diff --git a/libcxx/docs/Status/Cxx2bIssues.csv b/libcxx/docs/Status/Cxx2bIssues.csv
--- a/libcxx/docs/Status/Cxx2bIssues.csv
+++ b/libcxx/docs/Status/Cxx2bIssues.csv
@@ -308,3 +308,4 @@
 "`3881 <https://wg21.link/LWG3881>`__","Incorrect formatting of container adapters backed by ``std::string``","February 2023","|Complete|","17.0","|format|"
 "","","","","",""
 "`3343 <https://wg21.link/LWG3343>`__","Ordering of calls to ``unlock()`` and ``notify_all()`` in Effects element of ``notify_all_at_thread_exit()`` should be reversed","Not Yet Adopted","|Complete|","16.0",""
+"`3892 <https://wg21.link/LWG3892>`__","Incorrect formatting of nested ranges and tuples","Not Yet Adopted","|Complete|","17.0",""
diff --git a/libcxx/include/__format/formatter_tuple.h b/libcxx/include/__format/formatter_tuple.h
--- a/libcxx/include/__format/formatter_tuple.h
+++ b/libcxx/include/__format/formatter_tuple.h
@@ -53,33 +53,38 @@
   _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __parse_ctx) {
     auto __begin = __parser_.__parse(__parse_ctx, __format_spec::__fields_tuple);
 
-    // [format.tuple]/7
-    //   ... For each element e in underlying_, if e.set_debug_format()
-    //   is a valid expression, calls e.set_debug_format().
-    // TODO FMT this can be removed when P2733 is accepted.
-    std::__for_each_index_sequence(make_index_sequence<sizeof...(_Args)>(), [&]<size_t _Index> {
-      std::__set_debug_format(std::get<_Index>(__underlying_));
-    });
-
     auto __end = __parse_ctx.end();
-    if (__begin == __end)
-      return __begin;
-
-    if (*__begin == _CharT('m')) {
-      if constexpr (sizeof...(_Args) == 2) {
-        set_separator(_LIBCPP_STATICALLY_WIDEN(_CharT, ": "));
+    if (__begin != __end) {
+      if (*__begin == _CharT('m')) {
+        if constexpr (sizeof...(_Args) == 2) {
+          set_separator(_LIBCPP_STATICALLY_WIDEN(_CharT, ": "));
+          set_brackets({}, {});
+          ++__begin;
+        } else
+          std::__throw_format_error("The format specifier m requires a pair or a two-element tuple");
+      } else if (*__begin == _CharT('n')) {
         set_brackets({}, {});
         ++__begin;
-      } else
-        std::__throw_format_error("The format specifier m requires a pair or a two-element tuple");
-    } else if (*__begin == _CharT('n')) {
-      set_brackets({}, {});
-      ++__begin;
+      }
     }
 
     if (__begin != __end && *__begin != _CharT('}'))
       std::__throw_format_error("The format-spec should consume the input or end with a '}'");
 
+    __parse_ctx.advance_to(__begin);
+
+    // [format.tuple]/7
+    //   ... For each element e in underlying_, if e.set_debug_format()
+    //   is a valid expression, calls e.set_debug_format().
+    std::__for_each_index_sequence(make_index_sequence<sizeof...(_Args)>(), [&]<size_t _Index> {
+      auto& __formatter = std::get<_Index>(__underlying_);
+      __formatter.parse(__parse_ctx);
+      // Unlike the range_formatter we don't guard against evil parsers. Since
+      // this format-spec never has a format-spec for the underlying type
+      // adding the test would give additional overhead.
+      std::__set_debug_format(__formatter);
+    });
+
     return __begin;
   }
 
@@ -120,35 +125,7 @@
     std::__for_each_index_sequence(make_index_sequence<sizeof...(_Args)>(), [&]<size_t _Index> {
       if constexpr (_Index)
         __ctx.advance_to(std::ranges::copy(__separator_, __ctx.out()).out);
-
-        // During review Victor suggested to make the exposition only
-        // __underlying_ member a local variable. Currently the Standard
-        // requires nested debug-enabled formatter specializations not to
-        // output escaped output. P2733 fixes that bug, once accepted the
-        // code below can be used.
-        // (Note when a paper allows parsing a tuple-underlying-spec the
-        // exposition only member needs to be a class member. Earlier
-        // revisions of P2286 proposed that, but this was not pursued,
-        // due to time constrains and complexity of the matter.)
-        // TODO FMT This can be updated after P2733 is accepted.
-#  if 0
-      // P2286 uses an exposition only member in the formatter
-      //   tuple<formatter<remove_cvref_t<_Args>, _CharT>...> __underlying_;
-      // This was used in earlier versions of the paper since
-      // __underlying_.parse(...) was called. This is no longer the case
-      // so we can reduce the scope of the formatter.
-      //
-      // It does require the underlying's parse effect to be moved here too.
-      using _Arg = tuple_element<_Index, decltype(__tuple)>;
-      formatter<remove_cvref_t<_Args>, _CharT> __underlying;
-
-      // [format.tuple]/7
-      //   ... For each element e in underlying_, if e.set_debug_format()
-      //   is a valid expression, calls e.set_debug_format().
-      std::__set_debug_format(__underlying);
-#  else
       __ctx.advance_to(std::get<_Index>(__underlying_).format(std::get<_Index>(__tuple), __ctx));
-#  endif
     });
 
     return std::ranges::copy(__closing_bracket_, __ctx.out()).out;
diff --git a/libcxx/include/__format/range_formatter.h b/libcxx/include/__format/range_formatter.h
--- a/libcxx/include/__format/range_formatter.h
+++ b/libcxx/include/__format/range_formatter.h
@@ -57,28 +57,57 @@
   _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator parse(_ParseContext& __parse_ctx) {
     auto __begin = __parser_.__parse(__parse_ctx, __format_spec::__fields_range);
     auto __end   = __parse_ctx.end();
-    if (__begin == __end)
-      return __begin;
+    // Note the cases where __begin == __end in this code only happens when the
+    // replacement-field has no terminating }, or when the parse is manually
+    // called with a format-spec. The former is an error and the latter means
+    // using a formatter without the format functions or print.
+    if (__begin == __end) [[unlikely]]
+      return __parse_empty_range_underlying_spec(__parse_ctx, __begin);
 
     // The n field overrides a possible m type, therefore delay applying the
     // effect of n until the type has been procesed.
     bool __clear_brackets = (*__begin == _CharT('n'));
     if (__clear_brackets) {
       ++__begin;
-      if (__begin == __end) {
+      if (__begin == __end) [[unlikely]] {
         // Since there is no more data, clear the brackets before returning.
         set_brackets({}, {});
-        return __begin;
+        return __parse_empty_range_underlying_spec(__parse_ctx, __begin);
       }
     }
 
