UX and development need to work tightly together. Plan a time to provide feedback.
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Let me suggest another way for both of you to think of this. Sounds like you’re development and he’s UX. These two roles need to be tightly aligned. Do you work in sprints? Do you have regular meetings to discuss these concerns so he doesn’t have to bother you unexpectedly? Do you guys have a design system so you don’t have to ask and he doesn’t need to tell you something is 3px off?