Ask Claude to start your app · Build Your Card App

By the endClaude has created your app in your project folder with its first screen, and the development server is running in the Terminal pane.

Everything is in place: the plan, the rules, the tools, the backup. Now you ask for the app. One message does it. The message below gives Claude the whole picture, so read it once before you send it.

What you are asking for

Only the first screen: the main list from your plan, with two made-up sample entries so there is something to see. Nothing that saves, nothing that adds, no real data. Those come one at a time in Part 6.

Each message below already describes that screen for one kind of card app, with two made-up sample cards from the game your plan starts with. Pick the one for your kind of app. You can change any word before you send it, or later.

The message also asks Claude to match the version of Expo Go, the free app that shows your app on your phone. The reason: each version of Expo Go runs projects made for one Expo version only, so your project must match the Expo Go on your phone. Expo gets a new version every few months; the newest when this guide was checked was SDK 58, and the store copies of Expo Go can be a step behind.

Send the message

In your project's session in the Code tab:

Collection tracker (like Binder)

Copy for Claude

Let's start my app. Read my plan file (the .txt file ending in -plan in this folder) and CLAUDE.md first. Then create a new Expo app for iPhone and Android in this folder, following the plan. Before you create it, find out which Expo version the free Expo Go app currently in the App Store and on Google Play supports, and use exactly that version, so the app opens in Expo Go on my phone. Build only the first screen for now: my collection list, with two made-up sample cards from the game my plan starts with, each with a name, set, card number, condition like "Near Mint" and a plain sample price like "$12.00". A colored rectangle where each card's picture will go later. And a "Collection value" total at the top that adds up the sample prices. Nothing else yet. Explain each Allow question in one plain line before I answer it. When it's built, give me the command to start the app in the Terminal pane myself, so I can see the QR code, and then tell me exactly what to do on my phone, step by step. I'm a beginner.

Seller's app

Copy for Claude

Let's start my app. Read my plan file (the .txt file ending in -plan in this folder) and CLAUDE.md first. Then create a new Expo app for iPhone and Android in this folder, following the plan. Before you create it, find out which Expo version the free Expo Go app currently in the App Store and on Google Play supports, and use exactly that version, so the app opens in Expo Go on my phone. Build only the first screen for now: my stock list, with two made-up sample cards from the game my plan starts with, each with a name, set, card number, condition like "Near Mint", how many I have, and a plain sample asking price like "$12.00". A colored rectangle where each card's picture will go later. And a "Stock value" total at the top that adds up the asking prices times the quantities. No costs or profit on this screen. Nothing else yet. Explain each Allow question in one plain line before I answer it. When it's built, give me the command to start the app in the Terminal pane myself, so I can see the QR code, and then tell me exactly what to do on my phone, step by step. I'm a beginner.

Shop app

Copy for Claude

Let's start my app. Read my plan file (the .txt file ending in -plan in this folder) and CLAUDE.md first. Then create a new Expo app for iPhone and Android in this folder, following the plan. Before you create it, find out which Expo version the free Expo Go app currently in the App Store and on Google Play supports, and use exactly that version, so the app opens in Expo Go on my phone. Build only the first screen for now: the shop's stock list, with two made-up sample cards from the game my plan starts with, each with a name, set, card number, condition like "Near Mint", how many we have, and a plain sample price like "$12.00". A colored rectangle where each card's picture will go later. And a "Stock value" total at the top that adds up the prices times the quantities. Nothing else yet. Explain each Allow question in one plain line before I answer it. When it's built, give me the command to start the app in the Terminal pane myself, so I can see the QR code, and then tell me exactly what to do on my phone, step by step. I'm a beginner.

Paste the message and send it.

What happens next

Claude reads your plan and checks the Expo version. This takes a minute.
It asks to run the command that creates the app. Say yes. A few hundred files appear in your project folder; that is normal, and you never touch them.
It writes the first screen and asks to save each file. Say yes. The Changes pane count goes up.
It gives you a command, usually npx expo start, to run in the Terminal pane (Part 4, step 5).
You run it. After a moment the Terminal shows a big square QR code made of dots, with a few lines of text under it. That is the development server running. Leave it running, and leave that pane open.

On a Windows PC

The first time the server starts, Windows may show a box titled Windows Security Alert saying Windows Defender Firewall has blocked some features of Node.js. That is the firewall asking whether the server may talk to other devices on your network, which is exactly what the next step needs. Make sure Private networks is ticked, click Allow access, and click Yes if Windows asks to allow changes. If the box names something other than Node.js, click Cancel and ask Claude what it is.

The next step puts it on your phone. Don't close the Terminal pane, and don't quit the Claude app, or the server stops. You can shrink the pane by dragging its edge.

If something goes wrong

Claude made a new folder inside my project folder. Say: "Move everything up so the app is at the top level of this folder, next to my plan file." It can.

Claude asks which template or options to use. Say: "The default, for a beginner, on the Expo version that Expo Go supports."

The Terminal shows red text and no QR code. Copy the last few lines, or take a screenshot, and send it to Claude: "The start command failed. Here is what it says." It fixes it and gives you the command again.

On a PC, the Terminal says a file "cannot be loaded because running scripts is disabled on this system". PowerShell is refusing the helper that starts the server. Part 4, step 8's trouble box has the one-time fix; or tell Claude the exact words and it gives you the command.

On a PC, I clicked Cancel on the Windows Security Alert. The firewall now blocks the server, and the phone won't connect in the next step. Ask Claude: "I blocked Node.js in the Windows firewall by mistake. Walk me through allowing it on private networks." The setting lives in Windows Security, under Firewall & network protection, then Allow an app through firewall.

I hit the usage limit in the middle. Wait for the time shown, then send: "Let's continue where we left off." Your files are safe.

I ran the start command and the QR code is tiny or cut off. Drag the pane's edge to make it bigger. Zoom isn't needed; the next step scans it from the screen.