A system prompt is the standing instruction set an application gives a model before any user input: role, rules, tone, capabilities, constraints, and guardrails
The standing instruction set an application gives a model before any user input: role, rules, tone, capabilities, constraints, and guardrails. It frames every response and is the primary behavioral control surface developers own.
They must be treated as production artifacts, versioned, tested against evals, and security-reviewed, because prompt-injection attacks specifically try to override them. Secrets should never be placed in a system prompt, since attacks can coax models into revealing it.