Haiku. Sonnet. Opus. Anthropic's model names follow a deliberate poetic arc - each one representing a larger, more ambitious form of literary work. Now observers are debating what name logically comes next.
The candidate generating discussion is Mythos. The reasoning: after Opus, you can't call the next model Magnum Opus - that phrase means the greatest work a person creates, which grammatically implies nothing follows. The naming tier dead-ends. Mythos sidesteps this. Myths are narrative and expansive, operating on a scale beyond any individual poem or musical composition. They're also culturally foundational in a way that a single opus isn't.
This is entirely speculation. Anthropic has made no announcement, and the Mythos theory comes from community observation rather than any leak or official signal. Anthropic hasn't confirmed the existence of a model beyond Claude Opus 4, let alone named it.
What makes the speculation worth noting is that Anthropic's naming has been unusually coherent from the start. Haiku and Sonnet launched as the faster, cheaper tier. Opus was the flagship. The internal logic is real, which means anyone naming a successor to Opus does face a genuine constraint. Whether Mythos is their answer or whether they abandon the poetry framework entirely - going numerical, geographic, or something else entirely - is a decision only the brand team knows.
For now, file it as an interesting corner of model-naming architecture that becomes relevant if and when Anthropic releases something positioned above Opus.