Principal Research Engineer, Model Training & Post-Training

<div class="content-intro"><h2><strong>About Inflection AI</strong></h2> <p>Inflection AI is a Public Benefit Corporation empowering people with human-centered, emotionally intelligent AI. We’re shaping the future of AI by combining emotional intelligence (EQ) and raw intelligence (IQ) to elevate people’s potential.<br><br>Inflection AI created Pi, the world’s first emotionally intelligent AI, to help people work through decisions, emotions, and challenges. Pi is a personal AI agent powered by Inflection AI’s foundation model, proving that AI can be personal, empathetic, and contextually aware.</p></div><h2><strong>About the Role</strong></h2> <p>Inflection’s models are central to our product and platform strategy, and we are looking for a hands-on technical leader to own the model-improvement loop from data and training through evals, post-training, release criteria, and production feedback. This person will sit at the intersection of research, production engineering, and model release, with a mandate to ship models that are measurably better for users. The ideal candidate has led serious model training or post-training work before, can make principled tradeoffs across data, compute, architecture, and quality, around a clear technical roadmap.<br><br></p> <p><strong>What You’ll Do</strong></p> <ul> <li>Own the model-improvement roadmap across capability, reliability, emotional intelligence, tool use, safety, latency, cost, and enterprise readiness.</li> <li>Lead training and post-training strategy, including supervised fine-tuning, RLHF, DPO, GRPO, RLAIF, reward modeling, preference optimization, tool-use fine-tuning, distillation, synthetic data, and related methods.</li> <li>Drive model architecture and optimization decisions across modern transformer-based and hybrid architectures, including both training-time and inference-time performance.</li> <li>Lead large-scale training efforts on distributed GPU clusters, including systems operating at the scale of 1,000+