Claude 4 Sonnet
Claude Sonnet 4, also written Claude 4 Sonnet, was the mid-tier model of Anthropic's Claude 4 generation, released on May 22, 2025 alongside Claude Opus 4 and retired from the Claude API on June 15, 2026. It sat below Opus 4 in capability and price and was aimed at high-volume work rather than the hardest reasoning tasks. The model was trained with constitutional AI and reinforcement learning from human feedback, and supported extended thinking combined with tool use. It was used for text analysis, writing, coding assistance, mathematical reasoning, and general problem-solving. Organizations applied Claude Sonnet 4 to content production, document analysis, customer service automation, and research assistance through the Claude API; since the June 2026 retirement, requests to the claude-sonnet-4-20250514 model ID fail and those workloads have to run on a later Claude model.
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