When Pi Coding Agent is running on your computer: how to monitor it from your phone

Pi Coding Agent is one of those tools that’s happiest running on a “real” computer:

the repo is local
tools are local
long sessions are normal

And then you hit the usual desire:

I want to check in from my phone.

Not to do a whole refactor.

Just to:

see what it’s doing
see if it needs input
send one correction

This guide is the provider-specific workflow that makes that feel sane.

What I tried first (and where I bounced off)

SSH from phone
remote desktop
waiting
Happier: it gives you a phone UI to check progress, handle approvals, and send one follow-up. Trade-off: it still depends on the computer running the session being online.

If you’re new to Happier (what it is, and where to get it)

If you haven’t seen Happier before: it’s an open-source companion app (mobile/web/desktop) for coding sessions.

Get set up:

GitHub: https://github.com/happier-dev/happier
Install/download: https://github.com/happier-dev/happier#how-it-works
Discord: https://discord.gg/W6Pb8KuHfg

TL;DR

Install Pi (pi --version) on the computer that will run the session.
Pi auth is env-based (no interactive login flow).
If you’re using a system that supports connected credentials, pick a compatible profile (OpenAI Codex subscription OAuth, OpenAI API key, etc.).
If Pi isn’t detected, set HAPPIER_PI_PATH to the absolute path of the pi binary.
Use a phone-friendly session UI to monitor + approve + send follow-ups.

The problem

Pi is different from many providers because there isn’t a “log in” ceremony inside the app.

That’s not a bug.

It’s a credential model:

Pi reads supported credentials from environment-backed sources

So the phone workflow is not “log in from phone.”

It’s:

ensure the computer has the right credentials
then follow the session from your phone

Step 1: Install Pi Coding Agent

From provider docs:

npm install -g @mariozechner/pi-coding-agent
pi --version

Or via hstack:

hstack providers install pi
pi --version

(If you haven’t seen hstack before: it’s an optional helper in the Happier ecosystem that can install provider CLIs for you. You don’t need it — npm install -g ... is totally fine.)

Step 2: Auth model (env-only)

Pi is the clearest example of “credentials live on the computer, not in the chat UI.”

In source, Pi auth probing is marked as piEnvOnly.

That’s the behavior you should assume:

if the environment-backed credentials are present on that computer, Pi can run
if not, it can’t

A practical credentials checklist

On the computer that will run Pi:

Confirm pi --version works.
Decide which credential type you’re using:
- OpenAI Codex subscription OAuth (connected)
- OpenAI API key
- Anthropic API key
- Claude subscription setup-token profile (not OAuth)
Start one tiny session and confirm you can send a follow-up.

If that works once, your phone workflow becomes simple: monitor + approve + nudge.