I'm experiencing some strange console pagination behaviour in tmux when SSH'd to a Ubuntu host (EC2 instance on AWS). I've demonstrated this behaviour by running irssi inside the tmux and hitting PgUp and PgDn.(I'm aware that normally one should hit Ctrl+B and then PgUp to go up through buffer pages in tmux, but this should work in irssi as it's a terminal application that takes over the buffer and the paging.)You can see that it seems to think the window/buffer is about half of its actual size and move it to the top or bottom of the actual space, if that makes sense.My $TERM is xterm-256color, $SHELL is /bin/bash, tty is /dev/pts/2 (for the moment at least, the pts number changes I think).tmux -V is now 2.3 as I've tried installing the latest master from source, I first experienced this behaviour with the tmux that is packaged in the regular Ubuntu repositories (which was version 2.1). My Ubuntu is 16.04.1 LTS.
Misbehaving irssi Pagination in tmux
ubuntu;terminal;tmux;tty;buffer
For what it's worth, tmux relies upon using the terminal capabilities in the screen terminal description.  Besides function-keys (which tmux does in a different way), here are a few of the differences which affect cursor movement (all features in xterm but not in screen), which you could see using infocmp xterm-256color screen:    hpa: '\E[%i%p1%dG', NULL.    indn: '\E[%p1%dS', NULL.    rin: '\E[%p1%dT', NULL.    vpa: '\E[%i%p1%dd', NULL.If you set TERM=screen, that tells most applications to use only the number of colors described therein (8). tmux would work with screen-256color about as well as your non-tmux xterm-256colorThere also are tmux and tmux-256color entries, but it is common for packagers to provide by default only a cut-down terminal database without these.  You might want to install the ncurses-term package as a start.