Blog
Notes from the team building jes.
What is Jev, and what are the decision models behind jes?
Jev is TypeSafe's System One decision model, the first one released publicly. It classifies instead of generating. Here's how decision models like Jev and Laya work, and how jes uses them.
Why we built jes
Agents now run for hours, with thousands of tool calls per trajectory. LLM judges are too slow and costly to check them all, and they can be prompt-injected. jes runs on decision models that are fast and cheap enough to check every step.
Add guardrails to a LangChain or LangGraph agent
A walkthrough of the jes LangChain example: one middleware that checks the user's message, every tool call, every tool result and the final reply, plus the same checks as LangGraph nodes.