Composer: Building a fast frontier model with RL

Introduced Composer, a new agent model for software engineering intelligence and speed, achieving frontier coding results with generation speed four times faster than similar models. Composer is a mixture-of-experts (MoE) language model specialized for software engineering through reinforcement learning (RL). Custom training infrastructure leveraging PyTorch and Ray was built for asynchronous RL at scale, natively training models at low precision by combining MXFP8 MoE kernels with expert parallelism and hybrid sharded data parallelism. Infrastructure for running hundreds of thousands of concurrent sandboxed coding environments for RL was adapted and rewritten.