I created something similar, fully open source, using the ideas behind scrolling window managers. There's currently no website as I'm actively using it to work on a different project. It has features such as a shortcut (command+.) to open an overlay menu that allows you to switch to any split just by typing a letter and a number. Throughout the app. It also has optional vim bindings, support for different models and agents (e.g Claude, Codex, etc via ACP), and much more. There're bugs, but if you run into any, feel free to let AI create a PR. Goes without saying that it's vibe coded.

https://github.com/terhechte/Cormac