diff --git a/cudax/include/cuda/experimental/__algorithm/common.cuh b/cudax/include/cuda/experimental/__algorithm/common.cuh
index eadb5e50dd5..f79a9ebc926 100644
--- a/cudax/include/cuda/experimental/__algorithm/common.cuh
+++ b/cudax/include/cuda/experimental/__algorithm/common.cuh
@@ -31,26 +31,8 @@
 namespace cuda::experimental
 {
 
-#if _CCCL_STD_VER >= 2020 && defined(_CCCL_SPAN_USES_RANGES)
 template <typename _Tp>
-concept __valid_1d_copy_fill_argument = _CUDA_VRANGES::contiguous_range<detail::__as_copy_arg_t<_Tp>>;
-
-#else
-template <typename _Tp, typename = int>
-inline constexpr bool __convertible_to_span = false;
-
-template <typename _Tp>
-inline constexpr bool __convertible_to_span<
-  _Tp,
-  _CUDA_VSTD::enable_if_t<
-    _CUDA_VSTD::is_convertible_v<_Tp, _CUDA_VSTD::span<typename _CUDA_VSTD::decay_t<_Tp>::value_type>>,
-    int>> = true;
-
-template <typename _Tp>
-inline constexpr bool __valid_1d_copy_fill_argument =
-  _CUDA_VRANGES::contiguous_range<detail::__as_copy_arg_t<_Tp>> || __convertible_to_span<_Tp>;
-
-#endif
+_CCCL_CONCEPT __valid_1d_copy_fill_argument = _CUDA_VRANGES::contiguous_range<detail::__as_copy_arg_t<_Tp>>;
 
 template <typename _Tp, typename _Decayed = _CUDA_VSTD::decay_t<_Tp>>
 using __as_mdspan_t =
diff --git a/libcudacxx/include/cuda/std/__iterator/iterator_traits.h b/libcudacxx/include/cuda/std/__iterator/iterator_traits.h
index 020f27071db..c597222abd5 100644
--- a/libcudacxx/include/cuda/std/__iterator/iterator_traits.h
+++ b/libcudacxx/include/cuda/std/__iterator/iterator_traits.h
@@ -37,6 +37,7 @@
 #include <cuda/std/__type_traits/is_primary_template.h>
 #include <cuda/std/__type_traits/remove_cv.h>
 #include <cuda/std/__type_traits/void_t.h>
+#include <cuda/std/__utility/priority_tag.h>
 #include <cuda/std/cstddef>
 
 #if !_CCCL_COMPILER(NVRTC)
@@ -46,6 +47,10 @@
 #    include <iterator> // for ::std::input_iterator_tag
 #  endif // !_CCCL_COMPILER(MSVC)
 
+#  ifdef _GLIBCXX_DEBUG
+#    include <debug/safe_iterator.h>
+#  endif
+
 #  if _CCCL_STD_VER >= 2020
 template <class _Tp, class = void>
 struct __cccl_type_is_defined : _CUDA_VSTD::false_type
@@ -109,7 +114,7 @@ _CCCL_CONCEPT __dereferenceable = _CCCL_FRAGMENT(__dereferenceable_, _Tp);
 
 // [iterator.traits]
 template <class _Tp>
-using iter_reference_t = enable_if_t<__dereferenceable<_Tp>, decltype(*_CUDA_VSTD::declval<_Tp&>())>;
+using iter_reference_t = enable_if_t<__dereferenceable<_Tp>, decltype(*declval<_Tp&>())>;
 
 template <class, class>
 struct _CCCL_TYPE_VISIBILITY_DEFAULT iterator_traits;
@@ -165,38 +170,71 @@ struct __iter_traits_cache
 template <class _Iter>
 using _ITER_TRAITS = typename __iter_traits_cache<_Iter>::type;
 
