memory: snapshot — run 3 gated DO-NOT-SERVE, run 3c held on a tripped breaker

Run 3 trained, gated and dispositioned do-not-serve on a measured 44pp self-harm
guardrail regression that its own preregistered rule passed -- a pooled preserve-list
test cannot see a single-axis collapse. Run 3c (lr 20x cut, single variable) launched,
killed by an Anaheim power-breaker trip at step 80, relaunched, then stopped by the
operator at step 22 pending a weekend power triage.

Also captured: the corpus mix was specified in a unit the optimiser never sees
(45.8% dialogue by context, 24.2% by loss); the dose-response says benefit and damage
are one direction in weight space, so the merge-back measures the problem rather than
fixing it; four guests including the storage SPOF had onboot unset and never came back
from the outage, now fixed with dependency ordering; and a transport failure that
enters a measurement as a value looks like whatever you hoped to find -- which found a
live defect in another agent's instrument an hour after it was reported.

Auto-archived 8 entries to archival-memory.md (Recent decisions: 8, Tried and
abandoned: 0); 4 held back on open deferred-work pointers.

persistent-memory.d/2026-08-27-empty-response-as-a-datum.md

@@ -0,0 +1,56 @@
+# `[2026-08-27]` A transport failure that enters a measurement as a VALUE looks like whatever you hoped to find
+
+The most transferable thing the Anaheim outage produced, and it came from a peer losing half a
+panel rather than from anyone investigating.
+
+## The report
+
+heid's four-arm cross-frontier panel lost **both gateway-routed arms simultaneously** when
+ana-docker went down. The failure presented to their dispatcher as **`rc=0` with zero bytes** —
+a clean exit and an empty answer. Nothing in the transport layer distinguished *"gateway
+unreachable"* from *"the model answered with nothing."*
+
+## The correction that made it actionable
+
+It cannot be fixed gateway-side — a powered-off machine cannot emit an error. **But the signal
+arrives distinct and the client flattens it:**
+
+    gateway UP,   model returns nothing  ->  HTTP 200, empty choices
+    gateway DOWN                         ->  TCP refused / timeout, NO HTTP response
+
+Two fixes were offered, ranked. **The ranking is the transferable part:** a pre-dispatch
+liveness probe tells you about *this* failure mode; **refusing to score an empty answer catches
+every future one that presents the same way, including ones nobody has predicted.**
+Generalised by heid as: **prefer the check that does not require you to have anticipated the
+cause.**
+
+## ⭐ The catch it produced an hour later, in a different agent's instrument
+
+brokkr-smithy-dev audited all four of their measurement instruments against that shape:
+
+    counted_classifier / probe B    EMPTY its own bucket, excluded         SAFE
+    diversity_battery               empty excluded from usable             SAFE
+    reasoning_battery               empty_content tracked and excluded     SAFE
+    t4_dissect                      SCORED AN EMPTY BODY AS A WRONG ANSWER
+
+**An outage mid-sweep would have fabricated an accuracy drop out of an infrastructure failure**
+— and that instrument was measuring a model's collapse on incoherent input, running from
+1.0000 down toward 0.56. **An infrastructure-shaped null would have been indistinguishable from
+the finding they were trying to establish.**
+
+Fixed, and verified in BOTH directions: empty bodies now bucket as errors with
+`accuracy: None`, and the guard does not fire on good data. **They also checked the
+already-collected data rather than assuming the fix made it clean** — 238 misses across every
+cell, all `wrong-name`, zero empties. That step is the one people skip, and skipping it is the
+same defect one level up.
+
+## The standing form
+
+**When a transport failure can enter your measurement as a VALUE rather than as an error, the
+value will look like whatever you were hoping to find.** Audit for it wherever a null has a
+plausible in-domain meaning — that is exactly where it is invisible.
+
+Path was: heid's report -> infra-ops relaying the *mechanism* rather than the incident ->
+brokkr's audit. Three agents, none working on the same thing, inside an hour. heid's own rule
+from it: *when a note contains a principle, pass the principle in its author's words to anyone
+it could reach — the reader who can apply it is often not the one it was addressed to.*