Over the past year, Microsoft has been quietly but steadily reframing Zero Trust for an AI-first world, and the company’s new guidance makes that shift explicit. With Zero Trust for AI (ZT4AI), Microsoft is extending familiar security doctrine into the messy reality of models, agents, prompts, plugins, data pipelines, and autonomous workflows. The message is simple but consequential: if AI systems are now making decisions, touching sensitive data, and acting on behalf of users, then they...