Your app runs, but right now it forgets everything the instant you refresh, and anyone can use it. This lesson fixes both, and it is the part most people assume they need to hire an engineer for. They do not.

Recall the mental model: data is your app's memory, and auth is its gatekeeper. Everything a real product needs to remember (accounts, entries, history) lives in the data layer, and everything about who is allowed in lives in auth. In a traditional build these are serious pieces of engineering. In Lovable, you get them by asking. Since late 2025 Lovable provisions a real database and a real login system for you from inside the build; it runs on Supabase underneath, but you direct it entirely through Lovable, which is why setup told you not to make a separate Supabase account.

So you will add both live, by describing them. Something as plain as "add email and password sign-up and login, and store each user's entries so they see their own when they log back in" is enough for Lovable to stand up authentication and a database and wire your app to them. Watch what that gives you: a signup screen, a login screen, and, crucially, persistence. You will add one entry, refresh the page, and see it still there. That refresh test is the whole point of this lesson. When your data survives a refresh and each user sees only their own, you have a genuine full-stack product.

It helps to know one true thing about what is happening underneath, so you can reason about it when it misbehaves. Auth and data are connected: the login system tells your app who the current user is, and the database uses that identity to decide which records to show them. That link ("this data belongs to this user") is what keeps one person from seeing another's entries. You will not configure the internals by hand, but understanding that the connection exists is what lets you spot, and describe, a problem when someone can see data they should not.

By the end of this lesson your capstone remembers its users and keeps them separate. The only thing left for Week 1 is to get it onto the internet.