Anthropic Claude 4 (Opus)

Anthropic released Claude 4 Opus in 2025, its most capable model to date, featuring a 1-million-token context window, improved reasoning chains, and constitutional AI safety mechanisms refined through over three years of research. Claude 4 set new benchmarks on law bar exams, graduate-level scientific reasoning, and long-document analysis tasks. It became the preferred AI model in legal, medical, and research professional settings due to its measured, citation-rich output style.