Claude Fable 5 just launched, and I did what any reasonable person would do: I woke up at 6 AM, got flashbanged by an announcement page with no dark mode, read the whole thing, and then let the model loose on my production SaaS to see if the hype is real.
I recorded the whole experiment, including the exact moment Claude talked back to me for the first time ever. If you'd rather watch than read, here's the video:
This post is the written version of that experiment: what the announcement actually says, the benchmark everyone should be paying attention to, the feature Fable 5 built in my codebase (with the real code it wrote), and my honest verdict at the end. If you only care about the verdict, feel free to scroll. I do the same thing.
Fable vs Mythos: same model, different safeguards
The announcement opens with a sentence that sets the tone: Fable 5 is a Mythos-class model that Anthropic made safe for general use. It's state of the art on nearly all tested benchmarks, and the longer and more complex the task, the larger its lead over previous models.
