4/3/2026 Scaling and Optimizing Frontier Model Training

On this page How Fireworks scales frontier model training and offers the broadest set of fine-tunable MoE models on any platform. Training trillion-parameter Mixture-of-Experts (MoE) models has historically been bottlenecked by memory walls and complex cluster orchestration. Earlier this month, Cursor released Composer 2 — a frontier coding model that tops CursorBench at 61.3, SWE-bench Multilingual at 73.7, and Terminal-Bench at 61.7. Fireworks powers the Reinforcement Learning (RL) inference infrastructure behind it, proving that these bottlenecks can be overcome at scale. We have written about delta-compressed weight sync and multi-region rollout fleets, and about why numerical parity between training and inference is especially hard for MoE models. Those posts cover the inference half of the RL loop — rollouts, weight transfer, and numerical alignment. This post covers the last missing piece: the trainer itself. Our Training SDK provides the model…