Index: libcxx/include/__mdspan/extents.h
===================================================================
--- libcxx/include/__mdspan/extents.h
+++ libcxx/include/__mdspan/extents.h
@@ -171,11 +171,14 @@
       _TStatic __static_val = _StaticValues::__get(__i);
       if (__static_val == _DynTag) {
         __dyn_vals_[_DynamicIdxMap::__get(__i)] = __values[__i];
-      }
-      // Precondition check
-      else
-        _LIBCPP_ASSERT_UNCATEGORIZED(__values[__i] == static_cast<_TDynamic>(__static_val),
-                                     "extents construction: mismatch of provided arguments with static extents.");
+      } else
+        // Not catching this could lead to out of bounds errors later
+        // e.g. using my_mdspan_t = mdspan<int, extents<int, 10>>; my_mdspan_t = m(new int[5], 5);
+        // Right-hand-side construction looks ok with allocation and size matching,
+        // but since (potentially elsewhere defined) my_mdspan_t has static size m now thinks its range is 10 not 5
+        _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
+            __values[__i] == static_cast<_TDynamic>(__static_val),
+            "extents construction: mismatch of provided arguments with static extents.");
     }
   }
 
@@ -187,11 +190,14 @@
       _TStatic __static_val = _StaticValues::__get(__i);
       if (__static_val == _DynTag) {
         __dyn_vals_[_DynamicIdxMap::__get(__i)] = static_cast<_TDynamic>(__vals[__i]);
-      }
-      // Precondition check
-      else
-        _LIBCPP_ASSERT_UNCATEGORIZED(static_cast<_TDynamic>(__vals[__i]) == static_cast<_TDynamic>(__static_val),
-                                     "extents construction: mismatch of provided arguments with static extents.");
+      } else
+        // Not catching this could lead to out of bounds errors later
+        // e.g. using my_mdspan_t = mdspan<int, extents<int, 10>>; my_mdspan_t = m(new int[N], span<int,1>(&N));
+        // Right-hand-side construction looks ok with allocation and size matching,
+        // but since (potentially elsewhere defined) my_mdspan_t has static size m now thinks its range is 10 not N
+        _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
+            static_cast<_TDynamic>(__vals[__i]) == static_cast<_TDynamic>(__static_val),
+            "extents construction: mismatch of provided arguments with static extents.");
     }
   }
 
@@ -310,8 +316,10 @@
              (sizeof...(_OtherIndexTypes) == __rank_ || sizeof...(_OtherIndexTypes) == __rank_dynamic_))
   _LIBCPP_HIDE_FROM_ABI constexpr explicit extents(_OtherIndexTypes... __dynvals) noexcept
       : __vals_(static_cast<index_type>(__dynvals)...) {
-    _LIBCPP_ASSERT_UNCATEGORIZED(__mdspan_detail::__are_representable_as<index_type>(__dynvals...),
-                                 "extents ctor: arguments must be representable as index_type and nonnegative");
+    // Not catching this could lead to out of bounds errors later
+    // e.g. mdspan m(ptr, dextents<char, 1>(200u)); leads to an extent of -56 on m
+    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__mdspan_detail::__are_representable_as<index_type>(__dynvals...),
+                                        "extents ctor: arguments must be representable as index_type and nonnegative");
   }
 
   template <class _OtherIndexType, size_t _Size>
@@ -321,8 +329,10 @@
   explicit(_Size != __rank_dynamic_)
       _LIBCPP_HIDE_FROM_ABI constexpr extents(const array<_OtherIndexType, _Size>& __exts) noexcept
       : __vals_(span(__exts)) {
-    _LIBCPP_ASSERT_UNCATEGORIZED(__mdspan_detail::__are_representable_as<index_type>(span(__exts)),
-                                 "extents ctor: arguments must be representable as index_type and nonnegative");
+    // Not catching this could lead to out of bounds errors later
+    // e.g. mdspan m(ptr, dextents<char, 1>(array<unsigned,1>(200))); leads to an extent of -56 on m
+    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__mdspan_detail::__are_representable_as<index_type>(span(__exts)),
+                                        "extents ctor: arguments must be representable as index_type and nonnegative");
   }
 
