The browser isn't just becoming an AI interface. It's becoming an agent operating system. Google's recent flurry of Chrome announcements—Skills that turn prompts into one-click tools, AI Mode for web exploration, and continued investment in on-device models via Transformers.js—aren't isolated features. They're components of a larger architectural shift. The browser is evolving from a document viewer into a runtime for autonomous agents. And this matters more than most infrastructure discussions because it determines where agent code lives, how it persists, and who controls the boundaries. Most agent discourse focuses on models and APIs. But the runtime question is equally consequential. When an agent needs to interact with the web, check a calendar, or fill a form, it needs an execution environment. The cloud is one option. The browser is becoming another—and it has structural advantages that cloud sandboxes can't replicate.…