Each calendar in Cupla has an assignee: Me, My Partner, or Us. The assignee controls who the calendar’s events belong to in Cupla.
How to change a calendar’s assignee
Tap the menu icon (☰). Depending on your app version, it will appear either in the top-left corner of the Home screen or in the bottom-right corner of the tab bar.
Tap Calendar Settings.
Tap Calendar Connections.
Find the calendar you want to update.
Tap the edit button beside that calendar.
Choose the assignee: Me, My Partner, or Us.
Tap Save.
Why can't I choose my partner?
On iPhone the middle option — which shows your partner's name — is always unavailable, and that is by design rather than an error.
A calendar you connect belongs to you, so its events can appear as Me or, if you both treat it as shared, as Us. For events to appear on your partner's side of Cupla, your partner connects their own calendars from their phone, exactly as you did on yours.
Choosing Us also turns on Share event details for that calendar, so your partner sees full event titles rather than just busy time.