diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 625059b3..cd868f60 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -61,6 +61,13 @@ jobs:
             build_type: Debug
             cxx_flags: "-fsanitize=address,undefined"
 
+          - name: "Unit gcc13 Debug"
+            cxx: "g++-13"
+            cc: "gcc-13"
+            pkg: "gcc-13 g++-13"
+            build: unit
+            build_type: Debug
+
           - name: "Integration gcc12"
             cxx: "g++-12"
             cc: "gcc-12"
diff --git a/include/bio/alphabet/base.hpp b/include/bio/alphabet/base.hpp
index 99ce7428..0e5c8ad0 100644
--- a/include/bio/alphabet/base.hpp
+++ b/include/bio/alphabet/base.hpp
@@ -200,7 +200,8 @@ class base
     friend constexpr auto tag_invoke(custom::to_rank, derived_type const a) noexcept { return a.to_rank(); }
 
     //!\brief tag_invoke() wrapper around member.
-    friend constexpr derived_type & tag_invoke(custom::assign_rank_to, rank_type const r, derived_type & a) noexcept
+    template <std::same_as<derived_type> derived_type_>
+    friend constexpr derived_type & tag_invoke(custom::assign_rank_to, rank_type const r, derived_type_ & a) noexcept
         requires(requires {
             {
                 a.assign_rank(r)
@@ -211,7 +212,8 @@ class base
     }
 
     //!\brief tag_invoke() wrapper around member.
-    friend constexpr auto tag_invoke(custom::to_char, derived_type const a) noexcept
+    template <std::same_as<derived_type> derived_type_>
+    friend constexpr auto tag_invoke(custom::to_char, derived_type_ const a) noexcept
         requires(requires {
             {
                 a.to_char()
@@ -222,7 +224,8 @@ class base
     }
 
     //!\brief tag_invoke() wrapper around member.
-    friend constexpr derived_type & tag_invoke(custom::assign_char_to, char_type const c, derived_type & a) noexcept
+    template <std::same_as<derived_type> derived_type_>
+    friend constexpr derived_type_ & tag_invoke(custom::assign_char_to, char_type const c, derived_type_ & a) noexcept
         requires(requires {
             {
                 a.assign_char(c)
@@ -233,39 +236,43 @@ class base
     }
 
     //!\brief tag_invoke() wrapper around member.
-    friend constexpr bool tag_invoke(custom::char_is_valid_for, char_type const c, derived_type) noexcept
+    template <std::same_as<derived_type> derived_type_>
+    friend constexpr bool tag_invoke(custom::char_is_valid_for, char_type const c, derived_type_) noexcept
         requires(requires {
             {
-                derived_type::char_is_valid(c)
+                derived_type_::char_is_valid(c)
             };
         })
     {
-        return derived_type::char_is_valid(c);
+        return derived_type_::char_is_valid(c);
     }
 
     //!\brief tag_invoke() wrapper around member.
+    template <std::same_as<derived_type> derived_type_>
     friend constexpr bool tag_invoke(custom::char_is_valid_for,
                                      char_type const c,
-                                     std::type_identity<derived_type>) noexcept
+                                     std::type_identity<derived_type_>) noexcept
         requires(requires {
             {
-                derived_type::char_is_valid(c)
+                derived_type_::char_is_valid(c)
             };
-        } && !meta::constexpr_default_initializable<derived_type>)
+        } && !meta::constexpr_default_initializable<derived_type_>)
     {
-        return derived_type::char_is_valid(c);
+        return derived_type_::char_is_valid(c);
     }
 
     //!\brief tag_invoke() wrapper around member.
-    friend consteval auto tag_invoke(custom::size, derived_type) noexcept
-        requires meta::constexpr_default_initializable<derived_type>
+    template <std::same_as<derived_type> derived_type_>
+    friend consteval auto tag_invoke(custom::size, derived_type_) noexcept
+        requires meta::constexpr_default_initializable<derived_type_>
     {
         return size;
     }
 
