Agent runtime

System Prompt

The standing instructions a model receives before any user input — identity, scope, rules, and refusal behavior — the closest thing an AI system has to a job description.

Operating principle

Production AI is a system: context, tools, permissions, traces, evals, and feedback loops around the model.

What it is

The system prompt is the text the operator controls: who the assistant is, what it may and may not do, how it should answer, when it should decline or escalate. The user's message arrives after it and is interpreted in its light.

Why it matters

Most behavior people attribute to 'the model' is actually the system prompt. Two products on the same model feel different because their standing instructions differ. It is also a governed artifact: a wording change can shift refusal behavior, tone, or tool usage across every conversation at once.

How we manage it

System prompts are versioned files in a repository, not strings buried in code. Changes ship through the same gate as model changes: run the eval set, compare against production, promote only when the numbers pass. The persona layer of the prompt is tested separately for stability under adversarial pressure.

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