Claude Opus 4 is Anthropic's breakthrough coding and agent model released in May 2025, setting new standards for sustained performance on complex, long-running tasks. It leads on SWE-bench (72.5%) and Terminal-bench (43.2%), and can handle agentic workflows spanning thousands of task steps continuously for hours without degradation. As a hybrid model, it offers both near-instant responses and extended thinking for deeper reasoning, with parallel tool use and improved instruction memory.