     __parse_type(__begin, __end);
     if (__clear_brackets)
       set_brackets({}, {});
-    if (__begin == __end)
-      return __begin;
+    if (__begin == __end) [[unlikely]]
+      return __parse_empty_range_underlying_spec(__parse_ctx, __begin);
 
     bool __has_range_underlying_spec = *__begin == _CharT(':');
+    if (__has_range_underlying_spec) {
+      // range-underlying-spec:
+      //   :  format-spec
+      ++__begin;
+    } else if (__begin != __end && *__begin != _CharT('}'))
+      // When there is no underlaying range the current parse should have
+      // consumed the format-spec. If not, the not consumed input will be
+      // processed by the underlying. For example {:-} for a range in invalid,
+      // the sign field is not present. Without this check the underlying_ will
+      // get -} as input which my be valid.
+      std::__throw_format_error("The format-spec should consume the input or end with a '}'");
+
+    __parse_ctx.advance_to(__begin);
+    __begin = __underlying_.parse(__parse_ctx);
+
+    // This test should not be required if __has_range_underlying_spec is false.
+    // However this test makes sure the underlying formatter left the parser in
+    // a valid state. (Note this is not a full protection against evil parsers.
+    // For example
+    //   } this is test for the next argument {}
+    //   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
+    // could consume more than it should.
+    if (__begin != __end && *__begin != _CharT('}'))
+      std::__throw_format_error("The format-spec should consume the input or end with a '}'");
+
     if (__parser_.__type_ != __format_spec::__type::__default) {
       // [format.range.formatter]/6
       //   If the range-type is s or ?s, then there shall be no n option and no
@@ -96,20 +125,6 @@
     } else if (!__has_range_underlying_spec)
       std::__set_debug_format(__underlying_);
 
-    if (__has_range_underlying_spec) {
-      // range-underlying-spec:
-      //   :  format-spec
-      ++__begin;
-      if (__begin == __end)
-        return __begin;
-
-      __parse_ctx.advance_to(__begin);
-      __begin = __underlying_.parse(__parse_ctx);
-    }
-
-    if (__begin != __end && *__begin != _CharT('}'))
-      std::__throw_format_error("The format-spec should consume the input or end with a '}'");
-
     return __begin;
   }
 
@@ -243,6 +258,16 @@
     }
   }
 
+  template <class _ParseContext>
+  _LIBCPP_HIDE_FROM_ABI constexpr typename _ParseContext::iterator
+  __parse_empty_range_underlying_spec(_ParseContext& __parse_ctx, _ParseContext::iterator __begin) {
+    __parse_ctx.advance_to(__begin);
+    [[maybe_unused]] typename _ParseContext::iterator __result = __underlying_.parse(__parse_ctx);
+    _LIBCPP_ASSERT(__result == __begin,
+                   "the underlying's parse function should not advance the input beyond the end of the input");
+    return __begin;
+  }
+
   formatter<_Tp, _CharT> __underlying_;
   basic_string_view<_CharT> __separator_       = _LIBCPP_STATICALLY_WIDEN(_CharT, ", ");
   basic_string_view<_CharT> __opening_bracket_ = _LIBCPP_STATICALLY_WIDEN(_CharT, "[");
diff --git a/libcxx/test/std/utilities/format/format.range/format.range.fmtdef/format.pass.cpp b/libcxx/test/std/utilities/format/format.range/format.range.fmtdef/format.pass.cpp
--- a/libcxx/test/std/utilities/format/format.range/format.range.fmtdef/format.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.range/format.range.fmtdef/format.pass.cpp
@@ -30,6 +30,8 @@
 #include <format>
 #include <iterator>
 
+#include "assert_macros.h"
+#include "format.functions.common.h"
 #include "test_format_context.h"
 #include "test_macros.h"
 #include "make_string.h"
@@ -52,10 +54,51 @@
   assert(result == expected);
 }
 
+template <class CharT>
+void test_assure_parse_is_called(std::basic_string_view<CharT> fmt) {
+  using String     = std::basic_string<CharT>;
+  using OutIt      = std::back_insert_iterator<String>;
+  using FormatCtxT = std::basic_format_context<OutIt, CharT>;
+  std::array<parse_call_validator, 2> arg;
+
+  String result;
+  OutIt out             = std::back_inserter(result);
+  FormatCtxT format_ctx = test_format_context_create<OutIt, CharT>(out, std::make_format_args<FormatCtxT>(arg));
+
+  std::formatter<decltype(arg), CharT> formatter;
+  std::basic_format_parse_context<CharT> ctx{fmt};
+
+  formatter.parse(ctx);
+  formatter.format(arg, format_ctx);
+}
+
+template <class CharT>
+void test_assure_parse_is_called() {
+  using String     = std::basic_string<CharT>;
+  using OutIt      = std::back_insert_iterator<String>;
+  using FormatCtxT = std::basic_format_context<OutIt, CharT>;
+  std::array<parse_call_validator, 2> arg;
+
+  String result;
+  OutIt out             = std::back_inserter(result);
+  FormatCtxT format_ctx = test_format_context_create<OutIt, CharT>(out, std::make_format_args<FormatCtxT>(arg));
+
+  { // parse not called
+    [[maybe_unused]] const std::formatter<decltype(arg), CharT> formatter;
+    TEST_THROWS_TYPE(parse_call_validator::parse_function_not_called, formatter.format(arg, format_ctx));
+  }
+
+  test_assure_parse_is_called(SV("5"));
+  test_assure_parse_is_called(SV("n"));
+  test_assure_parse_is_called(SV("5n"));
+}
+
 template <class CharT>
 void test_fmt() {
   test_format(SV("[1, 42]"), std::array<int, 2>{{1, 42}});
   test_format(SV("[0, 99]"), std::array<int, 2>{{0, 99}});
+
+  test_assure_parse_is_called<CharT>();
 }
 
