Sr. Model Engineer, RL Training Framework

xAI|04 Nov 2026

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Listed location: Palo Alto, CA

Work arrangement: onsite. A remote label does not confirm worldwide eligibility or visa sponsorship.

Read the employer’s description for qualifications, compensation and work eligibility. Confirm the position is still open on the application page.

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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.

SpaceXSI is an equal opportunity employer. For details on data processing, view our Recruitment Privacy Notice.

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Is the Sr. Model Engineer, RL Training Framework position at xAI remote?

The Sr. Model Engineer, RL Training Framework role at xAI does not have a confirmed remote arrangement in our data. Check the employer description for its work location.