Pretraining is the large-scale phase that produces a base model with broad knowledge and capabilities through next-token prediction. Its output establishes most of the potential later cultivated by post-training. section 1.4
Next-token prediction does not automatically yield useful conversation. Post-training reshapes that behavior toward question-answering and attempts to expose capabilities that pretraining makes available but does not directly express. section 1.4
Pretraining establishes the starting point for later optimization:
- Produces a static base model whose knowledge and capabilities constrain the final model’s potential. section 1.4
- Leaves substantial performance gains to mid-training, high-quality end-of-pretraining data, instruction tuning, RLVR, and preference tuning. section 1.4
OLMoE comparison
OLMoE Instruct’s second version changed little in pretraining but improved its popular-benchmark average from 35 to 48 through post-training, illustrating the distinction between creating capability and eliciting it. section 1.4













