diff --git a/.github/workflows/ci_tests.yml b/.github/workflows/ci_tests.yml
index d6b9c64f..351cb387 100644
--- a/.github/workflows/ci_tests.yml
+++ b/.github/workflows/ci_tests.yml
@@ -40,9 +40,9 @@ jobs:
                   "tests": [
                     { "stdlibs": ["libstdc++"],
                       "tests": [
-                        "Debug.Default", "Release.Default",
-                        "Release.MaxSan", "Debug.Werror",
-                        "Debug.Dynamic", "Debug.Coverage"
+                        "Debug.Default", "Debug.Coverage",
+                        "Debug.MaxSan", "Debug.Werror",
+                        "Release.Default", "Release.Dynamic"
                       ]
                     }
                   ]
@@ -67,8 +67,8 @@ jobs:
                   "tests": [
                     { "stdlibs": ["libc++"],
                       "tests": [
-                        "Debug.Default", "Release.Default", "Release.MaxSan",
-                        "Debug.Dynamic"
+                        "Debug.Default", "Debug.MaxSan",
+                        "Release.Default", "Release.Dynamic"
                       ]
                     }
                   ]
@@ -96,7 +96,10 @@ jobs:
                 { "cxxversions": ["c++23"],
                   "tests": [
                     { "stdlibs": ["stl"],
-                      "tests": ["Debug.Default", "Release.Default", "Release.MaxSan"]
+                      "tests": [
+                        "Debug.Default", "Debug.MaxSan",
+                        "Release.Default", "Release.Dynamic"
+                      ]
                     }
                   ]
                 }
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 095c67d2..99c13228 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -21,40 +21,45 @@ set(TARGETS_EXPORT_NAME ${PROJECT_NAME}-targets) # NOTE: must be set, is importa
 
 #===============================================================================
 if(BEMAN_USE_MODULES)
+    set(CMAKE_CXX_SCAN_FOR_MODULES ON)
     set(CMAKE_CXX_VISIBILITY_PRESET hidden)
-    set(CMAKE_VISIBILITY_INLINES_HIDDEN TRUE)
+    set(CMAKE_VISIBILITY_INLINES_HIDDEN ON)
+
+    find_package(Threads REQUIRED)
 
     # CMake requires the language standard to be specified as compile feature
     # when a target provides C++23 modules and the target will be installed
-    add_library(beman.execution STATIC)
-    add_library(beman::execution ALIAS beman.execution)
+    add_library(${TARGET_PREFIX} STATIC)
+    add_library(beman::execution ALIAS ${TARGET_PREFIX})
     target_compile_features(
-        beman.execution
+        ${TARGET_PREFIX}
         PUBLIC cxx_std_${CMAKE_CXX_STANDARD}
     )
 
     include(GenerateExportHeader)
-
     generate_export_header(
-        beman.execution
-        BASE_NAME beman.execution
+        ${TARGET_PREFIX}
+        BASE_NAME ${TARGET_PREFIX}
         EXPORT_FILE_NAME beman/execution/modules_export.hpp
     )
     target_sources(
-        beman.execution
+        ${TARGET_PREFIX}
         PUBLIC
             FILE_SET HEADERS
                 BASE_DIRS include ${CMAKE_CURRENT_BINARY_DIR}
                 FILES
                     ${CMAKE_CURRENT_BINARY_DIR}/beman/execution/modules_export.hpp
     )
-    # FIXME: target_compile_definitions(beman.execution PUBLIC BEMAN_HAS_MODULES)
+    target_compile_definitions(${TARGET_PREFIX} PUBLIC BEMAN_HAS_MODULES)
+    target_link_libraries(${TARGET_PREFIX} PUBLIC Threads::Threads)
+else()
+    set(CMAKE_CXX_SCAN_FOR_MODULES OFF)
 endif()
 
 if(BEMAN_USE_MODULES AND CMAKE_CXX_MODULE_STD)
-    target_compile_definitions(beman.execution PUBLIC BEMAN_HAS_IMPORT_STD)
-else()
-    message(WARNING "Missing support for CMAKE_CXX_MODULE_STD!")
+    target_compile_definitions(${TARGET_PREFIX} PUBLIC BEMAN_HAS_IMPORT_STD)
+elseif(BEMAN_USE_MODULES)
+    message(WARNING "Missing or disabled support for CMAKE_CXX_MODULE_STD!")
 endif()
 #===============================================================================
 
@@ -72,13 +77,19 @@ option(
 
 add_subdirectory(src/beman/execution)
 
+#===============================================================================
 # NOTE: this must be done before tests! CK
-include(./cmake/beman-install-library-config.cmake)
-beman_install_library(${TARGET_PREFIX} headers)
+include(./cmake/beman-install-library.cmake)
+beman_install_library(${TARGET_PREFIX} TARGETS ${TARGET_NAME} ${TARGET_PREFIX}
+    # FIXME: DEPENDENCIES [===[beman.inplace_vector 1.0.0]===] [===[beman.scope 0.0.1 EXACT]===] fmt
+    # TODO(CK): XXX OR XXX DEPENDENCIES "beman.inplace_vector 1.0.0;beman.scope 0.0.1 EXACT"
+    DEPENDENCIES Threads
+)
+#===============================================================================
 
-if(BEMAN_EXECUTION_ENABLE_TESTING)
-    enable_testing()
+enable_testing()
 
+if(BEMAN_EXECUTION_ENABLE_TESTING)
     add_subdirectory(tests/beman/execution)
 endif()
 
diff --git a/CMakePresets.json b/CMakePresets.json
index 5bc75f84..eccfd3f6 100644
--- a/CMakePresets.json
+++ b/CMakePresets.json
@@ -7,9 +7,9 @@
       "generator": "Ninja",
       "binaryDir": "${sourceDir}/build/${presetName}",
       "cacheVariables": {
+        "BEMAN_USE_MODULES": true,
         "CMAKE_CXX_STANDARD": "23",
         "CMAKE_CXX_EXTENSIONS": true,
-        "CMAKE_CXX_SCAN_FOR_MODULES": true,
         "CMAKE_CXX_STANDARD_REQUIRED": true,
         "CMAKE_EXPORT_COMPILE_COMMANDS": true,
         "CMAKE_SKIP_TEST_ALL_DEPENDENCY": false,
@@ -19,6 +19,17 @@
     {
       "name": "_debug-base",
       "hidden": true,
+      "warnings": {
+        "dev": true,
+        "deprecated": true,
+        "uninitialized": true,
+        "unusedCli": true,
+        "systemVars": false
+      },
+      "errors": {
+        "dev": false,
+        "deprecated": false
+      },
       "cacheVariables": {
         "CMAKE_BUILD_TYPE": "Debug",
         "BEMAN_BUILDSYS_SANITIZER": "MaxSan"
@@ -62,6 +73,10 @@
       ],
       "cacheVariables": {
         "CMAKE_TOOLCHAIN_FILE": "infra/cmake/llvm-libc++-toolchain.cmake"
+      },
+      "environment": {
+        "CXX": "clang++",
+        "CMAKE_CXX_FLAGS": "-stdlib=libc++"
       }
     },
     {
@@ -73,6 +88,10 @@
       ],
       "cacheVariables": {
         "CMAKE_TOOLCHAIN_FILE": "infra/cmake/llvm-libc++-toolchain.cmake"
+      },
+      "environment": {
+        "CXX": "clang++",
+        "CMAKE_CXX_FLAGS": "-stdlib=libc++"
       }
     },
     {
@@ -83,7 +102,7 @@
         "_debug-base"
       ],
       "cacheVariables": {
-        "CMAKE_CXX_SCAN_FOR_MODULES": false,
+        "BEMAN_USE_MODULES": false,
         "CMAKE_TOOLCHAIN_FILE": "infra/cmake/appleclang-toolchain.cmake"
       }
     },
@@ -95,7 +114,7 @@
         "_release-base"
       ],
       "cacheVariables": {
-        "CMAKE_CXX_SCAN_FOR_MODULES": false,
+        "BEMAN_USE_MODULES": false,
         "CMAKE_TOOLCHAIN_FILE": "infra/cmake/appleclang-toolchain.cmake"
       }
     },
diff --git a/Makefile b/Makefile
index 6549b0d8..a2dd4e7e 100644
--- a/Makefile
+++ b/Makefile
@@ -14,7 +14,7 @@ SANITIZERS := run
 #     SANITIZERS += asan # TODO: tsan msan
 # endif
 
