What's new in Claude Sonnet 5
Why CEREBRO kept it
Official Sonnet 5 changelog & release notes.
The text below is an automated extraction of the article at https://simonwillison.net/2026/Jun/30/claude-sonnet-5/#atom-everything, stored verbatim in the public cerebro-vault repository. Copyright remains with the original publisher (simonwillison.net).
<p><strong><a href="https://platform.claude.com/docs/en/about-claude/models/whats-new-sonnet-5">What's new in Claude Sonnet 5</a></strong></p> Claude Sonnet 5 came out <a href="https://www.anthropic.com/news/claude-sonnet-5">this morning</a>. I always head straight for the "what's new" developer docs because they tend to have more actionable information than the official announcement post.</p> <p>Anthropic say of Sonnet 5 that "its performance is close to that of Opus 4.8, but at lower prices". The <a href="https://www-cdn.anthropic.com/9e6a1044980d8c4ed85669faf9c2a8342e2e9f1e/Claude%20So
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