Merge branch 'main' into dynamic-add

.gitignore

@@ -101,3 +101,4 @@ CLAUDE.local.md
 .claude/*.local.*
 .claude/local/*
 benchmarks/data/
+test_add/*

examples/dynamic_add_leann_no_recompute.py

@@ -0,0 +1,380 @@
+"""
+Dynamic add example for LEANN using HNSW backend without recompute.
+
+- Builds a base index from a directory of documents
+- Incrementally adds new documents without recomputing stored embeddings
+
+Defaults:
+- Base data: /Users/yichuan/Desktop/code/LEANN/leann/data
+- Incremental data: /Users/yichuan/Desktop/code/LEANN/leann/test_add
+- Index path: <index_dir>/documents.leann
+
+Usage examples:
+  uv run python examples/dynamic_add_leann_no_recompute.py --build-base \
+    --base-dir /Users/yichuan/Desktop/code/LEANN/leann/data \
+    --index-dir ./test_doc_files
+
+  uv run python examples/dynamic_add_leann_no_recompute.py --add-incremental \
+    --add-dir /Users/yichuan/Desktop/code/LEANN/leann/test_add \
+    --index-dir ./test_doc_files
+
+Quick recompute test (both true):
+  # Recompute build
+  uv run python examples/dynamic_add_leann_no_recompute.py --build-base \
+    --recompute-build --ef-construction 200 \
+    --base-dir /Users/yichuan/Desktop/code/LEANN/leann/data \
+    --index-dir ./test_doc_files --index-name documents.leann
+
+  # Recompute add
+  uv run python examples/dynamic_add_leann_no_recompute.py --add-incremental \
+    --recompute-add --ef-construction 32 \
+    --add-dir /Users/yichuan/Desktop/code/LEANN/leann/test_add \
+    --index-dir ./test_doc_files --index-name documents.leann
+"""
+
+import argparse
+import json
+import pickle
+import sys
+from pathlib import Path
+from typing import Any, Optional
+
+# Ensure we can import from the local packages and apps folders
+ROOT = Path(__file__).resolve().parents[1]
+CORE_SRC = ROOT / "packages" / "leann-core" / "src"
+HNSW_PKG_DIR = ROOT / "packages" / "leann-backend-hnsw"
+APPS_DIR = ROOT / "apps"
+
+
+# Prefer the installed backend if available (it contains the compiled extension)
+def _prefer_installed(pkg_name: str) -> bool:
+    try:
+        import importlib
+        import importlib.util
+
+        spec = importlib.util.find_spec(pkg_name)
+        if spec and spec.origin and "site-packages" in spec.origin:
+            # ensure the faiss shim/extension is importable from the installed package
+            importlib.import_module(f"{pkg_name}.faiss")
+            return True
+    except Exception:
+        pass
+    return False
+
+
+# Prepend paths, but only add the repo backend if the installed one is not present
+paths_to_prepend = [CORE_SRC, APPS_DIR]
+if not _prefer_installed("leann_backend_hnsw"):
+    paths_to_prepend.insert(1, HNSW_PKG_DIR)
+
+for p in paths_to_prepend:
+    p_str = str(p)
+    if p_str not in sys.path:
+        sys.path.insert(0, p_str)
+
+# Defer non-stdlib imports until after sys.path setup within functions (avoid E402)
+
+
+def _load_documents(data_dir: str, required_exts: Optional[list[str]] = None) -> list[Any]:
+    from llama_index.core import SimpleDirectoryReader  # type: ignore
+
+    reader_kwargs: dict[str, Any] = {"recursive": True, "encoding": "utf-8"}
+    if required_exts:
+        reader_kwargs["required_exts"] = required_exts
+    documents = SimpleDirectoryReader(data_dir, **reader_kwargs).load_data(show_progress=True)
+    return documents
+
+
+def _ensure_index_dir(index_dir: Path) -> None:
+    index_dir.mkdir(parents=True, exist_ok=True)
+
+
+def _index_files(index_path: Path) -> tuple[Path, Path, Path]:
+    """Return (passages.jsonl, passages.idx, index.index) paths for a given index base path.
+
+    Note: HNSWBackend writes the FAISS index using the stem (without .leann),
+    i.e., for base 'documents.leann' the file is 'documents.index'. We prefer the
+    existing file among candidates.
+    """
+    passages_file = index_path.parent / f"{index_path.name}.passages.jsonl"
+    offsets_file = index_path.parent / f"{index_path.name}.passages.idx"
+    candidate_name_index = index_path.parent / f"{index_path.name}.index"
+    candidate_stem_index = index_path.parent / f"{index_path.stem}.index"
+    index_file = candidate_stem_index if candidate_stem_index.exists() else candidate_name_index
+    return passages_file, offsets_file, index_file
+
+
+def _read_meta(index_path: Path) -> dict[str, Any]:
+    meta_path = index_path.parent / f"{index_path.name}.meta.json"
+    if not meta_path.exists():
+        raise FileNotFoundError(f"Metadata file not found: {meta_path}")
+    with open(meta_path, encoding="utf-8") as f:
+        return json.load(f)
+
+
+def _autodetect_index_base(index_dir: Path) -> Optional[Path]:
+    """If exactly one *.leann.meta.json exists, return its base path (without .meta.json)."""
+    candidates = list(index_dir.glob("*.leann.meta.json"))
+    if len(candidates) == 1:
+        meta = candidates[0]
+        base = meta.with_suffix("")  # remove .json
+        base = base.with_suffix("")  # remove .meta
+        return base
+    return None
+
+
+def _load_offset_map(offsets_file: Path) -> dict[str, int]:
+    if not offsets_file.exists():
+        return {}
+    with open(offsets_file, "rb") as f:
+        return pickle.load(f)
+
+
+def _next_numeric_id(existing_ids: list[str]) -> int:
+    numeric_ids = [int(x) for x in existing_ids if x.isdigit()]
+    if not numeric_ids:
+        return 0
+    return max(numeric_ids) + 1
+
+
+def build_base_index(
+    base_dir: str,
+    index_dir: str,
+    index_name: str,
+    embedding_model: str,
+    embedding_mode: str,
+    chunk_size: int,
+    chunk_overlap: int,
+    file_types: Optional[list[str]] = None,
+    max_items: int = -1,
+    ef_construction: Optional[int] = None,
+    recompute_build: bool = False,
+) -> str:
+    print(f"Building base index from: {base_dir}")
+    documents = _load_documents(base_dir, required_exts=file_types)
+    if not documents:
+        raise ValueError(f"No documents found in base_dir: {base_dir}")
+
+    from chunking import create_text_chunks
+
+    texts = create_text_chunks(
+        documents,
+        chunk_size=chunk_size,
+        chunk_overlap=chunk_overlap,
+        use_ast_chunking=False,
+    )
+    if max_items > 0 and len(texts) > max_items:
+        texts = texts[:max_items]
+        print(f"Limiting to {max_items} chunks")
+
+    index_dir_path = Path(index_dir)
+    _ensure_index_dir(index_dir_path)
+    index_path = index_dir_path / index_name
+
+    print("Creating HNSW index (non-compact)...")
+    from leann.api import LeannBuilder
+    from leann.registry import register_project_directory
+
+    builder = LeannBuilder(
+        backend_name="hnsw",
+        embedding_model=embedding_model,
+        embedding_mode=embedding_mode,
+        is_recompute=recompute_build,
