Shopify run dev CLI error - Cannot read properties of undefined (reading 'forEach')

Shopify Apps

Topic summary

Shopify CLI crashes with the error “Cannot read properties of undefined (reading ‘forEach’)” when working with extensions, notably after adding a Checkout UI extension.

  • Impacted commands: npm run dev (after adding a checkout UI extension) and npm run generate extension (when starting by adding the first extension instead of the Remix option).
  • Environment reported: macOS, Node.js v18, Shopify CLI v3.53.1.
  • Troubleshooting tried: – --reset flag and reinstalling the CLI; issue persists.
  • Verbose output: last GraphQL calls observed are FindApp and allAppExtensionRegistrations before the crash.
  • Reproduction path noted: create app via “npm init @shopify[email removed] (user typed @Shopify_77 [email removed] choose “Start by adding your first extension,” then run npm run generate extension → same error.

No workaround or fix identified in the thread. Likely a CLI regression related to extension scaffolding/registration. Screenshot/logs are central to understanding the failure. Discussion remains open with unresolved cause.

Summarized with AI on January 7. AI used: gpt-5.
1

Hello,

I’m having error running my npm run dev scripts. It was running fine at first, and then I ran new extension for checkout ui, after that it crashes everytime I run it. I tried running it with – --reset and tried reinstalling CLI with no luck.

kulit_0-1706081273513.png
kulit_0-1706081273513.png585×554 61.2 KB

When running --verbose
query FindApp and query allAppExtensionRegistrations was the last few queries being made.

Im running macOS and node version 18 CLI version 3.53.1

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2

Having the same issue. But for me to recreate, I created the app with “npm init @Shopify_77 /app@latest” and for get started building your app, instead of the remix option I chose Start by adding your first extension. Once I try to run npm run generate extension it throws me that same error.

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