If you deliver a user story in a previous sprint and then need to modify it in a new sprint, what do you do?

Example: Change the UI of a screen or change a technical detail in how it was previously implemented (ie: refactor).

If you delivered a user story in a previous sprint and then need to make changes to that feature in the current sprint, what do you do?

Examples:

• Change the user interface (UI) of a screen.
• Change a technical detail in how the feature was previously implemented (i.e. refactoring).