+        is_compact=False,
+        efConstruction=(ef_construction if ef_construction is not None else 200),
+    )
+    for t in texts:
+        builder.add_text(t)
+    builder.build_index(str(index_path))
+
+    # Register for discovery
+    register_project_directory(Path.cwd())
+
+    print(f"Base index built at: {index_path}")
+    return str(index_path)
+
+
+def add_incremental(
+    add_dir: str,
+    index_dir: str,
+    index_name: Optional[str] = None,
+    embedding_model: Optional[str] = None,
+    embedding_mode: Optional[str] = None,
+    chunk_size: int = 256,
+    chunk_overlap: int = 128,
+    file_types: Optional[list[str]] = None,
+    max_items: int = -1,
+    ef_construction: Optional[int] = None,
+    recompute_add: bool = False,
+) -> str:
+    print(f"Adding incremental data from: {add_dir}")
+    index_dir_path = Path(index_dir)
+    index_path = index_dir_path / (index_name or "documents.leann")
+
+    # If specified base doesn't exist, try to auto-detect an existing base
+    try:
+        _read_meta(index_path)
+    except FileNotFoundError:
+        auto_base = _autodetect_index_base(index_dir_path)
+        if auto_base is not None:
+            print(f"Auto-detected index base: {auto_base.name}")
+            index_path = auto_base
+            _read_meta(index_path)
+        else:
+            raise FileNotFoundError(
+                f"No index metadata found for base '{index_path.name}'. Build base first with --build-base "
+                f"or provide --index-name to match an existing index (e.g., 'test_doc_files.leann')."
+            )
+
+    # Prepare validated context from core (checks backend/no-recompute and resolves embedding defaults)
+    from leann.api import create_incremental_add_context, incremental_add_texts_with_context
+
+    ctx = create_incremental_add_context(
+        str(index_path),
+        embedding_model=embedding_model,
+        embedding_mode=embedding_mode,
+        data_dir=add_dir,
+        required_exts=file_types,
+        chunk_size=chunk_size,
+        chunk_overlap=chunk_overlap,
+        max_items=max_items,
+    )
+
+    # Use prepared texts from context to perform the add
+    prepared_texts = ctx.prepared_texts or []
+    if not prepared_texts:
+        print("No new chunks to add.")
+        return str(index_path)
+
+    added = incremental_add_texts_with_context(
+        ctx,
+        prepared_texts,
+        ef_construction=ef_construction,
+        recompute=recompute_add,
+    )
+
+    print(f"Incremental add completed. Added {added} chunks. Index: {index_path}")
+    return str(index_path)
+
+
+def main():
+    parser = argparse.ArgumentParser(
+        description="Dynamic add to LEANN HNSW index without recompute",
+        formatter_class=argparse.RawDescriptionHelpFormatter,
+    )
+
+    parser.add_argument("--build-base", action="store_true", help="Build base index")
+    parser.add_argument("--add-incremental", action="store_true", help="Add incremental data")
+
+    parser.add_argument(
+        "--base-dir",
+        type=str,
+        default="/Users/yichuan/Desktop/code/LEANN/leann/data",
+        help="Base data directory",
+    )
+    parser.add_argument(
+        "--add-dir",
+        type=str,
+        default="/Users/yichuan/Desktop/code/LEANN/leann/test_add",
+        help="Incremental data directory",
+    )
+    parser.add_argument(
+        "--index-dir",
+        type=str,
+        default="./test_doc_files",
+        help="Directory containing the index",
+    )
+    parser.add_argument(
+        "--index-name",
+        type=str,
+        default="documents.leann",
+        help=(
+            "Index base file name. If you built via document_rag.py, use 'test_doc_files.leann'. "
+            "Default: documents.leann"
+        ),
+    )
+
+    parser.add_argument(
+        "--embedding-model",
+        type=str,
+        default="facebook/contriever",
+        help="Embedding model name",
+    )
+    parser.add_argument(
+        "--embedding-mode",
+        type=str,
+        default="sentence-transformers",
+        choices=["sentence-transformers", "openai", "mlx", "ollama"],
+        help="Embedding backend mode",
+    )
+
+    parser.add_argument("--chunk-size", type=int, default=256)
+    parser.add_argument("--chunk-overlap", type=int, default=128)
+    parser.add_argument("--file-types", nargs="+", default=None)
+    parser.add_argument("--max-items", type=int, default=-1)
+    parser.add_argument("--ef-construction", type=int, default=32)
+    parser.add_argument(
+        "--recompute-add", action="store_true", help="Enable recompute-mode add (non-compact only)"
+    )
+    parser.add_argument(
+        "--recompute-build",
+        action="store_true",
+        help="Enable recompute-mode base build (non-compact only)",
+    )
+
+    args = parser.parse_args()
+
+    if not args.build_base and not args.add_incremental:
+        print("Nothing to do. Use --build-base and/or --add-incremental.")
+        return
+
+    index_path_str: Optional[str] = None
+
+    if args.build_base:
+        index_path_str = build_base_index(
+            base_dir=args.base_dir,
+            index_dir=args.index_dir,
+            index_name=args.index_name,
+            embedding_model=args.embedding_model,
+            embedding_mode=args.embedding_mode,
+            chunk_size=args.chunk_size,
+            chunk_overlap=args.chunk_overlap,
+            file_types=args.file_types,
+            max_items=args.max_items,
+            ef_construction=args.ef_construction,
+            recompute_build=args.recompute_build,
+        )
+
+    if args.add_incremental:
+        index_path_str = add_incremental(
+            add_dir=args.add_dir,
+            index_dir=args.index_dir,
+            index_name=args.index_name,
+            embedding_model=args.embedding_model,
+            embedding_mode=args.embedding_mode,
+            chunk_size=args.chunk_size,
+            chunk_overlap=args.chunk_overlap,
+            file_types=args.file_types,
+            max_items=args.max_items,
+            ef_construction=args.ef_construction,
+            recompute_add=args.recompute_add,
+        )
+
+    # Optional: quick test query using searcher
+    if index_path_str:
+        try:
+            from leann.api import LeannSearcher
+
+            searcher = LeannSearcher(index_path_str)
+            query = "what is LEANN?"
+            if args.add_incremental:
+                query = "what is the multi vector search and how it works?"
+            results = searcher.search(query, top_k=5)
+            if results:
+                print(f"Sample result: {results[0].text[:80]}...")
+        except Exception:
+            pass
+
+
+if __name__ == "__main__":
+    main()

