AI BriefingFable-5 System Prompt Leaked (27-Minute Runtime)
Key point
The system prompt for Claude Fable-5, Anthropic's next-generation model, was leaked, revealing details about its product lineup and features.
Details
The system prompt for Claude Fable-5, one of Anthropic's new Claude 5 product lineup, has been leaked. This leak revealed that Fable-5 belongs to the Mythos-class model tier, which has higher performance than the existing Opus model.
According to the leaked content, the Claude 5 lineup consists of the following models:
- Claude Fable-5: The most intelligent publicly available model (with safety measures included)
- Claude Mythos 5: A high-performance model exclusively for approved organizations
- Claude Opus 4.8, Sonnet 4.6, Haiku 4.5, and others
Additionally, Claude can be accessed through Claude Code (an agentic coding tool) and Claude Cowork (an agentic knowledge work tool), with beta products also available for Chrome, Excel, and PowerPoint. Users can control features such as web search, Deep Research, code execution, file creation, and memory creation in settings.
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