diff --git a/libcxx/docs/ReleaseNotes.rst b/libcxx/docs/ReleaseNotes.rst
--- a/libcxx/docs/ReleaseNotes.rst
+++ b/libcxx/docs/ReleaseNotes.rst
@@ -100,6 +100,9 @@
 - ``<string>``, ``<string_view>``, and ``<mutex>`` no longer include ``<functional>``
   in any C++ version (it was previously included in C++20 and earlier).
 
+- ``<atomic>``, ``<barrier>``, ``<latch>``, ``<numeric>``, ``<semaphore>`` and ``<shared_mutex>`` no longer include ``<iosfwd>``
+  (it was previously included in all Standard versions).
+
 - The headers ``<experimental/algorithm>`` and ``<experimental/functional>`` have been removed, since all the contents
   have been implemented in namespace ``std`` for at least two releases.
 
diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -676,6 +676,7 @@
   __system_error/error_condition.h
   __system_error/system_error.h
   __thread/formatter.h
+  __thread/id.h
   __thread/poll_with_backoff.h
   __thread/this_thread.h
   __thread/thread.h
diff --git a/libcxx/include/__condition_variable/condition_variable.h b/libcxx/include/__condition_variable/condition_variable.h
--- a/libcxx/include/__condition_variable/condition_variable.h
+++ b/libcxx/include/__condition_variable/condition_variable.h
@@ -20,6 +20,7 @@
 #include <__type_traits/enable_if.h>
 #include <__type_traits/is_floating_point.h>
 #include <__utility/move.h>
+#include <limits>
 #include <ratio>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
diff --git a/libcxx/include/__thread/formatter.h b/libcxx/include/__thread/formatter.h
--- a/libcxx/include/__thread/formatter.h
+++ b/libcxx/include/__thread/formatter.h
@@ -17,7 +17,7 @@
 #include <__format/formatter.h>
 #include <__format/formatter_integral.h>
 #include <__format/parser_std_format_spec.h>
-#include <__threading_support>
+#include <__thread/id.h>
 #include <__type_traits/conditional.h>
 #include <__type_traits/is_pointer.h>
 #include <__type_traits/is_same.h>
diff --git a/libcxx/include/__thread/id.h b/libcxx/include/__thread/id.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__thread/id.h
@@ -0,0 +1,147 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___THREAD_ID_H
+#define _LIBCPP___THREAD_ID_H
+
+#include <__compare/ordering.h>
+#include <__config>
+#include <__fwd/hash.h>
+#include <__threading_support>
+#include <iosfwd>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#ifndef _LIBCPP_HAS_NO_THREADS
+
+class _LIBCPP_EXPORTED_FROM_ABI thread;
+class _LIBCPP_EXPORTED_FROM_ABI __thread_id;
+
+namespace this_thread
+{
+
+_LIBCPP_INLINE_VISIBILITY __thread_id get_id() _NOEXCEPT;
+
+} // namespace this_thread
+
+template<> struct hash<__thread_id>;
+
+class _LIBCPP_TEMPLATE_VIS __thread_id
+{
+    // FIXME: pthread_t is a pointer on Darwin but a long on Linux.
+    // NULL is the no-thread value on Darwin.  Someone needs to check
+    // on other platforms.  We assume 0 works everywhere for now.
