The argument at the end of a project is almost never about the work. It is about whether the master files, the plates and the trained identities were part of the deal. A deliverable specification settles that at the start, when it is a sentence rather than a negotiation.
For generative production it should name the reusable artefacts explicitly: master plates, trained identities, set specifications, prompt sets and the version of the model they were built against. These are the assets with the longest life in the engagement.
A studio that will not put the reusable files in the spec is selling a dependency. That is a legitimate commercial choice and it should be priced as one.
Who should own the master plates and trained identities?
The client, in our view. They are what makes the second campaign cheaper than the first, and retaining them converts a production relationship into a dependency.
What is usually missing from a delivery spec?
Colour space, the model and version the work was built on, and a statement about what happens to a trained identity at the end of its term.