# lv-hemingway v2 gate — pre-registration

**Written 2026-09-17, before a single generation existed.** Everything below is
fixed. The point of writing it down is that a threshold chosen after seeing the
numbers is not a threshold, and this line has already been burned once: lv-bronte's
verdict turned on which arms happened to be in the run (see § 4).

Nothing here may be amended after the first arm is generated. If the design turns
out to be wrong, the run is wrong and gets re-run — the rule does not move.

---

## 1. What is being gated

`gx10:~/r49-runs/hemingway-4b-pairs-3ep/` — Qwen3-4B-Instruct + instruction-pair
LoRA on the renamed Hemingway corpus (994,760 words, 318 units, 6 renamed copies;
leak gate 0 of 941 entities with both controls green). 3-epoch schedule, seed 4919,
2,661 steps, finished 2026-09-16 18:27.

## 2. Arms — three, and why each one is present

| arm | what it is | role |
|---|---|---|
| `base-unadapted` | `~/carriers/Qwen3-4B-Instruct`, no adapter | negative control for memorisation (never saw the corpus) **and** the voice baseline |
| `ckpt1750` | epoch 1.973, eval_loss **2.2783** — the curve's minimum | ship candidate |
| `ckpt850` | epoch 0.959, eval_loss **2.2823** | **tied** candidate, see below |

⭐ **`ckpt850` is in the run because the loss curve cannot separate it from
`ckpt1750`.** Measured on this run's own 54 eval points: median neighbour jitter
**0.0044**, and step 850 sits **+0.0040** above the minimum. Three checkpoints are
inside one jitter of the best (850, 1700, 1750). "The minimum is at 1750" is true
and is *not* a reason to believe 1750 is the better adapter — picking it by staring
at the fourth decimal is reading noise, which is exactly what lv-bronte recorded
about its own 475-vs-925 pair.

There is also a prior worth testing rather than assuming: on Brontë the EARLIER,
epoch-1 checkpoint won the tiebreak on the axes that resolve (identical-to-control
memorisation, 2.7× tighter seed variance). Epoch 2 bought Brontë nothing. If that
repeats here, `ckpt850` ships and half an epoch of overfit is avoided.

**`adapter/` (end of run, epoch 3.0, 2.3546) is NOT gated.** It is +0.0762 worse
than the minimum — **17.4× the median jitter** — so unlike the 850/1750 pair this
one is resolved by the loss curve alone. The epoch-3 collapse is the robust finding
on this schedule; the epoch-2-vs-epoch-1 question is the open one.

## 3. Fixture and seeds — fixed now

- **60 beats**, sampled by `build_beat_fixture.py` from `~/hemingway-pairs/pairs-val.jsonl`
  (held-out `split=val`, 200 pairs, **173 inside the 90–150 word band**), `--seed 4919`,
  spread across works round-robin.
- **4 seeds: 1234 5678 9012 3456.** Same as lv-bronte.
- → 240 generations per arm, 720 total.

**Why 60 and not 30.** The floor is a per-seed range and per-seed variance scales
as 1/√N, so doubling lv-bronte's 30-beat fixture buys a ~1.41× tighter floor. 173
in-band val pairs make 60 available; Brontë had 44 in-band and *could not* have run
this. **More seeds would not help** — the floor is a range statistic and ranges
widen with more samples.

## 4. ⚠ THE FLOOR RULE — changed, and this is the change that matters

**The noise floor for a candidate is the larger of the within-arm seed spreads of
the TWO arms being compared: `max(spread(candidate), spread(base-unadapted))`.**

This is a deliberate amendment to the rule lv-bronte ran under, made before any
Hemingway number exists. Under the old "largest spread across ALL arms" reading:

```
base-unadapted   spread 0.062
ckpt475          spread 0.092   <- shipped
ckpt925          spread 0.251   <- set the floor, on ONE outlier seed
```

`ckpt475`'s **+0.193 was failed by a floor contributed entirely by a third arm
nobody was shipping.** Scored pairwise the floor is 0.092 and the same gap clears
at 2.1×. A candidate's verdict must not depend on which *other* arms you happened
to generate — and with a three-arm design that defect is live again, which is why
the rule is settled here rather than after the table prints.

`voice_distance.py` prints **both** floors and flags any case where the two rules
disagree. The pairwise number is the verdict; the all-arms number is kept so the
lv-bronte record stays comparable.

## 5. The three axes, and what passes

| axis | instrument | passes if |
|---|---|---|
| **A. VOICE** | `voice_distance.py --author Hemingway` (Burrows's Delta over char bigrams vs the held-out val split) | `delta_cb(base) − delta_cb(candidate)` **exceeds the pairwise floor** |
| **B. NOT COPIED** | `memorization_check.py` (longest verbatim n-gram vs the renamed copies, n=8) | hit-rate and max at or near `base-unadapted`, which never saw the corpus. Positive control (corpus vs itself) must saturate, or the zeroes are blind |
| **C. NO DAMAGE** | `score_beats.py --metric-source raw` | ran-on / out-of-band rate not worse than base beyond that metric's own floor |

A **FAIL on A with B and C clean** is the lv-bronte outcome and is NOT
automatically a no-ship — it was shipped there as additive, reversible and
safety-clean. That call is the operator's, and the difference here is that
**Hemingway is not public domain the way Brontë is**, so axis B carries more weight
in that conversation, not less.

## 6. Pre-flight already run — the beat-contamination audit

`audit_pairs_sourcenames.py` over all 7,294 built pairs, controls green
(941/941 surfaces found in the unrenamed source; nonce absent from both trees;
6/6 planted names detected in a positive control):

- **val pairs — 0 of 200.** The fixture is drawn from these, so the eval beats are
  clean and the gate is unconfounded. This is why the gate runs at all.
- **train pairs — 70 of 7,094 (0.96%)** name a character the rename removed
  (`Santiago` ×16, `Catherine` ×7, `Rinaldi` ×3, `Brett`, `Harry`, `Jake` …),
  with **0 of 7,294 responses** affected — the lv-bronte beat-only signature
  exactly. The pairs predate `build_sft_pairs.py --source-entities`.

**This is a property of the trained adapter and it is on the record before the
gate runs, not discovered afterwards.** It does not invalidate any axis: the
instruction half is contaminated, the target half is not, and the fixture is clean.
Whether to retrain on filtered pairs is a separate decision with its own cost, and
it belongs to the operator.

## 7. Reproduce

```bash
# on pfi-gx10, ~/lv-hemingway
./eval-hemingway.sh          # three arms, 60 beats, 4 seeds
python voice-prep.py         # beats5.* -> voice.*, control renamed to *unadapted*
scripts/r49-corpus/voice_distance.py corpus-renamed ~/r49-runs/hemingway-eval --author Hemingway
```