Claude 4 Opus
Claude Opus 4, also written Claude 4 Opus, was the most capable model of Anthropic's Claude 4 generation, released on May 22, 2025 and retired from the Claude API on June 15, 2026. It was positioned above Claude Sonnet 4 for complex reasoning, coding, and long-running agentic tasks, and was the first Anthropic model deployed under the company's ASL-3 protections. The model was trained with constitutional AI and reinforcement learning from human feedback, and supported extended thinking combined with tool use. Typical uses were analysis, long-form writing, coding assistance, and mathematical problem-solving. Organizations applied Claude Opus 4 to decision support, research assistance, document analysis, and planning; since the June 2026 retirement, requests to the claude-opus-4-20250514 model ID fail and those workloads have to run on a later Claude model.
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