TOT//OS

Run your agents from your phone with Tailscale

4 min read#agents #networking #howto

Coding agents do their best work on a machine with your repos, your tools and your keys on it. That is usually a desktop at home or at the office. But agents also work in long stretches where you mostly need to look in: approve a step, answer a question, start the next job. You don’t need to sit at the desk for that.

What you want is a terminal on that machine, from your phone, from anywhere, without exposing anything to the internet. That takes about twenty minutes.

phoneSSH clientprivate key workstationsshd · keys onlyagent in tmux Tailscale (WireGuard), 100.x.y.z encrypted, device-to-device router: no open ports
The phone and the workstation join the same private network. SSH only listens there, and only accepts keys.

1. A private network: Tailscale

Tailscale builds an encrypted WireGuard network between your own devices. Install it on the workstation and on the phone, sign in with the same account, and each device gets a stable private address (100.x.y.z) and a name. It punches through NAT on its own, so no port forwarding on the router and no public IP. The free plan is plenty for one person.

On a Windows workstation, turn on Run unattended in the Tailscale menu. Otherwise the connection only comes up after someone logs in at the desk, which is exactly when you don’t need it.

2. An SSH server that only takes keys

Linux / macOS: sshd is usually there already; make sure it’s enabled.

Windows ships OpenSSH Server as an optional feature. In an admin PowerShell:

Add-WindowsCapability -Online -Name OpenSSH.Server~~~~0.0.1.0
Set-Service sshd -StartupType Automatic
Start-Service sshd
# land in PowerShell instead of cmd.exe
New-ItemProperty -Path "HKLM:\SOFTWARE\OpenSSH" -Name DefaultShell `
  -Value "C:\Program Files\PowerShell\7\pwsh.exe" -PropertyType String -Force

Then keys, not passwords:

  1. In the phone’s SSH app (Termius, Blink, JuiceSSH, anything), generate an ed25519 key and copy the public half.
  2. On the workstation, add it to ~/.ssh/authorized_keys. On Windows, if your account is an administrator, the file that counts is C:\ProgramData\ssh\administrators_authorized_keys, and it must be readable only by Administrators and SYSTEM, or sshd silently ignores it.
  3. In sshd_config, set PasswordAuthentication no and restart the service.

Connect from the phone to the workstation’s Tailscale name. That’s it.

3. A session that survives the tunnel

Mobile connections drop. If your agent is running in the SSH session itself, a dead zone kills the job. Run it inside tmux (Linux, macOS, or WSL on Windows):

tmux new -s agent        # start once, run the agent inside
# ...connection drops...
tmux attach -t agent     # back exactly where you were

Any terminal agent works this way: coding agents, your own scripts, a long build. The phone is just a window onto a session that keeps running at home.

4. Keep the machine awake

A workstation that goes to sleep after 30 minutes is not reachable. Set the power plan so it doesn’t sleep while plugged in, or at least allow wake on network. Check this before you rely on it from the other side of the country.

The bug that ate an evening

My setup showed “Connecting…” forever. Tailscale said both devices were online. Ping worked in one direction only. The Windows firewall rules were fine. The antivirus suite’s firewall service showed as stopped.

It was still the antivirus. Some security suites install kernel-level network filters that keep dropping inbound traffic on the Tailscale adapter even when their firewall component claims to be off. The way to see it is to stop guessing and count packets: do bytes arrive on the adapter or not? When they arrive and nothing answers, something between the adapter and sshd is eating them. Uninstalling the suite (Windows Defender is still there) fixed it instantly.

Why bother

Because agents change what “being at work” means. The expensive part of agent work is not the typing. It is being available for the thirty seconds of judgement it needs every twenty minutes. With a private network and a persistent session, those thirty seconds can happen on a train, in a waiting room, or on the couch.

Checklist

  • Tailscale on both devices, Run unattended on Windows
  • SSH server on, keys only, password login off
  • No ports open on the router: nothing listens on the public internet
  • Agent runs inside tmux
  • Workstation doesn’t sleep
  • Lose your phone? Remove it from the Tailscale admin console and delete its key from authorized_keys. Access is gone in seconds.
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