   template <class _OtherIndexType, size_t _Size>
@@ -332,8 +342,11 @@
   explicit(_Size != __rank_dynamic_)
       _LIBCPP_HIDE_FROM_ABI constexpr extents(const span<_OtherIndexType, _Size>& __exts) noexcept
       : __vals_(__exts) {
-    _LIBCPP_ASSERT_UNCATEGORIZED(__mdspan_detail::__are_representable_as<index_type>(__exts),
-                                 "extents ctor: arguments must be representable as index_type and nonnegative");
+    // Not catching this could lead to out of bounds errors later
+    // e.g. array a{200u}; mdspan<int, dextents<char,1>> m(ptr, extents(span<unsigned,1>(a))); leads to an extent of -56
+    // on m
+    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__mdspan_detail::__are_representable_as<index_type>(__exts),
+                                        "extents ctor: arguments must be representable as index_type and nonnegative");
   }
 
 private:
@@ -382,10 +395,16 @@
       for (size_t __r = 0; __r < rank(); __r++) {
         if constexpr (static_cast<make_unsigned_t<index_type>>(numeric_limits<index_type>::max()) <
                       static_cast<make_unsigned_t<_OtherIndexType>>(numeric_limits<_OtherIndexType>::max())) {
-          _LIBCPP_ASSERT_UNCATEGORIZED(__mdspan_detail::__is_representable_as<index_type>(__other.extent(__r)),
-                                       "extents ctor: arguments must be representable as index_type and nonnegative");
+          // Not catching this could lead to out of bounds errors later
+          // e.g. dextents<char,1>> e(dextents<unsigned,1>(200)) leads to an extent of -56 on e
+          _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
+              __mdspan_detail::__is_representable_as<index_type>(__other.extent(__r)),
+              "extents ctor: arguments must be representable as index_type and nonnegative");
         }
-        _LIBCPP_ASSERT_UNCATEGORIZED(
+        // Not catching this could lead to out of bounds errors later
+        // e.g. mdspan<int, extents<int, 10>> m = mdspan<int, dextents<int, 1>>(new int[5], 5);
+        // Right-hand-side construction was ok, but m now thinks its range is 10 not 5
+        _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
             (_Values::__static_value(__r) == dynamic_extent) ||
                 (static_cast<index_type>(__other.extent(__r)) == static_cast<index_type>(_Values::__static_value(__r))),
             "extents construction: mismatch of provided arguments with static extents.");
Index: libcxx/include/__mdspan/layout_left.h
===================================================================
--- libcxx/include/__mdspan/layout_left.h
+++ libcxx/include/__mdspan/layout_left.h
@@ -75,7 +75,9 @@
   _LIBCPP_HIDE_FROM_ABI constexpr mapping() noexcept               = default;
   _LIBCPP_HIDE_FROM_ABI constexpr mapping(const mapping&) noexcept = default;
   _LIBCPP_HIDE_FROM_ABI constexpr mapping(const extents_type& __ext) noexcept : __extents_(__ext) {
-    _LIBCPP_ASSERT_UNCATEGORIZED(
+    // not catching this could lead to out-of-bounds access later when used inside mdspan
+    // mapping<dextents<char, 2>> map(dextents<char, 2>(40,40)); map(10, 3) == -126
+    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
         __required_span_size_is_representable(__ext),
         "layout_left::mapping extents ctor: product of extents must be representable as index_type.");
   }
@@ -85,7 +87,9 @@
   _LIBCPP_HIDE_FROM_ABI constexpr explicit(!is_convertible_v<_OtherExtents, extents_type>)
       mapping(const mapping<_OtherExtents>& __other) noexcept
       : __extents_(__other.extents()) {
-    _LIBCPP_ASSERT_UNCATEGORIZED(
+    // not catching this could lead to out-of-bounds access later when used inside mdspan
+    // mapping<dextents<char, 2>> map(mapping<dextents<int, 2>>(dextents<int, 2>(40,40))); map(10, 3) == -126
+    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
         __mdspan_detail::__is_representable_as<index_type>(__other.required_span_size()),
         "layout_left::mapping converting ctor: other.required_span_size() must be representable as index_type.");
   }
@@ -95,7 +99,13 @@
   _LIBCPP_HIDE_FROM_ABI constexpr explicit(!is_convertible_v<_OtherExtents, extents_type>)
       mapping(const layout_right::mapping<_OtherExtents>& __other) noexcept
       : __extents_(__other.extents()) {
-    _LIBCPP_ASSERT_UNCATEGORIZED(
+    // not catching this could lead to out-of-bounds access later when used inside mdspan
+    // Note: since this is constraint to rank 1, extents itself would catch the invalid conversion first
