What's new in Claude Sonnet 5 (simonwillison.net)

Anthropic has launched Claude Sonnet 5, a new AI model that promises performance levels comparable to Opus 4.8 but at a lower cost, addressing accessibility for developers in the AI/ML community. Notably, Sonnet 5's design includes safeguards making it less capable in cyber tasks compared to more advanced models like Mythos 5, allowing it to navigate regulatory concerns effectively. Key updates include an expanded context window of 1 million tokens and a maximum output of 128,000 tokens, along with a new tokenizer that produces approximately 30% more tokens than its predecessor, Claude Sonnet 4.6. This change translates to a 30% increase in effective pricing for users, although the introductory pricing remains competitive at $2-$3 per million inputs. Additionally, API updates remove support for certain sampling parameters, while adaptive thinking is enabled by default, positioning Sonnet 5 as a versatile tool for developers looking to leverage AI more efficiently.