diff --git a/libcxx/test/extensions/libcxx/depr/depr.c.headers/extern_c.pass.cpp b/libcxx/test/extensions/libcxx/depr/depr.c.headers/extern_c.pass.cpp
index f756aacbc1cd5..33b55c4bb195a 100644
--- a/libcxx/test/extensions/libcxx/depr/depr.c.headers/extern_c.pass.cpp
+++ b/libcxx/test/extensions/libcxx/depr/depr.c.headers/extern_c.pass.cpp
@@ -10,14 +10,10 @@
 // that we don't want to support and can't support with LSV enabled.
 // UNSUPPORTED: clang-modules-build
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
 // Sometimes C++'s <foo.h> headers get included within extern "C" contexts. This
 // is ill-formed (no diagnostic required), per [using.headers]p3, but we permit
 // it as an extension.
 
-#include <__config>
-
 extern "C" {
 #include <assert.h>
 // complex.h is not supported in extern "C".
diff --git a/libcxx/test/libcxx-03/algorithms/half_positive.pass.cpp b/libcxx/test/libcxx-03/algorithms/half_positive.pass.cpp
index 88a18e8592921..292fcf356554b 100644
--- a/libcxx/test/libcxx-03/algorithms/half_positive.pass.cpp
+++ b/libcxx/test/libcxx-03/algorithms/half_positive.pass.cpp
@@ -11,9 +11,7 @@
 // __half_positive divides an integer number by 2 as unsigned number for known types.
 // It can be an important optimization for lower bound, for example.
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
-#include <__algorithm/half_positive.h>
+#include <__cxx03/__algorithm/half_positive.h>
 #include <cassert>
 #include <cstddef>
 #include <limits>
diff --git a/libcxx/test/libcxx-03/assertions/default_verbose_abort.pass.cpp b/libcxx/test/libcxx-03/assertions/default_verbose_abort.pass.cpp
index 803868b757794..27169da5e1c41 100644
--- a/libcxx/test/libcxx-03/assertions/default_verbose_abort.pass.cpp
+++ b/libcxx/test/libcxx-03/assertions/default_verbose_abort.pass.cpp
@@ -9,9 +9,7 @@
 // Test that the default verbose termination function aborts the program.
 // XFAIL: availability-verbose_abort-missing
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
-#include <__verbose_abort>
+#include <__cxx03/__verbose_abort>
 #include <csignal>
 #include <cstdlib>
 
diff --git a/libcxx/test/libcxx-03/assertions/modes/none.pass.cpp b/libcxx/test/libcxx-03/assertions/modes/none.pass.cpp
index b64290a31a129..e79dee906ae69 100644
--- a/libcxx/test/libcxx-03/assertions/modes/none.pass.cpp
+++ b/libcxx/test/libcxx-03/assertions/modes/none.pass.cpp
@@ -11,9 +11,7 @@
 
 // REQUIRES: libcpp-hardening-mode=none
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
-#include <__assert>
+#include <__cxx03/__assert>
 #include <cassert>
 
 bool executed_condition = false;
diff --git a/libcxx/test/libcxx-03/assertions/single_expression.pass.cpp b/libcxx/test/libcxx-03/assertions/single_expression.pass.cpp
index 474edc9dc0833..bbda6f11e4f6a 100644
--- a/libcxx/test/libcxx-03/assertions/single_expression.pass.cpp
+++ b/libcxx/test/libcxx-03/assertions/single_expression.pass.cpp
@@ -10,9 +10,7 @@
 // This is useful so we can use them  in places that require an expression, such as
 // in a constructor initializer list.
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
-#include <__assert>
+#include <__cxx03/__assert>
 #include <cassert>
 
 void f() {
diff --git a/libcxx/test/libcxx-03/containers/associative/tree_balance_after_insert.pass.cpp b/libcxx/test/libcxx-03/containers/associative/tree_balance_after_insert.pass.cpp
index ccd84af44c3a5..c1e7406169708 100644
--- a/libcxx/test/libcxx-03/containers/associative/tree_balance_after_insert.pass.cpp
+++ b/libcxx/test/libcxx-03/containers/associative/tree_balance_after_insert.pass.cpp
@@ -13,9 +13,7 @@
 // void
 // __tree_balance_after_insert(_NodePtr __root, _NodePtr __x)
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
-#include <__tree>
+#include <__cxx03/__tree>
 #include <cassert>
 
