$PATH Pollution on NixOS

[CuboidRaptor]

Version Information:

• Linux NixOS 25.05 (Warbler) x86_64
• tmuxp 1.50.1
• tmux 3.5a
• Bash 5.2.37(1)-release

When loading tmuxp sessions, $PATH gets polluted with paths to python and tmuxp. For example, when I load a session, echo "$PATH" prints /nix/store/fqm9bqqlmaqqr02qbalm1bazp810qfiw-python3-3.12.9/bin:/nix/store/y2r9mrjwnjbj2mqai0949am04z6ckw4g-tmuxp-1.50.1/bin before my usual $PATH. These paths are where Nix stores tmuxp's binaries as well as the binaries for the version of python it uses.

This only happens when I load with tmuxp. Just using tmux new does not cause this bug. It also doesn't happen outside of tmux.
This happens with a completely blank tmux config that has nothing except for set-option -g default-shell /<...>/shellbin, where shellbin is a bash script I created that runs bash with --noprofile and --norc.
Essentially, a blank tmux and bash config.
This bug happens with both my custom tmuxp sessions and also the example on the README.md

Should be able to reproduce with tmuxp load mysession with ~/.tmuxp/mysession.yaml containing the example from the README.md with no bash/tmux config on NixOS

[CuboidRaptor]

My current incredibly scuffed solution:

#!/usr/bin/env bash

set -o pipefail

# run zsh in a blank login shell and set $PATH to that $PATH
# this basically sets $PATH to how it would be in a new login shell
# (it's a patch for tmuxp's weird behaviour)
# and also set $SHELL to login default cuz that's get screwed up too
defaultpath="$(env -i HOME="$HOME" zsh --login -c 'echo "$PATH"')" \
    && export PATH="$defaultpath" \
    && defaultshell="$(getent passwd "$USER" | awk -F: '{print $NF}')" \
    && export SHELL="$defaultshell" \
    && exec -a "zsh" zsh "$@" # set $0

It basically runs an extra login shell to get the correct $PATH and sets it to the correct value before invoking zsh. Using bash is probably similar. (It also gets the correct value of $SHELL because that breaks too for some reason) I just use this script as tmux default-shell instead of zsh.
However, this is really cursed and an actual solution would probably be nice.