Here is how to build an app with AI: write a five-line brief, turn it into one prompt that names the screens and the rules, test the preview with numbers you can check in your head, then fix one thing per message until it behaves. When it does, press Put it online. You do not need to code, but you do need to be exact. Below is a real example, a shared expenses app for flatmates, built prompt by prompt in VibeDream, with the places it usually goes wrong.
What AI can and cannot do here
- It can turn a clear description into a working app with screens, forms and a backend that saves data. On VibeDream that means a React frontend and a FastAPI backend.
- It can fix its own errors when you paste them back, restyle anything, and add features one at a time.
- It cannot guess facts it was not told, such as your rules for splitting bills. Missing details get filled with plausible guesses.
- It does not replace testing. You have to click every button and try the odd cases, like a bill split between two people instead of three.
- It will not make your decisions for you. Every rule you leave out becomes a guess.
This style of building, describing what you want and steering by how the result behaves, is often called vibe coding. The idea and its limits are explained in what is vibe coding.
Write the brief
Before you open the builder, answer five questions in a note. Who uses it? What is the one job? What screens? What data is saved? What are the rules? For the flatmates app:
- Who: three to five people sharing a flat, all on their phones.
- Job: record shared costs and show who owes whom, so nobody keeps a spreadsheet.
- Screens: Balances, Add expense, History, Flatmates.
- Data: flatmates (name), expenses (what, amount, who paid, date, who it is split between).
- Rules: split equally between the people ticked; balances net out so each person sees one number; settling up records a payment.
First prompt and first preview
Turn the brief into one message. Put the rules in plain sentences. Name the screens. Say how it should feel. In VibeDream, tap New Project, choose Direct Prompt and paste it, or press the microphone and say it.
If you would rather not start from an empty project, the Blank Starter template gives you a React frontend and a FastAPI backend that already talk to each other, and you paste the same prompt into it.
Build a shared expenses web app for flatmates. Screens: Balances (each person and one net number, green if they are owed, red if they owe), Add expense (what, amount, who paid, date, tick who it is split between, default everyone), History (newest first, tap to edit or delete), Flatmates (add or rename people). Split equally between the ticked people. Add a Settle up button that records a payment from one person to another. Clean, friendly, phone first, big buttons. Save all data so it is there next time.The preview appears beside the chat within seconds and fills in as the AI builds. When it stops, test it with numbers you can check in your head. Add three flatmates. Alex pays 60 for groceries split three ways. Sam pays 30 for internet split between Sam and Jo. Balances should show Alex owed 40, Sam owing 5 and Jo owing 35, which adds up to zero. If any number is wrong, you have found your first fix.
Five follow-up prompts that matter
Almost every app needs the same kinds of corrections after the first preview. Send them one at a time and check each before the next.
- Fix logic with an example. The balances are wrong. With Alex paying 60 split three ways and Sam paying 30 split between Sam and Jo, Jo should owe 35. Fix the calculation and show me the steps on the Balances screen when I tap a name.
- Handle the edge cases. If someone is removed from Flatmates, keep their past expenses in History and show them as former flatmates.
- Tighten the layout. On phones, make Add expense a big button fixed at the bottom of the screen.
- Fix the words. Rename Settle up to Pay back and show a confirmation like Sam paid Alex 10.
- Polish one thing. Show amounts with the pound sign and two decimals everywhere.
Quoting a worked example, as in the first fix above, is the most reliable way to correct logic. The AI can check its work against your numbers. When an error message appears, copy it into the chat and ask for a fix rather than describing it from memory.
Data and login
Your app's FastAPI backend is where saved data lives, so reload the page after adding an expense and confirm it is still there. If you want each flatmate to have an account, ask: add a simple login so each flatmate signs in with their email. The AI writes it into your app. You can also tap Add login or Add database under the chat. For a flat, a shared passcode on the first screen is often enough to start.
Keep secret keys, such as an email provider key for reminders, out of the chat and out of the code. Add them in project settings. The API keys guide explains which names stay on the server.
Publishing
Tap Put it online, choose a name, and the app goes live at an address like flat-money.vibedreams.ai with HTTPS, usually in one to three minutes. Share that link in your group chat. Each publish costs 5 credits, and the live version only changes when you press Update it, so you can keep experimenting in the preview without breaking what your flatmates are using. You can also connect your own domain with a TXT and a CNAME record; the deployment guide walks through it.
Want the code? Open the Code tab to read every file, use Export to download a ZIP, or connect GitHub to sync it to your own repository.
Keep a running spec
As the app grows past ten or twenty prompts, it is easy to forget what you decided. Keep a short note of the rules and anything you told the AI never to change, and update it as you go. When a later change breaks an earlier rule, paste the relevant line back in: remember, balances must always add up to zero. You can even ask the AI to write the current rules into a readme file in the project, so the spec lives next to the code.
Costs
All Access Mini is $49 a month with 60 credits and up to 3 active projects. All Access is $97 a month with 150 credits and up to 5 active projects. Credits go on messages, and bigger changes use more, so clear single-purpose prompts stretch further. Putting it online or updating it is 5 credits, and hosting is included. Current plans are on the pricing page.
For the bigger decisions around an app, such as web or native, how to scope it and how to test with real users, read how to build an app. If your tool is for a team at work, build internal tools with AI covers the extra questions around logins and existing data.