Opus-class model

An Opus-class model refers to one at the top tier of size and intelligence among Anthropic's Claude models. Just as a coffee shop has size grades like tall, grande, and venti, Claude models are also split into tiers ranging from light and fast to heavy and powerful — and the highest tier is called Opus-class.

The important thing is that Opus-class doesn't necessarily mean 'the newest model available right now.' Over time, Anthropic sometimes releases tiers that come after Opus and are even more powerful. So the phrase Opus-class is also used to describe a certain level of performance, not a specific generation of model.

That means saying a user is only allowed up to Opus-class could mean the latest top-tier model is still restricted, while access is opened up to one tier below it — which is still quite powerful.

In the article, Anthropic opened up free access to Claude for scientists, but stated that "biology and chemistry researchers can only use models up to Opus-class for the time being." The latest model, Claude Fable, blocks specialized biology and drug-related queries due to the risk of misuse in bioweapon development, while allowing free use of the earlier, Opus-class tier. Here, Opus-class is used not to mean 'newest,' but to mean 'the upper limit of allowed access.'