Claude Opus 4.7's Silent Cost Hike: Tokenizer Changes Inflate Effective Prices 25%

Claude Opus 4.7's new tokenizer recounts the same English text as 12–45% more tokens while the rate card stays unchanged, delivering a silent 25% cost increase for typical mid-size agent calls. The update became Claude Code v2.1.142's default on May 14, automatically raising bills for developers who didn't opt in. This highlights a critical gap between published pricing and actual billing in AI APIs.