packages/leann-backend-hnsw/leann_backend_hnsw/hnsw_backend.py

@@ -15,6 +15,7 @@ from leann.registry import register_backend
 from leann.searcher_base import BaseSearcher
 
 from .convert_to_csr import convert_hnsw_graph_to_csr
+from .prune_index import prune_embeddings_preserve_graph_inplace
 
 logger = logging.getLogger(__name__)
 
@@ -90,8 +91,16 @@ class HNSWBuilder(LeannBackendBuilderInterface):
         index_file = index_dir / f"{index_prefix}.index"
         faiss.write_index(index, str(index_file))
 
-        if self.is_compact:
-            self._convert_to_csr(index_file)
+        if self.is_recompute:
+            if self.is_compact:
+                self._convert_to_csr(index_file)
+            else:
+                # Non-compact format: prune only embeddings, keep original graph
+                ok = prune_embeddings_preserve_graph_inplace(str(index_file))
+                if not ok:
+                    raise RuntimeError(
+                        "Pruning embeddings while preserving graph failed for non-compact index"
+                    )
 
     def _convert_to_csr(self, index_file: Path):
         """Convert built index to CSR format"""
@@ -148,7 +157,13 @@ class HNSWSearcher(BaseSearcher):
             self.is_pruned
         )  # In C++ code, it's called is_recompute, but it's only for loading IIUC.
 
