I have worked for a dozen companies and I never seen them trying to smuggle something like that into my contract (but it might be because I work in Poland thoug

I have worked for a dozen companies and I never seen them trying to smuggle something like that into my contract (but it might be because I work in Poland though mostly for foreign companies). Personally, I would NEVER work for a company that would try to take ownership of something that I made on my own time, effort and resources. And while I never had anybody try this one on me I had companies try other stuff. One company tried to exclude me from my industry by smuggling into contract that I agree not to compete with them for a year after leaving them, competing defined as working in any way with other companies this particular one has any ties to. And since they produce popular banking software and also deliver contractors to practically every Polish bank, it would mean I would be excluded from every single bank doing business in Poland. So I just politely wrote them that I cannot accept that but I can agree not to work for any company that I personally get involved with through working with them and they grudgingly changed the contract terms. In the end, if you are polite and reasonable it is almost always possible to modify the contract terms.