diff --git a/CMakeLists.txt b/CMakeLists.txt
index 9517213..35c00b0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.14 FATAL_ERROR)
+cmake_minimum_required(VERSION 3.26 FATAL_ERROR)
 project(cxxmodules CXX)
 
 set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/lib")
@@ -6,21 +6,44 @@ set(CMAKE_LIBRARY_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/lib")
 set(CMAKE_RUNTIME_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/bin")
 
 set(CMAKE_CXX_STANDARD 20)
+set(CMAKE_CXX_EXTENSIONS NO)
+set(CMAKE_CXX_STANDARD_REQUIRED YES)
+set(CMAKE_CXX_SCAN_FOR_MODULES YES)
+
 # See #10.
 # set(CMAKE_CXX_VISIBILITY_PRESET hidden)
 
+set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API 2182bf5c-ef0d-489a-91da-49dbc3090d2a)
+set(CMake_TEST_CXXModules_UUID "a246741c-d067-4019-a8fb-3d16b0c9d1d3")
+
+if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+  set(CMAKE_EXPERIMENTAL_CXX_MODULE_DYNDEP 1)
+  set(CMAKE_EXPERIMENTAL_CXX_MODULE_MAP_FORMAT "clang")
+  set(CMAKE_EXE_LINKER_FLAGS -lstdc++)
+  # Workaround for C++Modules: Missing module map flags in exported compile commands
+  # see https://gitlab.kitware.com/cmake/cmake/-/issues/24618
+  set(CMAKE_CXX_COMPILE_OBJECT "${CMAKE_CXX_COMPILE_OBJECT} @<OBJECT>.modmap")
+
+elseif(CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
+  set(CMAKE_EXPERIMENTAL_CXX_MODULE_DYNDEP 1)
+
+endif()
+
 include(GenerateExportHeader)
-include(CTest)
+
+# include(CTest)
+enable_testing()
 
 add_subdirectory(simple)
 add_subdirectory(duplicates)
 add_subdirectory(duplicates-same-dir)
 add_subdirectory(link-use)
 add_subdirectory(link-use-mask)
-add_subdirectory(good-scanner)
+#TODO(CK): add_subdirectory(good-scanner)
 add_subdirectory(generated)
 
-add_subdirectory(partitions)
+# NOTE: This dit use of CXX_MODULE_INTERNAL_PARTITIONS?
+#FIXME: add_subdirectory(partitions)
 
-# The CMake APIs used here are not yet implemented.
-#add_subdirectory(header-units)
+# The CMake APIs used here are not yet implemented!
+# add_subdirectory(header-units)
diff --git a/generated/CMakeLists.txt b/generated/CMakeLists.txt
index 821ce6c..f9eacb3 100644
--- a/generated/CMakeLists.txt
+++ b/generated/CMakeLists.txt
@@ -10,13 +10,13 @@ function (generate name)
 endfunction ()
 
 generate(gen-export.mpp)
-generate(gen-import.mpp)
+generate(gen-import.cpp)
 
 add_executable(generated)
 target_sources(generated
     PRIVATE
-        "${CMAKE_CURRENT_BINARY_DIR}/gen-import.mpp"
-        use.mpp
+        "${CMAKE_CURRENT_BINARY_DIR}/gen-import.cpp"
+        use.cpp
     PRIVATE
         FILE_SET cxx_modules TYPE CXX_MODULES
         BASE_DIRS
diff --git a/generated/gen-import.mpp.in b/generated/gen-import.cpp.in
similarity index 100%
rename from generated/gen-import.mpp.in
rename to generated/gen-import.cpp.in
diff --git a/generated/use.mpp b/generated/use.cpp
similarity index 100%
rename from generated/use.mpp
rename to generated/use.cpp
diff --git a/link-use-mask/CMakeLists.txt b/link-use-mask/CMakeLists.txt
index b656995..dfc8752 100644
--- a/link-use-mask/CMakeLists.txt
+++ b/link-use-mask/CMakeLists.txt
@@ -1,5 +1,5 @@
 add_executable(link-use-mask
-    use.mpp)
+    use.cpp)
 # Should use "simple"'s `M` module since it is first in the link list.
 target_link_libraries(link-use-mask
     PRIVATE
@@ -8,7 +8,7 @@ target_link_libraries(link-use-mask
 add_test(NAME link-use-mask COMMAND link-use-mask)
 
 add_executable(link-use-mask-reverse
-    use.mpp)
+    use.cpp)
 # Should use "duplicate"'s `M` module since it is first in the link list.
 target_link_libraries(link-use-mask-reverse
     PRIVATE
diff --git a/link-use-mask/use.mpp b/link-use-mask/use.cpp
similarity index 100%
rename from link-use-mask/use.mpp
rename to link-use-mask/use.cpp
diff --git a/link-use/CMakeLists.txt b/link-use/CMakeLists.txt
index dcbab51..88224a4 100644
--- a/link-use/CMakeLists.txt
+++ b/link-use/CMakeLists.txt
@@ -1,5 +1,5 @@
 add_executable(link-use
-    use.mpp)
+    use.cpp)
 target_link_libraries(link-use
     PRIVATE
         simple)
diff --git a/link-use/use.mpp b/link-use/use.cpp
similarity index 100%
rename from link-use/use.mpp
rename to link-use/use.cpp
diff --git a/partitions/CMakeLists.txt b/partitions/CMakeLists.txt
index 07c2d08..0313990 100644
--- a/partitions/CMakeLists.txt
+++ b/partitions/CMakeLists.txt
@@ -4,6 +4,5 @@ target_sources(partitions
         FILE_SET cxx_modules TYPE CXX_MODULES FILES
             module.mpp
             parta.mpp
-        FILE_SET cxx_module_internal_partitions TYPE CXX_MODULE_INTERNAL_PARTITIONS FILES
             partb.mpp
             impl.mpp)
diff --git a/simple/CMakeLists.txt b/simple/CMakeLists.txt
index aa9afde..b84ca87 100644
--- a/simple/CMakeLists.txt
+++ b/simple/CMakeLists.txt
@@ -2,8 +2,8 @@ add_library(simple)
 generate_export_header(simple)
 target_sources(simple
     PRIVATE
-        use.mpp
-    PRIVATE
+        use.cpp
+    PUBLIC
         FILE_SET headers TYPE HEADERS
         BASE_DIRS
             "${CMAKE_CURRENT_BINARY_DIR}"
diff --git a/simple/use.mpp b/simple/use.cpp
similarity index 100%
rename from simple/use.mpp
rename to simple/use.cpp