+    //       and thus this assertion should never be triggered, but keeping it here for consistency
+    // layout_left::mapping<dextents<char, 1>> map(
+    //           layout_right::mapping<dextents<unsigned, 1>>(dextents<unsigned, 1>(200))); map.extents().extent(0) ==
+    //           -56
+    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
         __mdspan_detail::__is_representable_as<index_type>(__other.required_span_size()),
         "layout_left::mapping converting ctor: other.required_span_size() must be representable as index_type.");
   }
@@ -123,8 +133,12 @@
     requires((sizeof...(_Indices) == extents_type::rank()) && (is_convertible_v<_Indices, index_type> && ...) &&
              (is_nothrow_constructible_v<index_type, _Indices> && ...))
   _LIBCPP_HIDE_FROM_ABI constexpr index_type operator()(_Indices... __idx) const noexcept {
-    _LIBCPP_ASSERT_UNCATEGORIZED(__mdspan_detail::__is_multidimensional_index_in(__extents_, __idx...),
-                                 "layout_left::mapping: out of bounds indexing");
+    // Mappings are generally meant to be used for accessing allocations and are meant to guarantee to never
+    // return a value exceeding required_span_size(), which is used to know how large an allocation one needs
+    // Thus, this is a canonical point in multi-dimensional data structures to make invalid element access checks
+    // However, mdspan does check this on its own, so for now we avoid double checking in hardened mode
+    _LIBCPP_ASSERT(__mdspan_detail::__is_multidimensional_index_in(__extents_, __idx...),
+                   "layout_left::mapping: out of bounds indexing");
     array<index_type, extents_type::rank()> __idx_a{static_cast<index_type>(__idx)...};
     return [&]<size_t... _Pos>(index_sequence<_Pos...>) {
       index_type __res = 0;
@@ -145,7 +159,10 @@
   _LIBCPP_HIDE_FROM_ABI constexpr index_type stride(rank_type __r) const noexcept
     requires(extents_type::rank() > 0)
   {
-    _LIBCPP_ASSERT_UNCATEGORIZED(__r < extents_type::rank(), "layout_left::mapping::stride(): invalid rank index");
+    // While it would be caught by extents itself too, using a too large __r
+    // is functionally an out of bounds access on the stored information needed to compute strides
+    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
+        __r < extents_type::rank(), "layout_left::mapping::stride(): invalid rank index");
     index_type __s = 1;
     for (rank_type __i = extents_type::rank() - 1; __i > __r; __i--)
       __s *= __extents_.extent(__i);
Index: libcxx/include/__mdspan/layout_right.h
===================================================================
--- libcxx/include/__mdspan/layout_right.h
+++ libcxx/include/__mdspan/layout_right.h
@@ -74,7 +74,9 @@
   _LIBCPP_HIDE_FROM_ABI constexpr mapping() noexcept               = default;
   _LIBCPP_HIDE_FROM_ABI constexpr mapping(const mapping&) noexcept = default;
   _LIBCPP_HIDE_FROM_ABI constexpr mapping(const extents_type& __ext) noexcept : __extents_(__ext) {
-    _LIBCPP_ASSERT_UNCATEGORIZED(
+    // not catching this could lead to out-of-bounds access later when used inside mdspan
+    // mapping<dextents<char, 2>> map(dextents<char, 2>(40,40)); map(3, 10) == -126
+    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
         __required_span_size_is_representable(__ext),
         "layout_right::mapping extents ctor: product of extents must be representable as index_type.");
   }
@@ -84,7 +86,9 @@
   _LIBCPP_HIDE_FROM_ABI constexpr explicit(!is_convertible_v<_OtherExtents, extents_type>)
       mapping(const mapping<_OtherExtents>& __other) noexcept
       : __extents_(__other.extents()) {
-    _LIBCPP_ASSERT_UNCATEGORIZED(
+    // not catching this could lead to out-of-bounds access later when used inside mdspan
+    // mapping<dextents<char, 2>> map(mapping<dextents<int, 2>>(dextents<int, 2>(40,40))); map(3, 10) == -126
+    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
         __mdspan_detail::__is_representable_as<index_type>(__other.required_span_size()),
         "layout_right::mapping converting ctor: other.required_span_size() must be representable as index_type.");
   }
@@ -94,7 +98,13 @@
   _LIBCPP_HIDE_FROM_ABI constexpr explicit(!is_convertible_v<_OtherExtents, extents_type>)
       mapping(const layout_left::mapping<_OtherExtents>& __other) noexcept
       : __extents_(__other.extents()) {
-    _LIBCPP_ASSERT_UNCATEGORIZED(
+    // not catching this could lead to out-of-bounds access later when used inside mdspan
