Solid-like but not Solid

vanilla-signal mirrors the mental model of Solid reactive primitives, not the Solid component runtime. It is designed for no-build, CDN, native-browser usage, so lifecycle, error boundary, and transition behavior all use smaller runtime semantics.

Semantics Comparison

API	vanilla-signal Semantics	Difference from Solid
`createEffect(fn)`	Runs once synchronously by default; after dependency changes, enters the effect queue.	It does not distinguish component render phases, so the first run is more direct.
`createEffect(fn, { defer: true })`	Schedules the first run in a microtask.	This is a scheduling option in this library, not equivalent to Solid’s full render queue semantics.
`createComputed(fn)`	Semantic alias of `createEffect`.	It is not a full equivalent of Solid’s internal computation primitive.
`createRoot(fn)`	Creates an owner. If the callback returns `undefined`, returns `{ dispose, run }`; otherwise returns the callback result.	The return rule is this library’s manual-runtime convention.
`onCleanup(fn)`	Registers on the current owner; runs in LIFO order before an effect re-runs and when the owner is disposed.	Without an owner, it is not bound to a lifecycle and will warn in development.
`onMount(fn)`	Runs in a microtask after restoring the current owner; skips if the owner has been disposed.	It is not a true DOM-mounted hook; direct `h/jsx` calls do not automatically get component lifecycle.
`createErrorBoundary(fn, fallback?)`	Creates a disposable owner error boundary and catches synchronous runtime errors in child owners.	`fallback` is stored only as a return field and does not automatically render UI.
`startTransition(fn)`	Puts effects triggered by this update into a lower-priority queue and flushes them when idle or after timeout.	It is not a full concurrency model and does not provide render interruption or Suspense coordination.

Usage Guidance

Put code inside render(), createRoot(), createScope(), or createEffect() when events, timers, and DOM bindings need automatic cleanup.
onCleanup() only cleans resources managed by the current owner. If called in a plain top-level script, it returns the original function but will not run automatically.
onMount() is suitable for expressing “run after the current synchronous creation phase”, not “the node is already in the document and layout is complete”.
createErrorBoundary() is suitable for catching synchronous exceptions inside reactive owners. Async Promise rejections should be handled in business async flows or createResource.
startTransition() only lowers effect flush priority. Do not treat it as UI-framework-level concurrent rendering.