     //!\brief tag_invoke() wrapper around member.
-    friend consteval auto tag_invoke(custom::size, std::type_identity<derived_type>) noexcept
-        requires(!meta::constexpr_default_initializable<derived_type>)
+    template <std::same_as<derived_type> derived_type_>
+    friend consteval auto tag_invoke(custom::size, std::type_identity<derived_type_>) noexcept
+        requires(!meta::constexpr_default_initializable<derived_type_>)
     {
         return size;
     }
@@ -367,7 +374,8 @@ class base<derived_type, 1ul, char_t>
     }
 
     //!\brief tag_invoke() wrapper around member.
-    friend constexpr auto tag_invoke(custom::to_char, derived_type const a) noexcept
+    template <std::same_as<derived_type> derived_type_>
+    friend constexpr auto tag_invoke(custom::to_char, derived_type_ const a) noexcept
         requires(requires {
             {
                 a.to_char()
@@ -378,7 +386,8 @@ class base<derived_type, 1ul, char_t>
     }
 
     //!\brief tag_invoke() wrapper around member.
-    friend constexpr derived_type & tag_invoke(custom::assign_char_to, char_type const c, derived_type & a) noexcept
+    template <std::same_as<derived_type> derived_type_>
+    friend constexpr derived_type_ & tag_invoke(custom::assign_char_to, char_type const c, derived_type_ & a) noexcept
         requires(requires {
             {
                 a.assign_char(c)
@@ -389,39 +398,43 @@ class base<derived_type, 1ul, char_t>
     }
 
     //!\brief tag_invoke() wrapper around member.
-    friend constexpr bool tag_invoke(custom::char_is_valid_for, char_type const c, derived_type) noexcept
+    template <std::same_as<derived_type> derived_type_>
+    friend constexpr bool tag_invoke(custom::char_is_valid_for, char_type const c, derived_type_) noexcept
         requires(requires {
             {
-                derived_type::char_is_valid(c)
+                derived_type_::char_is_valid(c)
             };
-        } && std::is_nothrow_default_constructible_v<derived_type>)
+        } && std::is_nothrow_default_constructible_v<derived_type_>)
     {
-        return derived_type::char_is_valid(c);
+        return derived_type_::char_is_valid(c);
     }
 
     //!\brief tag_invoke() wrapper around member.
+    template <std::same_as<derived_type> derived_type_>
     friend constexpr bool tag_invoke(custom::char_is_valid_for,
                                      char_type const c,
-                                     std::type_identity<derived_type>) noexcept
+                                     std::type_identity<derived_type_>) noexcept
         requires(requires {
             {
-                derived_type::char_is_valid(c)
+                derived_type_::char_is_valid(c)
             };
-        } && !std::is_nothrow_default_constructible_v<derived_type>)
+        } && !std::is_nothrow_default_constructible_v<derived_type_>)
     {
-        return derived_type::char_is_valid(c);
+        return derived_type_::char_is_valid(c);
     }
 
     //!\brief tag_invoke() wrapper around member.
-    friend consteval auto tag_invoke(custom::size, derived_type) noexcept
-        requires meta::constexpr_default_initializable<derived_type>
+    template <std::same_as<derived_type> derived_type_>
+    friend consteval auto tag_invoke(custom::size, derived_type_) noexcept
+        requires meta::constexpr_default_initializable<derived_type_>
     {
         return alphabet_size;
     }
 
     //!\brief tag_invoke() wrapper around member.
-    friend consteval auto tag_invoke(custom::size, std::type_identity<derived_type>) noexcept
-        requires(!meta::constexpr_default_initializable<derived_type>)
+    template <std::same_as<derived_type> derived_type_>
+    friend consteval auto tag_invoke(custom::size, std::type_identity<derived_type_>) noexcept
+        requires(!meta::constexpr_default_initializable<derived_type_>)
     {
         return alphabet_size;
     }
diff --git a/include/bio/alphabet/proxy_base.hpp b/include/bio/alphabet/proxy_base.hpp
index f7f7791e..52faf48d 100644
--- a/include/bio/alphabet/proxy_base.hpp
+++ b/include/bio/alphabet/proxy_base.hpp
@@ -286,7 +286,8 @@ class proxy_base
     friend constexpr auto tag_invoke(custom::to_rank, derived_type const a) noexcept { return a.to_rank(); }
 
