Why is a 'system' Message Essential in OpenAI Chat Completions API When User Messages Can Set Behavior?

Explanation:

• Higher Priority:
  The system role is designed to establish foundational instructions that the assistant follows throughout the conversation. These instructions are given the highest priority and are not easily overridden by subsequent messages—even if a user message attempts to modify behavior.

• Consistency and Stability:
  By having a dedicated system message for behavior directives, the assistant’s personality, tone, and operational guidelines remain consistent, regardless of fluctuating user inputs. This ensures that core policies and behavior guidelines remain intact throughout the interaction.

• Pre-Configuration:
  The system message can be seen as the "pre-configuration" step that sets up the context, style, or constraints under which the assistant should operate. The user's message, in contrast, is part of the dynamic conversation and doesn’t have the same overriding authority.

In summary, while a user message can influence behavior to some extent, the system message is crucial because it provides a stable, always-applied set of instructions that ensure the assistant behaves in accordance with its designed objectives and policies.