You are missing out a bit, but stay content. :)

Multiplexers have a lot of little papercuts and limitations when you want consistent and native-to-the-OS behavior to flow all the way between the OS and the apps and connections in the multiplexers. For example, gesture scrolling in a tmux/zellij pane is hard because the right events don't flow through. It's an itch to scratch like designing a good terminal lib (like ghostty.)

And then, there's all the unifying and smoothing out of data connections--I imagine they'll be a lot to make sure that, e.g., an ssh session or a Claude code session in a pane can be seamlessly reconnected or never drop when the pane is closed. This takes a lot of hacking to make look seamless in most setups right now.

Like mitchell, I write a lot of software around multiplexers, and I've thought about making something similar, but I don't have quite the same level of personal wealth or angel investor connections. :)

herdr and mosh are a couple of reference points for this, there are others.