Still one model. Still one request. Now with spans. Sound on.
Open Foundation Routing Models. Bringing span-level decisions to System One.
Vela 2.0 is a family of open models for routing, safety checks and span-level decisions. Define your options, labels and rubrics at request time; get structured answers with probabilities and character-offset spans through one SystemOne-compatible interface.
Semantic Router can now verify grounded responses with a generative span detector served by vLLM. The new endpoint detector backend runs LettuceDetect v2 against every fact-checkable answer: unsupported spans are located to the character, typed against a hallucination taxonomy, and explained — in one call, before the response reaches the user.
The models come out of a joint paper between KR Labs and the Semantic Router team, Beyond Document Grounding: Span-Level Hallucination Detection over Code, Tool Output, and Documents (arXiv:2607.00895). This post walks through the paper — the benchmark, the taxonomy, the models, and what they score — and then through the integration that puts the detector into the serving stack.
