Versions >5.1.14 causing TypeError: Illegal invocation error

[Devr-pro]

Describe the bug

I was on 5.1.16 and after building the app and preview I was getting this Illegal invocation error, tried a lot to debug and found out the cause, rolling back to 5.1.14 makes things right and working again.
(Things were working well on dev server, but breaking on previewing the build)

Reproduction

Repo link

Go to the / route page (The error only seems to be on / route)
https://github.com/Devr-pro/dormster-app/tree/update-svelte-to-5.1.16

Deployed url

Logs

index-client.EUrO2unW.js:1 Uncaught (in promise) TypeError: Illegal invocation
    at R (index-client.EUrO2unW.js:1:3033)
    at wr (index-client.EUrO2unW.js:1:2487)
    at zp (4.DQXZKnv6.js:3:3801)
    at app.CB1Rbgs2.js:2:3955
    at props.C0W6GDie.js:1:2450
    at Xt (index-client.EUrO2unW.js:1:8424)
    at V (index-client.EUrO2unW.js:1:9115)
    at q (index-client.EUrO2unW.js:1:4543)
    at qr (index-client.EUrO2unW.js:1:5566)
    at props.C0W6GDie.js:1:2444

System Info

System:
    OS: Windows 11 10.0.22631
    CPU: (12) x64 AMD Ryzen 5 5625U with Radeon Graphics
    Memory: 3.97 GB / 15.34 GB
  Binaries:
    Node: 20.11.1 - C:\Program Files\nodejs\node.EXE
    npm: 10.2.4 - C:\Program Files\nodejs\npm.CMD
    pnpm: 9.12.3 - ~\AppData\Local\pnpm\pnpm.CMD
  Browsers:
    Edge: Chromium (130.0.2849.46)
    Internet Explorer: 11.0.22621.3527
  npmPackages:
    svelte: 5.1.14 => 5.1.14

Severity

blocking an upgrade

[Conduitry]

We need an actual reproduction.

[Devr-pro]

Well, I tried to create one in codespaces but it seems to work fine there, I don't know what's causing me issues in my local app, Will try to make a local reproduction and update here asap

[Devr-pro]

We need an actual reproduction.

I have updated the link, a repo is provided and also the deployed url

[dummdidumm]

This isn't a minimum reproduction, this is just your entire app. I had to delete the auth-related stuff from the repository to get it working. Provide an actual minimum reproduction next time.

That said, this is definitely a bug. My guess is it has something to do with a combination of @sveltejs/enhanced-img and the attributes optimization, because it fails at that point. It's strange because even if I run in dev mode with dev: false in the compiler options I get a different output compared to build. This likely came in as a result of #14249, and may go away after #14269 is done.

[Devr-pro]

This isn't a minimum reproduction, this is just your entire app. I had to delete the auth-related stuff from the repository to get it working. Provide an actual minimum reproduction next time.

I agree, apologies for that, I'll try to make a minimal reproduction.

[dummdidumm]

Update: Confirmed that this will be fixed by #14269

I agree, apologies for that, I'll try to make a minimal reproduction.

From my side it's not needed right now, since #14269 will fix this