Brett Winton of ARK Invest asserts that OpenAI's GPT 5.6 model offers superior performance breadth and approximately two times better cost and time efficiency compared to Fable, which he describes as an "overclocked" GPT-5.5 class model.
OpenAITailwindOpenAI released GPT-5.6 Luna, which significantly improves performance in health intelligence and achieves a 25x cost reduction, representing a qualified operational milestone and product enhancement.