I want to build in public but i'm concerned about idea theft

"Pour yourself into your product and everything around your product too: how you sell it, how you support it, how you explain it, and how you deliver it. Competitors can never copy the you in your product."

— Jason Fried and David Heinemeier Hansson, “Rework”

I don't know the answer to your question, but I think people are likely to copy it either way if there's something real there.

Ideas are cheap. You can only make money and gain traction when you execute it, grow it and scale to a point where you will be proud of. Scary? Don't start then, let your idea sits forever.

Give it a code name i.e. project x and talk about it in general terms

You'll never be able to keep your idea a secret forever, unless you never bring it to market. You should embrace competition and look at it from the positive side. If other people copy your idea, the market can potentially grow and you can differentiate yourself accordingly. Competition is part of growing.

Good luck

Just build a great product and don't worry about idea theft, if you do it right, it doesn't matter if 1000 people steal it, and I'm sure there is competition but you just did not do your research right so just go for it, you'll be happy with the results.

It’s pretty rare not to have competition, so if you did your research right, kudos to you! I think execution makes all the difference. If it is easy to copy and worth it, other people will do it anyway eventually. I’d suggest to focus on building a great product and try to deliver to your niche before others.