safe_current_working_directory() bypasses the vu_system
I think it should be corrected.

Now it's:
safe_current_working_directory (void) {
   return getcwd()
}

instead it should be
safe_current_working_directory (void) {
   wd = vu_getcwd()
}

and

vu_getcwd() {
   wd = getcwd()
   if (wd is in a registered namespace) {
       wd = (namespace_handler->getcwd)(wd)
   }
   return wd
}

a more fundamental approach would be to make the
vu_ system maintain the current directory...