/usr/include/ags/thread/ is in libags-dev 1.4.24-1ubuntu2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/ags/thread/ags_autosave_thread.h
/usr/include/ags/thread/ags_concurrency_provider.h
/usr/include/ags/thread/ags_condition_manager.h
/usr/include/ags/thread/ags_destroy_worker.h
/usr/include/ags/thread/ags_generic_main_loop.h
/usr/include/ags/thread/ags_history.h
/usr/include/ags/thread/ags_message_delivery.h
/usr/include/ags/thread/ags_message_queue.h
/usr/include/ags/thread/ags_mutex_manager.h
/usr/include/ags/thread/ags_poll_fd.h
/usr/include/ags/thread/ags_polling_thread.h
/usr/include/ags/thread/ags_returnable_thread.h
/usr/include/ags/thread/ags_single_thread.h
/usr/include/ags/thread/ags_task.h
/usr/include/ags/thread/ags_task_completion.h
/usr/include/ags/thread/ags_task_thread.h
/usr/include/ags/thread/ags_thread-posix.h
/usr/include/ags/thread/ags_thread_application_context.h
/usr/include/ags/thread/ags_thread_pool.h
/usr/include/ags/thread/ags_timestamp.h
/usr/include/ags/thread/ags_timestamp_factory.h
/usr/include/ags/thread/ags_timestamp_thread.h
/usr/include/ags/thread/ags_worker_thread.h
/usr/include/ags/thread/file/
/usr/include/ags/thread/file/ags_thread_file_xml.h
/usr/include/ags/thread/file/ags_thread_xml_serialization_factory.h