refactor(diskann): decouple from libaio via dlopen (#532)

Co-authored-by: Zefeng Yin <yinzefeng.yzf@alibaba-inc.com>
2026-07-16 17:58:25 +08:00
parent 23538ab876
commit ec8a78ee08
49 changed files with 1108 additions and 809 deletions
@@ -60,14 +60,6 @@ jobs:
          sudo apt-get install -y clang libomp-dev
        shell: bash

-      - name: Install AIO 
-        if: runner.os == 'Linux' && runner.arch == 'X64'
-        run: |
-          sudo apt-get update
-          sudo apt-get install -y --no-install-recommends \
-            libaio-dev
-        shell: bash
-
      - name: Print CPU info
        if: runner.os == 'Linux'
        run: lscpu
@@ -183,3 +175,41 @@ jobs:
          ./c_api_index_example
          ./c_api_optimized_example
        shell: bash
+
+      # ------------------------------------------------------------------ #
+      # DiskAnn libaio round: install libaio and re-run tests 
+      # ------------------------------------------------------------------ #
+      - name: Install libaio runtime
+        if: matrix.platform == 'linux-x64'
+        run: |
+          sudo apt-get update -y
+          # libaio1t64 on Ubuntu 24.04+ (t64 transition), libaio1 on older
+          sudo apt-get install -y libaio1t64 || sudo apt-get install -y libaio1
+          echo "=== libaio status (should be present) ==="
+          dpkg -l | grep -i libaio || true
+          ldconfig -p | grep libaio || true
+        shell: bash
+
+      - name: Run DiskAnn C++ Tests (w/ libaio)
+        if: matrix.platform == 'linux-x64'
+        run: |
+          cd "$GITHUB_WORKSPACE/build"
+          ctest -R diskann --output-on-failure --parallel $NPROC
+        shell: bash
+
+      - name: Run DiskAnn Python Tests (w/ libaio)
+        if: matrix.platform == 'linux-x64'
+        run: |
+          cd "$GITHUB_WORKSPACE"
+          python -m pytest python/tests/test_collection_diskann.py -v
+        shell: bash
+
+      # Verify installing libaio does not affect existing non-DiskAnn tests.
+      - name: Run HNSW Tests (w/ libaio)
+        if: matrix.platform == 'linux-x64'
+        run: |
+          cd "$GITHUB_WORKSPACE/build"
+          ctest -R hnsw --output-on-failure --parallel $NPROC
+          cd "$GITHUB_WORKSPACE"
+          python -m pytest python/tests/test_hnsw_contiguous_memory.py -v
+        shell: bash
@@ -34,13 +34,6 @@ jobs:
          cache: 'pip'
          cache-dependency-path: 'pyproject.toml'

-      - name: Install system dependencies
-        run: |
-          sudo apt-get update
-          sudo apt-get install -y --no-install-recommends \
-            libaio-dev
-        shell: bash
-
      - name: Set up environment variables
        run: |
          NPROC=$(nproc 2>/dev/null || echo 2)
@@ -47,7 +47,7 @@ jobs:
        if: steps.changed_files.outputs.any_changed == 'true'
        run: |
          sudo apt-get update
-          sudo apt-get install -y clang-tidy=1:18.0-59~exp2 cmake ninja-build libomp-dev libaio-dev
+          sudo apt-get install -y clang-tidy=1:18.0-59~exp2 cmake ninja-build libomp-dev

      - name: Setup ccache
        if: steps.changed_files.outputs.any_changed == 'true'
@@ -48,8 +48,8 @@ jobs:
      - name: Install system dependencies
        run: |
          sudo apt-get update
-          sudo apt-get install -y --no-install-recommends \
-            lcov libaio-dev
+          sudo apt-get install -y --no-install-recommends lcov
+          sudo apt-get install -y libaio1t64 || sudo apt-get install -y libaio1
        shell: bash

      - name: Install dependencies
@@ -122,7 +122,7 @@ else()
 endif()
 message(STATUS "RABITQ_ARCH_FLAG: ${RABITQ_ARCH_FLAG}")

-# DiskAnn support (Linux x86_64 only, requires libaio)
+# DiskAnn support (Linux x86_64 only; libaio loaded at runtime via dlopen)
 if(CMAKE_SYSTEM_NAME STREQUAL "Linux" AND CMAKE_SYSTEM_PROCESSOR MATCHES "x86_64|i686|i386" AND NOT ANDROID AND NOT IOS)
  set(DISKANN_SUPPORTED ON)
  add_definitions(-DDISKANN_SUPPORTED=1)
@@ -180,24 +180,9 @@ if(BUILD_PYTHON_BINDINGS)
    install(TARGETS _zvec LIBRARY DESTINATION ${ZVEC_PY_INSTALL_DIR}/zvec
            COMPONENT python)

-    # DiskAnn ships as a runtime-loaded shared module
-    # (libzvec_diskann_plugin.so) that is brought online implicitly the
-    # first time a DiskAnn index is created — users never call any load
-    # function. The Python extension resolves the module next to _zvec.so
-    # (see the $ORIGIN rpath in src/binding/python/CMakeLists.txt); the
-    # module must therefore be installed alongside _zvec.so, i.e. inside the
-    # zvec package directory as well.
-    #
-    # Gate on DISKANN_SUPPORTED, not on the target's existence: on unsupported
-    # platforms (e.g. macOS / ARM64) the core_knn_diskann target is still
-    # defined, but built from an empty stub (src/core/algorithm/CMakeLists.txt)
-    # with zero exported symbols and a runtime load path compiled out
-    # (#if DISKANN_SUPPORTED). Shipping that stub is pure dead weight, so it is
-    # only packaged where DiskAnn is real — currently Linux x86_64 with libaio.
-    if(DISKANN_SUPPORTED)
-        install(TARGETS core_knn_diskann LIBRARY DESTINATION ${ZVEC_PY_INSTALL_DIR}/zvec
-                COMPONENT python)
-    endif()
+    # DiskAnn is now statically linked into _zvec.so via --whole-archive
+    # (see src/binding/python/CMakeLists.txt -> core_knn_diskann_static),
+    # so no separate runtime .so needs to be installed in the wheel.
    # Bundle cppjieba's dictionary files so the `jieba` FTS tokenizer works
    # out of the box. python/zvec/__init__.py resolves this directory via
    # importlib.resources and registers it with set_default_jieba_dict_dir().
@@ -17,7 +17,6 @@ get_filename_component(ZVEC_ROOT_DIR "${CMAKE_CURRENT_LIST_DIR}/../.." ABSOLUTE)
 set(ZVEC_INCLUDE_DIR ${ZVEC_ROOT_DIR}/src/include)
 set(ZVEC_LIB_DIR ${ZVEC_ROOT_DIR}/${HOST_BUILD_DIR}/lib)

-# Add include and library search paths
 include_directories(${ZVEC_INCLUDE_DIR})
 set(ZVEC_LIB_SEARCH_DIRS ${ZVEC_LIB_DIR})

@@ -181,11 +181,6 @@ test-command = "cd {project} && pytest python/tests -v --tb=short"
 build-verbosity = 1

 [tool.cibuildwheel.linux]
-# libaio is required by the C++ backend; install it inside the manylinux
-# container (manylinux_2_28 is AlmaLinux 8 based, so use dnf/libaio-devel).
-# libaio-devel lives in BaseOS; disable EPEL so a flaky EPEL mirror cannot
-# break metadata refresh.
-before-all = "dnf install -y --disablerepo=epel libaio-devel"
 archs = ["auto"]
 environment = { CMAKE_GENERATOR = "Unix Makefiles", CMAKE_BUILD_PARALLEL_LEVEL = "16" }
 manylinux-x86_64-image = "manylinux_2_28"
@@ -13,19 +13,14 @@ from typing import Any, Generator
 from zvec.typing import DataType, StatusCode, MetricType, QuantizeType
 import zvec

-
-# Cache the DiskAnn plugin preload status so we pay the load cost once per
-# test session. The plugin normally auto-loads on first DiskAnn use, but we
-# preload it explicitly here so a missing libaio / misplaced plugin .so
-# surfaces as a clear pytest skip instead of a confusing
-# "Create vector column indexer failed" deep inside the collection code path.
 _DISKANN_PRELOAD_REASON: str | None = None
 _DISKANN_PRELOAD_DONE: bool = False


 def _ensure_diskann_runtime_or_reason() -> str | None:
-    """Preload the DiskAnn plugin and return None on success or a human-readable
-    skip reason on failure. Idempotent across calls."""
+    """Check whether DiskAnn is available on this platform and return None
+    on success or a human-readable skip reason on failure. Idempotent across
+    calls."""
    global _DISKANN_PRELOAD_DONE, _DISKANN_PRELOAD_REASON
    if _DISKANN_PRELOAD_DONE:
        return _DISKANN_PRELOAD_REASON
@@ -35,22 +30,6 @@ def _ensure_diskann_runtime_or_reason() -> str | None:
        _DISKANN_PRELOAD_REASON = "DiskAnn only supported on Linux x86_64"
        return _DISKANN_PRELOAD_REASON

-    if not zvec.is_libaio_available():
-        _DISKANN_PRELOAD_REASON = (
-            "libaio is not available on this host; DiskAnn cannot run. "
-            "Install libaio1 (or libaio1t64 on Ubuntu 24.04+) and retry."
-        )
-        return _DISKANN_PRELOAD_REASON
-
-    status = zvec.load_diskann_plugin()
-    if status != zvec.DISKANN_PLUGIN_OK:
-        _DISKANN_PRELOAD_REASON = (
-            f"Failed to load DiskAnn plugin (status={status}); "
-            "check that libzvec_diskann_plugin.so is installed alongside "
-            "_zvec.so in the Python site-packages directory."
-        )
-        return _DISKANN_PRELOAD_REASON
-
    _DISKANN_PRELOAD_REASON = None
    return None

@@ -148,8 +127,7 @@ def full_schema_new(request) -> CollectionSchema:
    else:
        nullable, has_index, vector_index = True, False, HnswIndexParam()

-    # Skip DiskAnn tests on unsupported platforms or when the runtime cannot
-    # be brought up (missing libaio, plugin .so not installed, etc.).
+    # Skip DiskAnn tests on unsupported platforms.
    from zvec.model.param import DiskAnnIndexParam

    if isinstance(vector_index, DiskAnnIndexParam):
@@ -13,17 +13,15 @@
 # limitations under the License.
 """End-to-end collection tests for the DiskAnn index.

-Mirrors ``test_collection_hnsw_rabitq.py`` but targets the DiskAnn plugin.
+Mirrors ``test_collection_hnsw_rabitq.py`` but targets the DiskAnn index.

 Two platform-level prerequisites are enforced at module import time:

 1. DiskAnn is currently built only for Linux x86_64 — other platforms are
   skipped wholesale.
-2. The DiskAnn backend lives in a *runtime-loaded* plugin
-   (``libzvec_diskann_plugin.so``). It must be loaded with ``RTLD_GLOBAL |
-   RTLD_NOW`` BEFORE ``import zvec`` so that the plugin's ``IndexFactory``
-   singleton is unified with the one inside ``_zvec.so``. After ``import
-   zvec`` we must also call ``zvec.load_diskann_plugin()`` exactly once.
+2. libaio is loaded eagerly (via dlopen) inside DiskAnnBuilder::init() /
+   DiskAnnStreamer::init(). If libaio is missing, DiskAnn falls back to
+   synchronous pread() — the tests still run but with degraded performance.

 If either prerequisite fails the whole module is skipped so the rest of the
 test-suite is not affected.
@@ -32,7 +30,6 @@ test-suite is not affected.
 from __future__ import annotations

 import math
-import os
 import platform
 import sys

@@ -46,13 +43,6 @@ pytestmark = pytest.mark.skipif(
    reason="DiskAnn plugin is only supported on Linux x86_64",
 )

-# Promote all symbols in subsequently-loaded DSOs to the global namespace and
-# resolve relocations eagerly. This is REQUIRED so the DiskAnn plugin can see
-# the ``IndexFactory`` singleton that lives in ``_zvec.so`` and vice versa.
-# See: DiskAnn RTLD_GLOBAL + RTLD_NOW Requirement.
-if sys.platform == "linux":
-    sys.setdlopenflags(sys.getdlopenflags() | os.RTLD_GLOBAL | os.RTLD_NOW)
-
 import zvec  # noqa: E402

 from zvec import (  # noqa: E402
@@ -17,6 +17,7 @@ import pytest
 from zvec import (
    DataType,
    IndexType,
+    IOBackendType,
    MetricType,
    QuantizeType,
    Status,
@@ -32,6 +33,7 @@ from zvec import (
    [
        (DataType.FLOAT, "FLOAT"),
        (IndexType.HNSW, "HNSW"),
+        (IOBackendType.PREAD, "PREAD"),
        (MetricType.COSINE, "COSINE"),
        (QuantizeType.INT8, "INT8"),
        (StatusCode.OK, "OK"),
@@ -46,6 +48,7 @@ def test_enum_names(member, name):
    [
        (DataType.FLOAT, 8),
        (IndexType.HNSW, 1),
+        (IOBackendType.PREAD, 0),
        (MetricType.COSINE, 3),
        (QuantizeType.INT8, 2),
        (StatusCode.OK, 0),
@@ -91,11 +94,29 @@ def test_data_type_has_member(member):
    assert member in DataType.__members__


-@pytest.mark.parametrize("member", ["HNSW", "IVF", "FLAT", "INVERT"])
+@pytest.mark.parametrize(
+    "member",
+    [
+        "UNDEFINED",
+        "HNSW",
+        "IVF",
+        "FLAT",
+        "HNSW_RABITQ",
+        "DISKANN",
+        "VAMANA",
+        "INVERT",
+        "FTS",
+    ],
+)
 def test_index_type_has_member(member):
    assert member in IndexType.__members__