 #include "test_macros.h"
diff --git a/libcxx/test/libcxx-03/containers/associative/tree_key_value_traits.pass.cpp b/libcxx/test/libcxx-03/containers/associative/tree_key_value_traits.pass.cpp
index 04dcb8f54fafc..630f5c8621407 100644
--- a/libcxx/test/libcxx-03/containers/associative/tree_key_value_traits.pass.cpp
+++ b/libcxx/test/libcxx-03/containers/associative/tree_key_value_traits.pass.cpp
@@ -6,9 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
-#include <__tree>
+#include <__cxx03/__tree>
 #include <map>
 #include <set>
 #include <type_traits>
diff --git a/libcxx/test/libcxx-03/containers/associative/tree_left_rotate.pass.cpp b/libcxx/test/libcxx-03/containers/associative/tree_left_rotate.pass.cpp
index d97a1c89f1f70..67edca72b7b4c 100644
--- a/libcxx/test/libcxx-03/containers/associative/tree_left_rotate.pass.cpp
+++ b/libcxx/test/libcxx-03/containers/associative/tree_left_rotate.pass.cpp
@@ -13,9 +13,7 @@
 // void
 // __tree_left_rotate(_NodePtr __x);
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
-#include <__tree>
+#include <__cxx03/__tree>
 #include <cassert>
 
 #include "test_macros.h"
diff --git a/libcxx/test/libcxx-03/containers/associative/tree_remove.pass.cpp b/libcxx/test/libcxx-03/containers/associative/tree_remove.pass.cpp
index e543c3360a685..d4eae2c957630 100644
--- a/libcxx/test/libcxx-03/containers/associative/tree_remove.pass.cpp
+++ b/libcxx/test/libcxx-03/containers/associative/tree_remove.pass.cpp
@@ -13,9 +13,7 @@
 // void
 // __tree_remove(_NodePtr __root, _NodePtr __z)
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
-#include <__tree>
+#include <__cxx03/__tree>
 #include <cassert>
 
 #include "test_macros.h"
diff --git a/libcxx/test/libcxx-03/containers/associative/tree_right_rotate.pass.cpp b/libcxx/test/libcxx-03/containers/associative/tree_right_rotate.pass.cpp
index b86446f5be101..19e9a8f464648 100644
--- a/libcxx/test/libcxx-03/containers/associative/tree_right_rotate.pass.cpp
+++ b/libcxx/test/libcxx-03/containers/associative/tree_right_rotate.pass.cpp
@@ -13,9 +13,7 @@
 // void
 // __tree_right_rotate(_NodePtr __x);
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
-#include <__tree>
+#include <__cxx03/__tree>
 #include <cassert>
 
 #include "test_macros.h"
diff --git a/libcxx/test/libcxx-03/containers/unord/key_value_traits.pass.cpp b/libcxx/test/libcxx-03/containers/unord/key_value_traits.pass.cpp
index e00a028489a72..a117884791062 100644
--- a/libcxx/test/libcxx-03/containers/unord/key_value_traits.pass.cpp
+++ b/libcxx/test/libcxx-03/containers/unord/key_value_traits.pass.cpp
@@ -6,9 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
-#include <__hash_table>
+#include <__cxx03/__hash_table>
 #include <unordered_map>
 #include <unordered_set>
 #include <type_traits>
diff --git a/libcxx/test/libcxx-03/containers/unord/next_prime.pass.cpp b/libcxx/test/libcxx-03/containers/unord/next_prime.pass.cpp
index 44b0eb96e2b9b..3ca8d27d17a09 100644
--- a/libcxx/test/libcxx-03/containers/unord/next_prime.pass.cpp
+++ b/libcxx/test/libcxx-03/containers/unord/next_prime.pass.cpp
@@ -16,9 +16,7 @@
 
 // If n == 0, return 0, else return the lowest prime greater than or equal to n
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
-#include <__hash_table>
+#include <__cxx03/__hash_table>
 #include <cassert>
 #include <cstddef>
 
diff --git a/libcxx/test/libcxx-03/iterators/aliasing_iterator.pass.cpp b/libcxx/test/libcxx-03/iterators/aliasing_iterator.pass.cpp
index 33774578e2337..d3bd7cc8618ef 100644
--- a/libcxx/test/libcxx-03/iterators/aliasing_iterator.pass.cpp
+++ b/libcxx/test/libcxx-03/iterators/aliasing_iterator.pass.cpp
@@ -8,9 +8,7 @@
 