+    __libcpp_thread_id __id_;
+
+    static _LIBCPP_HIDE_FROM_ABI
+        bool __lt_impl(__thread_id __x, __thread_id __y) _NOEXCEPT
+        { // id==0 is always less than any other thread_id
+        if (__x.__id_ == 0) return __y.__id_ != 0;
+        if (__y.__id_ == 0) return false;
+        return  __libcpp_thread_id_less(__x.__id_, __y.__id_);
+        }
+
+public:
+    _LIBCPP_INLINE_VISIBILITY
+    __thread_id() _NOEXCEPT : __id_(0) {}
+
+    _LIBCPP_INLINE_VISIBILITY
+    void __reset() { __id_ = 0; }
+
+    friend _LIBCPP_HIDE_FROM_ABI bool operator==(__thread_id __x, __thread_id __y) _NOEXCEPT;
+#if _LIBCPP_STD_VER <= 17
+    friend _LIBCPP_HIDE_FROM_ABI bool operator<(__thread_id __x, __thread_id __y) _NOEXCEPT;
+#else // _LIBCPP_STD_VER <= 17
+    friend _LIBCPP_HIDE_FROM_ABI strong_ordering operator<=>(__thread_id __x, __thread_id __y) noexcept;
+#endif // _LIBCPP_STD_VER <= 17
+
+    template<class _CharT, class _Traits>
+    friend
+    _LIBCPP_INLINE_VISIBILITY
+    basic_ostream<_CharT, _Traits>&
+    operator<<(basic_ostream<_CharT, _Traits>& __os, __thread_id __id);
+
+private:
+    _LIBCPP_INLINE_VISIBILITY
+    __thread_id(__libcpp_thread_id __id) : __id_(__id) {}
+
+    _LIBCPP_HIDE_FROM_ABI friend __libcpp_thread_id __get_underlying_id(const __thread_id __id) { return __id.__id_; }
+
+    friend __thread_id this_thread::get_id() _NOEXCEPT;
+    friend class _LIBCPP_EXPORTED_FROM_ABI thread;
+    friend struct _LIBCPP_TEMPLATE_VIS hash<__thread_id>;
+};
+
+inline _LIBCPP_HIDE_FROM_ABI
+bool operator==(__thread_id __x, __thread_id __y) _NOEXCEPT {
+  // Don't pass id==0 to underlying routines
+  if (__x.__id_ == 0)
+    return __y.__id_ == 0;
+  if (__y.__id_ == 0)
+    return false;
+  return __libcpp_thread_id_equal(__x.__id_, __y.__id_);
+}
+
+#if _LIBCPP_STD_VER <= 17
+
+inline _LIBCPP_HIDE_FROM_ABI
+bool operator!=(__thread_id __x, __thread_id __y) _NOEXCEPT {
+  return !(__x == __y);
+}
+
+inline _LIBCPP_HIDE_FROM_ABI
+bool operator<(__thread_id __x, __thread_id __y) _NOEXCEPT {
+  return __thread_id::__lt_impl(__x.__id_, __y.__id_);
+}
+
+inline _LIBCPP_HIDE_FROM_ABI bool operator<=(__thread_id __x, __thread_id __y) _NOEXCEPT { return !(__y < __x); }
+inline _LIBCPP_HIDE_FROM_ABI bool operator>(__thread_id __x, __thread_id __y) _NOEXCEPT { return __y < __x; }
+inline _LIBCPP_HIDE_FROM_ABI bool operator>=(__thread_id __x, __thread_id __y) _NOEXCEPT { return !(__x < __y); }
+
+#else // _LIBCPP_STD_VER <= 17
+
+inline _LIBCPP_HIDE_FROM_ABI
+strong_ordering operator<=>(__thread_id __x, __thread_id __y) noexcept {
+  if (__x == __y)
+    return strong_ordering::equal;
+  if (__thread_id::__lt_impl(__x, __y))
+    return strong_ordering::less;
+  return strong_ordering::greater;
+}
+
+#endif // _LIBCPP_STD_VER <= 17
+
+namespace this_thread
+{
+
+_LIBCPP_INLINE_VISIBILITY __thread_id get_id() _NOEXCEPT;
+
+} // namespace this_thread
+
+namespace this_thread
+{
+
+inline _LIBCPP_INLINE_VISIBILITY
+__thread_id
+get_id() _NOEXCEPT
+{
+    return __libcpp_thread_get_current_id();
+}
+
+} // namespace this_thread
+
+#endif // !_LIBCPP_HAS_NO_THREADS
