Rush starts on the desktop because serious agent work touches the real environment: files, browser state, local tools, credentials, and the subtle context of a person's machine. Browser-only products struggle here. Cloud-only products hide too much and ask for too much trust at once.
A local-first runtime gives the user a steering wheel. They can watch the work, intervene when needed, and keep sensitive context closer to home. That matters for trust as much as performance.
The long-term vision is broader than one device. But the first principle holds: agent software should feel grounded in the user's world, not rented from a distant black box.