diff --git a/libcxx/cmake/caches/Generic-no-threads.cmake b/libcxx/cmake/caches/Generic-no-threads.cmake
--- a/libcxx/cmake/caches/Generic-no-threads.cmake
+++ b/libcxx/cmake/caches/Generic-no-threads.cmake
@@ -1,3 +1,4 @@
+set(LIBCXX_ENABLE_STD_MODULES ON CACHE BOOL "") # TODO MODULES Remove when enabled automatically.
 set(LIBCXX_ENABLE_THREADS OFF CACHE BOOL "")
 set(LIBCXXABI_ENABLE_THREADS OFF CACHE BOOL "")
 set(LIBCXX_ENABLE_MONOTONIC_CLOCK OFF CACHE BOOL "")
diff --git a/libcxx/docs/Modules.rst b/libcxx/docs/Modules.rst
--- a/libcxx/docs/Modules.rst
+++ b/libcxx/docs/Modules.rst
@@ -44,6 +44,7 @@
 
    * ``LIBCXX_ENABLE_LOCALIZATION``
    * ``LIBCXX_ENABLE_WIDE_CHARACTERS``
+   * ``LIBCXX_ENABLE_THREADS``
 
 Some of the current limitations
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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
@@ -29,9 +29,6 @@
   endif()
 endmacro()
 
-if(NOT @LIBCXX_ENABLE_THREADS@ OR NOT @LIBCXXABI_ENABLE_THREADS@ OR NOT @LIBCXX_ENABLE_MONOTONIC_CLOCK@)
-  message(FATAL_ERROR "Modules without thread support is not yet implemented.")
-endif()
 if(NOT @LIBCXX_ENABLE_FILESYSTEM@)
   message(FATAL_ERROR "Modules without filesystem support is not yet implemented.")
 endif()
diff --git a/libcxx/modules/std/barrier.inc b/libcxx/modules/std/barrier.inc
--- a/libcxx/modules/std/barrier.inc
+++ b/libcxx/modules/std/barrier.inc
@@ -8,5 +8,7 @@
 //===----------------------------------------------------------------------===//
 
 export namespace std {
+#ifndef _LIBCPP_HAS_NO_THREADS
   using std::barrier;
+#endif // _LIBCPP_HAS_NO_THREADS
 } // namespace std
diff --git a/libcxx/modules/std/chrono.inc b/libcxx/modules/std/chrono.inc
--- a/libcxx/modules/std/chrono.inc
+++ b/libcxx/modules/std/chrono.inc
@@ -112,8 +112,10 @@
 
     using std::chrono::file_time;
 
+#ifndef _LIBCPP_HAS_NO_MONOTONIC_CLOCK
     // [time.clock.steady], class steady_clock
     using std::chrono::steady_clock;
+#endif
 
     // [time.clock.hires], class high_resolution_clock
     using std::chrono::high_resolution_clock;
diff --git a/libcxx/modules/std/condition_variable.inc b/libcxx/modules/std/condition_variable.inc
--- a/libcxx/modules/std/condition_variable.inc
+++ b/libcxx/modules/std/condition_variable.inc
@@ -8,7 +8,7 @@
 //===----------------------------------------------------------------------===//
 
 export namespace std {
-
+#ifndef _LIBCPP_HAS_NO_THREADS
   // [thread.condition.condvar], class condition_variable
   using std::condition_variable;
   // [thread.condition.condvarany], class condition_variable_any
@@ -18,5 +18,5 @@
   using std::notify_all_at_thread_exit;
 
   using std::cv_status;
-
+#endif // _LIBCPP_HAS_NO_THREADS
 } // namespace std
diff --git a/libcxx/modules/std/future.inc b/libcxx/modules/std/future.inc
--- a/libcxx/modules/std/future.inc
+++ b/libcxx/modules/std/future.inc
@@ -8,6 +8,7 @@
 //===----------------------------------------------------------------------===//
 
 export namespace std {
+#ifndef _LIBCPP_HAS_NO_THREADS
   using std::future_errc;
   using std::future_status;
   using std::launch;
@@ -50,4 +51,5 @@
 
   // [futures.async], function template async
   using std::async;
+#endif // _LIBCPP_HAS_NO_THREADS
 } // namespace std
diff --git a/libcxx/modules/std/latch.inc b/libcxx/modules/std/latch.inc
--- a/libcxx/modules/std/latch.inc
+++ b/libcxx/modules/std/latch.inc
@@ -8,5 +8,7 @@
 //===----------------------------------------------------------------------===//
 
 export namespace std {
+#ifndef _LIBCPP_HAS_NO_THREADS
   using std::latch;
+#endif // _LIBCPP_HAS_NO_THREADS
 } // namespace std
diff --git a/libcxx/modules/std/memory.inc b/libcxx/modules/std/memory.inc
--- a/libcxx/modules/std/memory.inc
+++ b/libcxx/modules/std/memory.inc
@@ -187,6 +187,7 @@
   // [inout.ptr], function template inout_ptr
   //  using std::inout_ptr;
 
