Nubank implemented a custom AI-driven enterprise search solution by integrating GPT‑4o and GPT‑4o mini with fine-tuned domain-specific models and Retrieval-Augmented Generation techniques, enabling employees to access FAQs, policies, and internal documents rapidly. They also developed a call center copilot using GPT‑4o that integrates the bank’s knowledge base and chat history to provide real-time conversation summaries, next-reply suggestions, and step-by-step guidance for agents, and launched an AI assistant to handle Tier 1 inquiries. Furthermore, Nubank piloted a fraud quality assurance system using GPT‑4o vision to analyze transactions and visual data, ensuring robust fraud detection according to regulatory requirements.