In Next.js 15, the hero banner rendered with next/image is the page's LCP element and loads late. Which prop fixes this?

priority is correct. It turns off lazy loading and preloads the image, so the browser starts downloading it early. This helps LCP (Largest Contentful Paint: when the biggest image or text block appears). The tempting loading="lazy" is wrong: lazy loading is already the default, and it would delay an above-the-fold image even more. Note: in Next.js 16, priority is deprecated in favour of the new preload prop.