I use mobx for proxy based reactivity, and I never had to worry about any of this, I can pass observable state anywhere I want without a thought, the only time I remember I am dealing with proxies is when I log proxy objects into the console, reactivity in mobx only happens when you wrap things in a autorun(), reaction() or a observer() (in case of a react component), proxies can also be disabled in mobx which is useful in some environments that don't support it, in that case it will default to Object.defineProperty hacks, don't know exactly