Arena raises $200M Series B at $3.1B valuation, nearly doubling in 10 months

AIArena, the crowdsourced AI model leaderboard that started as a UC Berkeley research project, raised a $200 million Series B at a $3.1 billion valuation, led by Lightspeed Venture Partners and Khosla Ventures. The company said it reached $100 million in annualized run-rate revenue in June, up from $30 million when it raised its $150 million Series A in January at a $1.7 billion post-money valuation.

AIArena has announced a Series B round co-led by Lightspeed and Khosla Ventures, with participation from Salesforce Ventures, 01 Advisors, Dell Technologies Capital, and Endeavor Catalyst. Existing investors Andreessen Horowitz, Felicis, a16z's AMP, QuantumLight, and The House Fund also supported the round.

AIArena announced a $200M Series B at a $3.1B valuation alongside its new Arena Alignment Index, a benchmark built from 90K+ real-world agent sessions across 27 models. The index measures Unauthorized Action, False Attribution, and Deceptive Completion, with OpenAI's GPT-6.1-Sol leading at 87.9, ahead of Claude-Opus-5.5 at 83.2 and Grok-4.7 at 82.7. The source reports that newer models outperform their predecessors across all four labs it covers.