Generative artificial intelligence (AI) and large language models (LLMs) are bringing disruption across industries, changing the way we create images, text, and code. Within architecture, engineering, and construction (AEC), these tools will transform the design and construction process. Professionals in AEC must stay informed of this fast-moving technology to remain competitive and aware of the innovative design-and-make software. TileGPT is an LLM-powered prototype developed within Autodesk Research to generate optimized designs using intuitive and flexible text-based input. This session will cover the technical capabilities of this generative AI system, which uses optimization to enable rapid design exploration. It presents example use cases within AEC design, including performance-driven generation of building massing, site design, facade layouts, and more. With generative AI, Autodesk Research is expanding what's possible within design tools, and showcasing new design experiences that are fast, intuitive, and accessible.