post-training

Definition

Everything done to a pretrained model to make it usable: supervised fine-tuning on demonstrations, preference-based reinforcement learning such as RLHF or DPO, safety training, and increasingly reasoning-focused training. Pre-training installs knowledge and general competence; post-training decides how that competence is expressed — format, refusal behavior, instruction following, willingness to reason at length. Among models of comparable scale, most of the visible quality difference now originates here.

Explainers using this term

• Paper Walkthrough: From Production Traffic to Post-Training — Folding 200 Internal Apps Into One Self-Hosted LLMFrom Production Traffic to Post-Training: Building a Self-Hosted LLM That Covers the Corporate Request Mix