A SharePoint 2013 tasks list created through code was not connecting to the Out-of-the-Box (OTB) Project Summary webpart.
We created a task list through code using the REST api. This is fairly simple to do with the gd-sprest library, refer to this page for additional details. Regardless of the library you use to create a list, you must set the list creation information. The minimum information you need to provide is the title of the list and the list template type. Refer to this page for a list of the template types.
When clicking on the link to “Create a Task List”, provided by the project summary webpart, I noticed the template type was set to 171. This template was unknown to me, since I’m used to only dealing with 10x list template types. When looking this up, the template being referenced is TasksWithTimelineAndHierarchy. I updated the solution to create a list using 171, and the project summary webpart was now connecting to it.
When creating a tasks list via code for SharePoint 2013, make sure to use template 171 if you want the list to work with the “Project Summary” webpart.