The Architecture (Client vs Server)

Directives ("use client", "use server")

The Shift: While popularized by Next.js, these are now core React specifications. They define the "boundary" between code that runs on the server (rendering HTML/database access) and code that runs in the browser (interactivity/state).

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Directives clearly separate server and client code, enabling better security and performance.

📚 Explanation

React 19's `"use client"` and `"use server"` directives clearly separate client and server code. Server actions can safely access databases and APIs, while client components handle interactivity. This architecture improves security and performance.