tmux built with sixel support not working as expected in wsltty

[a-priestley]

I don't know if this is an issue with tmux, or wsltty, but I've gathered some curious results on different combinations of terminal emulators, with / without tmux:

foot run with wslg, no tmux:

wsltty, no tmux:

foot run with wslg, tmux:

wsltty, tmux:

It seems that the addition of tmux to wsltty is preventing sixel support. I have wsltty installed via scoop, with the following configuration:

# To use common configuration in %APPDATA%\mintty, simply remove this file
Scrollbar=none
Font=FiraCode Nerd Font
Term=xterm-256color
FontHeight=14
CtrlShiftShortcuts=yes
CursorType=block