+    // Note: since this is constraint to rank 1, extents itself would catch the invalid conversion first
+    //       and thus this assertion should never be triggered, but keeping it here for consistency
+    // layout_right::mapping<dextents<char, 1>> map(
+    //           layout_left::mapping<dextents<unsigned, 1>>(dextents<unsigned, 1>(200))); map.extents().extent(0) ==
+    //           -56
+    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
         __mdspan_detail::__is_representable_as<index_type>(__other.required_span_size()),
         "layout_right::mapping converting ctor: other.required_span_size() must be representable as index_type.");
   }
@@ -122,8 +132,12 @@
     requires((sizeof...(_Indices) == extents_type::rank()) && (is_convertible_v<_Indices, index_type> && ...) &&
              (is_nothrow_constructible_v<index_type, _Indices> && ...))
   _LIBCPP_HIDE_FROM_ABI constexpr index_type operator()(_Indices... __idx) const noexcept {
-    _LIBCPP_ASSERT_UNCATEGORIZED(__mdspan_detail::__is_multidimensional_index_in(__extents_, __idx...),
-                                 "layout_right::mapping: out of bounds indexing");
+    // Mappings are generally meant to be used for accessing allocations and are meant to guarantee to never
+    // return a value exceeding required_span_size(), which is used to know how large an allocation one needs
+    // Thus, this is a canonical point in multi-dimensional data structures to make invalid element access checks
+    // However, mdspan does check this on its own, so for now we avoid double checking in hardened mode
+    _LIBCPP_ASSERT(__mdspan_detail::__is_multidimensional_index_in(__extents_, __idx...),
+                   "layout_right::mapping: out of bounds indexing");
     return [&]<size_t... _Pos>(index_sequence<_Pos...>) {
       index_type __res = 0;
       ((__res = static_cast<index_type>(__idx) + __extents_.extent(_Pos) * __res), ...);
@@ -142,7 +156,10 @@
   _LIBCPP_HIDE_FROM_ABI constexpr index_type stride(rank_type __r) const noexcept
     requires(extents_type::rank() > 0)
   {
-    _LIBCPP_ASSERT_UNCATEGORIZED(__r < extents_type::rank(), "layout_right::mapping::stride(): invalid rank index");
+    // While it would be caught by extents itself too, using a too large __r
+    // is functionally an out of bounds access on the stored information needed to compute strides
+    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
+        __r < extents_type::rank(), "layout_right::mapping::stride(): invalid rank index");
     index_type __s = 1;
     for (rank_type __i = extents_type::rank() - 1; __i > __r; __i--)
       __s *= __extents_.extent(__i);
Index: libcxx/include/__mdspan/mdspan.h
===================================================================
--- libcxx/include/__mdspan/mdspan.h
+++ libcxx/include/__mdspan/mdspan.h
@@ -166,7 +166,10 @@
     // always construct its extents() only from the dynamic extents, instead of from the other extents.
     if constexpr (rank() > 0) {
       for (size_t __r = 0; __r < rank(); __r++) {
-        _LIBCPP_ASSERT_UNCATEGORIZED(
+        // Not catching this could lead to out of bounds errors later
+        // e.g. mdspan<int, dextents<char,1>, non_checking_layout> m =
+        //        mdspan<int, dextents<unsigned, 1>, non_checking_layout>(ptr, 200); leads to an extent of -56 on m
+        _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
             (static_extent(__r) == dynamic_extent) ||
                 (static_cast<index_type>(__other.extent(__r)) == static_cast<index_type>(static_extent(__r))),
             "mdspan: conversion mismatch of source dynamic extents with static extents");
@@ -185,8 +188,10 @@
              (is_nothrow_constructible_v<index_type, _OtherIndexTypes> && ...) &&
              (sizeof...(_OtherIndexTypes) == rank()))
   _LIBCPP_HIDE_FROM_ABI constexpr reference operator[](_OtherIndexTypes... __indices) const {
-    _LIBCPP_ASSERT_UNCATEGORIZED(__mdspan_detail::__is_multidimensional_index_in(extents(), __indices...),
-                                 "mdspan: operator[] out of bounds access");
+    // Note the standard layouts would also check this, but user provided ones may not, so we
+    // check the precondition here
+    _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__mdspan_detail::__is_multidimensional_index_in(extents(), __indices...),
+                                        "mdspan: operator[] out of bounds access");
     return __acc_.access(__ptr_, __map_(static_cast<index_type>(std::move(__indices))...));
   }
 
