They’re not giving any details about why or how.

If they were the moral people they say they are, and believed what they say about it killing humanity they would stop unilaterally. These are the “rationalists” but they act like the fundamentalist church I grew up in. Every fact serves the same conclusion.

Yes, they are.

https://www.anthropic.com/threat-intelligence-report-septemb...

> Biological misuse is one of the most serious risks of frontier AI models. It has long been a concern that AI models might one day reach the level of capability where they can help to make existing pathogens more dangerous—or create entirely new ones. Without the correct safeguards, such capabilities could have catastrophic consequences.

Results from evaluations of older models (for example Claude Opus 4 and Claude Sonnet 4.5, from 2025) clearly showed that these models were well below the threshold where they could meaningfully assist a sophisticated user in carrying out dangerous biological research. As a result, safeguards on these models were less stringent, directed mostly at preventing access to content that might uplift novices in recreating known bioweapons. But for today’s models—which are capable of assisting in a range of complex scientific research tasks—the evidence is no longer certain, and we cannot make that same assurance. For this reason, and out of an abundance of caution, we have launched recent models (most notably Claude Fable 5) with stronger safeguards that restrict access to a wide range of dual-use biological research queries.

...

Here, we present five case studies of actors using our models in ways that could support biological weapons development. These examples are illustrative of the kinds of tasks to which our models are put, and the often-difficult judgements we have to make when assessing whether or not a given biological use is dangerous. They also convey that we encounter what would otherwise be non-public insight into the risks associated with biological misuse from AI