What should a client handoff include?

When a colleague leaves or changes roles, I want the new owner to understand the client quickly without asking the same questions repeatedly. What should a client handoff include? I am considering a short relationship summary, current goals, communication preferences, recent commitments, open risks, and the next scheduled touchpoint. Should I include a transcript of past calls, or is a concise timeline enough? How do you capture context that is sensitive but still necessary for good service? I would also like advice on the handoff conversation itself: who should attend, what should be confirmed with the client, and how to introduce the new owner. Please share a checklist or example record that you have found reliable. The aim is continuity for the client, confidence for the new owner, and minimal disruption to ongoing work.