This is my review of the proposed fixed_string library. Notes: - The list of member functions should include a full declaration so I know what's what. Other than that it does the job, though it would be nice to have a hierarchical TOC on the side for reference. - Add constexpr and noexcept where appropriate. - There was a discussion on whether or not resize should call boost::throw_exception. It should (as it does) because A) buffer overruns are gnarly and B) the overhead of the check is negligible, considering this is supposed to be a universal library. - Operator+ should be provided. I'm not sure whether it should use capacity N+M or something else, but all technical questions notwithstanding, users ought to be able to concatenate strings easily, e.g. if I want to add a "ms" to a number I shouldn't be jumping through hoops. - It's nice that the authors are concerned about physical coupling, but there are good reasons to provide (in addition) a single-header version (e.g. Godbolt). My vote is to accept.