Inconsistent performance with checkout extensibility

Topic summary

A developer has extended their app to support Shopify’s checkout extensibility but is experiencing erratic behavior with UI extensions on the thank you page.

The app includes extensions at two locations on the thank you page (above the ‘order status’ block and within the ‘customer information’ block) and two on the order status page. While the order status page works reliably, the thank you page blocks display inconsistently.

Observed Issues:

  • Sometimes both blocks appear
  • Sometimes only one block (A or B) is visible
  • Sometimes neither block appears
  • The inconsistency occurs randomly across different devices and browsers
  • Browser console shows an ‘order not found’ error when inspecting

The problem appears to be intermittent and not tied to specific device or browser configurations, making it difficult to diagnose. The issue remains unresolved and no solution or explanation has been provided yet.

Summarized with AI on November 9. AI used: claude-sonnet-4-5-20250929.

We’ve recently expanded our app to be compatible with checkout extensibility and are seeing a frustrating error on the thank you page. Our UI extensions are available in two places on the thank you page as well as two on the order status page. We have not had any problems with the order status page but the app blocks on the thank you page trigger erratically.

The two locations being used for the app blocks on the thank you page is above the ‘order status’ block (A) and then within the ‘customer information’ block (B). Sometimes both are visible, sometimes only A, others only B, and then there are times when neither are visible. If you use console within the browser’s inspect there is an error that says ‘order not found’.

The inconsistency is seen irrespective of device and browser (in other words, it happens at random across the board).