -DDISABLE_LLVM_LINK_LLVM_DYLIB=On                           `
                 -DClang_DIR="$env:LLVM_BUILD_DIR"  -DCODE_COVERAGE=${{ env.CODE_COVERAGE }} -DCMAKE_INSTALL_PREFIX="$env:CPPINTEROP_DIR"  ..\
         }
         else
         {
-          cmake -DCMAKE_BUILD_TYPE=${{ env.BUILD_TYPE }}    `
+          cmake -G Ninja -DCMAKE_BUILD_TYPE=${{ env.BUILD_TYPE }}    `
                 -DLLVM_DIR="$env:LLVM_BUILD_DIR\lib\cmake\llvm"  `
                 -DLLVM_ENABLE_WERROR=On                          `
+                -DBUILD_SHARED_LIBS=ON                          `
+                -DLLVM_LINK_LLVM_DYLIB=On                           `
+                -DCLANG_LINK_CLANG_DYLIB=On                         `
                 -DClang_DIR="$env:LLVM_BUILD_DIR\lib\cmake\clang"  -DCODE_COVERAGE=${{ env.CODE_COVERAGE }}  -DCMAKE_INSTALL_PREFIX="$env:CPPINTEROP_DIR"  ..\
                 cmake --build . --config ${{ env.BUILD_TYPE }} --target googletest --parallel ${{ env.ncpus }}
         }
-        cmake --build . --config ${{ env.BUILD_TYPE }} --target check-cppinterop --parallel ${{ env.ncpus }}
+        cmake --build . --config ${{ env.BUILD_TYPE }} --target check-cppinterop 
 
     - name: Setup tmate session
       if: ${{ failure() && runner.debug }}
diff --git a/CMakeLists.txt b/CMakeLists.txt
index b27d0a762..582c2d03a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -67,14 +67,14 @@ include(GNUInstallDirs)
   ## Define supported version of clang and llvm
 
   set(CLANG_MIN_SUPPORTED 13.0)
-  set(CLANG_MAX_SUPPORTED "19.1.x")
-  set(CLANG_VERSION_UPPER_BOUND 20.0.0)
+  set(CLANG_MAX_SUPPORTED "20.1.x")
+  set(CLANG_VERSION_UPPER_BOUND 21.0.0)
   set(LLD_MIN_SUPPORTED 13.0)
-  set(LLD_MAX_SUPPORTED "19.1.x")
-  set(LLD_VERSION_UPPER_BOUND 20.0.0)
+  set(LLD_MAX_SUPPORTED "20.1.x")
+  set(LLD_VERSION_UPPER_BOUND 21.0.0)
   set(LLVM_MIN_SUPPORTED 13.0)
-  set(LLVM_MAX_SUPPORTED "19.1.x")
-  set(LLVM_VERSION_UPPER_BOUND 20.0.0)
+  set(LLVM_MAX_SUPPORTED "20.1.x")
+  set(LLVM_VERSION_UPPER_BOUND 21.0.0)
 
