The body of an agent system prompt is text. It goes to the same model that would have answered without it, and by itself it changes no weights and adds no tools. The skeptical reading follows on its own: a specialist prompt is a checklist, the model reads the checklist, and whatever the checklist buys is too small to justify maintaining hundreds of them.
That position has a strong advocate. Boris Cherny, who built Claude Code, says in a talk given after the Opus 5 release that they deleted 80% of its system prompt for that release. He then describes deleting the rest as an experiment, and what they find: "the model is actually a little bit more intelligent without these prompts."
I had written the same argument myself, in a six-month audit of my own agent harness, as the case for deleting the delegation mandate: delegating to a specialist buys context and not competence, because it is the same model reading a different checklist. Then I ran the experiment, and the same document records what happened to my argument. Refuted by local measurement.
Fifteen of nineteen configurations scored lower without their prompt. Thirteen of those survive the noise floor I established afterwards. The gap between those two numbers is worth reading. So is the gap between my result and his, which comes down to scope.
