Sebastian Tirelli

AI systems

Harmony AI memory and retrieval platform

Worked on a hybrid retrieval stack combining vector similarity, graph traversal, and keyword search. Built the benchmarking pipeline that scored the system against the LongMemEval and LoCoMo papers, the two canonical long-context memory benchmarks, and turned the results into the signal the team used to decide what to ship next.

Agentheon Founding AI engineer · AI SDR platform

Built the product end to end as the only engineer. LangGraph agents orchestrating outbound research and outreach, async workers, real-time dashboards, human-in-the-loop review for every generated message, and a Next.js app on top. Owned the infrastructure, the prompts, the evaluation, and the design.

The most useful thing I learned in that year was how fast a LangGraph stack accumulates cost and reliability debt when nobody is watching. Most of my current writing is downstream of that observation.

Leadership and platform

OnTop Senior engineering manager · fintech

Ran five engineering teams, thirty-five plus engineers reporting through me. The core piece of work was rebuilding the entire payment workflows and pricing models end to end, which brought processing errors down by 40%.

Around this time I started the Berkeley ML/AI postgrad, which is what eventually pulled me back into hands-on building.

TestGorilla Senior engineer to engineering manager

Joined as a senior engineer, ended as a manager running a product-area team. Useful stretch, because I got to do the transition inside a single company.

Before that, engineering roles at Altoros (a Head Start platform serving over one million children in the US), Making Sense (four years across client teams), Hinch.as (early product engineer), and a two-year stint inside a government organization early in my career. One year teaching a software engineering course at UTN, which was the best way I found to stress-test my own fundamentals.