Google researchers have unveiled Dreamer 4, an AI agent that mastered diamond collection in Minecraft using purely offline data—a first in reinforcement learning. By training within an ultra-accurate neural world model that simulates complex physics and object interactions, the agent outperforms predecessors while using 100x less data than OpenAI's VPT. This breakthrough demonstrates the potential for real-world applications where physical trial-and-error is impractical, such as robotics.