Restoring a session

sess open rebuilds the session window by window:

1. tmux new-session for the first window, in the first pane's saved working directory.
2. tmux split-window once per additional saved pane.
3. tmux select-layout with the exact layout string captured at save time, so the geometry matches precisely instead of an even/generic split.
4. If the snapshot has any persisted environment variables, export NAME=value is sent into every pane's shell first — each pane is a separate process, so a var exported in one pane never reaches the others on its own.
5. tmux send-keys to relaunch each pane's saved command — guarded with -- so a command that happens to start with - is never misread as a flag.

If a live tmux session with the target name already exists, sess refuses to restore over it and attaches instead (see open for the --force override).

Restoring relaunches commands from scratch — it does not preserve a process's internal memory state (variables loaded in a REPL, for example). See Limitations.

Attaching, for real

Handing control of the terminal back to tmux for an interactive attach needs the child process to inherit the real stdin/stdout/stderr, not have them captured into a pipe — sess uses Command::status() for this one call specifically (Command::output(), used everywhere else for its convenient error capture, would silently break interactive attach).