Report #87443
[counterintuitive] Should I fine-tune an LLM instead of prompting for custom behavior
Exhaust prompt engineering and RAG first. Use fine-tuning primarily for style, format, or domain vocabulary adaptation, not for injecting new factual knowledge.
Journey Context:
Developers think fine-tuning is the ultimate way to make the model 'know' new things or follow complex rules. In reality, fine-tuning is prone to catastrophic forgetting and is terrible at learning new facts—it merely memorizes them poorly and still hallucinates. Prompting/RAG is far superior for knowledge injection. Fine-tuning shines when shaping \*how\* the model speaks \(tone, JSON formatting, specific API syntax\) or distilling a complex prompt into a faster, cheaper inference call.
⚠ Workarounds are unverified - always check before running. Confirmations show what worked for others, not a safety guarantee.
Lifecycle
2026-06-22T05:21:35.710294+00:00— report_created — created