In my opinion, the big issue with Fable is that Claude Code cannot use it properly. I know, that sounds weird, but I've had Fable run down the wrong lane (and never stop) or give up and claim that something was impossible so many times (until I pointed at a GitHub repo that solves the "impossible" issue).

But a while ago, I had access to a Fable harness that just never gives up. And that verifies itself. It burned $100 in API tokens in 15 minutes ... but it succeeded for all the prompts where Fable + Claude had failed.

And I believe that's a real issue for Anthropic. Fable+Claude is not too expensive thanks to the subscription, but Claude severely nerfs Fable. To save money, I guess. Fable API + Custom Harness is a different class, it's so much better. But API tokens are so expensive, you're cheaper off hiring a freelancer.