I recently came across Divvy (https://mizage.com/divvy/), and since it's closed source and hasn't changed in years, I built a lightweight open source alternative with Claude Code.
Press a shortcut, a grid appears, drag across the cells you want and the window snaps there, following your drag live. Any region can be saved as a preset with its own shortcut. It is simple Swift, has no dependencies, and requires no network access.
Tested on macOS 26 Tahoe. Feedback from anyone on earlier macOS versions is very welcome.
It's useful to me as is, and maybe it will be useful to someone else. Enjoy!