Ai2's Tülu 3 405B, a massive open-source AI model, has outperformed DeepSeek V3, GPT-4o, and Llama 3.1 405B on key benchmarks like PopQA, GSM8K, and MATH, proving that open models can rival top proprietary systems. Trained using 256 GPUs in parallel, Tülu 3 405B leverages advanced reinforcement learning techniques like RLVR to enhance accuracy in math, reasoning, and instruction-following. With full transparency, permissive licensing, and detailed training data, Ai2's breakthrough marks a major milestone in the ongoing AI arms race, challenging corporate dominance in artificial intelligence development.