Instructions you do not see.
THE DEFINITION
Text the operator provides to shape a model's behaviour: its tone, restrictions and purpose.
WHERE IT SITS
Before your messages, in every exchange.
You generally do not see it.
WHAT IT DOES
Sets how the assistant behaves States what it should and should not do Provides context about its role
WHY IT MATTERS TO YOU
Two products using the same underlying model can behave very differently because of it.
FOR BUILDERS
Treat system prompts as code: versioned, tested, reviewed.
Changing one changes behaviour, and undocumented changes cause confusion.
THE COST POINT
A lengthy system prompt is sent with every request and costs on every request.
At volume, that dominates.
RELATED TERMS
Prompt, alignment, API.
