Claude Sonnet 5 ships with 1M token context and new tokenizer that increases costs 30-40% for English text
Anthropic released Claude Sonnet 5 with a 1 million token context window and 128,000 token maximum output. The model removes traditional sampling parameters and introduces a new tokenizer that generates approximately 30% more tokens than Sonnet 4.6 for the same English text—effectively a significant price increase despite unchanged nominal rates of $3/million input and $15/million output tokens.