Research Engineer - Environments, Data and Post-Training

Mercor; San Francisco (CA); On-site; USD 150,000 - 210,000; Full time

Benefits offered by this job

Generous equity grant

$10K housing bonus

$1.5K monthly food stipend

Free Equinox membership

Health insurance

Job summary

A leading AI development company in San Francisco seeks a Research Engineer to work at the intersection of engineering and applied AI research. In this role, you will enhance model performance through post-training and RLVR pipelines, design experiments, and build scalable systems. The ideal candidate has a strong applied research background, coding proficiency, and is excited to thrive in a high-intensity environment. Benefits include equity grants, housing bonuses, and generous stipends.

Qualifications

• Strong applied research background in post-training and/or model evaluation.
• Experience with machine learning models and strong coding skills.
• Understanding of data structures, algorithms, and backend systems.
• Familiarity with APIs, SQL/NoSQL databases, and cloud platforms.

Responsibilities

• Work on post-training and RLVR pipelines to enhance model performance.
• Design reward-shaping experiments for LLM improvements.
• Quantify data usability and performance uplift on benchmarks.
• Build data generation and augmentation pipelines.
• Create scoring frameworks that guide training decisions.
• Operate in an experimental research environment.
• Collaborate closely with AI researchers and applied AI teams.

Skills

Applied research background

Coding proficiency

Data structures and algorithms

Machine learning models experience

APIs familiarity

SQL/NoSQL databases knowledge

Cloud platforms awareness

Model behavior reasoning

Cloud platforms

Python

Education

PhD or MS in CS/ML

Tools

Python

PyTorch

TensorFlow

ML pipelines

Job description

About Mercor

Mercor is defining the future of work. We partner with leading AI labs and enterprises to provide the human intelligence essential to AI development.

Our vast talent network trains frontier AI models in the same way teachers teach students: by sharing knowledge, experience, and context that can’t be captured in code alone. Today, more than 30,000 experts in our network collectively earn over $2 million a day.

Mercor is creating a new category of work where expertise powers AI advancement. Achieving this requires an ambitious, fast‑paced and deeply committed team. You’ll work alongside researchers, operators, and AI companies at the forefront of shaping the systems that are redefining society.

Mercor is a profitable Series C company valued at $10 billion. We work in‑person five days a week in our new San Francisco headquarters.

About the Role

As a Research Engineer at Mercor, you’ll work at the intersection of engineering and applied AI research. You’ll contribute directly to post‑training and RLVR, synthetic data generation, and large‑scale evaluation workflows that meaningfully impact frontier language models.

Your work will be used to train large language models to master tool use, agentic behavior, and real‑world reasoning in real‑world production environments. You’ll shape rewards, run post‑training experiments, and build scalable systems that improve model performance. You’ll help design and evaluate datasets, create scalable data augmentation pipelines, and build rubrics and evaluators that push the boundaries of what LLMs can learn.

What You’ll Do

• Work on post‑training and RLVR pipelines to understand how datasets, rewards, and training strategies impact model performance.
• Design and run reward‑shaping experiments and algorithmic improvements (e.g., GRPO, DAPO) to improve LLM tool‑use, agentic behavior, and real‑world reasoning.
• Quantify data usability, quality, and performance uplift on key benchmarks.
• Build and maintain data generation and augmentation pipelines that scale with training needs.
• Create and refine rubrics, evaluators, and scoring frameworks that guide training and evaluation decisions.
• Build and operate LLM evaluation systems, benchmarks, and metrics at scale.
• Collaborate closely with AI researchers, applied AI teams, and experts producing training data.
• Operate in a fast‑paced, experimental research environment with rapid iteration cycles and high ownership.

What We’re Looking For

• Strong applied research background, with a focus on post‑training and/or model evaluation.
• Strong coding proficiency and hands‑on experience working with machine learning models.
• Strong understanding of data structures, algorithms, backend systems, and core engineering fundamentals.
• Familiarity with APIs, SQL/NoSQL databases, and cloud platforms.
• Ability to reason deeply about model behavior, experimental results, and data quality.
• Excitement to work in person in San Francisco, five days a week (with optional remote Saturdays), and thrive in a high‑intensity, high‑ownership environment.

Nice To Have

• Real‑world post‑training team experience in industry (highest priority).
• Publications at top‑tier conferences (NeurIPS, ICML, ACL).
• Experience training models or evaluating model performance.
• Experience in synthetic data generation, LLM evaluations, or RL‑style workflows.
• Work samples, artifacts, or code repositories demonstrating relevant skills.

Benefits

• Generous equity grant vested over 4 years
• A $10K housing bonus (if you live within 0.5 miles of our office)
• A $1.5K monthly stipend for meals
• Free Equinox membership
• Health insurance