AI evaluation platform Arena closes $200M Series B at $3.1B valuation on October 8
Arena closed a $200 million Series B at a $3.1 billion valuation, led by Lightspeed and Khosla, to expand real world model evaluation.
Independent AI evaluation platform Arena announced a $200 million Series B on October 8 at a $3.1 billion valuation. Lightspeed Venture Partners and Khosla Ventures led the round, with participation from Salesforce Ventures, 01 Advisors, Dell Technologies Capital, Endeavor Catalyst, a16z and Felicis. Arena began as a 2023 UC Berkeley research project and now operates a crowdsourced service for comparing models and vibe coding projects, with tens of millions of monthly visitors. It launched a commercial evaluation product for laboratories and enterprises in September 2025. Arena raised a $150 million Series A in January at a $1.7 billion post money valuation and about $30 million in annualized revenue. The company said annualized revenue reached $100 million by June. The financing will fund real world model evaluation, while a new Alignment Index covers unauthorized actions, false attribution and deceptive completion.