System prompt

A system prompt is the standing instruction a deployer gives a model before any user input: tone, role, what to refuse, what tools it may call. Users don't see it, but it shapes every response, and in enterprise assistants it often encodes business rules and internal context.

Two risks follow: system prompts can leak (models can be coaxed into revealing them, and they sometimes contain internal details that shouldn't be public), and they can be overridden (prompt injection is, at bottom, attacker text outranking the system prompt).