Anthropic launched Opus 5, a smaller and cheaper model compared to the recently released Fable 5, but with fewer restrictions and better performance on several benchmarks.

The model arrives just two months after Opus 4.8, while other models in the 5 series (Mythos, Fable, Sonnet) launched in June, leaving only the lightweight Haiku awaiting an upgrade.

Anthropic emphasized that Opus 5 is stronger at verifying its work and iterating carefully, citing a test where it wrote its own computer vision pipeline from an incomplete prompt.

Unlike Fable and Mythos, Opus 5 is not subject to a 30-day data retention policy, addressing privacy concerns.

However, it still has meaningful safeguards, particularly around cybersecurity: it cannot scan for vulnerabilities in a software binary but can search for vulnerabilities in source code, which Anthropic considers more defensive.

The safety classifiers are expected to engage 85% less often for Opus 5 than for Fable 5.

Anthropic also introduced a beta feature called Automatic Fallbacks, which routes requests to a less powerful model when the safety classifier triggers, so API users get a functional response instead of an error message.