An answer nobody gave is not cached

"Nobody answered yet" and "there is nothing there" are different facts. Until they were told apart, a cold moment on a replica made a durably present node read as absent — permanently, for that process, with no error anywhere.

The three properties that compose into it

1. A synced query chain is the process's answer, once. MeshNodeStreamCache.GetQueryRaw builds every hub.GetQuery chain as Replay(1) + AutoConnectOwnedBy and keeps it in a registry that is never rebuilt. The FIRST frame is replayed to every later caller. That is the point of the cache — one upstream subscription, cheap re-reads — and it is right for a real answer.
2. An empty frame is an ordinary outcome, even when no provider spoke. MeshQuery.MergeProviderObservables counts a provider that COMPLETES WITHOUT an Initial as an EMPTY Initial, deliberately: the alternative starved the merge's gate and hung every real-user unpinned search for 300 s (prod, 2026-07-03). So the merge proceeds — correctly — and hands downstream a frame that says "nothing matches" with nothing behind it.
3. Nothing corrects it. The only event that refreshes a live chain is a change notification for a matching path, and the commonest writer of such a path is a reconcile re-writing an unchanged node — a NO-OP at the store (IsNoOpUpsert), which publishes nothing.

Cold answer + permanent cache + no corrective event = a false absence that outlives everything short of a restart.

Measured

Admin/_LogIncident/d1cd36f53a5f3a6c on memex-cloud — the plugin gate, 11,927 occurrences (MeshWeaver#1246). All ten retained samples fall in the 24 minutes after the 2026-09-16 21:24Z restart; the incident went quiet at 21:48Z. Every path they name, read afterwards:

Nine of ten are a durably present node read as missing. The burst-after-restart-then-quiet shape is the signature: the cold read happens while every per-node hub activates, and the wrong answer then sticks to the chain.

What the framework does now

• The frame says what it is worth. QueryResultChange.SilentProviders NAMES the providers that completed without an Initial and were counted as empty — the sibling of Partitions, which already exists so a zero can be read against the set it was read from. Null/empty means every provider answered.
• The single-provider path honours the same contract. A lone provider that completed silently used to leave the merged stream completing with NO frame at all, which a caching consumer keeps just as durably ("completed, nothing"). It now delivers the empty Initial and names the provider.
• A frame nobody answered is delivered, not kept. MeshNodeStreamCache drops that chain from its registry (EvictUnansweredQuery, pair-exact on (id, query set) like the faulted-chain eviction of #1316), so the next GetQuery for that id opens a fresh chain and asks again. Live subscribers keep the chain they hold — it is a real, running query whose next frame may well be complete — and its upstream is NOT released, because tearing a live read out from under readers to save one subscription is a worse trade than one extra subscription.

What it deliberately is not:

Pinned by ColdEmptyInitialIsNotCachedTest (real mesh: a provider that is silent on its first subscription and answers afterwards — the second read must find the node, and the control arm proves an answered frame is still cached) and by MeshQueryMergeContractTest (the merge names silent providers, names none when all answered, and the single-provider path answers an empty Initial that names itself).

The consumers this was reaching

A judgement per single-node / decisive-emptiness consumer of hub.GetQuery, swept over both repositories at 2026-09-17. "Cost" is what a cold false-absent buys; all of them are now served by a chain that cannot keep an unanswered frame, so the residual exposure is one wrong answer to the caller that triggered the cold read, never a permanent one.

Systemorph/MeshWeaver

Systemorph/MeshWeaver.Plugins

Related

• CQRS — Queries vs. Content Access — why a single known node's content comes from its owner, and a query is for sets.
• Silent Completion — the sibling shape: an empty completion is invisible to every timeout.
• Query Identity — the other way a read answers "absent" without anything being absent.