You're right that vanilla tmux can do all of this, if a human were to use it. tmux-cli exists because LLMs frequently make mistakes with raw tmux: forgetting the Enter key, not adding delays between text and Enter (causing race conditions with fast CLI apps), or incorrect escaping.
It bakes in defaults that address these: Enter is sent automatically with a 1-second delay (configurable), pane targeting accepts simple numbers instead of session:window.pane, and there's built-in wait_idle to detect when a CLI is ready for input. Basically a wrapper that eliminates the common failure modes I kept hitting when having Claude Code interact with other terminal sessions.
It bakes in defaults that address these: Enter is sent automatically with a 1-second delay (configurable), pane targeting accepts simple numbers instead of session:window.pane, and there's built-in wait_idle to detect when a CLI is ready for input. Basically a wrapper that eliminates the common failure modes I kept hitting when having Claude Code interact with other terminal sessions.