<p id="speakable-summary" class="wp-block-paragraph">On Friday, Anthropic launched its Opus 5 model, the newest version of its long-standing heavyweight model. While smaller than Fable 5, the model will be both cheaper and less restrictive than Fable, likely making it preferable in most use cases. </p>
<p class="wp-block-paragraph">Notably, Opus 5 actually outperforms Fable 5 on a number of benchmarks included in the announcement.</p>
<p class="wp-block-paragraph">Opus 5 is launching only two months after Opus 4.8, which became available on May 28. Mythos 5, Fable 5, and Sonnet 5 all launched in June, leaving only the lightweight Haiku model still waiting for an upgrade to the 5 series.</p>
<p class="wp-block-paragraph"><a href="https://www.anthropic.com/news/claude-opus-5" target="_blank" rel="noreferrer noopener nofollow">In a post announcing the new model</a>, Anthropic emphasized that Opus 5 was “much stronger at verifying its work and iterating carefully until it succeeds,” citing benchmark testing, in which Opus 5 wrote its own computer vision pipeline in response to an incomplete prompt, among other examples.</p>
<p class="wp-block-paragraph">Crucially, Opus 5 is also free from many of the restrictions that have dogged Fable since its release. Like its predecessor, Opus 5 is not subject to <a href="https://support.claude.com/en/articles/15425996-data-retention-practices-for-covered-models" target="_blank" rel="noreferrer noopener nofollow">the 30-day data retention policy</a> that covers Fable and Mythos, which had raised concerns among some privacy-conscious users.</p>
<p class="wp-block-paragraph">There are still meaningful safeguards on Opus, particularly around cybersecurity tasks like exploit generation and penetration testing. For instance, Opus 5 safeguards prevent it from being used to scan for vulnerabilities in a software binary, although it is permitted to search for vulnerabilities in source code, since the latter task is more likely to be used for defensive purposes.</p>
<p class="wp-block-paragraph">Broadly, Anthropic expects these classifiers to engage 85% less often for Opus 5 than they will for Fable 5, a reflection of the lighter touch given to the less capable model.</p>
<p class="wp-block-paragraph">Anthropic is also rolling out a new tool to <a href="https://techcrunch.com/2026/07/23/how-ai-guardrails-are-impeding-the-work-of-offensive-cybersecurity-researchers/" target="_blank" rel="noreferrer noopener">make the safeguards less disruptive</a> when they do engage. Users can now opt in to a beta feature called Automatic Fallbacks, which will automatically route requests to a less powerful model when a prompt triggers the safety classifier. The result is that API users with the setting engaged will get a functional response instead of an error message.</p>
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