Sr. Model Engineer, RL Training Framework

SpaceXSI; Palo Alto (CA); On-site; USD 180,000 - 400,000; Full time

Benefits offered by this job

Equity

Medical

Vision

Dental

401(k)

Disability Insurance

Life Insurance

Discounts & Perks

Job summary

SpaceXSI in Palo Alto is seeking a Senior Model Engineer to build and maintain the RL training framework that powers our Grok models. You will work on scalable RL infrastructure, from small experiments to production training runs, partnering with teams across our stack to push frontline AI capabilities.

The role demands strong software engineering skills, experience with Python and modern ML frameworks, and a passion for optimizing performance, efficiency, and reliability in large-scale

Qualifications

• Production-quality code experience in Python, PyTorch, JAX, Rust or C++.
• Experience training large models (1B+ parameters) including RL training.

Responsibilities

• Design and implement the RL training framework and supporting systems.
• Profile, debug, and optimize end-to-end RL training performance.
• Improve scalability and observability of the RL stack.

Skills

Python

PyTorch

JAX

Rust

C++

Large-scale model training

Job description

SpaceX was founded under the belief that a future where humanity is out exploring the stars is fundamentally more exciting than one where we are not. Today, SpaceX is actively developing the technologies to make this possible, with the ultimate goal of making life multiplanetary and expanding consciousness to the stars.

SpaceXSI is building Super Intelligence to help humanity understand the universe. Our teams are building the full Super Intelligence stack: from our Colossus supercomputers, to Grok models, to our suite of applications, including Grok Bot, Grok Build, Grok Imagine, Grok Voice, and X. We're creating a powerful flywheel where more compute trains better models, better models power more useful products, and what we learn from people using those products shapes what we build next.

SR. MODEL ENGINEER, RL TRAINING FRAMEWORK

The RL infrastructure team is looking for an engineer to help develop our RL training framework.

RESPONSIBILITIES:

• Design and implement the systems backing all RL workloads at SpaceXSI, from small scale ablations to production training runs
• Profile, debug, and optimize end-to-end training performance
• Improve scalability and observability of the RL stack

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:

• Experience building, debugging, and optimizing efficiency of large-scale distributed systems
• Experience with large scale LLM training infrastructure
• Experience with RL numerics
• Strong knowledge of reinforcement learning techniques
• Comfortable diving into unfamiliar areas and solving problems at all levels of the stack

COMPENSATION AND BENEFITS:

$180,000 - $400,000 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.

• equity
• comprehensive medical
• vision
• dental coverage
• access to a 401(k) retirement plan
• short & long-term disability insurance
• life insurance
• various other discounts and perks