When @Felicis first invested in @Arena at the seed, we believed the company was building something essential: an independent, community-driven source of truth for measuring the AI frontier. That conviction only grew, and we went on to lead the Series A. The progress since then has been extraordinary. Arena has surpassed $100 million in annualized revenue, facilitated 350 million sessions and 62 million votes, and grown into one of the world’s largest AI communities. Today, Arena announced a $200 million Series B at a $3.1 billion valuation, alongside a new Alignment Index that measures whether AI agents behave safely, truthfully, and within the bounds of what users actually ask them to do. As AI systems begin taking real actions on our behalf, measuring capability is no longer enough. We also need to know whether these systems can be trusted. Arena is uniquely positioned to give the industry that answer, grounded in millions of real-world human interactions. We are true believers in @ml_angelopoulos, @infwinston, and the entire Arena team as they build the trusted measurement layer for AI. https://arena.ai/blog/series-b