jQuery $.ajax error callback jqXHR status access under cross-origin policy

When a jQuery $.ajax request fails in a deployed application, the error callback provides the jqXHR object, status, and errorThrown values, which serve as the client-side diagnostics for identifying why the deployment returned an unexpected result.

However, cross-origin requests are subject to the browser's same-origin policy, which may prevent the error callback from accessing the full response body, limiting the diagnostic signal to status codes and generic error descriptions. Additionally, jQuery 3.x changed the error callback signature, and legacy code using the success/error shorthands may not receive the expected arguments.

What conditions cause jqXHR.status to reliably reflect the server's HTTP response code, and how can server access logs be structured to enable unambiguous matching with client-side error events? When does the error callback fire despite an aborted request, and which log fields best support cross-referencing with console-reported status values?