-        self._index = faiss.read_index(str(index_file), faiss.IO_FLAG_MMAP, hnsw_config)
+        # If pruned (recompute mode), explicitly skip storage to avoid reading
+        # the pruned section. Still allow MMAP for graph.
+        io_flags = faiss.IO_FLAG_MMAP
+        if self.is_pruned:
+            io_flags |= faiss.IO_FLAG_SKIP_STORAGE
+
+        self._index = faiss.read_index(str(index_file), io_flags, hnsw_config)
 
     def search(
         self,
@@ -251,3 +266,55 @@ class HNSWSearcher(BaseSearcher):
         string_labels = [[str(int_label) for int_label in batch_labels] for batch_labels in labels]
 
         return {"labels": string_labels, "distances": distances}
+
+
+# ---------- Helper API for incremental add (Python-level) ----------
+def add_vectors(
+    index_file_path: str,
+    embeddings: np.ndarray,
+    *,
+    ef_construction: Optional[int] = None,
+    recompute: bool = False,
+) -> None:
+    """Append vectors to an existing non-compact HNSW index.
+
+    Args:
+        index_file_path: Path to the HNSW .index file
+        embeddings: float32 numpy array (N, D)
+        ef_construction: Optional override for efConstruction during insertion
+        recompute: Reserved for future use to control insertion-time recompute behaviors
+    """
+    from . import faiss  # type: ignore
+
+    if embeddings.dtype != np.float32:
+        embeddings = embeddings.astype(np.float32)
+    if not embeddings.flags.c_contiguous:
+        embeddings = np.ascontiguousarray(embeddings, dtype=np.float32)
+
+    # Load index normally to ensure storage is present; toggle is_recompute on the object
+    index = faiss.read_index(str(index_file_path), faiss.IO_FLAG_MMAP)
+
+    # Best-effort: explicitly set flag on the object if the binding exposes it
+    try:
+        index.is_recompute = bool(recompute)
+    except Exception:
+        pass
+    try:
+        if ef_construction is not None:
+            index.hnsw.efConstruction = int(ef_construction)
+    except Exception:
+        # Best-effort; ignore if backend doesn't expose setter
+        pass
+
+    # For non-compact HNSW, calling add directly is sufficient. When is_recompute is set
+    # (via config or attribute), FAISS will run the insertion/search path accordingly.
+    # To strictly follow per-point insert semantics in recompute mode, add one-by-one.
+    if recompute:
+        # Insert row by row
+        n = embeddings.shape[0]
+        for i in range(n):
+            row = embeddings[i : i + 1]
+            index.add(1, faiss.swig_ptr(row))
+    else:
+        index.add(embeddings.shape[0], faiss.swig_ptr(embeddings))
+    faiss.write_index(index, str(index_file_path))

