Our Story

At Libretto, we’re excited about Large Language Models because they represent the first time that traditional web and mobile developers can harness the power of AI easily without needing deep machine learning expertise. We also know, though, that our current developer toolchain isn’t powerful enough to enable us to depend on LLMs the way we depend on other parts of our software stack. This is where Libretto comes in. Libretto helps you monitor, test, and improve your LLM prompts so you can feel secure that AI is working for you and your customers exactly as you intended.

Our Team

Sasha Aickin


Sasha has been a programmer, engineering manager, and enthusiastic technologist for the last 25 years. He has managed large Engineering and Product teams as the Redfin CTO and contributed to major open source web infrastructure as a one-time member of the React core team. Sasha is passionate about leading teams in a humane way to create beautiful, usable software that makes users smile while making them more productive.

Alec Flett

Senior Software Engineer

Alec built his career around mapping the messy, real, and human world into software. Whether it is knowledge graphs at Metaweb and Google, troves of survey data at Google Consumer Surveys, or layers of geospatial data at UrbanFootprint, he has built tools to help people find deep insights from their data. In addition Alec has always been a champion of the web, having worked on both Firefox and Chrome.

Justin Rosenthal

Senior Software Engineer

Justin is a software engineer who has spent 15 years building products that deliver tangible utility to people. While he’s a self-proclaimed generalist, much of his career has been spent designing, implementing, and operating high throughput distributed systems across a number of verticals, including social gaming, consumer messaging, and enterprise software. He was the co-founder and CTO of MessageMe (a mobile messaging product that was acquired by Yahoo!), and more recently an infrastructure lead for Google Cloud focused on modernizing the App Engine stack.