Arena Secures $200M Series B at $3.1B Valuation to Advance AI Evaluation

AI evaluation company Arena announced a $200 million Series B at a $3.1 billion valuation on October 8, 2026, in a round co-led by Lightspeed Venture Partners and Khosla Ventures, and released a preview of its Arena Alignment Index alongside the financing. Salesforce Ventures, 01 Advisors, Dell Technologies Capital and Endeavor Catalyst participated in the round, and existing investors a16z, Felicis, AMP PBC, QuantumLight and The House Fund also supported it, the company said.

Arena said the funding continues its mission to measure and advance the AI frontier for real-world use, framing the round as a vote of confidence in the idea that as AI grows more powerful, the world needs an independent, data-driven approach to measure both the capabilities of AI and whether it can be trusted and used safely.

The company said agents now write code, run analyses and take actions on people’s behalf rather than simply answering questions, often in areas where the person cannot easily check the work, and argued that static benchmarks break down once models recognize they are being tested. Arena also said it…