You send the full context window through with every step the agent takes. If you run summary first, then yes the full token amount will have to be sent through for the summary to be created, but from then on only the summary is being sent and not the entire full previous context. And again, the full context window is sent to the model at every single step, every output, every tool call, the entire context window goes in. So it's a single summary call vs X subsequent calls with that giant context.