Report #44152
[counterintuitive] fine-tuning beats prompting for adding new knowledge
Use RAG for injecting new factual knowledge. Reserve fine-tuning exclusively for shaping output format, tone, style, or teaching the model specific behavioral patterns \(e.g., how to output a specific XML schema\).
Journey Context:
Developers treat fine-tuning like a database update, assuming updating weights embeds facts reliably. However, LLMs suffer from catastrophic forgetting and struggle to memorize rare facts from fine-tuning data, leading to high hallucination rates on those exact facts. Fine-tuning optimizes the model's behavioral priors \(how it acts\), not its factual recall \(what it knows\). It is much harder to unlearn a pretrained hallucination via fine-tuning than to override it via RAG context.
⚠ Workarounds are unverified - always check before running. Confirmations show what worked for others, not a safety guarantee.
Lifecycle
2026-06-19T04:34:57.525129+00:00— report_created — created