Stop Vibe-Checking Your AI App: A Practical Guide to Evals

Most AI demos look great on Friday afternoon. You try five prompts. The model answers smoothly. The summary is crisp. The chatbot sounds helpful. The extraction workflow pulls the right fields out of the sample PDF. Everyone nods. Someone says, "This is basically ready." Then real users arrive... They paste messy inputs. They ask ambiguous questions. They upload documents with weird formatting. They use company slang your test prompts never included. They click "regenerate" six times. They get a