-.PHONY: default release debug doc run update check ce todo distclean clean codespell clang-tidy build test install all format unstage $(SANITIZERS) module build-module test-module
+.PHONY: default release debug doc run update check ce todo distclean clean codespell clang-tidy build test install all format unstage $(SANITIZERS) module build-module test-module build-interface
 
 SYSROOT   ?=
 TOOLCHAIN ?=
@@ -28,6 +28,9 @@ ifeq ($(CXX_BASE),clang++)
     COMPILER=clang++
 endif
 
+# NOTE default gmake use this flags!
+# COMPILE.cc = $(CXX) $(CXXFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c
+# LINK.cc = $(CXX) $(CXXFLAGS) $(CPPFLAGS) $(LDFLAGS) $(TARGET_ARCH)
 LDFLAGS   ?=
 SAN_FLAGS ?=
 CXX_FLAGS ?= -g
@@ -56,7 +59,8 @@ ifeq (${hostSystemName},Darwin)
   #  export GCC_DIR:=$(shell realpath ${GCC_PREFIX})
 
   # XXX export CMAKE_CXX_STDLIB_MODULES_JSON=${GCC_DIR}/lib/gcc/current/libstdc++.modules.json
-  ifeq ($(CXX),)
+  ifeq ($(origin CXX),default)
+    $(info CXX is using the built-in default: $(CXX))
     export CXX=g++-15
     export CXXFLAGS=-stdlib=libstdc++
   endif
@@ -99,7 +103,7 @@ endif
 # TODO: beman.execution.examples.modules
 # FIXME: beman.execution.execution-module.test beman.execution.stop-token-module.test
 
-default: release
+default: module
 
 all: $(SANITIZERS)
 
@@ -116,19 +120,21 @@ doc:
 # ==========================================================
 # NOTE: cmake configure to only test without modules! CK
 # ==========================================================
-build:
+build build-interface:
 	cmake -G Ninja -S $(SOURCEDIR) -B $(BUILD) $(TOOLCHAIN) $(SYSROOT) \
 	  -D CMAKE_EXPORT_COMPILE_COMMANDS=ON \
 	  -D CMAKE_SKIP_INSTALL_RULES=ON \
 	  -D CMAKE_CXX_STANDARD=23 \
 	  -D CMAKE_CXX_EXTENSIONS=ON \
 	  -D CMAKE_CXX_STANDARD_REQUIRED=ON \
-	  -D CMAKE_CXX_SCAN_FOR_MODULES=OFF \
 	  -D BEMAN_USE_MODULES=OFF \
+	  -D BEMAN_USE_STD_MODULE=OFF \
 	  -D CMAKE_BUILD_TYPE=Release \
-	  -D CMAKE_CXX_COMPILER=$(CXX) --log-level=VERBOSE
-	cmake --build $(BUILD)
-# XXX --fresh -D CMAKE_CXX_FLAGS="$(CXX_FLAGS) $(SAN_FLAGS)"
+	  -D CMAKE_SKIP_TEST_ALL_DEPENDENCY=OFF \
+	  -D CMAKE_CXX_COMPILER=$(CXX) --log-level=VERBOSE --fresh
+	# XXX -D CMAKE_CXX_FLAGS="$(CXX_FLAGS) $(SAN_FLAGS)"
+	cmake --build $(BUILD) --target all_verify_interface_header_sets
+	cmake --build $(BUILD) --target all
 
