… This tallies with external testers’ experience of Mythos Preview’s performance, and with recent additional evaluations of the model: The UK’s AI Security Institute reports that Mythos Preview is the first model to solve both of their cyber ranges simulations of multistep cyberattacks end to end; Mo… …
… These rules should be codified in strong regulation and applied equally across frontier model developers. Government involvement in AI releases requires a durable, transparent process that gives cyber defenders and others the certainty they need about access to powerful models. …
… It’s a great model to build with. On our Super-Agent benchmark, Claude Opus 4.8 is the only model to complete every case end-to-end, beating prior Opus models and GPT-5.5 at parity on cost. …
… We did not explicitly train our models to perform this task—and yet Mythos-class models outperformed sophisticated models dedicated to protein tasks known as “protein language models” using their biological reasoning alone. …
… We make three copies of this language model: The target model is a frozen copy of the original language model that we extract activations from. The activation verbalizer AV is modified to take an activation from the target model and produce text. …
… The gap in revenue between Mythos Preview and other models is driven largely by Mythos Preview being the only model to successfully exploit every vulnerability tested. Opus 4.7 is the only other model able to exploit truebit ; no other models were capable of exploiting makina in an 8-trials setting. …
… Opus 4.6 is one of the best models out there for developers, and this model is measurably more thorough on top of that. It passed Terminal Bench tasks that prior Claude models had failed, and worked through a tricky concurrency bug Opus 4.6 couldn't crack. …
… We've additionally added guidance to our CLAUDE.md to ensure model-specific changes are gated to the specific model they're targeting. …
… For several years, our team has carefully tracked the cybersecurity-relevant capabilities of AI models. Initially, we found models to be not particularly powerful for advanced and meaningful capabilities. …
… Evaluations of the final production model show a very similar pattern of results when compared to other Claude models, and are described in detail in the Claude Opus 4.5 system card . …