I almost shipped an AI-built app with writes open to every logged-in user

last week I was getting an AI-built client app ready to hand off. The UI looked fine: auth worked, uploads worked, and each account only showed its own records.

Then I called one API endpoint directly with a non-admin token. SELECT had an RLS policy; INSERT and UPDATE didnt. Any logged-in user could have written to someone else's records.

the generator built the happy path I described. It never had a reason to test the request without the UI.

I now create two test accounts, swap IDs in the requests I can find, and check each operation separately. I still miss things, which is the part that still bugs me.

i tried Enter on the next build because I wanted a stack I could inspect and export. It made the audit less awkward, but it didnt replace testing the boundary myself.

For people shipping AI-built apps to real users, what is the first permission test you run?