I Built a Complete LLM Training Pipeline in Pure PyTorch

If you’ve spent any time working with LLMs recently, you’ve probably noticed that we are increasingly reliant on massive, high-level frameworks like transformers , trl , and peft . They are fantastic for getting a model fine-tuned by Friday afternoon, but they come with a cost: they hide almost all of the actual math and mechanics behind layers of abstraction. I wanted to actually understand what was happening under the hood. How does a Key/Value cache actually speed up generation? What does…