The age of spending weeks writing product documents and manually testing patches is officially dead, replaced by a chaotic but thrilling era of "machine-speed" security where adversaries and defenders are locked in an AI arms race. Hart Rossman, Vice President of Security for AWS, explains that to survive this shift, organizations must ditch their bureaucratic "fast-twitch" bottlenecks and start co-building with AI from the very first prompt, using "steering docs" to automatically enforce security guardrails. As AI democratizes coding, the traditional "two-pizza" DevSecOps team is shrinking down to nimble "two-slice" squads, proving that the future of secure software development belongs to those who use AI to build the foundation, leaving humans to reason through the final, complex 20%.