Audit and test every non-happy-path state in my app, and fix the ones that are broken or ugly. 1. Empty states: every list, search result, dashboard, and feed gets tested with zero items. Each should show a useful empty state (what this is, what to do next), not a blank area, a broken layout, or a 'undefined' string. 2. 404 and bad routes: visit a route that does not exist, a record ID that does not exist, and a record ID belonging to another user. Each should render a proper not-found or forbidden page, not a crash or an empty shell. 3. Failed requests: simulate API failures (500s and network errors, using my test tool's request interception) on the main screens. Every screen that loads data needs a real error state with a retry, not an infinite spinner or a silently empty page. 4. Loading states: check that slow requests show something sensible and that rapid navigation does not flash stale content from the previous screen. 5. Offline: throttle the browser offline and reload the app. At minimum it should tell the user they are offline instead of appearing broken. 6. Form failures: submit each important form with a simulated server error and confirm entered data is preserved and the error is visible, not a lost form. Write tests for the states that can regress (empty states, 404s, error states on the main screens) and fix the UI anywhere the current behavior is a crash, blank page, or infinite spinner. Do not build elaborate error pages; clear message, retry path, and preserved user data is the bar. Do not swallow errors silently anywhere. Give me: the state-by-state audit results, the UI fixes applied, and the tests added per state.