Theme app extension assets vanishes every afternoon — glitch in the Matrix or just Shopify?

Extensions
1

Hey everyone,

I’m running into a strange bug with a Shopify theme app extension I built (with a Remix backend). Each day, sometime in the afternoon, the extension just… stops rendering.

Here’s what’s odd:

  • The JavaScript assets from the extension aren’t just failing to load — they’re not even present in the HTML. No <script> tags, no requests in the network tab. It’s like Shopify just forgets the app block exists.
  • Nothing changes in my code or deployment — the issue just starts happening out of nowhere.
  • Other parts of the app (like function APIs and Remix routes) stay fully functional.
  • If I switch to a different theme during the issue window, everything works instantly. And the theme app extension, will only start working again on the original theme after waiting for the next morning.

It feels like something internal to Shopify — maybe CDN caching, theme-asset sync issues, or some deployment lag — is causing the blocks to vanish temporarily.

Has anyone experienced anything like this? I’ve been able to reproduce it consistently across several days. I’d love to know if others have seen or solved this kind of problem before.

Thanks in advance!

2

Can you share your theme block’s main .liquid file?

Maybe there’s a clue there.

Are you referencing files that are built from a bundler in the liquid files? You have to be careful to make sure the bundler is running, is emitting files and that all of the files are compatible within the assets directory.

3

Hey @Dylan, thanks for the reply!

Here’s the main Liquid file from my theme app extension:

<script type="module" src="{{ 'cart-script.js' | asset_url }}"></script>
<script type="module" src="{{ 'cart-totals-display.js' | asset_url }}"></script>

{% schema %}
{
  "name": "Cart Script",
  "target": "body",
  "settings": []
}
{% endschema %}
4

Got it, so:

  1. Are these scripts created by a JS bundler?
  2. If so, are these scripts also creating the mounting point element on the theme too?

I don’t see any other HTML elements besides these two scripts. So not sure how they’re functionally adding visuals to the page.

5

To clarify, the .js files aren’t built using a bundler — I manually create them and drop them into the assets folder, then reference them in the .liquid template using the tag.

In the case of cart-script.js, it’s not meant to render any visual elements by default. What it does is check if a user is a club member (via a Shopify app proxy endpoint) and, if they are, inject a “Download PDF” button into the cart UI. This button triggers a request to generate and download a custom PDF based on cart contents and customer ID. So even something as simple as a console.log() should confirm the script is loaded.

The issue is that these scripts completely stop loading at some point later in the day — not intermittently, but very consistently — and then start working again the next morning without any changes on my end. During the affected time, even a basic console.log in the script doesn’t show up in the console. So it’s not a rendering issue; it’s that the browser doesn’t seem to load the script at all anymore.

Appreciate any insight into what might be causing this. Let me know if anything sounds off.

6

Is this issue happening in the deployed version of your app?

Or is it only happening when you’re actively testing with shopify app dev to publish your theme block to a dev store?

7

It’s happening when testing with shopify app dev. Basically the app is still in development and hence this issue is crushing my efforts and focus while working on it. And i’m also fearing having this same issue in deployed version later on.

8

There’s a bug that I’ve been complaining since 2023 where if the store theme has an unclosed <head> tag, the theme app extension scripts and css won’t load.

Also if the <body> or <html> tags are unclosed, the theme app extension liquid code won’t also load.

Check the store theme liquid files to see if you have an unclosed body, head or html tag.

1 Like
9

That could be it. Any unclosed <script> tag will cause problems for scripts following it, because the interpreter doesn’t know when the first one ends.

But that’s an HTML level issue, not a Shopify one. I guess Shopify could have some kind of validation logic, but that’s a designer mistake usually.