I'd move against him, and quickly. Tell the CEO you need unity not divisiveness. You are all for working with the new CTO but he is trying to force you out of t

I'd move against him, and quickly. Tell the CEO you need unity not divisiveness. You are all for working with the new CTO but he is trying to force you out of the company you founded. There is only one way to deal with people like this: decisively. The fact that you've come here to ask for opinions on this matter suggests that you may lack the inner confidence to survive in a startup. Take this as a learning opportunity. Bone up on your technical skills, hire people smarter than you. Realize that you've been identified as a less than top-tier software developer and use that information to help you figure out where your skills can best help the company succeed. Good luck, move now and go for the jugular.