It seems to me that having a powerful Fable layer for the planning, coordination, orchestration-type work and delegating to a suitable model for the actual execution of "coding tasks" is perfectly appropriate, if that is the case.
You drop a good old "A new {cool_word}-class model.".
And boom! What are you competitors going to do? Use same classification nomenclature? I don't think so! IPO secured.
It is one thing if I, as the user, choose to down-level but Claude shouldn't do this on its own.
"You won't be charged Fable prices for rerouted requests. Learn more about how the fallback experience works."
https://www.anthropic.com/claude/fable Under "Safeguards"
Not like you can tell the difference if you dont own any of the implementation.
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".