In this illuminating conversation from the frontier of AI-native startups, William Fairbairn, founder of Zalos.ai and part of Y Combinator's class of 2025, reveals what it takes to build at Silicon Valley velocity. Just five weeks after launch, Zalos is already deployed with major enterprise customers, automating finance workflows through computer-use agents that execute tasks like humans—extracting contract terms, initiating billing, and reconciling cash. Fairbairn's insights into Y Combinator's evolved wisdom for the AI era, particularly "forward-deployed engineering", demonstrate how the startup playbook has been fundamentally rewritten. With funding bars rising to $2 million ARR in 12 months just to reach Series A, and "supernovas" scaling from $1 million to $100 million in 18 months, this postcard from the edge of software leadership captures the intensity and opportunity of building in an era where the rules change weekly.