The Trap of Vibe Coding useCallback

Series: How React Works Under the Hood

Part 1: Motivation Behind React Fiber: Time Slicing & Suspense

Part 2: Why React Had to Build Its Own Execution Engine

Part 3: How React Finds What Actually Changed

Part 4: The Idea That Makes Suspense Possible

Part 5: The React Lifecycle From the Inside

Part 6: How State Actually Works

Prerequisites: Read Parts 1–6 first — especially Parts 3 and 6.

Where We Left Off

In Part 6 we saw how useState works — state stored on the Fiber as a hook object, updates queued and processed on the next render, the component function running fresh from the top every time. Every render. From the top.

That last part is what this article is about. Because every render from the top means every value inside the component is recreated. And that single fact is the root cause of most React performance problems — and the reason the most common advice for fixing them often makes things worse.

You Wrapped Everything in useCallback .…