A hidden instruction that sets the AI’s role and rules before the chat starts.
It is like a note taped behind the stage. The actors cannot see it. But it tells them how to act.
It keeps the AI’s tone and limits steady. You often meet it in assistants, customer support, and Agents.
Prompt
The System prompt sets the model’s role and rules before the user Prompt.
Prompt injection
Prompt injection often tries to trick the model into breaking the System prompt.
Agent
The System prompt often sets an Agent’s behavior limits and style.
Alignment
Some Alignment rules are put into practice through the System prompt.