captureInstallOffer

Remarks

Chromium fires beforeinstallprompt as soon as it judges the site installable, and it never fires it again. That is routinely before React has hydrated, so a listener added from a component effect misses it: measured on Android Chrome 149, with the manifest valid, every icon served and the service worker registered, the install prompt never appeared at all.

Called from instrumentation-client, which Next runs before the application starts — the earliest hook the framework offers. Several earlier attempts are worth not repeating: an inline <script> and a <script src> rendered from the root layout both reached only Next's streamed payload and never executed, and next/script with beforeInteractive is documented for external src scripts and emitted nothing for inline content.

Preventing the default is not optional: left alone the browser shows its own promotion alongside ours, and the learner is asked twice by two surfaces.