Hydra might be worth a look. The daemon owns the various agent processes (any that speaks ACP), and everything else is a client of open interfaces: a REST API for managing sessions, and ACP over a WebSocket for attaching to a live one. The TUI, a browser UI and VS Code all use those. So you can script it with plain HTTP instead of tmux. It doesn't use ssh; remote access is TLS. The TUI shows one session at a time, and ^P jumps between them.

https://github.com/smagnuso/hydra-acp