Guide

The new tokenizer that adds ~30% more tokens

Same rate card, higher bill: the newer models count tokens differently.

What changed

Claude Opus 4.7 and later, Fable 5, and Sonnet 5 use a newer tokenizer that produces about 30% more tokens for the same characters. Sonnet 4.6 and earlier use the old tokenizer. Because you are billed per token, the same prompt can cost ~30% more even though the per-token price is unchanged.

Why estimates undercount

Any cost estimate based on character or word counts with the old tokenizer will undercount these models. JP the Cat prices from the real token counts in your logs, so the inflation is already in the number.

Common questions

Does the new tokenizer change the per-token price?: No — the rate is the same. It changes how many tokens the same text becomes, which is what you pay for.

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