CustomEvent not propagated correctly

Shopify Apps

Topic summary

A custom configurator on Shopify has stopped functioning correctly due to JavaScript Custom Events failing to propagate from shadow DOM elements to the window level.

Timeline & Symptoms:

  • The issue began suddenly after 10pm yesterday
  • Previously working event propagation now only reaches the next component in the DOM tree instead of bubbling to the window
  • Interactive features like option panels have become unresponsive as a result

Suspected Cause:
Potential undocumented changes to Shopify’s event handling system, specifically affecting custom events originating within shadow DOM components.

Current Status:
The developer is seeking confirmation from others experiencing similar issues, as no advance notice was provided by Shopify regarding any modifications to event handling behavior.

Summarized with AI on November 1. AI used: claude-sonnet-4-5-20250929.
1

We are experiencing an issue with our custom configurator on Shopify. Our configurator relies on JS Custom Events dispatched from within a shadow DOM to drive its interactive features. Recently, we have observed that these events are not propagating to the window as they previously did, causing elements such as option panels to become unresponsive.

Yesterday until 10pm everything was working fine. Then it stopped to propagate the events. If we have nested custom components, event is propagating only to next component in the DOM tree.

We suspect there may have been changes in Shopify’s handling of custom events particularly those originating in the shadow DOM that are impacting their ability to bubble up correctly. We have not received any prior communication from Shopify regarding modifications to event handling behavior, so this issue has come as a surprise.

Any one is experiencing similar issues.