I'm not sure why Include/cpython/ is part of the compiler include directories. I am not sure why Include/ is *not* part of the compiler include directory.

Anyway, it's hard to control how people build Python and there are always legit use cases where you fall into such issue.

That's why I suggest to fix any risk of confusion by renaming Include/cpython/ header files to add a "cpython_" prefix. For example, rename Include/cpython/pystate.h to Include/cpython/cpython_pystate.h.

In the Include/internal/ directory, header files already have a prefix for the exact same reason. For example, there is a pycore_pystate.h file there.