 # NOTE: without install, see CMAKE_SKIP_INSTALL_RULES! CK
 test: build
@@ -137,12 +143,14 @@ test: build
 module build-module:
 	cmake -G Ninja -S $(SOURCEDIR) -B $(BUILD) $(TOOLCHAIN) $(SYSROOT) \
 	  -D CMAKE_EXPORT_COMPILE_COMMANDS=ON \
-	  -D CMAKE_SKIP_INSTALL_RULES=ON \
+	  -D CMAKE_SKIP_INSTALL_RULES=OFF \
 	  -D CMAKE_CXX_STANDARD=23 \
 	  -D CMAKE_CXX_EXTENSIONS=ON \
 	  -D CMAKE_CXX_STANDARD_REQUIRED=ON \
-	  -D CMAKE_CXX_SCAN_FOR_MODULES=ON \
 	  -D BEMAN_USE_MODULES=ON \
+	  -D BEMAN_USE_STD_MODULE=ON \
+	  -D CMAKE_BUILD_TYPE=Release \
+	  -D CMAKE_INSTALL_MESSAGE=LAZY \
 	  -D CMAKE_BUILD_TYPE=Release \
 	  -D CMAKE_CXX_COMPILER=$(CXX) --log-level=VERBOSE
 	cmake --build $(BUILD)
diff --git a/cmake/Config.cmake.in b/cmake/Config.cmake.in
new file mode 100644
index 00000000..81adf800
--- /dev/null
+++ b/cmake/Config.cmake.in
@@ -0,0 +1,12 @@
+# cmake/Config.cmake.in -*-makefile-*-
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+include(CMakeFindDependencyMacro)
+
+@BEMAN_FIND_DEPENDENCIES@
+
+@PACKAGE_INIT@
+
+include(${CMAKE_CURRENT_LIST_DIR}/@PROJECT_NAME@-targets.cmake)
+
+check_required_components(@PROJECT_NAME@)
diff --git a/cmake/README.md b/cmake/README.md
new file mode 100644
index 00000000..6c7e2723
--- /dev/null
+++ b/cmake/README.md
@@ -0,0 +1,388 @@
+<!-- SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception -->
+
+# CMake Support for Header-Only Libraries and C++ Modules
+
+This directory provides a small set of CMake helper modules that make it easier
+to **build and install a library that works both with and without C++20
+modules**.
+
+The helpers wrap CMake’s evolving support for `FILE_SET CXX_MODULE` and package
+installation so that:
+
+- consumers can use the library in **classic header-only mode**, or
+
+- consumers with a compatible toolchain can use **C++ modules**, including
+  optional `import std;` support.
+
+The goal is to keep project `CMakeLists.txt` files readable while hiding most of
+the platform- and compiler-specific complexity.
+
+---
+
+## Motivation
+
+Today, supporting C++ modules often requires duplicating targets and custom
+install logic:
+
+- one target for headers only,
+- another target that owns module interface units,
+- conditional logic depending on compiler and CMake version,
+- non-trivial install/export rules.
+
+The helpers in this directory centralize that logic and provide a single,
+consistent API for projects that want to offer both usage models.
+
+---
+
+## Provided CMake Modules
+
+The following modules are expected to live in `infra/cmake`:
+
+- `prelude.cmake`
+  Common project setup and option handling.
+
+- `cxx-modules-rules.cmake`
+  Compiler and CMake feature checks related to C++ modules.
+
+- `beman-install-library.cmake`
+  High-level helper to install libraries, headers, module interface units, and CMake package files.
+
+- `Config.cmake.in`
+  Template used to generate the `<package>-config.cmake` file for consumers.
+
+---
+
+## New Configuration Options
+
+    * BEMAN_USE_MODULES:BOOL=ON
+    * BEMAN_USE_STD_MODULE:BOOL=OFF
+    * BEMAN_HAS_IMPORT_STD::BOOL=${CMAKE_CXX_SCAN_FOR_MODULES} # only if toolchain supports it.
+
+### The recommended usage in CMake code
+
+```cmake
+if(CMAKE_CXX_STANDARD GREATER_EQUAL 20)
+    option(BEMAN_USE_MODULES "Build CXX_MODULES" ${CMAKE_CXX_SCAN_FOR_MODULES})
+endif()
+if(BEMAN_USE_MODULES)
+    target_compile_definitions(beman.execution PUBLIC BEMAN_HAS_MODULES)
+endif()
+
+BEMAN_USE_STD_MODULE:BOOL=ON
+# -> "Check if 'import std;' is possible with the toolchain?"
+
+if(BEMAN_USE_MODULES AND CMAKE_CXX_MODULE_STD)
+    target_compile_definitions(beman.execution PUBLIC BEMAN_HAS_IMPORT_STD)
+endif()
+```
+
+Typical projects will only toggle `BEMAN_USE_MODULES`; the remaining options are
+detected automatically.
+
+---
+
+## Installing a Library
+
+Installation is handled by the `beman_install_library()` helper.
+
+### Function Signature
+
+```cmake
+beman_install_library(name
+    TARGETS <target1> [<target2> ...]
+    [DEPENDENCIES <dep1> [<dep2> ...]]
+    [NAMESPACE <namespace>]
+    [EXPORT_NAME <export-name>]
+    [DESTINATION <module-destination>]
+)
+```
+
+### Arguments
+
+- **name**
+  Logical package name (e.g. "beman.utility").
+  Used to derive config file names and cache variable prefixes.
+
+- **TARGETS**
+  Targets to install and export.
+
+- **DEPENDENCIES (optional)**
+  Semicolon-separated list, one dependency per entry.
+  Each entry is a valid `find_dependency()` argument list.
+
+  **NOTE:** you must use the bracket form for quoting if not only a package name is used!
+
+  `"[===[beman.inplace_vector 1.0.0]===] [===[beman.scope 0.0.1 EXACT]===] fmt"`
+
+- **NAMESPACE (optional)**
+  Namespace for imported targets.
+  Defaults to "beman::".
+
+- **EXPORT_NAME (optional)**
+  Name of the generated CMake export set.
+  Defaults to "<name>-targets".
+
+- **DESTINATION (optional)**
+  Installation directory for C++ module interface units.
+  Defaults to `${CMAKE_INSTALL_INCLUDEDIR}/beman/modules`.
+
+This function installs the specified project TARGETS and its `FILE_SET
+TYPE HEADERS` to the default CMAKE install destination.
+
+It also handles the installation of the CMake config package files if
+needed.  If the given targets has `FILE_SET TYPE CXX_MODULE`, it will also
+installed to the given DESTINATION
+
+- ***Used Cache variables**
+
+`BEMAN_INSTALL_CONFIG_FILE_PACKAGES`
+  List of package names for which config files should be installed.
+
+`<PREFIX>_INSTALL_CONFIG_FILE_PACKAGE`
+  Per-package override to enable/disable config file installation.
+  <PREFIX> is the uppercased package name with dots replaced by underscores.
+
+### Caveats
+
+**Only one `FILE_SET of each TYPE` is supported to install with this function yet!**
+
+---
+
+## The possible usage in CMakeLists.txt
+
+```cmake
+cmake_minimum_required(VERSION 3.30...4.2)
+
+include(./cmake/prelude.cmake)
+project(beman.execution VERSION 0.2.0 LANGUAGES CXX)
+include(./cmake/cxx-modules-rules.cmake)
+
+set(TARGET_PREFIX ${PROJECT_NAME})
+
+#===============================================================================
+if(BEMAN_USE_MODULES)
+    set(CMAKE_CXX_VISIBILITY_PRESET hidden)
+    set(CMAKE_VISIBILITY_INLINES_HIDDEN TRUE)
+
+    # CMake requires the language standard to be specified as compile feature
+    # when a target provides C++23 modules and the target will be installed
+    add_library(${TARGET_PREFIX} STATIC)
+    add_library(beman::execution ALIAS ${TARGET_PREFIX})
+    target_compile_features(
+        ${TARGET_PREFIX}
+        PUBLIC cxx_std_${CMAKE_CXX_STANDARD}
+    )
+
+    include(GenerateExportHeader)
+    generate_export_header(
+        ${TARGET_PREFIX}
+        BASE_NAME ${TARGET_PREFIX}
+        EXPORT_FILE_NAME beman/execution/modules_export.hpp
+    )
+    target_sources(
+        ${TARGET_PREFIX}
+        PUBLIC
+            FILE_SET HEADERS
+                BASE_DIRS include ${CMAKE_CURRENT_BINARY_DIR}
+                FILES
+                    ${CMAKE_CURRENT_BINARY_DIR}/beman/execution/modules_export.hpp
+    )
+    target_compile_definitions(${TARGET_PREFIX} PUBLIC BEMAN_HAS_MODULES)
+endif()
+
+if(BEMAN_USE_MODULES AND CMAKE_CXX_MODULE_STD)
+    target_compile_definitions(${TARGET_PREFIX} PUBLIC BEMAN_HAS_IMPORT_STD)
+else()
+    message(WARNING "Missing support for CMAKE_CXX_MODULE_STD!")
+endif()
+#===============================================================================
+
+# ...
+
+# NOTE: this must be done before tests! CK
+include(beman-install-library)
+beman_install_library(${PROJECT_NAME} TARGETS ${TARGET_PREFIX} beman.exemplar_headers #
+    # TODO(add): DEPENDENCIES [===[beman.inplace_vector 1.0.0]===] [===[beman.scope 0.0.1 EXACT]===] fmt
+)
+```
+
+---
+
+## Possible cmake config output
+
+**NOTE:** Exact output depend on the build host, used toolchain, and
+whether module support is enabled and supported.
+
+```bash
+bash-5.3$ make test-module
+cmake -G Ninja -S /Users/clausklein/Workspace/cpp/beman-project/execution26 -B build/Darwin/default   \
+	  -D CMAKE_EXPORT_COMPILE_COMMANDS=ON \
+	  -D CMAKE_SKIP_INSTALL_RULES=OFF \
+	  -D CMAKE_CXX_STANDARD=23 \
+	  -D CMAKE_CXX_EXTENSIONS=ON \
+	  -D CMAKE_CXX_STANDARD_REQUIRED=ON \
+	  -D CMAKE_CXX_SCAN_FOR_MODULES=ON \
+	  -D BEMAN_USE_MODULES=ON \
+	  -D CMAKE_BUILD_TYPE=Release \
+	  -D CMAKE_INSTALL_MESSAGE=LAZY \
+	  -D CMAKE_BUILD_TYPE=Release \
+	  -D CMAKE_CXX_COMPILER=clang++ --log-level=VERBOSE
+-- use ccache
+-- CXXFLAGS=-stdlib=libc++
+'brew' '--prefix' 'llvm'
+-- LLVM_DIR=/usr/local/Cellar/llvm/21.1.8
+-- CMAKE_CXX_STDLIB_MODULES_JSON=/usr/local/Cellar/llvm/21.1.8/lib/c++/libc++.modules.json
+-- CMAKE_CXX_IMPLICIT_INCLUDE_DIRECTORIES=/usr/local/Cellar/llvm/21.1.8/include/c++/v1;/usr/local/Cellar/llvm/21.1.8/lib/clang/21/include;/Library/Developer/CommandLineTools/SDKs/MacOSX14.sdk/usr/include
+-- CMAKE_CXX_STDLIB_MODULES_JSON=/usr/local/Cellar/llvm/21.1.8/lib/c++/libc++.modules.json
+-- BEMAN_USE_STD_MODULE=ON
+-- CMAKE_CXX_COMPILER_IMPORT_STD=23;26
+-- CMAKE_CXX_MODULE_STD=ON
+-- BEMAN_HAS_IMPORT_STD=ON
+-- BEMAN_USE_MODULES=ON
+-- CMAKE_CXX_SCAN_FOR_MODULES=ON
+-- Performing Test COMPILER_HAS_HIDDEN_VISIBILITY
+-- Performing Test COMPILER_HAS_HIDDEN_VISIBILITY - Success
+-- Performing Test COMPILER_HAS_HIDDEN_INLINE_VISIBILITY
+-- Performing Test COMPILER_HAS_HIDDEN_INLINE_VISIBILITY - Success
+-- Performing Test COMPILER_HAS_DEPRECATED_ATTR
+-- Performing Test COMPILER_HAS_DEPRECATED_ATTR - Success
+-- beman_install_library(beman.execution): COMPONENT execution_headers for TARGET 'beman.execution_headers'
+-- beman-install-library(beman.execution): 'beman.execution_headers' has INTERFACE_HEADER_SETS=public_headers
+-- beman_install_library(beman.execution): COMPONENT execution for TARGET 'beman.execution'
+-- beman-install-library(beman.execution): 'beman.execution' has INTERFACE_HEADER_SETS=HEADERS
+-- beman-install-library(beman.execution): 'beman.execution' has CXX_MODULE_SETS=CXX_MODULES
+-- Configuring done (3.1s)
+CMake Warning (dev) in CMakeLists.txt:
+  CMake's support for `import std;` in C++23 and newer is experimental.  It
+  is meant only for experimentation and feedback to CMake developers.
+This warning is for project developers.  Use -Wno-dev to suppress it.
+
+-- Generating done (0.4s)
+-- Build files have been written to: /Users/clausklein/Workspace/cpp/beman-project/execution26/build/Darwin/default
+bash-5.3$
+```
+
+---
+
+## Possible cmake export config package
+
+**NOTE:** Exact contents depend on the build host, used toolchain, and
+whether module support is enabled.
+
+```bash
+cmake --install build/Darwin/default --prefix $PWD/stagedir
+
+bash-5.3$ cd stagedir/
+bash-5.3$ tree lib/
+lib/
+├── cmake
+│   └── beman.execution
+│       ├── beman.execution-config-version.cmake
+│       ├── beman.execution-config.cmake
+│       ├── beman.execution-targets-debug.cmake
+│       ├── beman.execution-targets-relwithdebinfo.cmake
