Auto-apply tmux layouts based on terminal config

You can trigger a tmux layout automatically based on which terminal config launched the session.

Set an env var in your alacritty config:

[env]
TMUX_LAYOUT = "dev"

Tell tmux to pull it from the shell environment in tmux.conf:

set-option -g update-environment "TMUX_LAYOUT"

Add hooks that source a layout file when the env var matches:

set-hook -g after-new-session 'if-shell "[ \"$TMUX_LAYOUT\" = \"dev\" ]" "source-file ~/.config/tmux/dev-layout.conf"'
set-hook -g after-new-window 'if-shell "[ \"$TMUX_LAYOUT\" = \"dev\" ]" "source-file ~/.config/tmux/dev-layout.conf"'

The layout file (dev-layout.conf) is just raw tmux commands — no session management needed since the hooks fire after the window already exists:

split-window -h -p 45 -c "#{pane_current_path}"
split-window -v -p 30 -c "#{pane_current_path}"
split-window -h -p 50 -c "#{pane_current_path}"
select-pane -t 0

-c "#{pane_current_path}" makes each pane inherit the working directory of the pane it split from. After tmux kill-server and a fresh launch, the env var is picked up and the layout applies automatically.