---
license: mit
base_model: MoritzLaurer/DeBERTa-v3-large-mnli-fever-anli-ling-wanli
datasets:
  - wandb/RAGTruth-processed
language:
  - en
pipeline_tag: text-classification
library_name: transformers
tags:
  - hallucination-detection
  - groundedness
  - rag
  - nli
  - fact-checking
metrics:
  - f1
---

# attest-grounding-large

A 0.4B NLI model fine-tuned to detect **ungrounded claims in RAG answers** — i.e.
sentences an LLM stated that the retrieved sources don't actually support. On the
RAGTruth benchmark it **matches a Claude Opus LLM-as-judge on F1 (0.75 vs 0.76)**
and beats it on precision, at **$0 vs ~$12.73 per 1,000 checks**.

Grounding is framed as Natural Language Inference: a claim is supported if a source
*entails* it. The model keeps the base 3-class NLI head (entailment / neutral /
contradiction) — read the **entailment probability** as the grounding score.

Full project, benchmark harness, and methodology: **https://github.com/Metry630/attest**

## Results — RAGTruth (500 held-out test examples, zero train/test source overlap)

| System | Size | Acc | Precision | Recall | F1 | Cost / 1k |
|---|---|---|---|---|---|---|
| base DeBERTa-MNLI | 0.18B | 0.60 | 0.48 | 0.89 | 0.63 | $0 |
| Vectara HHEM-2.1-open | 0.1B | 0.72 | 0.59 | 0.88 | 0.71 | $0 |
| off-the-shelf DeBERTa-large-MNLI | 0.4B | 0.60 | 0.49 | 0.92 | 0.64 | $0 |
| **this model (fine-tuned)** | **0.4B** | **0.81** | **0.73** | 0.78 | **0.75** | **$0** |
| Claude Opus 4.8 (LLM judge) | — | 0.78 | 0.64 | 0.92 | 0.76 | $12.73 |

The gain is from fine-tuning, not size: the *same* 0.4B architecture off-the-shelf
scores 0.64 (identical to the 0.18B base). Consistent with published work
(prompt-based GPT-4-turbo ≈ 0.63, LettuceDetect-large ≈ 0.79).

## Usage

```python
import torch
from transformers import AutoTokenizer, AutoModelForSequenceClassification

tok = AutoTokenizer.from_pretrained("Metry63/attest-grounding-large")
model = AutoModelForSequenceClassification.from_pretrained("Metry63/attest-grounding-large").eval()
ent_idx = next(i for i, l in model.config.id2label.items() if "entail" in l.lower())

source = "The Eiffel Tower was completed in 1889 and stands 330 metres tall in Paris."
claim  = "The Eiffel Tower is the tallest building in the world."

with torch.inference_mode():
    logits = model(**tok(source, claim, return_tensors="pt", truncation=True, max_length=512)).logits
supported = logits.softmax(-1)[0][ent_idx].item()
print(f"grounded (entailment) prob: {supported:.2f}")   # ~0.0 here -> not supported
```

For the full response-level pipeline (sentence splitting, chunk retrieval, and
aggregation), use the [`attest`](https://github.com/Metry630/attest) library.

## Training

- **Base:** `MoritzLaurer/DeBERTa-v3-large-mnli-fever-anli-ling-wanli` (3-class NLI).
- **Data:** ~112k sentence-level examples derived from RAGTruth's character-level
  hallucination spans — a sentence overlapping an *evident-conflict* span is labeled
  `contradiction`, a *baseless-info* span `neutral`, otherwise `entailment`.
- **Setup:** class-weighted loss (grounded sentences dominate), early stopping.
- Evaluated on the RAGTruth `test` split, which shares **zero source passages** with
  `train`.

## Limitations

- The LLM judge has higher **recall** (0.92) — it catches more hallucinations, with
  more false positives. This model is the more *precise* detector, not the most
  *sensitive* one.
- Not SOTA — purpose-built LettuceDetect-large (0.79) is higher.
- English only; evaluated on RAGTruth (news summary, QA, data-to-text). Behavior on
  other domains is untested.

## Credit

Builds on the NLI-as-factual-consistency line (TRUE, MiniCheck, AlignScore,
LettuceDetect). Benchmark: [RAGTruth](https://arxiv.org/abs/2401.00396).