 void test() {
diff --git a/libcxx/test/std/utilities/format/format.range/format.range.fmtmap/format.functions.format.pass.cpp b/libcxx/test/std/utilities/format/format.range/format.range.fmtmap/format.functions.format.pass.cpp
--- a/libcxx/test/std/utilities/format/format.range/format.range.fmtmap/format.functions.format.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.range/format.range.fmtmap/format.functions.format.pass.cpp
@@ -37,9 +37,10 @@
 auto test = []<class CharT, class... Args>(
                 std::basic_string_view<CharT> expected, test_format_string<CharT, Args...> fmt, Args&&... args) {
   std::basic_string<CharT> out = std::format(fmt, std::forward<Args>(args)...);
-  TEST_REQUIRE(out == expected,
-               TEST_WRITE_CONCATENATED(
-                   "\nFormat string   ", fmt, "\nExpected output ", expected, "\nActual output   ", out, '\n'));
+  TEST_REQUIRE(
+      out == expected,
+      TEST_WRITE_CONCATENATED(
+          "\nFormat string   ", fmt.get(), "\nExpected output ", expected, "\nActual output   ", out, '\n')); // XXX
 };
 
 auto test_exception = []<class CharT, class... Args>(std::string_view, std::basic_string_view<CharT>, Args&&...) {
diff --git a/libcxx/test/std/utilities/format/format.range/format.range.fmtmap/format.functions.tests.h b/libcxx/test/std/utilities/format/format.range/format.range.fmtmap/format.functions.tests.h
--- a/libcxx/test/std/utilities/format/format.range/format.range.fmtmap/format.functions.tests.h
+++ b/libcxx/test/std/utilities/format/format.range/format.range.fmtmap/format.functions.tests.h
@@ -26,20 +26,20 @@
 void test_char(TestFunction check, ExceptionTest check_exception) {
   std::map<CharT, CharT> input{{CharT('a'), CharT('A')}, {CharT('c'), CharT('C')}, {CharT('b'), CharT('B')}};
 
-  check(SV("{a: A, b: B, c: C}"), SV("{}"), input);
+  check(SV("{'a': 'A', 'b': 'B', 'c': 'C'}"), SV("{}"), input);
 
   // ***** underlying has no format-spec
 
   // *** align-fill & width ***
-  check(SV("{a: A, b: B, c: C}     "), SV("{:23}"), input);
-  check(SV("{a: A, b: B, c: C}*****"), SV("{:*<23}"), input);
-  check(SV("__{a: A, b: B, c: C}___"), SV("{:_^23}"), input);
-  check(SV("#####{a: A, b: B, c: C}"), SV("{:#>23}"), input);
+  check(SV("{'a': 'A', 'b': 'B', 'c': 'C'}     "), SV("{:35}"), input);
+  check(SV("{'a': 'A', 'b': 'B', 'c': 'C'}*****"), SV("{:*<35}"), input);
+  check(SV("__{'a': 'A', 'b': 'B', 'c': 'C'}___"), SV("{:_^35}"), input);
+  check(SV("#####{'a': 'A', 'b': 'B', 'c': 'C'}"), SV("{:#>35}"), input);
 
-  check(SV("{a: A, b: B, c: C}     "), SV("{:{}}"), input, 23);
-  check(SV("{a: A, b: B, c: C}*****"), SV("{:*<{}}"), input, 23);
-  check(SV("__{a: A, b: B, c: C}___"), SV("{:_^{}}"), input, 23);
-  check(SV("#####{a: A, b: B, c: C}"), SV("{:#>{}}"), input, 23);
+  check(SV("{'a': 'A', 'b': 'B', 'c': 'C'}     "), SV("{:{}}"), input, 35);
+  check(SV("{'a': 'A', 'b': 'B', 'c': 'C'}*****"), SV("{:*<{}}"), input, 35);
+  check(SV("__{'a': 'A', 'b': 'B', 'c': 'C'}___"), SV("{:_^{}}"), input, 35);
+  check(SV("#####{'a': 'A', 'b': 'B', 'c': 'C'}"), SV("{:#>{}}"), input, 35);
 
   check_exception("The format-spec range-fill field contains an invalid character", SV("{:}<}"), input);
   check_exception("The format-spec range-fill field contains an invalid character", SV("{:{<}"), input);
@@ -63,10 +63,10 @@
   check_exception("The format-spec should consume the input or end with a '}'", SV("{:L}"), input);
 
   // *** n
-  check(SV("__a: A, b: B, c: C___"), SV("{:_^21n}"), input);
+  check(SV("__'a': 'A', 'b': 'B', 'c': 'C'___"), SV("{:_^33n}"), input);
 
   // *** type ***
-  check(SV("__{a: A, b: B, c: C}___"), SV("{:_^23m}"), input); // the m type does the same as the default.
+  check(SV("__{'a': 'A', 'b': 'B', 'c': 'C'}___"), SV("{:_^35m}"), input); // the m type does the same as the default.
   check_exception("The range-format-spec type s requires formatting a character type", SV("{:s}"), input);
   check_exception("The range-format-spec type ?s requires formatting a character type", SV("{:?s}"), input);
 
@@ -134,20 +134,20 @@
   std::map<char, char> input{{'a', 'A'}, {'c', 'C'}, {'b', 'B'}};
 
   using CharT = wchar_t;
-  check(SV("{a: A, b: B, c: C}"), SV("{}"), input);
+  check(SV("{'a': 'A', 'b': 'B', 'c': 'C'}"), SV("{}"), input);
 
   // ***** underlying has no format-spec
 
   // *** align-fill & width ***
-  check(SV("{a: A, b: B, c: C}     "), SV("{:23}"), input);
-  check(SV("{a: A, b: B, c: C}*****"), SV("{:*<23}"), input);
-  check(SV("__{a: A, b: B, c: C}___"), SV("{:_^23}"), input);
-  check(SV("#####{a: A, b: B, c: C}"), SV("{:#>23}"), input);
+  check(SV("{'a': 'A', 'b': 'B', 'c': 'C'}     "), SV("{:35}"), input);
+  check(SV("{'a': 'A', 'b': 'B', 'c': 'C'}*****"), SV("{:*<35}"), input);
+  check(SV("__{'a': 'A', 'b': 'B', 'c': 'C'}___"), SV("{:_^35}"), input);
+  check(SV("#####{'a': 'A', 'b': 'B', 'c': 'C'}"), SV("{:#>35}"), input);
 
-  check(SV("{a: A, b: B, c: C}     "), SV("{:{}}"), input, 23);
-  check(SV("{a: A, b: B, c: C}*****"), SV("{:*<{}}"), input, 23);
-  check(SV("__{a: A, b: B, c: C}___"), SV("{:_^{}}"), input, 23);
-  check(SV("#####{a: A, b: B, c: C}"), SV("{:#>{}}"), input, 23);
+  check(SV("{'a': 'A', 'b': 'B', 'c': 'C'}     "), SV("{:{}}"), input, 35);
+  check(SV("{'a': 'A', 'b': 'B', 'c': 'C'}*****"), SV("{:*<{}}"), input, 35);
+  check(SV("__{'a': 'A', 'b': 'B', 'c': 'C'}___"), SV("{:_^{}}"), input, 35);
+  check(SV("#####{'a': 'A', 'b': 'B', 'c': 'C'}"), SV("{:#>{}}"), input, 35);
 
   check_exception("The format-spec range-fill field contains an invalid character", SV("{:}<}"), input);
   check_exception("The format-spec range-fill field contains an invalid character", SV("{:{<}"), input);
@@ -171,10 +171,10 @@
   check_exception("The format-spec should consume the input or end with a '}'", SV("{:L}"), input);
 
