How to Use Codex on Your Phone for Free – A Step‑by‑Step Guide

Integration Overview

OpenAI merged Codex into the ChatGPT mobile app. The phone does not run the Codex engine; it only displays a control panel while the engine executes on a host machine (laptop, Mac mini, devbox, or remote environment). Both the Free and Go subscription plans provide access at no extra cost.

Only macOS desktop clients can be paired; Windows clients are not supported. The Codex CLI and IDE plugins are not included in the mobile pairing workflow.

Supported Interaction Features

View live state : The phone shows the live state of all task threads running on the connected machine.

Approve and release : When Codex pauses for confirmation, tapping the phone resumes execution.

See results : Screenshots, terminal output, diffs, and test results are pushed to the phone in real time.

Change direction : New commands or strategy adjustments can be issued from the phone.

Switch model : The underlying GPT model version can be changed directly from the phone.

Create new task : A new thread can be started from the phone without returning to the computer.

Setup Procedure

Upgrade mobile app : Update ChatGPT; the Codex icon appears in the top‑left corner.

Start Codex on desktop : Open the macOS Codex app, click Start in Settings, and grant permission.

Authorize on phone : Authorize the connection; subsequent connections can be re‑established from the same screen.

Complete connection : Desktop Settings → Connection shows the phone’s status; the phone displays the identical Codex view.

Install Ollama : curl -fsSL https://ollama.com/install.sh | sh Launch Codex via Ollama : ollama launch codex-app Select a model : Cloud models such as K2.6 require a subscription. The author used the free Gemma‑4 model, which has a weekly quota.

Switch model : Edit the Codex configuration file to replace the model identifier; the change takes effect without reconnecting the phone.

Undo Ollama configuration : Comment out the added lines in the config file to stop using Ollama.

Extend free usage : After a Plus subscription expires, waiting one week before renewal allows continued use of GPT‑5.5 for free.

Configuration Details

Changing the model is performed by modifying the config file referenced by Codex; the modification is reflected immediately on the phone without a new connection.

Commenting out the Ollama‑related entries in the same config file disables the Ollama backend.

Visual References