Thanks for your response, but my build number is declared in my project as you show. My issue is that if a build is submitted to App Store Connect that has the same build number as a build that was previously submitted, App Store Connect silently auto-increments the build number and accepts the upload. This is not what I want as this results in the build number I see on ASC not matching the build I uploaded. But this only started happening relatively recently. Before, in this situation, the upload would be rejected, which is what I want.

Thank you so much. I tried searching the forums and google but was only finding older posts about people wanting the opposite of what I was looking for.