Sr. Model Engineer, Post-Training & RL

SR. MODEL ENGINEER, POST-TRAINING & RL

You will work on the most critical post-training and reinforcement learning challenges at any given time — including reward modeling, preference optimization (RLHF/DPO), and RL for improving reasoning, truthfulness, and real-world capabilities.

BASIC QUALIFICATIONS:

• Experience writing production-quality code in Python, PyTorch, JAX, Rust, or C++
• Experience training large models (e.g., pre-training, post-training, fine-tuning, or RL training of neural networks with 1B+ parameters)

PREFERRED SKILLS AND EXPERIENCE:

• You believe truth-seeking AI is the most important and challenging problem
• You are obsessed about building incredibly useful models through post-training and RL techniques
• You are a power user of AI models and eager to push the boundaries of what’s possible with reinforcement learning and alignment methods
• If you previously worked on post-training, RLHF, or trained models used by millions of people it’s a big plus, but relevant experience is not required
• You take pride in your work and thrive in meritocratic environments

COMPENSATION AND BENEFITS:

$180,000 - $600,000 USD

Base salary is just one part of our total rewards package at SpaceXSI, which also includes equity, comprehensive medical, vision, and dental coverage, access to a 401(k) retirement plan, short & long-term disability insurance, life insurance, and various other discounts and perks. SpaceXSI is an equal opportunity employer. For details on data processing, view our Recruitment Privacy Notice .