🚨 Claude Fable 5.1 and Mythos 5.1 are now available in the API.
Just found the details in Anthropic's official docs. This looks like a serious upgrade for long-running agentic work.
- 1M token context + 128K max output
- Stronger agentic coding, research, documents, spreadsheets and slides
- Better computer use and long-horizon tasks
- Adaptive thinking with adjustable effort
- 75% cheaper cache reads than Fable 5
- $10/M input tokens
- $50/M output tokens
- $0.25/M cached input tokens
- Fable 5.1 is available to all API customers
- Mythos 5.1 is currently limited to Project Glasswing participants