Evals are test suites for LLM systems. They cover capability benchmarks (MMLU, HumanEval, SWE-bench), regression tests (does this prompt still work after the model upgrade), and application-specific quality bars (does the chatbot give the right answer on these 200 real customer questions).
Evals are how teams ship LLM systems with confidence. Without them, every model upgrade is a roulette spin. In 2026, eval tooling is standard: Promptfoo, Braintrust, LangSmith, and OpenAI Evals are widely used. Good eval design matters more than fancier prompts for production quality.
