Unable to install apps by shopify cli 3.0 node-react on different store using build files

Technical Q&A

Topic summary

Main issue: A Shopify CLI 3.0 node-react app was built (npm run build) and the build output (index.html + assets) was deployed to the server’s public folder with asset paths adjusted. After updating the App URL and redirect callback URLs to the server, installing the app via “Test your app” on other development stores redirects but returns the index.html content instead of an auth code, then shows the default NotFound page from the CLI scaffold.

Environment behavior: Works locally via ngrok; fails when served from the custom server with static build files.

Configured URLs: App URL set to https://my-server-name.co.in/. Redirects include /auth/callback, /auth/shopify/callback, and /api/auth/callback on the same domain. Accessing these callbacks directly appears to serve the static index.html.

Expectation vs result: Expected to see the app installation UI in the target development store; instead gets a NotFound page in Shopify admin after redirect with hmac/host/shop/timestamp parameters.

Open questions/next steps: Whether the build output contains backend code or only frontend assets remains unclear to the poster. The thread has no resolution; correct handling of authentication callbacks and deployment approach are still unresolved.

Summarized with AI on January 31. AI used: gpt-5.
1

The main issue is that I’ve created an app using Shopify CLI 3.0 node-react. Then I created build files using “npm run build”.

Then I placed build files (index.html and assets) in my server’s root in the public folder.

I’ve updated the paths in the HTML file from “/assets/file-name.ext” to “/public/assets/file-name.ext” as the assets are in my public folder.

And updates the App URL and redirects the app to my server URL

App-URL:- https://my-server-name.co.in/

App redirects :-

https://my-server-name.co.in/auth/callback
https://my-server-name.co.in/auth/shopify/callback
https://my-server-name.co.in/api/auth/callback

Now the issue is that when I try to install apps in my other development stores using “Test your app” in the overview section of the app.

Then It goes to the redirect URL (I’m not sure as I tried accessing callback URL’s directly through google search) but the response will be the index.html file contents not the auth code of Shopify.

And after that, it shows me the default “NotFound” page created by Shopify CLI 3.0 node-react directory structure.
URL :

https://admin.shopify.com/store/store_name/apps/SHOPIFY_API_KEY/?hmac=HMAC&host=HOST&shop=STORE_NAME.myshopify.com&timestamp=TIMESTAMP

Note: It works when fine when running locally using ngrok tunnel.

One more question does the build file contain a code of the node backend or just the frontend folder files?

Expected: UI for installing the app into the development store.

Can someone help me asap as I need to complete this for a client?