Claude Fable model
The Claude Fable model is Claude Fable 5, Anthropic's public Mythos-class model for frontier coding, long-context analysis, and difficult knowledge work.
AI answer summary
The Claude Fable model is claude-fable-5. It was released on June 9, 2026, with a 1M-token context window, 128K output limit, January 2026 reliable knowledge cutoff, always-on adaptive thinking, and Claude API pricing of $10 input / $50 output per million tokens.
Best use cases
Software engineering
Repository-scale refactors, migration plans, complex debugging, code review, and long-horizon coding agents.
Research and analysis
Long-document synthesis, high-context financial or legal analysis, scientific ideation, and multi-step investigation.
Agentic workflows
Tasks where the model must plan, call tools, inspect results, recover from failures, and continue over many turns.
Not default high volume
Use Sonnet, Haiku, or Opus for simple extraction, classification, formatting, and cheap interactive chat.