Building a Harness with Jev
LangChain demos 'Jev,' a fast, cheap System 1 classification model for agent routing, guardrails, and evals.
“System 1 models are a class of AI models built to make fast structured decisions that software can use directly.”
A LangChain talk introduces 'Jev' from TypeSafe AI, a 'System 1' model that returns typed decisions and probabilities for classification tasks 20-200x faster and far cheaper than LLMs. It highlights practical agent-harness use cases—model routing, risky-tool-call blocking (auto mode), and online evals—via a new LangChain TypeSafe integration. The framing is a useful engineering pattern, but the specific model/vendor reads as illustrative rather than a confirmed major industry announcement.