It is one thing if I, as the user, choose to down-level but Claude shouldn't do this on its own.

It's a shame because I was really looking forward to use it specifically to find potential security holes in my own software.

That being said, Opus 4.7/4.8 have been quite useful already, especially for finding things in the harder to test, non-happy paths.

If I recall, Fable 5 is supposed to be basically Mythos which falls back to Opus 4.8 when dealing with cybersecurity. I wonder if that also includes "finding bugs that could lead to security exploits".