🤖 AI / ML

Claude Sonnet 5 有哪些新功能What's new in Claude Sonnet 5

simonwillison.net·2026-06-30 节选正文

Anthropic 最新发布了 Claude Sonnet 5 模型。其性能表现接近 Opus 4.8，但提供了更具性价比的定价策略。开发者可以通过官方开发者文档获取比新闻稿更具实操价值的详细信息。这标志着高端模型能力的进一步下放与成本优化。

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Simon Willison

30th June 2026 - Link Blog

What's new in Claude Sonnet 5 (via) Claude Sonnet 5 came out this morning. I always head straight for the "what's new" developer docs because they tend to have more actionable information than the official announcement post.

Anthropic say of Sonnet 5 that "its performance is close to that of Opus 4.8, but at lower prices". The system card helps explain how they were able to release the model without being blocked by the US government:

Sonnet 5 is significantly less capable at cyber tasks than Mythos 5: its safeguards are thus similar to those we apply to Opus 4.7 and Opus 4.8 (models that are more capable than Sonnet 5 but much less capable than Mythos 5).

Of note from the "what's new" API changes:

Sampling parameters temperature, top_p, top_k are no longer supported.

It has a 1 million token context window and 128,000 maximum output tokens.

It features "the same set of tools and platform features as Claude Sonnet 4.6"

Adaptive thinking is on by default, unless you specify "thinking": {type: "disabled"}.

The pricing is the same as Sonnet 4.6: $3/million input, $15/million input, with an introductory discount to $2/$10 until 31st August. But...

The model has a new tokenizer, where "The same input text produces approximately 30% more tokens than on Claude Sonnet 4.6." - effectively a 30% price increase.

I used my Claude Token Counter tool to try out the new tokenizer. Here are my results for several larger documents:

So the new token is roughly 1.4x times more expensive for English, 1.33x for Spanish, 1.28x for Python code and effectively the same cost for Simplified Mandarin.

Here's the pelican. It's nothing to write home about. Sonnet 5 thinks it looks like a goose.

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