Who owns the IP and the source files when you outsource game development?
Whoever the contract says, which is why this is settled before kickoff rather than at the final invoice. Assign all IP created under the agreement to you on payment, and require the working files at every milestone rather than at the end: layered art, project files, uncompiled source, build scripts. Name the formats. A studio that will only deliver flattened exports or compiled binaries leaves you unable to change the work without going back to them, which is a commercial position rather than a technical limit. Check separately what pre-existing tools or libraries the studio brings, and what licence you keep for them.
