Joining us as a Research Engineer on the Post-Training team, you'll be diving into the exciting world of fine-tuning AI models, optimizing their performance, and ensuring they meet the highest standards of quality and efficiency. Your work will directly contribute to our groundbreaking advancements in AI, helping shape an era where technology is not just a tool, but a companion in our daily lives. At Character.AI, your talent, creativity, and expertise will not just be valued—they will be the catalyst for change in an AI-driven future.
The Post-Training team is responsible for developing our powerful pretrained language models into intelligent, engaging, and aligned products.
As a Post-Training Researcher, you will work across teams and our technical stack to improve our model performance and training methods, including data, compute and algorithms. You will get to shape the conversational experience of millions of users per day.
Develop alignment algorithms and loss functions to improve data sample efficiency.
Write data pipelines to process diverse web data into a format models can ingest.
Identify quality signals to understand our model’s performance in the real world.
Design sampling algorithms to improve serving efficiency of large generative models.
"All Industry Levels": have at least PhD (or equivalent)
Write clear and clean production-facing and training code
Experience working with GPUs (training, serving, debugging)
Experience with data pipelines and data infrastructure
Strong understanding of modern machine learning techniques (reinforcement learning, transformers, etc)
Track-record of exceptional research or creative applied ML projects
Experience with product experimentation and A/B testing
Experience training large models in a distributed setting
Familiarity with ML deployment and orchestration (Kubernetes, Docker, cloud)
Publications in relevant academic journals or conferences in the field of machine learning
Character.AI empowers people to connect, learn and tell stories through interactive entertainment. Over 20 million people visit Character.AI every month, using our technology to supercharge their creativity and imagination. Our platform lets users engage with tens of millions of characters, enjoy unlimited conversations, and embark on infinite adventures.
In just two years, we achieved unicorn status and were honored as Google Play's AI App of the Year—a testament to our innovative technology and visionary approach.
Join us and be a part of establishing this new entertainment paradigm while shaping the future of Consumer AI!
At Character, we value diversity and welcome applicants from all backgrounds. As an equal opportunity employer, we firmly uphold a non-discrimination policy based on race, religion, national origin, gender, sexual orientation, age, veteran status, or disability. Your unique perspectives are vital to our success.
Optimize multimodal models for efficient training and deployment by profiling hardware performance, developing high-performance GPU kernels, and scaling transformer implementations across distributed systems.
Own post-training research for legal AI models, developing SFT and reinforcement learning methods, reward systems, and evaluations to improve long-horizon reasoning and agentic workflows.
Research and exploit vulnerabilities in LLM applications and autonomous agents, building attack tools, agent harnesses, and reproducible evaluations that improve AI security and offensive security products.
Design and deliver production-grade optimization models and solver services for enterprise contact center workforce planning, scheduling, staffing, coverage, and resource allocation.
Design and deliver production-grade optimization models and solver services for workforce planning, scheduling, staffing, and resource allocation in a large-scale contact center environment.
