tmux/Status Line/Q/Why does my status-right repeat the same session name instead of listing every session?

• Why does my tmux status-right repeat the same tmux/session name instead of listing every session?

  • AI Answer

    • Short answer: The right side is not showing four sessions — it is showing one session's name four times, once per live session. The global status-right shells out to tmux list-sessions -F '…' inside #(), and tmux expands #{…} across the whole format string before handing the command to /bin/sh. The -F template therefore reaches list-sessions already collapsed to the attached client's own session, and list-sessions prints that identical string once for every session it finds.

    • What the option actually holds

      • sh

        tmux show-options -g status-right
        # status-right "#(tmux list-sessions -F '#{?session_attached,[,}#{session_name}#{?session_attached,],}' | paste -sd' ' -) "

    • The order of operations

      • status-format[0] draws the option through #{T;=/#{status-right-length}:status-right}, so the option's contents are expanded as a format.
      • That expansion walks the entire string, the text inside #(…) included. #{session_name} becomes the session of the client drawing the status line, and both #{?session_attached,[,} and #{?session_attached,],} resolve for that same session — which is where the brackets come from.
      • Only then does /bin/sh run what survives: tmux list-sessions -F '[ls-encode-garden]' | paste -sd' ' -.
      • list-sessions emits its -F template once per session, so four sessions produce four identical bracketed names. The number of copies equals tmux list-sessions | wc -l; kill a session and one copy disappears.

    • Why it started

      • Nothing in ~/.config/tmux/tmux.conf sets status-left or status-right — that file only sets terminal features, passthrough, and update-environment. No theme, no plugin manager, no set -ag line, and no config reload appending to the option.
      • The options were written at runtime with tmux set -g … by an ad hoc layout script that stood up an agent workstream for a different repository on this same tmux server. set -g is server-global, so every session on the server inherits it, including sessions started later for unrelated work.
      • That script's other fingerprints are still on the server: status-left opens with its two-letter project tag, and set-titles-string still names the other project. ~/.config/tmux/tmux.conf never reverts them, because unset-at-runtime options only return on a new server or an explicit unset.

    • Three ways to fix it

      • Escape the inner hashes so the shell receives the template rather than its expansion — ## expands to a literal #:
      • sh

        tmux set -g status-right "#(tmux list-sessions -F '##{?session_attached,[,}##{session_name}##{?session_attached,],}' | paste -sd' ' -) "

      • Drop the subshell. The S: modifier loops a format over every session — no shell, no once-a-second job throttle, no escaping puzzle:
      • sh

        tmux set -g status-right "#{S:#{?session_attached,[,}#{session_name}#{?session_attached,],} }"
        # → [attached-session] other-session third-session

      • Restore the defaults, since these globals were never in the config file:
      • sh

        tmux set -gu status-right
        tmux set -gu status-left

      • set -gu unsets the option back to tmux's built-in default: status-left returns to [#{session_name}] , status-right to the truncated pane title plus clock.

    • Verified locally

      • On tmux/v/3.7b, a throwaway server (tmux -L fmttest) with three sessions and status-right set to #(tmux list-sessions -F '#{session_name}' | paste -sd, -) wrote one,one,one. The same command with ##{session_name} wrote one,three,two. The #{S:…} form rendered [one] two three.

    • Sources

      • tmux(1) man page — FORMATS — ## is replaced by a single #; S: loops a format over each session; #() inserts the last line of a shell command's output; #{l:…} marks a string as literal so it is not expanded.