Fetch error after updating the shopify-app-express from v5 to v6

First of all, thanks for the publishing this template which makes my work easier.

Recently i would like to update the Shopify API version to 2025-10. but that requires the update of @shopify/shopify-app-express from v5 to v6.

After updating this package, the graphql and rest api call returns fetch error.

GraphQL

The exact version change on my setup is updating @shopify/shopify-app-express from 5.0.4 to 6.0.3.

That involves @shopify/shopify-api version change from 11.5.0 to 12.1.2 and in 12.1.2, the node-fetch package is removed. I wonder if it is related.
https://github.com/Shopify/shopify-app-js/blob/main/packages/apps/shopify-api/CHANGELOG.md

In addition, https://github.com/Shopify/shopify-app-template-node is not yet tested with @shopify/shopify-app-express 6.0.3. I found that in web/node_modules/@shopify/shopify-app-express/dist/cjs/middlewares/has-valid-access-token.js

If i comment the line 13 above, the embedded app default landing page could trigger the rest call but it failed with the fetch call just like the graphql client as shown in the 1st image.

REST

Any help is appreciated. Thanks.

Reproduce the upgrade from @shopify/shopify-app-express 5.0.4 to 6.0.3 and start by inspecting web/node_modules/@shopify/shopify-app-express/dist/cjs/middlewares/has-valid-access-token.js. Trace the GraphQL and REST calls that return fetch errors and compare the related @shopify/shopify-api versions. Done means the template’s API calls work after the v5-to-v6 upgrade.