useMemo is really nice for sync effects but it breaks hot reload because hot reload does not call useMemo again. E.g. you can subscribe to something using useMe

useMemo is really nice for sync effects but it breaks hot reload because hot reload does not call useMemo again. E.g. you can subscribe to something using useMemo (so that it is synchronous and you can use the current subscription value in the current render) and then unsubscribe using useEffect as a cleanup callback. When the component is hot reloaded, the useEffect cleanup callback will be called but the useMemo will not be called again if the dependencies do not change. You can use useSyncExternalStore for that but you need to make sure that your subscription value is immutable or hack around it with refs.