How AppCub Turns a Chat Into a Working Android App

When you use AppCub, you type a few lines and a few minutes later an app is running next to the chat. This post explains what happens in between, and the rules we built AppCub around.

1. A plan before any code

AppCub does not start coding from your first message. A planning step reads what you wrote and decides whether anything essential is missing. If it is, AppCub asks, with tap-able answers, and asks no more than three questions in total. An app for a tiffin service does not need an interview.

Then it writes a plan: the screens, the features, the data the app saves, what is deliberately left out of the first version, and the build steps. You approve it, or reply with changes like "drop the calendar, add attendance".

We made planning a separate step because the most expensive mistake is building the wrong app. A plan is cheap to read and cheap to change. Code is not.

2. A starting project, not a blank page

Once you approve the plan, AppCub creates your app from a starter project written in Flutter, Google's framework for building apps. Your app's name, package name and colour are filled in, and the build settings are already correct for Android. The AI then writes your screens and features into that project.

AppCub can only write to the parts of the project that hold your app's own code, tests and pictures. The build configuration and the signing setup are managed by AppCub, not by the AI. A new package can only be added if it is on a list of long-used packages, or comes from a verified publisher on pub.dev, Flutter's package site, and has not been discontinued. This keeps a generated app from quietly pulling in code nobody checked.

3. The app has to build before it counts as done

This is the rule we care about most. While AppCub is writing code, it runs Flutter's own analyzer on the project. The job is not allowed to finish while the analyzer reports errors. If the coding step cannot fix them itself after two attempts, the problem is handed to a stronger model whose only job is to fix it.

AppCub also runs the app's tests. Tests are the one step that executes AI-written code, so they run in a sandbox: they can see only their own project, cannot reach the internet, and cannot see our servers, other people's projects or any keys.

When the code passes, AppCub formats it, saves a version and builds the live preview you see in the phone frame.

4. Every change is a version you can go back to

Each finished change is saved as a version. If a change makes the app worse, you restore the earlier one from the Activity tab.

If a change goes wrong in a way AppCub cannot fix, for example it runs out of steps or you press Stop, AppCub keeps the work only if the app still builds. Otherwise it goes back to the last version that did. The result is that the app in your preview always builds.

This is also why work that fails or is rolled back costs no credits. You pay for changes that work, and after every change you get one free fix if something was built wrong.

5. You can see the work

The Activity tab lists every step in plain language: which files were read, what was written, which checks ran and what was fixed. The Code tab shows every file. You do not need to read either, but they are there, and the code is yours to download and use without AppCub.

6. The Android build

When you want the app on a phone, AppCub produces a signed APK that you install by scanning a QR code. On paid plans it also produces the Play Store bundle (AAB) with a signing key made for your app, so every update you publish carries the same key.

Release builds do not run on the server that talks to the AI. They run on separate build machines, so the server that holds the signing keys never runs a build itself.

7. Credits follow the work

AppCub uses Google's Gemini models through Google Cloud Vertex AI. Under Google Cloud's terms your project is not used to train Google's models, and we do not use it to train models either.

A credit is a fixed amount of that AI work. AppCub charges for what a job actually used, so a colour change costs a few credits and a new app usually 60 to 110. Each run also has a limit: if it gets close, AppCub is told to wrap up, and if it reaches it, AppCub stops, keeps the work that builds and waits for you to say "continue". A single request cannot run away with your credits.

The current prices are on the AppCub pricing page.

What this does not solve

A working build is not the same as a correct app. The analyzer catches broken code, not a fee calculated the wrong way or a button that sends an order to the wrong number. Try the app the way your customers will, on your own phone, before you share it. AI-generated code can contain mistakes, and you are the publisher of the apps you make.

Try it

Describe the app you have in mind at appcub.ai. The plan is free, so you can see what AppCub understood before anything is built. If you run a business and are building your first app, start with how to make an Android app for your business without coding.