Sr. Model Engineer, Mid-Training

xAI

xAI’s mission is to create AI systems that can accurately understand the universe and aid humanity in its pursuit of knowledge.

xAI is the employer — EngRadar is a job radar, not a recruiter. We track this posting from their own careers page and send you straight there; we never handle applications or CVs.

Palo Alto, CA Posted 10d ago ai

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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.

RESPONSIBILITIES:

Scale synthetic coding data to trillions of tokens with large-scale docker verification
Distill the intelligence of flagship models into flash models through synthetic data generation
Optimize mid-training data mixtures to boost the ceiling for RL
Engineer long-context data recipes
Develop robust and diverse evaluation for mid-training checkpoints

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:

Familiarity across all kinds of scaling laws
Strong ability to design ML experiments
Familiarity with state-of-the-art techniques for curating AI training data for text, image, audio, and video modalities
Strong engineering abilities in large-scale data processing frameworks
Experience with ML and large model scaling
Experience with Spark, Ray, and other large-scale data processing frameworks

COMPENSATION AND BENEFITS:

$180,000 - $440,000 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.

Posted by xAI on their own careers page — you apply directly, no recruiter in between. View original / apply →