From fa5a6c6ee9427b8002558e19bf0efedf8b3733a8 Mon Sep 17 00:00:00 2001
From: Rodrigo Lopez <rodrigo.lopez@weaviate.io>
Date: Tue, 8 Sep 2026 12:39:57 +0200
Subject: [PATCH] Add pathseer filter strategy for HNSW vector index

Weaviate core is adding an adaptive filtered-HNSW search strategy
named 'pathseer' (weaviate/weaviate#12137) as a third filterStrategy
value alongside 'sweeping' and 'acorn'. Expose it in the client via a
new VectorFilterStrategy.PATHSEER enum member.

Includes a unit test for serialization and an integration test (gated
on server >= 1.40.0) covering creation and runtime updates in both
directions.
---
 integration/test_collection_config.py         | 36 +++++++++++++++++++
 test/collection/test_config.py                | 11 ++++++
 .../classes/config_vector_index.py            |  2 ++
 3 files changed, 49 insertions(+)

diff --git a/integration/test_collection_config.py b/integration/test_collection_config.py
index 68f1a0691..9a129e697 100644
--- a/integration/test_collection_config.py
+++ b/integration/test_collection_config.py
@@ -702,6 +702,42 @@ def test_hnsw_with_rq4c(collection_factory: CollectionFactory) -> None:
     assert config.vector_index_config.quantizer.training_limit == 10000
 
 
+def test_hnsw_with_pathseer_filter_strategy(collection_factory: CollectionFactory) -> None:
+    dummy = collection_factory("dummy")
+    if dummy._connection._weaviate_version.is_lower_than(1, 40, 0):
+        pytest.skip(
+            "pathseer filter strategy is not supported in Weaviate versions lower than 1.40.0"
+        )
+
+    collection = collection_factory(
+        vector_index_config=Configure.VectorIndex.hnsw(
+            filter_strategy=wvc.config.VectorFilterStrategy.PATHSEER,
+        ),
+    )
+
+    config = collection.config.get()
+    assert isinstance(config.vector_index_config, _VectorIndexConfigHNSW)
+    assert config.vector_index_config.filter_strategy == wvc.config.VectorFilterStrategy.PATHSEER
+
+    collection.config.update(
+        vector_index_config=Reconfigure.VectorIndex.hnsw(
+            filter_strategy=wvc.config.VectorFilterStrategy.ACORN,
+        ),
+    )
+    config = collection.config.get()
+    assert isinstance(config.vector_index_config, _VectorIndexConfigHNSW)
+    assert config.vector_index_config.filter_strategy == wvc.config.VectorFilterStrategy.ACORN
+
+    collection.config.update(
+        vector_index_config=Reconfigure.VectorIndex.hnsw(
+            filter_strategy=wvc.config.VectorFilterStrategy.PATHSEER,
+        ),
+    )
+    config = collection.config.get()
+    assert isinstance(config.vector_index_config, _VectorIndexConfigHNSW)
+    assert config.vector_index_config.filter_strategy == wvc.config.VectorFilterStrategy.PATHSEER
+
+
 @pytest.mark.parametrize(
     "vector_index_config",
     [
diff --git a/test/collection/test_config.py b/test/collection/test_config.py
index 7ff50c847..f8d952aa9 100644
--- a/test/collection/test_config.py
+++ b/test/collection/test_config.py
@@ -22,6 +22,7 @@
     _VectorizerConfigCreate,
     _ReplicationConfigCreate,
     ReplicationDeletionStrategy,
+    VectorFilterStrategy,
 )
 from weaviate.collections.classes.config_named_vectors import _NamedVectorConfigCreate
 from weaviate.collections.classes.config_vectorizers import (
@@ -1664,6 +1665,16 @@ def test_vector_config_hnsw_rq4c() -> None:
     assert vi_dict["rq"]["trainingLimit"] == 5012
 
 
+def test_vector_config_hnsw_pathseer_filter_strategy() -> None:
+    vector_index = Configure.VectorIndex.hnsw(
+        filter_strategy=VectorFilterStrategy.PATHSEER,
+    )
+
+    vi_dict = vector_index._to_dict()
+
+    assert vi_dict["filterStrategy"] == "pathseer"
+
+
 def test_vector_config_flat_pq() -> None:
     vector_index = Configure.VectorIndex.flat(
         distance_metric=VectorDistances.DOT,
diff --git a/weaviate/collections/classes/config_vector_index.py b/weaviate/collections/classes/config_vector_index.py
index cc9c74994..4e6ea3cc7 100644
--- a/weaviate/collections/classes/config_vector_index.py
+++ b/weaviate/collections/classes/config_vector_index.py
@@ -22,10 +22,12 @@ class VectorFilterStrategy(str, Enum):
     Attributes:
         SWEEPING: Do normal ANN search and skip nodes.
         ACORN: Multi-hop search to find new candidates matching the filter.
+        PATHSEER: Adaptive search that decides per query between sweeping and multi-hop candidate discovery.
     """
 
     SWEEPING = "sweeping"
     ACORN = "acorn"
+    PATHSEER = "pathseer"
 
 
 class VectorIndexType(str, Enum):