Lessons from building AI coding assistants: Context retrieval and evaluation

Context retrieval is a pivotal component in transforming large language models (LLMs) into effective AI coding assistants by enabling them to provide responses grounded in a specific codebase. This process involves the context engine, which retrieves and ranks relevant snippets of code or text to enrich an LLM's understanding, allowing it to deliver precise, context-aware answers. The context engine functions through a two-stage process of retrieval and ranking, utilizing diverse techniques such as keyword searches, code embeddings, and graph-based analysis to gather potential context items from various sources like code repositories and documentation. The ranking stage then refines this selection to ensure that only the most pertinent information fits within the token budget constraints, ultimately enhancing the LLM's response quality. Evaluating this system poses challenges due to the lack of ground truth data and the complexity of user interactions, but overcoming these hurdles is crucial for developing AI tools that can significantly boost developer productivity by offering tailored, accurate assistance.