Vela Halu
Vela Halu finds answer spans unsupported by the supplied evidence, for grounded answers and response verification.
307M parameters · Supported input length: 8,192 tokens, including special tokens.
Labels are supported (0) and hallucinated (1). Spans use Unicode character offsets in the answer. Evidence support is distinct from real-world factual truth; an empty result does not guarantee correctness.
Answers requiring arithmetic or multi-step reasoning beyond explicit context may be incorrectly flagged.
Evaluation
Reported scores on the 10,698-example fixed evaluation set. Each cell is Vela Halu / LettuceDetect, on a 0-100 scale; higher is better. Bold Vela scores exceed the paired baseline.
LettuceDetect scores are from its published model card, rounded to three decimal places on the 0-1 scale before conversion.
Span metrics measure character overlap; example F1 measures whether an answer contains any hallucinated span. IoU is mean character-set intersection over union. Vela evaluation uses bfloat16, an 8,192-token limit, only_first pair truncation, and token scores strictly above 0.5. Full scores include all source groups and truncation statistics.
Quick start
With PyTorch and Transformers 4.57.6:
Keep the complete evidence, request and answer within the supported input length. The example checks this limit before inference.
Explore the Vela model collection