The Prompt I Use To Untangle useEffect

When an effect misbehaves, the instinct is to paste it and ask "why does this run twice". You get an answer about StrictMode and you are no wiser.

Better prompt:

"For each effect in this component, tell me: what external system it synchronises with, what its cleanup should be, and whether it could be derived state or an event handler instead. Then rewrite only the ones that are genuinely effects."

The framing does the work. Most effects in a struggling component are not effects — they are derived values that got written as effects, and the rewrite deletes them rather than fixing them.

I ran this over a 400-line dashboard component. Six effects went to two, and the double-render bug disappeared on its own because the offending effect no longer existed.