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___THREAD_ID_H
diff --git a/libcxx/include/__thread/thread.h b/libcxx/include/__thread/thread.h
--- a/libcxx/include/__thread/thread.h
+++ b/libcxx/include/__thread/thread.h
@@ -18,8 +18,10 @@
 #include <__memory/unique_ptr.h>
 #include <__mutex/mutex.h>
 #include <__system_error/system_error.h>
+#include <__thread/id.h>
 #include <__threading_support>
 #include <__utility/forward.h>
+#include <iosfwd>
 #include <tuple>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
diff --git a/libcxx/include/__threading_support b/libcxx/include/__threading_support
--- a/libcxx/include/__threading_support
+++ b/libcxx/include/__threading_support
@@ -13,13 +13,9 @@
 #include <__availability>
 #include <__chrono/convert_to_timespec.h>
 #include <__chrono/duration.h>
-#include <__compare/ordering.h>
 #include <__config>
-#include <__fwd/hash.h>
 #include <__thread/poll_with_backoff.h>
 #include <errno.h>
-#include <iosfwd>
-#include <limits>
 
 #ifdef __MVS__
 # include <__support/ibm/nanosleep.h>
@@ -589,118 +585,8 @@
 
 #endif
 
-
 #endif // !_LIBCPP_HAS_THREAD_LIBRARY_EXTERNAL || _LIBCPP_BUILDING_THREAD_LIBRARY_EXTERNAL
 
-class _LIBCPP_EXPORTED_FROM_ABI thread;
-class _LIBCPP_EXPORTED_FROM_ABI __thread_id;
-
-namespace this_thread
-{
-
-_LIBCPP_INLINE_VISIBILITY __thread_id get_id() _NOEXCEPT;
-
-} // namespace this_thread
-
-template<> struct hash<__thread_id>;
-
-class _LIBCPP_TEMPLATE_VIS __thread_id
-{
-    // FIXME: pthread_t is a pointer on Darwin but a long on Linux.
-    // NULL is the no-thread value on Darwin.  Someone needs to check
-    // on other platforms.  We assume 0 works everywhere for now.
-    __libcpp_thread_id __id_;
-
-    static _LIBCPP_HIDE_FROM_ABI
-        bool __lt_impl(__thread_id __x, __thread_id __y) _NOEXCEPT
-        { // id==0 is always less than any other thread_id
-        if (__x.__id_ == 0) return __y.__id_ != 0;
-        if (__y.__id_ == 0) return false;
-        return  __libcpp_thread_id_less(__x.__id_, __y.__id_);
-        }
-
-public:
-    _LIBCPP_INLINE_VISIBILITY
-    __thread_id() _NOEXCEPT : __id_(0) {}
-
-    _LIBCPP_INLINE_VISIBILITY
-    void __reset() { __id_ = 0; }
-
-    friend _LIBCPP_HIDE_FROM_ABI bool operator==(__thread_id __x, __thread_id __y) _NOEXCEPT;
-#if _LIBCPP_STD_VER <= 17
-    friend _LIBCPP_HIDE_FROM_ABI bool operator<(__thread_id __x, __thread_id __y) _NOEXCEPT;
-#else // _LIBCPP_STD_VER <= 17
-    friend _LIBCPP_HIDE_FROM_ABI strong_ordering operator<=>(__thread_id __x, __thread_id __y) noexcept;
-#endif // _LIBCPP_STD_VER <= 17
-
-    template<class _CharT, class _Traits>
-    friend
-    _LIBCPP_INLINE_VISIBILITY
-    basic_ostream<_CharT, _Traits>&
-    operator<<(basic_ostream<_CharT, _Traits>& __os, __thread_id __id);
-
-private:
-    _LIBCPP_INLINE_VISIBILITY
-    __thread_id(__libcpp_thread_id __id) : __id_(__id) {}
-
-    _LIBCPP_HIDE_FROM_ABI friend __libcpp_thread_id __get_underlying_id(const __thread_id __id) { return __id.__id_; }
-
-    friend __thread_id this_thread::get_id() _NOEXCEPT;
