Praveenrajus/jevify-qwen3.5-2b-readout-full

Qwen3.5-2B, readout fine-tuned (full, supervised, lr 1e-6 selected on validation)

A System One decision model: it reads a state, answers typed questions (choice, score, noul) and returns calibrated probability distributions your code can branch on — it never writes text. This repo is every parameter of Qwen/Qwen3.5-2B fine-tuned, trained on its own decision readout.

At a glance — accuracy 0.703 · ECE 0.056 · held-out 0.746 · TVD to human labels 0.315 · sure loss 0.344
same order, Qwen3.5-2B, untuned (Tier 0): 0.577 / 0.089 / 0.634 / 0.458 / 0.212
same order, Jev 1.13.0: 0.733 / 0.113 / 0.835 / 0.432 / 0.081

jev-bench · leaderboard · findings · code

Use it

from jevify import load_jevified

model = load_jevified("Praveenrajus/jevify-qwen3.5-2b-readout-full")
model.ask({"text": "The battery lasted two days on a single charge."},
          {"q": {"type": "noul", "instructions": "Is the review positive?"}})

jevify-serve --model Praveenrajus/jevify-qwen3.5-2b-readout-full serves it as a drop-in for the TypeSafe SDK (TYPESAFE_BASE_URL=http://localhost:8000). The weights are in this repo.

Results

Every number is on the jev-bench test splits (22,773 records) or the study's other test suites, scored the same way for every model; the rows under this model are references from the same study.

Decisions and calibration

model	acc	ECE	Brier	held-out acc	TVD to human labels
this model	0.703	0.056	0.358	0.746	0.315
Qwen3.5-2B, untuned (Tier 0)	0.577	0.089	0.485	0.634	0.458
LoRA, same data and seed	0.701	0.051	0.362	0.736	0.324
full fine-tune + coherence (same lr)	0.704	0.056	0.358	0.742	0.307
Jev 1.13.0 (TypeSafe API)	0.733	0.113	0.349	0.835	0.432

Coherence and invariance — sure loss: mean d² over 4,749 question families (0 = perfectly coherent); order flip: how often the top answer changes when options are shuffled; tag TVD: how much the distribution moves when option tags change from A–J to other identifiers.

model	sure loss	share incoherent	order flip	tag TVD	K=2→max acc drop
this model	0.344	0.980	0.113	0.050	0.253
Qwen3.5-2B, untuned (Tier 0)	0.212	0.980	0.271	0.048	0.452
LoRA, same data and seed	0.339	0.972	0.104	0.044	0.259
full fine-tune + coherence (same lr)	0.028	0.486	0.109	0.049	0.250
Jev 1.13.0 (TypeSafe API)	0.081	0.725	0.046	—	0.246

Out of distribution — stated rules (LegalBench, rule given in the question), none-of-the-above when the gold option is removed, injected-instruction hijack rate, and three community Jev benchmarks.

model	stated rule	'none' when gone	hijack	phishing AUROC	tool risk
this model	0.671	0.336	0.055	0.775	0.783
Qwen3.5-2B, untuned (Tier 0)	0.602	0.850	0.269	0.902	0.733
LoRA, same data and seed	0.536	0.472	0.055	0.776	0.767
full fine-tune + coherence (same lr)	0.612	0.462	0.021	0.772	0.800
Jev 1.13.0 (TypeSafe API)	0.924	0.744	0.205	0.688	0.933

Reproduction check. Loading this folder with load_jevified and re-scoring 72 jev-bench test records from six sources reproduced the training run's own test predictions: 0 changed choice answers, mean largest |Δp| 0.007, max 0.038.

How it was trained

The model is trained on its own decision readout — the distribution over the allowed answers read at the answer position, one forward pass, no decoding — with the primitive's proper scoring rule. Options are shuffled per family. Training data: the train splits of the 16 non-held-out jev-bench sources (5,885 families, at most 400 records per source); lr 1e-06, 2 epochs, best epoch by validation loss (epoch 0), seed 0, fp32 master weights with bf16 autocast. A Tier 0 recipe (temperature per primitive, Noul bias, option-order permutations) was then fitted on validation splits. The six held-out sources (clinc150, arc_challenge, yelp5, measuring_hate_speech, fever_evidence, strategyqa_grounded) never appeared in training.

Files

• jevify_config.json — the recipe, the backbone and the training settings load_jevified reads
• model weights, tokenizer and chat template — the full fine-tuned checkpoint
• results/test_metrics.json — every jev-bench config; recipe.json — the fitted recipe
• results/coherence.json, probes.json, tags.json — the coherence, probe and tag tests
• results/train.json — the training log; summary.json — this model's row of the study table
• results/verification.json — the reproduction check reported under Results

Related models

• Same recipe + coherence penalty
• LoRA instead of full fine-tuning

Limitations

• One training seed per repo branch; out-of-distribution numbers in particular vary between identical runs, so compare arms across seeds before drawing conclusions.
• The phishing benchmark's decision threshold shifts after fine-tuning (ranking, AUROC, is preserved); a one-number log-odds shift fitted on a handful of labelled emails repairs it.
• English only; the recipe was fitted on jev-bench validation splits and may need refitting on a very different domain.