+#ifndef _LIBCPP_HAS_NO_THREADS
   // [depr.util.smartptr.shared.atomic]
   using std::atomic_is_lock_free;
 
@@ -203,4 +204,5 @@
   using std::atomic_compare_exchange_strong_explicit;
   using std::atomic_compare_exchange_weak;
   using std::atomic_compare_exchange_weak_explicit;
+#endif // _LIBCPP_HAS_NO_THREADS
 } // namespace std
diff --git a/libcxx/modules/std/mutex.inc b/libcxx/modules/std/mutex.inc
--- a/libcxx/modules/std/mutex.inc
+++ b/libcxx/modules/std/mutex.inc
@@ -8,6 +8,7 @@
 //===----------------------------------------------------------------------===//
 
 export namespace std {
+#ifndef _LIBCPP_HAS_NO_THREADS
   // [thread.mutex.class], class mutex
   using std::mutex;
   // [thread.mutex.recursive], class recursive_mutex
@@ -35,6 +36,7 @@
   // [thread.lock.algorithm], generic locking algorithms
   using std::lock;
   using std::try_lock;
+#endif // _LIBCPP_HAS_NO_THREADS
 
   using std::once_flag;
 
diff --git a/libcxx/modules/std/semaphore.inc b/libcxx/modules/std/semaphore.inc
--- a/libcxx/modules/std/semaphore.inc
+++ b/libcxx/modules/std/semaphore.inc
@@ -8,8 +8,10 @@
 //===----------------------------------------------------------------------===//
 
 export namespace std {
+#ifndef _LIBCPP_HAS_NO_THREADS
   // [thread.sema.cnt], class template counting_semaphore
   using std::counting_semaphore;
 
   using std::binary_semaphore;
+#endif // _LIBCPP_HAS_NO_THREADS
 } // namespace std
diff --git a/libcxx/modules/std/shared_mutex.inc b/libcxx/modules/std/shared_mutex.inc
--- a/libcxx/modules/std/shared_mutex.inc
+++ b/libcxx/modules/std/shared_mutex.inc
@@ -8,6 +8,7 @@
 //===----------------------------------------------------------------------===//
 
 export namespace std {
+#ifndef _LIBCPP_HAS_NO_THREADS
   // [thread.sharedmutex.class], class shared_­mutex
   using std::shared_mutex;
   // [thread.sharedtimedmutex.class], class shared_­timed_­mutex
@@ -15,4 +16,5 @@
   // [thread.lock.shared], class template shared_­lock
   using std::shared_lock;
   using std::swap;
+#endif // _LIBCPP_HAS_NO_THREADS
 } // namespace std
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
@@ -8,6 +8,7 @@
 //===----------------------------------------------------------------------===//
 
 export namespace std {
+#ifndef _LIBCPP_HAS_NO_THREADS
   // [stoptoken], class stop_­token
   using std::stop_token;
 
@@ -20,4 +21,5 @@
 
   // [stopcallback], class template stop_­callback
   using std::stop_callback;
+#endif // _LIBCPP_HAS_NO_THREADS
 } // namespace std
diff --git a/libcxx/modules/std/thread.inc b/libcxx/modules/std/thread.inc
--- a/libcxx/modules/std/thread.inc
+++ b/libcxx/modules/std/thread.inc
@@ -8,6 +8,7 @@
 //===----------------------------------------------------------------------===//
 
 export namespace std {
+#ifndef _LIBCPP_HAS_NO_THREADS
   // [thread.thread.class], class thread
   using std::thread;
 
@@ -28,11 +29,12 @@
   // [thread.thread.id]
   using std::operator==;
   using std::operator<=>;
-#ifndef _LIBCPP_HAS_NO_LOCALIZATION
+#  ifndef _LIBCPP_HAS_NO_LOCALIZATION
   using std::operator<<;
-#endif // _LIBCPP_HAS_NO_LOCALIZATION
+#  endif // _LIBCPP_HAS_NO_LOCALIZATION
 
   using std::formatter;
 
   using std::hash;
+#endif // _LIBCPP_HAS_NO_THREADS
 } // namespace std
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
@@ -569,8 +569,11 @@
         - "**/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"