Last updated: 2026-04-18
What is Fine-tuning?
Continuing the training of a base LLM on your own labeled examples to specialize its behavior — different from prompt engineering (changing instructions) or RAG (providing context at inference time). Useful when you need a specific tone, format, or domain vocabulary the base model can't reliably hit via prompting alone. Available through the OpenAI API and some open-weight models; not available in ChatGPT or Claude Cowork. Costs 100×-1000× a regular inference call but is a one-time cost.
See also
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