I was feeling bad about not knowing about Preact Signals, until I recognized the original MobX (which they freely acknowledge): https://preactjs.com/guide/v10/signals/ Points of departure: • MX watches (ne observers) are not just terminal computations; • MX derived values are eager by default; and • no ability for one component to navigate the app to find the state it wants. But glad to see the growing awareness on reactivity.