TinyLettuce is a lightweight token‑classification model that flags unsupported spans in answers given context (span aggregation performed downstream). Built on the 17M Ettin encoder, it targets real‑time CPU inference and low‑cost domain fine‑tuning with synthetic data.

Trained on our synthetic dataset, this 17M variant achieves 90.87% F1 on the held‑out synthetic test set (beating large LLM judges, like GPT-OSS-120), proving the effectiveness of our domain‑specific hallucination data generation pipeline.

Model Details

Architecture: Ettin encoder (17M) + token‑classification head
Task: token classification (0 = supported, 1 = hallucinated)
Input format: [CLS] context [SEP] question [SEP] answer [SEP], up to 4096 tokens
Language: English; License: MIT

Training Data

Synthetic generation (train): ~1,500 hallucinated samples (≈3,000 total with non‑hallucinated) from enelpol/rag-mini-bioasq; intensity 0.3.
Synthetic generation (test): 300 hallucinated samples (≈600 total) held out.

Training Procedure

Tokenizer: AutoTokenizer; DataCollatorForTokenClassification; label pad −100
Max length: 4096 tokens; batch size: 8; epochs: 3
Optimizer: AdamW (lr 1e‑5, weight_decay 0.01)
Hardware: Single A100 80GB; CPU inference targeted

Results

Synthetic (domain‑specific):

Model	Parameters	Precision (%)	Recall (%)	F1 (%)	Hardware
TinyLettuce-17M	17M	84.56	98.21	90.87	CPU
TinyLettuce-32M	32M	80.36	99.10	88.76	CPU
TinyLettuce-68M	68M	89.54	95.96	92.64	CPU
GPT-5-mini	~200B	71.95	100.00	83.69	API/GPU
GPT-OSS-120B	120B	72.21	98.64	83.38	GPU
Qwen3-235B	235B	66.74	99.32	79.84	GPU

Notes: “Synthetic” metrics reflect generated data; absolute scores depend on post‑processing thresholds and domain.

Usage

First install lettucedetect:

pip install lettucedetect

Then use it:

python

from lettucedetect.models.inference import HallucinationDetector

detector = HallucinationDetector(
    method="transformer",
    model_path="KRLabsOrg/tinylettuce-ettin-17m-en-v1",
)

spans = detector.predict(
    context=[
        "Ibuprofen is an NSAID that reduces inflammation and pain. The typical adult dose is 400-600mg every 6-8 hours, not exceeding 2400mg daily."
    ],
    question="What is the maximum daily dose of ibuprofen?",
    answer="The maximum daily dose of ibuprofen for adults is 3200mg.",
    output_format="spans",
)
print(spans)
# Output: [{"start": 51, "end": 57, "text": "3200mg"}]

Citing

If you use the model or the tool, please cite the following paper:

bibtex

@misc{Kovacs:2025,
      title={LettuceDetect: A Hallucination Detection Framework for RAG Applications}, 
      author={Ádám Kovács and Gábor Recski},
      year={2025},
      eprint={2502.17125},
      archivePrefix={arXiv},
      primaryClass={cs.CL},
      url={https://arxiv.org/abs/2502.17125}, 
}

KRLabsOrg/tinylettuce-ettin-17m-en-bioasq

TinyLettuce (Ettin-17M): Efficient Hallucination Detection

Overview