   ## Set Cmake packages search order
 
diff --git a/lib/Interpreter/CMakeLists.txt b/lib/Interpreter/CMakeLists.txt
index 933505691..c912d1e99 100644
--- a/lib/Interpreter/CMakeLists.txt
+++ b/lib/Interpreter/CMakeLists.txt
@@ -29,14 +29,16 @@ if(EMSCRIPTEN)
     PUBLIC "SHELL: -s WASM_BIGINT"
   )
 else()
-  set(LLVM_LINK_COMPONENTS
-    ${LLVM_TARGETS_TO_BUILD}
-    BinaryFormat
-    Core
-    Object
-    OrcJit
-    Support
-  )
+  IF(NOT WIN32)
+    set(LLVM_LINK_COMPONENTS
+      ${LLVM_TARGETS_TO_BUILD}
+      BinaryFormat
+      Core
+      Object
+      OrcJit
+      Support
+    )
+  endif()
   # FIXME: Investigate why this needs to be conditionally included.
   if ("LLVMFrontendDriver" IN_LIST LLVM_AVAILABLE_LIBS)
     list(APPEND LLVM_LINK_COMPONENTS  FrontendDriver)
@@ -77,7 +79,7 @@ else()
   if(NOT WIN32)
     list(APPEND link_libs dl)
   endif()
-
+    
   # Get rid of libLLVM-X.so which is appended to the list of static libraries.
   if (LLVM_LINK_LLVM_DYLIB)
     set(new_libs ${link_libs})
@@ -89,8 +91,10 @@ else()
           if (NOT transitive_libs)
             continue()
           endif()
+          string(REPLACE "version;" "" transitive_libs "${transitive_libs}")
           foreach(transitive_lib ${transitive_libs})
             get_target_property(lib_type ${transitive_lib} TYPE)
+            message(STATUS "lib_type ${lib_type}")
             if("${lib_type}" STREQUAL "STATIC_LIBRARY")
               list(APPEND static_transitive_libs ${transitive_lib})
             else()
@@ -124,8 +128,8 @@ else()
       clangStaticAnalyzerCore
       )
   endif(LLVM_LINK_LLVM_DYLIB)
-
-  add_llvm_library(clangCppInterOp
+  if(NOT WIN32)
+  llvm_add_library(clangCppInterOp
     DISABLE_LLVM_LINK_LLVM_DYLIB
     CppInterOp.cpp
     CXCppInterOp.cpp
@@ -133,6 +137,14 @@ else()
     LINK_LIBS
     ${link_libs}
   )
+  else()
+  llvm_add_library(clangCppInterOp
+    DISABLE_LLVM_LINK_LLVM_DYLIB
+    CppInterOp.cpp
+    CXCppInterOp.cpp
+    ${DLM}
+  )
+  endif()
 endif()
 
 string(REPLACE ";" "\;" _VER CPPINTEROP_VERSION)
diff --git a/unittests/CppInterOp/CUDATest.cpp b/unittests/CppInterOp/CUDATest.cpp
index ea171b46e..17bf80dff 100644
--- a/unittests/CppInterOp/CUDATest.cpp
+++ b/unittests/CppInterOp/CUDATest.cpp
@@ -46,18 +46,12 @@ TEST(DISABLED_CUDATest, Sanity) {
 #else
 TEST(CUDATest, Sanity) {
 #endif // CLANG_VERSION_MAJOR < 16
-#ifdef _WIN32
-  GTEST_SKIP() << "Disabled on Windows. Needs fixing.";
-#endif
   if (!HasCudaSDK())
     GTEST_SKIP() << "Skipping CUDA tests as CUDA SDK not found";
   EXPECT_TRUE(Cpp::CreateInterpreter({}, {"--cuda"}));
 }
 
 TEST(CUDATest, CUDAH) {
-#ifdef _WIN32
-  GTEST_SKIP() << "Disabled on Windows. Needs fixing.";
-#endif
   if (!HasCudaSDK())
     GTEST_SKIP() << "Skipping CUDA tests as CUDA SDK not found";
 
@@ -67,9 +61,6 @@ TEST(CUDATest, CUDAH) {
 }
 
 TEST(CUDATest, CUDARuntime) {
-#ifdef _WIN32
-  GTEST_SKIP() << "Disabled on Windows. Needs fixing.";
-#endif
   if (!HasCudaRuntime())
     GTEST_SKIP() << "Skipping CUDA tests as CUDA runtime not found";
 
diff --git a/unittests/CppInterOp/FunctionReflectionTest.cpp b/unittests/CppInterOp/FunctionReflectionTest.cpp
index efc1ca815..12b2ccd6d 100644
--- a/unittests/CppInterOp/FunctionReflectionTest.cpp
+++ b/unittests/CppInterOp/FunctionReflectionTest.cpp
@@ -800,9 +800,6 @@ TEST(FunctionReflectionTest, IsStaticMethod) {
 TEST(FunctionReflectionTest, GetFunctionAddress) {
   if (llvm::sys::RunningOnValgrind())
     GTEST_SKIP() << "XFAIL due to Valgrind report";
-#ifdef _WIN32
-  GTEST_SKIP() << "Disabled on Windows. Needs fixing.";
-#endif
   std::vector<Decl*> Decls, SubDecls;
   std::string code = "int f1(int i) { return i * i; }";
 
