R-281: a ratchet, because "helps in all of them" survives the advice decaying

R-280 left the claim satisfiable by a gain of 0.2. The artifact now records how
many measurable packs clear their own noise -- reliable: {aboveNoise: 36, of: 38}
-- and the check refuses if that share falls. It may rise freely.

A ratchet rather than a threshold: any threshold here would be a number I chose,
and choosing one just under the current value is what produced MEASURABLE =
[15,85]. A share rather than a count, so widening admission cannot pay it off.

Proved three ways in worktrees: making focus fire actively bad fires the drift
check first, which is correct; making it unreliable and re-recording fires the
older claim at 37 of 38; and claiming a better past, 38 of 38, is refused by the
ratchet itself. The ratchet bites exactly where the old claim does not -- between
"still helps everywhere" and "helps as reliably as it did", which is where a slow
degradation lives.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/REVIEW_LOG.md

@@ -6539,3 +6539,37 @@ measurable pack — is satisfied by gains of 0.2, so it is a weaker sentence tha
 the band admitted only contested fights. If it should be a stronger claim, the place to
 strengthen it is the claim, not the admission rule; tightening admission to protect a claim
 is how the band got here.
+
+## R-281 — a ratchet, because "helps in all of them" survives the advice becoming useless
+
+R-280 left check-focus asserting that focus fire helps in every measurable pack, and that
+sentence is now satisfied by a gain of **0.2**. True, and thin: the advice could decay to
+nothing everywhere it is not already decisive and the guard would still pass.
+
+**The strengthening is a ratchet rather than a threshold.** The artifact records how many
+measurable packs showed a gain clearing their own noise — `reliable: { aboveNoise: 36, of:
+38 }` — and the check refuses if that SHARE falls. It may rise freely.
+
+A threshold here would be a number I chose, and choosing one to sit just under the current
+value is the move that produced `MEASURABLE = [15, 85]` in the first place. A ratchet has no
+chosen number in it: the bar is the measurement, and it moves only when the game does.
+
+**It is a share and not a count**, so it cannot be satisfied by admitting more packs — which
+matters, because R-280 just widened admission from 31 to 38 and a count-based ratchet would
+have been paid off by the widening.
+
+**Proved by trying it three ways**, in throwaway worktrees:
+
+- *Make focus fire actively bad* — target the healthiest enemy instead of the most hurt.
+  The drift check fires first and names four creatures, which is correct: any movement is
+  drift before it is anything else.
+- *Make it unreliable and re-record* — concentrate only half the time, then `--update`.
+  The older claim fires: focus fire now helps in 37 of 38, so the page's flat assertion is
+  already false and the ratchet is never reached.
+- *Leave the game alone and claim a better past* — set the recorded share to 38 of 38. The
+  ratchet refuses: *"clears its own noise in 36 of 38, down from 38 of 38 ... that is a
+  change in the game, not a baseline to refresh."*
+
+The middle case is the useful one to understand: **the ratchet only bites where the existing
+claim does not**, in the band between "still helps everywhere" and "helps as reliably as it
+did". That band is exactly where a slow degradation lives, and it was unguarded until now.

tools/check-focus.mjs

@@ -131,7 +131,7 @@ const pickSize = spec => {
 
 if (UPDATE) {
   const creatures = {};
-  let measurableCount = 0;
+  let measurableCount = 0, aboveNoiseCount = 0;
   for (const spec of NPCS) {
     const pick = pickSize(spec);
     /* Measured first, then admitted or not: the noise this test needs is a product of the
@@ -143,11 +143,17 @@ if (UPDATE) {
     }
     creatures[spec.key] = row;
     measurableCount++;
+    if (row.gain > row.noise) aboveNoiseCount++;
   }
   await writeFile(BASELINE, JSON.stringify({
     note: "Generated by tools/check-focus.mjs --update. Do not edit by hand.",
     party: PARTY_KEYS, runs: RUNS, seeds: SEEDS, seedMode: SEED_MODE,
-    admission: "spread clear of 0 and 100 by more than its own noise", creatures
+    admission: "spread clear of 0 and 100 by more than its own noise",
+    /* R-281. The ratchet the claim check holds to: how many of the measurable packs
+       showed a gain clearing their own noise when this was recorded. Focus fire may
+       get more reliable and may not quietly get less. */
+    reliable: { aboveNoise: aboveNoiseCount, of: measurableCount },
+    creatures
   }, null, 2) + "\n", "utf8");
   console.log(`check-focus: baseline recorded — ${measurableCount} of ${NPCS.length} creatures measurable, `
     + `${RUNS} runs x ${SEEDS.length} seeds, seed ${SEEDS[0]} ${SEED_MODE}`);
@@ -226,5 +232,27 @@ if (helped !== checked) {
   process.exit(1);
 }
 
+/* R-281. "Helps in all of them" is satisfied by a gain of 0.2, which is true and thin: it
+   survives the advice becoming useless everywhere it is not already decisive. So the
+   RELIABILITY is recorded and ratcheted — the share of measurable packs where the gain
+   clears its own noise may rise and may not quietly fall.
+
+   A ratchet rather than a threshold, because any threshold here would be a number I chose.
+   This one is the measurement itself, and it fails only on a real change in the game. Note
+   the direction: this cannot be satisfied by admitting more packs, since it is a share. */
+const wasReliable = base.reliable;
+if (wasReliable && wasReliable.of > 0) {
+  const wasShare = wasReliable.aboveNoise / wasReliable.of;
+  const nowShare = aboveNoise / Math.max(checked, 1);
+  if (nowShare < wasShare) {
+    console.error(`check-focus: FAILED — focus fire clears its own noise in ${aboveNoise} of `
+      + `${checked} packs, down from ${wasReliable.aboveNoise} of ${wasReliable.of}. The advice `
+      + `still helps everywhere, and it has become less reliably worth taking than when it was `
+      + `recorded. That is a change in the game, not a baseline to refresh: find what moved `
+      + `before re-recording, and rewrite the page if the advice is now weaker than it reads.`);
+    process.exit(1);
+  }
+}
+
 console.log(`check-focus: OK — focus fire measured against ${checked} packs, helps in all of them`
   + `, ${aboveNoise} of them by more than their own noise`);

tools/focus-baseline.json

@@ -14,6 +14,10 @@
   ],
   "seedMode": "per-creature",
   "admission": "spread clear of 0 and 100 by more than its own noise",
+  "reliable": {
+    "aboveNoise": 36,
+    "of": 38
+  },
   "creatures": {
     "quiet_neighbours_npc": {
       "n": 6,