If you use LLMs long enough, you hit the same wall. The frontier model is impressive, but it is not always the best model for your job. It may be too expensive. It may be too slow. It may be too general. And once you start asking it to follow your company’s rules, tone, domain language, and task structure, the gap between “smart” and “useful” gets obvious fast. That is where post-training comes in. The short version is this: if you have enough good data, you can often take an open-source model a