Mobile tests are where the bugs actually live. A signup flow that works on an iPhone 15 falls apart on a lower-end Android because the keyboard pushes a button off-screen. A push notification mid-flow leaves the app in a state nothing else reproduces. Memory pressure on a four-year-old Android does things you can't make a simulator do. I wrote simulator-only tests anyway, for years. Real-device runs took ten to thirty minutes per cycle, the device farm queue was unpredictable, and CI on physical hardware was expensive enough that someone always wanted to talk about cost. So tests got written for the simulator, the device-specific bugs found their way to production, and we caught them in Sentry instead of in CI. The thing that changed wasn't a better device farm or a faster CI. It was Claude Code writing the tests, BrowserStack MCP driving the devices, and the whole loop closing inside a single session.…