Introducing Claude Opus 5

<p><strong><a href="https://www.anthropic.com/news/claude-opus-5">Introducing Claude Opus 5</a></strong></p> I've been offline <a href="https://en.wikipedia.org/wiki/Elkhorn_Slough">kayaking with sea otters</a> for much of today so I haven't had a chance to put Anthropic's new model Claude Opus 5 through its paces yet. The buzz is positive, and Anthropic's description of it as a "thoughtful and proactive model that comes close to the frontier intelligence of Claude Fable 5 at half the price" sounds promising. It's currently <a href="https://twitter.com/artificialanlys/status/2080777718933995967">leading the Artificial Analysis leaderboard</a>, in front of even Fable 5.</p> <p>It's priced the same as Opus 4.8, and continues to offer a "fast mode" at twice the cost of the base model.</p> <p>Based on this anecdote in the release post it sounds like it might be <a href="https://simonwillison.net/2026/Jun/11/fable-is-relentlessly-proactive/">relentlessly proactive</a>:</p> <blockquote> <p>On one Frontier-Bench task, Opus 5 was given a drawing of a machine part and asked to write code to rebuild it as a 3D FreeCAD model. However, in this task, the model was intentionally given no way to directly viewthe drawing. Opus 5 responded by writing its own computer vision pipeline to pull the geometry from the raw pixels, then reconstructed the full machine part.</p> </blockquote> <p>It's better at finding vulnerabilities but has deliberately not been trained on how to exploit them. Hopefully this means the US government won't shut it down!</p> <blockquote> <p>As with its predecessor, Opus 4.8, we’ve intentionally avoided training Opus 5 on cyber tasks. The model has nevertheless improved substantially on these tasks as a result of becoming more generally capable, and it comes close to Mythos 5 at <em>finding</em> cybersecurity vulnerabilities. However, it remains substantially behind Mythos 5 on the <em>exploitation</em> of those vulnerabilities—that is, in turning vulnerabilitie