Agent Evals That Catch Regressions: LangSmith & Braintrust 2026
LLM agent evaluation is how you catch silent regressions: build eval suites in LangSmith and Braintrust that flag semantically wrong agent output before...
Chapter 1: Why Agents Regress Silently — And Why Evals Are the Only Fix You shipped an agent. It worked. Three weeks later, a support ticket lands: "The assistant used to book the meeting. Now it just asks me what time I want, forever." Nothing in your repo changed. No deploy went out. Your error rate is flat, your latency is fine, your logs are clean. And yet the agent is broken. Welcome to the defining operational problem of 2026: agents regress silently. Traditional software fails loudly — a null pointer throws, a 500 gets logged, a test goes red....