Historically our header files have carried the .h suffix. Most toolchains consider that to be a C header, not C++. That hasn't been an issue in practice, for the most part, since the build system decides whether to build with C or C++ based on source file extensions, not header files. However, we do have tooling that wants to operate on header files directly sometimes, via things like clang-format or related IDE tooling. The use of the C-associated suffix can be misleading for those tools.

We should evaluate whether we can bulk migrate our header files to a .hpp suffix.