When does the Development Team participate in Product Backlog refinement?

The Development Team participates in Product Backlog refinement anytime during the Sprint because refinement is an ongoing process that helps ensure the Product Backlog is relevant, properly prioritized, and contains items that are well-understood and detailed enough for upcoming work. Engaging in refinement throughout the Sprint allows the team to collaborate with the Product Owner to clarify requirements, break down larger items into manageable tasks, and adjust priorities based on new information or changes in business context.

This continuous collaboration supports the agile principles of flexibility, responsiveness to change, and effective communication among team members, ensuring that they are aligned with the Product Owner's vision and are well-prepared for future Sprints. This also keeps the backlog healthy and optimized, making Sprint Planning more efficient and effective.