as far as I'm aware, there is some sort of protocol for looking at tmux state. iTerm has tmux integration, and will show tabs/splits as native (sub)windows.

https://iterm2.com/documentation-tmux-integration.html

https://github.com/tmux/tmux/wiki/Control-Mode

The downside is it doesn't work very well. Tmux tabs open as new iTerm windows instead of tabs, there are resizing bugs, etc.