When does wiring models together actually help?

A single model is one agent in a loop. A mix wires several over one workspace - a planner, an implementer, a critic, a judge. lemon-squeezer runs the first four of these as scored harnesses on the same evals as everything else; the fifth, Swarm, is shown for shape (it is how this very page was built, not a benchmark arm). Below: how each is wired, and what it buys.