Felicis(@felicis):What began as a UC Berkeley research project is becoming the infrastructure the world relies on to understand and advance AI. Today, @arena announced a $200 million Series B at a $3.1 billion valuation and launched the Arena AI Alignment Index, a new way to measure how AI agents behave in the real world. We at @felicis first backed Arena at the seed and led its Series A because @ml_angelopoulos, @infwinston, and @istoica05 understood the ground truth in AI: you can’t improve what you can’t measure. Congratulations to the entire Arena team on this milestone and the important work ahead! Read Arena’s announcement: https://t.co/XkG7qPmQjM And learn how Anastasios and Wei-Lin turned a weekend research project into AI’s trusted evaluation platform:

2026.10.08 17:38

What began as a UC Berkeley research project is becoming the infrastructure the world relies on to understand and advance AI. Today, @arena announced a $200 million Series B at a $3.1 billion valuation and launched the Arena AI Alignment Index, a new way to measure how AI agents behave in the real world. We at @felicis first backed Arena at the seed and led its Series A because @ml_angelopoulos, @infwinston, and @istoica05 understood the ground truth in AI: you can’t improve what you can’t measure. Congratulations to the entire Arena team on this milestone and the important work ahead! Read Arena’s announcement: And learn how Anastasios and Wei-Lin turned a weekend research project into AI’s trusted evaluation platform: