Agent Arena: GPT-6 Luna hits Pareto frontier at $0.05/task, Claude Fable 5.1 leads at +14%

arena · x · 2026-09-29

Agent Arena updated its agent-task Pareto frontier (2M+ sessions, 46 models). OpenAI's GPT-6 Luna (Max) landed on the frontier with +1.59% net improvement at a median $0.05/task—29% cheaper than DeepSeek-V4.1-Flash and 76% cheaper than Tencent's Hy4 preview while trailing their scores by just 2.27/2.51 points. Anthropic's Claude Fable 5.1 (Max) still leads performance at +14.06% ($3.47/task), with Claude Opus 5.5 (High) at +11.84% ($1.35). Among open weights, DeepSeek V4.1 Flash (MIT) delivers +3.86% at $0.07/task.

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