As a reader of Simon's work, I can speculate an answer here.
All "designing agentic loops" is context engineering, but not all context engineering is designing agentic loops. He's specifically talking about instructing the model to run and iterate against an evaluation step. Sure, that instruction will end up in the context, but he's describing creating a context for a specific behavior that allows an agent to be more effective working on its own.
Of course, it'll be interesting to see if future models are taught to create their own agentic loops with evaluation steps/tests, much as models were taught to do their own chain of thought.
All "designing agentic loops" is context engineering, but not all context engineering is designing agentic loops. He's specifically talking about instructing the model to run and iterate against an evaluation step. Sure, that instruction will end up in the context, but he's describing creating a context for a specific behavior that allows an agent to be more effective working on its own.
Of course, it'll be interesting to see if future models are taught to create their own agentic loops with evaluation steps/tests, much as models were taught to do their own chain of thought.