Anthropic's Claude Mythos model is a much bigger, more expensive, slower, but more powerful model compared to Opus.

Anthropic's Mythos LLM is so capable at computer security tasks that Anthropic did not release it publicly, instead granting access only to critical software makers.

Computationally expensive AI models like Claude Mythos can only be used effectively by individuals who spend significant amounts on tokens.

Anthropic released a new AI model named Mythos, which is an upgrade from previous models like Sonnet, Opus, and Haiku.

On SWEBench Pro, Claude Mythos achieved a 78% score, while Opus previously scored 53% and GPT 5.4 scored 57.7%.

Anthropic will not widely release its Claude Mythos Preview model because of its potential to cause harm if misused.