diff --git a/CMakeLists.txt b/CMakeLists.txt
index a383d22..26c7a78 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -17,14 +17,12 @@ if(CTH_ENABLE_TESTS)
 	enable_testing()
 endif()
 
-# exported
+# exported, a parent project turns components off with set(CTH_BUILD_<COMPONENT> OFF)
 add_subdirectory(cth)
-add_subdirectory(cth_os)
-add_subdirectory(cth_coro)
-add_subdirectory(cth_net)
-if(WIN32)
-	add_subdirectory(cth_win)
-endif()
+cth_add_subdirectory(cth_os CTH_BUILD_OS)
+cth_add_subdirectory(cth_coro CTH_BUILD_CORO)
+cth_add_subdirectory(cth_net CTH_BUILD_NET)
+cth_add_subdirectory(cth_win CTH_BUILD_WIN WIN32)
 
 cth_create_package()
 
diff --git a/README.md b/README.md
index e2cca89..48510ac 100644
--- a/README.md
+++ b/README.md
@@ -139,11 +139,23 @@ find_package(cth CONFIG REQUIRED COMPONENTS coro)
 target_link_libraries(app PRIVATE cth::coro)
 ```
 
+or add the source as a subdirectory, options turn components off:
+
+```cmake
+set(CTH_BUILD_NET OFF)
+add_subdirectory(lib/cth)
+target_link_libraries(app PRIVATE cth::os)
+```
+
 api not stable yet, no versioned releases
 
 ## components
-- `cth`, `os`, `coro`
+- `cth`, `os`, `coro`, `net`
 - windows only: `win`, `win_capture`
 
+## options
+- `CTH_BUILD_OS`, `CTH_BUILD_CORO`, `CTH_BUILD_NET`: default ON
+- `CTH_BUILD_WIN`: default ON on windows
+
 # license
 [MIT](LICENSE)
diff --git a/cth/CMakeLists.txt b/cth/CMakeLists.txt
index cfa0e43..adb41cc 100644
--- a/cth/CMakeLists.txt
+++ b/cth/CMakeLists.txt
@@ -11,6 +11,10 @@ cth_pkg_target_include_directories(
 
 target_compile_options(cth INTERFACE $<$<CXX_COMPILER_ID:MSVC>:/Zc:preprocessor>)
 
+# cth/hash/hash_aggregates.hpp includes boost/pfr.hpp
+cth_pkg_target_find_package(cth boost_pfr CONFIG REQUIRED)
+target_link_libraries(cth INTERFACE Boost::pfr)
+
 target_link_libraries(cth INTERFACE $<$<AND:$<CXX_COMPILER_ID:GNU,Clang>,$<NOT:$<PLATFORM_ID:Windows>>>:stdc++exp>)
 
 # tests
diff --git a/cth_coro/CMakeLists.txt b/cth_coro/CMakeLists.txt
index f001617..df04af0 100644
--- a/cth_coro/CMakeLists.txt
+++ b/cth_coro/CMakeLists.txt
@@ -1,3 +1,5 @@
+cth_assert_target(cth::os REASON "cth_coro requires cth_os (CTH_BUILD_OS)")
+
 cth_glob_cpp(CTH_CORO_SRC "src")
 cth_glob_cpp(CTH_CORO_INCL "incl")
 
diff --git a/cth_net/CMakeLists.txt b/cth_net/CMakeLists.txt
index e94daa8..b8f4bc3 100644
--- a/cth_net/CMakeLists.txt
+++ b/cth_net/CMakeLists.txt
@@ -1,3 +1,5 @@
+cth_assert_target(cth::os REASON "cth_net requires cth_os (CTH_BUILD_OS)")
+
 cth_glob_cpp(CTH_NET_SRC "src")
 cth_glob_cpp(CTH_NET_INCL "incl")
 
diff --git a/cth_win/CMakeLists.txt b/cth_win/CMakeLists.txt
index b5692d0..28f14d5 100644
--- a/cth_win/CMakeLists.txt
+++ b/cth_win/CMakeLists.txt
@@ -1,3 +1,7 @@
+cth_assert_true(WIN32 REASON "cth_win targets windows")
+cth_assert_target(cth::os REASON "cth_win requires cth_os (CTH_BUILD_OS)")
+cth_assert_target(cth::coro REASON "cth_win requires cth_coro (CTH_BUILD_CORO)")
+
 cth_glob_cpp(CTH_WIN_SRC "src")
 cth_glob_cpp(CTH_WIN_INCL "incl")
 
diff --git a/lib/cth_cmake b/lib/cth_cmake
index 12f2a5c..09a6c5d 160000
--- a/lib/cth_cmake
+++ b/lib/cth_cmake
@@ -1 +1 @@
-Subproject commit 12f2a5c6d1a7c999ff3f71c7035c8fe104b93e30
+Subproject commit 09a6c5d02421cba58fcf33bc3e4fd3d4fb646002