GitHub Copilot Stores Derived State in useEffect. This Is Why That Breaks Your App.

There is a pattern that shows up in almost every React project where AI was involved. It looks harmless. It works on first glance. And it silently creates bugs that are annoying to track down. It looks like this: const [total, setTotal] = useState(0) useEffect(() => { setTotal(items.reduce((sum, i) => sum + i.price, 0)) }, [items]) GitHub Copilot writes this confidently. No warnings. No errors. Just broken logic waiting to happen. What is actually wrong here Total is not s