Claude Sonnet 4.5 vs Llama-3.1 Nemotron Ultra 253B

Claude Sonnet 4.5

Anthropic

Claude Sonnet 4.5, released by Anthropic in September 2025, is a large language model from the Claude 4.5 family that balances response quality and efficiency for coding, agentic tasks, and analytical work. It features a 200K token context window (extendable to 1M tokens in beta), 64K maximum output tokens, native image understanding, and extended thinking support. Sonnet 4.5 targets use cases that require a balance of throughput and reasoning depth, including code generation, data analysis, and multi-step agentic pipelines.

Llama-3.1 Nemotron Ultra 253B

NVIDIA

Llama-3.1-Nemotron-Ultra-253B-v1 is a 253-billion-parameter model from NVIDIA, derived from Meta's Llama 3.1 405B using neural architecture search (NAS) compression combined with NVIDIA's Nemotron post-training pipeline, which recovers and exceeds the base model's capability after structural compression. Released in April 2025, it supports toggling between a standard instruction mode and an extended reasoning mode via system prompt, allowing the same model to handle both rapid responses and deliberate chain-of-thought tasks. It is the flagship of the Nemotron family, available open-weight on HuggingFace and through NVIDIA NIM for enterprise inference.