+│       ├── beman.execution-targets.cmake
+│       ├── bmi-GNU_Debug
+│       │   └── beman.execution.gcm
+│       ├── bmi-GNU_RelWithDebInfo
+│       │   └── beman.execution.gcm
+│       ├── cxx-modules
+│       │   ├── cxx-modules-beman.execution-Debug.cmake
+│       │   ├── cxx-modules-beman.execution-RelWithDebInfo.cmake
+│       │   ├── cxx-modules-beman.execution.cmake
+│       │   ├── target-execution-Debug.cmake
+│       │   └── target-execution-RelWithDebInfo.cmake
+│       └── modules
+│           └── execution.cppm
+├── libbeman.execution.a
+└── libbeman.execution_d.a
+
+7 directories, 15 files
+bash-5.3$
+```
+
+---
+
+## The recommended usage in implementation
+
+```cpp
+// identity.cppm
+module;
+
+#ifdef BEMAN_HAS_IMPORT_STD
+import std;
+#else
+#include <utility>
+#endif
+
+export module beman.exemplar;
+
+export namespace beman::exemplar {
+struct __is_transparent;
+
+struct identity {
+    template <class T>
+    constexpr T&& operator()(T&& t) const noexcept {
+        return std::forward<T>(t);
+    }
+
+    using is_transparent = __is_transparent;
+};
+} // namespace beman::exemplar
+```
+
+---
+
+## The possible usage in user code
+
+```cpp
+// example-usage.cpp
+
+#ifdef BEMAN_HAS_IMPORT_STD
+import std;
+#else
+#include <iostream>
+#endif
+
+#ifdef BEMAN_HAS_MODULES
+import beman.exemplar;
+#else
+#include <beman/exemplar/identity.hpp>
+#endif
+
+int main() {
+    beman::exemplar::identity id;
+
+    int x = 42;
+    int y = id(x); // y == 42
+
+    std::cout << y << '\n';
+    return 0;
+}
+```
+
+---
+
+## Notes on CMake and Modules
+
+- `FILE_SET CXX_MODULE` support is still evolving and depends on the compiler
+  and CMake version.
+
+- Not all toolchains support installing or consuming prebuilt module interface
+  units yet.
+
+- These helpers aim to provide a pragmatic, forward-compatible structure rather
+  than a final standard solution.
+
+---
+
+## Summary
+
+The helpers in this directory provide a structured way to:
+
+- build header-only and module-based libraries side by side,
+- hide compiler- and platform-specific complexity,
+- install and export targets in a consistent, consumer-friendly way.
+
+They are intended for projects that want to experiment with C++ modules today
+while remaining usable on traditional toolchains.
diff --git a/cmake/beman-install-library-config.cmake b/cmake/beman-install-library-config.cmake
deleted file mode 100644
index 4ad27ff2..00000000
--- a/cmake/beman-install-library-config.cmake
+++ /dev/null
@@ -1,251 +0,0 @@
-# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-include_guard(GLOBAL)
-
-# This file defines the function `beman_install_library` which is used to
-# install a library target and its headers, along with optional CMake
-# configuration files.
-#
-# The function is designed to be reusable across different Beman libraries.
-
-function(beman_install_library name interface)
-    # Usage
-    # -----
-    #
-    #     beman_install_library(NAME INTERFACE)
-    #
-    # Brief
-    # -----
-    #
-    # This function installs the specified library target and its headers.
-    # It also handles the installation of the CMake configuration files if needed.
-    #
-    # CMake variables
-    # ---------------
-    #
-    # Note that configuration of the installation is generally controlled by CMake
-    # cache variables so that they can be controlled by the user or tool running the
-    # `cmake` command. Neither `CMakeLists.txt` nor `*.cmake` files should set these
-    # variables directly.
-    #
-    # - BEMAN_INSTALL_CONFIG_FILE_PACKAGES:
-    #      List of packages that require config file installation.
-    #      If the package name is in this list, it will install the config file.
-    #
-    # - <PREFIX>_INSTALL_CONFIG_FILE_PACKAGE:
-    #      Boolean to control config file installation for the specific library.
-    #      The prefix `<PREFIX>` is the uppercased name of the library with dots
-    #      replaced by underscores.
-    #
-
-    # if(NOT TARGET "${name}")
-    #     message(FATAL_ERROR "Target '${name}' does not exist.")
-    # endif()
-
-    # if(NOT ARGN STREQUAL "")
-    #     message(
-    #         FATAL_ERROR
-    #         "beman_install_library does not accept extra arguments: ${ARGN}"
-    #     )
-    # endif()
-
-    # Given foo.bar, the component name is bar
-    string(REPLACE "." ";" name_parts "${name}")
-    # fail if the name doesn't look like foo.bar
-    list(LENGTH name_parts name_parts_length)
-    if(NOT name_parts_length EQUAL 2)
-        message(
-            FATAL_ERROR
-            "beman_install_library expects a name of the form 'beman.<name>', got '${name}'"
-        )
-    endif()
-
-    set(target_name "${name}")
-
-    # COMPONENT <component>
-    # Specify an installation component name with which the install rule is associated,
-    # such as Runtime or Development.
-    set(install_component_name "${name}") # TODO(CK): this is not common name!
-
-    set(export_name "${name}")
-    set(package_name "${name}")
-    list(GET name_parts -1 component_name)
-
-    include(GNUInstallDirs)
-
-    set(package_install_dir "${CMAKE_INSTALL_LIBDIR}/cmake/${package_name}")
-
-    set(target_list)
-    if(TARGET "${target_name}")
-        set_target_properties(
-            "${target_name}"
-            PROPERTIES EXPORT_NAME "${component_name}"
-        )
-        message(
-            VERBOSE
-            "beman-install-library: COMPONENT ${component_name} for TARGET '${target_name}'"
-        )
-        list(APPEND target_list "${target_name}")
-
-        get_target_property(
-            INTERFACE_CXX_MODULE_SETS
-            ${target_name}
-            INTERFACE_CXX_MODULE_SETS
-        )
-        if(INTERFACE_CXX_MODULE_SETS)
-            message(
-                VERBOSE
-                "beman-install-library: '${target_name}' has INTERFACE_CXX_MODULE_SETS=${INTERFACE_CXX_MODULE_SETS}"
-            )
-            set(__INSTALL_CXX_MODULES
-                FILE_SET
-                ${INTERFACE_CXX_MODULE_SETS}
-                DESTINATION
-                ${package_install_dir}/modules
-            )
-        endif()
-    endif()
-
-    if(interface AND TARGET "${target_name}_${interface}")
-        set_target_properties(
-            "${target_name}_${interface}"
-            PROPERTIES EXPORT_NAME "${component_name}_${interface}"
-        )
-        message(
-            VERBOSE
-            "beman-install-library: COMPONENT ${component_name} for TARGET '${name}_${interface}'"
-        )
-        list(APPEND target_list "${target_name}_${interface}")
-
-        get_target_property(
-            INTERFACE_HEADER_SETS
-            ${target_name}_${interface}
-            INTERFACE_HEADER_SETS
-        )
-        if(INTERFACE_HEADER_SETS)
-            message(
-                VERBOSE
-                "beman-install-library: '${target_name}_${interface}' has INTERFACE_HEADER_SETS=${INTERFACE_HEADER_SETS}"
-            )
-            set(__INSTALL_HEADER_SETS FILE_SET ${INTERFACE_HEADER_SETS})
-        endif()
-    endif()
-
-    if(CMAKE_SKIP_INSTALL_RULES)
-        message(
-            WARNING
-            "beman-install-library: not installing targets '${target_list}' due to CMAKE_SKIP_INSTALL_RULES"
-        )
-        return()
-    endif()
-
-    # ============================================================
-    install(
-        TARGETS ${target_list}
-        COMPONENT "${install_component_name}"
-        EXPORT "${export_name}"
-        FILE_SET HEADERS
-            ${__INSTALL_HEADER_SETS}
-            # FILE_SET CXX_MODULES
-            #     DESTINATION ${package_install_dir}/modules
-            ${__INSTALL_CXX_MODULES}
-        # There's currently no convention for this location
-        CXX_MODULES_BMI
-            DESTINATION
-                ${package_install_dir}/bmi-${CMAKE_CXX_COMPILER_ID}_$<CONFIG>
-    )
-    # ============================================================
-
-    # Determine the prefix for project-specific variables
-    string(TOUPPER "${name}" project_prefix)
-    string(REPLACE "." "_" project_prefix "${project_prefix}")
-
-    option(
-        ${project_prefix}_INSTALL_CONFIG_FILE_PACKAGE
-        "Enable creating and installing a CMake config-file package. Default: ON. Values: { ON, OFF }."
-        ON
-    )
-
-    # By default, install the config package
-    set(install_config_package ON)
-
-    # Turn OFF installation of config package by default if,
-    # in order of precedence:
-    # 1. The specific package variable is set to OFF
-    # 2. The package name is not in the list of packages to install config files
-    if(DEFINED BEMAN_INSTALL_CONFIG_FILE_PACKAGES)
-        if(
-            NOT "${install_component_name}"
-                IN_LIST
-                BEMAN_INSTALL_CONFIG_FILE_PACKAGES
-        )
-            set(install_config_package OFF)
-        endif()
-    endif()
-    if(DEFINED ${project_prefix}_INSTALL_CONFIG_FILE_PACKAGE)
-        set(install_config_package
-            ${${project_prefix}_INSTALL_CONFIG_FILE_PACKAGE}
-        )
-    endif()
-
-    if(install_config_package)
-        message(
-            VERBOSE
-            "beman-install-library: Export cmake config to ${package_install_dir} for '${name}'"
-        )
-
-        include(CMakePackageConfigHelpers)
-
-        find_file(
-            config_file_template
-            NAMES "${package_name}-config.cmake.in"
-            PATHS "${PROJECT_SOURCE_DIR}/cmake"
-            NO_DEFAULT_PATH
-            NO_CACHE
-            REQUIRED
-        )
-        set(config_package_file
-            "${CMAKE_CURRENT_BINARY_DIR}/${package_name}-config.cmake"
-        )
-        configure_package_config_file(
-            "${config_file_template}"
-            "${config_package_file}"
-            INSTALL_DESTINATION "${package_install_dir}"
-            PATH_VARS PROJECT_NAME PROJECT_VERSION
-        )
-
-        set(config_version_file
-            "${CMAKE_CURRENT_BINARY_DIR}/${package_name}-config-version.cmake"
-        )
-        write_basic_package_version_file(
-            "${config_version_file}"
-            VERSION "${PROJECT_VERSION}"
-            COMPATIBILITY ExactVersion
-        )
-
-        install(
-            FILES "${config_package_file}" "${config_version_file}"
-            DESTINATION "${package_install_dir}"
-            COMPONENT "${install_component_name}"
-        )
-
-        # NOTE: must be same value as ${TARGETS_EXPORT_NAME}.cmake! CK
-        set(config_targets_file "${package_name}-targets.cmake")
-        install(
-            EXPORT "${export_name}"
-            DESTINATION "${package_install_dir}"
-            NAMESPACE beman::
-            FILE "${config_targets_file}"
-            CXX_MODULES_DIRECTORY
-            cxx-modules
-            COMPONENT "${install_component_name}"
-        )
-    else()
-        message(
-            WARNING
-            "beman-install-library: Not installing a config package for '${name}'"