-    friend class _LIBCPP_EXPORTED_FROM_ABI thread;
-    friend struct _LIBCPP_TEMPLATE_VIS hash<__thread_id>;
-};
-
-inline _LIBCPP_HIDE_FROM_ABI
-bool operator==(__thread_id __x, __thread_id __y) _NOEXCEPT {
-  // Don't pass id==0 to underlying routines
-  if (__x.__id_ == 0)
-    return __y.__id_ == 0;
-  if (__y.__id_ == 0)
-    return false;
-  return __libcpp_thread_id_equal(__x.__id_, __y.__id_);
-}
-
-#if _LIBCPP_STD_VER <= 17
-
-inline _LIBCPP_HIDE_FROM_ABI
-bool operator!=(__thread_id __x, __thread_id __y) _NOEXCEPT {
-  return !(__x == __y);
-}
-
-inline _LIBCPP_HIDE_FROM_ABI
-bool operator<(__thread_id __x, __thread_id __y) _NOEXCEPT {
-  return __thread_id::__lt_impl(__x.__id_, __y.__id_);
-}
-
-inline _LIBCPP_HIDE_FROM_ABI bool operator<=(__thread_id __x, __thread_id __y) _NOEXCEPT { return !(__y < __x); }
-inline _LIBCPP_HIDE_FROM_ABI bool operator>(__thread_id __x, __thread_id __y) _NOEXCEPT { return __y < __x; }
-inline _LIBCPP_HIDE_FROM_ABI bool operator>=(__thread_id __x, __thread_id __y) _NOEXCEPT { return !(__x < __y); }
-
-#else // _LIBCPP_STD_VER <= 17
-
-inline _LIBCPP_HIDE_FROM_ABI
-strong_ordering operator<=>(__thread_id __x, __thread_id __y) noexcept {
-  if (__x == __y)
-    return strong_ordering::equal;
-  if (__thread_id::__lt_impl(__x, __y))
-    return strong_ordering::less;
-  return strong_ordering::greater;
-}
-
-#endif // _LIBCPP_STD_VER <= 17
-
-namespace this_thread
-{
-
-inline _LIBCPP_INLINE_VISIBILITY
-__thread_id
-get_id() _NOEXCEPT
-{
-    return __libcpp_thread_get_current_id();
-}
-
-} // namespace this_thread
-
 #endif // !_LIBCPP_HAS_NO_THREADS
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/module.modulemap.in b/libcxx/include/module.modulemap.in
--- a/libcxx/include/module.modulemap.in
+++ b/libcxx/include/module.modulemap.in
@@ -1619,6 +1619,7 @@
 
     module __thread {
       module formatter            { private header "__thread/formatter.h" }
+      module id                   { private header "__thread/id.h" }
       module poll_with_backoff    { private header "__thread/poll_with_backoff.h" }
       module this_thread          { private header "__thread/this_thread.h" }
       module thread               { private header "__thread/thread.h" }
diff --git a/libcxx/include/mutex b/libcxx/include/mutex
--- a/libcxx/include/mutex
+++ b/libcxx/include/mutex
@@ -196,9 +196,11 @@
 #include <__mutex/mutex.h>
 #include <__mutex/tag_types.h>
 #include <__mutex/unique_lock.h>
+#include <__thread/id.h>
 #include <__threading_support>
 #include <__utility/forward.h>
 #include <cstdint>
+#include <limits>
 #ifndef _LIBCPP_CXX03_LANG
 # include <tuple>
 #endif
diff --git a/libcxx/src/mutex.cpp b/libcxx/src/mutex.cpp
--- a/libcxx/src/mutex.cpp
+++ b/libcxx/src/mutex.cpp
@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include <__assert>
+#include <__thread/id.h>
 #include <limits>
 #include <mutex>
 
diff --git a/libcxx/test/libcxx/transitive_includes/cxx03.csv b/libcxx/test/libcxx/transitive_includes/cxx03.csv
--- a/libcxx/test/libcxx/transitive_includes/cxx03.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx03.csv
