# Fine-tune vs. RAG vs. prompt

Knowledge changes often → RAG. Behavior/format/tone must change → fine-tune. Neither → a better system prompt with examples (cheapest, try first). Most companies that think they need fine-tuning need retrieval and better prompts.

Canonical: https://robauto.ai/learn/ai-architecture/9

_Advanced AI Architecture: Strategy, Stack & Daily Practice — lesson 9 of 20 (PLAYBOOK)_

Knowledge changes often → RAG. Behavior/format/tone must change → fine-tune. Neither → a better system prompt with examples (cheapest, try first). Most companies that think they need fine-tuning need retrieval and better prompts.

Source: [OpenAI — Optimizing LLM accuracy](https://platform.openai.com/docs/guides/optimizing-llm-accuracy?utm_source=robauto)

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