Sebastian Crossa

Sebastian Crossa is a full-stack engineer who was born and raised in Mexico and is now based in New York City, New York, according to his personal site. He is the founder of ZeroEval, which went through Y Combinator in the S25 batch, and of LLM Stats.

Meeting Jonathan Chávez in College in Mexico

Crossa and co-founder Jonathan Chávez met in their first year of college in Mexico more than 7 years before launching ZeroEval, according to the company's YC launch post. They worked on side projects together and later built llm-stats.com. Crossa was a founding engineer at Micro, an email startup backed by a16z, and at Atrato (YC W21). Chavez was an early employee on Datadog's LLM observability team.

Building Evaluations That Learn From Mistakes

ZeroEval helps developers build reliable AI agents through evaluations that learn from their mistakes and improve over time. Developers define the evaluation criteria as a starting point.