@@ -58,7 +58,6 @@
 atomic cstdlib
 atomic cstring
 atomic ctime
-atomic iosfwd
 atomic limits
 atomic ratio
 atomic type_traits
@@ -69,7 +68,6 @@
 barrier cstdint
 barrier cstring
 barrier ctime
-barrier iosfwd
 barrier iterator
 barrier limits
 barrier memory
@@ -173,7 +171,6 @@
 condition_variable cstring
 condition_variable ctime
 condition_variable initializer_list
-condition_variable iosfwd
 condition_variable limits
 condition_variable new
 condition_variable ratio
@@ -455,7 +452,6 @@
 latch cstdint
 latch cstring
 latch ctime
-latch iosfwd
 latch limits
 latch ratio
 latch type_traits
@@ -591,7 +587,6 @@
 numeric execution
 numeric functional
 numeric initializer_list
-numeric iosfwd
 numeric iterator
 numeric limits
 numeric new
@@ -729,7 +724,6 @@
 semaphore cstdint
 semaphore cstring
 semaphore ctime
-semaphore iosfwd
 semaphore limits
 semaphore ratio
 semaphore type_traits
@@ -751,7 +745,6 @@
 shared_mutex cerrno
 shared_mutex cstddef
 shared_mutex ctime
-shared_mutex iosfwd
 shared_mutex limits
 shared_mutex ratio
 shared_mutex stdexcept
diff --git a/libcxx/test/libcxx/transitive_includes/cxx11.csv b/libcxx/test/libcxx/transitive_includes/cxx11.csv
--- a/libcxx/test/libcxx/transitive_includes/cxx11.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx11.csv
@@ -58,7 +58,6 @@
 atomic cstdlib
 atomic cstring
 atomic ctime
-atomic iosfwd
 atomic limits
 atomic ratio
 atomic type_traits
@@ -69,7 +68,6 @@
 barrier cstdint
 barrier cstring
 barrier ctime
-barrier iosfwd
 barrier iterator
 barrier limits
 barrier memory
@@ -173,7 +171,6 @@
 condition_variable cstring
 condition_variable ctime
 condition_variable initializer_list
-condition_variable iosfwd
 condition_variable limits
 condition_variable new
 condition_variable ratio
@@ -455,7 +452,6 @@
 latch cstdint
 latch cstring
 latch ctime
-latch iosfwd
 latch limits
 latch ratio
 latch type_traits
@@ -592,7 +588,6 @@
 numeric execution
 numeric functional
 numeric initializer_list
-numeric iosfwd
 numeric iterator
 numeric limits
 numeric new
@@ -730,7 +725,6 @@
 semaphore cstdint
 semaphore cstring
 semaphore ctime
-semaphore iosfwd
 semaphore limits
 semaphore ratio
 semaphore type_traits
@@ -752,7 +746,6 @@
 shared_mutex cerrno
 shared_mutex cstddef
 shared_mutex ctime
-shared_mutex iosfwd
 shared_mutex limits
 shared_mutex ratio
 shared_mutex stdexcept
diff --git a/libcxx/test/libcxx/transitive_includes/cxx14.csv b/libcxx/test/libcxx/transitive_includes/cxx14.csv
--- a/libcxx/test/libcxx/transitive_includes/cxx14.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx14.csv
@@ -58,7 +58,6 @@
 atomic cstdlib
 atomic cstring
 atomic ctime
-atomic iosfwd
 atomic limits
 atomic ratio
 atomic type_traits
@@ -69,7 +68,6 @@
 barrier cstdint
 barrier cstring
 barrier ctime
-barrier iosfwd
 barrier iterator
 barrier limits
 barrier memory
@@ -173,7 +171,6 @@
 condition_variable cstring
 condition_variable ctime
 condition_variable initializer_list
-condition_variable iosfwd
 condition_variable limits
 condition_variable new
 condition_variable ratio
@@ -457,7 +454,6 @@
 latch cstdint
 latch cstring