@@ -209,6 +214,8 @@
   }
 
   _LIBCPP_HIDE_FROM_ABI constexpr size_type size() const noexcept {
+    // Could leave this as only checked in debug mode: semantically size() is never
+    // guaranteed to be related to any accessible range
     _LIBCPP_ASSERT_UNCATEGORIZED(
         false == ([&]<size_t... _Idxs>(index_sequence<_Idxs...>) {
           size_type __prod = 1;
@@ -260,13 +267,13 @@
 explicit mdspan(_ElementType*, _OtherIndexTypes...)
     -> mdspan<_ElementType, dextents<size_t, sizeof...(_OtherIndexTypes)>>;
 
-template <class Pointer>
-  requires(is_pointer_v<remove_reference_t<Pointer>>)
-mdspan(Pointer&&) -> mdspan<remove_pointer_t<remove_reference_t<Pointer>>, extents<size_t>>;
+template <class _Pointer>
+  requires(is_pointer_v<remove_reference_t<_Pointer>>)
+mdspan(_Pointer&&) -> mdspan<remove_pointer_t<remove_reference_t<_Pointer>>, extents<size_t>>;
 
-template <class CArray>
-  requires(is_array_v<CArray> && (rank_v<CArray> == 1))
-mdspan(CArray&) -> mdspan<remove_all_extents_t<CArray>, extents<size_t, extent_v<CArray, 0>>>;
+template <class _CArray>
+  requires(is_array_v<_CArray> && (rank_v<_CArray> == 1))
+mdspan(_CArray&) -> mdspan<remove_all_extents_t<_CArray>, extents<size_t, extent_v<_CArray, 0>>>;
 
 template <class _ElementType, class _OtherIndexType, size_t _Size>
 mdspan(_ElementType*, const array<_OtherIndexType, _Size>&) -> mdspan<_ElementType, dextents<size_t, _Size>>;
@@ -281,16 +288,16 @@
 mdspan(_ElementType*, const extents<_OtherIndexType, _ExtentsPack...>&)
     -> mdspan<_ElementType, extents<_OtherIndexType, _ExtentsPack...>>;
 
-template <class _ElementType, class MappingType>
-mdspan(_ElementType*, const MappingType&)
-    -> mdspan<_ElementType, typename MappingType::extents_type, typename MappingType::layout_type>;
+template <class _ElementType, class _MappingType>
+mdspan(_ElementType*, const _MappingType&)
+    -> mdspan<_ElementType, typename _MappingType::extents_type, typename _MappingType::layout_type>;
 
