Pre-registration: own-baseline arm (fontaine_arb_rcond_100k_1xh100)

SUPERSEDED 2026-08-05 16:13Z, never launched — owner steering replaced the standalone baseline with a paired 40k design whose arm A is this recipe at 40k and doubles as the own-topology control. Body below preserved verbatim per the immutability convention.

2026-08-05. Immutable once posted; the launcher header carries the same content. Launches tonight after the bootstrap eval bursts, gated on the smoke run passing.

Question

What does the mainline-best recipe (bijou_arb_rcond_100k_ddp4 — request-conditioned ar_backbone, prompt fmt 3 / suffix fmt 5) do on this topology — 1×H100, eff-batch 10, single process — at matched steps? Charter §4’s own-baseline rule: until this arm exists, every training delta on this box is “vs mainline, cross-topology — directional only”. This run is the anchor later arms pair against.

Exact command

~/launch_fontaine_arb_rcond_100k_1xh100.sh (committed convention: launcher header = this post). Recipe flags verbatim from the mainline 100k report; differences, exhaustively: --batch-size 10 (vs 12→10; B10 is mainline’s standing post-OOM setting — adopted from step 0, no batch roulette), single process (no DDP wrapper), --num-workers 16 --prefetch-factor 4, --save-every 5000, wandb project fontaine. Seed 0, fresh run, no resume.

Numbered expectations

1. Startup: selection 878 datasets / 42,872 episodes (verified on this mirror today); model line = ~11M new decoder params + live text trunk at 2e-5; wandb run visible in fontaine.
2. Throughput: 0.4–0.6 s/step at B10 (mainline per-rank 0.42–0.47 at B10–12); VRAM peak < 76 GiB (B11 measured 75.6); ~12–14 h wall for 100k.
3. Curve (256-frame in-run probe, ±0.3 floor): below 12 by 10k, below 9 by 30k. The mainline eff-48 curve (7.54@10k, 6.57@30k, 5.55@100k) is expected to be AHEAD of this arm at every matched step — eff-10 sees 1/4 the samples per step. This arm matching the mainline curve would itself be a finding (batch-size insensitivity at fixed steps).
4. Kill gates: probe > 15 at 10k with a falling-then-rising shape (divergence, not slowness); NaN loss; second OOM after the standing B−1 resume. Slowness alone is data, not a kill.

Known seams and confounds

• eff-10 vs eff-40 means same-steps ≠ same-samples vs mainline: this arm anchors the topology precisely so that later comparisons are paired on it, not on mainline.
• LRs are kept verbatim (1e-4 / 2e-5) rather than batch-rescaled — deliberate: the arm measures the recipe as-is on this box; an LR-rescale arm is a separate follow-up if the curve is badly off.
• Expected fingerprint of the smaller batch: noisier probe series and a later-arriving plateau, not instability.

Cost

~12–14 h of the standing GPU (overnight — charter §3), ~480 GB disk (checked against df), zero API spend.