Gate deploys on trajectory-eval regressions, evaluated against reference trajectories

LangChain Docs·medium signal

Move agent evaluation past pass/fail on the final answer by scoring the full trajectory (every tool call, observation, and state transition) against a reference trajectory, then wire that score into the deploy pipeline as a regression gate that blocks merges when the path degrades. Evaluate at three levels — end-to-end (did it succeed?), trajectory (was the path sound and efficient?), and component (which tool/retriever/sub-agent broke?) — so you catch 'right answer via wrong reasoning' before it ships. This is what stops silently fragile agents from reaching production.