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:

What began as a UC Berkeley research project has become one of the fastest-growing and most trusted AI infrastructure companies in the world. This week, the vision set forth by Arena founders @infwinston and @ml_angelopoulos reached another remarkable milestone: @Arena announced it has surpassed $100M in annualized revenue run rate just eight months after launching its enterprise offering, while growing to a community of more than 10 million users helping shape how frontier AI models are evaluated. In the @Felicis profile on the company, Wei-Lin and Anastasios shared how they approached building a platform rooted in scientific rigor, neutrality, and community trust; principles that have become even more important as AI capabilities accelerate. We've been true believers in Arena since Seed.

Two in five home health patients get turned away, not because care isn't available, but because the admin overhead costs more than the agency gets paid. $40B in referrals are rejected every year. That's the problem @AlexRWendland and Ryan Tolsma are rebuilding from scratch with @joinAdaptive. AI-native operations. 100K+ visits delivered. 4.9% rehospitalization rate vs. 12.9% state average. @Felicis investors @Pxd and @EricFlaningam sat down with Alex and Ryan to discuss the future they're building with Adaptive.

Two in every five patients referred to home health care in America never get the care they need. Not because clinicians aren't available. Not because the patient doesn't qualify. They get turned away because the paperwork costs more than the visit pays. Roughly $40B in referrals get rejected this way every year. So the agency says no, and the patient ends up in a nursing facility or gets sicker at home until the ER takes over. We led @joinadaptive's Series A because they stopped trying to sell better software to broken agencies and became the provider instead. AI runs the intake, scheduling, prior authorization, documentation, and billing that traditional agencies burn $.60 to $.90 of every clinical-labor dollar on. When those costs collapse, the patients who would have been rejected instead get the care that they deserve. So far in Adaptive's first market: Patients served by Adaptive have a 4.9% rehospitalization rate compared to the 12.9% Texas state average and 10.2% national average. More than 95% of patients see improvement in ambulation, meaning they are back on their feet, no longer homebound, compared to an 89.5% national average. Patients are set up with a home care provider extremely quickly, with 99% of patients admitted within 48 hours of referral. They have a 4.5-star CMS quality rating against an industry average of around 3. Hear from co-founders @AlexRWendland and @ryanatolsma on the future they're building with Adaptive. 👇 cc: @pxd @EricFlaningam