chunk overlap

Chunk overlap prevents important context from being split at chunk boundaries. **Problem**: Fixed-size chunking can split sentences, paragraphs, or logical units, making retrieved chunks incomplete. **Solution**: Overlap consecutive chunks by N tokens, ensuring boundary content appears in at least one complete chunk. **Typical values**: 10-20% overlap (50-100 tokens for 500-token chunks). Too little: context splits remain; too much: redundancy and increased storage. **Example**: 400-token chunks with 50-token overlap → each boundary region covered in two chunks. **Trade-offs**: Increased storage (overlap creates redundancy), more chunks in index, potential for duplicate retrieval results. **Deduplication**: Remove near-duplicate chunks from retrieval results, or prefer higher-ranked version. **Alternatives to overlap**: Semantic chunking at natural boundaries, sliding window retrieval (compute on-the-fly), parent-child retrieval. **Best practices**: Match overlap to typical semantic unit sizes in your documents, monitor for retrieval duplicates, combine with sentence-aware splitting when possible. Simple but effective technique for improving RAG context quality.