diff --git a/libcxx/cmake/caches/Generic-no-experimental.cmake b/libcxx/cmake/caches/Generic-no-experimental.cmake
--- a/libcxx/cmake/caches/Generic-no-experimental.cmake
+++ b/libcxx/cmake/caches/Generic-no-experimental.cmake
@@ -1,2 +1,3 @@
+set(LIBCXX_ENABLE_STD_MODULES ON CACHE BOOL "") # TODO MODULES Remove when enabled automatically.
 set(LIBCXX_TEST_PARAMS "enable_experimental=False" CACHE STRING "")
 set(LIBCXXABI_TEST_PARAMS "${LIBCXX_TEST_PARAMS}" CACHE STRING "")
diff --git a/libcxx/docs/Modules.rst b/libcxx/docs/Modules.rst
--- a/libcxx/docs/Modules.rst
+++ b/libcxx/docs/Modules.rst
@@ -71,7 +71,6 @@
  * Only C++23 and C++26 are tested
  * Libc++ is not tested with modules instead of headers
  * The module ``.cppm`` files are not installed
- * The experimental ``PSTL`` library is not supported
  * Clang supports modules using GNU extensions, but libc++ does not work using
    GNU extensions.
  * Clang:
diff --git a/libcxx/modules/CMakeLists.txt.in b/libcxx/modules/CMakeLists.txt.in
--- a/libcxx/modules/CMakeLists.txt.in
+++ b/libcxx/modules/CMakeLists.txt.in
@@ -35,7 +35,6 @@
     std.cppm
 )
 
-target_compile_definitions(std PRIVATE _LIBCPP_ENABLE_EXPERIMENTAL)
 target_include_directories(std SYSTEM PRIVATE @LIBCXX_CONFIGURED_INCLUDE_DIRS@)
 
 if (NOT @LIBCXX_ENABLE_EXCEPTIONS@)
diff --git a/libcxx/modules/std/execution.inc b/libcxx/modules/std/execution.inc
--- a/libcxx/modules/std/execution.inc
+++ b/libcxx/modules/std/execution.inc
@@ -7,6 +7,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#ifdef _LIBCPP_ENABLE_EXPERIMENTAL
 export namespace std {
   // [execpol.type], execution policy type trait
   using std::is_execution_policy;
@@ -32,3 +33,4 @@
   using std::execution::seq;
   using std::execution::unseq;
 } // namespace std::execution
+#endif // _LIBCPP_ENABLE_EXPERIMENTAL
diff --git a/libcxx/modules/std/ranges.inc b/libcxx/modules/std/ranges.inc
--- a/libcxx/modules/std/ranges.inc
+++ b/libcxx/modules/std/ranges.inc
@@ -204,11 +204,13 @@
       using std::ranges::views::drop_while;
     } // namespace views
 
+#ifdef _LIBCPP_ENABLE_EXPERIMENTAL
     using std::ranges::join_view;
 
     namespace views {
       using std::ranges::views::join;
     } // namespace views
+#endif // _LIBCPP_ENABLE_EXPERIMENTAL
 #if 0
     using std::ranges::join_with_view;
 
diff --git a/libcxx/modules/std/stop_token.inc b/libcxx/modules/std/stop_token.inc
--- a/libcxx/modules/std/stop_token.inc
+++ b/libcxx/modules/std/stop_token.inc
@@ -9,6 +9,7 @@
 
 export namespace std {
 #ifndef _LIBCPP_HAS_NO_THREADS
+#  ifdef _LIBCPP_ENABLE_EXPERIMENTAL
   // [stoptoken], class stop_­token
   using std::stop_token;
 
@@ -21,5 +22,6 @@
 
   // [stopcallback], class template stop_­callback
   using std::stop_callback;
-#endif // _LIBCPP_HAS_NO_THREADS
+#  endif // _LIBCPP_ENABLE_EXPERIMENTAL
+#endif   // _LIBCPP_HAS_NO_THREADS
 } // namespace std
diff --git a/libcxx/test/lit.local.cfg b/libcxx/test/lit.local.cfg
--- a/libcxx/test/lit.local.cfg
+++ b/libcxx/test/lit.local.cfg
@@ -52,8 +52,10 @@
         + os.path.join(config.test_exec_root, "__config_module__/CMakeFiles/std.dir"),
     )
 
-    flags = getSubstitution("%{flags}", config)
     cmake = getSubstitution("%{cmake}", config)
+    flags = getSubstitution("%{flags}", config)
+    if "c++experimental" in config.available_features:
+        flags = f"{flags} -D_LIBCPP_ENABLE_EXPERIMENTAL"
 
     subprocess.check_call(
         [cmake, f"-DCMAKE_CXX_STANDARD={std}", f"-DCMAKE_CXX_FLAGS={flags}", build],
diff --git a/libcxx/utils/ci/buildkite-pipeline.yml b/libcxx/utils/ci/buildkite-pipeline.yml
--- a/libcxx/utils/ci/buildkite-pipeline.yml
+++ b/libcxx/utils/ci/buildkite-pipeline.yml
@@ -687,8 +687,11 @@
         - "**/test-results.xml"
         - "**/*.abilist"
       env:
-          CC: "clang-${LLVM_HEAD_VERSION}"
-          CXX: "clang++-${LLVM_HEAD_VERSION}"
+          # Note: Modules require and absolute path for clang-scan-deps
+          # https://github.com/llvm/llvm-project/issues/61006
+          CC: "/usr/lib/llvm-${LLVM_HEAD_VERSION}/bin/clang"
+          CXX: "/usr/lib/llvm-${LLVM_HEAD_VERSION}/bin/clang++"
+          CMAKE: "/opt/bin/cmake"
           ENABLE_CLANG_TIDY: "On"
       agents:
         queue: "libcxx-builders"