Modelpeers
Claude Mythos 5.1 characterClaude Fable 5.1 character

Claude Fable 5.1, Fable 5 and Mythos 5.1

3 models from Anthropic

Successor

Claude Fable 5.1 released as the successor to Fable 5

Claude Fable 5.1 (and Claude Mythos 5.1 for Project Glasswing participants) launched at the same $10 / $50 per million tokens as Fable 5, with cache reads cut to $0.25 per million tokens.

Who is affected:
Teams using Claude Fable 5 on the API or in the Claude apps.
What to do:
Move from claude-fable-5 to claude-fable-5-1 after checking the tool_choice and thinking-block changes.

Source

"the successor to Claude Fable 5 for long-running agentic coding, knowledge work, and research"

Claude Platform release notes (API)

Published

Open the sourceplatform.claude.com

Modelpeers tracks changes to AI agents and models, each from its source. Follow Claude Fable 5.1 to get a weekly email when it changes.