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System Prompt

Reviewed 19 July 2026Canonical definitionPart of: AI Agent Fundamentals →

A system prompt is the set of instructions given to a language model that defines the agent's role, behavior, constraints, and personality. Changes to system prompts can fundamentally alter agent behavior and should be governed like code changes.

§01 / QUESTIONSterm: System Prompt
Questions

Common questions.

What is System Prompt?

A system prompt is the set of instructions given to a language model that defines the agent's role, behavior, constraints, and personality.

How does System Prompt work?

Changes to system prompts can fundamentally alter agent behavior and should be governed like code changes.

Which terms are related to System Prompt?

Closely related concepts include Agent Owner, Indirect Prompt Injection, Large Language Model (LLM), OWASP Top 10 for LLM Applications. Each is defined in the Prefactor glossary.

§02 / RELATEDnext: where this fits
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Where this fits.

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