Fine-Tuning Isn’t Just Supervised: Why SFT Is Really RL in Disguise
In the arms race to align large language models (LLMs), supervised fine-tuning (SFT) and reinforcement learning (RL) are often painted as competing paradigms. SFT is praised for its stability and simplicity; RL is heralded for its theoretical soundness and alignment fidelity. But what if this dichotomy is an illusion? A recent preprint from Chongli Qin and Jost Tobias Springenberg makes a bold and elegant claim: SFT on curated data is not merely supervised learning—it is actually optimizing a lower bound on the RL objective. ...