Claude Sonnet 5 tokenizer counts 41% more tokens per prompt

Short summary

Claude Sonnet 5 uses a new tokenizer that counts English text as 41% more tokens than Sonnet 4.6, affecting cost and context window usage. Intro pricing ($2/$10/M through Aug 31) offsets the token increase, but standard rates ($3/$15/M from Sep 1) make identical prompts ~41% more expensive. Caching mechanics remain unchanged with ~90% discount on warm reads.

• •Sonnet 5's tokenizer counts identical text as 41% more tokens than Sonnet 4.6
• •Intro pricing offsets the increase, but standard rates starting Sep 1 make it ~41% pricier
• •Caching contract unchanged; warm reads still get ~90% discount

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