diff --git a/libcxx/docs/FeatureTestMacroTable.rst b/libcxx/docs/FeatureTestMacroTable.rst
index db24b65caca6c..3c4a13332661e 100644
--- a/libcxx/docs/FeatureTestMacroTable.rst
+++ b/libcxx/docs/FeatureTestMacroTable.rst
@@ -278,7 +278,7 @@ Status
     ---------------------------------------------------------- -----------------
     ``__cpp_lib_shift``                                        ``201806L``
     ---------------------------------------------------------- -----------------
-    ``__cpp_lib_smart_ptr_for_overwrite``                      *unimplemented*
+    ``__cpp_lib_smart_ptr_for_overwrite``                      ``202002L``
     ---------------------------------------------------------- -----------------
     ``__cpp_lib_source_location``                              ``201907L``
     ---------------------------------------------------------- -----------------
diff --git a/libcxx/docs/Status/Cxx20Papers.csv b/libcxx/docs/Status/Cxx20Papers.csv
index c8c30a315fcaf..66cb1012eceb9 100644
--- a/libcxx/docs/Status/Cxx20Papers.csv
+++ b/libcxx/docs/Status/Cxx20Papers.csv
@@ -68,7 +68,7 @@
 "`P0972R0 <https://wg21.link/P0972R0>`__","<chrono> ``zero()``\ , ``min()``\ , and ``max()``\  should be noexcept","2018-11 (San Diego)","|Complete|","8",""
 "`P1006R1 <https://wg21.link/P1006R1>`__","Constexpr in std::pointer_traits","2018-11 (San Diego)","|Complete|","8",""
 "`P1007R3 <https://wg21.link/P1007R3>`__","``std::assume_aligned``\ ","2018-11 (San Diego)","|Complete|","15",""
-"`P1020R1 <https://wg21.link/P1020R1>`__","Smart pointer creation with default initialization","2018-11 (San Diego)","|Complete|","16",""
+"`P1020R1 <https://wg21.link/P1020R1>`__","Smart pointer creation with default initialization","2018-11 (San Diego)","|Complete|","16","The feature-test macro was not set until LLVM 20."
 "`P1032R1 <https://wg21.link/P1032R1>`__","Misc constexpr bits","2018-11 (San Diego)","|Complete|","13",""
 "`P1085R2 <https://wg21.link/P1085R2>`__","Should Span be Regular?","2018-11 (San Diego)","|Complete|","8",""
 "`P1123R0 <https://wg21.link/P1123R0>`__","Editorial Guidance for merging P0019r8 and P0528r3","2018-11 (San Diego)","","",""
@@ -177,7 +177,7 @@
 "`P1963R0 <https://wg21.link/P1963R0>`__","Fixing US 313","2020-02 (Prague)","","",""
 "`P1964R2 <https://wg21.link/P1964R2>`__","Wording for boolean-testable","2020-02 (Prague)","|Complete|","13",""
 "`P1970R2 <https://wg21.link/P1970R2>`__","Consistency for size() functions: Add ranges::ssize","2020-02 (Prague)","|Complete|","15",""
-"`P1973R1 <https://wg21.link/P1973R1>`__","Rename ""_default_init"" Functions, Rev1","2020-02 (Prague)","|Complete|","16",""
+"`P1973R1 <https://wg21.link/P1973R1>`__","Rename ""_default_init"" Functions, Rev1","2020-02 (Prague)","|Complete|","16","The feature-test macro was not set until LLVM 20."
 "`P1976R2 <https://wg21.link/P1976R2>`__","Fixed-size span construction from dynamic range","2020-02 (Prague)","|Complete|","11",""
 "`P1981R0 <https://wg21.link/P1981R0>`__","Rename leap to leap_second","2020-02 (Prague)","|Complete|","19",""
 "`P1982R0 <https://wg21.link/P1982R0>`__","Rename link to time_zone_link","2020-02 (Prague)","|Complete|","19",""
diff --git a/libcxx/include/version b/libcxx/include/version
index cb75f3b2db681..571b6e39381d1 100644
--- a/libcxx/include/version
+++ b/libcxx/include/version
@@ -443,7 +443,7 @@ __cpp_lib_void_t                                        201411L <type_traits>
 # undef  __cpp_lib_shared_ptr_arrays
 # define __cpp_lib_shared_ptr_arrays                    201707L
 # define __cpp_lib_shift                                201806L
-// # define __cpp_lib_smart_ptr_for_overwrite              202002L
+# define __cpp_lib_smart_ptr_for_overwrite              202002L
 # define __cpp_lib_source_location                      201907L
 # define __cpp_lib_span                                 202002L
 # define __cpp_lib_ssize                                201902L
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/memory.version.compile.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/memory.version.compile.pass.cpp
index 315058f7f4637..0094bed44be07 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/memory.version.compile.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/memory.version.compile.pass.cpp
@@ -390,17 +390,11 @@
 #   error "__cpp_lib_shared_ptr_weak_type should have the value 201606L in c++20"
 # endif
 