-template <class MappingType, class AccessorType>
-mdspan(const typename AccessorType::data_handle_type, const MappingType&, const AccessorType&)
-    -> mdspan<typename AccessorType::element_type,
-              typename MappingType::extents_type,
-              typename MappingType::layout_type,
-              AccessorType>;
+template <class _MappingType, class _AccessorType>
+mdspan(const typename _AccessorType::data_handle_type, const _MappingType&, const _AccessorType&)
+    -> mdspan<typename _AccessorType::element_type,
+              typename _MappingType::extents_type,
+              typename _MappingType::layout_type,
+              _AccessorType>;
 
 #endif // _LIBCPP_STD_VER >= 23
 
Index: libcxx/test/libcxx/containers/views/mdspan/extents/assert.conversion.pass.cpp
===================================================================
--- libcxx/test/libcxx/containers/views/mdspan/extents/assert.conversion.pass.cpp
+++ libcxx/test/libcxx/containers/views/mdspan/extents/assert.conversion.pass.cpp
@@ -6,7 +6,7 @@
 //===----------------------------------------------------------------------===//
 // REQUIRES: has-unix-headers
 // UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
-// UNSUPPORTED: !libcpp-has-debug-mode
+// UNSUPPORTED: !libcpp-has-hardened-mode && !libcpp-has-debug-mode
 // XFAIL: availability-verbose_abort-missing
 
 // <mdspan>
Index: libcxx/test/libcxx/containers/views/mdspan/extents/assert.ctor_from_array.pass.cpp
===================================================================
--- libcxx/test/libcxx/containers/views/mdspan/extents/assert.ctor_from_array.pass.cpp
+++ libcxx/test/libcxx/containers/views/mdspan/extents/assert.ctor_from_array.pass.cpp
@@ -6,7 +6,7 @@
 //===----------------------------------------------------------------------===//
 // REQUIRES: has-unix-headers
 // UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
-// UNSUPPORTED: !libcpp-has-debug-mode
+// UNSUPPORTED: !libcpp-has-hardened-mode && !libcpp-has-debug-mode
 // XFAIL: availability-verbose_abort-missing
 
 // <mdspan>
Index: libcxx/test/libcxx/containers/views/mdspan/extents/assert.ctor_from_integral.pass.cpp
===================================================================
--- libcxx/test/libcxx/containers/views/mdspan/extents/assert.ctor_from_integral.pass.cpp
+++ libcxx/test/libcxx/containers/views/mdspan/extents/assert.ctor_from_integral.pass.cpp
@@ -6,7 +6,7 @@
 //===----------------------------------------------------------------------===//
 // REQUIRES: has-unix-headers
 // UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
-// UNSUPPORTED: !libcpp-has-debug-mode
+// UNSUPPORTED: !libcpp-has-hardened-mode && !libcpp-has-debug-mode
 // XFAIL: availability-verbose_abort-missing
 
 // <mdspan>
Index: libcxx/test/libcxx/containers/views/mdspan/extents/assert.ctor_from_span.pass.cpp
===================================================================
--- libcxx/test/libcxx/containers/views/mdspan/extents/assert.ctor_from_span.pass.cpp
+++ libcxx/test/libcxx/containers/views/mdspan/extents/assert.ctor_from_span.pass.cpp
@@ -6,7 +6,7 @@
 //===----------------------------------------------------------------------===//
 // REQUIRES: has-unix-headers
 // UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
-// UNSUPPORTED: !libcpp-has-debug-mode
+// UNSUPPORTED: !libcpp-has-hardened-mode && !libcpp-has-debug-mode
 // XFAIL: availability-verbose_abort-missing
 
 // Test construction from span:
Index: libcxx/test/libcxx/containers/views/mdspan/extents/assert.obs.pass.cpp
===================================================================
--- libcxx/test/libcxx/containers/views/mdspan/extents/assert.obs.pass.cpp
+++ libcxx/test/libcxx/containers/views/mdspan/extents/assert.obs.pass.cpp
@@ -6,7 +6,7 @@
 //===----------------------------------------------------------------------===//
 // REQUIRES: has-unix-headers
 // UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
-// UNSUPPORTED: !libcpp-has-debug-mode
+// UNSUPPORTED: !libcpp-has-hardened-mode && !libcpp-has-debug-mode
 // XFAIL: availability-verbose_abort-missing
 