   // *** n
-  check(SV("__a: A, b: B, c: C___"), SV("{:_^21n}"), input);
+  check(SV("__'a': 'A', 'b': 'B', 'c': 'C'___"), SV("{:_^33n}"), input);
 
   // *** type ***
-  check(SV("__{a: A, b: B, c: C}___"), SV("{:_^23m}"), input); // the m type does the same as the default.
+  check(SV("__{'a': 'A', 'b': 'B', 'c': 'C'}___"), SV("{:_^35m}"), input); // the m type does the same as the default.
   check_exception("The range-format-spec type s requires formatting a character type", SV("{:s}"), input);
   check_exception("The range-format-spec type ?s requires formatting a character type", SV("{:?s}"), input);
 
@@ -642,20 +642,20 @@
   std::map<std::basic_string<CharT>, std::basic_string<CharT>> input{
       {STR("hello"), STR("HELLO")}, {STR("world"), STR("WORLD")}};
 
-  check(SV(R"({hello: HELLO, world: WORLD})"), SV("{}"), input);
+  check(SV(R"({"hello": "HELLO", "world": "WORLD"})"), SV("{}"), input);
 
   // ***** underlying has no format-spec
 
   // *** align-fill & width ***
-  check(SV(R"({hello: HELLO, world: WORLD}     )"), SV("{:33}"), input);
-  check(SV(R"({hello: HELLO, world: WORLD}*****)"), SV("{:*<33}"), input);
-  check(SV(R"(__{hello: HELLO, world: WORLD}___)"), SV("{:_^33}"), input);
-  check(SV(R"(#####{hello: HELLO, world: WORLD})"), SV("{:#>33}"), input);
+  check(SV(R"({"hello": "HELLO", "world": "WORLD"}     )"), SV("{:41}"), input);
+  check(SV(R"({"hello": "HELLO", "world": "WORLD"}*****)"), SV("{:*<41}"), input);
+  check(SV(R"(__{"hello": "HELLO", "world": "WORLD"}___)"), SV("{:_^41}"), input);
+  check(SV(R"(#####{"hello": "HELLO", "world": "WORLD"})"), SV("{:#>41}"), input);
 
-  check(SV(R"({hello: HELLO, world: WORLD}     )"), SV("{:{}}"), input, 33);
-  check(SV(R"({hello: HELLO, world: WORLD}*****)"), SV("{:*<{}}"), input, 33);
-  check(SV(R"(__{hello: HELLO, world: WORLD}___)"), SV("{:_^{}}"), input, 33);
-  check(SV(R"(#####{hello: HELLO, world: WORLD})"), SV("{:#>{}}"), input, 33);
+  check(SV(R"({"hello": "HELLO", "world": "WORLD"}     )"), SV("{:{}}"), input, 41);
+  check(SV(R"({"hello": "HELLO", "world": "WORLD"}*****)"), SV("{:*<{}}"), input, 41);
+  check(SV(R"(__{"hello": "HELLO", "world": "WORLD"}___)"), SV("{:_^{}}"), input, 41);
+  check(SV(R"(#####{"hello": "HELLO", "world": "WORLD"})"), SV("{:#>{}}"), input, 41);
 
   check_exception("The format-spec range-fill field contains an invalid character", SV("{:}<}"), input);
   check_exception("The format-spec range-fill field contains an invalid character", SV("{:{<}"), input);
@@ -677,10 +677,10 @@
   check_exception("The format-spec should consume the input or end with a '}'", SV("{:L}"), input);
 
   // *** n
-  check(SV(R"(__hello: HELLO, world: WORLD___)"), SV("{:_^31n}"), input);
+  check(SV(R"(__"hello": "HELLO", "world": "WORLD"___)"), SV("{:_^39n}"), input);
 
   // *** type ***
-  check(SV(R"(__{hello: HELLO, world: WORLD}___)"), SV("{:_^33m}"), input);
+  check(SV(R"(__{"hello": "HELLO", "world": "WORLD"}___)"), SV("{:_^41m}"), input);
   check_exception("The range-format-spec type s requires formatting a character type", SV("{:s}"), input);
   check_exception("The range-format-spec type ?s requires formatting a character type", SV("{:?s}"), input);
 
diff --git a/libcxx/test/std/utilities/format/format.range/format.range.fmtmap/format.pass.cpp b/libcxx/test/std/utilities/format/format.range/format.range.fmtmap/format.pass.cpp
--- a/libcxx/test/std/utilities/format/format.range/format.range.fmtmap/format.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.range/format.range.fmtmap/format.pass.cpp
@@ -33,6 +33,8 @@
 #include <iterator>
 #include <map>
 
+#include "assert_macros.h"
+#include "format.functions.common.h"
 #include "test_format_context.h"
 #include "test_macros.h"
 #include "make_string.h"
@@ -55,10 +57,53 @@
   assert(result == expected);
 }
 
+template <class CharT>
+void test_assure_parse_is_called(std::basic_string_view<CharT> fmt) {
+  using String     = std::basic_string<CharT>;
+  using OutIt      = std::back_insert_iterator<String>;
+  using FormatCtxT = std::basic_format_context<OutIt, CharT>;
+  std::map<parse_call_validator, parse_call_validator> arg{{parse_call_validator{}, parse_call_validator{}}};
+
+  String result;
+  OutIt out             = std::back_inserter(result);
+  FormatCtxT format_ctx = test_format_context_create<OutIt, CharT>(out, std::make_format_args<FormatCtxT>(arg));
+
+  std::formatter<decltype(arg), CharT> formatter;
+  std::basic_format_parse_context<CharT> ctx{fmt};
+
+  formatter.parse(ctx);
+  formatter.format(arg, format_ctx);
+}
+
+template <class CharT>
+void test_assure_parse_is_called() {
+  using String     = std::basic_string<CharT>;
+  using OutIt      = std::back_insert_iterator<String>;
+  using FormatCtxT = std::basic_format_context<OutIt, CharT>;
+  std::map<parse_call_validator, parse_call_validator> arg{{parse_call_validator{}, parse_call_validator{}}};
+
+  String result;
+  OutIt out             = std::back_inserter(result);
+  FormatCtxT format_ctx = test_format_context_create<OutIt, CharT>(out, std::make_format_args<FormatCtxT>(arg));
+
+  { // parse not called
+    [[maybe_unused]] const std::formatter<decltype(arg), CharT> formatter;
+    TEST_THROWS_TYPE(parse_call_validator::parse_function_not_called, formatter.format(arg, format_ctx));
+  }
+
+  test_assure_parse_is_called(SV("5"));
+  test_assure_parse_is_called(SV("n"));
+  test_assure_parse_is_called(SV("m"));
+  test_assure_parse_is_called(SV("5n"));
+  test_assure_parse_is_called(SV("5m"));
+}
+
 template <class CharT>
 void test_fmt() {
   test_format(SV("{1: 42}"), std::map<int, int>{{1, 42}});
   test_format(SV("{0: 99}"), std::map<int, int>{{0, 99}});
+
+  test_assure_parse_is_called<CharT>();
 }
 
