Like it or not, it is your responsibility to inform management if/when there’s a problem. It is their responsibility to decide what to do about it. Be transpare

Like it or not, it is your responsibility to inform management if/when there’s a problem. It is their responsibility to decide what to do about it. Be transparent about the impact that the current codebase is having on your estimates, bugs in your code, and job satisfaction. Analyze the situation and offer solutions. If you have provided management with accurate information, you will have no reason to feel bad about the outcomes, and there should be no surprises for anyone. I understand that you do not wish to offend your coworker who wrote poor code. That’s good, but it is also your responsibility to find a non-offensive way to communicate when their work is not ideal. I recommend using “code-first” language when talking about the code. For example, do not say “what you’re doing in this function is wrong”, say “this function is incorrect” (basically just never say “you” when discussing the code.) If they get defensive, remind them that your goal is code quality, and that you are not trying to be offensive. Be precise, informative, and most importantly: humble.