+@pytest.mark.parametrize("member", ["PREAD", "LIBAIO"])
+def test_io_backend_type_has_member(member):
+    assert member in IOBackendType.__members__
+
+
@pytest.mark.parametrize("member", ["FP16", "INT8", "INT4", "UNDEFINED"])
 def test_quantize_type_has_member(member):
    assert member in QuantizeType.__members__
@@ -39,6 +39,8 @@ try:

    from zvec._zvec import (
        get_default_jieba_dict_dir,
+        io_backend_description,
+        io_backend_type,
        set_default_jieba_dict_dir,
    )

@@ -52,21 +54,6 @@ except Exception:
 # Public API — grouped by category
 # ==============================

-# —— DiskAnn runtime plugin ——
-# Re-export the plugin management entry points defined by the C++ extension.
-# DiskAnn normally auto-loads on first use; these APIs let tests and
-# diagnostic tools preload the plugin and get a clear error if libaio is
-# missing or the plugin shared object cannot be located.
-from zvec._zvec import (
-    DISKANN_PLUGIN_DLOPEN_FAILED,
-    DISKANN_PLUGIN_LIBAIO_MISSING,
-    DISKANN_PLUGIN_OK,
-    DISKANN_PLUGIN_UNSUPPORTED_PLATFORM,
-    is_diskann_plugin_loaded,
-    is_libaio_available,
-    load_diskann_plugin,
-)
-
 from . import model as model

 # —— Extensions ——
@@ -131,6 +118,7 @@ from .tool import require_module
 from .typing import (
    DataType,
    IndexType,
+    IOBackendType,
    MetricType,
    QuantizeType,
    Status,
@@ -151,6 +139,8 @@ __all__ = [
    "open",
    "set_default_jieba_dict_dir",
    "get_default_jieba_dict_dir",
+    "io_backend_type",
+    "io_backend_description",
    # Core classes
    "Collection",
    "Doc",
@@ -204,6 +194,7 @@ __all__ = [
    "QwenReRanker",
    # Typing
    "DataType",
+    "IOBackendType",
    "MetricType",
    "QuantizeType",
    "IndexType",
@@ -213,14 +204,6 @@ __all__ = [
    "StatusCode",
    # Tools
    "require_module",
-    # DiskAnn plugin
-    "load_diskann_plugin",
-    "is_diskann_plugin_loaded",
-    "is_libaio_available",
-    "DISKANN_PLUGIN_OK",
-    "DISKANN_PLUGIN_UNSUPPORTED_PLATFORM",
-    "DISKANN_PLUGIN_LIBAIO_MISSING",
-    "DISKANN_PLUGIN_DLOPEN_FAILED",
 ]

 # ==============================
@@ -40,6 +40,7 @@ from .tool import require_module
 from .typing import (
    DataType,
    IndexType,
+    IOBackendType,
    MetricType,
    QuantizeType,
    Status,
@@ -48,6 +49,22 @@ from .typing import (
 from .typing.enum import LogLevel, LogType
 from .zvec import create_and_open, init, open

+def io_backend_type() -> IOBackendType:
+    """Returns the current I/O backend type for DiskAnn async disk reads
+    as an IOBackendType enum (zvec.typing.IOBackendType).
+    IOBackendType.LIBAIO if libaio is available, IOBackendType.PREAD otherwise."""
+
+def io_backend_description() -> str:
+    """Returns a human-readable description of the current I/O backend.
+    When only pread is available, includes instructions for installing
+    libaio to enable async I/O."""
+
+def set_default_jieba_dict_dir(dir: str) -> None:
+    """Register the process-wide default jieba dict directory."""
+
+def get_default_jieba_dict_dir() -> str:
+    """Read the currently registered default jieba dict directory."""
+
 __all__: list = [
    "AddColumnOption",
    "AlterColumnOption",
@@ -71,6 +88,7 @@ __all__: list = [
    "HnswQueryParam",
    "HnswRabitqIndexParam",
    "HnswRabitqQueryParam",
+    "IOBackendType",
    "IVFIndexParam",
    "IVFQueryParam",
    "IndexOption",
@@ -93,9 +111,13 @@ __all__: list = [
    "VectorSchema",
    "WeightedReRanker",
    "create_and_open",
+    "get_default_jieba_dict_dir",
    "init",
+    "io_backend_description",
+    "io_backend_type",
    "open",
    "require_module",
+    "set_default_jieba_dict_dir",
 ]

 class _Collection:
@@ -13,6 +13,8 @@ __all__: list[str] = [
    "AddColumnOption",
    "AlterColumnOption",
    "CollectionOption",
+    "DiskAnnIndexParam",
+    "DiskAnnQueryParam",
    "FlatIndexParam",
    "FtsIndexParam",
    "FtsQueryParam",
@@ -133,6 +135,124 @@ class CollectionOption:
    @property
    def read_only(self) -> bool: ...

+class DiskAnnIndexParam(VectorIndexParam):
+    """
+
+    Parameters for configuring a DiskAnn index.
+
+    DiskAnn stores compressed vector in memory and high-definition vector on disk. At query time,
+    only compressed vector will be loaded into memory. By this way, search memory at runtime is diminished.
+
+    Attributes:
+        metric_type (MetricType): Distance metric used for similarity computation.
+            Default is ``MetricType.IP`` (inner product).
+        max_degree (int): Maximum out-degree of each node in the Vamana graph.
+            Larger values improve recall at the cost of build time and index size.
+            Clamped to the range [1, 100]. Default is 100.
+        list_size (int): Candidate list size used during graph construction.
+            Larger values improve graph quality and recall at the cost of build time.
+            Clamped to the range [10, 100]. Default is 50.
+        pq_chunk_num (int): Number of PQ chunks used for product-quantizing the
+            in-memory compressed vectors. ``0`` means auto-pick based on dimension.
+            Clamped to the range [1, 1024]. Default is 0.
+        quantize_type (QuantizeType): Optional quantization type for vector
+            compression (e.g., FP16, INT8). Default is ``QuantizeType.UNDEFINED``.
+
+    Examples:
+        >>> from zvec.typing import MetricType, QuantizeType
+        >>> params = DiskAnnIndexParam(
+        ...     metric_type=MetricType.COSINE,
+        ...     max_degree=100,
+        ...     list_size=50,
+        ...     pq_chunk_num=8,
+        ...     quantize_type=QuantizeType.FP16
+        ... )
+        >>> print(params.max_degree)
+        100
+    """
+
+    def __getstate__(self) -> tuple: ...
+    def __init__(
+        self,
+        metric_type: zvec._zvec.typing.MetricType = ...,
+        max_degree: typing.SupportsInt = 100,
+        list_size: typing.SupportsInt = 50,
+        pq_chunk_num: typing.SupportsInt = 0,
+        quantize_type: zvec._zvec.typing.QuantizeType = ...,
+        quantizer_param: QuantizerParam = ...,
+    ) -> None:
+        """
+
+        Constructs a DiskAnnIndexParam instance.
+
+        Args:
+            metric_type (MetricType, optional): Distance metric. Defaults to MetricType.IP.
+            max_degree (int, optional): Maximum out-degree of each node in the Vamana
+                graph. Clamped to [1, 100]. Defaults to 100.
+            list_size (int, optional): Candidate list size used during graph
+                construction. Clamped to [10, 100]. Defaults to 50.
+            pq_chunk_num (int, optional): Number of PQ chunks for product
+                quantization. ``0`` means auto-pick based on dimension.
+                Clamped to [1, 1024]. Defaults to 0.
+            quantize_type (QuantizeType, optional): Vector quantization type.
+                Defaults to QuantizeType.UNDEFINED.
+            quantizer_param (QuantizerParam, optional): Quantizer configuration.
+                Defaults to QuantizerParam().
+        """
+
+    def __repr__(self) -> str: ...
+    def __setstate__(self, arg0: tuple) -> None: ...
+    def to_dict(self) -> dict:
+        """
+        Convert to dictionary with all fields
+        """
+
+    @property
+    def max_degree(self) -> int:
+        """int: Maximum out-degree of each node in the Vamana graph."""
+
+    @property
+    def list_size(self) -> int:
+        """int: Candidate list size used during graph construction."""
+
+    @property
+    def pq_chunk_num(self) -> int:
+        """int: Number of PQ chunks for product quantization."""
+
+class DiskAnnQueryParam(QueryParam):
+    """
+
+    Query parameters for DiskAnn index.
+
+    Attributes:
+        type (IndexType): Always ``IndexType.DISKANN``.
+        list_size (int): Beam-search candidate list size used at query time.
+            Higher values improve recall but increase latency. Default is 300.
+
+    Examples:
+        >>> params = DiskAnnQueryParam(list_size=20)
+        >>> print(params.list_size)
+        20
+    """
+
+    def __getstate__(self) -> tuple: ...
+    def __init__(self, list_size: typing.SupportsInt = 300) -> None:
+        """
+
+        Constructs a DiskAnnQueryParam instance.
+
+        Args:
+            list_size (int, optional): Beam-search candidate list size during
+                graph search. Higher values improve recall at the cost of latency.
+                Defaults to 300.
+        """
+
+    def __repr__(self) -> str: ...
+    def __setstate__(self, arg0: tuple) -> None: ...
+    @property
+    def list_size(self) -> int:
+        """int: Beam-search candidate list size during DiskAnn query."""
+
 class FlatIndexParam(VectorIndexParam):
    """

@@ -16,6 +16,7 @@ from __future__ import annotations
 from zvec._zvec.typing import (
    DataType,
    IndexType,
+    IOBackendType,
    MetricType,
    QuantizeType,
    Status,
@@ -24,6 +25,7 @@ from zvec._zvec.typing import (

 __all__ = [
    "DataType",
+    "IOBackendType",
    "IndexType",
    "MetricType",
    "QuantizeType",
@@ -8,6 +8,7 @@ import typing

 __all__: list[str] = [
    "DataType",
+    "IOBackendType",
    "IndexType",
    "MetricType",
    "QuantizeType",
@@ -122,6 +123,48 @@ class DataType:
    @property
    def value(self) -> int: ...

+class IOBackendType:
+    """
+
+    Enumeration of supported I/O backend types for DiskAnn async disk reads.
+
+    - PREAD: Synchronous pread() — no async I/O.
+    - LIBAIO: libaio loaded at runtime via dlopen().
+
+    Examples:
+        >>> from zvec.typing import IOBackendType
+        >>> print(IOBackendType.LIBAIO)
+        IOBackendType.LIBAIO
+
+
+    Members:
+
+      PREAD
+
+      LIBAIO
+    """
+
+    LIBAIO: typing.ClassVar[IOBackendType]  # value = <IOBackendType.LIBAIO: 1>
+    PREAD: typing.ClassVar[IOBackendType]  # value = <IOBackendType.PREAD: 0>
+    __members__: typing.ClassVar[
+        dict[str, IOBackendType]
+    ]  # value = {'PREAD': <IOBackendType.PREAD: 0>, 'LIBAIO': <IOBackendType.LIBAIO: 1>}
+
+    def __eq__(self, other: typing.Any) -> bool: ...
+    def __getstate__(self) -> int: ...
+    def __hash__(self) -> int: ...
+    def __index__(self) -> int: ...
+    def __init__(self, value: typing.SupportsInt) -> None: ...
+    def __int__(self) -> int: ...
+    def __ne__(self, other: typing.Any) -> bool: ...
+    def __repr__(self) -> str: ...
+    def __setstate__(self, state: typing.SupportsInt) -> None: ...
+    def __str__(self) -> str: ...
+    @property
+    def name(self) -> str: ...
+    @property
+    def value(self) -> int: ...
+
 class IndexType:
    """

@@ -143,17 +186,29 @@ class IndexType:

      FLAT

+      HNSW_RABITQ
+
+      DISKANN
+
+      VAMANA
+
      INVERT
+
+      FTS
    """

-    FLAT: typing.ClassVar[IndexType]  # value = <IndexType.FLAT: 4>
+    DISKANN: typing.ClassVar[IndexType]  # value = <IndexType.DISKANN: 5>
+    FLAT: typing.ClassVar[IndexType]  # value = <IndexType.FLAT: 3>
+    FTS: typing.ClassVar[IndexType]  # value = <IndexType.FTS: 11>
    HNSW: typing.ClassVar[IndexType]  # value = <IndexType.HNSW: 1>
+    HNSW_RABITQ: typing.ClassVar[IndexType]  # value = <IndexType.HNSW_RABITQ: 4>
    INVERT: typing.ClassVar[IndexType]  # value = <IndexType.INVERT: 10>
-    IVF: typing.ClassVar[IndexType]  # value = <IndexType.IVF: 3>
+    IVF: typing.ClassVar[IndexType]  # value = <IndexType.IVF: 2>
    UNDEFINED: typing.ClassVar[IndexType]  # value = <IndexType.UNDEFINED: 0>
+    VAMANA: typing.ClassVar[IndexType]  # value = <IndexType.VAMANA: 6>
    __members__: typing.ClassVar[
        dict[str, IndexType]
-    ]  # value = {'UNDEFINED': <IndexType.UNDEFINED: 0>, 'HNSW': <IndexType.HNSW: 1>, 'IVF': <IndexType.IVF: 3>, 'FLAT': <IndexType.FLAT: 4>, 'INVERT': <IndexType.INVERT: 10>}
+    ]  # value = {'UNDEFINED': <IndexType.UNDEFINED: 0>, 'HNSW': <IndexType.HNSW: 1>, 'IVF': <IndexType.IVF: 2>, 'FLAT': <IndexType.FLAT: 3>, 'HNSW_RABITQ': <IndexType.HNSW_RABITQ: 4>, 'DISKANN': <IndexType.DISKANN: 5>, 'VAMANA': <IndexType.VAMANA: 6>, 'INVERT': <IndexType.INVERT: 10>, 'FTS': <IndexType.FTS: 11>}

    def __eq__(self, other: typing.Any) -> bool: ...
    def __getstate__(self) -> int: ...
@@ -236,15 +291,18 @@ class QuantizeType:
      INT8

