The vendor reduced cache read pricing for Fable 5.1 and said the model is similar to Mythos 5.1, with different safeguards.
September 2, 2026
Anthropic introduced Fable 5.1 and Mythos 5.1, highlighting how it is addressing pricing concerns for enterprise customers. However, despite the powerful capabilities of Fable 5.1 and Mythos 5.1, enterprises don’t always need the most powerful model for their workloads.
The AI lab on Sept. 1 revealed that Fable 5.1 and Mythos 5.1 are the same models, except that Mythos 5.1 is accessible only to authorized users as part of its Project Glasswing cybersecurity initiative and includes distinct levels of safeguards.
The vendor said that, along with increased capabilities in advanced coding and knowledge work, and improved research skills in science fields, Fable 5.1 costs 25% less than Fable 5 for typical workloads because it reduces cache read pricing. Cache read is when the model reads the inputs that have already been processed or stored. This means Fable 5.1 pricing is reduced from $1 per million tokens to $0.25 per million tokens. Other than this difference, the standard input pricing remains $10 per million input tokens and $50 per million output tokens. The standard pricing is still significantly higher than OpenAI’s GPT-5.6 Sol, which is $5 per million input tokens and $30 per million output tokens.
