Build Your First AI Web App: A Reading-List Project

Choose one stateful action

A web app does something with input or state: a tracker saves entries, a booking tool records a request, a dashboard reads data. Your first version should make one of those actions reliable before you add several more.

This guide uses a personal reading list as an example. Version one adds a book, marks it finished and preserves the list in the same browser. It does not have shared accounts, payments or an external catalog integration.

1. Decide where the data belongs

Requirement	A possible starting point	What to check
A disposable demonstration	In-memory sample data	Explain that refresh resets it
A personal list on one browser	Browser storage	Check persistence, storage failure and clear-data behavior
A list shared across devices	Backend storage with identity	Check login, record ownership and network failures
Several roles sharing private records	Backend with explicit permissions	Test each allowed and denied action separately

Browser localStorage is scoped to an origin and persists across sessions, but it is not cross-device synchronization or a secure place for server secrets. MDN documents its behavior and limitations. Choose it only when those limits match the feature.

2. Give the agent an observable contract

Build a reading-list app with add, mark-finished and remove actions.
For version one, use this browser's storage; no accounts or backend.
Each item needs an id, title and finished state.
Reject an empty title. Explain what happens if storage is unavailable.
Show useful empty and error states.
Before editing, propose the file changes and acceptance checks.

The contract does not need to dictate every line of code. It should make essential product decisions explicit. Use the one-feature template when your idea has more requirements than fit in the prompt.

3. Build one vertical slice

Start with “add a book and see it in the list.” Then check what happens after refresh. Once that works, add mark-finished and remove. This sequence connects interface, behavior and storage for one action before expanding the rest.

Avoid building a polished dashboard around unverified storage. A realistic loading animation does not prove a request succeeded. If a write fails, the interface needs to tell the user what was and was not saved.

4. Use a small test matrix

For the reading list, check:

• Empty input creates no item and shows a useful message.
• Adding two books produces two distinct records.
• Marking one book finished does not change the other.
• Refresh preserves the intended state.
• Removing a book removes the intended record only.
• A storage failure does not show false success.
• A narrow screen still allows every action.

Run the existing project checks and repeat the main interaction in the browser. Record the result rather than relying solely on the agent’s completion message.

5. Add accounts as a separate feature

Moving from one browser to several users changes the data model and permissions. A hidden button is not access control. Your backend needs to decide which records a request may read or change.

If you use Supabase, read its official Row Level Security guide and test policies with two sample users. If you use another backend, find its equivalent authorization mechanism. Do not remove permission checks to make a failed request appear successful.

Use sample data while developing. Secrets that authorize a server integration belong on the server, not in frontend code or a public repository. The security lesson path introduces the risks to recognize.

6. Publish a checked version

Follow the host’s current deployment steps, then test the public URL. Check the initial load, the main action and persistence there. Keep the working checkpoint and know how to restore it if the release fails.

For a concrete first-party example, VibeGym’s architecture and newsletter case study shows how a public interface connects to API and database states. It also explains which checks were run and which conclusions they cannot establish.

If something breaks, gather evidence with the debugging workflow. If the project keeps growing, return to the scope guide. You have a useful first app when one real action works and you can explain how you verified it.

Sources checked 2026-10-03

• Bolt introduction — checked 2026-10-03.

• Supabase row-level security — checked 2026-10-03.

• MDN website security — checked 2026-10-03.

• behavior and limitations — checked 2026-10-03.