 latch ctime
-latch iosfwd
 latch limits
 latch ratio
 latch type_traits
@@ -594,7 +590,6 @@
 numeric execution
 numeric functional
 numeric initializer_list
-numeric iosfwd
 numeric iterator
 numeric limits
 numeric new
@@ -732,7 +727,6 @@
 semaphore cstdint
 semaphore cstring
 semaphore ctime
-semaphore iosfwd
 semaphore limits
 semaphore ratio
 semaphore type_traits
@@ -754,7 +748,6 @@
 shared_mutex cerrno
 shared_mutex cstddef
 shared_mutex ctime
-shared_mutex iosfwd
 shared_mutex limits
 shared_mutex ratio
 shared_mutex stdexcept
diff --git a/libcxx/test/libcxx/transitive_includes/cxx17.csv b/libcxx/test/libcxx/transitive_includes/cxx17.csv
--- a/libcxx/test/libcxx/transitive_includes/cxx17.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx17.csv
@@ -58,7 +58,6 @@
 atomic cstdlib
 atomic cstring
 atomic ctime
-atomic iosfwd
 atomic limits
 atomic ratio
 atomic type_traits
@@ -69,7 +68,6 @@
 barrier cstdint
 barrier cstring
 barrier ctime
-barrier iosfwd
 barrier iterator
 barrier limits
 barrier memory
@@ -173,7 +171,6 @@
 condition_variable cstring
 condition_variable ctime
 condition_variable initializer_list
-condition_variable iosfwd
 condition_variable limits
 condition_variable new
 condition_variable ratio
@@ -457,7 +454,6 @@
 latch cstdint
 latch cstring
 latch ctime
-latch iosfwd
 latch limits
 latch ratio
 latch type_traits
@@ -594,7 +590,6 @@
 numeric execution
 numeric functional
 numeric initializer_list
-numeric iosfwd
 numeric iterator
 numeric limits
 numeric new
@@ -732,7 +727,6 @@
 semaphore cstdint
 semaphore cstring
 semaphore ctime
-semaphore iosfwd
 semaphore limits
 semaphore ratio
 semaphore type_traits
@@ -754,7 +748,6 @@
 shared_mutex cerrno
 shared_mutex cstddef
 shared_mutex ctime
-shared_mutex iosfwd
 shared_mutex limits
 shared_mutex ratio
 shared_mutex stdexcept
diff --git a/libcxx/test/libcxx/transitive_includes/cxx20.csv b/libcxx/test/libcxx/transitive_includes/cxx20.csv
--- a/libcxx/test/libcxx/transitive_includes/cxx20.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx20.csv
@@ -57,7 +57,6 @@
 atomic cstdlib
 atomic cstring
 atomic ctime
-atomic iosfwd
 atomic limits
 atomic ratio
 atomic type_traits
@@ -68,7 +67,6 @@
 barrier cstdint
 barrier cstring
 barrier ctime
-barrier iosfwd
 barrier iterator
 barrier limits
 barrier memory
@@ -180,7 +178,6 @@
 condition_variable cstring
 condition_variable ctime
 condition_variable initializer_list
-condition_variable iosfwd
 condition_variable limits
 condition_variable new
 condition_variable ratio
@@ -463,7 +460,6 @@
 latch cstdint
 latch cstring
 latch ctime
-latch iosfwd
 latch limits
 latch ratio
 latch type_traits
@@ -600,7 +596,6 @@
 numeric execution
 numeric functional
 numeric initializer_list
-numeric iosfwd
 numeric iterator
 numeric limits
 numeric new
@@ -738,7 +733,6 @@
 semaphore cstdint
 semaphore cstring
 semaphore ctime
-semaphore iosfwd
 semaphore limits
 semaphore ratio
 semaphore type_traits
@@ -760,7 +754,6 @@
 shared_mutex cerrno
 shared_mutex cstddef
 shared_mutex ctime
-shared_mutex iosfwd
 shared_mutex limits
 shared_mutex ratio
 shared_mutex stdexcept
