The system prompt is a separate channel — role, rules, format and guardrails the model reads before the first user turn

Most people paste everything into one message: the persona, the rules, the format, and the actual question, all mashed together. But the model has two separate channels, and knowing the difference is the whole trick. The user turn is the question that changes every time; the system prompt is the standing instruction that persists across every turn. I built a live playground that assembles a system prompt from parts and shows the same question answered differently under it. Here's what I learned…