Fable 5.1 by Anthropic Enters Arena

Arena.ai posted that Fable 5.1 by AnthropicAI is now in the Arena. The company invited users to submit their toughest prompts and begin voting, with scores scheduled to appear soon. It described Agent Arena as a system that evaluates models on millions of real-world, long-horizon agentic tasks. Models in the arena can use web search, filesystem, and terminal tools to handle complex workflows. The announcement came from the official Arena.ai account and included a static promotional graphic.