 void test() {
diff --git a/libcxx/test/std/utilities/format/format.range/format.range.fmtset/format.functions.format.pass.cpp b/libcxx/test/std/utilities/format/format.range/format.range.fmtset/format.functions.format.pass.cpp
--- a/libcxx/test/std/utilities/format/format.range/format.range.fmtset/format.functions.format.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.range/format.range.fmtset/format.functions.format.pass.cpp
@@ -39,7 +39,7 @@
   std::basic_string<CharT> out = std::format(fmt, std::forward<Args>(args)...);
   TEST_REQUIRE(out == expected,
                TEST_WRITE_CONCATENATED(
-                   "\nFormat string   ", fmt, "\nExpected output ", expected, "\nActual output   ", out, '\n'));
+                   "\nFormat string   ", fmt.get(), "\nExpected output ", expected, "\nActual output   ", out, '\n'));
 };
 
 auto test_exception = []<class CharT, class... Args>(std::string_view, std::basic_string_view<CharT>, Args&&...) {
diff --git a/libcxx/test/std/utilities/format/format.range/format.range.fmtset/format.functions.tests.h b/libcxx/test/std/utilities/format/format.range/format.range.fmtset/format.functions.tests.h
--- a/libcxx/test/std/utilities/format/format.range/format.range.fmtset/format.functions.tests.h
+++ b/libcxx/test/std/utilities/format/format.range/format.range.fmtset/format.functions.tests.h
@@ -1100,20 +1100,20 @@
 
 template <class CharT, class TestFunction, class ExceptionTest>
 void test_pair_tuple(TestFunction check, ExceptionTest check_exception, auto&& input) {
-  check(SV("{(1, a), (42, *)}"), SV("{}"), input);
+  check(SV("{(1, 'a'), (42, '*')}"), SV("{}"), input);
 
   // ***** underlying has no format-spec
 
   // *** align-fill & width ***
-  check(SV("{(1, a), (42, *)}     "), SV("{:22}"), input);
-  check(SV("{(1, a), (42, *)}*****"), SV("{:*<22}"), input);
-  check(SV("__{(1, a), (42, *)}___"), SV("{:_^22}"), input);
-  check(SV("#####{(1, a), (42, *)}"), SV("{:#>22}"), input);
+  check(SV("{(1, 'a'), (42, '*')}     "), SV("{:26}"), input);
+  check(SV("{(1, 'a'), (42, '*')}*****"), SV("{:*<26}"), input);
+  check(SV("__{(1, 'a'), (42, '*')}___"), SV("{:_^26}"), input);
+  check(SV("#####{(1, 'a'), (42, '*')}"), SV("{:#>26}"), input);
 
-  check(SV("{(1, a), (42, *)}     "), SV("{:{}}"), input, 22);
-  check(SV("{(1, a), (42, *)}*****"), SV("{:*<{}}"), input, 22);
-  check(SV("__{(1, a), (42, *)}___"), SV("{:_^{}}"), input, 22);
-  check(SV("#####{(1, a), (42, *)}"), SV("{:#>{}}"), input, 22);
+  check(SV("{(1, 'a'), (42, '*')}     "), SV("{:{}}"), input, 26);
+  check(SV("{(1, 'a'), (42, '*')}*****"), SV("{:*<{}}"), input, 26);
+  check(SV("__{(1, 'a'), (42, '*')}___"), SV("{:_^{}}"), input, 26);
+  check(SV("#####{(1, 'a'), (42, '*')}"), SV("{:#>{}}"), input, 26);
 
   check_exception("The format-spec range-fill field contains an invalid character", SV("{:}<}"), input);
   check_exception("The format-spec range-fill field contains an invalid character", SV("{:{<}"), input);
@@ -1137,11 +1137,11 @@
   check_exception("The format-spec should consume the input or end with a '}'", SV("{:L}"), input);
 
   // *** n
-  check(SV("__(1, a), (42, *)___"), SV("{:_^20n}"), input);
-  check(SV("__(1, a), (42, *)___"), SV("{:_^20nm}"), input); // m should have no effect
+  check(SV("__(1, 'a'), (42, '*')___"), SV("{:_^24n}"), input);
+  check(SV("__(1, 'a'), (42, '*')___"), SV("{:_^24nm}"), input); // m should have no effect
 
   // *** type ***
-  check(SV("__{(1, a), (42, *)}___"), SV("{:_^22m}"), input);
+  check(SV("__{(1, 'a'), (42, '*')}___"), SV("{:_^26m}"), input);
   check_exception("The range-format-spec type s requires formatting a character type", SV("{:s}"), input);
   check_exception("The range-format-spec type ?s requires formatting a character type", SV("{:?s}"), input);
 
diff --git a/libcxx/test/std/utilities/format/format.range/format.range.fmtset/format.pass.cpp b/libcxx/test/std/utilities/format/format.range/format.range.fmtset/format.pass.cpp
--- a/libcxx/test/std/utilities/format/format.range/format.range.fmtset/format.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.range/format.range.fmtset/format.pass.cpp
@@ -33,6 +33,8 @@
 #include <format>
 #include <set>
 
+#include "assert_macros.h"
+#include "format.functions.common.h"
 #include "test_format_context.h"
 #include "test_macros.h"
 #include "make_string.h"
@@ -55,9 +57,50 @@
   assert(result == expected);
 }
 