 // <mdspan>
Index: libcxx/test/libcxx/containers/views/mdspan/layout_left/assert.conversion.pass.cpp
===================================================================
--- libcxx/test/libcxx/containers/views/mdspan/layout_left/assert.conversion.pass.cpp
+++ libcxx/test/libcxx/containers/views/mdspan/layout_left/assert.conversion.pass.cpp
@@ -8,7 +8,7 @@
 
 // REQUIRES: has-unix-headers
 // UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
-// UNSUPPORTED: !libcpp-has-debug-mode
+// UNSUPPORTED: !libcpp-has-hardened-mode && !libcpp-has-debug-mode
 // XFAIL: availability-verbose_abort-missing
 
 // <mdspan>
Index: libcxx/test/libcxx/containers/views/mdspan/layout_left/assert.ctor.extents.pass.cpp
===================================================================
--- libcxx/test/libcxx/containers/views/mdspan/layout_left/assert.ctor.extents.pass.cpp
+++ libcxx/test/libcxx/containers/views/mdspan/layout_left/assert.ctor.extents.pass.cpp
@@ -8,7 +8,7 @@
 
 // REQUIRES: has-unix-headers
 // UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
-// UNSUPPORTED: !libcpp-has-debug-mode
+// UNSUPPORTED: !libcpp-has-hardened-mode && !libcpp-has-debug-mode
 // XFAIL: availability-verbose_abort-missing
 
 // <mdspan>
Index: libcxx/test/libcxx/containers/views/mdspan/layout_left/assert.ctor.layout_right.pass.cpp
===================================================================
--- libcxx/test/libcxx/containers/views/mdspan/layout_left/assert.ctor.layout_right.pass.cpp
+++ libcxx/test/libcxx/containers/views/mdspan/layout_left/assert.ctor.layout_right.pass.cpp
@@ -8,7 +8,7 @@
 
 // REQUIRES: has-unix-headers
 // UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
-// UNSUPPORTED: !libcpp-has-debug-mode
+// UNSUPPORTED: !libcpp-has-hardened-mode && !libcpp-has-debug-mode
 // XFAIL: availability-verbose_abort-missing
 
 // <mdspan>
Index: libcxx/test/libcxx/containers/views/mdspan/layout_left/assert.stride.pass.cpp
===================================================================
--- libcxx/test/libcxx/containers/views/mdspan/layout_left/assert.stride.pass.cpp
+++ libcxx/test/libcxx/containers/views/mdspan/layout_left/assert.stride.pass.cpp
@@ -8,7 +8,7 @@
 
 // REQUIRES: has-unix-headers
 // UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
-// UNSUPPORTED: !libcpp-has-debug-mode
+// UNSUPPORTED: !libcpp-has-hardened-mode && !libcpp-has-debug-mode
 // XFAIL: availability-verbose_abort-missing
 
 // <mdspan>
Index: libcxx/test/libcxx/containers/views/mdspan/layout_right/assert.conversion.pass.cpp
===================================================================
--- libcxx/test/libcxx/containers/views/mdspan/layout_right/assert.conversion.pass.cpp
+++ libcxx/test/libcxx/containers/views/mdspan/layout_right/assert.conversion.pass.cpp
@@ -8,7 +8,7 @@
 
 // REQUIRES: has-unix-headers
 // UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
-// UNSUPPORTED: !libcpp-has-debug-mode
+// UNSUPPORTED: !libcpp-has-hardened-mode && !libcpp-has-debug-mode
 // XFAIL: availability-verbose_abort-missing
 
 // <mdspan>
Index: libcxx/test/libcxx/containers/views/mdspan/layout_right/assert.ctor.extents.pass.cpp
===================================================================
--- libcxx/test/libcxx/containers/views/mdspan/layout_right/assert.ctor.extents.pass.cpp
+++ libcxx/test/libcxx/containers/views/mdspan/layout_right/assert.ctor.extents.pass.cpp
@@ -8,7 +8,7 @@
 