packages/leann-backend-hnsw/leann_backend_hnsw/prune_index.py

@@ -0,0 +1,149 @@
+import os
+import struct
+from pathlib import Path
+
+from .convert_to_csr import (
+    EXPECTED_HNSW_FOURCCS,
+    NULL_INDEX_FOURCC,
+    read_struct,
+    read_vector_raw,
+)
+
+
+def _write_vector_raw(f_out, count: int, data_bytes: bytes) -> None:
+    """Write a vector in the same binary layout as read_vector_raw reads: <Q count> + raw bytes."""
+    f_out.write(struct.pack("<Q", count))
+    if count > 0 and data_bytes:
+        f_out.write(data_bytes)
+
+
+def prune_embeddings_preserve_graph(input_filename: str, output_filename: str) -> bool:
+    """
+    Copy an original (non-compact) HNSW index file while pruning the trailing embedding storage.
+    Preserves the graph structure and metadata exactly; only writes a NULL storage marker instead of
+    the original storage fourcc and payload.
+
+    Returns True on success.
+    """
+    print(f"Pruning embeddings from {input_filename} to {output_filename}")
+    print("--------------------------------")
+    # running in mode is-recompute=True and is-compact=False
+    in_path = Path(input_filename)
+    out_path = Path(output_filename)
+
+    try:
+        with open(in_path, "rb") as f_in, open(out_path, "wb") as f_out:
+            # Header
+            index_fourcc = read_struct(f_in, "<I")
+            if index_fourcc not in EXPECTED_HNSW_FOURCCS:
+                # Still proceed, but this is unexpected
+                pass
+            f_out.write(struct.pack("<I", index_fourcc))
+
+            d = read_struct(f_in, "<i")
+            ntotal_hdr = read_struct(f_in, "<q")
+            dummy1 = read_struct(f_in, "<q")
+            dummy2 = read_struct(f_in, "<q")
+            is_trained = read_struct(f_in, "?")
+            metric_type = read_struct(f_in, "<i")
+            f_out.write(struct.pack("<i", d))
+            f_out.write(struct.pack("<q", ntotal_hdr))
+            f_out.write(struct.pack("<q", dummy1))
+            f_out.write(struct.pack("<q", dummy2))
+            f_out.write(struct.pack("<?", is_trained))
+            f_out.write(struct.pack("<i", metric_type))
+
+            if metric_type > 1:
+                metric_arg = read_struct(f_in, "<f")
+                f_out.write(struct.pack("<f", metric_arg))
+
+            # Vectors: assign_probas (double), cum_nneighbor_per_level (int32), levels (int32)
+            cnt, data = read_vector_raw(f_in, "d")
+            _write_vector_raw(f_out, cnt, data)
+
+            cnt, data = read_vector_raw(f_in, "i")
+            _write_vector_raw(f_out, cnt, data)
+
+            cnt, data = read_vector_raw(f_in, "i")
+            _write_vector_raw(f_out, cnt, data)
+
+            # Probe potential extra alignment/flag byte present in some original formats
+            probe = f_in.read(1)
+            if probe:
+                if probe == b"\x00":
+                    # Preserve this unexpected 0x00 byte
+                    f_out.write(probe)
+                else:
+                    # Likely part of the next vector; rewind
+                    f_in.seek(-1, os.SEEK_CUR)
+
+            # Offsets (uint64) and neighbors (int32)
+            cnt, data = read_vector_raw(f_in, "Q")
+            _write_vector_raw(f_out, cnt, data)
+
+            cnt, data = read_vector_raw(f_in, "i")
+            _write_vector_raw(f_out, cnt, data)
+
+            # Scalar params
+            entry_point = read_struct(f_in, "<i")
+            max_level = read_struct(f_in, "<i")
+            ef_construction = read_struct(f_in, "<i")
+            ef_search = read_struct(f_in, "<i")
+            dummy_upper_beam = read_struct(f_in, "<i")
+            f_out.write(struct.pack("<i", entry_point))
+            f_out.write(struct.pack("<i", max_level))
+            f_out.write(struct.pack("<i", ef_construction))
+            f_out.write(struct.pack("<i", ef_search))
+            f_out.write(struct.pack("<i", dummy_upper_beam))
+
+            # Storage fourcc (if present) — write NULL marker and drop any remaining data
+            try:
+                read_struct(f_in, "<I")
+                # Regardless of original, write NULL
+                f_out.write(struct.pack("<I", NULL_INDEX_FOURCC))
+                # Discard the rest of the file (embedding payload)
+                # (Do not copy anything else)
+            except EOFError:
+                # No storage section; nothing else to write
+                pass
+
+        return True
+    except Exception:
+        # Best-effort cleanup
+        try:
+            if out_path.exists():
+                out_path.unlink()
+        except OSError:
+            pass
+        return False
+
+
+def prune_embeddings_preserve_graph_inplace(index_file_path: str) -> bool:
+    """
+    Convenience wrapper: write pruned file to a temporary path next to the
+    original, then atomically replace on success.
+    """
+    print(f"Pruning embeddings from {index_file_path} to {index_file_path}")
+    print("--------------------------------")
+    # running in mode is-recompute=True and is-compact=False
+    src = Path(index_file_path)
+    tmp = src.with_suffix(".pruned.tmp")
+    ok = prune_embeddings_preserve_graph(str(src), str(tmp))
+    if not ok:
+        if tmp.exists():
+            try:
+                tmp.unlink()
+            except OSError:
+                pass
+        return False
+    try:
+        os.replace(str(tmp), str(src))
+    except Exception:
+        # Rollback on failure
+        try:
+            if tmp.exists():
+                tmp.unlink()
+        except OSError:
+            pass
+        return False
+    return True

packages/leann-core/src/leann/api.py

@@ -5,6 +5,7 @@ with the correct, original embedding logic from the user's reference code.
 
 import json
 import logging
+import os
 import pickle
 import re
 import subprocess
@@ -19,6 +20,7 @@ import numpy as np
 from leann.interface import LeannBackendSearcherInterface
 
 from .chat import get_llm
+from .embedding_server_manager import EmbeddingServerManager
 from .interface import LeannBackendFactoryInterface
 from .metadata_filter import MetadataFilterEngine
 from .registry import BACKEND_REGISTRY
@@ -118,6 +120,20 @@ class SearchResult:
     metadata: dict[str, Any] = field(default_factory=dict)
 
 
+@dataclass
+class IncrementalAddContext:
+    """Prepared context for safe incremental add operations on an index."""
+
+    index_path: str
+    passages_file: Path
+    offsets_file: Path
+    vector_index_file: Path
+    embedding_model: str
+    embedding_mode: str
+    distance_metric: str
+    prepared_texts: Optional[list[str]] = None
+
+
 class PassageManager:
     def __init__(
         self, passage_sources: list[dict[str, Any]], metadata_file_path: Optional[str] = None
@@ -476,9 +492,7 @@ class LeannBuilder:
             is_compact = self.backend_kwargs.get("is_compact", True)
             is_recompute = self.backend_kwargs.get("is_recompute", True)
             meta_data["is_compact"] = is_compact
-            meta_data["is_pruned"] = (
-                is_compact and is_recompute
-            )  # Pruned only if compact and recompute
+            meta_data["is_pruned"] = is_recompute  # Pruned only if compact and recompute
         with open(leann_meta_path, "w", encoding="utf-8") as f:
             json.dump(meta_data, f, indent=2)
 
