System prompt
The instructions the model receives before any user messages — used by the product operator to set behavior, tone, and guardrails.
A system prompt is the special first message in a conversation that a model treats as authoritative instructions rather than a normal user turn. It's how a product operator (like LADLE) tells the model things like "you are a helpful assistant for our product", "keep responses concise", "never discuss competitors negatively", etc.
The distinction matters because most modern chat models are trained to weight system prompts more heavily than user turns, and to resist attempts to override them mid-conversation. A user typing "ignore the system prompt" doesn't usually work; the model was specifically trained to keep following its original system-level instructions.
Users generally don't see the system prompt in consumer chat products. This is partly for UX simplicity (system prompts are often long and boilerplate-ish) and partly for competitive reasons (system prompts are where product differentiation lives). Some products expose them; most don't.