langchain¶

--format auto detects the layout. Verified with stores built by real langchain_community FAISS and langchain_core.

• faiss: a FAISS.save_local folder (index.faiss + index.pkl, --index-name). Vectors are reconstructed from FAISS (IVF needs a direct map; quantized indexes return their lossy reconstruction). index.pkl is a pickle: it is read with an allow-list unpickler that maps only LangChain's Document and InMemoryDocstore classes to inert stand-ins, so a hostile pickle cannot run code (tested) and LangChain need not be installed. Document ids come from the docstore mapping.
• inmemory: InMemoryVectorStore.dump JSON (current {id: item} and older {"store": ...} layouts).
• jsonl: one Document per line, either dumpd form or {"page_content", "metadata", "id"}.
• filestore: a LocalFileStore / create_kv_docstore directory (file name = id, content = serialized Document; no vectors).

Document metadata is preserved flat. LangChain stores no timestamps, so none are invented. Text-only layouts need an encoder.