Artificial Intelligence
The initial Claude 4 family: first quality tests
Anthropic released Claude Opus 4 and Claude Sonnet 4 on 22 May 2025, the first major naming jump since the 3.5 series. Claude 4 reasons noticeably better over long programming tasks: multi-hour refactors that previously stalled without a human nudge now run further alone, and the family targets agentic, multi-step flows.