How to Design Offline Eval Gates That Actually Catch Regressions Before Release

A practical guide to implementing offline release gates, with a reference implementation. Article 2 in a series on eval loops for production LLM systems. A release gate is not a benchmark report. It is a decision system. Most teams I’ve seen treat it like a scoreboard instead. They run a dataset, watch one number move, and call that release discipline. The problem shows up later, in production, when a candidate that looked flat on the headline metric turns out to have quietly broken behavior on the cases that matter most.