 // ADDITIONAL_COMPILE_FLAGS(clang): -Wprivate-header
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
-#include <__iterator/aliasing_iterator.h>
+#include <__cxx03/__iterator/aliasing_iterator.h>
 #include <cassert>
 
 struct NonTrivial {
diff --git a/libcxx/test/libcxx-03/iterators/bounded_iter/arithmetic.pass.cpp b/libcxx/test/libcxx-03/iterators/bounded_iter/arithmetic.pass.cpp
index 3fc735b441676..b4b6e7fa1940c 100644
--- a/libcxx/test/libcxx-03/iterators/bounded_iter/arithmetic.pass.cpp
+++ b/libcxx/test/libcxx-03/iterators/bounded_iter/arithmetic.pass.cpp
@@ -11,9 +11,7 @@
 //
 // Arithmetic operators
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
-#include <__iterator/bounded_iter.h>
+#include <__cxx03/__iterator/bounded_iter.h>
 #include <cstddef>
 
 #include "test_iterators.h"
diff --git a/libcxx/test/libcxx-03/iterators/bounded_iter/pointer_traits.pass.cpp b/libcxx/test/libcxx-03/iterators/bounded_iter/pointer_traits.pass.cpp
index 22ad8c6706d6f..671e716d21e26 100644
--- a/libcxx/test/libcxx-03/iterators/bounded_iter/pointer_traits.pass.cpp
+++ b/libcxx/test/libcxx-03/iterators/bounded_iter/pointer_traits.pass.cpp
@@ -11,9 +11,7 @@
 //
 // std::pointer_traits specialization
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
-#include <__iterator/bounded_iter.h>
+#include <__cxx03/__iterator/bounded_iter.h>
 #include <cassert>
 #include <cstddef>
 #include <memory>
diff --git a/libcxx/test/libcxx-03/iterators/bounded_iter/types.compile.pass.cpp b/libcxx/test/libcxx-03/iterators/bounded_iter/types.compile.pass.cpp
index d205c5b03ee3f..0d27dff0873b4 100644
--- a/libcxx/test/libcxx-03/iterators/bounded_iter/types.compile.pass.cpp
+++ b/libcxx/test/libcxx-03/iterators/bounded_iter/types.compile.pass.cpp
@@ -11,9 +11,7 @@
 //
 // Nested types
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
-#include <__iterator/bounded_iter.h>
+#include <__cxx03/__iterator/bounded_iter.h>
 #include <cstddef>
 #include <iterator>
 #include <type_traits>
diff --git a/libcxx/test/libcxx-03/memory/allocation_guard.pass.cpp b/libcxx/test/libcxx-03/memory/allocation_guard.pass.cpp
index 20c05b381ef0e..5e71decdcabbd 100644
--- a/libcxx/test/libcxx-03/memory/allocation_guard.pass.cpp
+++ b/libcxx/test/libcxx-03/memory/allocation_guard.pass.cpp
@@ -12,12 +12,10 @@
 // To allow checking that self-move works correctly.
 // ADDITIONAL_COMPILE_FLAGS: -Wno-self-move
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
 // template<class _Alloc>
 // struct __allocation_guard;
 
-#include <__memory/allocation_guard.h>
+#include <__cxx03/__memory/allocation_guard.h>
 #include <cassert>
 #include <type_traits>
 #include <utility>
diff --git a/libcxx/test/libcxx-03/memory/swap_allocator.pass.cpp b/libcxx/test/libcxx-03/memory/swap_allocator.pass.cpp
index f70f8134d1dda..38dde7a1bf636 100644
--- a/libcxx/test/libcxx-03/memory/swap_allocator.pass.cpp
+++ b/libcxx/test/libcxx-03/memory/swap_allocator.pass.cpp
@@ -7,14 +7,12 @@
 //===----------------------------------------------------------------------===//
 //
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
 // <memory>
 
 // template <typename _Alloc>
 // void __swap_allocator(_Alloc& __a1, _Alloc& __a2);
 
