Here is the source code for a greenfield, zero-dependency, 100% pure PHP raw Git repository viewer made for self-hosted or shared environments that is 99.9% vibe-coded and has had ~10k hits and ~7k viewers of late, with 0 errors reported in the logs over the last 24 hours:
Did it really have to be zero-dependency...
I got back learning from books and use LLMs for "review my code in depth and show me its weak points" occasionally.
You can trace the back commits to the first to show that it was started from scratch:
https://repo.autonoma.ca/repo/treetrek/commits/c7742cb3c580d...
That's brownfield to me. Greenfield would develop a completely new system. This is a utility for an existing system, one whose design is clearly a copy of existing utilities. Both of those make this brownfield.