Proposed resolution:

This wording is relative to N5032.

1. Modify [meta.reflection.exception] as indicated:

   namespace std::meta {
     class exception : public std::exception {
     private:
       optional<string> what_;  // exposition only
       u8string u8what_;        // exposition only
       info from_;              // exposition only
       source_location where_;  // exposition only
     public:
       consteval exception(u8string_view what, info from,
                           source_location where = source_location::current()) noexcept;
   
       consteval exception(string_view what, info from,
                           source_location where = source_location::current()) noexcept;
   
       exception(const exception&) = default;
       exception(exception&&) = default;
   
       exception& operator=(const exception&) = default;
       exception& operator=(exception&&) = default;
   
       constexpr consteval const char* what() const noexcept override;
       consteval u8string_view u8what() const noexcept;
       consteval info from() const noexcept;
       consteval source_location where() const noexcept;
     };
   }
   

   …

   constexpr consteval const char* what() const noexcept override;
   

   -5- Constant when: what_.has_value() is `true`.

As mentioned in LWG 4494, `meta::exception::what()` can be (and should be) marked `consteval` now that CWG 3117 has been approved.