diff --git a/libcxx/test/libcxx/transitive_includes/cxx23.csv b/libcxx/test/libcxx/transitive_includes/cxx23.csv
--- a/libcxx/test/libcxx/transitive_includes/cxx23.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx23.csv
@@ -32,7 +32,6 @@
 atomic cstdlib
 atomic cstring
 atomic ctime
-atomic iosfwd
 atomic limits
 atomic ratio
 atomic version
@@ -40,7 +39,6 @@
 barrier cstdint
 barrier cstring
 barrier ctime
-barrier iosfwd
 barrier limits
 barrier new
 barrier ratio
@@ -330,7 +328,6 @@
 latch cstdint
 latch cstring
 latch ctime
-latch iosfwd
 latch limits
 latch ratio
 latch version
@@ -427,7 +424,6 @@
 numeric ctime
 numeric execution
 numeric initializer_list
-numeric iosfwd
 numeric limits
 numeric new
 numeric ratio
@@ -519,7 +515,6 @@
 semaphore cstdint
 semaphore cstring
 semaphore ctime
-semaphore iosfwd
 semaphore limits
 semaphore ratio
 semaphore version
@@ -536,7 +531,6 @@
 shared_mutex cerrno
 shared_mutex cstddef
 shared_mutex ctime
-shared_mutex iosfwd
 shared_mutex limits
 shared_mutex ratio
 shared_mutex stdexcept
diff --git a/libcxx/test/libcxx/transitive_includes/cxx26.csv b/libcxx/test/libcxx/transitive_includes/cxx26.csv
--- a/libcxx/test/libcxx/transitive_includes/cxx26.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx26.csv
@@ -32,7 +32,6 @@
 atomic cstdlib
 atomic cstring
 atomic ctime
-atomic iosfwd
 atomic limits
 atomic ratio
 atomic version
@@ -40,7 +39,6 @@
 barrier cstdint
 barrier cstring
 barrier ctime
-barrier iosfwd
 barrier limits
 barrier new
 barrier ratio
@@ -330,7 +328,6 @@
 latch cstdint
 latch cstring
 latch ctime
-latch iosfwd
 latch limits
 latch ratio
 latch version
@@ -427,7 +424,6 @@
 numeric ctime
 numeric execution
 numeric initializer_list
-numeric iosfwd
 numeric limits
 numeric new
 numeric ratio
@@ -519,7 +515,6 @@
 semaphore cstdint
 semaphore cstring
 semaphore ctime
-semaphore iosfwd
 semaphore limits
 semaphore ratio
 semaphore version
@@ -536,7 +531,6 @@
 shared_mutex cerrno
 shared_mutex cstddef
 shared_mutex ctime
-shared_mutex iosfwd
 shared_mutex limits
 shared_mutex ratio
 shared_mutex stdexcept
diff --git a/libcxx/test/std/thread/thread.threads/thread.thread.class/thread.thread.id/thread_id.pass.cpp b/libcxx/test/std/thread/thread.threads/thread.thread.class/thread.thread.id/thread_id.pass.cpp
--- a/libcxx/test/std/thread/thread.threads/thread.thread.class/thread.thread.id/thread_id.pass.cpp
+++ b/libcxx/test/std/thread/thread.threads/thread.thread.class/thread.thread.id/thread_id.pass.cpp
@@ -18,8 +18,9 @@
 
 // Not very portable
 
-#include <thread>
 #include <cassert>
+#include <functional>
+#include <thread>
 
 #include "test_macros.h"
 
diff --git a/libcxx/utils/data/ignore_format.txt b/libcxx/utils/data/ignore_format.txt
--- a/libcxx/utils/data/ignore_format.txt
+++ b/libcxx/utils/data/ignore_format.txt
@@ -474,6 +474,7 @@
 libcxx/include/__system_error/errc.h
 libcxx/include/thread
 libcxx/include/__thread/formatter.h
+libcxx/include/__thread/id.h
 libcxx/include/__threading_support
 libcxx/include/__thread/poll_with_backoff.h
 libcxx/include/__thread/this_thread.h