      INT4
+
+      RABITQ
    """

    FP16: typing.ClassVar[QuantizeType]  # value = <QuantizeType.FP16: 1>
    INT4: typing.ClassVar[QuantizeType]  # value = <QuantizeType.INT4: 3>
    INT8: typing.ClassVar[QuantizeType]  # value = <QuantizeType.INT8: 2>
+    RABITQ: typing.ClassVar[QuantizeType]  # value = <QuantizeType.RABITQ: 4>
    UNDEFINED: typing.ClassVar[QuantizeType]  # value = <QuantizeType.UNDEFINED: 0>
    __members__: typing.ClassVar[
        dict[str, QuantizeType]
-    ]  # value = {'UNDEFINED': <QuantizeType.UNDEFINED: 0>, 'FP16': <QuantizeType.FP16: 1>, 'INT8': <QuantizeType.INT8: 2>, 'INT4': <QuantizeType.INT4: 3>}
+    ]  # value = {'UNDEFINED': <QuantizeType.UNDEFINED: 0>, 'FP16': <QuantizeType.FP16: 1>, 'INT8': <QuantizeType.INT8: 2>, 'INT4': <QuantizeType.INT4: 3>, 'RABITQ': <QuantizeType.RABITQ: 4>}

    def __eq__(self, other: typing.Any) -> bool: ...
    def __getstate__(self) -> int: ...
@@ -0,0 +1,39 @@
+// Copyright 2025-present the zvec project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Implementation of the convenience helpers declared in the public header
+// zvec/ailego/io/io_backend.h.
+//
+// This translation unit is the single place that bridges the dependency-free
+// public header to the internal IOBackend singleton, so that public headers
+// can expose current_io_backend_type() / current_io_backend_description()
+// without pulling in libaio_loader or io_backend_def.h.
+
+#include <ailego/io/io_backend_def.h>
+#include <zvec/ailego/io/io_backend.h>
+
+namespace zvec {
+namespace ailego {
+
+IOBackendType current_io_backend_type() {
+  return IOBackend::Instance().available();
+}
+
+std::string current_io_backend_description() {
+  auto type = IOBackend::Instance().available();
+  return IOBackendDescription(type);
+}
+
+}  // namespace ailego
+}  // namespace zvec
@@ -0,0 +1,137 @@
+// Copyright 2025-present the zvec project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Abstract I/O backend selector.
+//
+// Wraps the low-level loaders (LibAioLoader for libaio) and provides a uniform
+// way to initialize, query, and report the active I/O backend.  The actual I/O
+// operations are still performed by the underlying loaders; this class is
+// responsible only for backend initialization and reporting.
+//
+// When no async backend is available, the caller should fall back to
+// synchronous pread().
+//
+// Usage:
+//   auto& backend = ailego::IOBackend::Instance();
+//   if (!backend.is_pread()) { ... }
+//   LOG_INFO("I/O backend: %s", backend.name());
+
+#pragma once
+
+#include <ailego/io/libaio_loader.h>
+#include <zvec/ailego/io/io_backend.h>
+
+namespace zvec {
+namespace ailego {
+
+// Returns a human-readable name for the given backend type.
+inline const char *IOBackendTypeName(IOBackendType type) {
+  switch (type) {
+    case IOBackendType::kLibAio:
+      return "libaio";
+    case IOBackendType::kPread:
+      return "pread";
+  }
+  return "unknown";
+}
+
+// Returns a human-readable description for the given backend type.
+// When the backend is kPread, includes installation guidance for libaio.
+inline const char *IOBackendDescription(IOBackendType type) {
+  switch (type) {
+    case IOBackendType::kLibAio:
+      return "libaio async I/O backend loaded at runtime via dlopen().";
+    case IOBackendType::kPread:
+      return "No async I/O backend available. Install libaio (e.g. "
+             "'apt-get install libaio1', or 'libaio1t64' on Ubuntu 24.04+) "
+             "and retry. DiskAnn will fall back to synchronous pread() \u2014 "
+             "performance will be degraded.";
+  }
+  return "Unknown I/O backend.";
+}
+
+// Singleton that loads and queries an I/O backend on demand.
+//
+// available() (no arg) tries the best backend with priority (libaio > pread)
+// and returns the loaded backend type.
+// available(IOBackendType) tries a specific backend.
+// Use type() / name() to query the loaded backend without triggering a load.
+class IOBackend {
+ public:
+  static IOBackend &Instance() {
+    static IOBackend instance;
+    return instance;
+  }
+
+  // Try to load the best available backend (libaio > pread).
+  // Returns the loaded backend type.
+  // Idempotent — if already loaded, returns immediately.
+  IOBackendType available() {
+    if (type_ != IOBackendType::kPread) {
+      return type_;
+    }
+    return available(IOBackendType::kLibAio);
+  }
+
+  // Try to load the requested backend.  Returns the loaded backend type
+  // (may differ from requested if the load failed — falls back to kPread).
+  // Idempotent — if the same backend is already loaded, returns immediately.
+  IOBackendType available(IOBackendType requested) {
+    if (type_ == requested && type_ != IOBackendType::kPread) {
+      return type_;
+    }
+#if defined(__linux) || defined(__linux__)
+    if (requested == IOBackendType::kLibAio) {
+      if (LibAioLoader::Instance().load() &&
+          LibAioLoader::Instance().is_available()) {
+        type_ = IOBackendType::kLibAio;
+        return type_;
+      }
+    }
+#endif
+    type_ = IOBackendType::kPread;
+    return type_;
+  }
+
+  bool is_pread() {
+    return available() == IOBackendType::kPread;
+  }
+
+  bool is_libaio() {
+    return available() == IOBackendType::kLibAio;
+  }
+
+  // Returns the loaded backend type.
+  IOBackendType type() const {
+    return type_;
+  }
+
+  // Human-readable name for the selected backend.
+  const char *name() const {
+    return IOBackendTypeName(type_);
+  }
+
+  // Human-readable description for the selected backend.
+  const char *description() const {
+    return IOBackendDescription(type_);
+  }
+
+ private:
+  IOBackend() = default;
+
+  IOBackendType type_{IOBackendType::kPread};
+};
+
+}  // namespace ailego
+}  // namespace zvec
@@ -0,0 +1,190 @@
+// Copyright 2025-present the zvec project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Private replacement for <libaio.h>.
+//
+// This header declares *only* the types, constants, and inline helpers that
+// zvec needs from libaio.  By doing so the project is completely decoupled
+// from the system libaio-dev header: there is no `#include <libaio.h>` anywhere
+// in the source tree, which means libaio-dev does not need to be installed at
+// build time and the code is portable to cross-compilation environments that
+// lack the header.
+//
+// The struct layouts (struct iocb, struct io_event, ...) are part of the Linux
+// kernel ABI.  They are copied verbatim from the upstream <libaio.h>, including
+// the PADDED macros that handle architecture-specific padding.  The inline
+// helper io_prep_pread() is likewise copied — it only manipulates struct fields
+// and does not call into the library.
+
+#pragma once
+
+#include <time.h>   // struct timespec (used by io_getevents signature)
+#include <cstring>  // memset() — used by io_prep_pread() inline helper
+
+#if defined(__linux) || defined(__linux__)
+
+struct sockaddr;
+struct iovec;
+
+// ---------------------------------------------------------------------------
+// Type and struct definitions copied from <libaio.h>
+// ---------------------------------------------------------------------------
+
+typedef struct io_context *io_context_t;
+
+typedef enum io_iocb_cmd {
+  IO_CMD_PREAD = 0,
+  IO_CMD_PWRITE = 1,
+  IO_CMD_FSYNC = 2,
+  IO_CMD_FDSYNC = 3,
+  IO_CMD_POLL = 5,
+  IO_CMD_NOOP = 6,
+  IO_CMD_PREADV = 7,
+  IO_CMD_PWRITEV = 8,
+} io_iocb_cmd_t;
+
+// PADDED macros — copied verbatim from <libaio.h> to guarantee ABI-compatible
+// struct layout on every supported architecture.
+
+/* little endian, 32 bits */
+#if defined(__i386__) || (defined(__x86_64__) && defined(__ILP32__)) ||     \
+    (defined(__arm__) && !defined(__ARMEB__)) ||                            \
+    (defined(__sh__) && defined(__LITTLE_ENDIAN__)) || defined(__bfin__) || \
+    (defined(__MIPSEL__) && !defined(__mips64)) || defined(__cris__) ||     \
+    defined(__loongarch32) || (defined(__riscv) && __riscv_xlen == 32) ||   \
+    (defined(__GNUC__) && defined(__BYTE_ORDER__) &&                        \
+     __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ && __SIZEOF_LONG__ == 4)
+#define AIO_PADDED(x, y) \
+  x;                     \
+  unsigned y
+#define AIO_PADDEDptr(x, y) \
+  x;                        \
+  unsigned y
+#define AIO_PADDEDul(x, y) \
+  unsigned long x;         \
+  unsigned y
+
+/* little endian, 64 bits */
+#elif defined(__ia64__) || defined(__x86_64__) || defined(__alpha__) ||   \
+    (defined(__mips64) && defined(__MIPSEL__)) ||                         \
+    (defined(__aarch64__) && defined(__AARCH64EL__)) ||                   \
+    defined(__loongarch64) || (defined(__riscv) && __riscv_xlen == 64) || \
+    (defined(__GNUC__) && defined(__BYTE_ORDER__) &&                      \
+     __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ && __SIZEOF_LONG__ == 8)
+#define AIO_PADDED(x, y) x, y
+#define AIO_PADDEDptr(x, y) x
+#define AIO_PADDEDul(x, y) unsigned long x
+
+/* big endian, 64 bits */
+#elif defined(__powerpc64__) || defined(__s390x__) ||   \
+    (defined(__hppa__) && defined(__arch64__)) ||       \
+    (defined(__sparc__) && defined(__arch64__)) ||      \
+    (defined(__mips64) && defined(__MIPSEB__)) ||       \
+    (defined(__aarch64__) && defined(__AARCH64EB__)) || \
+    (defined(__GNUC__) && defined(__BYTE_ORDER__) &&    \
+     __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ && __SIZEOF_LONG__ == 8)
+#define AIO_PADDED(x, y) \
+  unsigned y;            \
+  x
+#define AIO_PADDEDptr(x, y) x
+#define AIO_PADDEDul(x, y) unsigned long x
+
+/* big endian, 32 bits */
+#elif defined(__PPC__) || defined(__s390__) ||                            \
+    (defined(__arm__) && defined(__ARMEB__)) ||                           \
+    (defined(__sh__) && defined(__BIG_ENDIAN__)) || defined(__sparc__) || \
+    defined(__MIPSEB__) || defined(__m68k__) || defined(__hppa__) ||      \
+    defined(__frv__) || defined(__avr32__) ||                             \
+    (defined(__GNUC__) && defined(__BYTE_ORDER__) &&                      \
+     __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ && __SIZEOF_LONG__ == 4)
+#define AIO_PADDED(x, y) \
+  unsigned y;            \
+  x
+#define AIO_PADDEDptr(x, y) \
+  unsigned y;               \
+  x
+#define AIO_PADDEDul(x, y) \
+  unsigned y;              \
+  unsigned long x
+
+#else
+#error endianness?
+#endif
+
+struct io_iocb_poll {
+  AIO_PADDED(int events, __pad1);
+};
+
+struct io_iocb_sockaddr {
+  AIO_PADDEDptr(struct sockaddr *addr, __pad1);
+  AIO_PADDEDul(len, __pad2);
+};
+
+struct io_iocb_common {
+  AIO_PADDEDptr(void *buf, __pad1);
+  AIO_PADDEDul(nbytes, __pad2);
+  long long offset;
+  long long __pad3;
+  unsigned flags;
+  unsigned resfd;
+};
+
+struct io_iocb_vector {
+  AIO_PADDEDptr(const struct iovec *vec, __pad1);
+  AIO_PADDEDul(nr, __pad2);
+  long long offset;
+};
+
+struct iocb {
+  AIO_PADDEDptr(void *data, __pad1);
+  AIO_PADDED(unsigned key, aio_rw_flags);
+  short aio_lio_opcode;
+  short aio_reqprio;
+  int aio_fildes;
+  union {
+    struct io_iocb_common c;
+    struct io_iocb_vector v;
+    struct io_iocb_poll poll;
+    struct io_iocb_sockaddr saddr;
+  } u;
+};
+
+struct io_event {
+  AIO_PADDEDptr(void *data, __pad1);
+  AIO_PADDEDptr(struct iocb *obj, __pad2);
+  AIO_PADDEDul(res, __pad3);
+  AIO_PADDEDul(res2, __pad4);
+};
+
+#undef AIO_PADDED
+#undef AIO_PADDEDptr
+#undef AIO_PADDEDul
+
+// Inline helper — copied from <libaio.h>.  Only manipulates struct fields.
+static inline void io_prep_pread(struct iocb *iocb, int fd, void *buf,
+                                 size_t count, long long offset) {
+  memset(iocb, 0, sizeof(*iocb));
+  iocb->aio_fildes = fd;
+  iocb->aio_lio_opcode = IO_CMD_PREAD;
+  iocb->aio_reqprio = 0;
+  iocb->u.c.buf = buf;
+  iocb->u.c.nbytes = count;
+  iocb->u.c.offset = offset;
+}
+
+// ---------------------------------------------------------------------------
+// End: type and struct definitions from <libaio.h>
+// ---------------------------------------------------------------------------
+
+#endif  // __linux__
@@ -0,0 +1,144 @@
+// Copyright 2025-present the zvec project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// dlopen-based wrapper for libaio.  Instead of linking against -laio at build
+// time, the DiskAnn plugin loads libaio at runtime via dlopen()/dlsym().  This
+// removes libaio as a hard build- and load-time dependency: the plugin .so no
+// longer carries a NEEDED entry for libaio.so.1, so it can be dlopen'ed on
+// hosts that don't have libaio installed.  Callers that actually exercise the
+// async-I/O path will fall back to synchronous pread() when libaio is absent.
+//
+// All ABI-stable type and struct definitions (struct iocb, struct io_event,
+// io_context_t, PADDED macros, io_prep_pread(), ...) now live in libaio_def.h —
+// a private header that replaces <libaio.h> so the project has zero build-time
+// dependency on libaio-dev.
+
+#pragma once
+
+#if defined(__linux) || defined(__linux__)
+
+#include <dlfcn.h>
+#include <atomic>
+#include <cstring>
+#include <mutex>
+#include <ailego/io/libaio_def.h>  // ABI-stable struct definitions (replaces <libaio.h>)
+
+// Function-pointer typedefs for the four libaio syscalls used by DiskAnn.
+typedef int (*aio_setup_fn)(int maxevents, io_context_t *ctxp);
+typedef int (*aio_destroy_fn)(io_context_t ctx);
+typedef int (*aio_submit_fn)(io_context_t ctx, long nr, struct iocb *ios[]);
+typedef int (*aio_getevents_fn)(io_context_t ctx, long min_nr, long nr,
+                                struct io_event *events,
+                                struct timespec *timeout);
+
+// Runtime loader for libaio.  Thread-safe singleton that dlopen()'s libaio
+// once and caches the function pointers.  If libaio is not present on the
+// host, all pointers remain nullptr and callers should fall back to
+// synchronous I/O (pread).
+//
+// Usage:
+//   if (LibAioLoader::Instance().load()) {
+//     LibAioLoader::Instance().io_setup(...);
+//   }
+class LibAioLoader {
+ public:
+  static LibAioLoader &Instance() {
+    static LibAioLoader instance;
+    return instance;
+  }
+
+  // Load (or confirm already loaded) libaio.  Returns true on success.
+  // Thread-safe and idempotent.
+  bool load() {
+    if (available_.load(std::memory_order_acquire)) {
+      return true;
+    }
+    std::call_once(once_, [this] { this->try_load(); });
+    return available_.load(std::memory_order_relaxed);
+  }
+
+  bool is_available() const {
+    return available_.load(std::memory_order_acquire);
+  }
+
+  // Function pointers — nullptr until load() succeeds.
+  aio_setup_fn io_setup;
+  aio_destroy_fn io_destroy;
+  aio_submit_fn io_submit;
+  aio_getevents_fn io_getevents;
+
+ private:
+  LibAioLoader()
+      : io_setup(nullptr),
+        io_destroy(nullptr),
+        io_submit(nullptr),
+        io_getevents(nullptr) {}
+
+  ~LibAioLoader() {
+    if (handle_ != nullptr) {
+      dlclose(handle_);
+    }
+  }
+
+  LibAioLoader(const LibAioLoader &) = delete;
+  LibAioLoader &operator=(const LibAioLoader &) = delete;
+
+  void try_load() {
+    // On Ubuntu 24.04 the libaio package was renamed with the t64 suffix
+    // (64-bit time_t transition), so probe both spellings.
+    static constexpr const char *kSonames[] = {
+        "libaio.so.1",
+        "libaio.so.1t64",
+    };
+
+    for (const char *soname : kSonames) {
+      void *h = dlopen(soname, RTLD_LAZY);
+      if (h == nullptr) {
+        continue;
+      }
+
+      io_setup = reinterpret_cast<aio_setup_fn>(dlsym(h, "io_setup"));
+      io_destroy = reinterpret_cast<aio_destroy_fn>(dlsym(h, "io_destroy"));
+      io_submit = reinterpret_cast<aio_submit_fn>(dlsym(h, "io_submit"));
+
+      // io_getevents may be redirected to io_getevents_time64 on 32-bit
+      // platforms compiled with _TIME_BITS=64.
+      io_getevents =
+          reinterpret_cast<aio_getevents_fn>(dlsym(h, "io_getevents"));
+      if (io_getevents == nullptr) {
+        io_getevents =
+            reinterpret_cast<aio_getevents_fn>(dlsym(h, "io_getevents_time64"));
+      }
+
+      if (io_setup && io_destroy && io_submit && io_getevents) {
+        handle_ = h;
+        available_.store(true, std::memory_order_release);
+        return;
+      }
+
+      // Some symbols missing — try the next soname.
+      dlclose(h);
+      io_setup = nullptr;
+      io_destroy = nullptr;
+      io_submit = nullptr;
+      io_getevents = nullptr;
+    }
+  }
+
+  std::once_flag once_;
+  std::atomic<bool> available_{false};
+  void *handle_{nullptr};
+};
+
+#endif  // __linux__
@@ -29,6 +29,8 @@
 #include <string>
 #include <unordered_map>
 #include <vector>
+#include <ailego/io/io_backend_def.h>
+#include <zvec/ailego/io/io_backend.h>
 #include <zvec/db/collection.h>
 #include <zvec/db/config.h>
 #include <zvec/db/doc.h>
@@ -759,6 +761,25 @@ const char *zvec_get_default_jieba_dict_dir(void) {
  return cached.c_str();
 }

