Instruct probe: voice and instruction-following coexist

Trained the same corpus onto Qwen3-4B instruct rather than -Base, with seed, steps
and token count held so the carrier is the only variable. The chain picked
checkpoint-150 by loss automatically, applying the lesson that cost a re-cut on
4B-Base.

The central risk did not materialise. The assistant prior did not block the voice:
curly quotes land at 16 of 18, identical to the 4B-Base tuned arm, against 1 of 18
on the unadapted control, and task-leak is 0 of 18 where the base carrier leaked 4.
Instruction-following also survived raw-text training -- 10 of 10 on-beat through
the chat template, the same as the untuned control.

The cost is length discipline rather than comprehension. In-band dropped from 10 of
10 to 6 of 10 and the median went from 124 to 140 words. Training on Victorian
prose made it wordier, which is a soft degradation and not a break.

Held-out sits at 2.908 against 4B-Base's 2.814, and it plateaus without turning
where the base carrier overfit at step 75. The assistant prior competes for
capacity, so the instruct carrier absorbs less rather than overfitting more.

What raw-continuation training does not fix is the plot furniture. The tuned
instruct arm renders the beat and then drags the referent -- "He licked her clean...
my master thus, my husband thus", turning the dog into a man, because the corpus is
about masters and husbands. Another beat ran to 247 words and gave the narrator a
list of duties. That is precisely what instruction-pair training addresses, since
pairs teach render-this-and-stop where continuation teaches keep-writing. The probe
de-risks the instruction-pair path without substituting for it.

One metric note against future misreading: ran_on reports 10 of 10 on both arms and
is uninformative on this job, because a single paragraph contains no blank line for
it to find.

persistent-memory.md

@@ -206,6 +206,9 @@ _As of 2026-09-10 10:25 PT._
 
 ## Recent decisions
 
+- `[2026-09-11]` ⭐⭐ **THE INSTRUCT PROBE ANSWERS ITS QUESTION: voice and instruction-following DO coexist. Option C is de-risked.** `Qwen3-4B` **instruct** (not `-Base`), same corpus/seed/steps so the carrier is the only variable; best checkpoint `checkpoint-150` picked by loss (applying the 4B-Base lesson automatically this time). **Voice installed at full strength — curly quotes 16/18, IDENTICAL to the 4B-Base tuned arm's 16/18**, against the unadapted control's 1/18, and **task-leak 0/18 vs the base carrier's 4/18**. So the assistant prior did NOT block Brontë, which was the central risk. **Instruction-following SURVIVED: 10/10 on-beat through the chat template**, same as the untuned control. ⚠ **The cost is length discipline, not comprehension** — in-band 10/10 → **6/10**, median 124w → 140w. Training on Victorian prose made it wordier, a soft degradation rather than a break. ⚠ **Held-out 2.908 vs 4B-Base's 2.814** — the instruct carrier fits the corpus **0.094 nats worse** and **plateaus without turning** where base overfit at step 75: the assistant prior competes for capacity, so it absorbs less rather than overfitting more.
+- `[2026-09-11]` ⚠ **What raw-continuation training on an instruct carrier does NOT fix: the plot furniture.** Reading the product artifact, the tuned-instruct arm renders the beat and then drags the referent — *"He licked her clean… my master thus—my husband thus"*, turning the dog into a man, because Brontë's corpus is about masters and husbands. Another beat ran 247w and gave the narrator a list of duties. **This is exactly what instruction-PAIR training is for** — pairs teach "render this and stop", continuation teaches "keep writing Victorian prose". So the probe de-risks option C without substituting for it. ⚠ Also: my `ran_on` metric is uninformative on this job (10/10 on BOTH arms) because a single paragraph contains no blank line — it measures "no paragraph break found", which is correct and useless here. Do not read it as a finding.
+
 - `[2026-09-11]` ⭐⭐⭐ **SKALDSONG'S SHAPE SETTLES THE ARCHITECTURE: the adapted completion carrier CANNOT do beat→paragraph, and an instruct model can. Option C (instruct carrier + corpus rebuilt as instruction→response pairs) is now evidence-backed, not opinion.** Operator's requirement: *"skaldsong will want to write story beats which are a sentence, and have the LLM expound on that sentence to a paragraph and stitch it together."* Booth: `http://10.100.10.50:8090/b/skaldsong-beats/`. **Adapted 4B (checkpoint-75): TEN prompt formats × 3 seeds = 30 samples, ZERO that reliably render the beat** — bare, para-break, labelled, epigraph, fewshot(1), fewshot-bare, fewshot3, elaborate, recount, label-begin. Every one drifts, frames, or truncates. Root cause is structural: *"write a paragraph **about** this sentence"* is an instruction, and a completion model has no mechanism for *about* — it continues the text it is given. ⚠⚠ **Two formats leaked PRETRAINING TASK DATA**: `para-break` emitted an NLI multiple-choice item (*"Does it follow that... OPTIONS: (1). yes (2). it is not possible to tell"*) and `label-begin` a grammar-correction exercise (*"CORRECTION: ... The passage appears to be a sentence fragment"*). A standalone sentence plus a blank line looks exactly like a dataset entry; **style adaptation does not remove base-model task artifacts.** **Instruct arm (`gen` seat + style prompt, no adapter): 10/10 samples inside the requested 90–140 band (124–148w, median 130), every one on-beat, zero drift** — but the voice is generic literary pastiche, abstract-noun-heavy and over-written, not Brontë. **So: voice without direction vs direction without voice; the product needs both.** ⚠ **This applies to Yarros identically** — the carrier question is orthogonal to the author, so the next corpus must NOT re-run this experiment.
 - `[2026-09-11]` ⚠ **Stitching has its own failure mode, visible in the booth's Panel C: independently-generated paragraphs drift in POINT OF VIEW.** By beat 4 of 5 the narrator is simultaneously watching the girl carry the animals and carrying them herself ("their weight a strange, heavy secret carried between my ribs"). Each paragraph was generated with no knowledge of the others. **A real stitcher must feed prior paragraphs back as context**, which also means the instruction-pair corpus should include multi-paragraph continuity examples, not just isolated beat→paragraph pairs.