+template <class CharT>
+void test_assure_parse_is_called(std::basic_string_view<CharT> fmt) {
+  using String     = std::basic_string<CharT>;
+  using OutIt      = std::back_insert_iterator<String>;
+  using FormatCtxT = std::basic_format_context<OutIt, CharT>;
+  std::set<parse_call_validator> arg{parse_call_validator{}};
+
+  String result;
+  OutIt out             = std::back_inserter(result);
+  FormatCtxT format_ctx = test_format_context_create<OutIt, CharT>(out, std::make_format_args<FormatCtxT>(arg));
+
+  std::formatter<decltype(arg), CharT> formatter;
+  std::basic_format_parse_context<CharT> ctx{fmt};
+
+  formatter.parse(ctx);
+  formatter.format(arg, format_ctx);
+}
+
+template <class CharT>
+void test_assure_parse_is_called() {
+  using String     = std::basic_string<CharT>;
+  using OutIt      = std::back_insert_iterator<String>;
+  using FormatCtxT = std::basic_format_context<OutIt, CharT>;
+  std::set<parse_call_validator> arg{parse_call_validator{}};
+
+  String result;
+  OutIt out             = std::back_inserter(result);
+  FormatCtxT format_ctx = test_format_context_create<OutIt, CharT>(out, std::make_format_args<FormatCtxT>(arg));
+
+  { // parse not called
+    [[maybe_unused]] const std::formatter<decltype(arg), CharT> formatter;
+    TEST_THROWS_TYPE(parse_call_validator::parse_function_not_called, formatter.format(arg, format_ctx));
+  }
+
+  test_assure_parse_is_called(SV("5"));
+  test_assure_parse_is_called(SV("n"));
+  test_assure_parse_is_called(SV("5n"));
+}
+
 template <class CharT>
 void test_fmt() {
   test_format(SV("{42}"), std::set<int>{42});
+
+  test_assure_parse_is_called<CharT>();
 }
 
 void test() {
diff --git a/libcxx/test/std/utilities/format/format.range/format.range.formatter/format.functions.format.pass.cpp b/libcxx/test/std/utilities/format/format.range/format.range.formatter/format.functions.format.pass.cpp
--- a/libcxx/test/std/utilities/format/format.range/format.range.formatter/format.functions.format.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.range/format.range.formatter/format.functions.format.pass.cpp
@@ -40,7 +40,7 @@
   std::basic_string<CharT> out = std::format(fmt, std::forward<Args>(args)...);
   TEST_REQUIRE(out == expected,
                TEST_WRITE_CONCATENATED(
-                   "\nFormat string   ", fmt, "\nExpected output ", expected, "\nActual output   ", out, '\n'));
+                   "\nFormat string   ", fmt.get(), "\nExpected output ", expected, "\nActual output   ", out, '\n'));
 };
 
 auto test_exception = []<class CharT, class... Args>(std::string_view, std::basic_string_view<CharT>, Args&&...) {
diff --git a/libcxx/test/std/utilities/format/format.range/format.range.formatter/format.functions.tests.h b/libcxx/test/std/utilities/format/format.range/format.range.formatter/format.functions.tests.h
--- a/libcxx/test/std/utilities/format/format.range/format.range.formatter/format.functions.tests.h
+++ b/libcxx/test/std/utilities/format/format.range/format.range.formatter/format.functions.tests.h
@@ -928,20 +928,20 @@
   // So when there is no range-underlying-spec, there is no need to call parse
   // thus the char element is not escaped.
   // TODO FMT P2733 addresses this issue.
-  check(SV("[(1, a), (42, *)]"), SV("{}"), input);
+  check(SV("[(1, 'a'), (42, '*')]"), SV("{}"), input);
 
   // ***** underlying has no format-spec
 
   // *** align-fill & width ***
-  check(SV("[(1, a), (42, *)]     "), SV("{:22}"), input);
-  check(SV("[(1, a), (42, *)]*****"), SV("{:*<22}"), input);
-  check(SV("__[(1, a), (42, *)]___"), SV("{:_^22}"), input);
-  check(SV("#####[(1, a), (42, *)]"), SV("{:#>22}"), input);
+  check(SV("[(1, 'a'), (42, '*')]     "), SV("{:26}"), input);
+  check(SV("[(1, 'a'), (42, '*')]*****"), SV("{:*<26}"), input);
+  check(SV("__[(1, 'a'), (42, '*')]___"), SV("{:_^26}"), input);
+  check(SV("#####[(1, 'a'), (42, '*')]"), SV("{:#>26}"), input);
 
-  check(SV("[(1, a), (42, *)]     "), SV("{:{}}"), input, 22);
-  check(SV("[(1, a), (42, *)]*****"), SV("{:*<{}}"), input, 22);
-  check(SV("__[(1, a), (42, *)]___"), SV("{:_^{}}"), input, 22);
-  check(SV("#####[(1, a), (42, *)]"), SV("{:#>{}}"), input, 22);
+  check(SV("[(1, 'a'), (42, '*')]     "), SV("{:{}}"), input, 26);
+  check(SV("[(1, 'a'), (42, '*')]*****"), SV("{:*<{}}"), input, 26);
+  check(SV("__[(1, 'a'), (42, '*')]___"), SV("{:_^{}}"), input, 26);
+  check(SV("#####[(1, 'a'), (42, '*')]"), SV("{:#>{}}"), input, 26);
 
   check_exception("The format-spec range-fill field contains an invalid character", SV("{:}<}"), input);
   check_exception("The format-spec range-fill field contains an invalid character", SV("{:{<}"), input);
@@ -965,11 +965,11 @@
   check_exception("The format-spec should consume the input or end with a '}'", SV("{:L}"), input);
 
   // *** n
-  check(SV("__(1, a), (42, *)___"), SV("{:_^20n}"), input);
-  check(SV("__(1, a), (42, *)___"), SV("{:_^20nm}"), input); // m should have no effect
+  check(SV("__(1, 'a'), (42, '*')___"), SV("{:_^24n}"), input);
+  check(SV("__(1, 'a'), (42, '*')___"), SV("{:_^24nm}"), input); // m should have no effect
 
   // *** type ***
-  check(SV("__{(1, a), (42, *)}___"), SV("{:_^22m}"), input);
+  check(SV("__{(1, 'a'), (42, '*')}___"), SV("{:_^26m}"), input);
   check_exception("The range-format-spec type s requires formatting a character type", SV("{:s}"), input);
   check_exception("The range-format-spec type ?s requires formatting a character type", SV("{:?s}"), input);
   for (std::basic_string_view<CharT> fmt : fmt_invalid_types<CharT>("s"))
diff --git a/libcxx/test/std/utilities/format/format.range/format.range.formatter/format.pass.cpp b/libcxx/test/std/utilities/format/format.range/format.range.formatter/format.pass.cpp
--- a/libcxx/test/std/utilities/format/format.range/format.range.formatter/format.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.range/format.range.formatter/format.pass.cpp
@@ -34,9 +34,11 @@
 #include <format>
 #include <vector>
 
