New Software Agency – looking for best practices when handing off software to another team

We are a small software agency. We just completed a fairly decent sized project, and the internal team is taking it over. While we aren't leaving on bad terms in any way shape or form, and this is expected, I want to make sure we do this in a way that protects my agency. We are thinking of creating a quick hand-off/termination contract with some stipulations, such as having another dev outside our team work on the software voids any warranty they might have with us. What are some other best practices or things to think about here?