Running Claude Code on Mobile with Happy Engineering

I’ve been using Claude Code a lot lately and wanted to be able to use it from my phone as well — not just from my desk. Here’s how I set it up.

Architecture

The whole system is made up of a few components connected over Tailscale, so there’s no port forwarding or public exposure involved:

┌─────────────────────────────────────────────────┐
│                   Tailscale                      │
│                                                  │
│  ┌──────────┐    ┌──────────┐    ┌──────────┐   │
│  │ Claude   │    │ Happy    │    │          │   │
│  │ Code VM  │◄──►│ Server   │◄──►│  Phone   │   │
│  │ (Zellij) │    │ VM       │    │  (Happy) │   │
│  └────▲─────┘    └──────────┘    └──────────┘   │
│       │                                          │
│       │ Mutagen sync                             │
│       │                                          │
│  ┌────▼─────┐                                    │
│  │   Mac    │                                    │
│  │ (editor) │                                    │
│  └──────────┘                                    │
└─────────────────────────────────────────────────┘

• Claude Code VM — runs Claude Code inside Zellij (like tmux but more user-friendly). Sessions persist, so I can disconnect and reconnect without losing context.
• Happy Server VM — runs happy-server-light, a lighter fork of the official happy-server that replaces Postgres with SQLite, drops Redis, and uses local file storage instead of S3. Much simpler to selfhost as a single instance. It didn’t build out of the box, so I forked it and made minimal fixes to get it running.
• Phone — Happy mobile app to interact with Claude Code. It connects to the selfhosted server and switches seamlessly between remote and local sessions. I can also use Termius to SSH directly into the Claude VM for full terminal access.
• Mac — Mutagen provides two-way file sync between the Claude VM and my local machine in real time, so I can review and edit code on desktop while Claude works in the VM.

How it works in practice

I can start a task on my phone via Happy, then pick it up on desktop — or the other way around. Happy handles the transition without any manual reconnection.

When I need full terminal access from my phone (to run bash commands or interact with Claude directly), I SSH into the Zellij session via Termius.

It’s a small setup but it makes Claude Code genuinely usable on the go.

Both the setup described here and this blog post were written with the help of Claude Code.