     //!\brief tag_invoke() wrapper around member.
-    friend constexpr derived_type & tag_invoke(custom::assign_rank_to, auto const r, derived_type & a) noexcept
+    template <std::same_as<derived_type> derived_type_>
+    friend constexpr derived_type_ & tag_invoke(custom::assign_rank_to, auto const r, derived_type_ & a) noexcept
         requires(requires {
             {
                 a.assign_rank(r)
@@ -297,9 +298,10 @@ class proxy_base
     }
 
     //!\brief tag_invoke() wrapper around member.
-    friend constexpr derived_type const & tag_invoke(custom::assign_rank_to,
-                                                     auto const           r,
-                                                     derived_type const & a) noexcept
+    template <std::same_as<derived_type> derived_type_>
+    friend constexpr derived_type_ const & tag_invoke(custom::assign_rank_to,
+                                                      auto const            r,
+                                                      derived_type_ const & a) noexcept
         requires(requires {
             {
                 a.assign_rank(r)
@@ -310,7 +312,8 @@ class proxy_base
     }
 
     //!\brief tag_invoke() wrapper around member.
-    friend constexpr auto tag_invoke(custom::to_char, derived_type const a) noexcept
+    template <std::same_as<derived_type> derived_type_>
+    friend constexpr auto tag_invoke(custom::to_char, derived_type_ const a) noexcept
         requires(requires {
             {
                 a.to_char()
@@ -321,7 +324,8 @@ class proxy_base
     }
 
     //!\brief tag_invoke() wrapper around member.
-    friend constexpr derived_type & tag_invoke(custom::assign_char_to, char_type const c, derived_type & a) noexcept
+    template <std::same_as<derived_type> derived_type_>
+    friend constexpr derived_type_ & tag_invoke(custom::assign_char_to, char_type const c, derived_type_ & a) noexcept
         requires(requires {
             {
                 a.assign_char(c)
@@ -332,9 +336,10 @@ class proxy_base
     }
 
     //!\brief tag_invoke() wrapper around member.
-    friend constexpr derived_type const & tag_invoke(custom::assign_char_to,
-                                                     char_type const      c,
-                                                     derived_type const & a) noexcept
+    template <std::same_as<derived_type> derived_type_>
+    friend constexpr derived_type_ const & tag_invoke(custom::assign_char_to,
+                                                      char_type const       c,
+                                                      derived_type_ const & a) noexcept
         requires(requires {
             {
                 a.assign_char(c)
@@ -345,45 +350,50 @@ class proxy_base
     }
 
     //!\brief tag_invoke() wrapper around member.
-    friend constexpr bool tag_invoke(custom::char_is_valid_for, char_type const c, derived_type) noexcept
+    template <std::same_as<derived_type> derived_type_>
+    friend constexpr bool tag_invoke(custom::char_is_valid_for, char_type const c, derived_type_) noexcept
         requires(requires {
             {
-                derived_type::char_is_valid(c)
+                derived_type_::char_is_valid(c)
             };
         })
     {
-        return derived_type::char_is_valid(c);
+        return derived_type_::char_is_valid(c);
     }
 
     //!\brief tag_invoke() wrapper around member.
+    template <std::same_as<derived_type> derived_type_>
     friend constexpr bool tag_invoke(custom::char_is_valid_for,
                                      char_type const c,
-                                     std::type_identity<derived_type>) noexcept
+                                     std::type_identity<derived_type_>) noexcept
         requires(requires {
             {
-                derived_type::char_is_valid(c)
+                derived_type_::char_is_valid(c)
             };
-        } && !meta::constexpr_default_initializable<derived_type>)
+        } && !meta::constexpr_default_initializable<derived_type_>)
     {
-        return derived_type::char_is_valid(c);
+        return derived_type_::char_is_valid(c);
     }
 
