Classmate shops my unpublished ideas around and contacts my advisors, I'm about a year into some exciting research, with some early results that many professors are interested in following the progress of.  I have two advisors.
I recently learned that my graduate classmate, from a different lab, has been shopping my ideas around, interviewing with other labs at other universities, apparently to try to do something similar, gain a collaborator, etc.  He told he did this, which made me uncomfortable.
He's also contacted one of my advisors, he says.  I believe there is no stopping him at this point.  He will likely contact my second, more renowned advisor too, with the goal of working with them, and knowing about all of my recent progress in research, since him and I are very close friends.
I feel he's behaving like a leech and acting like a desperate leap-frogger.  And I regret talking so much about my progress, which he now uses and shops around, perhaps misrepresenting the ideas and techniques as his own.
How should I deal with these feelings?
On the one hand, I feel he has complete freedom to contact whomever he wants, and shop whatever unpublished ideas he wants, to build his own career.  On the other hand, I feel like I am just supplying and enabling a plagiarist.
Should I cut contact with him, or be proud that he is excited about my work and wants to emulate me?
I don't contact his advisors or shop his ideas around, for example.
What you describe sounds very odd. It's hard to know exactly without being party to the conversations (and you don't know exactly what this person is saying to others about your work), but my initial impression is that this is more likely to hurt your friend than you. I also wonder if they're in a good space - it sounds less like someone trying to build a career and more like someone who might be a bit lost and confused about their own directions.
That said, it would absolutely be appropriate for you to ask that they stop talking about your work to third parties. It's one thing if it happens to come up in related conversation centered on their own work, it's another thing to shop it around actively, whether giving you credit or not. There are definitely kinder ways to phrase this and harsher ways. I'd probably start with kindness just because they are more likely to react positively. You can thank them for being excited about your research, but share that you'd like to spread your own work and ask that they not discuss it with people besides you.
You can also simply stop sharing such detail with them, without cutting them off completely unless you also choose to do that. If they are upset, I think it's reasonable to remind them that when you told them more they told other people, and that you'd rather talk about (any other topic). If they react aggressively, it may then make sense to get other people involved at your institution.
I'd also suggest having a conversation with your advisor(s). It doesn't need to be in any depth, and you don't need to set aside a separate meeting. Just mention that you've been talking about your research with a friend and you were surprised that they then conveyed it to third parties, and ask whether they think you should do anything about it. You don't have to accuse them or provide proof of plagiarism - you can just say what has happened and let others judge for themselves. They probably won't suggest there is much you can do, but now they'll be aware in the future.
Otherwise, keep moving forward and push towards publishing the things you have, like you would be doing anyways. If you have near-publishable work, consider discussing with your advisor whether it could be released as a pre-print. Whatever you have told this person about your progress so far, you have a huge head start on them, it's your research. Unless you think they'll actually be able to somehow beat you to publishing through their machinations, which doesn't seem likely from your description, they aren't too much of a threat.