When running a NextJS app using "App Routing" in a Firebase emulator, it doesn't handle 404 page generation properly. The default NextJS 404 page generates a "This page could not be found" error styled in the middle of the page. When running in Firebase Emulator suite, the 404 page generates as . This makes it impossible to test custom 404 page appearances for a NextJS application within the Firebase emulator.

[REQUIRED] Environment info

firebase-tools: 13.24.2

Platform: Docker running inside macOS

[REQUIRED] Test case

https://gitlab.com/MidnightLightning/firebase-404-test

[REQUIRED] Steps to reproduce

Run docker compose up, then visit http://localhost:25602/foobarbaz.

[REQUIRED] Expected behavior

To see the NextJS custom 404 page (text "This page could not be found" in the center of screen)

[REQUIRED] Actual behavior

A plain textual response of "Cannot GET /pathname"