I think datasette-transactions https://github.com/datasette/datasette-transactions is pretty novel. Here's the transcript where Claude Code built it: https://gisthost.github.io/?a41ce6304367e2ced59cd237c576b817...

That transcript viewer itself is a pretty fun novel piece of software, see https://github.com/simonw/claude-code-transcripts

Denobox https://github.com/simonw/denobox is another recent agent project which I consider novel: https://orphanhost.github.io/?simonw/denobox/transcripts/ses...