The LLM Data Company is a YC X25 company creating post-training data and RL environments for AI labs and applied AI companies. We have raised $3.6m from Tier 1 VCs and are growing 200%+ month-over-month.

About The LLM Data Company

The LLM Data Company (YC X25) provides post-training data and RL environments to foundation model labs and frontier applied AI companies. We have raised $3.6m from Tier 1 VCs and are growing 200%+ month-over-month.

Responsibilities

• Design and implement scalable RL recipes for post-training task-specific models

• Develop modular environments, reward functions, and evaluator scaffolds for internal and customer-facing tasks

• Drive research at the intersection of scalable infra and modern RL frameworks to enable RL-as-a-service

• Drive foundational research to publish open source environments and training data

• Build data generation and curation pipelines to support frontier post-training

• Collaborate with product teams to deliver a user friendly interface for non-technical users to generate data

Qualifications

• Master or PhD in Computer Science or related field

• Comfort with core tooling (verl, PyTorch, etc.)

• Familiarity with modern post-training techniques (GRPO, etc.)

• Experience with evaluations and reward engineering

• Published in top journals (ICLR, NeurIPS, ICML, etc.)

Why you should join

• Cutting-edge research : Work on unpublished, novel training environments

• Direct lab exposure : Projects that labs actually use and validate in production

• High autonomy : Wide design space to propose and run experiments with minimal oversight

• Early team member : Join as one of the first 10 people with significant equity upside