@@ -1129,9 +1126,6 @@ TEST(FunctionReflectionTest, GetFunctionArgDefault) {
 TEST(FunctionReflectionTest, Construct) {
   if (llvm::sys::RunningOnValgrind())
     GTEST_SKIP() << "XFAIL due to Valgrind report";
-#ifdef _WIN32
-  GTEST_SKIP() << "Disabled on Windows. Needs fixing.";
-#endif
 
   Cpp::CreateInterpreter();
 
@@ -1170,10 +1164,6 @@ TEST(FunctionReflectionTest, Destruct) {
   if (llvm::sys::RunningOnValgrind())
     GTEST_SKIP() << "XFAIL due to Valgrind report";
 
-#ifdef _WIN32
-  GTEST_SKIP() << "Disabled on Windows. Needs fixing.";
-#endif
-
   Cpp::CreateInterpreter();
 
   Interp->declare(R"(
diff --git a/unittests/CppInterOp/InterpreterTest.cpp b/unittests/CppInterOp/InterpreterTest.cpp
index 22c5f0e99..5d72fe3cb 100644
--- a/unittests/CppInterOp/InterpreterTest.cpp
+++ b/unittests/CppInterOp/InterpreterTest.cpp
@@ -57,9 +57,6 @@ TEST(InterpreterTest, DebugFlag) {
 }
 
 TEST(InterpreterTest, Evaluate) {
-#ifdef _WIN32
-  GTEST_SKIP() << "Disabled on Windows. Needs fixing.";
-#endif
   if (llvm::sys::RunningOnValgrind())
     GTEST_SKIP() << "XFAIL due to Valgrind report";
   //  EXPECT_TRUE(Cpp::Evaluate(I, "") == 0);
@@ -76,9 +73,6 @@ TEST(InterpreterTest, Evaluate) {
 }
 
 TEST(InterpreterTest, Process) {
-#ifdef _WIN32
-  GTEST_SKIP() << "Disabled on Windows. Needs fixing.";
-#endif
   if (llvm::sys::RunningOnValgrind())
     GTEST_SKIP() << "XFAIL due to Valgrind report";
   Cpp::CreateInterpreter();
@@ -128,9 +122,6 @@ TEST(InterpreterTest, DetectResourceDir) {
 #else
 TEST(InterpreterTest, DISABLED_DetectResourceDir) {
 #endif // LLVM_BINARY_DIR
-#ifdef _WIN32
-  GTEST_SKIP() << "Disabled on Windows. Needs fixing.";
-#endif
   Cpp::CreateInterpreter();
   EXPECT_STRNE(Cpp::DetectResourceDir().c_str(), Cpp::GetResourceDir());
   llvm::SmallString<256> Clang(LLVM_BINARY_DIR);
@@ -140,9 +131,6 @@ TEST(InterpreterTest, DISABLED_DetectResourceDir) {
 }
 
 TEST(InterpreterTest, DetectSystemCompilerIncludePaths) {
-#ifdef _WIN32
-  GTEST_SKIP() << "Disabled on Windows. Needs fixing.";
-#endif
   std::vector<std::string> includes;
   Cpp::DetectSystemCompilerIncludePaths(includes);
   EXPECT_FALSE(includes.empty());
diff --git a/unittests/CppInterOp/JitTest.cpp b/unittests/CppInterOp/JitTest.cpp
index 310f87efe..5d0e55d58 100644
--- a/unittests/CppInterOp/JitTest.cpp
+++ b/unittests/CppInterOp/JitTest.cpp
@@ -14,9 +14,6 @@ static int printf_jit(const char* format, ...) {
 TEST(JitTest, InsertOrReplaceJitSymbol) {
   if (llvm::sys::RunningOnValgrind())
     GTEST_SKIP() << "XFAIL due to Valgrind report";
-#ifdef _WIN32
-  GTEST_SKIP() << "Disabled on Windows. Needs fixing.";
-#endif
   std::vector<Decl*> Decls;
   std::string code = R"(
     extern "C" int printf(const char*,...);