Question: What are the time-boxes for Nexus events ?

Hello,

Nexus guide is vague in Nexus events duration & if it is time boxed or not , specially for sprint planning & retrospectives. actually the sentence "They are time-boxes in addition to their corresponding Scrum events." mentioned in the nexus guide is not clear for me.

can anyone mention the time box for each nexus event & if its separate from the scrum events or included in it?

Thanks