+// =============================================================================
+// I/O Backend Introspection
+// =============================================================================
+
+zvec_io_backend_type_t zvec_get_io_backend_type(void) {
+  auto type = zvec::ailego::current_io_backend_type();
+  return static_cast<zvec_io_backend_type_t>(static_cast<uint32_t>(type));
+}
+
+const char *zvec_get_io_backend_type_name(zvec_io_backend_type_t type) {
+  auto cpp_type = static_cast<zvec::ailego::IOBackendType>(type);
+  return zvec::ailego::IOBackendTypeName(cpp_type);
+}
+
+const char *zvec_get_io_backend_description(void) {
+  auto type = zvec::ailego::current_io_backend_type();
+  return zvec::ailego::IOBackendDescription(type);
+}
+
 // =============================================================================
 // Error handling interface implementation
 // =============================================================================
@@ -2800,12 +2821,16 @@ const char *zvec_index_type_to_string(zvec_index_type_t index_type) {
      return "IVF";
    case ZVEC_INDEX_TYPE_FLAT:
      return "FLAT";
+    case ZVEC_INDEX_TYPE_HNSW_RABITQ:
+      return "HNSW_RABITQ";
+    case ZVEC_INDEX_TYPE_DISKANN:
+      return "DISKANN";
+    case ZVEC_INDEX_TYPE_VAMANA:
+      return "VAMANA";
    case ZVEC_INDEX_TYPE_INVERT:
      return "INVERT";
    case ZVEC_INDEX_TYPE_FTS:
      return "FTS";
-    case ZVEC_INDEX_TYPE_DISKANN:
-      return "DiskANN";
    default:
      return "UNKNOWN_INDEX_TYPE";
  }
@@ -19,21 +19,6 @@ set(SRC_LISTS

 pybind11_add_module(_zvec ${SRC_LISTS})

-# pybind11_add_module() defaults to CXX_VISIBILITY_PRESET=hidden +
-# VISIBILITY_INLINES_HIDDEN=ON, which hides the compiler-generated helper
-# symbols attached to inline functions (guard variables for static locals,
-# vtables, typeinfo ...). The DiskAnn runtime plugin has its own copy of
-# Factory<IndexStreamer>::Instance()'s guard variable; if _zvec.so's copy
-# is hidden, the two guards are separate and the factory constructor runs
-# twice during plugin load, wiping out the registrations that happened
-# during _zvec.so import. We switch to default visibility here and rely on
-# the version script (exports.map / exports.mac) to keep the dynamic
-# symbol table small by exporting only zvec::* and PyInit_*.
-set_target_properties(_zvec PROPERTIES
-        CXX_VISIBILITY_PRESET default
-        C_VISIBILITY_PRESET default
-        VISIBILITY_INLINES_HIDDEN OFF)
-
 # Ensure any change to the linker version script (exports.map) triggers a
 # re-link of _zvec.so. target_link_options() alone is a command-line flag
 # and does not register the script file as a build dependency, so stale
@@ -57,11 +42,11 @@ if (CMAKE_SYSTEM_NAME STREQUAL "Linux")
            $<TARGET_FILE:core_knn_ivf_static>
            $<TARGET_FILE:core_knn_vamana_static>
            $<TARGET_FILE:core_knn_cluster_static>
+            $<TARGET_FILE:core_knn_diskann_static>
            $<TARGET_FILE:core_mix_reducer_static>
            $<TARGET_FILE:core_metric_static>
            $<TARGET_FILE:core_utility_static>
            $<TARGET_FILE:core_quantizer_static>
-            $<TARGET_FILE:core_plugin>
            -Wl,--no-whole-archive
            zvec
            ${CMAKE_DL_LIBS}
@@ -69,21 +54,11 @@ if (CMAKE_SYSTEM_NAME STREQUAL "Linux")
    target_link_options(_zvec PRIVATE
            "LINKER:--version-script=${CMAKE_CURRENT_SOURCE_DIR}/exports.map"
    )
-    # DiskAnn is x86-only (it depends on libaio, unavailable on ARM64), so the
-    # runtime plugin (libzvec_diskann_plugin.so) is only produced on non-ARM
-    # builds. It is shipped as a runtime-loaded shared module and brought up
-    # implicitly the first time a DiskAnn index is created — users never need to
-    # call any load function. If libaio is missing at runtime the auto-load
-    # fails cleanly and the error is surfaced only when DiskAnn is actually
-    # used; other index types (HNSW/IVF/Flat/Vamana) remain fully functional.
-    # The .so must therefore be discoverable next to the extension module,
-    # hence the $ORIGIN rpath below.
-    if (NOT CMAKE_SYSTEM_PROCESSOR MATCHES "aarch64|arm64|arm")
-        set_target_properties(_zvec PROPERTIES
-                BUILD_RPATH "$ORIGIN"
-                INSTALL_RPATH "$ORIGIN"
-        )
-    endif()
+    # DiskAnn is now statically linked into _zvec.so via --whole-archive, so
+    # no separate runtime .so is shipped in the wheel. libaio is still loaded
+    # at runtime via dlopen() (see libaio_loader.h); if it is missing, DiskAnn
+    # fails cleanly with an actionable error while other index types
+    # (HNSW/IVF/Flat/Vamana) remain fully functional.
 elseif (APPLE)
    target_link_libraries(_zvec PRIVATE
            -Wl,-force_load,$<TARGET_FILE:core_knn_flat_static>
@@ -94,11 +69,11 @@ elseif (APPLE)
            -Wl,-force_load,$<TARGET_FILE:core_knn_ivf_static>
            -Wl,-force_load,$<TARGET_FILE:core_knn_vamana_static>
            -Wl,-force_load,$<TARGET_FILE:core_knn_cluster_static>
+            -Wl,-force_load,$<TARGET_FILE:core_knn_diskann_static>
            -Wl,-force_load,$<TARGET_FILE:core_mix_reducer_static>
            -Wl,-force_load,$<TARGET_FILE:core_metric_static>
            -Wl,-force_load,$<TARGET_FILE:core_utility_static>
            -Wl,-force_load,$<TARGET_FILE:core_quantizer_static>
-            -Wl,-force_load,$<TARGET_FILE:core_plugin>
            zvec
    )
    target_link_libraries(_zvec PRIVATE
@@ -113,11 +88,11 @@ elseif (MSVC)
            core_knn_ivf_static
            core_knn_vamana_static
            core_knn_cluster_static
+            core_knn_diskann_static
            core_mix_reducer_static
            core_metric_static
            core_utility_static
            core_quantizer_static
-            core_plugin
    )
    target_link_libraries(_zvec PRIVATE
            ${_zvec_whole_archive_libs}
@@ -13,7 +13,6 @@
 // limitations under the License.

