How to keep an agent running after you close the laptop

Pick the tool

Four tools do the job. For an agent you talk to, take tmux. For a script or a bot that nobody types into, take systemd.

Already use screen? The same idea, other keys: start with screen -S agent, detach with Ctrl+A then D, list with screen -ls, come back with screen -r agent. For a script with no keyboard, nohup ./agent.sh > agent.log 2>&1 & keeps it alive after SSH closes.

Steps

1. Install tmux

   On Ubuntu and Debian it is one package. Do this on the server, over SSH.

   $ sudo apt install -y tmux

2. Start a named session and run the agent in it

   The name lets you find the session later. Start your agent as usual inside it.

   $ tmux new -s agent
   $ cd your-project
   $ claude        # or codex, or your own script

3. Detach and close the laptop

   Press Ctrl+B, then D. tmux prints the session name and returns you to the shell. The agent keeps working. Close SSH and the laptop.

4. Come back and attach

   List the sessions if you forgot the name, then attach. You see the agent as it is now, with everything it did while you were away.

   $ ssh [email protected]
   $ tmux ls
   $ tmux attach -t agent

5. For a job that must outlive a reboot: write a service

   tmux dies with the server. A systemd service starts at boot and restarts the program when it crashes. Put it in /etc/systemd/system/agent.service, with the path to your program and your own user.

   [Unit]
   Description=My agent
   After=network-online.target
   
   [Service]
   User=dev
   WorkingDirectory=/home/dev/your-project
   EnvironmentFile=/home/dev/your-project/.env
   ExecStart=/usr/bin/node agent.js
   Restart=on-failure
   RestartSec=5
   
   [Install]
   WantedBy=multi-user.target

   Restart=on-failure restarts the program when it exits with an error. Restart=always restarts it in every case, even after a clean exit. Then switch it on and watch the log:

   $ sudo systemctl daemon-reload
   $ sudo systemctl enable --now agent
   $ systemctl status agent
   $ journalctl -u agent -f

6. Stop the connection from dropping while you are there

   A quiet SSH window can be cut by a router. Ask your laptop to send a keep-alive every minute. Add this to ~/.ssh/config on the laptop.

   Host *
       ServerAliveInterval 60

Check that it works

Run a command that leaves a trace, detach, close the SSH window and open a new one. If the trace keeps growing, the setup works.

$ tmux new -s test
$ while true; do date >> ~/alive.log; sleep 5; done
# Ctrl+B, then D. Close SSH. Connect again:
$ tail -3 ~/alive.log
$ tmux kill-session -t test

For the service, run sudo reboot, wait a minute and run systemctl status agent. It should say active (running).

What tmux does not do

• It does not survive a reboot of the server. A kernel update or a provider restart ends the session; a systemd service comes back by itself.
• It does not restart a crashed agent. It only keeps the window open, with the error on screen.
• It does not look after the server. A plain server stays on, and updates, disk space and restarts stay yours to handle.

Common problems