wmii[0], it implements the acme window layout. But the interesting part is that it exposes its state as a file-system. The main loop is a shell script[1]. So BYO posible, fe here is a Ruby one [2]

[0]: https://github.com/0intro/wmii [1]: https://github.com/0intro/wmii/blob/main/cmd/wmii.rc.rc [2]: https://github.com/sunaku/wmiirc