Hi, I’m Brian

I’m a staff software engineer and two-time founder who takes ambitious products from prototype to production. I’m at my best in ambiguous, high-leverage work: shaping the product, building the first durable version, and creating systems that help teams move faster.

I work at Square, leading zero-to-production product and platform work across reporting and restaurants. My current focus is AI-native engineering, especially harness engineering: giving agents the context, boundaries, tools, and feedback loops to build quickly without trading away correctness, reliability, or operational rigor.

I write about practical ways to make software teams faster and more effective, including context engineering, durable documentation, automation, and continuous learning. My Software Engineering Toolbox collects many of those ideas.

Before Square, I helped build products and platforms at Valimail that make email more trustworthy.

Sports has shaped both my life and my work. I was the starting center for Harvard men’s basketball and later played professionally in four countries. I’ve also helped bring people together through PeacePlayers, DUPLAYS, and Playpass.

Playpass helps sports managers run leagues and tournaments with an easy-to-use online league scheduler, plus registration and payments, memberships, bookings, waivers, and websites with stores. In 2013, Endeavor Global named me a “high-impact entrepreneur”.

You can contact me on X at @BrianSigafoos. You can also find me on LinkedIn, GitHub, and Goodreads, or browse my reading list.