Machine Learning

Days-long autonomous runs, sub-agent delegation, persistent memory: what Fable 5 changes for agent builders, and where rivals stand today.

Fable 5 posts 80.3% on SWE-Bench Pro against 69.2 for Opus 4.8 and 58.6 for GPT-5.5. We ran the price-per-point math so you do not have to.

Anthropic just shipped its first Mythos-class model to the public. Here is what Fable 5 can do, what it costs, and why it is a new tier.