Export documents (async)

Submit an async export of a bank's documents (extracted facts, entity names, causal links, chunks) as a transfer ZIP archive. Embeddings and database ids are not included — importing re-embeds with the target bank's model and re-resolves entities. Runs as a background operation to avoid pinning the API on large banks. Returns an operation_id; poll GET /v1/default/banks/{bank_id}/operations/{operation_id}. On completion the operation's result_metadata carries download_url (fetch the ZIP from GET /v1/default/files/download/{key}), storage_key, byte_size, and filename. Pass document_id query params to export specific documents, or omit to export the whole bank; include_observations=true carries consolidated observations and include_knowledge_base=true carries Mental Models plus Knowledge Pages (all whole-bank export only).