console -> tmux -> Emacs: Meta key problem

Hi,

I'm using OpenBSD 7.5 GENERIC.MP#82 amd64 with a PC keyboard of a US
layout. I'm using the console, and to have the Meta key work properly
with Emacs, I was advised on this list to configure Emacs with:

(set-input-mode t nil t)

The Emacs manual says that the above configuration makes Emacs expect
8bit characters where the Meta key is encoded by the 8th bit.

The problem is that when I run Emacs inside tmux, the Meta key
(specifically, M-x) is no longer working. As far as I can tell, tmux
does not bind to M-x. How could I get the Meta key back?


Best,
Irek