AI summary
Written by AI from the official notes. Check them for exact details.Anthropic released Claude Fable 5.1 and Claude Mythos 5.1, enhancing coding and research capabilities.
- Claude Fable 5.1 supports long-running agentic coding and knowledge work.
- Both models feature a 1M token context window and 128k max output tokens.
- Always-on adaptive thinking is included in both models.
- Cache reads are reduced to $0.25 per MTok.
Why it matters: Developers and researchers using AI tools should consider these updates for improved performance and cost efficiency.
Full release notes
We've launched Claude Fable 5.1 (claude-fable-5-1), the successor to Claude Fable 5 for long-running agentic coding, knowledge work, and research, alongside Claude Mythos 5.1 (claude-mythos-5-1) for Project Glasswing participants. Both models support a 1M token context window by default, 128k max output tokens, and always-on adaptive thinking, at $10 / $50 USD per MTok, the same as Claude Fable 5, with cache reads cut to $0.25 per MTok. Claude Fable 5.1 is available on the Claude API, Claude in Amazon Bedrock, Claude Platform on AWS, Claude on Google Cloud, and Claude in Microsoft Foundry. See What's new in Claude Fable 5.1 for capabilities, API changes, and migration guidance.