-        )
-    endif()
-endfunction()
-
-set(CPACK_GENERATOR TGZ)
-include(CPack)
diff --git a/cmake/beman-install-library.cmake b/cmake/beman-install-library.cmake
new file mode 100644
index 00000000..5b90d9d3
--- /dev/null
+++ b/cmake/beman-install-library.cmake
@@ -0,0 +1,290 @@
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+cmake_minimum_required(VERSION 3.30)
+
+include_guard(GLOBAL)
+
+include(CMakePackageConfigHelpers)
+include(GNUInstallDirs)
+
+# beman_install_library
+# =====================
+#
+# Installs a library (or set of targets) along with headers, C++ modules,
+# and optional CMake package configuration files.
+#
+# Usage:
+# ------
+#   beman_install_library(<name>
+#     TARGETS <target1> [<target2> ...]
+#     [DEPENDENCIES <dependency1> [<dependency2> ...]]
+#     [NAMESPACE <namespace>]
+#     [EXPORT_NAME <export-name>]
+#     [DESTINATION <install-prefix>]
+#   )
+#
+# Arguments:
+# ----------
+# name
+#   Logical package name (e.g. "beman.utility").
+#   Used to derive config file names and cache variable prefixes.
+#
+# TARGETS (required)
+#   List of CMake targets to install.
+#
+# DEPENDENCIES (optional)
+#   Semicolon-separated list, one dependency per entry.
+#   Each entry is a valid find_dependency() argument list.
+#   Note: you must use the bracket form for quoting if not only a package name is used!
+#   "[===[beman.inplace_vector 1.0.0]===] [===[beman.scope 0.0.1 EXACT]===] fmt"
+#
+# NAMESPACE (optional)
+#   Namespace for exported targets.
+#   Defaults to "beman::".
+#
+# EXPORT_NAME (optional)
+#   Name of the CMake export set.
+#   Defaults to "<name>-targets".
+#
+# DESTINATION (optional)
+#   The install destination for CXX_MODULES.
+#   Defaults to ${CMAKE_INSTALL_LIBDIR}/cmake/${name}/modules.
+#
+# Brief
+# -----
+#
+# This function installs the specified project TARGETS and its FILE_SET
+# HEADERS to the default CMAKE install destination.
+#
+# It also handles the installation of the CMake config package files if
+# needed.  If the given targets has FILE_SET CXX_MODULE, it will also
+# installed to the given DESTINATION
+#
+# Cache variables:
+# ----------------
+# BEMAN_INSTALL_CONFIG_FILE_PACKAGES
+#   List of package names for which config files should be installed.
+#
+# <PREFIX>_INSTALL_CONFIG_FILE_PACKAGE
+#   Per-package override to enable/disable config file installation.
+#   <PREFIX> is the uppercased package name with dots replaced by underscores.
+#
+function(beman_install_library name)
+    # ----------------------------
+    # Argument parsing
+    # ----------------------------
+    set(options)
+    set(oneValueArgs NAMESPACE EXPORT_NAME DESTINATION)
+    set(multiValueArgs TARGETS DEPENDENCIES)
+
+    cmake_parse_arguments(
+        BEMAN
+        "${options}"
+        "${oneValueArgs}"
+        "${multiValueArgs}"
+        ${ARGN}
+    )
+
+    if(NOT BEMAN_TARGETS)
+        message(
+            FATAL_ERROR
+            "beman_install_library(${name}): TARGETS must be specified"
+        )
+    endif()
+
+    if(CMAKE_SKIP_INSTALL_RULES)
+        message(
+            WARNING
+            "beman_install_library(${name}): not installing targets '${BEMAN_TARGETS}' due to CMAKE_SKIP_INSTALL_RULES"
+        )
+        return()
+    endif()
+
+    set(_config_install_dir "${CMAKE_INSTALL_LIBDIR}/cmake/${name}")
+
+    # ----------------------------
+    # Defaults
+    # ----------------------------
+    if(NOT BEMAN_NAMESPACE)
+        set(BEMAN_NAMESPACE "beman::")
+    endif()
+
+    if(NOT BEMAN_EXPORT_NAME)
+        set(BEMAN_EXPORT_NAME "${name}-targets")
+    endif()
+
+    if(NOT BEMAN_DESTINATION)
+        set(BEMAN_DESTINATION "${_config_install_dir}/modules")
+    endif()
+
+    string(REPLACE "beman." "" install_component_name "${name}")
+
+    # --------------------------------------------------
+    # Install each target with all of its file sets
+    # --------------------------------------------------
+    foreach(_tgt IN LISTS BEMAN_TARGETS)
+        if(NOT TARGET "${_tgt}")
+            message(
+                WARNING
+                "beman_install_library(${name}): '${_tgt}' is not a target"
+            )
+            continue()
+        endif()
+
+        # Given foo.bar, the component name is bar
+        string(REPLACE "." ";" name_parts "${_tgt}")
+        # fail if the name doesn't look like foo.bar
+        list(LENGTH name_parts name_parts_length)
+        if(NOT name_parts_length EQUAL 2)
+            message(
+                FATAL_ERROR
+                "beman_install_library(${name}): expects a name of the form 'beman.<name>', got '${_tgt}'"
+            )
+        endif()
+        list(GET name_parts -1 component_name)
+        set_target_properties(
+            "${_tgt}"
+            PROPERTIES EXPORT_NAME "${component_name}"
+        )
+        message(
+            VERBOSE
+            "beman_install_library(${name}): COMPONENT ${component_name} for TARGET '${_tgt}'"
+        )
+
+        # Get the list of interface header sets, exact one expected!
+        get_target_property(_header_sets ${_tgt} INTERFACE_HEADER_SETS)
+        if(_header_sets)
+            message(
+                VERBOSE
+                "beman-install-library(${name}): '${_tgt}' has INTERFACE_HEADER_SETS=${_header_sets}"
+            )
+        else()
+            set(_header_sets HEADERS) # Note: empty FILE_SET in this case! CK
+        endif()
+
+        # Detect presence of C++ module file sets, exact one expected!
+        get_target_property(_module_sets "${_tgt}" CXX_MODULE_SETS)
+        if(_module_sets)
+            message(
+                VERBOSE
+                "beman-install-library(${name}): '${_tgt}' has CXX_MODULE_SETS=${_module_sets}"
+            )
+            install(
+                TARGETS "${_tgt}"
+                COMPONENT "${install_component_name}"
+                EXPORT ${BEMAN_EXPORT_NAME}
+                ARCHIVE # DESTINATION ${CMAKE_INSTALL_LIBDIR}
+                LIBRARY # DESTINATION ${CMAKE_INSTALL_LIBDIR}
+                RUNTIME # DESTINATION ${CMAKE_INSTALL_BINDIR}
+                FILE_SET
+                    ${_header_sets} # DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
+                FILE_SET ${_module_sets} DESTINATION "${BEMAN_DESTINATION}"
+                # NOTE: There's currently no convention for this location! CK
+                CXX_MODULES_BMI
+                # TODO(CK): DESTINATION ${_config_install_dir}/bmi-${CMAKE_CXX_COMPILER_ID}_$<CONFIG>
+            )
+        else()
+            install(
+                TARGETS "${_tgt}"
+                COMPONENT "${install_component_name}"
+                EXPORT ${BEMAN_EXPORT_NAME}
+                ARCHIVE # DESTINATION ${CMAKE_INSTALL_LIBDIR}
+                LIBRARY # DESTINATION ${CMAKE_INSTALL_LIBDIR}
+                RUNTIME # DESTINATION ${CMAKE_INSTALL_BINDIR}
+                FILE_SET
+                    ${_header_sets} # DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
+            )
+        endif()
+    endforeach()
+
+    # --------------------------------------------------
+    # Export targets
+    # --------------------------------------------------
+    install(
+        EXPORT ${BEMAN_EXPORT_NAME}
+        NAMESPACE ${BEMAN_NAMESPACE}
+        CXX_MODULES_DIRECTORY
+        cxx-modules
+        DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/${name}
+        COMPONENT "${install_component_name}"
+    )
+
+    # ----------------------------------------
+    # Config file installation logic
+    # ----------------------------------------
+    string(TOUPPER "${name}" _pkg_upper)
+    string(REPLACE "." "_" _pkg_prefix "${_pkg_upper}")
+
+    option(
+        ${_pkg_prefix}_INSTALL_CONFIG_FILE_PACKAGE
+        "Enable creating and installing a CMake config-file package. Default: ON. Values: { ON, OFF }."
+        ON
+    )
+
+    set(_pkg_var "${_pkg_prefix}_INSTALL_CONFIG_FILE_PACKAGE")
+
+    if(NOT DEFINED ${_pkg_var})
+        set(${_pkg_var}
+            OFF
+            CACHE BOOL
+            "Install CMake package config files for ${name}"
+        )
+    endif()
+
+    set(_install_config OFF)
+
+    if(${_pkg_var})
+        set(_install_config ON)
+    elseif(BEMAN_INSTALL_CONFIG_FILE_PACKAGES)
+        list(FIND BEMAN_INSTALL_CONFIG_FILE_PACKAGES "${name}" _idx)
+        if(NOT _idx EQUAL -1)
+            set(_install_config ON)
+        endif()
+    endif()
+
+    # ----------------------------------------
+    # expand dependencies
+    # ----------------------------------------
+    set(_beman_find_deps "")
+    foreach(dep IN ITEMS ${BEMAN_DEPENDENCIES})
+        message(
+            VERBOSE
+            "beman-install-library(${name}): Add find_dependency(${dep})"
+        )
+        string(APPEND _beman_find_deps "find_dependency(${dep})\n")
+    endforeach()
+    set(BEMAN_FIND_DEPENDENCIES "${_beman_find_deps}")
+
+    # ----------------------------------------
+    # Generate + install config files
+    # ----------------------------------------
+    if(_install_config)
+        configure_package_config_file(
+            "${CMAKE_CURRENT_FUNCTION_LIST_DIR}/Config.cmake.in"
+            "${CMAKE_CURRENT_BINARY_DIR}/${name}-config.cmake"
+            INSTALL_DESTINATION ${_config_install_dir}
+        )
+
+        write_basic_package_version_file(
+            "${CMAKE_CURRENT_BINARY_DIR}/${name}-config-version.cmake"
+            VERSION ${PROJECT_VERSION}
+            COMPATIBILITY SameMajorVersion
+        )
+
+        install(
+            FILES
+                "${CMAKE_CURRENT_BINARY_DIR}/${name}-config.cmake"
+                "${CMAKE_CURRENT_BINARY_DIR}/${name}-config-version.cmake"
+            DESTINATION ${_config_install_dir}
+            COMPONENT "${install_component_name}"
+        )
+    else()
+        message(
+            WARNING
+            "beman-install-library(${name}): Not installing a config package for '${name}'"
+        )
+    endif()
+endfunction()
+
+set(CPACK_GENERATOR TGZ)
+include(CPack)
diff --git a/cmake/beman.execution-config.cmake.in b/cmake/beman.execution-config.cmake.in
deleted file mode 100644
index 40463a38..00000000
--- a/cmake/beman.execution-config.cmake.in
+++ /dev/null
@@ -1,7 +0,0 @@
-# cmake/Config.cmake.in -*-makefile-*-
-# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-
-@PACKAGE_INIT@
-
-include("${CMAKE_CURRENT_LIST_DIR}/@TARGETS_EXPORT_NAME@.cmake")
-check_required_components("@TARGET_LIBRARY@")
diff --git a/cmake/cxx-modules-rules.cmake b/cmake/cxx-modules-rules.cmake
index 498131d1..91939b36 100644
--- a/cmake/cxx-modules-rules.cmake
+++ b/cmake/cxx-modules-rules.cmake
@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
 # A CMake language file to be included as the last step of all project() command calls.
 # This file must be included/used as CMAKE_PROJECT_INCLUDE -> after project()
@@ -89,6 +90,11 @@ if(NOT DEFINED CMAKE_CXX_MODULE_STD)
     set(CMAKE_CXX_MODULE_STD OFF)
 endif()
 
