Backed by Lightspeed and a16z.
About the role
Technical Leadership & Mentorship: Define and drive the technical roadmap for mid- and post-training systems, balancing research innovation with production reliability and scalability. You will mentor and grow a team of researchers and engineers through technical guidance, design reviews, and career development. Establish best practices for experimentation, model development, and deployment.
What they're looking for
- PhD in Computer Science, Machine Learning, AI, or a related field, or equivalent industry experience
- Significant experience leading technical projects or teams in machine learning, AI research, or large-scale distributed systems. Experience scaling and mentoring high-performing research and engineering teams
- Deep understanding of modern machine learning techniques, including transformers, reinforcement learning, alignment methods, and large language models
- Strong track record of delivering impactful research or applied ML systems in production environments
- Expertise in designing, building, and maintaining production-quality ML systems and infrastructure
- Experience training, serving, debugging, and optimizing large-scale models on GPU-based systems
More about this role
About the Role and Team As a Principal Research Engineer on the Post-Training team, you will drive the technical vision, execution, and evolution of the systems that transform foundation models into intelligent, engaging, and aligned products. Specifically, your team focuses on post-training of top-tier OSS LLMs (such as Mistral and Qwen) to power the highly immersive role-playing chat features of Character.AI .
You will lead initiatives spanning data, algorithms, infrastructure, and evaluation, helping define how our models learn from feedback and improve over time. This is a highly cross-functional role that combines deep technical expertise with organizational leadership. You will partner closely with researchers, engineers, product teams, and infrastructure teams to identify the highest-leverage opportunities for improving model performance and user experience. Your work will directly shape the conversational experiences of millions of users every day. At Character.AI , you will have the opportunity to influence both the direction of our research and the systems that bring it into production, helping build the next generation of AI entertainment.
Technical Leadership &...
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