tmux/Q/What expands every item in tree mode, and why does Cmd-plus resize the Ghostty font instead?

• What expands every item in tmux tree mode, and why does Cmd-plus resize the Ghostty font instead?

  • AI Answer

    • Short answer: tmux/Mode/Tree binds expand-all to M-+, and M- is Key/Meta — on macOS that is ⌥, never ⌘. ⌘+ is Ghostty's own font-size binding and is swallowed before tmux can see it. Even the right keystroke only opens the tree as deep as it was built, so after tmux/Prefix w it does nothing. Opening the tree with choose-tree -Z shows sessions, windows, and panes at once.

    • The keystroke that needs nothing configured

      • C-b : opens the tmux/Command/Prompt; type choose-tree -Z and press Enter.
      • With neither -s nor -w, tmux/Command/choose-tree builds the tree down to panes and starts every branch open, so there is nothing left to expand.
      • ⌥⇧= — ⌥ and the + key — is M-+ and does reach tmux, as long as the tree was opened with tmux/Prefix s.

    • Why ⌘+ never arrives

      • ghostty +list-keybinds reports keybind = super++=increase_font_size:1 and keybind = super+==increase_font_size:1. Ghostty acts on those itself and writes nothing to the pty, so tmux is never offered the keystroke.
      • ⌘ is not a terminal modifier at all — see Key/Mac/Command. Terminal programs receive Key/Control and Key/Meta, never Command.
      • Key/Meta on macOS is ⌥, and only when the terminal is told to send it that way. macos-option-as-alt = true in the Ghostty config makes ⌥⇧= send ESC then +, which tmux reads as M-+. Ghostty ships no built-in alt+ binding for + or =, so nothing intercepts it on the way through — unlike alt+arrow_left and alt+arrow_right, which do collide (see tmux/Keyshort/Pane/Resize Pane).

    • How far M-+ actually reaches

      • Tree opened with	What M-+ does
        choose-tree -Zs (tmux/Prefix s)	opens the sessions to show their windows; panes stay hidden
        choose-tree -Zw (tmux/Prefix w)	nothing — sessions are already open, and windows never open this way
        choose-tree -Z (no -s, no -w)	the tree is already fully open; M-- then M-+ restores it

      • Pressing M-+ again does not descend another level; the expansion is bounded by how the tree was built, not by how many times the key is pressed.
      • After tmux/Prefix w, panes are reached one window at a time with +, Key/Arrow/Right, or l.

    • The durable change

      • bind-key W choose-tree -Z in the tmux/Config puts a fully expanded tree on C-b W.
      • The tree-mode keys themselves cannot be rebound off Key/Meta: tmux list-keys -T choose-tree answers table choose-tree doesn't exist, and tmux/list-keys shows only the prefix, root, copy-mode, and copy-mode-vi tables. Tree-mode keys are compiled in.
      • No Ghostty change is called for. macos-option-as-alt = true is already delivering Key/Meta; unbinding super++ would cost font-size control and still would not help, because tmux is waiting on ⌥, not ⌘.

    • Where the key list comes from

      • C-h or F1 inside tree mode prints the table that tmux/session/Picker/Help mirrors, and tmux/man repeats it under choose-tree. Both list M-+ as Expand all without qualifying the depth.
    • Behaviour above is tmux/v/3.7b.