+#include "assert_macros.h"
+#include "format.functions.common.h"
+#include "make_string.h"
 #include "test_format_context.h"
 #include "test_macros.h"
-#include "make_string.h"
 
 #define SV(S) MAKE_STRING_VIEW(CharT, S)
 
@@ -56,10 +58,56 @@
   assert(result == expected);
 }
 
+template <class CharT>
+void test_assure_parse_is_called(std::basic_string_view<CharT> fmt) {
+  using String     = std::basic_string<CharT>;
+  using OutIt      = std::back_insert_iterator<String>;
+  using FormatCtxT = std::basic_format_context<OutIt, CharT>;
+  std::vector<parse_call_validator> arg{1};
+
+  String result;
+  OutIt out             = std::back_inserter(result);
+  FormatCtxT format_ctx = test_format_context_create<OutIt, CharT>(out, std::make_format_args<FormatCtxT>(arg));
+
+  std::range_formatter<parse_call_validator, CharT> formatter;
+  std::basic_format_parse_context<CharT> ctx{fmt};
+
+  formatter.parse(ctx);
+  formatter.format(arg, format_ctx);
+}
+
+template <class CharT>
+void test_assure_parse_is_called() {
+  using String     = std::basic_string<CharT>;
+  using OutIt      = std::back_insert_iterator<String>;
+  using FormatCtxT = std::basic_format_context<OutIt, CharT>;
+  std::vector<parse_call_validator> arg{1};
+
+  String result;
+  OutIt out             = std::back_inserter(result);
+  FormatCtxT format_ctx = test_format_context_create<OutIt, CharT>(out, std::make_format_args<FormatCtxT>(arg));
+
+  { // parse not called
+    [[maybe_unused]] const std::range_formatter<parse_call_validator, CharT> formatter;
+    TEST_THROWS_TYPE(parse_call_validator::parse_function_not_called, formatter.format(arg, format_ctx));
+  }
+
+  // The range-format-spec has no range-underlying-spec
+  // This uses various variants, which have different code paths in libc++
+  test_assure_parse_is_called(SV("5"));
+  test_assure_parse_is_called(SV("n"));
+  test_assure_parse_is_called(SV(":"));
+  test_assure_parse_is_called(SV("5"));
+  test_assure_parse_is_called(SV("5n"));
+  test_assure_parse_is_called(SV("5n:"));
+}
+
 template <class CharT>
 void test_fmt() {
   test_format(SV("[1]"), std::vector<int>{1});
   test_format(SV("[0]"), std::vector<int>{0});
+
+  test_assure_parse_is_called<CharT>();
 }
 
 void test() {
diff --git a/libcxx/test/std/utilities/format/format.tuple/format.functions.format.pass.cpp b/libcxx/test/std/utilities/format/format.tuple/format.functions.format.pass.cpp
--- a/libcxx/test/std/utilities/format/format.tuple/format.functions.format.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.tuple/format.functions.format.pass.cpp
@@ -41,7 +41,7 @@
   std::basic_string<CharT> out = std::format(fmt, std::forward<Args>(args)...);
   TEST_REQUIRE(out == expected,
                TEST_WRITE_CONCATENATED(
-                   "\nFormat string   ", fmt, "\nExpected output ", expected, "\nActual output   ", out, '\n'));
+                   "\nFormat string   ", fmt.get(), "\nExpected output ", expected, "\nActual output   ", out, '\n'));
 };
 
 auto test_exception = []<class CharT, class... Args>(std::string_view, std::basic_string_view<CharT>, Args&&...) {
diff --git a/libcxx/test/std/utilities/format/format.tuple/format.functions.tests.h b/libcxx/test/std/utilities/format/format.tuple/format.functions.tests.h
--- a/libcxx/test/std/utilities/format/format.tuple/format.functions.tests.h
+++ b/libcxx/test/std/utilities/format/format.tuple/format.functions.tests.h
@@ -288,18 +288,18 @@
   //   P2733 Fix handling of empty specifiers in std::format
   // addressed this.
 
-  check(SV("(42, (hello, red))"), SV("{}"), input);
+  check(SV("(42, (\"hello\", \"red\"))"), SV("{}"), input);
 
   // *** align-fill & width ***
-  check(SV("(42, (hello, red))     "), SV("{:23}"), input);
-  check(SV("(42, (hello, red))*****"), SV("{:*<23}"), input);
-  check(SV("__(42, (hello, red))___"), SV("{:_^23}"), input);
-  check(SV("#####(42, (hello, red))"), SV("{:#>23}"), input);
+  check(SV("(42, (\"hello\", \"red\"))     "), SV("{:27}"), input);
+  check(SV("(42, (\"hello\", \"red\"))*****"), SV("{:*<27}"), input);
+  check(SV("__(42, (\"hello\", \"red\"))___"), SV("{:_^27}"), input);
+  check(SV("#####(42, (\"hello\", \"red\"))"), SV("{:#>27}"), input);
 
-  check(SV("(42, (hello, red))     "), SV("{:{}}"), input, 23);
-  check(SV("(42, (hello, red))*****"), SV("{:*<{}}"), input, 23);
-  check(SV("__(42, (hello, red))___"), SV("{:_^{}}"), input, 23);
-  check(SV("#####(42, (hello, red))"), SV("{:#>{}}"), input, 23);
+  check(SV("(42, (\"hello\", \"red\"))     "), SV("{:{}}"), input, 27);
+  check(SV("(42, (\"hello\", \"red\"))*****"), SV("{:*<{}}"), input, 27);
+  check(SV("__(42, (\"hello\", \"red\"))___"), SV("{:_^{}}"), input, 27);
+  check(SV("#####(42, (\"hello\", \"red\"))"), SV("{:#>{}}"), input, 27);
 
   check_exception("The format-spec range-fill field contains an invalid character", SV("{:}<}"), input);
   check_exception("The format-spec range-fill field contains an invalid character", SV("{:{<}"), input);
@@ -323,8 +323,8 @@
   check_exception("The format-spec should consume the input or end with a '}'", SV("{:L}"), input);
 
