Senior Research Engineer, Post-training & Evaluation

Reddit is a community of communities. It’s built on shared interests, passion, and trust, and is home to the most open and authentic conversations on the internet. The AI Engineering team at Reddit is embarking on a strategic initiative to build our own Reddit-native foundational Large Language Models (LLMs). As a Senior Research Engineer for Post-Training & Evaluation, you will own the critical "feedback loop" of our model development.

Requirements

• 4+ years of professional experience in machine learning engineering, with a focus on LLM fine-tuning or evaluation.
• Fluency in Python and PyTorch, with experience using libraries like Hugging Face Transformers, vLLM, or lm-eval-harness.
• Deep understanding of Instruction Tuning (SFT) and how data quality impacts model behavior.
• Experience building Evaluation Pipelines: You know the difference between MMLU, GSM8K, and how to build a custom domain-specific benchmark.
• Familiarity with distributed training (FSDP/DeepSpeed) for fine-tuning jobs.
• Strong data engineering skills for curating and cleaning instruction datasets.

Benefits

• Comprehensive Healthcare Benefits and Income Replacement Programs
• 401k with Employer Match
• Global Benefit programs that fit your lifestyle, from workspace to professional development to caregiving support
• Family Planning Support
• Gender-Affirming Care
• Mental Health & Coaching Benefits
• Flexible Vacation & Paid Volunteer Time Off
• Generous Paid Parental Leave