# Developer Message

> A higher-priority instruction from the application that sets rules, tone, business logic, or boundaries for the model.

- Category: Context & Memory
- Stage: Rising
- Also called: System prompt, System message, Instruction message
- Canonical: https://www.joelcsaji.com/ai-dictionary/developer-message

## Plain English

It is the app's private rule sheet for how the AI should behave before the user asks anything.

## Example

A finance assistant's developer message says to cite policy documents and never move money without approval.

## Why it matters

Separating app instructions from user requests is central to safer prompt design and prompt-injection defense.

## Related

- [Prompt](https://www.joelcsaji.com/ai-dictionary/prompt)
- [Prompt Injection](https://www.joelcsaji.com/ai-dictionary/prompt-injection)
- [Guardrails](https://www.joelcsaji.com/ai-dictionary/guardrails)

## Sources

- [OpenAI: Text Generation](https://platform.openai.com/docs/guides/text-generation)