Z: P9 held on every clause -- the node-line draw landed on turn 64 and cost one word

Predicted at turn 34 with the run in flight, from min_life falling by exactly
1 per turn: the first phase-11 draw on turn 64, exactly 1 word, tail total 1,
bracket = ProcessTurn + 1. The game was played to turn 64 and every clause
held. predict_words, computed before the original ran, said 1 and the
measurement said 1 -- a real check of the model, against 63 preceding turns
where 0 matched 0 and checked nothing.

So the defect lane K warned about is no longer latent: on that turn a
reimplementation modelling ProcessTurn perfectly would have written an autosave
one word out of step.

And the instrument's thinnest part ran live on the same turn -- ProcessTurn
crossed a block boundary (left 11 -> 615, one twist, 20 words) and the bracket
still reconciled to residual 0.

findings/control-flow/tail-rng-ledger.md

@@ -386,19 +386,52 @@ Three things follow, none of which was knowable before:
 3. It explains why the campaign never noticed: no save in the corpus is within 40 turns of a decay event,
    and the ones that could get there are the newest saves in it.
 
-**Phase 11's draw therefore remains a path no save exercises — a hypothesis, and labelled one.** What *is*
-now instruction-verified is the predicate that decides it (§6.1), and what is measured is the distance.
+### 9.1 The prediction, and the turn it came true
 
-### 9.1 The model is stated but not yet tested
+Because `min_life` was falling by exactly 1 per turn — 43, 42, 41 … 30 at turn 34, with the traffic term
+contributing nothing on this map — a numeric prediction became possible, and it was committed to
+`sots-engine/docs/Z-tail-rng.md` §6 at turn 34 with the run still in flight:
 
-`predict_words` is computed at hook entry, before the original runs, and recorded on every node-line-decay
-record. It read **0** on every call and the measured delta was **0** on every call. That agreement is worth
-exactly nothing as a test of the model — it is the "0 diverged while comparing nothing" shape this campaign
-has already paid for — and it is reported that way rather than as a green tick.
+> **P9. The first phase-11 draw happens on turn 64, and costs exactly 1 word.** Node-line decay records
+> `np_min_life = 0`, `predict_words = 1`, and a measured `rng` delta of 1; the tail's total becomes 1
+> instead of 0; the bracket total becomes `ProcessTurn + 1`.
 
-Compare mode was **not** run on this hook for the same reason: with a prediction of 0 and a measurement of 0,
-`ours` would advance the scratch generator by nothing, diff clean, and prove only that the harness works.
-The model becomes checkable the first time a line expires, and the descriptor is ready for that day.
+The game was played to turn 64. **Every clause held.**
+
+| turn | node paths | mortal | min life | ≤5 | expired | `predict_words` | node-decay words | **tail words** | `ProcessTurn` | bracket | residual |
+|---|---|---|---|---|---|---|---|---|---|---|---|
+| 62 | 64 | 13 | 2 | 1 | 0 | 0 | 0 | 0 | 18 | 18 | 0 |
+| 63 | 64 | 13 | 1 | 1 | 0 | 0 | 0 | 0 | 18 | 18 | 0 |
+| **64** | 64 | 13 | — | 0 | **1** | **1** | **1** | **1** | 20 | **21** | **0** |
+
+**That is the first non-zero tail cost this campaign has ever recorded**, and it is exactly the draw lane K
+found by reading 0x007ae095. The defect lane K warned about is no longer latent, no longer inferred and no
+longer a hypothesis: **on turn 64 of this save, a reimplementation that models `ProcessTurn` perfectly and
+stops would have written an autosave one generator word out of step, and every subsequent turn would
+diverge.**
+
+`predict_words` is computed at hook entry, *before* the original runs, from the same `RemainingLife`
+predicate transcribed in §6.1. It said 1; the measurement said 1. That is a real check of the model — as
+opposed to the 63 preceding turns, where it said 0 and the measurement said 0, which checked nothing and was
+reported that way.
+
+### 9.2 The twist path ran, live, on the same turn
+
+The instrument's thinnest part (§8: "the block-chain machinery has never run live") was exercised on this
+very turn. `ProcessTurn` entered with `left = 11` and left with `left = 615` — it **crossed a block
+boundary**, the generator twisted, and the ledger reported `11 + (624 − 615) = 20` words. Sixty-three turns
+of measurements had all sat inside a single block, so every earlier word count reduced to a subtraction; this
+one did not, and the bracket still reconciled to a residual of 0.
+
+### 9.3 What is still not settled about node lines
+
+* **One expiry, on one map.** 51 of the 64 lines are permanent; the 13 mortal ones are Zuul-dug. A
+  non-Zuul game may never produce a mortal line at all.
+* **The `0x20000`-fleet gate has never been exercised**, because it only matters when the roll *succeeds*
+  and no fleet was riding this line. Whether the roll succeeded here is not visible in a word count — the
+  draw costs 1 either way, which is the whole point of §6's correction.
+* **Two expiries on one turn has never been observed** (`np_within5` read 1, never 2), so "one word per
+  expired line" is confirmed for *one* line and extrapolated for two.
 
 
 ---