Principal Machine Learning Engineer, Applied AI

Location: Cambridge, MA, USA or San Francisco, CA, USA

Expected base salary: $252,000–$336,000 USD annually, with bonus potential and early-stage equity.

Company

hirify.global is building AI systems and proprietary instruments to create a scientific operating system that autonomously executes the scientific method across medicine, materials, and energy.

What you will do

• Adapt AI models to customer-specific scientific workflows and close the gap between model capabilities and production use cases.
• Lead model post-training using SFT and reinforcement learning methods including DPO, PPO, and GRPO.
• Build evaluation loops to measure model quality, reliability, and customer fit.
• Turn customer feedback, data signals, and evaluation results into iterative model improvements.
• Partner with AI Research and Software teams to integrate model behavior into end-to-end product workflows.
• Debug complex model failures and mentor engineers on model adaptation, evaluation, and deployment.

Requirements

• 2–3+ years of hands-on post-training experience, including SFT, DPO, PPO, or GRPO, and evaluation system design.
• Strong software engineering skills in Python and modern machine learning frameworks such as PyTorch.
• Experience debugging ambiguous, high-stakes model behavior using data, traces, logs, and qualitative feedback.
• Experience leading technical work across research and engineering teams.
• Deep familiarity with large language models, multimodal models, or agentic AI systems.
• Clear communication skills for translating customer needs into technical approaches and explaining complex model behavior.

Nice to have

• Experience adapting models for customer-facing production workflows in scientific, technical, or data-intensive domains.
• Experience with RLHF, GRPO, tool-augmented reinforcement learning, evaluation harnesses, monitoring, or quality dashboards.
• Experience training mixture-of-experts architectures.
• Mentoring experience and recognition as a go-to technical expert.

Culture & Benefits

• Startup-speed environment focused on scientific AI and high-impact problems.
• Full-time U.S. employees receive medical, dental, vision, life, and disability coverage.
• Flexible time off, company-wide holidays, and paid parental leave.
• Educational assistance, commuter benefits, and subsidized lunch for office-based employees.
• Full-time employees outside the U.S. receive benefits tailored to their region.