Having a junior engineer show up to "shadow" you and you've got them filing an HR complaint minutes later is not a commendable trait. It's a total dick move to

Having a junior engineer show up to "shadow" you and you've got them filing an HR complaint minutes later is not a commendable trait. It's a total dick move to rope them into your problem. They (presumably) have nothing to do with any of the politics or age discrimination that might be going on. They're just some young engineer that got something like their dream job and (presumably) want to learn from a principal engineer with decades of experience. Teach them what you know and don't make your problem their problem. More importantly, it's just unwise. They received a very important piece of information and reacted instead of taking some time to think about the best course of action. Reacting in a way that causes the junior engineer to report it to HR sets off a chain of events that may not be in your interest. Because drum roll.... HR is not your friend. Their role in this scenario is to protect the company. And the easiest way to protect the company is to root out the malcontent in a way that doesn't get them sued. Especially in this sort of scenario where someone with political capital in the organization is gunning for you. Reaching out to the CEO just sealed his fate. It's not a matter of principles or doing good work. It's having a basic understanding of how an organization works and acting in a way that will maximize your and/or the companies well being.