reactive_helpers.svelte.ts

Runs create outside the current component or effect, so app-level state it constructs (Cells, or any class with $derived fields) outlives it.

Svelte owns a $derived by the effect that was running when it was created, and once that effect is destroyed the derived can stop recomputing — reads return its last cached value. A Cell constructed during component init does exactly that when the component unmounts, while the app keeps using it. Code in onMount or an $effect body runs inside an effect too, so state created there that outlives it goes through here as well, rather than relying on how Svelte treats those effects' deriveds today. Event handlers and async continuations run with no effect and are safe.

create runs untracked in a fresh effect root that is never destroyed (a root survives its parent's teardown), so the deriveds it creates stay live for as long as their state is referenced.