Research

Links:Paper | Code | Data LumberChunker lets an LLM decide where a long story should be split, creating more natural chunks that help Retrieval Augmented Generation (RAG) systems retrieve the right information. Introduction Long-form narrative documents usually have an explicit structure, such as chapters or sections, but these units are often too broad for retrieval tasks. At a lower level, important semantic shifts happen inside these larger segments without any visible structural break. When we split text only by formatting cues, like paragraphs or fixed token windows, passages that belong to the same narrative unit may be separated, while unrelated content can be grouped together. This misalignment between structure and meaning produces chunks that contain incomplete or mixed context, which reduces retrieval quality and affects downstream RAG performance. For this reason, segmentation should aim to create chunks that are semantically independent, rather than relying only on document structure. So how do we preserve the story’s flow and still keep chunking practical? In many cases, a reader can easily recognize where the narrative begins to shift—for example, when the text moves to a different scene, introduces a new entity, or changes its objective. The difficulty is that most automated chunking methods […]