Every technology wave eventually gets the book that names it. For the generation of developers building on top of foundation models, gluing GPTs and Claudes into products with prompts, retrieval pipelines and evaluation harnesses, that book is Chip Huyen's AI Engineering: Building Applications with Foundation Models. Published by O'Reilly at the start of 2025, it became the house textbook of a job title that barely existed two years earlier, and it remains the first thing worth handing to anyone who asks how this work actually gets done.