mediumHallucinated APIsFetch API

The invented flag

A developer asked an AI assistant to add a request timeout to a fetch call that hits a slow internal API. The suggested option compiles fine and never errors, but the request still hangs well past the intended limit.

fetchReport.js

async function fetchReport(reportId) {
  const response = await fetch(`/api/reports/${reportId}`, {
    timeout: 5000,
  });
  if (!response.ok) throw new Error('Failed to load report');
  return response.json();
}

Why does this fetch call still hang past 5 seconds?

The Fetch API has no timeout option — passing it is silently ignored, so the request runs until the browser's own default timeout.

response.ok is undefined until the promise fully settles.

reportId is not URL-encoded before being inserted into the path.

fetch requires an explicit method: 'GET' for a timeout to take effect.