The vim purist and the browser tab share one tmux

You live in SSH and tmux and you're not changing. Your teammate has a browser and a meeting in four minutes.

Web terminal sessions map to tmux sessions: the terminal-3 URL is tmux session 3. She opens the URL; you run tmux attach -t 3 from your own client. You're both in the same session: same scrollback, same vim buffer, same half-typed command. She points at the bug by typing; you see her keystrokes land in your terminal emulator, and yours land in her tab.

Nobody screen-shared. Nobody installed anything. Nobody compromised on their setup.

Same session, two doors: one is SSH, one is a URL.