Honestly, if I could quit my job for six months and work in a codebase like yours, I'm extremely curious what I could accomplish with AI.

We have a codebase at work that was "stuck." We've consistently done minor library upgrades, but no major upgrades in several years, and was recognized as a major piece of technical debt / minor disaster for almost two years, in that we urgently needed to dedicate an engineer to it for a month or more to bring it up to date. We also suspected that framework upgrades would improve performance enough to save us a little bit in operating costs. I got curious, created a branch, and threw Claude at it. Claude knocked it out in a couple of days while I mostly worked on other things. Then we dedicated several engineer days to doing extra manual testing. Done and deployed. Now we're ready to experiment with giving it less resources to see if the performance improvement holds up in practice.

This codebase was only about 200k lines of code, so probably smaller than yours. Really curious how it would go with a larger codebase.

EDIT: Claude may only have taken a couple of days because I was only checking in occasionally to give it further instructions. I don't know how fast it would have been with my complete attention.