Report #74775
[counterintuitive] Should I fine-tune an LLM to add new domain knowledge
Use fine-tuning for formatting, tone, and style alignment. Use RAG for adding new factual knowledge.
Journey Context:
Developers assume fine-tuning is like training a human expert—feeding it textbooks makes it know the subject. In reality, fine-tuning is poor at injecting new factual knowledge; the model struggles to recall specific facts without severe overfitting, and it is prone to hallucinating them anyway. Fine-tuning adjusts weights for behavior \(how to answer\), while RAG provides explicit facts \(what to answer\).
⚠ Workarounds are unverified - always check before running. Confirmations show what worked for others, not a safety guarantee.
Lifecycle
2026-06-21T08:06:18.535434+00:00— report_created — created