It's not so straight-forward. Either you must add hooks the the agent to notify tmux directly or you must use an external tool that polls tmux to determine one of its panes has gone silent and then based on that, send notification to tmux.

The poling requires tmux (not screen nor dtach, as far as I could find). And, silence for N seconds is just that, the poll doesn't know if that really means waiting for input or something else. With agents (like claude) that have a throbber/spinner going while "thinking", silence is a good indicator.

Kitty terminal can be polled for current text and then see if that has changed in N seconds. This would allow not having to depend on tmux which may be preferable to some kitty users. Generally, using tmux always surfaces some annoying problems for me.

Someone else suggested the bell character. But you can also just set tmux pane names or color. Which you can also do from your agent harnass.

You can achieve this with features that Tmux already have. Glued a tool that works:

https://gist.github.com/Enoch2090/5026c417f86ff6ff4fbe30c22b...

You use an agentic harness which terminates with bell character[0]. This lights up tmux, clearly indicating that it's done.

[0]: https://en.wikipedia.org/wiki/Bell_character