At what point can a new custom product development project be considered complete? When the product meets all the points of the specification? When the customer had run out of requests for modifications (i.e., never)? When the product has been successfully put into production (and what is "successfully")? Or maybe when the customer began to profit from the new development?

None of the participants in the customer-executor relationship can make this decision alone. But someone can take the lead and make a proposal. We, as contract developers, have completed 20+ projects, so it is logical for us to take the lead. Sometimes customers work with us on their first product development project! First time! So we suggest when a development project is complete. Hmmm, it will never actually be finished (and thank goodness, so the product will live on). It's just that the development contract will be replaced by a production implementation contract and so on.

But even the completion of the development contract is a non-trivial point. After all, you can't expect the spec to close all the uncertainties, which are bound to happen because we are creating something new. If it was already known, then there would be no need to develop it. You could, of course, try to develop a comprehensive spec. But then its development will become a full-fledged project, the timing and cost of which will never satisfy the customer. This should not be seen as a reason not to try to make detailed spec at all, but the fact that you can not always embrace the immensity, it is certainly worth taking right away.

This means that from the get go it makes sense with the customer at least in words to discuss the question of where the boundaries of responsibility of the contract developer. At least in the form of general principles. Let these principles not be formulated in the dry language of standardized documents, let it be a correspondence by e-mail or WhatsApp/Telegram (voice on the phone is worse, I think you understand why?), where you tell the customer in three sentences what's the difference between the contract development and introduction into production, and prototype – from a serial sample.

Even this kind of correspondence will increase the chance of preserving the relationship in case of any disputes at the end of the project. Yes, this discussion will be like negotiating the terms of a marriage contract shortly before going to the registry office, but both parties should understand that all this is done to divide responsibilities and reduce the likelihood of conflict, rather than to squeeze more from each other after the divorce.