The Wikimedia REST API's /page/summary response contains content_urls and api_urls keys that provide convenience lists of various URLs of potential interest to the consumer.  These lists appear in other endpoint responses as well, as the page summary response is transcluded in various places throughout the REST API. 

Currently, these URL strings are constructed erroneously using unencoded page title strings.  A proposed patch (https://gerrit.wikimedia.org/r/#/c/mediawiki/services/mobileapps/+/489329/) applies encodeURIComponent to encode these before including them in URLs. 

Since this endpoint is advertised as stable[1], I'm announcing the change here in advance.  Barring any objections, the change will be deployed late next week.

[1] https://en.wikipedia.org/api/rest_v1/#!/Page_content/get_page_summary_title
--