先说结论

If you mostly know AI through ChatGPT-style tools and you're trying to build your first real product, the easy mistake is thinking “full stack” means “set up a pile of backend services first.”

That mistake is expensive. You can burn time, budget, and attention on infrastructure before you prove the product.

Picture the moment: you see another AI stack post, almost scroll past it, then stop because you do not want to fall behind. The useful question is not “Ask an AI expert: What exactly is the full stack?

” as a vague debate. The useful question is: what changes your next build decision?

为什么这次值得看

My answer for a first version: about 80% of the full stack is usually three files: route.ts, actions.ts, and policy.sql.

route.ts is the request entry. In Next.js, route handlers already use the standard Web Request/Response API, so you do not need a giant backend just to receive and shape calls [S001].

actions.ts is the trusted write path. Next.js Server Actions let the client trigger server-side mutations over the network, which covers a lot of first-version behavior without another service layer [S002].

policy.sql is the part people underweight: the permission boundary. Supabase is blunt here. Browser access is only safe when row-level security is on, and without a policy, even a public key cannot read the table [S004].

关键证据

That is the whole point of the three-file frame. When someone asks, “Ask an AI expert: What exactly is the full stack?”, my first-version answer is still the same: route.ts, actions.ts, policy.sql.

Not forever. Not for queues, analytics, billing, or multi-region ops. But often enough for v1.

A post is only worth your time if it changes your next build decision. If someone around you is overbuilding their first AI app, share this with them.

Which of the three is still missing in your stack: route.ts, actions.ts, or policy.sql?

#AIEngineering #FullStack #Nextjs #Supabase

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