tmux-config

When to load

• User asks to "set up tmux" / "configure tmux" / "fix tmux"
• Authoring a fresh ~/.tmux.conf or auditing one that misbehaves
• Reconciling a config across WSL2 (Windows clipboard), Linux server (xsel/wl-copy), or macOS (pbcopy)
• Choosing a prefix key, color mode, or copy/paste strategy

Decision ladder (pick before writing)

1. Prefix — Ctrl-a is the lazy default. Ctrl-b is tmux stock (awkward, home row left hand). Ctrl-c collides with SIGINT. Ctrl-\ is SIGQUIT. Stop arguing, take C-a unless user insists.
2. Color — tmux-256color + terminal-overrides ",*256col*:Tc" (Linux) or ",xterm-256color:RGB" (WSL). Both work, neither needs a vendor terminfo.
3. Shell — match the user's login shell. fish users: set -g default-shell /usr/bin/fish. Don't override — half the time the user has a .bashrc that exec fish and tmux's shell start fights with it.
4. Clipboard bridge — this is the only per-host difference. See references/clipboard-bridge.md.
5. Mouse + vi copy — almost always set -g mouse on + mode-keys vi. Trivial wins.
6. Status bar — bottom by default (matches tmux/literature). Only flip to top if user has an embedded terminal/IDE pattern that needs it.

Verification ritual (ponytail)

The tmux server I'm running inside is my own host. Killing it kills me. So:

# WRONG — wipes my own session
tmux kill-server

# RIGHT — verify in a fresh session, on the same server, then kill only that session
tmux new-session -d -s _vverify fish -l
tmux source-file ~/.tmux.conf
tmux display-message -p "prefix=[#{prefix}] mouse=[#{mouse}] shell=[#{default-shell}]"
tmux kill-session -t _vverify

-p prints to stdout (scriptable), the named session makes cleanup explicit. Never kill-server during verification.

If the user is on fish and you must check $? after a tmux command, use tmux display-message -p to embed the check inside tmux itself — fish won't see the $? and won't choke.

SSH + fish login shell (the recurring foot-gun)

When the remote user's login shell is fish and you run inline ssh user@host '...':

• ssh user@host 'echo $?' → fish expands $? to literal $? because the command string is passed as argv, then fish sees $? and errors: fish: $? is not the exit status. In fish, please use $status.
• Symptom: exit code 127, fish error in stderr, your command never ran.

Fixes (pick one):

• ssh user@host bash -c '...' — ssh then runs bash; bash handles $? correctly.
• ssh user@host /bin/sh <<'EOF' ... EOF — heredoc forces the remote interpreter to sh, bypassing login shell.
• Never use bare $? in a single-quoted remote command when remote shell is fish.

Diagnose: if a remote command fails with fish: $? is not the exit status, the cause is fish login shell expanding $?, not your command syntax.

Cross-host config variants

The WSL2 and Linux-server configs in references/wsl-tmux.conf and references/linux-server-tmux.conf differ in only two lines: the clipboard bridge (clip.exe vs xsel --clipboard) and one terminal-overrides flavor. Keep the rest identical so muscle memory survives ssh jumps.

Output style for the user

User wants the config to "just work" with a 1-3 line usage summary at the end, not a 500-word config dump. After deploying, print:

• The 5-7 most-used key bindings (prefix + key)
• One line of "skipped" for what was not done (status bar theme, powerline, etc.)
• A note if any active session needs manual prefix r to pick up changes

Skipped by default (ponytail)

• Powerline / Nerd Font status bar — adds a font dep, asks the user to install fonts. Only do it on explicit request.
• Plugin managers (tpm, catppuccin) — heavy, lazy default is stock tmux. Add when user asks.
• Custom key bindings beyond C-a, r, |, -, p — no guesswork.
• Per-window themes, icons in status bar — visual noise.