System Prompt
Also called: system message
Standing instructions that set a model's role, rules, and tone for an entire conversation.
The system prompt sits above the user turn and persists across the session, defining who the assistant is and what it must and must not do. It is where product teams put voice, scope, and refusal rules. It is influential but not a security boundary — treat it as configuration, not as a control users cannot reach.
In practice: ‘You are a support agent for an EU fintech. Never give financial advice. Reply in under 120 words.’
Where this comes up
- ChatGPT Context Window: What It Is and What Actually Fits
- ChatGPT Help Tips and Tricks in 2026: How to Make ChatGPT More Effective
- Claude Code Subagents: What They Do and When to Use Them
- Claude Context Window: Size, What Counts Toward It, and How to Manage It
- Claude Memory: How It Works, How to Manage It, and When to Avoid It
- How to Set Up ChatGPT Locally for Work in 2026