Claude 3.5 Sonnet

Claude 3.5 Sonnet was the June 2024 release where a mid-tier model from a frontier lab decisively beat its own larger sibling. Claude 3 Opus from March had been the larger and more expensive offering; 3.5 Sonnet outperformed it across most benchmarks at one-fifth the price and twice the speed. The release also introduced Artifacts, a UI surface for code, diagrams, and document drafts rendered alongside the chat. Artifacts triggered a wave of product copies (canvas modes appeared in ChatGPT, Gemini, Mistral's chat product, and several open-weights wrappers within months) and established a new default expectation for what a chat interface was. On the API side, Claude 3.5 Sonnet held a leadership position on code benchmarks through most of late 2024 and became the default backend for early agentic coding tools (Cursor, Continue, Cline). The strategic story for Anthropic was that a smaller-faster-cheaper model from the mid tier could carry product surface area, which made Claude 3 Opus's slower follow-up effectively redundant; the model line skipped directly to 3.7 Sonnet in February 2025.