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

Claude Mythos achieved an 82% score on the terminal bench, an increase from the previous 65%.

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

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

Scale AI benchmarked top models (Claude, Gemini, OpenAI) on real multi-file software engineering tasks using actual production-grade code, finding they solved only 20-30% of tasks.

On Humanity's Last Exam, Claude Mythos improved its score from 40% to 56.8%, and to 64.7% when given tools.