+if(CMAKE_CXX_STANDARD GREATER_EQUAL 20)
+    option(BEMAN_USE_MODULES "Build CXX_MODULES" ${CMAKE_CXX_SCAN_FOR_MODULES})
+endif()
+message(STATUS "BEMAN_USE_MODULES=${BEMAN_USE_MODULES}")
+
 option(
     BEMAN_USE_STD_MODULE
     "Check if 'import std;' is possible with the toolchain?"
@@ -96,7 +102,7 @@ option(
 )
 message(STATUS "BEMAN_USE_STD_MODULE=${BEMAN_USE_STD_MODULE}")
 
-if(BEMAN_USE_STD_MODULE)
+if(BEMAN_USE_MODULES AND BEMAN_USE_STD_MODULE)
     # -------------------------------------------------------------------------
     # Tell CMake that we explicitly want `import std`.
     # This will initialize the property on all targets declared after this to 1
@@ -121,11 +127,6 @@ if(BEMAN_USE_STD_MODULE)
     message(STATUS "BEMAN_HAS_IMPORT_STD=${BEMAN_HAS_IMPORT_STD}")
 endif()
 
-if(CMAKE_CXX_STANDARD GREATER_EQUAL 20)
-    option(BEMAN_USE_MODULES "Build CXX_MODULES" ${CMAKE_CXX_SCAN_FOR_MODULES})
-endif()
-message(STATUS "BEMAN_USE_MODULES=${BEMAN_USE_MODULES}")
-
 if(NOT BEMAN_USE_MODULES)
     set(CMAKE_CXX_SCAN_FOR_MODULES OFF)
 endif()
diff --git a/cmake/prelude.cmake b/cmake/prelude.cmake
index c7b86338..588e608c 100644
--- a/cmake/prelude.cmake
+++ b/cmake/prelude.cmake
@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
 # This file must be included/used as CMAKE_PROJECT_TOP_LEVEL_INCLUDES -> before project() is called!
 #
@@ -14,35 +15,36 @@ if(CMAKE_SOURCE_DIR STREQUAL CMAKE_BINARY_DIR)
     )
 endif()
 