@@ -1018,8 +1032,405 @@ class LeannChat:
         except Exception:
             pass
 
-    def __del__(self):
+
+# ------------------------------
+# Incremental Add Utilities (HNSW no-recompute only)
+# ------------------------------
+
+
+def _resolve_index_paths(index_path: str) -> tuple[Path, Path, Path]:
+    """Given base index path (without extension), return (passages.jsonl, passages.idx, vector.index).
+
+    For HNSW, vector index file is typically <stem>.index (e.g., documents.index) even when base is
+    'documents.leann'. We prefer an existing <stem>.index, otherwise fall back to <name>.index.
+    """
+    base = Path(index_path)
+    passages_file = base.parent / f"{base.name}.passages.jsonl"
+    offsets_file = base.parent / f"{base.name}.passages.idx"
+    candidate_name_index = base.parent / f"{base.name}.index"
+    candidate_stem_index = base.parent / f"{base.stem}.index"
+    vector_index_file = (
+        candidate_stem_index if candidate_stem_index.exists() else candidate_name_index
+    )
+    return passages_file, offsets_file, vector_index_file
+
+
+def _read_meta_file(index_path: str) -> dict[str, Any]:
+    meta_path = Path(f"{index_path}.meta.json")
+    if not meta_path.exists():
+        raise FileNotFoundError(f"Leann metadata file not found: {meta_path}")
+    with open(meta_path, encoding="utf-8") as f:
+        return json.load(f)
+
+
+def _load_offset_map_pickle(offsets_file: Path) -> dict[str, int]:
+    if not offsets_file.exists():
+        return {}
+    with open(offsets_file, "rb") as f:
+        return pickle.load(f)
+
+
+def _append_passages_and_update_offsets(
+    passages_file: Path, offsets_file: Path, new_texts: list[str]
+) -> list[str]:
+    """Append new texts to passages file, update offset map, and return assigned string IDs.
+
+    IDs are assigned as incrementing integers based on existing keys in the offset map.
+    """
+    offset_map = _load_offset_map_pickle(offsets_file)
+    # Compute next numeric id
+    numeric_ids = [int(x) for x in offset_map.keys() if str(x).isdigit()]
+    next_id_num = (max(numeric_ids) + 1) if numeric_ids else 0
+    assigned_ids: list[str] = []
+
+    with open(passages_file, "a", encoding="utf-8") as f:
+        for text in new_texts:
+            offset = f.tell()
+            str_id = str(next_id_num)
+            json.dump({"id": str_id, "text": text, "metadata": {}}, f, ensure_ascii=False)
+            f.write("\n")
+            offset_map[str_id] = offset
+            assigned_ids.append(str_id)
+            next_id_num += 1
+
+    with open(offsets_file, "wb") as f:
+        pickle.dump(offset_map, f)
+
+    return assigned_ids
+
+
+def incremental_add_texts(
+    index_path: str,
+    texts: list[str],
+    *,
+    embedding_model: Optional[str] = None,
+    embedding_mode: Optional[str] = None,
+    ef_construction: Optional[int] = None,
+    recompute: bool = False,
+) -> int:
+    """Incrementally add text chunks to an existing HNSW index built with no-recompute.
+
+    - Validates backend is HNSW and index is non-compact (no-recompute path)
+    - Appends passages and offsets
+    - Computes embeddings and appends to the HNSW vector index
+
+    Returns number of added chunks.
+    """
+    if not texts:
+        return 0
+
+    meta = _read_meta_file(index_path)
+    if meta.get("backend_name") != "hnsw":
+        raise RuntimeError("Incremental add is currently supported only for HNSW backend")
+    if meta.get("is_compact", True):
+        raise RuntimeError(
+            "Index is compact/pruned. Rebuild base with is_recompute=False and is_compact=False for incremental add."
+        )
+
+    passages_file, offsets_file, vector_index_file = _resolve_index_paths(index_path)
+    if not vector_index_file.exists():
+        raise FileNotFoundError(
+            f"Vector index file missing: {vector_index_file}. Build base first with LeannBuilder."
+        )
+
+    # Resolve embedding config from meta if not provided
+    model_name = embedding_model or meta.get("embedding_model", "facebook/contriever")
+    mode_name = embedding_mode or meta.get("embedding_mode", "sentence-transformers")
+
+    # Append passages and update offsets
+    assigned_ids = _append_passages_and_update_offsets(passages_file, offsets_file, texts)
+
+    # Compute embeddings
+    # Embedding computation path
+    esm = None
+    port = None
+    if recompute:
+        # Determine distance metric early for server config
+        distance_metric = meta.get("backend_kwargs", {}).get("distance_metric", "mips").lower()
+        # Start embedding server and compute via ZMQ for consistency with recompute semantics
+        passages_source_file = f"{index_path}.meta.json"
+        esm = EmbeddingServerManager(
+            backend_module_name="leann_backend_hnsw.hnsw_embedding_server",
+        )
+        started, port = esm.start_server(
+            port=5557,
+            model_name=model_name,
+            embedding_mode=mode_name,
+            passages_file=passages_source_file,
+            distance_metric=distance_metric,
