Introducing Claude Sonnet 5

It can perform some routine, non-harmful cyber tasks, but on evaluations testing potentially dangerous cyber skills, such as developing software exploits, it shows substantially poorer performance than models such as Opus 4.8 and Mythos 5.Anthropic

2 Sonnet 5 is an upgrade to Sonnet 4.6, but it uses an updated tokenizer that changes how the model processes text to improve performance (this is similar to the tokenizer change we introduced with Claude Opus 4.7).Anthropic

From today, Claude Sonnet 5 is available across all plans: it is the default model for Free and Pro plans, and is available to Max, Team, and Enterprise users.Anthropic

The 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).Simon Willison

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"}.Simon Willison

Of note from the "what's new" API changes: - Sampling parameters temperature, top p, top k are no longer supported.Simon Willison