Claude 3.5 Sonnet vs Grok 4.1 Fast

Claude 3.5 Sonnet

Anthropic

Claude 3.5 Sonnet, updated by Anthropic in October 2024 (originally released June 2024), is a large language model from the Claude 3.5 family that delivered strong performance in coding, reasoning, and instruction-following at its release. It supports a 200K token context window, 8K maximum output tokens, and native image understanding including screenshot analysis and document comprehension. Claude 3.5 Sonnet targets general-purpose development tasks, document analysis, and applications requiring reliable instruction following with visual input support.

Grok 4.1 Fast

xAI

Grok 4.1 Fast, released by xAI in November 2025, is a fast-response variant from the Grok 4 family featuring a 2M token context window designed for high-throughput applications. It omits thinking tokens for immediate responses, reducing latency while maintaining strong output quality. Grok 4.1 Fast targets production APIs, real-time assistants, and cost-sensitive applications requiring long-context understanding at high volume.