-if(PROJECT_NAME)
-    message(
-        FATAL_ERROR
-        "This CMake file has to be included before first project() command call!"
-    )
-endif()
+list(APPEND CMAKE_MODULE_PATH ${CMAKE_CURRENT_LIST_DIR})
 
-# gersemi: off
-# ---------------------------------------------------------------------------
-# use ccache if found
 # ---------------------------------------------------------------------------
-find_program(CCACHE_EXECUTABLE "ccache" HINTS /usr/local/bin /opt/local/bin)
-if(CCACHE_EXECUTABLE)
-    message(STATUS "use ccache")
-    set(CMAKE_CXX_COMPILER_LAUNCHER "${CCACHE_EXECUTABLE}" CACHE PATH "ccache")
-    set(CMAKE_C_COMPILER_LAUNCHER "${CCACHE_EXECUTABLE}" CACHE PATH "ccache")
+if(NOT BEMAN_USE_STD_MODULE OR CMAKE_VERSION VERSION_GREATER_EQUAL 4.3)
+    return()
 endif()
+# ---------------------------------------------------------------------------
 
-list(APPEND CMAKE_MODULE_PATH ${CMAKE_CURRENT_LIST_DIR})
-
+# gersemi: off
 # ---------------------------------------------------------------------------
 # check if import std; is supported by CMAKE_CXX_COMPILER
 # ---------------------------------------------------------------------------
 if(CMAKE_VERSION VERSION_GREATER_EQUAL 4.2)
+    if(PROJECT_NAME)
+        message(
+            WARNING
+            "This CMake file has to be included before first project() command call!"
+        )
+    endif()
+
     set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD "d0edc3af-4c50-42ea-a356-e2862fe7a444")
 endif()
 # gersemi: on
 
-# FIXME: on APPLE with clang++ still needs to export CXX=clang++
+# TODO(CK): Do we need this HACK for linux too?
+# if(NOT APPLE)
+#     return()
+# endif()
+
+# FIXME: clang++ we still needs to export CXX=clang++
 if("$ENV{CXX}" STREQUAL "" AND CMAKE_CXX_COMPILER)
     message(WARNING "\$CXX is not set")
     set(ENV{CXX} ${CMAKE_CXX_COMPILER})
@@ -80,7 +82,7 @@ if(
     elseif(LINUX)
         execute_process(
             OUTPUT_VARIABLE LLVM_MODULES
-            COMMAND clang++ -print-file-name=c++/libc++.modules.json
+            COMMAND clang++ -print-file-name=libc++.modules.json
             COMMAND_ECHO STDOUT
             OUTPUT_STRIP_TRAILING_WHITESPACE
         )
@@ -107,7 +109,7 @@ if(
         # gersemi: on
     else()
         message(
-            WARNING
+            FATAL_ERROR
             "File does NOT EXISTS! ${CMAKE_CXX_STDLIB_MODULES_JSON}"
         )
     endif()
diff --git a/cmake/presets/CMakeGenericPresets.json b/cmake/presets/CMakeGenericPresets.json
index df2d2045..e86aea1e 100644
--- a/cmake/presets/CMakeGenericPresets.json
+++ b/cmake/presets/CMakeGenericPresets.json
@@ -12,9 +12,9 @@
           "type": "path",
           "value": "${sourceDir}/stagedir"
         },
+        "BEMAN_USE_MODULES": true,
         "CMAKE_CXX_STANDARD": "23",
         "CMAKE_CXX_EXTENSIONS": true,
-        "CMAKE_CXX_SCAN_FOR_MODULES": true,
         "CMAKE_CXX_STANDARD_REQUIRED": true,
         "CMAKE_EXPORT_COMPILE_COMMANDS": true,
         "CMAKE_INSTALL_MESSAGE": "LAZY",
diff --git a/examples/CMakeLists.txt b/examples/CMakeLists.txt
index c68e6e17..958b6df0 100644
--- a/examples/CMakeLists.txt
+++ b/examples/CMakeLists.txt
@@ -43,7 +43,6 @@ foreach(EXAMPLE ${EXAMPLES})
     add_executable(${EXAMPLE_TARGET})
     target_sources(${EXAMPLE_TARGET} PRIVATE ${EXAMPLE}.cpp)
     if(BEMAN_USE_MODULES)
-        # target_compile_definitions(${EXAMPLE_TARGET} PUBLIC BEMAN_HAS_MODULES)
         target_link_libraries(${EXAMPLE_TARGET} PRIVATE beman::execution)
     else()
         target_link_libraries(
diff --git a/infra/cmake/appleclang-toolchain.cmake b/infra/cmake/appleclang-toolchain.cmake
index 70ef548e..451c86b6 100644
--- a/infra/cmake/appleclang-toolchain.cmake
+++ b/infra/cmake/appleclang-toolchain.cmake
@@ -32,7 +32,7 @@ endif()
 set(CMAKE_C_FLAGS_DEBUG_INIT "${SANITIZER_FLAGS}")
 set(CMAKE_CXX_FLAGS_DEBUG_INIT "${SANITIZER_FLAGS}")
 
