Claude Sonnet 5's New Tokenizer Inflates Costs by 41%

Anthropic's Claude Sonnet 5 uses a new tokenizer that generates 41% more input tokens for the same English text, effectively raising costs despite a lower per-token price. At standard rates, identical prompts cost 41% more than on Sonnet 4.6, and context windows fill faster. The introductory pricing of $2/$10 per million tokens runs through August 31, 2026.