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

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.

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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