Claude 4.7's new tokenizer inflates text 1.325x on average — 80-turn Code sessions now cost 20-30% more
·claudecodecamp.com
A measurement study published April 17 on claudecodecamp compared Anthropic's Claude 4.6 and 4.7 tokenizers on identical content using Anthropic's free /v1/messages/count_tokens endpoint. Weighted across seven real Claude Code workloads, the 4.7 tokenizer produces 1.325x more tokens than 4.6 — CLAUDE.md files run 1.445x, user prompts 1.373x, code diffs 1.212x, terminal output 1.291x. The root cause is that English chars-per-token dropped from 4.33 to 3.60; TypeScript dropped from 3.66 to 2.69 — the new tokenizer just slices text finer. Net effect on an 80-turn Claude Code session: 4.6 cost ~$6.65 vs 4.7 cost ~$7.86-$8.76, roughly 20-30% higher at identical list prices.
anthropicclaudetokenizercostbenchmark
Why it matters
Tokenizer inflation is the hidden variable in 'list price vs actual bill' comparisons — most enterprise AI budgeting spreadsheets assume constant tokens-per-word across model generations. A 1.325x multiplier means every Anthropic customer who upgraded from Opus 4.6 to 4.7 at stated pricing is effectively paying 32% more for the same workload before any model-quality differences factor in. Expect Anthropic to either cut 4.7 per-token pricing, publish an official tokenizer-efficiency note, or face a second enterprise-visible story (after the NYT Connections regression) undermining the 4.7 release narrative.
Impact scorecard
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Coverage7 outlets · 1 tier-1
claudecodecamp, Hacker News, TLDR AI
X / Twitter4,800 mentions @simonw · 3,400 likes
Reddit1,200 upvotes r/ClaudeAI
r/ClaudeAI, r/singularity, r/LocalLLaMA
Trust check
medium
Independent blogger with reproducible methodology using Anthropic's own token-count endpoint, posted on HN front page. Numbers are verifiable by anyone with API access. Not yet corroborated by Anthropic — treat efficiency multiplier as directionally accurate, exact deltas subject to workload mix.
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