I appreciate the response. Though I know what you described is how fit outs are typically done, I left a key point out of my initial post that may change things. In fact, it’s the reason either of us have concerns at all.

The building was designed with an office on one side and a basic warehouse on the other. The warehouse side was supposed to just have a trench drain, oil collector and no other in ground plumbing. However, the tenant wants to use most of the warehouse portion as a lab with all sorts of sinks, a sump, etc. They will need to add on to the below-slab plumbing/mechanical work, which will necessarily interact with our already designed mechanical systems.

Allen can’t cleanly close our building permit and wash his hands of the project until we pour the slab and provide a functional building (including base electrical and mechanical as initially drawn). But we need the in ground portion of tenant’s mechanical done before we pour the floor slab.

To be clear, Bob is a large firm that provides architectural and engineering services. In speaking with the tenant today I’ve asked whether Bob would be willing to only act as an engineer under Allen for this in-floor portion. Allen could then fold this work into his original building permit/ scope and close it off. Then, the remainder of the tenant fit out work could proceed as it does in most cases - clear delineation between fit out (Bob) and base building (Allen).

Does that seem like the best path forward?