Definition
System prompt
Instructions passed to an AI model before the user's message, typically used to define the model's persona, constraints, and task context. System prompts are often treated as authoritative, but they are not a security boundary — prompt injection can cause the model to override or ignore system prompt instructions. OWASP and Microsoft's security guidance both emphasize that security-critical constraints must be enforced in deterministic code, not in system prompt text.
Related terms
Prompt injection
A class of attack where malicious input alters an AI model's behavior in ways the system designer di…
Operator controls
Deterministic controls implemented in code — outside the AI model — that govern what an agent is per…
Trust boundary
A point in a system architecture where trust assumptions change — where data or control moves from a…
Deep dive
Basic knowledgeWhat is prompt injection?
Prompt injection is not just a clever string. It is any input that changes a model's behavior in a way the system designer did not intend, especially when the model can reach tools, data, and accounts.
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