Principal Machine Learning Engineer, ML Bots - Game Tech Group

At AI Foundations, our mission is to unlock cutting edge player experiences through the power of ML and AI technologies. Within this space, the AI Foundry team partners with teams across Riot to accelerate the development and deployment of new machine learning & AI systems. We dive into diverse, high impact projects across Riot, and help take them from ideas to fully fledged features. As a Principal Machine Learning Engineer specializing in applied machine learning, you will lead the modeling strategy for our most ambitious applications of Game Understanding Agents in a deeply technical role. You'll elevate the technical standards in reinforcement learning, imitation learning, and simulation-based training for game AI by mentoring engineers on the ML Bots team. Your contributions to Riot’s shared game AI frameworks will accelerate development across multiple games and you'll build strong cross-disciplinary partnerships to achieve these goals. You and your team will develop and deploy in-game Game AI capabilities that significantly enhance the player and developer experience, creating reusable training and evaluation pipelines for Game Understanding Agents that support multiple game genres and adapt to each title’s unique constraints. You will support the team in combining modern ML with deep game domain knowledge to create autonomous agents that can play, understand, and adapt like real players. Responsibilities: Lead the modeling strategy for ML Bots across multiple games, focusing on training agents that can understand game state, make decisions, and act in ways that create compelling player experiences. Develop predictive features and signals from gameplay telemetry, unstructured game data, and simulation outputs, ensuring quality, interpretability, and reliability. Design and implement ML systems using methods including reinforcement learning and imitation learning (e.g., behavior cloning, inverse reinforcement learning), on-/off-policy algorithms, policy gradient methods, behavior shaping, and hybrid systems that combine learned policies with rule-based or scripted components. Define evaluation frameworks for game AI that balance generalizable approaches with genre-specific metrics, adapting methods for the needs of each title. Ensure the safety, fairness, and trustworthiness of autonomous agents operating in live player environments. Mentor senior and staff-level ML engineers in advanced ML for game AI and architectural decision-making. Collaborate with game and platform engineers, along with UX teams, to integrate models into production systems in ways that enhance player experience and maintain operational reliability. Represent the ML Bots team in multi-game forums and contribute to shared frameworks for autonomous agent development. Required Qualifications: Extensive experience (8+ years) delivering ML systems in production, including reinforcement learning, imitation learning, or simulation-based training in rich, interactive environments such as game worlds or multi-agent simulations. Proven ability to design modeling strategies and architectures adopted across multiple games or interactive products. Expertise in developing predictive features and signals from gameplay telemetry, simulation data, or other complex interactive environments. Strong track record building and optimizing agent-based systems or world models for dynamic, player-facing environments. Hands-on experience with relevant ML methods including reinforcement learning and imitation learning (such as behavior cloning and inverse reinforcement learning), on-/off-policy algorithms, policy gradient methods, behavior shaping, and hybrid systems that combine learned policies with rule-based or scripted components. Mastery of experiment design, model evaluation, and optimization for autonomous agents. Track record of incorporating human considerations into AI applications, such as responsible AI practices and human-computer interaction or UX best practices. Experience mentoring engineers and collaborating with cross-disciplinary teams. Familiarity with integrating ML-driven agents into live game environments with game and platform engineers. For this role, you'll find success through craft expertise, a collaborative spirit, and decision-making that prioritizes the delight of players. We will be looking at your past studies, experience, and your personal relationship with games. If you embody player empathy and care about players' experiences, this could be your role! Our Perks: Riot focuses on work/life balance, shown by our open paid time off policy and other perks such as flexible work schedules. We offer medical, dental, and life insurance, parental leave for you, your spouse/domestic partner, and children, and a 401k with company match. Check out our benefits pages for more information. At Riot Games, we put players first. That mission drives every decision in our quest to create games and experiences that make it better to be a player. Whether you’re working directly on a new player-facing experience or you’re supporting the company as a whole, everyone at Riot is part of our mission. And just like in our games, we’re better when we work together. Our goal is to create collaborative teams where you are empowered to bring your unique perspective everyday. If that sounds like the kind of place you want to work, we’re looking forward to your application. It’s our policy to provide equal employment opportunity for all applicants and members of Riot Games, Inc. Riot Games makes reasonable accommodations for handicapped and disabled Rioters and does not unlawfully discriminate on the basis of race, color, religion, sex, sexual orientation, gender identity or expression, national origin, age, handicap, veteran status, marital status, criminal history, or any other category protected by applicable federal and state law. We consider for employment all qualified applicants, including those with criminal histories, in a manner consistent with applicable federal, state and local law, including the California Fair Chance Act, the City of Los Angeles Fair Chance Initiative for Hiring Ordinance, the Los Angeles County Fair Chance Ordinance for Employers, the San Francisco Fair Chance Ordinance, and the Washington Fair Chance Act. Per the Los Angeles County Fair Chance Ordinance, the following core duties may create a basis for disqualifying candidates with relevant criminal histories: Safeguarding confidential and sensitive Company data Communication with others, including Rioters and third parties such as vendors, and/or players, including minors Accessing Company assets, secure digital systems, and networks Ensuring a safe interactive environment for players and other Rioters These duties are directly related to essential operations, safety, trust, and compliance obligations within our organization. Please note that job duties may evolve based on business needs and additional responsibilities may be assigned as necessary to maintain operational efficiency and security.