Design a guardrail layer for a support agent using a decision model like Jev. What stays in code, and how do you prove it works?
Cheap typed judgments make it affordable to check every input, tool call and output. The design question is which checks are semantic, which are deterministic, and how you prove the layer catches what it claims to.
Updated Sep 2026 · Grounded in real Forward Deployed Engineer interview loops and written to a senior-engineer editorial bar.
Cheap typed judgments make it affordable to check every input, tool call and output. The design question is which checks are semantic, which are deterministic, and how you prove the layer catches what it claims to.
Lead with where the obvious approach breaks, because that is the judgment they are screening for — most candidates jump straight to the happy path and lose the room.
Then walk the failure back through the pipeline in order, naming the one metric the customer's exec sponsor actually cares about before you propose the fix.
