My keynote speech from
@RubyConfAT 2026, recorded live on May 30, 2026 at Das MuTh theatre in Vienna.
“Obie Fernandez — author of The Rails Way and Patterns of Application Development Using AI, CTO at ZAR — tells the story of two chefs in two very different kitchens, building a fintech together with AI.
One chef is Sebastian, ZAR's lead architect: a perfectionist running a Michelin-star kitchen, where almost every line of ZAR Core — a stablecoin wallet serving underbanked populations across a 60+ country roadmap — touches users' money. The other is Obie: idealist, delegator, running three or four Claude Code sessions at once on internal tools, never reading every line, wearing the --dangerously-skip-permissions t-shirt on stage. "I'm a control freak and you're a free spirit." What they share: a total intolerance for technical debt. What differs is when they pay — Sebastian up front, with planning and specifications; Obie afterwards, with cleanup passes he finally has the bandwidth to make.
Highlights:
• The cautionary tale: kr8d, a vibe-coded fun-employment app that collapsed under its own featureweight
• Sebastian's kitchen by the numbers: a single 37,000-line cleanup PR, deleting five lines for every line added — while features keep shipping
• Obie's kitchen: five Rails apps, 1000+ commits, 400k+ lines in five months — Nexus, Agentis, Imperium, and Eventis, an event bus that's an active participant in the conversation
• The /goal workflow: plan, implement, ship, deploy, verify — then walk to the cafe and supervise from your phone
• Compounding: every problem you solve should make the next one cheaper — 75 custom skills, /fresh, /ship, and a skill that writes skills
• The two-week Flutter → React Native rewrite the team said would take two months
• Why Rails conventions matter more than ever: every shape choice you leave open is an invitation for the model to get non-deterministic
• Open source from ZAR: Servus (a disciplined, schema-validated service-object pattern), Amounts (fungible amounts with units and type safety), and Praxis (conceptual linting — RuboCop at the level of intent, not syntax)
• The uncomfortable truth about code review in the agent era — and why automated constraints will save us from ourselves
"Don't tolerate debt. It's not needed anymore."
piped.video/7QrXGLSZHvE?si=XsWn…