 #include <pybind11/pybind11.h>
-#include <zvec/plugin/diskann_plugin.h>
 #include "python_collection.h"
 #include "python_config.h"
 #include "python_doc.h"
@@ -24,39 +23,6 @@

 namespace zvec {

-namespace {
-
-// Expose DiskAnn plugin management to Python. The DiskAnn runtime normally
-// auto-loads on first use, but tests (and diagnostic tooling) need a way to
-// force a load up-front and get actionable errors when libaio is missing or
-// the plugin shared object cannot be located.
-void InitializeDiskAnnPluginBindings(pybind11::module_ &m) {
-  m.def(
-      "load_diskann_plugin",
-      [](const std::string &path) { return ::zvec::LoadDiskAnnPlugin(path); },
-      pybind11::arg("path") = std::string(),
-      "Load the DiskAnn runtime plugin. Returns 0 on success or a negative "
-      "DiskAnnPluginStatus code on failure (unsupported platform, libaio "
-      "missing, or dlopen failure).");
-  m.def("is_diskann_plugin_loaded", &::zvec::IsDiskAnnPluginLoaded,
-        "Return True if the DiskAnn runtime plugin is currently loaded.");
-  m.def("is_libaio_available", &::zvec::IsLibAioAvailable,
-        "Return True if libaio is resolvable on this host (required by the "
-        "DiskAnn runtime).");
-
-  // Status constants so callers can compare against well-known codes without
-  // hard-coding integers.
-  m.attr("DISKANN_PLUGIN_OK") = static_cast<int>(::zvec::kDiskAnnPluginOk);
-  m.attr("DISKANN_PLUGIN_UNSUPPORTED_PLATFORM") =
-      static_cast<int>(::zvec::kDiskAnnPluginUnsupportedPlatform);
-  m.attr("DISKANN_PLUGIN_LIBAIO_MISSING") =
-      static_cast<int>(::zvec::kDiskAnnPluginLibAioMissing);
-  m.attr("DISKANN_PLUGIN_DLOPEN_FAILED") =
-      static_cast<int>(::zvec::kDiskAnnPluginDlopenFailed);
-}
-
-}  // namespace
-
 PYBIND11_MODULE(_zvec, m) {
  m.doc() = "Zvec core module";

@@ -67,6 +33,5 @@ PYBIND11_MODULE(_zvec, m) {
  ZVecPyConfig::Initialize(m);
  ZVecPyDoc::Initialize(m);
  ZVecPyCollection::Initialize(m);
-  InitializeDiskAnnPluginBindings(m);
 }
 }  // namespace zvec
@@ -1,34 +1,6 @@
 {
    global:
-        # Python module entry point(s).
-        PyInit_*;
-
-        # Expose the full zvec C++ namespace so the DiskAnn runtime plugin
-        # (libzvec_diskann_plugin.so), which is dlopen()ed with
-        # RTLD_NOW | RTLD_GLOBAL after the interpreter has loaded _zvec.so,
-        # can resolve its undefined references against this module. Without
-        # this, the plugin fails to load with errors like
-        #   undefined symbol: _ZN4zvec6ailego6Logger10LEVEL_INFOE
-        # because the default version script hides every internal symbol.
-        extern "C++" {
-            "zvec::*";
-            zvec::*;
-            # Also export the compiler-generated helper symbols that live
-            # alongside symbols in the zvec namespace (guard variables for
-            # static locals, vtables, typeinfo, VTT, construction vtables,
-            # thunks). Without these, the DiskAnn plugin and _zvec.so each
-            # get their own copy of e.g. the guard for Factory<T>::Instance's
-            # static local, which causes the factory constructor to run
-            # twice - wiping out registrations done during _zvec.so load.
-            "guard variable for zvec::*";
-            "vtable for zvec::*";
-            "VTT for zvec::*";
-            "typeinfo for zvec::*";
-            "typeinfo name for zvec::*";
-            "construction vtable for zvec::*";
-            "non-virtual thunk to zvec::*";
-            "virtual thunk to zvec::*";
-        };
+        PyInit_*;  # export only python related functions
    local:
        *;
 };
@@ -10,9 +10,12 @@
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
-// limitations under the License.#pragma once
+// limitations under the License.
+
+#pragma once

 #include <pybind11/pybind11.h>
+#include <zvec/ailego/io/io_backend.h>
 #include <zvec/db/status.h>
 #include <zvec/db/type.h>

@@ -32,6 +35,7 @@ class ZVecPyTyping {
  static void bind_index_types(py::module_ &m);
  static void bind_metric_types(py::module_ &m);
  static void bind_quantize_types(py::module_ &m);
+  static void bind_io_backend_types(py::module_ &m);
  static void bind_status(py::module_ &m);
 };

@@ -14,6 +14,7 @@

 #include "python_config.h"
 #include <pybind11/stl.h>
+#include <zvec/ailego/io/io_backend.h>

 namespace zvec {

@@ -217,6 +218,27 @@ void ZVecPyConfig::Initialize(pybind11::module_ &m) {
      "get_default_jieba_dict_dir",
      []() -> std::string { return GlobalConfig::Instance().jieba_dict_dir(); },
      "Read the currently registered default jieba dict directory.");
+
+  // Returns the current I/O backend type for DiskAnn async disk reads.
+  // Pure introspection \u2014 no side effects, no install hints.
+  m.def(
+      "io_backend_type",
+      []() -> ailego::IOBackendType {
+        return ailego::current_io_backend_type();
+      },
+      "Returns the current I/O backend type for DiskAnn async disk reads "
+      "as an IOBackendType enum (zvec.typing.IOBackendType). "
+      "IOBackendType.LIBAIO if libaio is available, "
+      "IOBackendType.PREAD otherwise.");
+
+  // Returns a human-readable description of the I/O backend, including
+  // installation guidance for libaio when only pread is available.
+  m.def(
+      "io_backend_description",
+      []() -> std::string { return ailego::current_io_backend_description(); },
+      "Returns a human-readable description of the current I/O backend. "
+      "When only pread is available, includes instructions for installing "
+      "libaio to enable async I/O.");
 }


@@ -24,6 +24,7 @@ void ZVecPyTyping::Initialize(pybind11::module_ &parent) {
  bind_index_types(m);
  bind_metric_types(m);
  bind_quantize_types(m);
+  bind_io_backend_types(m);
  bind_status(m);
 }

@@ -96,11 +97,13 @@ Examples:
 )pbdoc")
      .value("UNDEFINED", IndexType::UNDEFINED)
      .value("HNSW", IndexType::HNSW)
-      .value("HNSW_RABITQ", IndexType::HNSW_RABITQ)
      .value("IVF", IndexType::IVF)
      .value("FLAT", IndexType::FLAT)
+      .value("HNSW_RABITQ", IndexType::HNSW_RABITQ)
+      .value("DISKANN", IndexType::DISKANN)
      .value("VAMANA", IndexType::VAMANA)
-      .value("INVERT", IndexType::INVERT);
+      .value("INVERT", IndexType::INVERT)
+      .value("FTS", IndexType::FTS);
 }

 void ZVecPyTyping::bind_metric_types(pybind11::module_ &m) {
@@ -137,6 +140,22 @@ Examples:
      .value("RABITQ", QuantizeType::RABITQ);
 }

+void ZVecPyTyping::bind_io_backend_types(py::module_ &m) {
+  py::enum_<ailego::IOBackendType>(m, "IOBackendType", R"pbdoc(
+Enumeration of supported I/O backend types for DiskAnn async disk reads.
+
+- PREAD: Synchronous pread() \u2014 no async I/O.
+- LIBAIO: libaio loaded at runtime via dlopen().
+
+Examples:
+    >>> from zvec.typing import IOBackendType
+    >>> print(IOBackendType.LIBAIO)
+    IOBackendType.LIBAIO
+)pbdoc")
+      .value("PREAD", ailego::IOBackendType::kPread)
+      .value("LIBAIO", ailego::IOBackendType::kLibAio);
+}
+
 void ZVecPyTyping::bind_status(py::module_ &m) {
  // bind status code
  py::enum_<StatusCode>(m, "StatusCode", R"pbdoc(
@@ -49,7 +49,6 @@ cc_directory(quantizer)
 cc_directory(utility)
 cc_directory(interface)
 cc_directory(mixed_reducer)
-cc_directory(plugin)

 git_version(GIT_SRCS_VER ${CMAKE_CURRENT_SOURCE_DIR})
 file(GLOB_RECURSE ALL_CORE_SRCS *.cc *.c *.h)
@@ -63,17 +62,17 @@ endif()

 # Always exclude algorithm/diskann implementation files from zvec_core.
 # The DiskAnn algorithm is provided by the separate core_knn_diskann library
-# (real on Linux x86_64, stub on other platforms). Including them here causes
-# duplicate symbols and missing -laio when test binaries link both zvec_core
-# (via zvec) and core_knn_diskann.
-
+# (STATIC+SHARED, real on Linux x86_64, stub on other platforms). The static
+# variant is whole-archived into _zvec.so for the Python wheel; the shared
+# variant is used by C++ tools and tests. Including the sources here would
+# cause duplicate symbols.
 list(FILTER ALL_CORE_SRCS EXCLUDE REGEX ".*/algorithm/diskann/.*")
 if(NOT DISKANN_SUPPORTED)
  list(FILTER ALL_CORE_SRCS EXCLUDE REGEX ".*/interface/indexes/diskann_index\\.cc")
 endif()

 set(ZVEC_CORE_LIBS zvec_ailego zvec_turbo sparsehash magic_enum rabitqlib)
-# The plugin loader uses dlopen/dlsym, so link libdl on Linux.
+# The DiskAnn runtime loader uses dlopen/dlsym, so link libdl on Linux.
 if(CMAKE_SYSTEM_NAME STREQUAL "Linux")
  list(APPEND ZVEC_CORE_LIBS ${CMAKE_DL_LIBS})
 endif()
@@ -23,7 +23,12 @@ else()

  if(MSVC)
    # MSVC: STATIC-only stub to avoid creating an empty DLL with no exports
-    # (MSVC linker fails to produce an import library when there are zero exports)
+    # (MSVC linker fails to produce an import library when there are zero exports).
+    # cc_library with STATIC-only creates target "core_knn_diskann" but NOT the
+    # "core_knn_diskann_static" variant (that only happens with STATIC+SHARED).
+    # The Python binding references core_knn_diskann_static on all platforms, so
+    # create an ALIAS so the same target name works under MSVC as well.
+    # ($<TARGET_FILE:> supports ALIAS targets since CMake 3.18.)
    cc_library(
        NAME core_knn_diskann
        STATIC STRICT ALWAYS_LINK
@@ -32,6 +37,7 @@ else()
        INCS . ${PROJECT_ROOT_DIR}/src ${PROJECT_ROOT_DIR}/src/core ${PROJECT_ROOT_DIR}/src/core/algorithm
        VERSION "${PROXIMA_ZVEC_VERSION}"
      )
+    add_library(core_knn_diskann_static ALIAS core_knn_diskann)
  else()
    cc_library(
        NAME core_knn_diskann
@@ -1,57 +1,34 @@
 include(${PROJECT_ROOT_DIR}/cmake/bazel.cmake)
+include(${PROJECT_ROOT_DIR}/cmake/option.cmake)

 file(GLOB_RECURSE ALL_SRCS *.cc *.c)

-# The DiskAnn plugin is loaded at runtime via zvec::LoadDiskAnnPlugin() with
-# RTLD_GLOBAL, so its undefined references to internal zvec symbols
-# (core_framework, core_knn_cluster, zvec_ailego, ...) are resolved at load
-# time against the hosting binary (_zvec.so for the Python extension, the
-# test executable for gtest, or libzvec_core for tools).
+# DiskAnn is compiled as a STATIC+SHARED library (matching the pattern used by
+# core_knn_hnsw, core_knn_cluster, etc.). The static variant
+# (core_knn_diskann_static) is whole-archived into _zvec.so for the Python
+# wheel, so no separate runtime .so is needed. The shared variant is used by
+# C++ tools and tests that link against it directly.
 #
-# As a consequence the plugin .so must NOT carry NEEDED entries for those
-# libs: otherwise the dynamic loader would try to resolve them from disk
-# before invoking dlopen's RTLD_GLOBAL symbol sharing, and the Python wheel
-# (which only ships _zvec.so + the plugin) would fail to load.
-#
-# We therefore link the plugin only against its system-level dependency
-# (libaio) and rely on the global include dirs plus -Wl,--unresolved-symbols
-# =ignore-all to let the linker build a shared library with unresolved
-# references to internal APIs.
-set(CORE_KNN_DISKANN_LIBS "")
+# libaio is loaded at runtime via dlopen()/dlsym() (see libaio_loader.h), so
+# we do NOT link against -laio. The only system-level link dependency is
+# ${CMAKE_DL_LIBS} for dlopen/dlsym/dlclose.
+set(CORE_KNN_DISKANN_LIBS core_framework core_knn_cluster)

 if(CMAKE_SYSTEM_NAME STREQUAL "Linux" AND CMAKE_SYSTEM_PROCESSOR MATCHES "x86_64|i686|i386")
-    list(APPEND CORE_KNN_DISKANN_LIBS aio)
+    list(APPEND CORE_KNN_DISKANN_LIBS ${CMAKE_DL_LIBS})
+endif()
+
+if(NOT APPLE)
+    set(CORE_KNN_DISKANN_LDFLAGS
+        "-Wl,--exclude-libs,libparquet.a:libarrow.a:libarrow_bundled_dependencies.a")
 endif()

 cc_library(
    NAME core_knn_diskann
-    SHARED STRICT
+    STATIC SHARED STRICT ALWAYS_LINK
    SRCS *.cc
    LIBS ${CORE_KNN_DISKANN_LIBS}
    INCS . ${PROJECT_ROOT_DIR}/src/core ${PROJECT_ROOT_DIR}/src/core/algorithm
+    LDFLAGS "${CORE_KNN_DISKANN_LDFLAGS}"
    VERSION "${PROXIMA_ZVEC_VERSION}"
-)
-
-# Internal zvec libs are referenced only for header availability; the actual
-# symbol resolution happens at dlopen time. Expose their public include dirs
-# without adding them as link dependencies.
-foreach(_dep zvec_ailego core_framework core_knn_cluster)
-    if(TARGET ${_dep})
-        target_include_directories(core_knn_diskann PRIVATE
-            $<TARGET_PROPERTY:${_dep},INTERFACE_INCLUDE_DIRECTORIES>)
-        add_dependencies(core_knn_diskann ${_dep})
-    endif()
-endforeach()
-
-# Allow the plugin to have unresolved symbols that will be satisfied at
-# dlopen(RTLD_NOW | RTLD_GLOBAL) time by the hosting binary.
-if(CMAKE_SYSTEM_NAME STREQUAL "Linux")
-    target_link_options(core_knn_diskann PRIVATE
-        "LINKER:--unresolved-symbols=ignore-all")
-endif()
-
-# Rename the artifact to libzvec_diskann_plugin.so so it is clearly identified
-# as an optional plugin that users load at runtime via zvec::LoadDiskAnnPlugin().
-set_target_properties(core_knn_diskann PROPERTIES
-    OUTPUT_NAME zvec_diskann_plugin
 )
@@ -32,6 +32,8 @@ namespace core {
 int DiskAnnBuilder::init(const IndexMeta &meta, const ailego::Params &params) {
  LOG_INFO("Begin DiskAnnBuilder::init");

