My contracts either stipulated set work hours or was contract work for which I billed for the hours. If the project is completed outside of the stipulated work

My contracts either stipulated set work hours or was contract work for which I billed for the hours. If the project is completed outside of the stipulated work hours or not billed for and not using company resources such as computers, then they have no claim to it. If I’m meeting my contactual obligations, anything more is mine. If I go above and beyond, then that is, essentially, a gift from me to the company, because I’m only compensated for what the contract says I’m compensated for. If I spend my leisure time to build something that makes my job easier, I see that akin to using the time to go to the gym or get more sleep because that also makes my job easier. If it’s my leisure time, what I do is my business even if it helps my work. Of course we don’t know when this person built the tool and maybe it was done in a less clear way. I always try to keep things I do for myself clearly separate. Eg if I’m WFH and the last hour is quiet maybe I’ll also put some food on while I finish work, but I would never use that time to work on a personal project but rather wait until I’m clearly clocked out.