-#include <__memory/swap_allocator.h>
+#include <__cxx03/__memory/swap_allocator.h>
 #include <cassert>
 #include <memory>
 #include <utility>
diff --git a/libcxx/test/libcxx-03/numerics/clamp_to_integral.pass.cpp b/libcxx/test/libcxx-03/numerics/clamp_to_integral.pass.cpp
index 68d55afa1f280..d8ac80d4d2fc4 100644
--- a/libcxx/test/libcxx-03/numerics/clamp_to_integral.pass.cpp
+++ b/libcxx/test/libcxx-03/numerics/clamp_to_integral.pass.cpp
@@ -12,9 +12,7 @@
 // closest representable value for the specified integer type, or
 // numeric_limits<IntT>::max()/min() if the value isn't representable.
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
-#include <__random/clamp_to_integral.h>
+#include <__cxx03/__random/clamp_to_integral.h>
 #include <cassert>
 #include <cmath>
 #include <limits>
diff --git a/libcxx/test/libcxx-03/strings/c.strings/constexpr_memmove.pass.cpp b/libcxx/test/libcxx-03/strings/c.strings/constexpr_memmove.pass.cpp
index 2009cbe28a91f..d2ca5a2658524 100644
--- a/libcxx/test/libcxx-03/strings/c.strings/constexpr_memmove.pass.cpp
+++ b/libcxx/test/libcxx-03/strings/c.strings/constexpr_memmove.pass.cpp
@@ -19,9 +19,7 @@
 // and is_trivially_XXX_assignable), so we use some funky types to test these
 // corner cases.
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
-#include <__string/constexpr_c_functions.h>
+#include <__cxx03/__string/constexpr_c_functions.h>
 #include <cassert>
 #include <cstdint>
 #include <type_traits>
diff --git a/libcxx/test/libcxx-03/type_traits/is_trivially_comparable.compile.pass.cpp b/libcxx/test/libcxx-03/type_traits/is_trivially_comparable.compile.pass.cpp
index e9b53080fcd6d..860ed63500e20 100644
--- a/libcxx/test/libcxx-03/type_traits/is_trivially_comparable.compile.pass.cpp
+++ b/libcxx/test/libcxx-03/type_traits/is_trivially_comparable.compile.pass.cpp
@@ -6,11 +6,9 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
-#include <__type_traits/conditional.h>
-#include <__type_traits/is_equality_comparable.h>
-#include <__type_traits/is_signed.h>
+#include <__cxx03/__type_traits/conditional.h>
+#include <__cxx03/__type_traits/is_equality_comparable.h>
+#include <__cxx03/__type_traits/is_signed.h>
 #include <cstdint>
 
 enum Enum : int {};
diff --git a/libcxx/test/libcxx-03/type_traits/is_trivially_relocatable.compile.pass.cpp b/libcxx/test/libcxx-03/type_traits/is_trivially_relocatable.compile.pass.cpp
index 8066925f2900a..09049f38497aa 100644
--- a/libcxx/test/libcxx-03/type_traits/is_trivially_relocatable.compile.pass.cpp
+++ b/libcxx/test/libcxx-03/type_traits/is_trivially_relocatable.compile.pass.cpp
@@ -6,9 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
-#include <__type_traits/is_trivially_relocatable.h>
+#include <__cxx03/__type_traits/is_trivially_relocatable.h>
 #include <array>
 #include <deque>
 #include <exception>
diff --git a/libcxx/test/libcxx-03/utilities/exception_guard.odr.sh.cpp b/libcxx/test/libcxx-03/utilities/exception_guard.odr.sh.cpp
index fb51a4bf4ed27..92ec3e97cabe4 100644
--- a/libcxx/test/libcxx-03/utilities/exception_guard.odr.sh.cpp
+++ b/libcxx/test/libcxx-03/utilities/exception_guard.odr.sh.cpp
@@ -9,8 +9,6 @@
 // This test relies on `typeid` and thus requires `-frtti`.
 // UNSUPPORTED: no-rtti
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
 // Make sure that we don't get ODR violations with __exception_guard when
 // linking together TUs compiled with different values of -f[no-]exceptions.
 