-# if !defined(_LIBCPP_VERSION)
-#   ifndef __cpp_lib_smart_ptr_for_overwrite
-#     error "__cpp_lib_smart_ptr_for_overwrite should be defined in c++20"
-#   endif
-#   if __cpp_lib_smart_ptr_for_overwrite != 202002L
-#     error "__cpp_lib_smart_ptr_for_overwrite should have the value 202002L in c++20"
-#   endif
-# else // _LIBCPP_VERSION
-#   ifdef __cpp_lib_smart_ptr_for_overwrite
-#     error "__cpp_lib_smart_ptr_for_overwrite should not be defined because it is unimplemented in libc++!"
-#   endif
+# ifndef __cpp_lib_smart_ptr_for_overwrite
+#   error "__cpp_lib_smart_ptr_for_overwrite should be defined in c++20"
+# endif
+# if __cpp_lib_smart_ptr_for_overwrite != 202002L
+#   error "__cpp_lib_smart_ptr_for_overwrite should have the value 202002L in c++20"
 # endif
 
 # ifdef __cpp_lib_smart_ptr_owner_equality
@@ -521,17 +515,11 @@
 #   error "__cpp_lib_shared_ptr_weak_type should have the value 201606L in c++23"
 # endif
 
-# if !defined(_LIBCPP_VERSION)
-#   ifndef __cpp_lib_smart_ptr_for_overwrite
-#     error "__cpp_lib_smart_ptr_for_overwrite should be defined in c++23"
-#   endif
-#   if __cpp_lib_smart_ptr_for_overwrite != 202002L
-#     error "__cpp_lib_smart_ptr_for_overwrite should have the value 202002L in c++23"
-#   endif
-# else // _LIBCPP_VERSION
-#   ifdef __cpp_lib_smart_ptr_for_overwrite
-#     error "__cpp_lib_smart_ptr_for_overwrite should not be defined because it is unimplemented in libc++!"
-#   endif
+# ifndef __cpp_lib_smart_ptr_for_overwrite
+#   error "__cpp_lib_smart_ptr_for_overwrite should be defined in c++23"
+# endif
+# if __cpp_lib_smart_ptr_for_overwrite != 202002L
+#   error "__cpp_lib_smart_ptr_for_overwrite should have the value 202002L in c++23"
 # endif
 
 # ifdef __cpp_lib_smart_ptr_owner_equality
@@ -652,17 +640,11 @@
 #   error "__cpp_lib_shared_ptr_weak_type should have the value 201606L in c++26"
 # endif
 
-# if !defined(_LIBCPP_VERSION)
-#   ifndef __cpp_lib_smart_ptr_for_overwrite
-#     error "__cpp_lib_smart_ptr_for_overwrite should be defined in c++26"
-#   endif
-#   if __cpp_lib_smart_ptr_for_overwrite != 202002L
-#     error "__cpp_lib_smart_ptr_for_overwrite should have the value 202002L in c++26"
-#   endif
-# else // _LIBCPP_VERSION
-#   ifdef __cpp_lib_smart_ptr_for_overwrite
-#     error "__cpp_lib_smart_ptr_for_overwrite should not be defined because it is unimplemented in libc++!"
-#   endif
+# ifndef __cpp_lib_smart_ptr_for_overwrite
+#   error "__cpp_lib_smart_ptr_for_overwrite should be defined in c++26"
+# endif
+# if __cpp_lib_smart_ptr_for_overwrite != 202002L
+#   error "__cpp_lib_smart_ptr_for_overwrite should have the value 202002L in c++26"
 # endif
 
 # if !defined(_LIBCPP_VERSION)
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp
index 5deaee16895f6..74db80c4d642e 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/version.version.compile.pass.cpp
@@ -4344,17 +4344,11 @@
 #   error "__cpp_lib_shift should have the value 201806L in c++20"
 # endif
 
