Back in the early days of the X Window System, X10 era, there was a window manager that tried to emulate the Andrew System’s original tiled window interface, which tiled windows based on constraint solving.
Andrew moved to a simpler layout algorithm and there is a later X window manager also called “Andrew somethingorother” that uses this simplified algorithm.
But the original X WM. I saw it on a tape, source and all, years ago, and now I can’t find it.
@lorddimwit do you mean Siemens RTL Window Manager?
Sadly no, though they is an important entry in the history of window management. :)
@lorddimwit I don't know any other early tiling wm, so I'm curious what you find. The X10R3 tape has xwm, xnwm and uwm (all overlapping): http://www.retro11.de/ouxr/43bsd/usr/src/new/X/