Что такое System Prompt?

The system prompt is the LLM's 'job description.' It typically describes who the assistant is (a customer support agent for X), how it should behave (concise, helpful, escalate if unsure), what it should NOT do (don't make medical claims, don't go off-topic), and what tools it has. The system prompt is shown to the model before any user message and (in most modern models) carries higher priority than user instructions. Users can't override it via clever phrasing — though prompt injection attacks remain a real risk in 2026. Well-designed system prompts are the difference between a chatbot that solves problems and one that hallucinates wildly. Big companies write 1000-line system prompts; most apps can do well with 50-100 lines.