Codex anywhere with tmux, Mosh, Termius, and Tailscale

My current mobile Codex setup is deliberately simple: I use Termius on my phone to connect to my own laptop, then run Codex inside a tmux session. For a normal connection I use SSH; on a less reliable mobile network I use Mosh instead.

When I am at home, this is just SSH over my home Wi-Fi. When I am outside, I turn on Tailscale and use the same Termius profile against the laptop’s Tailscale address. The workflow stays the same:

Phone -> Termius -> Mosh or SSH -> laptop -> tmux -> Codex
            
          

Mosh makes the interactive connection more forgiving. It starts through SSH, then uses UDP so the terminal can survive short interruptions and roam between Wi-Fi and mobile data. On my Arch Linux laptop, the server is a small install:

sudo pacman -S mosh
            
          

I can then connect to the laptop by its Tailscale hostname or address:

mosh jiyu@my-laptop
            
          

Mosh does not replace tmux. Mosh keeps a shaky connection usable; tmux keeps Codex running when the terminal client is closed, the Mosh session eventually ends, or I want to reconnect from another device. That separation is the important part of the setup.

tmux new -s codex
            
          

Later, reconnect with:

tmux attach -t codex
            
          

I also tested remote control through the Codex app. The UI is better for phone use, but on Arch Linux it is not an official target for me, and the connection has been too slow and unreliable. A nicer UI does not help much when the session keeps dropping.

So I went back to the boring setup that works: Termius on the phone, Mosh or SSH for the terminal connection, Tailscale for private networking when I am away from home, and tmux as the durable shell on the laptop.

It is not elegant, but it gives me the thing I actually need: access to the same local development environment from anywhere, without pretending the phone is the development machine.