Model Engineer, Post-Training & RL

Xai · Palo Alto, CA · Engineering

Posted 2026-11-01

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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++

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.

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