NVIDIA releases Nemotron 3 Ultra — a 550B open-weights model

NVIDIA's Nemotron 3 Ultra (about 550B total / 55B active, mixture-of-experts) landed as open weights — the top-scoring US open-weights model on the Artificial Analysis index at release, built for deep reasoning and research workflows.

What it means A frontier-adjacent model you can run yourself narrows the gap between hosted APIs and self-hosted stacks for serious agent work.