Error State

Error states come in a few levels. Field level: one input has the wrong format, so show a hint right below it. Block level: one card or list fails to load, so show "Failed to load. Retry" in its place. Page level: 404, 500, or no connection, so the whole page shows an explanation and a back button. Action level: a save fails, so tell the user with a toast or an alert banner.

A good error message has three parts: plain language ("Couldn't connect to the network," not "Error 500"), the cause (if you know it), and a way forward (a retry button, back to home, contact support). If one block fails, don't let the whole page go blank.

When AI writes code, it often only covers the success case and skips the failure branch, so explicitly ask it to handle errors.