Why high: an exact fingerprint shared with 4 models that declare the same family, without a second signal of a different kind yet.
Anthropic: Claude Sonnet 4 is Anthropic's model. Its measured tokenizer sits with the Claude group, which is evidence that it builds on the Claude tokenizer. Tokenizer reuse is normal engineering, open vocabularies travel between labs, and this says nothing against Anthropic's authorship of the model itself.
| We checked | What we found | Where it came from |
|---|---|---|
| How it counts tokens | Counts every one of the 50 test strings exactly like 4 other models | tk_2d06485c |
| How its API is set up | A combination of settings no other listing in the catalogue uses | api_72fff635 |
| How much it can read and write | Reads up to 200,000 tokens at once, writes up to 64,000 | its own listing |
| Whether it thinks before answering | Reasons when asked to | its own listing |
| Who served our requests | Amazon Bedrock | we measured it, 5 October 2026 |
Click a row to open the full comparison.
We sent Anthropic: Claude Sonnet 4 fifty short pieces of text and recorded what each one cost it in tokens. The bars below are those costs. Two models built on the same tokenizer produce the same bars; a model built on a different one produces a different set, which is what makes this a fingerprint.
Overhead subtracted: 7 prompt tokens.
Claude Sonnet 4 significantly enhances the capabilities of its predecessor, Sonnet 3.7, excelling in both coding and reasoning tasks with improved precision and controllability. Achieving state-of-the-art performance on SWE-bench (72.7%),...
Supported parameters
include_reasoningmax_tokensreasoningstoptemperaturetool_choicetoolstop_ktop_p
defaults: {"temperature":null,"top_p":null,"top_k":null,"frequency_penalty":null,"presence_penalty":null,"repetition_penalty":null}
