grug-rule-350m — a from-scratch 350M deduction organ (research artifact)

⚠️ This is not a usable chat model. It is a 341.9M-parameter decoder-only transformer trained from scratch on a synthetic deductive-reasoning DSL (effective vocab: 355 BPE tokens). It speaks nothing else. Its value is as a reproducible research artifact for two results and one training-stability case study — and as a checkpoint you can re-evaluate yourself for ~$0.30.

Part of akh-medu at source commit 053c6651 / Project Grug-Brain: the bet that a tiny model can hold reasoning while an external knowledge engine holds facts.

The two results

1. Narrow deductive competence scales cleanly. On held-out modus-ponens chains over in-prompt rules (depths 2–4), n=512: answers 0.928, trace validity 0.928, and the strict select/bind/fire/chain decomposition scores 1.000/1.000/1.000/0.935 — exceeding the 11M reference model (chain 0.918) that gated this run. This competence is learned, not latent: a generic 600M pretrained model (Qwen3-0.6B), given few-shot exemplars, scores below the majority-class baseline on the same test (it imitates the trace vocabulary and copies exemplar label frequencies — format mimicry, not derivation).
2. Capacity does not buy length generalization. At unseen depths 5–6: chain 0.000 — identical to the 11M and 50M models. A 31× parameter increase moved this number not at all. The wall is architectural.

The training-stability case study

The run survived what killed two predecessors: epoch-periodic gradient storms — bursts of batches with finite loss (~ln(vocab), i.e. collapsed- to-uniform logits) but non-finite gradients, recurring at the same stream positions every epoch, across different random inits, at learning rates from 4.4e-5 down to 5e-6. Two content-side root causes were tested and falsified (context-length truncation: max sequence 677 vs ctx 1024; batch-content logit divergence: trigger batches produce logits ≈25, identical to controls). What stands is a data-position × optimizer-state interaction on a fully-converged task (Adam second-moment collapse; cf. Adaptive Edge of Stability, arXiv 2207.14484; PaLM §5.1's batch-skip experience, arXiv 2204.02311).

The kill mechanism, confirmed in source: per-parameter-tensor Norm(1.0) gradient clipping divides an inf-norm gradient by infinity → NaN weights in a single optimizer step. The mitigation stack that let this run finish:

• linear warmup + cosine decay (peak 5e-5),
• a loss-spike gate (skip updates > 4× loss-EMA),
• a global pre-clip grad-norm gate (skip non-finite or > 5× gnorm-EMA).

501 poisoned updates refused over 17.1h on one A100; zero weight damage; ~$28 of compute. Because the corpus is deterministically seeded, the storms are byte-reproducible — they arrive at the same steps if you rerun the recipe, which makes this checkpoint's lineage a rare controlled testbed for training-instability research.

Files

• model.mpk — Burn 0.21 checkpoint (step 28000; best; the three final checkpoints score identically to 3 decimals)
• tokenizer.json — byte-level BPE trained in-process (vocab 3000, saturates at 355 on this templated corpus)
• eval_rule.json — the definitive n=512 evaluation output
• eval_rule.jsonl — 12-point training-time eval series
• logs/ — all four runs' training logs, including both fatal NaN runs (p350m-run1-nan.log, p350m-run2-skipflood.log) — the storms and the gate refusals are visible line by line

Reproduce (from scratch, ~$30, or any 24GB+ GPU)

git clone https://code.aopc.cloud/toasterson/akh-medu.git
cd akh-medu && git checkout 053c66516074c5cdc13438df230c4a92bc7a1125
bash training/scripts/setup-cuda.sh   # rust + CUDA build + 60-step smoke
bash training/scripts/run-350m.sh     # detached, resumable, guarded
bash training/scripts/status.sh p350m

No dataset download: the corpus (40,000 examples, seed 42) and the tokenizer are generated in-process. Evaluate this checkpoint without training: eval_rule --n 512 --resume <checkpoint dir> (see training/results/README.md). The cross-model exam harness (dump_rule_eval / score_rule_jsonl + an MLX runner) lets you sit any model against the same scorer.

Full run report: training/results/p350m-RESULT.md in the repo.

Architecture

d_model 1024 · 24 layers · 16 heads · d_ff 4864 · ctx 1024 · learned positional embeddings · fp32 training (Burn 0.21 / CubeCL, CUDA) · Adam + per-tensor Norm(1.0) clip + the gate stack above.

Native multimodal development status (2026-09-04)

This published model.mpk is text-only. It contains neither the new visual stem nor multimodal training and must not be advertised as an OCR model.

The companion research artifacts under research/adaptive-vision-v1/ document an implemented continuous-exam controller and two native visual-prefix candidates sharing the BabyLLM decoder. The first CPU smoke reduced teacher-forced loss from 5.6197 to 0.0930 but emitted the same transcript for all three images (cross_semantic_collapse_rate=1.0), and the raw-patch stem failed held-out translations. Those negative results remain published.

Failure-directed refinement selected a compact stride-16 convolutional stem. Its 3.31M shared-decoder checkpoint passed the deliberately narrow V1 training-overfit gate: 128/128 exact clean-line transcripts, zero CER/WER/blank and zero cross-semantic collapse. It also loaded into the local CPU backend and produced 3/3 exact outputs under an OS network-deny sandbox. The experimental checkpoint, Adam state and exact compatibility tuple are under research/adaptive-vision-v1/checkpoints/compact-clean-line-v1/; they do not replace root model.mpk.

This is not a usable general OCR claim. The checkpoint saw every scored string during training. Different-renderer/real images, unseen strings/fonts, EN/DE/FR, corruptions/layouts, metamorphic groups and text-retention gates are still unrun or red. Those boundaries are part of the published model card, results and checkpoint README.

License

MIT (published weights, tokenizer, evaluation outputs, and logs). The linked training/evaluation source code is GPL-3.0-only.