Cursor Open-Sources Mixture-of-Kittens (MoK), a Deterministic MoE Training Megakernel for GB300 NVL72 Racks

Cursor has open-sourced Mixture-of-Kittens (MoK), a deterministic Mixture-of-Experts training megakernel purpose-built for NVIDIA's GB300 NVL72 rack systems. MoK addresses reproducibility and efficiency challenges in large-scale MoE training by providing deterministic execution — a critical property for debugging and auditing training runs at frontier scale. This release is directly relevant to teams training or fine-tuning large MoE models on cutting-edge NVIDIA hardware, as it offers a production-grade kernel that Cursor has validated internally. Open-sourcing this level of infrastructure tooling is relatively rare and signals Cursor's investment in the broader AI training ecosystem beyond its IDE product. Developers with access to GB300 NVL72 clusters can immediately benchmark MoK against existing training kernels.