Why would it be your fault? Is his assignment to understand what you’re doing? If yes it sounds like you hesitate to play your role in this relationship. Is his

Why would it be your fault? Is his assignment to understand what you’re doing? If yes it sounds like you hesitate to play your role in this relationship. Is his role to work with you on a codebase new to him? Similarly you need to help him no matter his seniority. I Know sometimes having people lifting the veil of your code can be intimidating but if I were your manager that would be my first suspicion if I heard complaints in the context of the relationships outlined above, i.e. that you have concerns about the quality of your work. I might be wrong, but this is an anecdotal perspective to keep in mind before you escalate.