Why Your AI-Built App Breaks When Real Users Sign Up

Most AI-built apps break at signup because they were only ever tested on the happy path: one builder, one device, one clean account. Real users bring typos, slow networks, old phones and half-finished flows, and the app has no plan for any of them.

Why does the app work for you but not for your users?#

It works for you because you are the one person it was built around. You wrote the prompts, you know which button to press next, and you test with data you chose. The AI tool produced a main path that holds up under exactly those conditions.

Real users do not behave like that. They sign up with an email that is already registered. They paste a password with a trailing space. They close the tab halfway through and come back an hour later. They open the link on a phone with a weak connection. Each of those is a different path through the code, and AI-generated code tends to be thinner on the unglamorous paths around the main one.

The first time a third-party service times out, the user sees a blank screen and the founder sees nothing at all.

What goes wrong most often at signup?#

From hands-on work opening up apps built this way, the same problems keep appearing:

• Signup and login that fail quietly, with no error shown to the user.
• Authentication that was added but never checked for edge cases.
• API keys placed in front-end code where anyone can read them.
• Old code left behind when the AI added new code, so nobody knows which version is live.
• Pages that look fine on one screen and break on others, or that are slow because of large files.

The founder usually sees the symptoms rather than the causes: signups failing, a site that loads slowly, a layout that looks wrong on some devices, and no way to tell what went wrong once real traffic arrives.

Is the login itself safe?#

Not automatically. The OWASP list of common web weaknesses has a whole category for authentication failures. It includes weak or default passwords, missing multi-factor authentication, weak account recovery, and sessions that are not ended properly at logout or timeout. Its prevention advice includes throttling repeated failed logins and giving the same response whether or not an account exists, so attackers cannot use your signup form to find out who is registered. Read the full list in the OWASP guidance on authentication failures.

In the apps we have opened, failed authentication has been a recurring finding. A generated login form often covers enough to let you in, and not much more.

What about the database behind the signup?#

Some AI app builders connect to a hosted database such as Supabase. According to a Supabase security guide from Bastion, a table without Row Level Security lets anyone holding the public key read and write every row through the automatic API. The same guide says the service role key bypasses those protections entirely and must never appear in front-end code.

This is not a theoretical worry. The Next Web reported that a flaw in the AI app platform Lovable left source code, database credentials and user records exposed for 48 days after a researcher reported it. That was a platform-level flaw, not something a founder caused. It shows why "the AI built it" is not the same as "it has been checked".

What can a founder check without reading code?#

Walk through the app the way a stranger would. Sign up with a new email, then try the same email again. Reset a password. Use the app on a phone you do not normally use, on mobile data instead of Wi-Fi. Then ask someone who has never seen it to do the same while you watch without helping.

If any of these fail, the problem is real even when the cause is hidden.

What should you ask your developer?#

Ask where the secret keys are stored and which of them are visible in the browser. Ask how failed logins are handled and what happens when an outside service is down. Ask what is running in production and whether any old code is still deployed. A clear answer to each is a good sign. A vague one is a reason to look closer.

If you want a wider view of the common failure points, our guides on AI-built apps go through them one by one, and the services page explains how we approach fixing them.

Where should you start?#

Fix what users hit first: signup, login, and anything that handles money or personal data. Then look at speed and phone layouts. If you are not sure where your business stands overall, the free Digital Maturity Calculator can show which area deserves attention before you spend on fixes.