+  log_diskann_io_backend();
+
  params.get(PARAM_DISKANN_BUILDER_MAX_DEGREE, &max_degree_);
  params.get(PARAM_DISKANN_BUILDER_LIST_SIZE, &list_size_);
  params.get(PARAM_DISKANN_BUILDER_THREAD_COUNT, &build_thread_count_);
@@ -18,6 +18,8 @@
 #include <cstdio>
 #include <cstring>
 #include <iostream>
+#include <ailego/io/io_backend_def.h>
+#include <zvec/ailego/io/io_backend.h>
 #include <zvec/core/framework/index_logger.h>

 #define MAX_EVENTS 1024
@@ -28,11 +30,36 @@ namespace core {
 #if (defined(__linux) || defined(__linux__))
 typedef struct io_event io_event_t;
 typedef struct iocb iocb_t;
+
+// Ensures the I/O backend selection is logged exactly once per process,
+// regardless of which entry point (setup_io_ctx or register_thread)
+// triggers it first.
+static std::once_flag g_io_backend_log_once;
 #endif

+void log_diskann_io_backend() {
+#if (defined(__linux) || defined(__linux__))
+  auto &backend = ailego::IOBackend::Instance();
+  if (backend.is_pread()) {
+    LOG_WARN(
+        "DiskAnn: no async I/O backend available. Install libaio (e.g. "
+        "'apt-get install libaio1', or 'libaio1t64' on Ubuntu 24.04+) and "
+        "retry. DiskAnn will fall back to synchronous pread() — performance "
+        "will be degraded.");
+  } else {
+    LOG_INFO("DiskAnn: I/O backend '%s' loaded — async I/O enabled.",
+             backend.name());
+  }
+#endif
+}
+
 int setup_io_ctx(IOContext &ctx) {
 #if (defined(__linux) || defined(__linux__))
-  int ret = io_setup(MAX_EVENTS, &ctx);
+  std::call_once(g_io_backend_log_once, log_diskann_io_backend);
+  if (ailego::IOBackend::Instance().is_pread()) {
+    return 0;
+  }
+  int ret = LibAioLoader::Instance().io_setup(MAX_EVENTS, &ctx);

  return ret;
 #else
@@ -42,7 +69,10 @@ int setup_io_ctx(IOContext &ctx) {

 int destroy_io_ctx(IOContext &ctx) {
 #if (defined(__linux) || defined(__linux__))
-  int ret = io_destroy(ctx);
+  if (ailego::IOBackend::Instance().is_pread()) {
+    return 0;
+  }
+  int ret = LibAioLoader::Instance().io_destroy(ctx);

  return ret;
 #else
@@ -71,6 +101,9 @@ static int execute_io_pread(int fd, std::vector<AlignedRead> &read_reqs) {
 int execute_io(IOContext ctx, int fd, std::vector<AlignedRead> &read_reqs,
               uint64_t n_retries = 0) {
 #if (defined(__linux) || defined(__linux__))
+  if (ailego::IOBackend::Instance().is_pread()) {
+    return execute_io_pread(fd, read_reqs);
+  }
  uint64_t iters = DiskAnnUtil::div_round_up(read_reqs.size(), MAX_EVENTS);

  for (uint64_t iter = 0; iter < iters; iter++) {
@@ -93,7 +126,8 @@ int execute_io(IOContext ctx, int fd, std::vector<AlignedRead> &read_reqs,
    size_t n_tries = 0;
    // Phase 1: io_submit with retry.
    while (true) {
-      int ret = io_submit(ctx, (int64_t)n_ops, cbs.data());
+      int ret =
+          LibAioLoader::Instance().io_submit(ctx, (int64_t)n_ops, cbs.data());
      if (ret == (int)n_ops) {
        break;
      }
@@ -111,8 +145,8 @@ int execute_io(IOContext ctx, int fd, std::vector<AlignedRead> &read_reqs,
    // Phase 2: io_getevents with retry (never re-submits).
    n_tries = 0;
    while (true) {
-      int ret = io_getevents(ctx, (int64_t)n_ops, (int64_t)n_ops, evts.data(),
-                             nullptr);
+      int ret = LibAioLoader::Instance().io_getevents(
+          ctx, (int64_t)n_ops, (int64_t)n_ops, evts.data(), nullptr);
      if (ret == (int)n_ops) {
        break;
      }
@@ -188,16 +222,19 @@ void LinuxAlignedFileReader::register_thread() {

  IOContext ctx = nullptr;

-  int ret = io_setup(MAX_EVENTS, &ctx);
-  if (ret != 0) {
+  std::call_once(g_io_backend_log_once, log_diskann_io_backend);
+  if (ailego::IOBackend::Instance().is_pread()) {
    lk.unlock();
+    return;
+  }
+  int ret = LibAioLoader::Instance().io_setup(MAX_EVENTS, &ctx);
+  if (ret != 0) {
    if (ret == -EAGAIN) {
      LOG_ERROR(
          "io_setup failed with EAGAIN: Consider increasing "
          "/proc/sys/fs/aio-max-nr");
    } else {
      LOG_ERROR("io_setup failed; returned: %d, %s", ret, ::strerror(-ret));
-      ;
    }
  } else {
    LOG_INFO("allocating ctx: %lu", (uint64_t)ctx);
@@ -226,7 +263,10 @@ void LinuxAlignedFileReader::deregister_thread() {
  }

  // io_destroy is a syscall; keep it outside the lock to avoid blocking others
-  io_destroy(ctx);
+  if (ailego::IOBackend::Instance().available() !=
+      ailego::IOBackendType::kPread) {
+    LibAioLoader::Instance().io_destroy(ctx);
+  }
  LOG_INFO("returned ctx from thread");
 #endif
 }
@@ -234,9 +274,13 @@ void LinuxAlignedFileReader::deregister_thread() {
 void LinuxAlignedFileReader::deregister_all_threads() {
 #if (defined(__linux) || defined(__linux__))
  std::unique_lock<std::mutex> lk(ctx_mut);
+  bool aio_available = ailego::IOBackend::Instance().available() !=
+                       ailego::IOBackendType::kPread;
  for (auto x = ctx_map.begin(); x != ctx_map.end(); x++) {
    IOContext ctx = x->second;
-    io_destroy(ctx);
+    if (aio_available) {
+      LibAioLoader::Instance().io_destroy(ctx);
+    }
  }
  ctx_map.clear();
 #endif
@@ -18,7 +18,7 @@
 #include <fcntl.h>

 #if (defined(__linux) || defined(__linux__))
-#include <libaio.h>
+#include <ailego/io/libaio_loader.h>  // dlopen-based libaio wrapper
 #endif

 #include <unistd.h>
@@ -39,6 +39,10 @@ typedef uint32_t IOContext;
 int setup_io_ctx(IOContext &ctx);
 int destroy_io_ctx(IOContext &ctx);

+// Log the current DiskAnn I/O backend status (async vs. synchronous pread).
+// Probes the backend on first call.  No-op on non-Linux platforms.
+void log_diskann_io_backend();
+
 struct AlignedRead {
  uint64_t offset;
  uint64_t len;
@@ -25,6 +25,8 @@ DiskAnnSearcher::DiskAnnSearcher() {}
 DiskAnnSearcher::~DiskAnnSearcher() {}

 int DiskAnnSearcher::init(const ailego::Params &search_params) {
+  log_diskann_io_backend();
+
  search_params.get(PARAM_DISKANN_SEARCHER_LIST_SIZE, &list_size_);
  search_params.get(PARAM_DISKANN_SEARCHER_CACHE_NODE_NUM, &cache_nodes_num_);
  return 0;
@@ -28,6 +28,9 @@ DiskAnnStreamer::~DiskAnnStreamer() {}
 int DiskAnnStreamer::init(const IndexMeta &meta,
                          const ailego::Params &search_params) {
  meta_ = meta;
+
+  log_diskann_io_backend();
+
  search_params.get(PARAM_DISKANN_SEARCHER_LIST_SIZE, &list_size_);
  search_params.get(PARAM_DISKANN_SEARCHER_CACHE_NODE_NUM, &cache_nodes_num_);
  return 0;
@@ -1,10 +1,15 @@
 include(${PROJECT_ROOT_DIR}/cmake/bazel.cmake)
 include(${PROJECT_ROOT_DIR}/cmake/option.cmake)

+set(CORE_INTERFACE_LIBS zvec_ailego core_framework sparsehash magic_enum rabitqlib)
+if(CMAKE_SYSTEM_NAME STREQUAL "Linux")
+    list(APPEND CORE_INTERFACE_LIBS ${CMAKE_DL_LIBS})
+endif()
+
 cc_library(
        NAME core_interface STATIC STRICT ALWAYS_LINK
        SRCS *.cc indexes/*.cc
        INCS . ${PROJECT_ROOT_DIR}/src/ ${PROJECT_ROOT_DIR}/src/core
-        LIBS zvec_ailego core_framework core_plugin sparsehash magic_enum rabitqlib
+        LIBS ${CORE_INTERFACE_LIBS}
        VERSION "${PROXIMA_ZVEC_VERSION}"
 )
@@ -16,61 +16,12 @@
 #include <mutex>
 #include <string>
 #include <zvec/core/interface/index.h>
-#include <zvec/plugin/diskann_plugin.h>
 #include "algorithm/diskann/diskann_params.h"
 #include "holder_builder.h"

