We just recently use Claude Code to port an old Coldfusion site to Java Spring and it went amazingly well. It's around 50K lines of Java, one of our engineers did it in his spare time over about a week, using the $200/mo Claude plan. We had been talking about doing it for at least the last dozen years but never found the time. It would have taken around 12-18 engineer-months to do this manually.
He had the translation use browser integration to compare the new site to the old site automatically. The result was so good that he had to change background color on the new site because he couldn't be sure that he was testing the new site; it was so close to the original he was paranoid about accidentally being on the old site and not knowing it. The whole thing was done in under 2 weeks, including coding, developer testing, tester testing, and deployment. It's been in production 4-6 weeks now and we've had no reports of problems.
He had the translation use browser integration to compare the new site to the old site automatically. The result was so good that he had to change background color on the new site because he couldn't be sure that he was testing the new site; it was so close to the original he was paranoid about accidentally being on the old site and not knowing it. The whole thing was done in under 2 weeks, including coding, developer testing, tester testing, and deployment. It's been in production 4-6 weeks now and we've had no reports of problems.