Nvidia joins Reactor’s Series A as world model startup reaches $74 million

Nvidia has placed another bet on the idea that AI’s next act happens off the screen. On October 5, 2026, Reactor, a San Francisco startup building infrastructure for real-time generative video and world models, said Nvidia and Sapphire Ventures had joined its Series A. The new backers bring Reactor’s total funding to $74 million. When the company emerged from stealth on May 28, 2026, that figure stood at $59 million. The timing is hard to miss. Days earlier, AMD announced plans to acquire World Labs for $8.2 billion in stock, putting an eye-catching price tag on a category that barely registered with most investors a short while ago. What Reactor is actually building Lightspeed Venture Partners originally led the Series A. Nvidia and Sapphire Ventures are latecomers to the round, though hardly minor ones. Reactor is not trying to build the flashiest world model itself. It sells a developer platform, offering an SDK and API that let other companies run world models in their own products. The company says its platform runs at over 60 frames per second with latency under 40 milliseconds. That performance rests on three pieces Reactor built itself: a proprietary inference engine, a glo...