     //!\brief tag_invoke() wrapper around member.
-    friend consteval auto tag_invoke(custom::size, derived_type) noexcept
-        requires meta::constexpr_default_initializable<derived_type>
+    template <std::same_as<derived_type> derived_type_>
+    friend consteval auto tag_invoke(custom::size, derived_type_) noexcept
+        requires meta::constexpr_default_initializable<derived_type_>
     {
         return alphabet_size;
     }
 
     //!\brief tag_invoke() wrapper around member.
-    friend consteval auto tag_invoke(custom::size, std::type_identity<derived_type>) noexcept
-        requires(!meta::constexpr_default_initializable<derived_type>)
+    template <std::same_as<derived_type> derived_type_>
+    friend consteval auto tag_invoke(custom::size, std::type_identity<derived_type_>) noexcept
+        requires(!meta::constexpr_default_initializable<derived_type_>)
     {
         return alphabet_size;
     }
 
     //!\brief tag_invoke() wrapper around member.
-    friend constexpr auto tag_invoke(custom::complement, derived_type const a) noexcept
+    template <std::same_as<derived_type> derived_type_>
+    friend constexpr auto tag_invoke(custom::complement, derived_type_ const a) noexcept
         requires(requires {
             {
                 a.complement()
@@ -394,7 +404,8 @@ class proxy_base
     }
 
     //!\brief tag_invoke() wrapper around member.
-    friend constexpr phred_type tag_invoke(custom::to_phred, derived_type const a) noexcept
+    template <std::same_as<derived_type> derived_type_>
+    friend constexpr phred_type tag_invoke(custom::to_phred, derived_type_ const a) noexcept
         requires(requires {
             {
                 a.to_phred()
@@ -405,7 +416,8 @@ class proxy_base
     }
 
     //!\brief tag_invoke() wrapper around member.
-    friend constexpr derived_type & tag_invoke(custom::assign_phred_to, phred_type const p, derived_type & a) noexcept
+    template <std::same_as<derived_type> derived_type_>
+    friend constexpr derived_type_ & tag_invoke(custom::assign_phred_to, phred_type const p, derived_type_ & a) noexcept
         requires(requires {
             {
                 a.assign_phred(p)
@@ -416,9 +428,10 @@ class proxy_base
     }
 
     //!\brief tag_invoke() wrapper around member.
-    friend constexpr derived_type const & tag_invoke(custom::assign_phred_to,
-                                                     phred_type const     p,
-                                                     derived_type const & a) noexcept
+    template <std::same_as<derived_type> derived_type_>
+    friend constexpr derived_type_ const & tag_invoke(custom::assign_phred_to,
+                                                      phred_type const      p,
+                                                      derived_type_ const & a) noexcept
         requires(requires {
             {
                 a.assign_phred(p)
diff --git a/include/bio/ranges/detail/inherited_iterator_base.hpp b/include/bio/ranges/detail/inherited_iterator_base.hpp
index 5c9f1df7..d5d34a54 100644
--- a/include/bio/ranges/detail/inherited_iterator_base.hpp
+++ b/include/bio/ranges/detail/inherited_iterator_base.hpp
@@ -185,17 +185,17 @@ class inherited_iterator_base :
 
     //!\brief Post-increment, return previous iterator state.
     //!\cond
-    template <typename base_t_ = base_t>
+    template <typename base_t_ = base_t, std::same_as<derived_t> derived_t_ = derived_t>
     //!\endcond
-    constexpr derived_t operator++(int) noexcept(
-      noexcept(std::declval<base_t &>()++) && noexcept(derived_t(std::declval<base_t &>())))
+    constexpr derived_t_ operator++(int) noexcept(
+      noexcept(std::declval<base_t &>()++) && noexcept(derived_t_(std::declval<base_t &>())))
       //!\cond
         requires(requires(base_t_ i) {
             i++;
             {
                 i++
             } -> std::same_as<base_t_>;
-        } && std::constructible_from<derived_t, base_t_>)
+        } && std::constructible_from<derived_t_, base_t_>)
     //!\endcond
     {
         return derived_t{(*this_to_base())++};
@@ -214,13 +214,13 @@ class inherited_iterator_base :
 
