I've found MCP is great for stacking claude code instances- https://github.com/cduerr/stewardmcp has legit been a useful tool for me, and more reliable than handing a single instance 100k lines of code over a dozen repos.
Isn't that handled pretty well these days with sub agents? They can research the code without polluting the context.
Somewhat. The stewards (sub-Claudes) won't share their parents context window and have the ability to talk to one another. That said I'm sure there's a lot out there that solves for this.