leobitz/jev-berta-base-zeroshot-classifier

JevBerta

JevBerta is a small Python package for running a variable-choice zero-shot classifier over structured decision tasks.

What It Does

JevBerta scores a set of candidate answers conditioned on:

• a context string
• a query string
• a variable-length list of candidate choices

It also exposes a JEV-style interface where:

• state is treated as the context
• each question's instructions is treated as the query
• each question's criteria defines the candidate labels

All supported question types are reduced to classification over the provided criteria.

Install

pip install git+https://github.com/leobitz/jev-berta.git

Quick Start

from jev_berta import JevBerta

model = JevBerta.from_pretrained("leobitz/jev-berta-base-zeroshot-classifier")

result = model.predict(
    context="Customer says they were billed twice for the same order.",
    query="What is the best category?",
    choices=["billing", "shipping", "technical"],
)

print(result["choice"])
print(result["probabilities"])
print(result["scores"])

probabilities and scores are both softmax-normalized probabilities over the provided choices.

JEV-Style API

from jev_berta import JevBerta

model = JevBerta.from_pretrained("leobitz/jev-berta-base-zeroshot-classifier")

payload = {
    "state": "A customer says they were charged twice for the same order, already emailed support twice without getting a reply, and now wants the duplicate charge refunded immediately.",
    "questions": {
        "refund_requested": {
            "type": "noul",
            "instructions": "Is the customer explicitly asking for a refund?",
            "criteria": {
                "true": "The customer clearly wants money returned or a charge reversed.",
                "false": "The customer is not asking for a refund."
            }
        },
        "owner_team": {
            "type": "choice",
            "instructions": "Which team should take ownership of this case?",
            "criteria": {
                "billing": "Handles duplicate charges, refunds, invoices, and payment disputes.",
                "support": "Handles follow-up communication and general customer assistance.",
                "technical": "Handles bugs, outages, and product malfunctions.",
                "other": "Use when none of the main teams fit the case."
            }
        },
        "priority": {
            "type": "score",
            "instructions": "How urgent is this case?",
            "criteria": ["Low", "Medium", "High"]
        }
    }
}

result = model.predict_jev(payload)
print(result["predictions"])

Architecture

The runtime package is centered on JevBerta in src/jev_berta/jevberta.py.

Input formulation

For each candidate label, the model builds a pair of texts:

• sequence A: Context: ...\nQuery: ...
• sequence B: Candidate: ...

Each candidate is encoded independently by the Transformer encoder, then grouped back into a candidate set for joint reasoning.

Encoder backbone

JevBerta uses a pretrained Hugging Face encoder loaded through transformers.AutoModel. The exported checkpoint configuration determines:

• base encoder model name
• maximum sequence length
• number of set-attention layers
• number of set-attention heads
• feed-forward expansion factor
• dropout

Candidate-set reasoning

After encoding, the model:

1. takes the CLS representation for each candidate pair
2. reassembles candidates into a batch_size x num_choices x hidden_size tensor
3. applies layer normalization
4. runs several candidate-set self-attention blocks

Each candidate-set block contains:

• multi-head self-attention across the candidate dimension
• residual connections
• layer normalization
• a feed-forward network

This lets the model score each option while conditioning on the full set of alternatives, rather than treating each option fully independently.

Scoring head

A small MLP converts each candidate state into a scalar logit. A masked softmax over the candidate dimension produces the final probability distribution.

Public APIs

The package exposes two main inference calls:

• predict(context, query, choices)
• predict_jev(payload)

predict_jev is a thin adapter over predict that:

• maps state -> context
• maps instructions -> query
• converts criteria into the candidate list
• returns one prediction block per question key

Accuracy Snapshot

Dataset	JevBerta	OpenJev	kev-0.8b	laya
model size	198M	435M	435M	435M
validation	0.854	0.556	0.713	0.503
ood_eval	0.627	0.391	0.640	0.431
truthfulqa	0.480	0.252	0.481	0.132
mmlu	0.276	0.327	0.458	0.274
type_decision	0.374	0.390	0.501	0.332

Demo Notebook

See demo/demo_usage.ipynb for a runnable walkthrough that loads leobitz/jev-berta-base-zeroshot-classifier and demonstrates both APIs.