const openfuse = new OpenfuseCloud(...);

what happens when your service goes down

It is answered in the FAQ at the bottom of the page

"The SDK is fail-open by design. If our service is unreachable, it falls back to the last known breaker state.

If no state has ever been cached (e.g., a cold start with no connectivity), it defaults to closed, meaning your protected calls keep executing normally. Your app is never blocked by Openfuse unavailability."