 namespace zvec::core_interface {

-namespace {
-
-// Implicitly bring the DiskAnn runtime online on first use. This keeps the
-// DiskAnn index an ordinary public API (users just instantiate a
-// DiskAnnIndexParam) while still letting the rest of the library — HNSW,
-// IVF, Flat, Vamana — run on hosts that happen to lack libaio. On such
-// hosts only DiskAnn fails, with a clear, actionable error message, and
-// every other index type stays fully functional.
-int EnsureDiskAnnRuntimeReady() {
-  static std::once_flag once;
-  static int cached_result = 0;
-  std::call_once(once, []() {
-    const int status = ::zvec::LoadDiskAnnPlugin();
-    if (status == kDiskAnnPluginOk) {
-      cached_result = 0;
-      return;
-    }
-    switch (status) {
-      case kDiskAnnPluginLibAioMissing:
-        LOG_ERROR(
-            "DiskAnn requires libaio at runtime, but it was not found on this "
-            "host. Install it (e.g. 'apt-get install libaio1' on "
-            "Debian/Ubuntu, "
-            "or 'libaio1t64' on Ubuntu 24.04+) and retry.");
-        break;
-      case kDiskAnnPluginUnsupportedPlatform:
-        LOG_ERROR("DiskAnn is only supported on Linux x86_64.");
-        break;
-      case kDiskAnnPluginDlopenFailed:
-      default:
-        LOG_ERROR("Failed to initialize the DiskAnn runtime (status=%d).",
-                  status);
-        break;
-    }
-    cached_result = core::IndexError_Runtime;
-  });
-  return cached_result;
-}
-
-}  // namespace
-
 int DiskAnnIndex::CreateAndInitStreamer(const BaseIndexParam &param) {
-  // Fail fast and cleanly if the DiskAnn runtime cannot be brought up on
-  // this host (most commonly: libaio is missing). The rest of zvec keeps
-  // running; only DiskAnn is unusable.
-  if (int rc = EnsureDiskAnnRuntimeReady(); rc != 0) {
-    return rc;
-  }
-
  if (is_sparse_) {
    LOG_ERROR("Failed to create streamer. Sparse is not Supported.");
    return core::IndexError_Unsupported;
@@ -1,29 +0,0 @@
-##
-##  Copyright (C) The Software Authors. All rights reserved.
-##
-##  \file     CMakeLists.txt
-##  \brief    Build script for the zvec internal plugin-loading glue library.
-##            Lives inside the main zvec_core artifact and provides the
-##            implicit DiskAnn runtime bring-up used by DiskAnnIndex on first
-##            use. These APIs are NOT part of the public user surface: users
-##            simply instantiate ``DiskAnnIndexParam`` / ``DiskAnnIndex`` and
-##            the runtime (``libzvec_diskann_plugin.so``) is loaded behind
-##            the scenes.
-##
-
-include(${PROJECT_ROOT_DIR}/cmake/bazel.cmake)
-include(${PROJECT_ROOT_DIR}/cmake/option.cmake)
-
-set(CORE_PLUGIN_LIBS zvec_ailego core_framework)
-if(CMAKE_SYSTEM_NAME STREQUAL "Linux")
-    list(APPEND CORE_PLUGIN_LIBS ${CMAKE_DL_LIBS})
-endif()
-
-cc_library(
-    NAME core_plugin
-    STATIC STRICT ALWAYS_LINK
-    SRCS *.cc
-    LIBS ${CORE_PLUGIN_LIBS}
-    INCS . ${PROJECT_ROOT_DIR}/src/core
-    VERSION "${PROXIMA_ZVEC_VERSION}"
-)
@@ -1,322 +0,0 @@
-// Copyright 2025-present the zvec project
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-#include <atomic>
-#include <mutex>
-#include <string>
-#include <vector>
-#include <zvec/core/framework/index_logger.h>
-#include <zvec/plugin/diskann_plugin.h>
-
-#if defined(__linux__) || defined(__linux) || defined(__APPLE__)
-#include <dlfcn.h>
-#include <unistd.h>
-#endif
-
-#if defined(__linux__) || defined(__linux)
-#include <limits.h>
-#endif
-
-namespace zvec {
-
-namespace {
-
-#if defined(__linux__) || defined(__linux)
-constexpr const char *kPluginFileName = "libzvec_diskann_plugin.so";
-// Candidate soname list. On Ubuntu 24.04 the libaio package was renamed with
-// the t64 suffix (64-bit time_t transition), so we probe both spellings.
-constexpr const char *kLibAioSoNames[] = {
-    "libaio.so.1",
-    "libaio.so.1t64",
-};
-constexpr bool kPlatformSupportsDiskAnnPlugin = true;
-#elif defined(__APPLE__)
-[[maybe_unused]] constexpr const char *kPluginFileName =
-    "libzvec_diskann_plugin.dylib";
-constexpr bool kPlatformSupportsDiskAnnPlugin = false;
-#else
-[[maybe_unused]] constexpr const char *kPluginFileName =
-    "zvec_diskann_plugin.dll";
-constexpr bool kPlatformSupportsDiskAnnPlugin = false;
-#endif
-
-// Global plugin handle. Nullptr means "not loaded".
-std::atomic<void *> g_plugin_handle{nullptr};
-std::mutex g_plugin_mutex;
-
-#if defined(__linux__) || defined(__linux)
-
-// Resolve the directory containing the currently running executable, so we
-// can look for the plugin next to it regardless of the working directory.
-std::string GetExecutableDir() {
-  char buf[PATH_MAX];
-  ssize_t n = ::readlink("/proc/self/exe", buf, sizeof(buf) - 1);
-  if (n <= 0) {
-    return {};
-  }
-  buf[n] = '\0';
-  std::string path(buf);
-  auto slash = path.find_last_of('/');
-  if (slash == std::string::npos) {
-    return {};
-  }
-  return path.substr(0, slash);
-}
-
-// Resolve the directory containing the shared object that hosts this
-// function. For Python wheels this is the directory of
-// ``_zvec.cpython-*.so``; for regular C++ binaries it is the directory of
-// ``libzvec_core.so``. In either case the DiskAnn plugin is shipped
-// alongside, so this is the most reliable lookup location.
-//
-// NOTE: we pass the address of an *exported* function (LoadDiskAnnPlugin)
-// rather than one in this anonymous namespace, because dladdr() on a symbol
-// with internal linkage can report the main executable instead of the
-// hosting shared object when the translation unit is whole-archived into
-// another .so.
-std::string ResolveHostingSoDir() {
-  ::Dl_info info{};
-  if (::dladdr(reinterpret_cast<void *>(&::zvec::LoadDiskAnnPlugin), &info) ==
-          0 ||
-      info.dli_fname == nullptr) {
-    return {};
-  }
-  std::string path(info.dli_fname);
-  auto slash = path.find_last_of('/');
-  if (slash == std::string::npos) {
-    return {};
-  }
-  return path.substr(0, slash);
-}
-
-// Full path of the shared object that hosts LoadDiskAnnPlugin, or empty
-// string on failure.
-std::string ResolveHostingSoPath() {
-  ::Dl_info info{};
-  if (::dladdr(reinterpret_cast<void *>(&::zvec::LoadDiskAnnPlugin), &info) ==
-          0 ||
-      info.dli_fname == nullptr) {
-    return {};
-  }
-  return std::string(info.dli_fname);
-}
-
-// Promote the hosting shared object (e.g. the Python extension module
-// ``_zvec.cpython-*.so``) to the global symbol scope. Python loads C
-// extensions with RTLD_LOCAL by default, which means their C++ symbols are
-// invisible to subsequently dlopen(RTLD_GLOBAL)ed libraries. Without this
-// promotion, the DiskAnn plugin's undefined references to zvec:: symbols
-// cannot be resolved against the already-loaded host module and dlopen
-// fails with messages like:
-//
-//   undefined symbol: _ZN4zvec6ailego6Logger10LEVEL_INFOE
-//
-// Using RTLD_NOLOAD re-opens the existing image without loading it again,
-// while RTLD_GLOBAL merges its symbols into the global scope. This is a
-// no-op for hosts that were already loaded with RTLD_GLOBAL.
-void PromoteHostingSoToGlobal() {
-  const std::string host = ResolveHostingSoPath();
-  if (host.empty()) {
-    return;
-  }
-  // When LoadDiskAnnPlugin is statically linked into the main executable,
-  // dladdr resolves to the executable itself. The main exe's symbols are
-  // already in the global scope by definition, so skip promotion.
-  const std::string exe_path = GetExecutableDir();
-  if (!exe_path.empty()) {
-    char exe_buf[PATH_MAX];
-    ssize_t n = ::readlink("/proc/self/exe", exe_buf, sizeof(exe_buf) - 1);
-    if (n > 0) {
-      exe_buf[n] = '\0';
-      // Compare resolved real paths to handle relative vs absolute.
-      char host_real[PATH_MAX];
-      char exe_real[PATH_MAX];
-      if (::realpath(host.c_str(), host_real) != nullptr &&
-          ::realpath(exe_buf, exe_real) != nullptr &&
-          std::string(host_real) == std::string(exe_real)) {
-        // Host IS the main executable; symbols are already global.
-        return;
-      }
-    }
-  }
-  void *h = ::dlopen(host.c_str(), RTLD_NOW | RTLD_GLOBAL | RTLD_NOLOAD);
-  if (h == nullptr) {
-    const char *err = ::dlerror();
-    LOG_WARN("Could not promote host '%s' to RTLD_GLOBAL: %s", host.c_str(),
-             err ? err : "unknown");
-    return;
-  }
-  // We purposely keep the handle refcount incremented for the life of the
-  // process: there is no safe point at which to dlclose() it, and doing so
-  // would only decrement the count anyway (the image remains mapped because
-  // Python still holds its own reference).
-  (void)h;
-}
-
-// Build the list of candidate paths for the plugin.
-std::vector<std::string> BuildCandidatePaths(const std::string &explicit_path) {
-  std::vector<std::string> candidates;
-  if (!explicit_path.empty()) {
-    candidates.push_back(explicit_path);
-    return candidates;
-  }
-
-  // Helper that pushes both ``<dir>/<plugin>`` and ``<dir>/../lib/<plugin>``
-  // to handle the conventional CMake build layout where executables live in
-  // ``bin/`` while shared objects (including this plugin) live in ``lib/``.
-  auto push_dir_candidates = [&candidates](const std::string &dir) {
-    if (dir.empty()) {
-      return;
-    }
-    candidates.push_back(dir + "/" + kPluginFileName);
-    candidates.push_back(dir + "/../lib/" + kPluginFileName);
-  };
-
-  // 1. Directory of the library that hosts LoadDiskAnnPlugin (e.g. the
-  //    Python extension module or libzvec_core). This works for Python,
-  //    C++ embedding, and most packaging layouts.
-  const std::string own_dir = ResolveHostingSoDir();
-  push_dir_candidates(own_dir);
-  // 2. Directory of the running executable. Useful for self-contained C++
-  //    tools that drop the plugin next to their binary, as well as for the
-  //    standard CMake bin/lib split (handled by ``../lib/`` above).
-  const std::string exe_dir = GetExecutableDir();
-  if (!exe_dir.empty() && exe_dir != own_dir) {
-    push_dir_candidates(exe_dir);
-  }
-  // 3. Fallback: rely on the dynamic linker's default search path
-  //    (RPATH / LD_LIBRARY_PATH / /etc/ld.so.conf).
-  candidates.emplace_back(kPluginFileName);
-  return candidates;
-}
-
-#endif  // linux
-
-}  // namespace
-
-bool IsLibAioAvailable() {
-#if defined(__linux__) || defined(__linux)
-  const char *kRequiredSymbols[] = {"io_setup", "io_submit", "io_getevents",
-                                    "io_destroy"};
-  for (const char *soname : kLibAioSoNames) {
-    // RTLD_LAZY keeps the cost low; we only need to know whether the library
-    // is resolvable and exposes the symbols DiskAnn actually calls.
-    void *handle = ::dlopen(soname, RTLD_LAZY);
-    if (handle == nullptr) {
-      continue;
-    }
-    bool ok = true;
-    for (const char *sym : kRequiredSymbols) {
-      if (::dlsym(handle, sym) == nullptr) {
-        ok = false;
-        break;
-      }
-    }
-    ::dlclose(handle);
-    if (ok) {
-      return true;
-    }
-  }
-  return false;
-#else
-  return false;
-#endif
-}
-
-bool IsDiskAnnPluginLoaded() {
-  return g_plugin_handle.load(std::memory_order_acquire) != nullptr;
-}
-
-int LoadDiskAnnPlugin(const std::string &path) {
-  if (!kPlatformSupportsDiskAnnPlugin) {
-    LOG_ERROR(
-        "DiskAnn plugin is not supported on this platform; it is only "
-        "available on Linux x86_64 with libaio.");
-    return kDiskAnnPluginUnsupportedPlatform;
-  }
-
-#if defined(__linux__) || defined(__linux)
-  // Fast path: already loaded.
-  if (g_plugin_handle.load(std::memory_order_acquire) != nullptr) {
-    return kDiskAnnPluginOk;
-  }
-
-  std::lock_guard<std::mutex> lock(g_plugin_mutex);
-  if (g_plugin_handle.load(std::memory_order_relaxed) != nullptr) {
-    return kDiskAnnPluginOk;
-  }
-
-  if (!IsLibAioAvailable()) {
-    LOG_ERROR(
-        "libaio is not available on this host; the DiskAnn runtime cannot be "
-        "activated. Install libaio1 (e.g. 'apt-get install libaio1', or "
-        "'libaio1t64' on Ubuntu 24.04+) and retry. This does not affect "
-        "other index types (HNSW, IVF, Flat, Vamana).");
-    return kDiskAnnPluginLibAioMissing;
-  }
-
-  const std::vector<std::string> candidates = BuildCandidatePaths(path);
-  // Ensure the hosting module's C++ symbols (zvec::*) are visible to the
-  // plugin at dlopen time. See PromoteHostingSoToGlobal() for the rationale.
-  PromoteHostingSoToGlobal();
-  void *handle = nullptr;
-  std::string last_error;
-  for (const std::string &candidate : candidates) {
-    // RTLD_GLOBAL so the plugin's factory registrations (which live in the
-    // plugin's own static-init code) can reference symbols from the main
-    // library, and any callers that later dlsym against the process can see
-    // the plugin's symbols.
-    handle = ::dlopen(candidate.c_str(), RTLD_NOW | RTLD_GLOBAL);
-    if (handle != nullptr) {
-      LOG_INFO("Loaded DiskAnn plugin from: %s", candidate.c_str());
-      break;
-    }
-    const char *err = ::dlerror();
-    last_error = err ? err : "unknown dlopen error";
-    LOG_DEBUG("dlopen(%s) failed: %s", candidate.c_str(), last_error.c_str());
-  }
-
-  if (handle == nullptr) {
-    LOG_ERROR("Failed to load DiskAnn plugin; last error: %s",
-              last_error.c_str());
-    return kDiskAnnPluginDlopenFailed;
-  }
-
-  g_plugin_handle.store(handle, std::memory_order_release);
-  return kDiskAnnPluginOk;
-#else
-  (void)path;
-  return kDiskAnnPluginUnsupportedPlatform;
-#endif
-}
-
-bool UnloadDiskAnnPlugin() {
-#if defined(__linux__) || defined(__linux)
-  std::lock_guard<std::mutex> lock(g_plugin_mutex);
-  void *handle = g_plugin_handle.exchange(nullptr, std::memory_order_acq_rel);
-  if (handle == nullptr) {
-    return false;
-  }
-  if (::dlclose(handle) != 0) {
-    const char *err = ::dlerror();
-    LOG_WARN("dlclose for DiskAnn plugin returned non-zero: %s",
-             err ? err : "unknown");
-  }
-  return true;
-#else
-  return false;
-#endif
-}
-
-}  // namespace zvec
@@ -20,7 +20,6 @@
 #include <zvec/db/schema.h>
 #include <zvec/db/status.h>
 #include <zvec/db/type.h>
-#include <zvec/plugin/diskann_plugin.h>
 #include "ailego/internal/cpu_features.h"
 #include "db/common/constants.h"
 #include "db/common/typedef.h"
@@ -154,7 +153,8 @@ Status FieldSchema::validate() const {
            support_dense_vector_index.end()) {
          return Status::InvalidArgument(
              "schema validate failed: dense_vector's index_params only "
-              "support FLAT|HNSW|IVF index, but field[",
+              "support FLAT|HNSW|HNSW_RABITQ|IVF|DISKANN|VAMANA index, but "
+              "field[",
              name_, "]'s index_type is ",
              IndexTypeCodeBook::AsString(index_params_->type()));
        }
@@ -198,30 +198,20 @@ Status FieldSchema::validate() const {
      }

      if (index_params_->type() == IndexType::DISKANN) {
-        // Probe the DiskAnn runtime eagerly at creation time so unsupported
-        // platforms (non Linux x86_64), missing libaio, or a missing plugin
-        // .so fail fast with a clear message instead of surfacing later during
-        // optimize(). This reuses the same gate DiskAnnIndex applies on first
-        // use (zvec::LoadDiskAnnPlugin, wrapped by EnsureDiskAnnRuntimeReady).
-        // All validate() call sites are creation-time only, so triggering the
-        // plugin load here is safe (and idempotent/cached).
-        const int rc = ::zvec::LoadDiskAnnPlugin();
-        switch (rc) {
-          case kDiskAnnPluginOk:
-            break;
-          case kDiskAnnPluginUnsupportedPlatform:
-            return Status::NotSupported(
-                "DiskAnn is not supported on this platform (Linux x86_64 "
-                "only)");
-          case kDiskAnnPluginLibAioMissing:
-            return Status::NotSupported(
-                "DiskAnn requires libaio at runtime, but it was not found on "
-                "this host. Install it (e.g. 'apt-get install libaio1', or "
-                "'libaio1t64' on Ubuntu 24.04+) and retry.");
-          default:
-            return Status::NotSupported(
-                "DiskAnn runtime could not be initialized on this host");
-        }
+        // DiskAnn requires Linux x86_64/i686/i386.  The CMake variable
+        // DISKANN_SUPPORTED (defined in the top-level CMakeLists.txt) is the
+        // single source of truth for platform eligibility — it is also used by
+        // index_factory.cc to conditionally compile the DiskAnn index
+        // registration.  Using the same macro here ensures that schema
+        // validation and index registration agree on supported platforms.
+        //
+        // libaio is loaded eagerly (via dlopen) inside DiskAnnBuilder::init()
+        // and DiskAnnStreamer::init(); if libaio is missing, DiskAnn falls
+        // back to synchronous pread() with degraded performance.
+#if !DISKANN_SUPPORTED
+        return Status::NotSupported(
+            "DiskAnn is not supported on this platform (Linux x86_64 only)");
+#endif
      }


