Forecast of functionality by development team at the start of sprint planning
Topic one in the sprint planning section of the scrum guide states that the "Development Team works to forecast the functionality that will be developed during the Sprint".
Is this functionality represented only by items from the product backlog and improvements from previous sprint retrospectives, or can there be other items contained in the forecast even if they aren't present in either of these two lists?
There should be transparency over all of the work which a team plans to do during a Sprint, irrespective of its nature. If it isn't visible it cannot be tracked, or critiqued and challenged for its usefulness and relevance.