Receiver: one listener, one verb

nodes.subUpdates.listen((e) async {
  if (e.subName != 'samples' || e.ancestry.length != 2) return;

  final sample = await nodes.getDescendant<StatSample>(
    ancestry: e.ancestry,    // [host CAncestor, atSign CAncestor]
    id: e.id,                // <millis>
    owner: e.owner,          // sender atSign
    leafExpiration: ttl,
    leafFromJson: StatSample.fromJson,
    leafTypeTag: 'StatSample',
  );

  if (sample != null) window.add(sample.obj);
});

• One subscription on the root catches every descendant subUpdate, at any depth.
• getDescendant walks the parent chain in a single call. It replaces a hand-coded getOrNull → subCollection → getOrNull → subCollection → getOrNull ladder.
• Returns null if any link in the chain is missing, expired, or has availableAt in the future. The receiver retries on the next event without exception handling or special cases.

That's the entire receive loop. The Flutter dashboard does this plus chart rendering in around 100 lines.