 // REQUIRES: has-unix-headers
 // UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
-// UNSUPPORTED: !libcpp-has-debug-mode
+// UNSUPPORTED: !libcpp-has-hardened-mode && !libcpp-has-debug-mode
 // XFAIL: availability-verbose_abort-missing
 
 // <mdspan>
Index: libcxx/test/libcxx/containers/views/mdspan/layout_right/assert.ctor.layout_left.pass.cpp
===================================================================
--- libcxx/test/libcxx/containers/views/mdspan/layout_right/assert.ctor.layout_left.pass.cpp
+++ libcxx/test/libcxx/containers/views/mdspan/layout_right/assert.ctor.layout_left.pass.cpp
@@ -8,7 +8,7 @@
 
 // REQUIRES: has-unix-headers
 // UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
-// UNSUPPORTED: !libcpp-has-debug-mode
+// UNSUPPORTED: !libcpp-has-hardened-mode && !libcpp-has-debug-mode
 // XFAIL: availability-verbose_abort-missing
 
 // <mdspan>
Index: libcxx/test/libcxx/containers/views/mdspan/layout_right/assert.stride.pass.cpp
===================================================================
--- libcxx/test/libcxx/containers/views/mdspan/layout_right/assert.stride.pass.cpp
+++ libcxx/test/libcxx/containers/views/mdspan/layout_right/assert.stride.pass.cpp
@@ -8,7 +8,7 @@
 
 // REQUIRES: has-unix-headers
 // UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
-// UNSUPPORTED: !libcpp-has-debug-mode
+// UNSUPPORTED: !libcpp-has-hardened-mode && !libcpp-has-debug-mode
 // XFAIL: availability-verbose_abort-missing
 
 // <mdspan>
Index: libcxx/test/libcxx/containers/views/mdspan/mdspan/assert.conversion.pass.cpp
===================================================================
--- libcxx/test/libcxx/containers/views/mdspan/mdspan/assert.conversion.pass.cpp
+++ libcxx/test/libcxx/containers/views/mdspan/mdspan/assert.conversion.pass.cpp
@@ -6,7 +6,7 @@
 //===----------------------------------------------------------------------===//
 // REQUIRES: has-unix-headers
 // UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
-// UNSUPPORTED: !libcpp-has-debug-mode
+// UNSUPPORTED: !libcpp-has-hardened-mode && !libcpp-has-debug-mode
 // XFAIL: availability-verbose_abort-missing
 
 // <mdspan>
@@ -42,7 +42,7 @@
 #include <mdspan>
 
 #include "check_assertion.h"
-#include "CustomTestLayouts.h"
+#include "../../../../../std/containers/views/mdspan/mdspan/CustomTestLayouts.h"
 
 // We use a funky mapping in this test that doesn't check the dynamic/static extents mismatch itself
 int main(int, char**) {
Index: libcxx/test/libcxx/containers/views/mdspan/mdspan/assert.index_operator.pass.cpp
===================================================================
--- libcxx/test/libcxx/containers/views/mdspan/mdspan/assert.index_operator.pass.cpp
+++ libcxx/test/libcxx/containers/views/mdspan/mdspan/assert.index_operator.pass.cpp
@@ -8,7 +8,7 @@
 
 // REQUIRES: has-unix-headers
 // UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
-// UNSUPPORTED: !libcpp-has-debug-mode
+// UNSUPPORTED: !libcpp-has-hardened-mode && !libcpp-has-debug-mode
 // XFAIL: availability-verbose_abort-missing
 
 // <mdspan>
Index: libcxx/test/libcxx/containers/views/mdspan/mdspan/assert.size.pass.cpp
===================================================================
--- libcxx/test/libcxx/containers/views/mdspan/mdspan/assert.size.pass.cpp
+++ libcxx/test/libcxx/containers/views/mdspan/mdspan/assert.size.pass.cpp
@@ -22,7 +22,7 @@
 #include <mdspan>
 
 #include "check_assertion.h"
-#include "CustomTestLayouts.h"
+#include "../../../../../std/containers/views/mdspan/mdspan/CustomTestLayouts.h"
 
 // We use a funky mapping in this test where required_span_size is much smaller than the size of the index space
 int main(int, char**) {