@@ -19,7 +17,7 @@
 // RUN: %{cxx} %{flags} %{link_flags} -o %t.exe %t.except.o %t.noexcept.o
 // RUN: %{run}
 
-#include <__utility/exception_guard.h>
+#include <__cxx03/__utility/exception_guard.h>
 #include <cassert>
 #include <cstring>
 #include <typeinfo>
diff --git a/libcxx/test/libcxx-03/utilities/is_pointer_in_range.pass.cpp b/libcxx/test/libcxx-03/utilities/is_pointer_in_range.pass.cpp
index b0a27c79287d4..6c60147adfdf4 100644
--- a/libcxx/test/libcxx-03/utilities/is_pointer_in_range.pass.cpp
+++ b/libcxx/test/libcxx-03/utilities/is_pointer_in_range.pass.cpp
@@ -6,9 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
-#include <__utility/is_pointer_in_range.h>
+#include <__cxx03/__utility/is_pointer_in_range.h>
 #include <cassert>
 
 #include "test_macros.h"
diff --git a/libcxx/test/libcxx-03/utilities/is_valid_range.pass.cpp b/libcxx/test/libcxx-03/utilities/is_valid_range.pass.cpp
index cb800aee5674b..9ad1e89f98187 100644
--- a/libcxx/test/libcxx-03/utilities/is_valid_range.pass.cpp
+++ b/libcxx/test/libcxx-03/utilities/is_valid_range.pass.cpp
@@ -6,9 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
-#include <__utility/is_valid_range.h>
+#include <__cxx03/__utility/is_valid_range.h>
 #include <cassert>
 
 #include "test_macros.h"
diff --git a/libcxx/test/libcxx-03/utilities/meta/meta_base.pass.cpp b/libcxx/test/libcxx-03/utilities/meta/meta_base.pass.cpp
index 66c25b1d75638..f6bddedc96ac0 100644
--- a/libcxx/test/libcxx-03/utilities/meta/meta_base.pass.cpp
+++ b/libcxx/test/libcxx-03/utilities/meta/meta_base.pass.cpp
@@ -7,15 +7,13 @@
 //===----------------------------------------------------------------------===//
 //
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
 #include "test_macros.h"
 
 TEST_CLANG_DIAGNOSTIC_IGNORED("-Wprivate-header")
-#include <__type_traits/conjunction.h>
-#include <__type_traits/disjunction.h>
-#include <__type_traits/is_valid_expansion.h>
-#include <__type_traits/negation.h>
+#include <__cxx03/__type_traits/conjunction.h>
+#include <__cxx03/__type_traits/disjunction.h>
+#include <__cxx03/__type_traits/is_valid_expansion.h>
+#include <__cxx03/__type_traits/negation.h>
 #include <cassert>
 #include <type_traits>
 #include <utility>
diff --git a/libcxx/test/libcxx-03/utilities/no_destroy.pass.cpp b/libcxx/test/libcxx-03/utilities/no_destroy.pass.cpp
index 8693bb17089dc..561654d7f31fb 100644
--- a/libcxx/test/libcxx-03/utilities/no_destroy.pass.cpp
+++ b/libcxx/test/libcxx-03/utilities/no_destroy.pass.cpp
@@ -6,9 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
-#include <__utility/no_destroy.h>
+#include <__cxx03/__utility/no_destroy.h>
 #include <cassert>
 
 #include "test_macros.h"
diff --git a/libcxx/test/libcxx-03/utilities/utility/private_constructor_tag.compile.pass.cpp b/libcxx/test/libcxx-03/utilities/utility/private_constructor_tag.compile.pass.cpp
index 1644819a02f7f..a186098eeb295 100644
--- a/libcxx/test/libcxx-03/utilities/utility/private_constructor_tag.compile.pass.cpp
+++ b/libcxx/test/libcxx-03/utilities/utility/private_constructor_tag.compile.pass.cpp
@@ -6,8 +6,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
 // struct __private_constructor_tag{};
 
 // The private constructor tag is intended to be a trivial type that can easily
@@ -15,7 +13,7 @@
 //
 // Tests whether the type is trivial.
 
-#include <__utility/private_constructor_tag.h>
+#include <__cxx03/__utility/private_constructor_tag.h>
 #include <type_traits>
 
 static_assert(std::is_trivially_copyable<std::__private_constructor_tag>::value, "");
diff --git a/libcxx/test/selftest/test_macros.pass.cpp b/libcxx/test/selftest/test_macros.pass.cpp
index 9bcf7cf9a31f5..66cb7c0b9b57d 100644
--- a/libcxx/test/selftest/test_macros.pass.cpp
+++ b/libcxx/test/selftest/test_macros.pass.cpp
@@ -8,9 +8,6 @@
 //
 // Test the "test_macros.h" header.
 
-// XFAIL: FROZEN-CXX03-HEADERS-FIXME
-
-#include <__config>
 #include "test_macros.h"
 
 #ifndef TEST_STD_VER