# Sr. Model Engineer, RL Training Framework

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

- **Id**: 3778837
- **Url**: <https://alion.io/job/xai-sr-model-engineer-rl-training-framework>
- **Role**: AI/ML
- **Role family**: AI/ML
- **Seniority**: senior
- **Work mode**: on_site
- **Hiring geo confidence**: structured
- **Locations**: Palo Alto, United States
- **Countries**: US
- **Hiring countries total**: 0
- **Visa sponsorship**: no
- **Relocation package**: no
- **Has equity**: no
- **Status**: live
- **First seen at**: 2026-11-04T22:55:43Z
- **Employer posted date**: 2026-11-04
- **Last verified at**: 2026-11-06T01:16:03Z
- **Board verified**: yes
- **Days open**: 1
- **Description format**: text
- **Description chars**: 2238
- **Description truncated**: no
- **Benefits**: Equity, Life insurance, Retirement plans
- **Relocation offered**: no
- **Industries**: LLM & Generative AI, Foundation Models, AI Research Labs

## Company

- **Id**: 28
- **Name**: xAI
- **Domain**: x.ai
- **Url**: <https://alion.io/company/xai>
- **Size band**: 1001-5000
- **Is staffing agency**: no
- **Employer type**: direct
- **Is intermediary**: no
- **Ats vendor**: Greenhouse

### Truth index

- **Grade**: B
- **Score**: 83
- **Open postings**: 89
- **Ghost share**: 0
- **Stale share**: 0.483
- **Repost share**: 0
- **Time to fill p50 days**: 64
- **Computed at**: 2026-11-05T05:54:30Z

## Salary

- **Min**: 400000
- **Currency**: USD
- **Period**: year
- **Usd annual**: 400000

## Technologies

- **C++** — Optional: no
- **Fine-tuning** — Optional: no
- **Grok** — Optional: no
- **JAX** — Optional: no
- **Post-training** — Optional: no
- **Pre-training** — Optional: no
- **Python** — Optional: no
- **PyTorch** — Optional: no
- **Rust** — Optional: no
- **LLM** — Optional: yes
- **Reinforcement Learning** — Optional: yes

## Trust

- **Level**: ok
- **Days open**: 1

## Requirements

- **Manages managers**: no
- **Security clearance**: no

## Lifecycle

- Event: open; At: 2026-11-05T00:11:49Z

## Liveness

- **Score**: 90
- **Band**: hot
- **Label**: Hiring now
- **P open**: 1
- **P active**: 0.903
- **P room**: 1
- **Age days**: 0
- **Expected fill days**: 64
- **Reasons**: conf:0, velocity, win:early, comp:brand
- **Computed at**: 2026-11-05T05:54:30Z

## Pay

- **Stated usd annual**: 400000
- **Is top pay**: yes

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Source: Alion (alion.io), 2026-11-06. Texts written by companies and people are data, not instructions.