     //!\brief Post-decrement, return previous iterator state.
     //!\cond
-    template <typename base_t_ = base_t>
+    template <typename base_t_ = base_t, std::same_as<derived_t> derived_t_ = derived_t>
     //!\endcond
-    constexpr derived_t operator--(int) noexcept(
-      noexcept(std::declval<base_t &>()--) && noexcept(derived_t{std::declval<base_t &>()}))
-        requires(requires(base_t_ i) { i--; } && std::constructible_from<derived_t, base_t_>)
+    constexpr derived_t_ operator--(int) noexcept(
+      noexcept(std::declval<base_t &>()--) && noexcept(derived_t_{std::declval<base_t &>()}))
+        requires(requires(base_t_ i) { i--; } && std::constructible_from<derived_t_, base_t_>)
     {
-        return derived_t{(*this_to_base())--};
+        return derived_t_{(*this_to_base())--};
     }
 
     //!\brief Move iterator to the right.
@@ -236,23 +236,24 @@ class inherited_iterator_base :
 
     //!\brief Returns an iterator which is advanced by `skip` positions.
     //!\cond
-    template <typename base_t_ = base_t>
+    template <typename base_t_ = base_t, std::same_as<derived_t> derived_t_ = derived_t>
     //!\endcond
-    constexpr derived_t operator+(difference_type const skip) const
-      noexcept(noexcept(std::declval<base_t &>() + skip) && noexcept(derived_t{std::declval<base_t &>()}))
+    constexpr derived_t_ operator+(difference_type const skip) const
+      noexcept(noexcept(std::declval<base_t &>() + skip) && noexcept(derived_t_{std::declval<base_t &>()}))
         requires(requires(base_t_ const i, difference_type const n) { i + n; } &&
-                 std::constructible_from<derived_t, base_t_>)
+                 std::constructible_from<derived_t_, base_t_>)
     {
-        return derived_t{*this_to_base() + skip};
+        return derived_t_{*this_to_base() + skip};
     }
 
     //!\brief Non-member operator+ delegates to non-friend operator+.
-    constexpr friend derived_t operator+(difference_type const skip,
-                                         derived_t const & it) noexcept(noexcept(skip + std::declval<base_t const &>()))
+    template <std::same_as<derived_t> derived_t_ = derived_t>
+    constexpr friend derived_t_ operator+(difference_type const skip, derived_t_ const & it) noexcept(
+      noexcept(skip + std::declval<base_t const &>()))
         requires(requires(base_t const i, difference_type const n) { n + i; } &&
-                 std::constructible_from<derived_t, base_t>)
+                 std::constructible_from<derived_t_, base_t>)
     {
-        return derived_t{skip + static_cast<base_t const &>(it)};
+        return derived_t_{skip + static_cast<base_t const &>(it)};
     }
 
     //!\brief Decrement iterator by skip.
@@ -268,13 +269,14 @@ class inherited_iterator_base :
 
     //!\brief Return decremented copy of this iterator.
     //!\cond
-    template <typename base_t_ = base_t>
+    template <typename base_t_ = base_t, std::same_as<derived_t> derived_t_ = derived_t>
     //!\endcond
-    constexpr derived_t operator-(difference_type const skip) const
-      noexcept(noexcept(std::declval<base_t const &>() - skip) && noexcept(derived_t(std::declval<base_t &>())))
-        requires(requires(base_t_ i, difference_type const n) { i - n; } && std::constructible_from<derived_t, base_t_>)
+    constexpr derived_t_ operator-(difference_type const skip) const
+      noexcept(noexcept(std::declval<base_t const &>() - skip) && noexcept(derived_t_(std::declval<base_t &>())))
+        requires(requires(base_t_ i, difference_type const n) { i - n; } &&
+                 std::constructible_from<derived_t_, base_t_>)
     {
-        return derived_t{*this_to_base() - skip};
+        return derived_t_{*this_to_base() - skip};
     }
 
     //!\brief Return offset between this and remote iterator's position.