Flash of "We can't find the internet" in Firefox (desktop/mobile) in Phoenix 1.8

[ponychicken]

Environment

• Elixir version (elixir -v): 1.18.1-otp-27
• Phoenix version (mix deps): Github Main (61cbfeb
• Operating system: Debian

Reproduction

1. Create a new project with phx.new
2. Put it on a server which has some latency (not your local box)
3. Open the page in Firefox mobile

Actual behaviour

You will see a very short (10ms) or longish (1000ms) flash of "We couldn't find the internet", when opening the page in a new window/ tab.

Expected behavior

No errors when opening a window

Notes

This makes the site looks immidiately unprofessional if you open it, and the first thing you see is an error message.

Bildschirmaufzeichnung.vom.2024-12-29.18-46-07.mp4

[03juan]

Check suggested solutions in #5102 e.g. #5102 (comment) ?

[ponychicken]

Check suggested solutions in #5102 e.g. #5102 (comment) ?

I can reproduce this in a variety of devices independent of whether the phoenix app is behind nginx or not. The supposed fix with adding proxy headers did not result in a change for me.