+            enable_warmup=False,
+        )
+        if not started:
+            raise RuntimeError("Failed to start embedding server for recompute add")
+        embeddings = compute_embeddings_via_server(texts, model_name, port)
+    else:
+        embeddings = compute_embeddings(
+            texts,
+            model_name=model_name,
+            mode=mode_name,
+            use_server=False,
+            is_build=True,
+        )
+
+    # Normalize for cosine if needed
+    if "distance_metric" not in locals():
+        distance_metric = meta.get("backend_kwargs", {}).get("distance_metric", "mips").lower()
+    if distance_metric == "cosine":
+        norms = np.linalg.norm(embeddings, axis=1, keepdims=True)
+        norms[norms == 0] = 1
+        embeddings = embeddings / norms
+
+    # Append via backend helper (supports ef_construction/recompute plumbing)
+    try:
+        from leann_backend_hnsw.hnsw_backend import add_vectors as hnsw_add_vectors  # type: ignore
+    except Exception as e:
+        raise RuntimeError(
+            "Failed to import HNSW backend add helper. Ensure HNSW backend is installed."
+        ) from e
+
+    # Propagate ZMQ port to FAISS add path when recompute is True
+    if recompute and port is not None:
+        os.environ["LEANN_ZMQ_PORT"] = str(port)
+
+    hnsw_add_vectors(
+        str(vector_index_file),
+        embeddings,
+        ef_construction=ef_construction,
+        recompute=recompute,
+    )
+
+    # Stop server after add when recompute path used
+    if esm is not None:
         try:
-            self.cleanup()
+            esm.stop_server()
         except Exception:
             pass
+
+    # Sanity: ids length should match embeddings rows
+    if len(assigned_ids) != embeddings.shape[0]:
+        warnings.warn(
+            f"Assigned {len(assigned_ids)} IDs but computed {embeddings.shape[0]} embeddings.",
+            UserWarning,
+            stacklevel=2,
+        )
+
+    return len(assigned_ids)
+
+
+def create_incremental_add_context(
+    index_path: str,
+    *,
+    # Optional embedding choices; if None will use meta
+    embedding_model: Optional[str] = None,
+    embedding_mode: Optional[str] = None,
+    # Optional data-to-text preparation in context
+    data_dir: Optional[str] = None,
+    required_exts: Optional[list[str]] = None,
+    chunk_size: int = 256,
+    chunk_overlap: int = 128,
+    max_items: int = -1,
+) -> IncrementalAddContext:
+    """Validate index and prepare context for repeated incremental adds.
+
+    Additionally, if data_dir is provided, this function will load documents,
+    chunk them to texts with the specified parameters, and store them in ctx.prepared_texts.
+    """
+    meta = _read_meta_file(index_path)
+    if meta.get("backend_name") != "hnsw":
+        raise RuntimeError("Incremental add is currently supported only for HNSW backend")
+    if meta.get("is_compact", True):
+        raise RuntimeError(
+            "Index is compact/pruned. Rebuild base with is_recompute=False and is_compact=False for incremental add."
+        )
+
+    passages_file, offsets_file, vector_index_file = _resolve_index_paths(index_path)
+    if not vector_index_file.exists():
+        raise FileNotFoundError(
+            f"Vector index file missing: {vector_index_file}. Build base first with LeannBuilder."
+        )
+
+    model_name = embedding_model or meta.get("embedding_model", "facebook/contriever")
+    mode_name = embedding_mode or meta.get("embedding_mode", "sentence-transformers")
+    distance_metric = meta.get("backend_kwargs", {}).get("distance_metric", "mips").lower()
+
+    prepared_texts: Optional[list[str]] = None
+    if data_dir is not None:
+        try:
+            from llama_index.core import SimpleDirectoryReader  # type: ignore
+            from llama_index.core.node_parser import SentenceSplitter  # type: ignore
+        except Exception as e:
+            raise RuntimeError(
+                "llama-index-core is required when using data_dir in create_incremental_add_context"
+            ) from e
+
+        reader_kwargs: dict[str, Any] = {"recursive": True, "encoding": "utf-8"}
+        if required_exts:
+            reader_kwargs["required_exts"] = required_exts
+        documents = SimpleDirectoryReader(data_dir, **reader_kwargs).load_data(show_progress=True)
+        if documents:
+            splitter = SentenceSplitter(
+                chunk_size=chunk_size,
+                chunk_overlap=chunk_overlap,
+                separator=" ",
+                paragraph_separator="\n\n",
+            )
+            prepared_texts = []
+            for doc in documents:
+                try:
+                    nodes = splitter.get_nodes_from_documents([doc])
+                    if nodes:
+                        prepared_texts.extend([node.get_content() for node in nodes])
+                except Exception:
+                    content = doc.get_content()
+                    if content and content.strip():
+                        prepared_texts.append(content.strip())