-# if !defined(_LIBCPP_VERSION)
-#   ifndef __cpp_lib_smart_ptr_for_overwrite
-#     error "__cpp_lib_smart_ptr_for_overwrite should be defined in c++20"
-#   endif
-#   if __cpp_lib_smart_ptr_for_overwrite != 202002L
-#     error "__cpp_lib_smart_ptr_for_overwrite should have the value 202002L in c++20"
-#   endif
-# else // _LIBCPP_VERSION
-#   ifdef __cpp_lib_smart_ptr_for_overwrite
-#     error "__cpp_lib_smart_ptr_for_overwrite should not be defined because it is unimplemented in libc++!"
-#   endif
+# ifndef __cpp_lib_smart_ptr_for_overwrite
+#   error "__cpp_lib_smart_ptr_for_overwrite should be defined in c++20"
+# endif
+# if __cpp_lib_smart_ptr_for_overwrite != 202002L
+#   error "__cpp_lib_smart_ptr_for_overwrite should have the value 202002L in c++20"
 # endif
 
 # ifdef __cpp_lib_smart_ptr_owner_equality
@@ -5929,17 +5923,11 @@
 #   error "__cpp_lib_shift should have the value 201806L in c++23"
 # endif
 
-# if !defined(_LIBCPP_VERSION)
-#   ifndef __cpp_lib_smart_ptr_for_overwrite
-#     error "__cpp_lib_smart_ptr_for_overwrite should be defined in c++23"
-#   endif
-#   if __cpp_lib_smart_ptr_for_overwrite != 202002L
-#     error "__cpp_lib_smart_ptr_for_overwrite should have the value 202002L in c++23"
-#   endif
-# else // _LIBCPP_VERSION
-#   ifdef __cpp_lib_smart_ptr_for_overwrite
-#     error "__cpp_lib_smart_ptr_for_overwrite should not be defined because it is unimplemented in libc++!"
-#   endif
+# ifndef __cpp_lib_smart_ptr_for_overwrite
+#   error "__cpp_lib_smart_ptr_for_overwrite should be defined in c++23"
+# endif
+# if __cpp_lib_smart_ptr_for_overwrite != 202002L
+#   error "__cpp_lib_smart_ptr_for_overwrite should have the value 202002L in c++23"
 # endif
 
 # ifdef __cpp_lib_smart_ptr_owner_equality
@@ -7829,17 +7817,11 @@
 #   error "__cpp_lib_shift should have the value 201806L in c++26"
 # endif
 
-# if !defined(_LIBCPP_VERSION)
-#   ifndef __cpp_lib_smart_ptr_for_overwrite
-#     error "__cpp_lib_smart_ptr_for_overwrite should be defined in c++26"
-#   endif
-#   if __cpp_lib_smart_ptr_for_overwrite != 202002L
-#     error "__cpp_lib_smart_ptr_for_overwrite should have the value 202002L in c++26"
-#   endif
-# else // _LIBCPP_VERSION
-#   ifdef __cpp_lib_smart_ptr_for_overwrite
-#     error "__cpp_lib_smart_ptr_for_overwrite should not be defined because it is unimplemented in libc++!"
-#   endif
+# ifndef __cpp_lib_smart_ptr_for_overwrite
+#   error "__cpp_lib_smart_ptr_for_overwrite should be defined in c++26"
+# endif
+# if __cpp_lib_smart_ptr_for_overwrite != 202002L
+#   error "__cpp_lib_smart_ptr_for_overwrite should have the value 202002L in c++26"
 # endif
 
 # if !defined(_LIBCPP_VERSION)
diff --git a/libcxx/utils/generate_feature_test_macro_components.py b/libcxx/utils/generate_feature_test_macro_components.py
index 197d6bbc69222..c32d8d77c8857 100755
--- a/libcxx/utils/generate_feature_test_macro_components.py
+++ b/libcxx/utils/generate_feature_test_macro_components.py
@@ -1196,7 +1196,6 @@ def add_version_header(tc):
             "name": "__cpp_lib_smart_ptr_for_overwrite",
             "values": {"c++20": 202002},
             "headers": ["memory"],
-            "unimplemented": True,
         },
         {
             "name": "__cpp_lib_smart_ptr_owner_equality",