It does but not in a way you probably expect it to be handled: i.e., with some filesystem mechanisms to make the update command only see what has been declared

It does but not in a way you probably expect it to be handled: i.e., with some filesystem mechanisms to make the update command only see what has been declared as target's dependencies -- I must admit I don't know Bazel does this in a cross-platform manner (Windows, Mac OS); copying seems way too heavy-handed. In any case, in build2 this is "handled" by not including headers as "foo.h" but as <libfoo/foo.h>, that is, with the project prefix. You can read more on this here: https://build2.org/build2-toolchain/doc/build2-toolchain-intro.xhtml#proj-struct https://build2.org/build2-toolchain/doc/build2-toolchain-int... And the proper fix will hopefully come with C++20 modules.