Summary

psmux currently allows users to start a new psmux session from within an active psmux session shell. This lack of nesting prevention leads to UI confusion.

Environment

OS: Windows 11 25H2 version 26200.7922

Terminal: Windows Terminal / Alacritty / Wezterm

Shell: PowerShell 7.5.4 / msys2 bash / nushell / busybox ash

psmux: release 0.4.5 install by scoop

What I expected

psmux should detect if it is already running in the current shell environment. If an active session is detected, it should prevent the launch of a nested session by default or provide a warning to the user.

What happened

Running the psmux command inside an existing session successfully spawns a new instance within the current window. Then that session cannot use shortcut, session program cannot exit.

Reproduction

1. Open a Windows terminal.
2. Start psmux: psmux
3. Inside the psmux session, run psmux again. Note that a second session starts inside the first one.

Suggested Fix (Reference to tmux)

A proven solution, as seen in tmux, is to export a unique environment variable $TMUX upon session initialization.

The logic would be:

1. When psmux starts, it checks for the existence of an environment variable like PSMUX.
2. If the variable exists, the application exits with an error message: sessions should not be nested.
3. If it does not exist, the application sets $PSMUX and proceeds to launch.

Impact

• Usability: Conflicting keybindings between nested layers.
• UI: Overlapping status bars or screen corruption.