How much of the Product Backlog must be defined during the Sprint Planning meeting?

The amount of the Product Backlog that must be defined during the Sprint Planning meeting is primarily focused on creating a forecast for the Sprint. This means that the Scrum Team needs to collaborate to determine which items from the Product Backlog they can realistically commit to delivering by the end of the Sprint.

The Sprint Planning meeting is designed to establish a clear and actionable Sprint Goal based on the prioritized items in the Product Backlog. This involves discussing the items that are of highest value and ensuring that they are well understood by the team so that they can plan their work effectively. The selected items provide a foundation for the work that will be done during the Sprint, allowing the team to forecast what they can achieve within the time frame.

While it may include higher-priority items to some extent, the requirement is not to define all of them nor just a brief summary of tasks. Instead, it focuses on sufficient detail so that the team can make informed decisions and provide a clear expected outcome for the Sprint. Thus, the emphasis is on creating a forecast that aligns with the team's capabilities and understanding of the work involved. This approach ensures that the team can remain flexible and adapt as they progress with their work during the Sprint.