What's new in Claude Sonnet 5

According to Simon Willison, Anthropic released Claude Sonnet 5. The company claims it delivers near Opus four point eight performance at lower prices, but there's a catch. While the official pricing remains three dollars per million input tokens and fifteen dollars per million output tokens, Sonnet 5 introduces a new tokenizer that generates approximately thirty percent more tokens than Sonnet four point six for the same input. The impact varies by language: English text becomes roughly one point four times more expensive, Spanish about one point three three times, Python code one point two eight times, and Mandarin Chinese effectively unchanged. Other technical changes include a one million token context window, one hundred twenty-eight thousand maximum output tokens, and adaptive thinking enabled by default. For developers, the practical takeaway: the price per token stayed flat, but you'll need more tokens.

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