Web support

Makes an Expo app's web build a deliberate, working target: the web is declared or left out on purpose, platform files resolve the way Metro and TypeScript expect, nothing in the web bundle imports a module or calls a React Native API that fails in a browser, expo-sqlite gets its wasm, isolation headers, warm-up and single-tab lock, and the exported site is opened in a real browser before it ships. Two zero-dependency checkers prove it; every fact below was measured in headless Chrome against an export of a canonical Tasks app (Expo SDK 57, react-native-web 0.21.3, 2026-10-14).

Rules that must hold