# `[2026-08-26]` Run 3 corpus built, then held — and the megamix containment defect it exposed

Run 3's corpus was built to brokkr's `SFT-RECIPE-run3.md` (`f6c0589`), a blocker
was found before any GPU spend, and **brokkr is now redoing the recipe**. Nothing
launched. The build artifacts survive and are re-parameterisable.

## ⚠ THE FINDING: `creative-writing-multiturn` is a MEGAMIX containing our other roots

Its own Hoard card says so — `hoard/datasets/creative-writing-multiturn/dataset.yaml`,
`archive_provenance_note`:

> *"Dampfinchen/Creative_Writing_Multiturn — 2026 curated ~4.6k high-turn
> creative-writing/RP **megamix (bluemoon, LimaRP/PIPPA, stheno, gutenberg-dpo
> chosen, VellumK2 subset)**"*

**It is not a sibling root. It is a bag holding several of our other roots.**

Found because my corpus build would not reproduce brokkr's numbers: he computed
on the raw roots, I computed on run 1's deduped survivor list. bluemoon came out
67 against his 126. Run 1's dedup record explains it:

    DROPPED                     ->  KEPT                          n   median jaccard
    bluemoon                    ->  creative-writing-multiturn   59       1.000
    creative-writing-multiturn  ->  pippa                        30       1.000
    c2-logs-32k-llama3          ->  creative-writing-multiturn   23       0.945

brokkr then measured it directly against the raw corpora, and it is worse than
the dedup threshold showed — **the MEDIAN bluemoon conversation is 87% similar to
something in creative-writing** (≥0.99: 28.3%, ≥0.90: 49.6%, max 0.999). That is
containment, not overlap.

**Why it mattered here specifically:** the remix elevates creative-writing to
43.2% and bluemoon to 31.4% of loss signal — *the two roots that overlap*.
Building on raw roots would have double-counted bluemoon inside creative-writing's
share, in a run whose entire justification is the composition change.

## Three consequences, two of them structural

**1. "bluemoon is the only human-authored root" was overstated.** It is the only
*wholly* human-authored root; creative-writing is *partly bluemoon*. brokkr
restated rather than withdrew.

**2. ⚠ F1 does not do what the recipe says.** "Excise PIPPA" removes the ROOT, not
the MATERIAL — PIPPA persists inside the megamix, which the remix promotes to
largest contributor. **F2's 250-word floor is what actually removes PIPPA
material**, because PIPPA turns cannot exceed 123 words wherever they live. The
outcome was right; the stated mechanism was wrong. **Had the operator chosen a
floor below 123, F1 would have been nearly cosmetic.**

**3. ⚠ The dedup kept the wrong side of the pair, 59 times.** When a primary
source and a megamix containing it collide, the survivor should be the primary
source, not the copy inside the bag — the megamix version may have been
reprocessed by its curator. We kept the derivative and discarded the origin.

**Reversed for run 3** (brokkr's call, ~3 minutes): keep bluemoon, drop the
megamix copy. Result is better than either prior version —

    root                     run 2    recipe    DEDUPED+REVERSED
    bluemoon                  6.9%     31.4%              38.6%
    creative-writing         18.0%     43.2%              30.4%
    c2-logs                  40.2%     25.4%              31.0%
    pippa                    34.9%        0%                 0%

**The wholly-human share went UP and the megamix share went DOWN** — strictly the
composition the recipe argued for, now honestly counted. Total context unchanged
at 12.49M, so the operator's settled mix arithmetic survived untouched.

## ⚠ The catalog-level problem, unsolved

**A megamix root silently contains other catalog roots and nothing in the mix
arithmetic knows.** Any share computed over roots including creative-writing
double-counts bluemoon, PIPPA, LimaRP and stheno by an unknown amount. Run 2's
mix had this defect and nobody noticed, because run 2 did not promote the
overlapping roots.

LimaRP and stheno are **still unchecked against anything.** Wants a
`contains_datasets:` field on the Hoard card plus a preflight assertion that no
recipe includes both a megamix and a root it contains. brokkr is raising it as
its own item; not a run-3 blocker.

## What is staged on ana-ml2

    /tank/erp-tune/recipe-r3/recipe-erp-seat-sft-r3.json
    /tank/erp-tune/recipe-r3/dialogue-survivors.jsonl      610 conversations
    /tank/erp-tune/recipe-r3/lowquality-mask-v1.jsonl    5,867 mask rows
    /tank/erp-tune/build_r3.py       the filter build; floors are constants at the top
    /tank/erp-tune/pippa_clip.py     length-distribution measurement
    /tank/erp-tune/clip_share.py     turn-share vs word-share

⚠ **`/mnt/smithy` is READ-ONLY from ana-ml2**, so recipe artifacts live under
`/tank/erp-tune/recipe-r3/` rather than beside the r1 recipe. The harness takes
absolute paths, so this is fine — but do not expect to write to the r1 recipe dir.

**F2/F3/F4 are implemented as a LOSS MASK reusing the impersonation-mask format**,
so `load_impersonation_mask` reads it and `_impersonation_flags` sha-asserts every
masked turn with no new harness code. F4 is masked rather than stripped:
stripping mutates content, which invalidates the shas, and the read-only mount
forecloses a mutated derived root anyway. 28 turns of 6,209 (0.45%).

Re-parameterising for a new recipe is one command and ~90 seconds; the dedup
reversal and F4-as-mask handling are baked in and survive it.

## Decisions I took

**No conversation admission threshold** (brokkr delegated it, then endorsed).
81% of surviving bot turns are context-only, but masked context costs the
transformer body and **not** the LM head — the harness drops `IGNORE_INDEX`
before the 262k-vocab head, so the waste is bounded well below what the 81%
suggests. A 20% context trim buys ~35 minutes against a 3-hour run, and it would
be a fifth filter moving composition inside a run whose purpose is testing the
filters alone. **Buying 35 minutes by confounding a 3-hour experiment is a bad
trade.** brokkr: "your reason 1 is decisive."

**Left `erp-tune-v2` UP** on the operator's discretion grant. The card is not
needed until a recipe is settled, and it is his evaluation surface plus a live
gateway route. Take it down when run 3 is actually ready, not before.
