Expanding Project Glasswing
… In the future, frontier model releases will become increasingly high-stakes. …
Users will find Opus 4.8 to be a modest but tangible improvement on its predecessor. There’s still more to be done: we’re working on developing and releasing models that provide many of the same capabilities as Opus at a lower cost. Not only that, but we plan to release a new class of model with even higher intelligence than Opus. As part of Project Glasswing, a small number of organizations are currently using Claude Mythos Preview for cybersecurity work. Models of this capability level require stronger cyber safeguards before they can be generally released. We’re making swift progress on dev
Introducing Claude Opus 4.8… In the future, frontier model releases will become increasingly high-stakes. …
… 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… …
… There’s still more to be done: we’re working on developing and releasing models that provide many of the same capabilities as Opus at a lower cost. Not only that, but we plan to release a new class of model with even higher intelligence than Opus. …
Interpretability A “diff” tool for AI: Finding behavioral differences in new models Mar 13, 2026 Read the paper Every time a new AI model is released, its developers run a suite of evaluations to measure its performance and safety. …
… We also release an interactive frontend for exploring NLAs on several open models through a collaboration with Neuronpedia . We have also released our code for other researchers to build on. …
… We stated that we would keep Claude Mythos Preview’s release limited and test new cyber safeguards on less capable models first. …
… For example, an independent assessment of Moonshot’s Kimi K2.5 published in April found that the model failed to refuse CBRN-related requests at a far higher rate than US frontier models. Compounding the problem, labs in China often release dual-use capable models as open-weight. …
… A few weeks before we released Opus 4.7, we started tuning Claude Code in preparation. Each model behaves slightly differently, and we spend time before each release optimizing the harness and product for it. …
… A step forward on safety As we state in our system card , Claude Opus 4.5 is the most robustly aligned model we have released to date and, we suspect, the best-aligned frontier model by any developer. …
… This includes creating public goods—like model benchmarks, datasets, and knowledge graphs—to ensure AI tools for math tutoring, college advising, and curriculum design are effective. The first of these will be released publicly later this year. …