-set(RELEASE_FLAGS "-O3 ${SANITIZER_FLAGS}")
+set(RELEASE_FLAGS "-O3")
 
 set(CMAKE_C_FLAGS_RELWITHDEBINFO_INIT "${RELEASE_FLAGS}")
 set(CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT "${RELEASE_FLAGS}")
@@ -41,4 +41,4 @@ set(CMAKE_C_FLAGS_RELEASE_INIT "${RELEASE_FLAGS}")
 set(CMAKE_CXX_FLAGS_RELEASE_INIT "${RELEASE_FLAGS}")
 
 # Add this dir to the module path so that `find_package(beman-install-library)` works
-list(APPEND CMAKE_PREFIX_PATH "${CMAKE_CURRENT_LIST_DIR}")
+# NO! list(APPEND CMAKE_PREFIX_PATH "${CMAKE_CURRENT_LIST_DIR}")
diff --git a/infra/cmake/gnu-toolchain.cmake b/infra/cmake/gnu-toolchain.cmake
index d3b9f92d..a946349d 100644
--- a/infra/cmake/gnu-toolchain.cmake
+++ b/infra/cmake/gnu-toolchain.cmake
@@ -29,7 +29,7 @@ endif()
 set(CMAKE_C_FLAGS_DEBUG_INIT "${SANITIZER_FLAGS}")
 set(CMAKE_CXX_FLAGS_DEBUG_INIT "${SANITIZER_FLAGS}")
 
-set(RELEASE_FLAGS "-O3 ${SANITIZER_FLAGS}")
+set(RELEASE_FLAGS "-O3")
 
 set(CMAKE_C_FLAGS_RELWITHDEBINFO_INIT "${RELEASE_FLAGS}")
 set(CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT "${RELEASE_FLAGS}")
@@ -38,4 +38,4 @@ set(CMAKE_C_FLAGS_RELEASE_INIT "${RELEASE_FLAGS}")
 set(CMAKE_CXX_FLAGS_RELEASE_INIT "${RELEASE_FLAGS}")
 
 # Add this dir to the module path so that `find_package(beman-install-library)` works
-list(APPEND CMAKE_PREFIX_PATH "${CMAKE_CURRENT_LIST_DIR}")
+# NO! list(APPEND CMAKE_PREFIX_PATH "${CMAKE_CURRENT_LIST_DIR}")
diff --git a/infra/cmake/llvm-toolchain.cmake b/infra/cmake/llvm-toolchain.cmake
index f1623b7e..b0ca3bdb 100644
--- a/infra/cmake/llvm-toolchain.cmake
+++ b/infra/cmake/llvm-toolchain.cmake
@@ -29,7 +29,7 @@ endif()
 set(CMAKE_C_FLAGS_DEBUG_INIT "${SANITIZER_FLAGS}")
 set(CMAKE_CXX_FLAGS_DEBUG_INIT "${SANITIZER_FLAGS}")
 
-set(RELEASE_FLAGS "-O3 ${SANITIZER_FLAGS}")
+set(RELEASE_FLAGS "-O3")
 
 set(CMAKE_C_FLAGS_RELWITHDEBINFO_INIT "${RELEASE_FLAGS}")
 set(CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT "${RELEASE_FLAGS}")
@@ -38,4 +38,4 @@ set(CMAKE_C_FLAGS_RELEASE_INIT "${RELEASE_FLAGS}")
 set(CMAKE_CXX_FLAGS_RELEASE_INIT "${RELEASE_FLAGS}")
 
 # Add this dir to the module path so that `find_package(beman-install-library)` works
-list(APPEND CMAKE_PREFIX_PATH "${CMAKE_CURRENT_LIST_DIR}")
+# NO! list(APPEND CMAKE_PREFIX_PATH "${CMAKE_CURRENT_LIST_DIR}")
diff --git a/infra/cmake/msvc-toolchain.cmake b/infra/cmake/msvc-toolchain.cmake
index bdc24de9..7bd82279 100644
--- a/infra/cmake/msvc-toolchain.cmake
+++ b/infra/cmake/msvc-toolchain.cmake
@@ -29,7 +29,7 @@ endif()
 set(CMAKE_CXX_FLAGS_DEBUG_INIT "/EHsc /permissive- ${SANITIZER_FLAGS}")
 set(CMAKE_C_FLAGS_DEBUG_INIT "/EHsc /permissive- ${SANITIZER_FLAGS}")
 
-set(RELEASE_FLAGS "/EHsc /permissive- /O2 ${SANITIZER_FLAGS}")
+set(RELEASE_FLAGS "/EHsc /permissive- /O2")
 
 set(CMAKE_C_FLAGS_RELWITHDEBINFO_INIT "${RELEASE_FLAGS}")
 set(CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT "${RELEASE_FLAGS}")
@@ -38,4 +38,4 @@ set(CMAKE_C_FLAGS_RELEASE_INIT "${RELEASE_FLAGS}")
 set(CMAKE_CXX_FLAGS_RELEASE_INIT "${RELEASE_FLAGS}")
 
 # Add this dir to the module path so that `find_package(beman-install-library)` works
-list(APPEND CMAKE_PREFIX_PATH "${CMAKE_CURRENT_LIST_DIR}")
+# NO! list(APPEND CMAKE_PREFIX_PATH "${CMAKE_CURRENT_LIST_DIR}")
diff --git a/src/beman/execution/CMakeLists.txt b/src/beman/execution/CMakeLists.txt
index 10774bac..1558ca95 100644
--- a/src/beman/execution/CMakeLists.txt
+++ b/src/beman/execution/CMakeLists.txt
@@ -200,8 +200,8 @@ if(BEMAN_USE_MODULES)
             execution.cpp # TODO(CK): check if really needed!
         PUBLIC
             FILE_SET CXX_MODULES
-                BASE_DIRS ${PROJECT_SOURCE_DIR}/src/beman/execution
-                FILES ${PROJECT_SOURCE_DIR}/src/beman/execution/execution.cppm
+                BASE_DIRS ${CMAKE_CURRENT_SOURCE_DIR}
+                FILES execution.cppm
     )
     target_link_libraries(${TARGET_PREFIX} PUBLIC ${TARGET_NAME})
 endif()
diff --git a/tests/beman/execution/CMakeLists.txt b/tests/beman/execution/CMakeLists.txt
index 65238e5c..0bbfea16 100644
--- a/tests/beman/execution/CMakeLists.txt
+++ b/tests/beman/execution/CMakeLists.txt
@@ -122,6 +122,13 @@ foreach(test ${execution_tests})
     add_test(NAME ${TEST_EXE} COMMAND $<TARGET_FILE:${TEST_EXE}>)
 endforeach()
 
+if(CMAKE_BUILD_TYPE STREQUAL "Debug")
+    return()
+endif()
+
+#======================================================================
+# NOTE: Only for Release build with enabled install rules useful! CK
+#======================================================================
 if(BEMAN_EXECUTION_INSTALL_CONFIG_FILE_PACKAGE AND NOT CMAKE_SKIP_INSTALL_RULES)
     # test if the targets are usable from the install directory
     add_test(
@@ -141,11 +148,11 @@ if(BEMAN_EXECUTION_INSTALL_CONFIG_FILE_PACKAGE AND NOT CMAKE_SKIP_INSTALL_RULES)
             --build-makeprogram ${CMAKE_MAKE_PROGRAM} #
             --build-options #
             "-D BEMAN_USE_MODULES=${BEMAN_USE_MODULES}"
+            "-D BEMAN_USE_STD_MODULE=${BEMAN_USE_STD_MODULE}"
             "-D CMAKE_BUILD_TYPE=$<CONFIG>"
             "-D CMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}"
             "-D CMAKE_CXX_EXTENSIONS=${CMAKE_CXX_EXTENSIONS}"
             "-D CMAKE_CXX_MODULE_STD=${CMAKE_CXX_MODULE_STD}"
-            "-D CMAKE_CXX_SCAN_FOR_MODULES=${CMAKE_CXX_SCAN_FOR_MODULES}"
             "-D CMAKE_CXX_STANDARD=${CMAKE_CXX_STANDARD}"
             "-D CMAKE_CXX_STANDARD_REQUIRED=${CMAKE_CXX_STANDARD_REQUIRED}"
             "-D CMAKE_PREFIX_PATH=${CMAKE_BINARY_DIR}/stagedir"