-struct __iter_concept_concept_test
-{
-  template <class _Iter>
-  using _Apply = typename _ITER_TRAITS<_Iter>::iterator_concept;
-};
-struct __iter_concept_category_test
-{
-  template <class _Iter>
-  using _Apply = typename _ITER_TRAITS<_Iter>::iterator_category;
-};
-struct __iter_concept_random_fallback
-{
-  template <class _Iter>
-  using _Apply = enable_if_t<__is_primary_template<iterator_traits<_Iter>>::value, random_access_iterator_tag>;
-};
+#  if defined(_GLIBCXX_DEBUG)
+_CCCL_TEMPLATE(class _Iter, class _Ty, class _Range)
+_CCCL_REQUIRES(same_as<_Iter, ::__gnu_debug::_Safe_iterator<_Ty*, _Range>>)
+auto __iter_concept_fn(::__gnu_debug::_Safe_iterator<_Ty*, _Range>, __priority_tag<3>) -> contiguous_iterator_tag;
+#  endif
+#  if defined(__GLIBCXX__)
+_CCCL_TEMPLATE(class _Iter, class _Ty, class _Range)
+_CCCL_REQUIRES(same_as<_Iter, ::__gnu_cxx::__normal_iterator<_Ty*, _Range>>)
+auto __iter_concept_fn(::__gnu_cxx::__normal_iterator<_Ty*, _Range>, __priority_tag<3>) -> contiguous_iterator_tag;
+#  endif
+#  if defined(_LIBCPP_VERSION)
+_CCCL_TEMPLATE(class _Iter, class _Ty)
+_CCCL_REQUIRES(same_as<_Iter, ::std::__wrap_iter<_Ty*>>)
+auto __iter_concept_fn(::std::__wrap_iter<_Ty*>, __priority_tag<3>) -> contiguous_iterator_tag;
+#  endif
+#  if defined(_MSVC_STL_VERSION) || defined(_IS_WRS)
+_CCCL_TEMPLATE(class _Iter)
+_CCCL_REQUIRES(same_as<_Iter, class _Iter::_Array_iterator>)
+auto __iter_concept_fn(_Iter, __priority_tag<3>) -> contiguous_iterator_tag;
+_CCCL_TEMPLATE(class _Iter)
+_CCCL_REQUIRES(same_as<_Iter, class _Iter::_Array_const_iterator>)
+auto __iter_concept_fn(_Iter, __priority_tag<3>) -> contiguous_iterator_tag;
+_CCCL_TEMPLATE(class _Iter)
+_CCCL_REQUIRES(same_as<_Iter, class _Iter::_Vector_iterator>)
+auto __iter_concept_fn(_Iter, __priority_tag<3>) -> contiguous_iterator_tag;
+_CCCL_TEMPLATE(class _Iter)
+_CCCL_REQUIRES(same_as<_Iter, class _Iter::_Vector_const_iterator>)
+auto __iter_concept_fn(_Iter, __priority_tag<3>) -> contiguous_iterator_tag;
+_CCCL_TEMPLATE(class _Iter)
+_CCCL_REQUIRES(same_as<_Iter, class _Iter::_String_iterator>)
+auto __iter_concept_fn(_Iter, __priority_tag<3>) -> contiguous_iterator_tag;
+_CCCL_TEMPLATE(class _Iter)
+_CCCL_REQUIRES(same_as<_Iter, class _Iter::_String_const_iterator>)
+auto __iter_concept_fn(_Iter, __priority_tag<3>) -> contiguous_iterator_tag;
+_CCCL_TEMPLATE(class _Iter)
+_CCCL_REQUIRES(same_as<_Iter, class _Iter::_String_view_iterator>)
+auto __iter_concept_fn(_Iter, __priority_tag<3>) -> contiguous_iterator_tag;
+#  endif
+_CCCL_TEMPLATE(class _Iter, class _Ty)
+_CCCL_REQUIRES(same_as<_Iter, _Ty*>)
+auto __iter_concept_fn(_Ty*, __priority_tag<3>) -> contiguous_iterator_tag;
+template <class _Iter>
+auto __iter_concept_fn(_Iter, __priority_tag<2>) -> class _ITER_TRAITS<_Iter>::iterator_concept;
+template <class _Iter>
+auto __iter_concept_fn(_Iter, __priority_tag<1>) -> class _ITER_TRAITS<_Iter>::iterator_category;
+template <class _Iter>
+auto __iter_concept_fn(_Iter, __priority_tag<0>)
+  -> enable_if_t<__is_primary_template<iterator_traits<_Iter>>::value, random_access_iterator_tag>;
+
+template <class _Iter>
+using __iter_concept_t =
+  decltype(_CUDA_VSTD::__iter_concept_fn<_Iter>(declval<_Iter>(), __priority_tag<3>{}));
 
-template <class _Iter, class _Tester>
-struct __test_iter_concept
-    : _IsValidExpansion<_Tester::template _Apply, _Iter>
-    , _Tester
+template <class _Iter, class = void>
+struct __iter_concept_cache : __type_defer_quote<__iter_concept_t, _Iter>
 {};
 
 template <class _Iter>
-struct __iter_concept_cache
+struct __iter_concept_cache<_Iter, void_t<__iter_concept_t<_Iter>>>
 {
-  using type = _Or<__test_iter_concept<_Iter, __iter_concept_concept_test>,
-                   __test_iter_concept<_Iter, __iter_concept_category_test>,
-                   __test_iter_concept<_Iter, __iter_concept_random_fallback>>;
+  using type = __iter_concept_t<_Iter>;
 };
 
 template <class _Iter>
-using _ITER_CONCEPT = typename __iter_concept_cache<_Iter>::type::template _Apply<_Iter>;
+using _ITER_CONCEPT = typename __iter_concept_cache<_Iter>::type;
 
 template <class _Tp>
 struct __has_iterator_typedefs