Context retrieval for LLM prompts

The model only knows what you put in front of it. Everything Cursor does well starts with one quiet, brutal engineering problem: which bytes of a million-line repo go into a few-thousand-token window.

An interviewer who works on the editor will probe this fast, because it's the unglamorous core of the product. A completion that ignores the helper you wrote two files over feels broken even when the model is fine. The model wasn't wrong, it was blind. Context retrieval is the part of the system that decides what it gets to see.

Frame the prompt as a budget you spend deliberately. You have a fixed token window, you want to fill it with the snippets most likely to make the next edit correct and you have milliseconds to decide.