Claude Opus 5.5 is now in Arena.ai Agent Arena and Battle Mode

Claude Opus 5.5 by AnthropicAI is now in Arena.ai’s Agent Arena. It is also in Battle Mode for WebDev, Text, Vision, and Document.

Arena.ai says Agent Arena measures models on millions of real-world, long-horizon agentic tasks from a global community of users. Models can use web search, filesystem, and terminal tools. The leaderboard scores outcomes relative to the average model using a causal tracing methodology.

Claude says Opus 5.5 is the first model in the Claude 5.5 family, performs at the level of Claude Fable 5.1 for most tasks, and costs 40% less to run than Opus 5.