Scaling with Collapse: Efficient and Predictable Training of LLM Families

Abstract: Effective LLM training relies on consistency, meaning that key quantities -- such as final losses and optimal hyperparameters -- scale predictably across model sizes. Qiu et al. (2025) recently showed that this consistency extends beyond scalars: whole training loss curves can collapse onto a universal trajectory after a simple normalization. What remains unclear is whether this phenomenon holds for LLM families trained under practical scaling recipes, where width, depth, learning rate, batch size, and weight decay are scaled jointly. We show that it does: loss curves collapse across scales precisely when optimization hyperparameters are set optimally for the given data budget, in accordance with recent empirical scaling laws. Collapse thus emerges as a signature of compute-efficient training. We demonstrate two applications at scale: (1) deviation-from-collapse provides a sensitive, early diagnostic of training pathologies, and (2) the predictability of collapsed curves enables early stopping in large-scale hyperparameter tuning. Finally, we train a competitive LLM family, Celerity, using these insights, highlighting collapse as an effective tool for developing efficient LLMs.