I've published a sample project that is medium sized, about 20k lines encompassing a game client, game server, and background service: https://github.com/kirodotdev/spirit-of-kiro This has been all developed by Kiro. The way Kiro is able to work in these larger projects is thanks to steering files like these:

- Structure, helps Kiro navigate the large project: https://github.com/kirodotdev/spirit-of-kiro/blob/main/.kiro...

- Tech, helps Kiro stay consistent with the tech it uses in a large project: https://github.com/kirodotdev/spirit-of-kiro/blob/main/.kiro...

And yes, the specs do help a lot. They help Kiro spend more time gathering context before getting to work, which helps the new features integrate into the existing codebase better, with less duplication, and more accuracy.