The extension brings Nvidia's venture arm and Sapphire Ventures into a Series A led by Lightspeed Venture Partners, alongside WndrCo, Amplify Partners, Sky9 Capital and FPV Ventures. Reactor did not disclose the size of the new tranche or its valuation; total raised now stands at $74M. The company builds the inference engine, GPU cloud and low-latency streaming layer needed to run interactive video and world models in real time, and says it has active projects with Hollywood studios, advertising platforms and streaming services. Nvidia's interest tracks a wider rush into world models this quarter, including General Intuition's $220M raise, Runway's Praxis-1 open-weight world action model and Mirror Particle's behavioural model, which is heading to Disrupt's Startup Battlefield this month. For builders, Reactor is a bet that the hard part of world models is not training them but serving them interactively, and that a specialised runtime will sit between model labs and the game, film and ad companies that want to use them.