Loading/Suspense not working in Next.js 15 on one machine

[alchengan]

Summary

I was trying to implement loading pages with loading.tsx for an app I'm building with Next.js 15, but I couldn't get it to work. After doing a lot of researching trying to figure out how it works, I realized that loading.tsx was not working for me, despite following any tutorial I could find exactly.

Here's what I've done to try and figure out the problem:

• I created a new Next.js 15 project with a simple loading page to test and it still did not work.
• I tested a simple loading page in Next.js 14 and it worked as expected.
• I tried testing the same exact original Next.js 15 code on another computer and loading.tsx worked fine with the expected behavior.
• I verified that Next.js versions and Node versions are all the same between the two machines.

I thought maybe that Suspense was not working on the original machine so I basically repeated the process with suspense with the mostly the same results except Suspense also did not work in Next.js 14 on the original machine.

After all that, I still have no idea what the issue could be.

What could be causing this issue?

I've linked a repo with the code I've been using to test loading and suspense.

Expected behavior:

• On /home, the AwaitComponent should show "LOADING" for ten seconds before it is replaced with "AwaitComponent"
• When navigating to /about, a yellow box should immediately appear for ten seconds before showing "TestLoading"

Actual behavior:

• For both pages, it appears nothing happens for ten seconds before showing "AwaitComponent" or "TestLoading". Neither loading signifier appears for either page.

Additional information

No response

Example

https://github.com/alchengan/nextjs-notloading

[icyJoseph]

Could you share some specs of these machines? Windows? Mac?

[alchengan]

The machine that isn't working is Windows 10 x64, the one that is working is Windows 11 x64. Both have AMD processors. I also had a friend test and loading/suspense works on their computer, not sure what their specs are, but it is also Windows. Let me know if you need anything more specific.

[icyJoseph]

All with same Node.js? In the failing machine:

➜ node -p 'process.arch'

Does that match the OS bits?

[alchengan]

Yes, both machines return 'x64'

[icyJoseph]

What Node.js version? Browser versions?

[alchengan]

Both machines are running Node v22.16.0.
On the machine that doesn't work, I have tested with Firefox 139.0.4 (64-bit) and Edge 137.0.3296.83 (64-bit). Neither properly show loading or suspense.
On the machine that does work, I have tested with Firefox 139.0.4 (64-bit) and Edge 137.0.3296.68 (64-bit). Both properly show loading and suspense.

[alchengan]

Had the thought that maybe the issue was being caused by my firewall/antivirus and had those suspicions confirmed here. It seems Sophos blocks suspense/loading from working correctly in Next.js 15 and indeed the issue went away when I disabled web protection.
I couldn't figure out a way to get Sophos to ignore localhost while I'm developing without turning off web protection altogether so I just switched to a different antivirus and now everything works as expected.