Vibe coding is changing how software gets built. But as AI agents write more of our code, the question security teams are asking has shifted from "Can AI build this?" to "Can I trust what AI builds?". At Replit, we believe the answer has to be yes, not through blind faith, but through architecture. Every layer of the Replit infrastructure where customer code runs, from the development sandbox to the production deployment, is designed with defense in depth. The Replit platform itself, our control plane, is also implemented with these principles in mind. No single control is the last line of defense. Every layer assumes the one above it might fail. This thread is a detailed walkthrough of how we think about security across the stack, written for the people who need to evaluate it: CISOs, security engineers, and teams considering Replit for production workloads. 🧵