   // *** type ***
-  check(SV("__42: (hello, red)___"), SV("{:_^21m}"), input);
-  check(SV("__42, (hello, red)___"), SV("{:_^21n}"), input);
+  check(SV("__42: (\"hello\", \"red\")___"), SV("{:_^25m}"), input);
+  check(SV("__42, (\"hello\", \"red\")___"), SV("{:_^25n}"), input);
 
   for (CharT c : SV("aAbBcdeEfFgGopsxX?")) {
     check_exception("The format-spec should consume the input or end with a '}'",
diff --git a/libcxx/test/std/utilities/format/format.tuple/format.pass.cpp b/libcxx/test/std/utilities/format/format.tuple/format.pass.cpp
--- a/libcxx/test/std/utilities/format/format.tuple/format.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.tuple/format.pass.cpp
@@ -34,9 +34,11 @@
 #include <tuple>
 #include <utility>
 
+#include "assert_macros.h"
+#include "format.functions.common.h"
+#include "make_string.h"
 #include "test_format_context.h"
 #include "test_macros.h"
-#include "make_string.h"
 
 #define SV(S) MAKE_STRING_VIEW(CharT, S)
 
@@ -56,12 +58,55 @@
   assert(result == expected);
 }
 
+template <class CharT>
+void test_assure_parse_is_called(std::basic_string_view<CharT> fmt) {
+  using String     = std::basic_string<CharT>;
+  using OutIt      = std::back_insert_iterator<String>;
+  using FormatCtxT = std::basic_format_context<OutIt, CharT>;
+  std::pair<parse_call_validator, parse_call_validator> arg;
+
+  String result;
+  OutIt out             = std::back_inserter(result);
+  FormatCtxT format_ctx = test_format_context_create<OutIt, CharT>(out, std::make_format_args<FormatCtxT>(arg));
+
+  std::formatter<decltype(arg), CharT> formatter;
+  std::basic_format_parse_context<CharT> ctx{fmt};
+
+  formatter.parse(ctx);
+  formatter.format(arg, format_ctx);
+}
+
+template <class CharT>
+void test_assure_parse_is_called() {
+  using String     = std::basic_string<CharT>;
+  using OutIt      = std::back_insert_iterator<String>;
+  using FormatCtxT = std::basic_format_context<OutIt, CharT>;
+  std::pair<parse_call_validator, parse_call_validator> arg;
+
+  String result;
+  OutIt out             = std::back_inserter(result);
+  FormatCtxT format_ctx = test_format_context_create<OutIt, CharT>(out, std::make_format_args<FormatCtxT>(arg));
+
+  { // parse not called
+    [[maybe_unused]] const std::formatter<decltype(arg), CharT> formatter;
+    TEST_THROWS_TYPE(parse_call_validator::parse_function_not_called, formatter.format(arg, format_ctx));
+  }
+
+  test_assure_parse_is_called(SV("5"));
+  test_assure_parse_is_called(SV("n"));
+  test_assure_parse_is_called(SV("m"));
+  test_assure_parse_is_called(SV("5n"));
+  test_assure_parse_is_called(SV("5m"));
+}
+
 template <class CharT>
 void test() {
   test(SV("(1)"), std::tuple<int>{1});
   test(SV("(1, 1)"), std::tuple<int, CharT>{1, CharT('1')});
   test(SV("(1, 1)"), std::pair<int, CharT>{1, CharT('1')});
   test(SV("(1, 1, 1)"), std::tuple<int, CharT, double>{1, CharT('1'), 1.0});
+
+  test_assure_parse_is_called<CharT>();
 }
 
 void test() {
diff --git a/libcxx/test/support/format.functions.common.h b/libcxx/test/support/format.functions.common.h
--- a/libcxx/test/support/format.functions.common.h
+++ b/libcxx/test/support/format.functions.common.h
@@ -49,11 +49,17 @@
 // The formatter for a user-defined type used to test the handle formatter.
 template <class CharT>
 struct std::formatter<status, CharT> {
-  int type = 0;
+  // During the 2023 Issaquah meeting LWEG made it clear a formatter is
+  // required to call its parse function. LWG3892 Adds the wording for that
+  // requirement. Therefore this formatter is initialized in an invalid state.
+  // A call to parse sets it in a valid state and a call to format validates
+  // the state.
+  int type = -1;
 
   constexpr auto parse(basic_format_parse_context<CharT>& parse_ctx) -> decltype(parse_ctx.begin()) {
     auto begin = parse_ctx.begin();
-    auto end = parse_ctx.end();
+    auto end   = parse_ctx.end();
+    type       = 0;
     if (begin == end)
       return begin;
 
@@ -86,6 +92,9 @@
     const char* begin = names[0];
     const char* end = names[0];
     switch (type) {
+    case -1:
+      throw_format_error("The formatter's parse function has not been called.");
+
     case 0:
       begin = buffer;
       buffer[0] = '0';
@@ -124,7 +133,7 @@
   }
 
 private:
-  void throw_format_error(const char* s) {
+  void throw_format_error(const char* s) const {
 #ifndef TEST_HAS_NO_EXCEPTIONS
     throw std::format_error(s);
 #else
@@ -134,6 +143,52 @@
   }
 };
 
+struct parse_call_validator {
+  struct parse_function_not_called {};
+
+  friend constexpr auto operator<=>(const parse_call_validator& lhs, const parse_call_validator& rhs) {
+    return &lhs <=> &rhs;
+  }
+};
+
+// The formatter for a user-defined type used to test the handle formatter.
+//
+// Like std::formatter<status, CharT> this formatter validates that parse is
+// called. This formatter is intended to be used when the formatter's parse is
+// called directly and not with format. In that case the format-spec does not
+// require a terminating }. The tests must be written in a fashion where this
+// formatter is always called with an empty format-spec. This requirement
+// allows testing of certain code paths that are never reached by using a
+// well-formed format-string in the format functions.
+template <class CharT>
+struct std::formatter<parse_call_validator, CharT> {
+  bool parse_called{false};
+
+  constexpr auto parse(basic_format_parse_context<CharT>& parse_ctx) -> decltype(parse_ctx.begin()) {
+    auto begin = parse_ctx.begin();
+    auto end   = parse_ctx.end();
+    assert(begin == end);
+    parse_called = true;
+    return begin;
+  }
+
+  auto format(parse_call_validator, auto& ctx) const -> decltype(ctx.out()) {
+    if (!parse_called)
+      throw_error<parse_call_validator::parse_function_not_called>();
+    return ctx.out();
+  }
+
+private:
+  template <class T>
+  [[noreturn]] void throw_error() const {
+#ifndef TEST_HAS_NO_EXCEPTIONS
+    throw T{};
+#else
+    std::abort();
+#endif
+  }
+};
+
 // Creates format string for the invalid types.
 //
 // valid contains a list of types that are valid.