Ask HN: What to do when your pet project is also a clients?

[meester]

So, I started work for a development firm yesterday, and came to find that one of the clients that has approached them wants to build something that's very much like what I'm working on, on the side.

Obviously, I don't want to expose myself to risk of litigation or anything, but It's not clear what to do here. I haven't gleamed any of the actual confidential stuff yet in hopes that shields me somehow...

While it's not the exact same thing, there is definitely overlap... enough to make me uncomfortable.

The firm said they'll ask the lawyer once they land the contract, but I just wanted to ask the community if there's something I should do, like run for the hills; or if there's some legal document that can absolve me of risk in my involvement.