Codex on Android: build apps with your ChatGPT plan
The short version. AppMama runs OpenAI's Codex coding agent on your Android phone, together with everything needed to compile an Android app. Sign in with ChatGPT, say what you want, and Codex writes it while the phone builds and installs it.
Codex, without a computer
Codex is OpenAI's coding agent: it reads a project, writes code, runs commands and fixes its own mistakes. It normally runs in a terminal on a computer, or in the cloud where the result is code you still have to build somewhere. AppMama runs it locally on the phone, with a JDK, Gradle and Android build tools next to it, so its output is an app you can install right away.
How it works
- Install AppMama from Google Play and choose ChatGPT during setup.
- Sign in with your ChatGPT account, or paste an OpenAI API key.
- Describe the app. Codex works in a live terminal you can watch.
- When the APK is ready, tap to install it.
- Ask for changes in the same conversation and install the update.
Good to know
- Each app uses your ChatGPT allowance, the same as a long Codex session would.
- Pick the model: a quick one for small fixes, a stronger one for a new app.
- Your sign-in is stored encrypted on the phone and used only to talk to OpenAI.
- Prefer Claude? See Claude Code on Android. Curious how the build works? Build an APK on your phone.
Questions
Can I run OpenAI Codex on Android?
Yes. AppMama runs the Codex agent inside the app, with everything it needs already installed. Sign in with your ChatGPT plan or use an OpenAI API key.
Does it use my ChatGPT Plus or Pro subscription?
Yes. You sign in to your own ChatGPT account, so the work counts against your plan, just as Codex does on a computer.
What can Codex build on my phone?
Real Android apps: trackers, tools, calculators and small games. Codex writes the project and the phone builds and installs it.