Claude 3 Sonnet
Claude 3 Sonnet was the mid-tier model in Anthropic's Claude 3 family, released in March 2024 and retired from the Claude API on July 21, 2025. It sat between Claude 3 Haiku and Claude 3 Opus, trading some capability for lower cost per token and faster responses. The model was trained with constitutional AI and reinforcement learning from human feedback, the same alignment approach used across the Claude 3 family, and was applied to text analysis, content creation, coding assistance, mathematical reasoning, and conversational interfaces.
While it was available, organizations used Claude 3 Sonnet for content automation, customer service, document analysis, research assistance, and reporting, where cost per token mattered as much as raw capability. Those deployments ran through the Claude API; after the July 2025 retirement, requests to the claude-3-sonnet-20240229 model ID fail and the workloads have to run on a later Claude model.
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