I've found myself occasionally wishing I had a monorepo purely for Claude Code for web (Anthropic's hosted version of Claude Code), since it can currently only work with one private repository at a time.
On my own machine I have a dev/ folder full of checkouts of other repos, and I'll often run Claude Code or Codex CLI in that top level folder and tell it to make changes to multiple projects at once. That works just fine.
The "dev/" folder concept is what I give my agent, so I can select what I want it to have access to. On my computer, I have a few of those to group those that go together.
Couldn’t you make a pseudo monorepo via git submodules?