I fixed my 10 year-old webapp yesterday. There were only a couple of easy-to-fix issues. I could've fixed them without AI but AI does help speed things up.

The problem is when looking at it 10 years later I want to rebuild it from scratch because the code and build system look so different than what we do now. I'm not sure yet if it will take a long time though, at least if I accept to keep jquery and avoid typescripting everything.