diff --git a/docs/REVIEW_LOG.md b/docs/REVIEW_LOG.md
index 06dc6c0..badf4a4 100644
--- a/docs/REVIEW_LOG.md
+++ b/docs/REVIEW_LOG.md
@@ -5825,8 +5825,13 @@ fight** — 4 points through Neil's armour. Seed 2 is the wipe, and its first tw
 produce a single 3-point scratch; the column lands three blows in round 3, Kate goes 12 to
 0 and Arun is disabled by a critical, and the cut is two effective attackers against three.
 
-**Both sides disable on one good hit.** The major-wound threshold is half of max HP and it
-is the same rule in both directions — the neighbours have 10, the agents 11 to 13 — so an
+**Both sides disable on one good hit.** A LOCATION is disabled when the damage it has
+taken reaches that location's own capacity — `locationMaxHp`, a fraction of total hit
+points — which is 5 for a neighbour's leg or torso and 4 for its arms, against 6 and 5 for
+an agent. (Not, as an earlier version of this entry said, at half of maximum hit points:
+that is `majorWoundFor`, it feeds only how long a dying character lasts, and being taken
+out of the fight is `conditionFor` at hp <= 2. See R-270 — the invented rule gave the right
+answer for legs and torsos, which is why it survived being read.) So an
 average blow takes a fighter out of the fight. Every disable costs its owner 30 points off
 the relevant skills — `locationEffectsFor`, an arm or a leg — which for a 40% attacker is
 three quarters of their hit chance, so it thins the return fire and makes the next disable
@@ -6003,3 +6008,38 @@ was possible — no guard measures the tail, because every one of them averages.
 **So the reading is still doing work the measuring cannot.** Fourteen guards, and the
 thing worth knowing about this fight — that it ends with one player failing three
 impossible rolls in a row — is visible only by watching it happen.
+
+## R-270 — a rule I invented, and the coincidence that hid it
+
+R-266 said "the major-wound threshold is half of max HP and it is the same rule in both
+directions". The scenario session carried the same sentence, went to `rules.mjs` to verify
+my correction of a *different* error in it, read the neighbouring functions, and found this
+one. It is not a rule. Verified here rather than accepted:
+
+| what I said | what `rules.mjs` says |
+|---|---|
+| a fighter goes down at half maximum hit points | `conditionFor` (1623) — down at `hp <= 2` or unconscious; dying at `hp <= 0` |
+| half max HP is the threshold that matters | `majorWoundFor` (32) is `ceil(hp/2)` and feeds only `dyingLimitFor` — how long the dying last |
+| one rule, both directions | a LOCATION is disabled by `resolveLocationHit` (556) at `after >= locationMax`, which is `locationMaxHp` (54) — a fraction of total hit points, per location |
+
+**The coincidence is the interesting part.** For a 10-point neighbour, `majorWoundFor` is 5
+and a leg, abdomen or chest holds exactly 5. For a 12-point agent both are 6. So on the
+locations that get hit most, the invented rule and the real one return the same number, and
+the narration prints `MAJOR WOUND · disabled` together on the same line — two rules firing
+at once, reading as one. Arms and heads are where they part (4 against 5 for a neighbour),
+and I had not looked at an arm.
+
+So the sentence was not a guess. It was a generalisation from the case where two unrelated
+thresholds agree, checked against the output, and confirmed by it. That is a worse failure
+than a guess, because it came with evidence.
+
+**Neither error is neutral in the same direction.** A disable that removes a fighter, and a
+down-threshold at half hit points, both make the fight easier than it is: fewer attackers
+still standing, and agents falling at 6 rather than fighting to 3. A GM reading either would
+have run a party-ending encounter as a survivable one.
+
+**And this is the fourth time today that checking one claim surfaced a different one.** Not
+the same claim re-examined — the neighbour of it. The pattern is worth naming: the cost of
+verifying something is mostly the cost of getting to where it lives, and once you are there
+the next function along is nearly free to read. Both of us have now paid that fare and come
+back with something we were not looking for.
diff --git a/tools/check-firstblood.mjs b/tools/check-firstblood.mjs
index 84e4972..e23260b 100644
--- a/tools/check-firstblood.mjs
+++ b/tools/check-firstblood.mjs
@@ -1,9 +1,9 @@
 /**
  * The four-player cut turns on its first disabling blow, and it must keep doing so.
  *
- * R-266 found the mechanism behind CLEAN GROUND's bimodal outcome: both sides disable on
- * one good hit, so whoever lands the first one thins the return fire and makes the next
- * likelier. It was measured in a scratch harness, and another session declined to put it
+ * R-266 found the mechanism behind CLEAN GROUND's bimodal outcome: one hit meeting a
+ * limb's capacity disables it, and both sides are made of limbs that hold 4 or 5 points,
+ * so whoever lands the first one thins the return fire and makes the next likelier. It was measured in a scratch harness, and another session declined to put it
  * in the scenario for that reason — correctly, and that refusal is why this guard exists.
  *
  * Thin on purpose. The measurement lives in first-blood.mjs, which is also the tool a
diff --git a/tools/first-blood.mjs b/tools/first-blood.mjs
index f674891..3670169 100644
--- a/tools/first-blood.mjs
+++ b/tools/first-blood.mjs
@@ -2,8 +2,9 @@
  * first-blood — who lands the first disabling blow, and what the fight does afterwards.
  *
  * check-lethality and check-focus record how a fight ENDS. Neither records how it TURNS,
- * and the four-player cut of CLEAN GROUND turns early: both sides disable on one good
- * hit, so whoever lands it first costs the other 30 points off the skills that matter,
+ * and the four-player cut of CLEAN GROUND turns early: one hit that meets a limb's own
+ * capacity disables it — 4 or 5 points either way here, `locationMaxHp` — and both sides
+ * are made of limbs that small, so whoever lands it first costs the other 30 points off the skills that matter,
  * which thins the return fire, which
  * makes the next disable likelier. Nothing pulls the fight back toward the middle once it
  * has tipped, and that — not anything about round five — is where the scenario's bimodal