AshutoshShrivastava(@ai_for_success):🚨 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

2026.09.01 18:05

🚨 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