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The Internet Compass

AI

System Prompt

A system prompt is a set of instructions provided to a language model, separate from the user's own messages, that establishes its role, tone, constraints and behaviour for the remainder of a conversation — typically set by the application developer rather than the end user.

System prompts are how the same underlying model becomes a customer-support bot in one product and a coding assistant in another: the model's core capabilities don't change, but the system prompt narrows its behaviour, gives it context about the product it's embedded in, and sets rules for what it should refuse to do.

Well-designed system prompts are typically layered with the conversation itself: general behavioural rules set once, plus dynamically injected context (retrieved documents, user data, available tools) added per conversation — treating the system prompt as a single static block of text tends to produce brittle results as an application's needs grow.