Machine Learning Engineer – Lumen Enterprise Models (SWE-focused LLMs)

Cosine is hiring a Machine Learning Engineer to train and improve its Lumen Enterprise software-engineering models. The role spans model training, reinforcement learning, performance optimization, and collaboration with infrastructure, platform, and data teams.

Responsibilities:

• Work across the full training lifecycle, running pre-training, supervised fine-tuning and reinforcement-learning experiments
• Optimize training methods at scale on frontier models
• Diagnose and fix performance bottlenecks and communication overhead in distributed training environments
• Train models on long-context, multi-file and repository-level tasks
• Develop RL and RLVR loops using signals from execution, tests, linters, static analysis and other engineering feedback, turning fresh ideas into scalable, reproducible code
• Investigate model failure modes such as poor planning, brittle fixes, reward hacking and regressions
• Collaborate with infrastructure, platform and data teams