NVIDIA Nemotron 3 Ultra (free)

Nemotron 3 Ultra is NVIDIA's largest open reasoning and agentic large language model, featuring 550B total parameters with 55B active via a hybrid Transformer/Mamba mixture-of-experts architecture. It is designed for long-running agent workflows such as planning, tool use, coding, and deep research, supporting up to 1M-token context windows. Source: supabase.