Agent Arena

Arena.ai's Agent Arena analysis finds that Gemini 4 Carbon becomes increasingly cost-competitive as task complexity rises. On typical tasks, GPT-6 Astra costs about 3.4x and Claude Opus 5.5 about 3.9x as much as Carbon, while across the most expensive 5% of sessions Opus rises to 4.2x and Astra's cost roughly doubles relative to Carbon. The finding is relevant for budgeting long-horizon agent workloads.

Anthropic has launched Claude Fable 5.2 and Claude Mythos 5.2, claiming gains in coding, reasoning and vision for tackling demanding technical work. Fable 5.2 is now live in Arena's Agent Arena and Code Arena, where it can use web search, filesystem and terminal tools on long-horizon agentic tasks, with leaderboard scores to follow.