What's dangerous is Opus 4.8's proclivity to create backdoors and no-op critical security code. Claude Web counted 27 instances of this I had cataloged over the last few months, and Fable 5 found more. Fable 5 may do this too, but I didn't get a long enough chance to test it since it kept downgrading to Opus 4.8 on every prompt saying, "This model has safety measures that flagged something in this session", even when asking Fable 5 to fix the security issues it found that Opus 4.8 created. You have a model that presumably can write secure code and identify security vulnerabilities, but as a security measure, they say we're going to force you to use a model that creates security holes. This is backwards. Considering the scale, Opus 4.8 is creating more issues than Mythos or Fable 5 is patching.