Also spent the past day using Fable for everything I usually use Opus or gpt-5.5 for. My experience is that it’s a better and more reliable Opus that’s far better in frontend tasks than backend/ios. More similar to gpt-5.5 for long running tasks and reliability.

It still left small bugs and weird behaviors that it cleaned up when I told it about them, but it felt very Opus-ey.

I think for implementing a detailed design doc, I’d put it on par with gpt-5.5 high but farrrr more expensive. I’m eating through my x5 Max plan in no time. I’d use it for reviewing implementations and designs docs as another pass, but it’s too expensive for me for reading a lot of (uncached) code by itself in an agentic loop, especially with medium to high reasoning.

As a daily driver too expensive, that crown still goes to gpt-5.5.

I barely used it in high/xhigh/max reasoning though.