@@ -0,0 +1,46 @@
+// Copyright 2025-present the zvec project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// I/O backend type enum.
+//
+// This is the public, dependency-free part of the I/O backend abstraction.
+// It defines the IOBackendType enum and the convenience helpers
+// current_io_backend_type() / current_io_backend_description() so that
+// public headers can reference IOBackendType without pulling in the
+// internal IOBackend singleton or libaio_loader.
+
+#pragma once
+
+#include <string>
+#include <zvec/ailego/internal/platform.h>
+
+namespace zvec {
+namespace ailego {
+
+// Supported I/O backend types.
+enum class IOBackendType {
+  kPread,   // Synchronous pread() — no async I/O
+  kLibAio,  // libaio loaded at runtime via dlopen()
+};
+
+// Returns the currently active I/O backend type.
+// Triggers backend initialization on first call (libaio > pread).
+IOBackendType current_io_backend_type();
+
+// Returns a human-readable description of the currently active I/O backend.
+// When only pread is available, includes installation guidance for libaio.
+std::string current_io_backend_description();
+
+}  // namespace ailego
+}  // namespace zvec
@@ -120,15 +120,18 @@ class Factory {
  //! a guard variable (`_ZGVZN...E7factory`) alongside the object, and both
  //! must be unified across DSOs for the singleton to be shared.
  //!
-  //! In the Python extension build the _zvec.so version script exports the
-  //! storage (`zvec::*` matches its demangled name) while the guard variable,
-  //! whose demangled form is `guard variable for zvec::...`, ends up hidden
-  //! (compilers emit the guard in a COMDAT group whose visibility is not
-  //! upgraded by our version script). When libzvec_diskann_plugin.so is
-  //! loaded, _zvec.so and the plugin then share the `factory` storage but
-  //! each have their own guard; the plugin's still-zero guard triggers a
-  //! second run of the Factory constructor on the shared storage, wiping
-  //! all registrations performed during _zvec.so import (e.g. FlatStreamer).
+  //! Historically (when DiskAnn was a runtime-loaded shared plugin) the
+  //! _zvec.so version script exported the storage (`zvec::*` matches its
+  //! demangled name) while the guard variable, whose demangled form is
+  //! `guard variable for zvec::...`, ended up hidden (compilers emit the
+  //! guard in a COMDAT group whose visibility is not upgraded by our version
+  //! script). When the plugin was loaded, _zvec.so and the plugin shared the
+  //! `factory` storage but each had its own guard; the plugin's still-zero
+  //! guard triggered a second run of the Factory constructor on the shared
+  //! storage, wiping out registrations performed during _zvec.so import.
+  //! DiskAnn is now statically linked into _zvec.so, so this DSO-splitting
+  //! issue no longer applies, but the atomic-pointer pattern is retained as
+  //! a defensive measure.
  //!
  //! A constant-initialized static std::atomic<T*> has NO guard variable
  //! (its zero init is compile-time), so we use a leaked heap singleton with
@@ -774,6 +774,51 @@ ZVEC_EXPORT void ZVEC_CALL zvec_set_default_jieba_dict_dir(const char *dir);
 */
 ZVEC_EXPORT const char *ZVEC_CALL zvec_get_default_jieba_dict_dir(void);

+// =============================================================================
+// I/O Backend Introspection
+// =============================================================================
+
+/**
+ * @brief I/O backend type codes for DiskAnn async disk reads.
+ *
+ * Defined as uint32_t constants for consistent binary representation
+ * across C and C++ boundaries.
+ */
+typedef uint32_t zvec_io_backend_type_t;
+#define ZVEC_IO_BACKEND_TYPE_PREAD \
+  0 /**< Synchronous pread() \u2014 no async I/O */
+#define ZVEC_IO_BACKEND_TYPE_LIBAIO \
+  1 /**< libaio loaded at runtime via dlopen() */
+
+/**
+ * @brief Get the current I/O backend type for DiskAnn async disk reads.
+ *
+ * Pure introspection \u2014 no side effects, no install hints.
+ *
+ * @return zvec_io_backend_type_t The loaded backend type
+ *         (ZVEC_IO_BACKEND_TYPE_LIBAIO or ZVEC_IO_BACKEND_TYPE_PREAD).
+ */
+ZVEC_EXPORT zvec_io_backend_type_t ZVEC_CALL zvec_get_io_backend_type(void);
+
+/**
+ * @brief Get a human-readable name for the given I/O backend type.
+ *
+ * @param type The backend type code.
+ * @return Thread-local string valid until the next call on this thread;
+ *         "libaio", "pread", or "unknown".
+ */
+ZVEC_EXPORT const char *ZVEC_CALL
+zvec_get_io_backend_type_name(zvec_io_backend_type_t type);
+
+/**
+ * @brief Get a human-readable description of the current I/O backend.
+ *
+ * When only pread is available, includes installation guidance for libaio.
+ *
+ * @return Thread-local string valid until the next call on this thread.
+ */
+ZVEC_EXPORT const char *ZVEC_CALL zvec_get_io_backend_description(void);
+
 // =============================================================================
 // Data Type Enumerations
 // =============================================================================
@@ -826,6 +871,7 @@ typedef uint32_t zvec_index_type_t;
 #define ZVEC_INDEX_TYPE_HNSW 1
 #define ZVEC_INDEX_TYPE_IVF 2
 #define ZVEC_INDEX_TYPE_FLAT 3
+#define ZVEC_INDEX_TYPE_HNSW_RABITQ 4
 #define ZVEC_INDEX_TYPE_DISKANN 5
 #define ZVEC_INDEX_TYPE_VAMANA 6
 #define ZVEC_INDEX_TYPE_INVERT 10
@@ -1,84 +0,0 @@
-// Copyright 2025-present the zvec project
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-#pragma once
-
-#include <string>
-
-// NOTE: The APIs declared in this header are INTERNAL to zvec. They are
-// invoked implicitly by ``DiskAnnIndex`` on first use so that DiskAnn works
-// out of the box, without users ever calling a ``load_diskann_plugin()`` /
-// ``is_libaio_available()`` entry point. External callers should not depend
-// on these symbols; they may change or be removed in future releases. On
-// hosts missing libaio the bring-up fails cleanly and only DiskAnn becomes
-// unavailable — other index types (HNSW / IVF / Flat / Vamana) keep working.
-
-#if defined(_WIN32) || defined(__CYGWIN__)
-#ifdef ZVEC_BUILD_SHARED
-#define ZVEC_PLUGIN_EXPORT __declspec(dllexport)
-#elif defined(ZVEC_USE_SHARED)
-#define ZVEC_PLUGIN_EXPORT __declspec(dllimport)
-#else
-#define ZVEC_PLUGIN_EXPORT
-#endif
-#else
-#if __GNUC__ >= 4
-#define ZVEC_PLUGIN_EXPORT __attribute__((visibility("default")))
-#else
-#define ZVEC_PLUGIN_EXPORT
-#endif
-#endif
-
-namespace zvec {
-
-// Return codes for LoadDiskAnnPlugin().
-enum DiskAnnPluginStatus {
-  kDiskAnnPluginOk = 0,
-  kDiskAnnPluginUnsupportedPlatform = -1,
-  kDiskAnnPluginLibAioMissing = -2,
-  kDiskAnnPluginDlopenFailed = -3,
-};
-
-// Returns true if libaio is present on the host and the minimum set of symbols
-// required by the DiskAnn runtime (io_setup / io_submit / io_getevents /
-// io_destroy) can be resolved at runtime.
-//
-// Internal probe used by ``LoadDiskAnnPlugin`` before attempting dlopen. Not
-// part of the user-facing API.
-ZVEC_PLUGIN_EXPORT bool IsLibAioAvailable();
-
-// Load the DiskAnn runtime shared library (libzvec_diskann_plugin.so) via
-// dlopen(). Invoked implicitly by ``DiskAnnIndex::CreateAndInitStreamer`` on
-// first use; callers should not invoke it directly. The call is idempotent
-// and returns ``kDiskAnnPluginOk`` when the runtime is already active.
-//
-// Search order when ``path`` is empty:
-//   1. next to the currently running executable (``/proc/self/exe`` on Linux);
-//   2. next to the hosting shared object (e.g. ``_zvec.cpython-*.so``);
-//   3. the platform default dynamic-linker search path (RPATH,
-//      ``LD_LIBRARY_PATH``, ``/etc/ld.so.conf``, …).
-ZVEC_PLUGIN_EXPORT int LoadDiskAnnPlugin(const std::string &path = "");
-
-// Returns true if the DiskAnn runtime is currently loaded in this process.
-// Internal diagnostic; not a user-facing API.
-ZVEC_PLUGIN_EXPORT bool IsDiskAnnPluginLoaded();
-
-// Unload the DiskAnn runtime. Internal only — unloading a library that has
-// registered itself into global factory singletons is inherently racy;
-// callers must guarantee that no DiskAnn objects are still alive and no
-// background threads are executing DiskAnn code before calling this. Returns
-// true when a live handle was released.
-ZVEC_PLUGIN_EXPORT bool UnloadDiskAnnPlugin();
-
-}  // namespace zvec
@@ -6221,7 +6221,7 @@ void test_diskann_index_params_functions(void) {

  // to_string should report DiskANN
  const char *type_str = zvec_index_type_to_string(ZVEC_INDEX_TYPE_DISKANN);
-  TEST_ASSERT(type_str != NULL && strcmp(type_str, "DiskANN") == 0);
+  TEST_ASSERT(type_str != NULL && strcmp(type_str, "DISKANN") == 0);

  zvec_index_params_destroy(params);
  TEST_END();
@@ -7,7 +7,7 @@ foreach(CC_SRCS ${ALL_TEST_SRCS})
  cc_gtest(
      NAME ${CC_TARGET}
      STRICT
-      LIBS zvec_ailego core_framework core_utility core_metric core_quantizer core_knn_cluster core_plugin core_knn_diskann
+      LIBS zvec_ailego core_framework core_utility core_metric core_quantizer core_knn_cluster core_knn_diskann
      SRCS ${CC_SRCS}
      INCS . ${PROJECT_ROOT_DIR}/src/core ${PROJECT_ROOT_DIR}/src/core/algorithm/diskann
    )
@@ -143,18 +143,6 @@ TEST_F(DiskAnnBuilderTest, SmallDatasetBuildTime) {
      << " ms — likely a lost-wakeup regression in progress loops.";
 }

-// DiskAnn is now exposed implicitly: no caller ever invokes a
-// ``LoadDiskAnnPlugin`` / ``IsLibAioAvailable`` API (those were removed from
-// the public surface together with ``zvec.load_diskann_plugin()`` in Python).
-// The only contract this test validates is the UX guarantee: once the DiskAnn
-// module has been linked into the hosting binary (here, directly into the
-// test via the ``core_knn_diskann`` target), its factory entries are
-// registered automatically and the global ``IndexFactory`` can hand out a
-// ``DiskAnnBuilder`` without any explicit setup step. On hosts missing
-// libaio, DiskAnn would fail at the index-creation layer with a clear error
-// while other index types (HNSW/IVF/Flat/Vamana) remain unaffected; that
-// runtime branch lives in ``DiskAnnIndex::CreateAndInitStreamer`` and is
-// covered by the higher-level interface tests.
 TEST_F(DiskAnnBuilderTest, TestImplicitFactoryRegistration) {
  IndexBuilder::Pointer builder = IndexFactory::CreateBuilder("DiskAnnBuilder");
  ASSERT_NE(builder, nullptr)
@@ -8,7 +8,7 @@ foreach(CC_SRCS ${ALL_TEST_SRCS})
      NAME ${CC_TARGET}
      STRICT
      LIBS zvec_ailego core_framework core_metric core_interface core_knn_flat core_utility core_quantizer sparsehash core_knn_hnsw core_mix_reducer
-          core_knn_flat_sparse core_knn_hnsw_sparse core_knn_ivf core_knn_hnsw_rabitq core_knn_vamana
+          core_knn_flat_sparse core_knn_hnsw_sparse core_knn_ivf core_knn_hnsw_rabitq core_knn_vamana core_knn_diskann
      SRCS ${CC_SRCS}
      INCS . ${PROJECT_ROOT_DIR}/src/core ${PROJECT_ROOT_DIR}/src/core/algorithm
    )
@@ -885,7 +885,7 @@ int main(int argc, char *argv[]) {
                         : "debug";
  transform(log_level.begin(), log_level.end(), log_level.begin(), ::tolower);
  if (LOG_LEVEL.find(log_level) != LOG_LEVEL.end()) {
-    IndexLoggerBroker::SetLevel(LOG_LEVEL[log_level]);
+    zvec::ailego::LoggerBroker::SetLevel(LOG_LEVEL[log_level]);
  }

  // Calculate Bench
@@ -1882,7 +1882,7 @@ int main(int argc, char *argv[]) {
                         : "debug";
  transform(log_level.begin(), log_level.end(), log_level.begin(), ::tolower);
  if (LOG_LEVEL.find(log_level) != LOG_LEVEL.end()) {
-    IndexLoggerBroker::SetLevel(LOG_LEVEL[log_level]);
+    zvec::ailego::LoggerBroker::SetLevel(LOG_LEVEL[log_level]);
  }

  // Calculate Recall