Claude Sonnet is Anthropic's primary production model — the middle tier between the cheaper Haiku and the most powerful Opus. As of 2025 the current version is Claude Sonnet 4, sitting at $3/$15 per million input/output tokens with a 200K context window.
What it does best: long-document analysis (it actually uses its 200K window well, unlike some models), complex instruction following, writing quality that reads like a careful editor, and highly reliable structured output / function-calling. It's consistently the top choice for RAG systems, content pipelines, and any application where writing quality matters.
Compared to GPT-4o: slightly more expensive and slower, but meaningfully better on long-context tasks and writing. No native voice support. For teams that need to process large documents or build content-generation pipelines, Claude Sonnet is often the default. Many production systems use both: Claude for reasoning-heavy steps, GPT-4o for short tasks, classification, and voice.
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