BlockCoverage

What the provider actually examined when it produced an AppliedBlock.

A provider that holds the whole block can answer any subscription from it. A metered provider cannot afford to: Blockfrost's cheap path is per-address and per-asset endpoints, so what it learns about a block is only ever "what these sources did in it", and it must say so.

The distinction is load-bearing rather than informational. The hub delivers a block to a subscription and advances that subscription's watermark past it in the same step, so handing it a block that did not cover a subscription would tell that subscriber "nothing here for you" — as an scalus.cardano.node.stream.UtxoEvent.Idle, no less — and then make the real events for that height undeliverable, because the watermark has moved on. Silently.