With eye-opening clarity, Dr. Pistilli reveals what 'AI companions' really are, why people turn to them for connection, and how design choices incentivize overreliance. She shows us what it truly means to apply AI ethics in practice--pointing the way toward a more thoughtful, reflective, human-centered future.--Dr. Margaret Mitchell, Hugging Face Building AI companions that millions trust requires more than technical skill More than 987 million people now use AI chatbots, and many of them form emotional bonds with systems built to simulate companionship. This is a $15 billion market on track to reach $46 billion by 2029, and the developers building these technologies face challenges no technical manual addresses: How do you design for attachment without exploitation? How do you balance engagement with user wellbeing? Giada Pistilli, former Principal Ethicist at Hugging Face, draws on her experience building and evaluating large language models to offer structured approaches for every stage of development. From system architecture to deployment monitoring, she works through real cases of success and failure, showing how technical and ethical choices shape each other across the development lifecycle. For developers, researchers, and executives building conversational AI, this book offers practical frameworks that build ethics into the design process rather than treating them as afterthoughts. Whether you're designing new companion systems or scaling existing ones, it shows you how to build AI companions people are actually better off using.