Parent node does not update when updating referenced entity child node I have a node type called page which references a node type called slider. I am using the Drupal 8 rest module to make updates to content. 

I make a PATCH request to update the slider content and it says the content had been updated. When I view the slider content I can see the updated version all good but when I view the page (which renders the reference entity) it is still showing the older revision of the slider. 

When I update the page by saving it to sending a PATCH to update the page then it shows the most recent version.

Is there a way to update a entity reference field (slider in this case) and also have the parent (page) also auto update with the changes?
When the referenced child node is updated in the database this triggers automatically a cache invalidation.

In this case there are three theming levels, page, parent node and child node. They all need to be invalidated when an entity involved gets updated. 

But this only works when they are tagged properly. You only need to have the children tagged, because tags bubble up to the parent.

For debugging check the response header X-Drupal-Cache-Tags. To enable this header copy sites/default/default.services.yml to services.ymland set:

  # Cacheability debugging:
  #
  # Responses with cacheability metadata (CacheableResponseInterface instances)
  # get X-Drupal-Cache-Tags and X-Drupal-Cache-Contexts headers.
  #
  # For more information about debugging cacheable responses, see
  # https://www.drupal.org/developing/api/8/response/cacheable-response-interface
  #
  # Not recommended in production environments
  # @default false
  http.response.debug_cacheability_headers: true


Now you can check the response headers in the browser debugging tools and see which cache tags are missing in the page.