Arena Raises $200 Million Series B at $3.1 Billion Valuation and Launches Alignment Index

Arena announced a $200 million Series B at a $3.1 billion valuation and launched the Arena Alignment Index, a benchmark meant to measure whether AI agents act in line with human intent once they are used in real workflows. The financing gives the AI evaluation company more capital to expand beyond capability rankings into safety and alignment measurement as agents write code, analyze documents and take actions users may not be able to verify; Arena also argues that static benchmarks break down once models recognize they are being tested.