autotrust/JEV-Gemma4-26B-A4B

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An integrated System 1 + System 2 open model on Gemma-4-26B-A4B-it — Decision Index 0.2.1: 58.05

This bundle serves two systems from one set of base weights. System 2 is the unmodified google/gemma-4-26B-A4B-it (a 26 B-parameter mixture-of-experts model with ≈ 4 B active parameters per token, text and image input): generation and reasoning, bit-identical to the base model. System 1 adds a LoRA adapter and a 24-slot decision head and returns calibrated probabilities for three typed primitives in one prefill pass:

• noul: true / false
• choice: 2–16 options (wider questions are read in groups of ≤ 16 plus a final)
• score: 0–5

Two models, two organisations. TypeSafe Jev 1.13 is the hosted, closed model made by TypeSafe AI. autotrust/JEV-Gemma4-26B-A4B is an independent open-weights model built by AutoTrust AI; it is not affiliated with, endorsed by, or a product of TypeSafe AI.

Decision Index 0.2.1

Complete run of all 150,759 requests of suite 0.2 (150,317 scored; 0 errors, 0 unsupported), scored with the kit's score --edition 0.2.1. Results: autotrust/jev-decision-index-results (runs/jev-gemma4-26b-a4b).

Engine and read-out

• Template bare-v1, prefixed with <bos>: [kind] … [state] … [question] … [options] A) … [decision]:
• Read-out: the final-norm hidden state of the last token goes through a linear fp32 head (hidden 2,816 → 24 slots), soft-capped at 30 like Gemma's own logits; inactive slots are masked, the logits are divided by the per-kind temperature and softmaxed. Nothing is generated.
• Adapter: adapter/ is merged into the bf16 backbone in memory at load (as in the Decision Index run).
• More than 16 options: ⌈n/16⌉ contiguous groups read whole, then a final of 16; every option is read, none pruned.

The reference engine for the Decision Index is submissions/jev/jev_engine.py in the Decision Index kit.

Temperatures

Use calibration_gold.json when you gate automatic actions on confidence.

Usage (transformers + peft)

import json, torch
from huggingface_hub import snapshot_download
from peft import PeftModel
from safetensors.torch import load_file
from transformers import AutoTokenizer, Gemma4ForConditionalGeneration

d = snapshot_download("autotrust/JEV-Gemma4-26B-A4B")
tok = AutoTokenizer.from_pretrained(d)
base = Gemma4ForConditionalGeneration.from_pretrained(d, dtype=torch.bfloat16, device_map="cuda")
# System 2: `base` is gemma-4-26B-A4B-it unchanged — use base.generate(...) (text or images).

# System 1: adapter merged in memory + head
m = PeftModel.from_pretrained(base, f"{d}/adapter").merge_and_unload().eval()
backbone = m.model
jc, T = json.load(open(f"{d}/judge_config.json")), json.load(open(f"{d}/calibration.json"))["per_kind"]
head = load_file(f"{d}/head.safetensors"); W, b = head["proj.weight"].cuda(), head["proj.bias"].cuda()

@torch.no_grad()
def decide(kind, state, question, options):
    lines = options if kind != "choice" else [f"{'ABCDEFGHIJKLMNOP'[i]}) {o}" for i, o in enumerate(options)]
    text = f"[kind] {kind}\n[state] {state}\n[question] {question}\n[options]\n" + "\n".join(lines) + "\n[decision]:"
    ids = torch.tensor([[tok.bos_token_id] + tok.encode(text, add_special_tokens=False)], device="cuda")
    h = backbone(input_ids=ids, use_cache=False).last_hidden_state[0, -1].float()
    z = 30.0 * torch.tanh((W @ h + b) / 30.0)
    s, _ = jc["slots"]["ranges"][kind]
    return dict(zip(options, torch.softmax(z[s:s + len(options)] / T[kind], 0).tolist()))

print(decide("noul", "Customer says the parcel arrived damaged and wants their money back.",
             "Is the customer asking for a refund?", ["false", "true"]))

Training data (disclosure)

System 1 was trained on teacher distributions and ground-truth decision data. The ground-truth data includes the public training splits of some datasets whose test splits the Decision Index uses; no test split of any benchmark was used, and suite items were excluded before training. The list has been provided to the Decision Index maintainers with the submission. MMMU / MMMU-Pro are not valid evaluations for this model.

Limitations

• Where the teacher is wrong, System 1 often is too.
• Weaker than JEV-27B on long structured inputs (e.g. the Decision Index's Home appliance simulator and POP909).
• HLE: below chance, like every open entry on the board; do not use System 1 for expert-level questions.
• noul and score accept only their canonical options.
• English-centric; not for high-stakes decisions without confidence gating.

Files

model-*.safetensors · config.json · processor_config.json · tokenizer* · chat_template.jinja
                          google/gemma-4-26B-A4B-it, unchanged (System 2; text + image input)
adapter/                  System 1 LoRA (peft)
head.safetensors          24-slot decision head (fp32): proj.weight [24, 2816], proj.bias [24]
judge_config.json         slot layout, verbalizer ids, softcap, read-out, provenance
calibration.json          per-kind temperatures (default)
calibration_gold.json     per-kind temperatures calibrated against ground-truth answers
reports/                  Decision Index scores

License

Apache-2.0 for the adapter, head and calibration files; base model under the Gemma 4 terms (https://ai.google.dev/gemma/docs/gemma_4_license). Not affiliated with TypeSafe AI.