I was a bit skeptical when they said it behaves like Fable but is cheaper... those two things have been mutually exclusive in my experience, no LLM can light tokens on fire faster while spinning its wheels than the Fable/Mythos tier of models.
Sent Opus 5.5 an example that used go context.WithTimeout and it tried to tell me that was wrong and I should pass timeouts as ints before finally admitting the docs it cited didn't say to use ints and that's a ridiculous design in go anyway (it was trying to claim that was codebase convention--passing ints...)