LLM Data Researcher

About the Role Join an early-stage research team at a European AI data company and investigate whether expert-generated data improves language model performance. You will conduct hands-on research, build evaluation infrastructure, and help determine which research and data initiatives to pursue. What You'll Do Post-train language models on expert datasets and measure their impact, investigating when results fall short. Design and run evaluations of frontier language models in expert domains. Select and execute suitable training methods, including supervised fine-tuning, reinforcement learning, and preference tuning. Translate research findings into dataset specifications and recommendations for future work. Publish research papers, benchmarks, and written research updates. Coordinate research findings with data, client, partnership, and marketing teams. What We're Looking For Hands-on research experience with reinforcement learning environments for language models or RL-based post-training, such as RLHF, RLVR, reward modeling, or preference optimization. A completed or nearly completed PhD in machine learning or NLP, or an equivalent research record demonstrated through publications or AI lab and industry research work. Experience personally post-training and evaluating language models end to end, and building evaluations or benchmarks. Research publications at leading machine learning or NLP venues, or experience building evaluation tools. Early-career research profile, from near PhD completion to a few years post-PhD. Compensation & Benefits Competitive salary and equity. Relocation support is available. Visa sponsorship details were not provided. Location Full-time, on-site in Barcelona, Catalonia, Spain. Relocation support is available.