Initial impressions of Claude Fable 5
9 hours ago
- #Anthropic Claude
- #Machine Learning
- #AI Model Release
- Claude Fable 5 is a new AI model from Anthropic, released on June 9, 2026, with strict guardrails for safety and comparable performance to Claude Mythos 5.
- The model has a 1 million token context window, 128k max output tokens, knowledge cut-off of January 2026, and costs $10/million input tokens and $50/million output tokens.
- Initial testing shows Fable 5 is slow and expensive but highly capable, excelling at tasks like upgrading a MicroPython WASM project to full Python and adding features to Datasette Agent.
- Fable 5 demonstrated extensive knowledge, such as listing open-source projects by Simon Willison in detail, suggesting it may be a larger model than previous versions.
- The model is available on Claude.ai and other surfaces until June 22nd for subscribers, with usage tracked via tools like AgentsView, totaling $110.42 in token costs in one day.