Subgoal-draws rung (b) closes at table cost: T=1 derails 11.5% of draws (#6)

2026-08-08 ~10:2xZ. Stage-1 result of the subgoal-draws pre-reg: a pre-registered go/no-go bar failed, so stage 2 (the conditioned arms) does not run — “the table is the rung-(b) result” was the frozen rule, and this is that result. Cost: ~1.6 of the 6 GPU-h ceiling (preflight + table). Live oracles were ALL GREEN before the judgment: the draws-0 limit reproduced the rung-(a) self decode bit-exact at matched composition, and forced-empty reproduced the plain path bit-exact — the instrument is sound; the data failed the bar.

The mechanical bars

60 stratified frames × (1 greedy + 8 sampled @ T=1.0) candidates:

What actually fails: an 11.5% derailment mode

Zero sampled candidates are empty. The greedy candidate is clean on all 60 rows. The failure is entirely truncation: 55/480 sampled draws (11.5%) derail into non-terminating multilingual gibberish and hit the decode budget — e.g. (verbatim):

दशकों इनमेंଐ হয়েছিল নিয়ন্ত্রণেപ്പെട്ടിэлекә휋本书 ged फाइल सं…

At T=1.0 the open-vocab text head occasionally samples an off-distribution token and never recovers. With an 88.5% per-draw clean rate, the probability that all 8 sampled draws in a row are clean is ~0.885⁸ ≈ 38% — the measured 33% is exactly that binomial arithmetic. The bar was written against broken decoding; what it caught is a real, quantified property of T=1.0 sampling on this head.

The clean draws are good — and the scorer already refuses the bad ones

Two free reads from the same table (record-only, no GPU):

• Criterion (d), by eyes: every clean candidate inspected is subgoal-shaped and phase-relevant — “lift and carry the battery over the bin”, “reach toward the blue toffee on the cloth”, “retract the arm to the rest pose”. Real phase alternatives appear (row 4: greedy “grasp the toffee” vs sampled “reach down toward the blue toffee” — adjacent phases, the exact ambiguity rung (a) located). Diversity is genuine: the self-certainty pick differs from the greedy string on 39/60 rows (expectation 5 said ≥ 20%, low confidence — measured 65%).
• Self-certainty vs the gibberish: the frozen scorer picks a truncated candidate on 0/60 rows; across all 55 truncated candidates the SC rank is median 9th of 9 (never top-3). Derailed decodes are exactly the high-entropy strings SC is built to down-rank. The risk the bar guards (conditioning pass 2 on gibberish) would not have materialized through this scorer — but that is a 60-row observation, not a guarantee, and the pre-reg forbade candidate filtering (“used as decoded”), so the bar stands and the rung closes.

What this rung banked

1. T=1.0 sampled decoding of the subgoal head has an 11.5% derailment rate (budget-truncated multilingual gibberish); greedy never derails (0/60).
2. Candidate diversity at width 9 is real (97% of rows ≥ 2 unique strings; no cross-frame collapse — top pooled string 4.8%).
3. Self-certainty structurally avoids derailed candidates (0/60 picks; median rank last).
4. Δ_bon / Δ_ceil remain unmeasured — whether selection beats greedy self-conditioning is still open at this width.

Escalation (needs its own pre-reg, per the closing clause)

The obvious next rung: identical design with a truncation-robust candidate list — either exclude budget-truncated candidates from the scorer’s list (structural version of what SC already does; fallback to greedy when all sampled draws derail) or move the sampler to nucleus/lower-T. The stage-1 evidence above is the written prior; the instrument delta is small and the whole preflight apparatus (live oracles, matched-composition comparators) is landed and green. Queued as idea6-subgoal-draws-cleancand-prereg-draft; nothing launches without the posted pre-reg.