+            if max_items > 0 and len(prepared_texts) > max_items:
+                prepared_texts = prepared_texts[:max_items]
+
+    return IncrementalAddContext(
+        index_path=index_path,
+        passages_file=passages_file,
+        offsets_file=offsets_file,
+        vector_index_file=vector_index_file,
+        embedding_model=model_name,
+        embedding_mode=mode_name,
+        distance_metric=distance_metric,
+        prepared_texts=prepared_texts,
+    )
+
+
+def incremental_add_texts_with_context(
+    ctx: IncrementalAddContext,
+    texts: list[str],
+    *,
+    ef_construction: Optional[int] = None,
+    recompute: bool = False,
+) -> int:
+    """Incrementally add texts using a prepared context (no repeated validation).
+
+    For non-compact HNSW, ef_construction (efConstruction) can be overridden during insertion.
+    """
+    if not texts:
+        return 0
+
+    # Append passages & offsets
+    _append_passages_and_update_offsets(ctx.passages_file, ctx.offsets_file, texts)
+
+    # Compute embeddings
+    # Embedding computation path
+    esm = None
+    port = None
+    if recompute:
+        passages_source_file = f"{ctx.index_path}.meta.json"
+        esm = EmbeddingServerManager(
+            backend_module_name="leann_backend_hnsw.hnsw_embedding_server",
+        )
+        started, port = esm.start_server(
+            port=5557,
+            model_name=ctx.embedding_model,
+            embedding_mode=ctx.embedding_mode,
+            passages_file=passages_source_file,
+            distance_metric=ctx.distance_metric,
+            enable_warmup=False,
+        )
+        if not started:
+            raise RuntimeError("Failed to start embedding server for recompute add")
+        embeddings = compute_embeddings_via_server(texts, ctx.embedding_model, port)
+    else:
+        embeddings = compute_embeddings(
+            texts,
+            model_name=ctx.embedding_model,
+            mode=ctx.embedding_mode,
+            use_server=False,
+            is_build=True,
+        )
+
+    # Normalize for cosine if needed
+    if ctx.distance_metric == "cosine":
+        norms = np.linalg.norm(embeddings, axis=1, keepdims=True)
+        norms[norms == 0] = 1
+        embeddings = embeddings / norms
+
+    # Append via backend helper (supports ef_construction/recompute plumbing)
+    try:
+        from leann_backend_hnsw.hnsw_backend import add_vectors as hnsw_add_vectors  # type: ignore
+    except Exception as e:
+        raise RuntimeError(
+            "Failed to import HNSW backend add helper. Ensure HNSW backend is installed."
+        ) from e
+
+    if recompute and port is not None:
+        os.environ["LEANN_ZMQ_PORT"] = str(port)
+
+    hnsw_add_vectors(
+        str(ctx.vector_index_file),
+        embeddings,
+        ef_construction=ef_construction,
+        recompute=recompute,
+    )
+
+    # Stop server after add when recompute path used
+    if esm is not None:
+        try:
+            esm.stop_server()
+        except Exception:
+            pass
+
+    return embeddings.shape[0]
+
+
+def incremental_add_directory(
+    index_path: str,
+    data_dir: str,
+    *,
+    chunk_size: int = 256,
+    chunk_overlap: int = 128,
+    required_exts: Optional[list[str]] = None,
+    max_items: int = -1,
+    embedding_model: Optional[str] = None,
+    embedding_mode: Optional[str] = None,
+) -> int:
+    """Load documents from a directory, chunk them, and incrementally add to an index.
+
+    Chunking uses LlamaIndex SentenceSplitter for simplicity and avoids external app dependencies.
+    """
+    try:
+        from llama_index.core import SimpleDirectoryReader  # type: ignore
+        from llama_index.core.node_parser import SentenceSplitter  # type: ignore
+    except Exception as e:
+        raise RuntimeError("llama-index-core is required for incremental_add_directory") from e
+
+    reader_kwargs: dict[str, Any] = {"recursive": True, "encoding": "utf-8"}
+    if required_exts:
+        reader_kwargs["required_exts"] = required_exts
+    documents = SimpleDirectoryReader(data_dir, **reader_kwargs).load_data(show_progress=True)
+    if not documents:
+        return 0
+
+    # Traditional text chunking
+    splitter = SentenceSplitter(
+        chunk_size=chunk_size,
+        chunk_overlap=chunk_overlap,
+        separator=" ",
+        paragraph_separator="\n\n",
+    )
+    all_texts: list[str] = []
+    for doc in documents:
+        try:
+            nodes = splitter.get_nodes_from_documents([doc])
+            if nodes:
+                all_texts.extend([node.get_content() for node in nodes])
+        except Exception:
+            content = doc.get_content()
+            if content and content.strip():
+                all_texts.append(content.strip())
+
+    if max_items > 0 and len(all_texts) > max_items:
+        all_texts = all_texts[:max_items]
+
+    return incremental_add_texts(
+        index_path,
+        all_texts,
+        embedding_model=embedding_model,
+        embedding_mode=embedding_mode,
+    )