#Fable 5

Claude Fable 5.5 has not been announced: no model id, no model card, no pricing. A tracker, with dates and sources, of what's confirmed (Fable 5.1 is still the current model, Anthropic's IPO is targeted for mid-November) and what's just timeline chatter (hidden routing, viral demos, a URL returning 404). Plus what to do with your code in the meantime.

GPT-6 Astra is OpenAI's new top-of-the-line model, launched on September 3, 2026 at $10/$50 per million tokens, the same price as Claude Fable 5.1. Benchmark by benchmark against Fable 5.1 and GPT-5.6 Sol, the cache math that makes an agent session 54% more expensive on Astra, and the ARC-AGI-3 run where the same model scored 62.7% or 99.9% just by swapping the harness.

Anthropic released Claude Fable 5.1 on September 1, 2026. It beats Opus 5 on every published benchmark, but almost always by 2 to 3 points, and it costs twice as much per token. The official numbers, the real math on an agentic session with a warm cache (where the cost ratio drops from 2x to 1.3x), the decision tree between Fable 5.1, Opus 5 and Sonnet 5, and the 3 breaking changes that break your code if you just swap the model id.