NVIDIA Nemotron 3 Ultra

NVIDIA's 550B Mixture-of-Experts model with hybrid Mamba-Attention architecture, delivering 300+ tokens/sec with a 1M-token context window. Top-ranked US open-weights model on the Artificial Analysis Intelligence Index. Built specifically for multi-step agent loops where frontier reasoning at open-source economics actually matters. Available now on Hugging Face, OpenRouter, ModelScope, and build.nvidia.com as a NIM microservice.