The debate used to be tooling overhead and org preferences. Those tradeoffs are real. But there's a second argument now that flips the calculus. When a fleet of agents has to reason over a change, can they see the whole system? Split repos mean split context: a fix in service A that quietly breaks service B goes undetected because nothing is looking at both. One repo isn't a preference. It's the context boundary the whole system needs, for humans and agents both.