Make the exception visible.

Give uncertainty somewhere to go

I would design an exception path at the same time as the expected path. Missing information, conflicting values, and unavailable dependencies are ordinary parts of a workflow. If there is no place for them, they tend to become hidden work for the person maintaining the system.

An exception should show why it is waiting, who can resolve it, and what evidence is available. I want the original input to remain accessible so the decision can be revisited. A visible queue turns uncertainty into manageable work and makes recurring problems easier to recognize over time.