PyData Boston 2025

Nathan Fulton

Nathan Fulton is a manager at IBM Research. He is an expert in large language models, formal verification, and reinforcement learning. Nathan earned bachelors degree from Carthage College in Computer Science and Mathematics, and a Ph.D. from Carnegie Mellon University's Computer Science Department. During his PhD studies, Nathan was a member of André Platzer's Logical Systems Lab and a core developer of the KeYmaera X theorem prover for hybrid systems. Nathan has previously worked as a Senior Applied Scientist at Amazon Web Services and as a Research Scientist at the MIT-IBM AI Lab.


Session

12-08
15:30
90min
Generative Programming with Mellea: from Agentic Soup to Robust Software
Nathan Fulton, Jake Lorocco

Agentic frameworks make it easy to build and deploy compelling demos. But building robust systems that use LLMs is difficult because of inherent environmental non-determinism. Each user is different, each request is different; the very flexibility that makes LLMs feel magical in-the-small also makes agents difficult to wrangle in-the-large.

Developers who have built large agentic-like systems know the pain. Exceptional cases multiply, prompt libraries grow, instructions are co-mingled with user input. After a few iterations, an elegant agent evolves into a big ball of mud.

This hands-on tutorial introduces participants to Mellea, an open-source Python library for writing structured generative programs. Mellea puts the developer back in control by providing the building blocks needed to circumscribe, control, and mediate essential non-determinism.

Horace Mann