Claude 3 Opus
Claude 3 Opus was the most capable model in Anthropic's Claude 3 family, released in March 2024 and retired from the Claude API on January 5, 2026. It was positioned above Claude 3 Sonnet and Claude 3 Haiku and was used for complex reasoning, long-form writing, and multi-step problem-solving. The model was trained with constitutional AI and reinforcement learning from human feedback, the alignment approach Anthropic applies across the Claude line. Anthropic did not publish parameter counts or architectural details for the Claude 3 models.
While it was available, organizations used Claude 3 Opus for decision support, research assistance, document analysis, and planning work that called for the strongest model in the Claude 3 line. Those deployments ran through the Claude API; after the retirement, the claude-3-opus-20240229 model ID is no longer generally available and those workloads have to run on a later Claude model.
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