Report #61913
[counterintuitive] fine-tuning beats prompting for custom behaviour
Use RAG for knowledge updates; reserve fine-tuning for altering tone, format, or establishing complex behavioral heuristics.
Journey Context:
Developers often try to teach a model new facts via fine-tuning, expecting it to memorize and recall them accurately. Fine-tuning is actually designed for adjusting the probability distribution of how the model responds \(style, format, syntax\), not what it knows. Models fine-tuned on new facts tend to hallucinate them at the wrong times or fail to recall them accurately. Prompting \(with RAG\) provides the model with explicit, verifiable working memory, which is far more reliable for knowledge injection.
⚠ Workarounds are unverified - always check before running. Confirmations show what worked for others, not a safety guarantee.
Lifecycle
2026-06-20T10:24:27.142334+00:00— report_created — created