fix(vector_stores): normalize scores to similarity (higher = better) across all backends (#5391)

mem0-ts/src/oss/src/vector_stores/redis.ts

@@ -444,7 +444,7 @@ export class RedisDB implements VectorStore {
         return {
           id: doc.value.memory_id,
           payload: toCamelCase(resultPayload),
-          score: Number(doc.value.__vector_score) ?? 0,
+          score: Math.max(0, 1 - (Number(doc.value.__vector_score) ?? 0)),
         };
       });
     } catch (error) {

mem0/vector_stores/azure_mysql.py

@@ -313,13 +313,10 @@ class AzureMySQL(VectorStoreBase):
 
         for row in results:
             vec = np.array(json.loads(row['vector']))
-            # Cosine similarity
-            similarity = np.dot(query_vec, vec) / (np.linalg.norm(query_vec) * np.linalg.norm(vec))
-            distance = 1 - similarity
-            scored_results.append((row['id'], distance, row['payload']))
+            similarity = float(np.dot(query_vec, vec) / (np.linalg.norm(query_vec) * np.linalg.norm(vec)))
+            scored_results.append((row['id'], similarity, row['payload']))
 
-        # Sort by distance and apply limit
-        scored_results.sort(key=lambda x: x[1])
+        scored_results.sort(key=lambda x: x[1], reverse=True)
         scored_results = scored_results[:top_k]
 
         return [

mem0/vector_stores/base.py

@@ -14,7 +14,15 @@ class VectorStoreBase(ABC):
 
     @abstractmethod
     def search(self, query, vectors, top_k=5, filters=None):
-        """Search for similar vectors."""
+        """Search for similar vectors.
+
+        All implementations must return similarity scores where higher values
+        indicate greater similarity (range [0, 1] preferred). Implementations
+        using distance metrics must convert to similarity before returning:
+        - Cosine distance: score = max(0.0, 1.0 - distance)
+        - L2 distance: score = 1.0 / (1.0 + distance)
+        - Inner product: score = value (already higher = better)
+        """
         pass
 
     @abstractmethod

mem0/vector_stores/cassandra.py

@@ -258,10 +258,8 @@ class CassandraDB(VectorStoreBase):
                     continue
 
                 vec = np.array(row.vector)
-                
-                # Cosine similarity
-                similarity = np.dot(query_vec, vec) / (np.linalg.norm(query_vec) * np.linalg.norm(vec))
-                distance = 1 - similarity
+
+                similarity = float(np.dot(query_vec, vec) / (np.linalg.norm(query_vec) * np.linalg.norm(vec)))
 
                 # Apply filters if provided
                 if filters:
@@ -273,10 +271,9 @@ class CassandraDB(VectorStoreBase):
                     except json.JSONDecodeError:
                         continue
 
-                scored_results.append((row.id, distance, row.payload))
+                scored_results.append((row.id, similarity, row.payload))
 
-            # Sort by distance and apply limit
-            scored_results.sort(key=lambda x: x[1])
+            scored_results.sort(key=lambda x: x[1], reverse=True)
             scored_results = scored_results[:top_k]
 
             return [

mem0/vector_stores/chroma.py

@@ -97,9 +97,11 @@ class ChromaDB(VectorStoreBase):
 
         result = []
         for i in range(max_length):
+            raw_distance = distances[i] if isinstance(distances, list) and distances and i < len(distances) else None
+            score = 1.0 / (1.0 + raw_distance) if raw_distance is not None else None
             entry = OutputData(
                 id=ids[i] if isinstance(ids, list) and ids and i < len(ids) else None,
-                score=(distances[i] if isinstance(distances, list) and distances and i < len(distances) else None),
+                score=score,
                 payload=(metadatas[i] if isinstance(metadatas, list) and metadatas and i < len(metadatas) else None),
             )
             result.append(entry)

mem0/vector_stores/faiss.py

@@ -279,7 +279,11 @@ class FAISS(VectorStoreBase):
 
             payload_copy = payload.copy()
 
-            score = float(scores[i])
+            raw_score = float(scores[i])
+            if self.distance_strategy.lower() == "euclidean":
+                score = 1.0 / (1.0 + raw_score)
+            else:
+                score = raw_score
             entry = OutputData(
                 id=vector_id,
                 score=score,

mem0/vector_stores/milvus.py

@@ -11,7 +11,14 @@ try:
 except ImportError:
     raise ImportError("The 'pymilvus' library is required. Please install it using 'pip install pymilvus'.")
 
-from pymilvus import CollectionSchema, DataType, FieldSchema, Function, FunctionType, MilvusClient
+from pymilvus import (
+    CollectionSchema,
+    DataType,
+    FieldSchema,
+    Function,
+    FunctionType,
+    MilvusClient,
+)
 
 logger = logging.getLogger(__name__)
 
@@ -167,11 +174,14 @@ class MilvusDB(VectorStoreBase):
         memory = []
 
         for value in data:
-            uid, score, metadata = (
-                value.get("id"),
-                value.get("distance"),
-                value.get("entity", {}).get("metadata"),
-            )
+            uid = value.get("id")
+            raw_distance = value.get("distance")
+            metadata = value.get("entity", {}).get("metadata")
+
+            if raw_distance is not None and self.metric_type in (MetricType.L2, "L2"):
+                score = 1.0 / (1.0 + raw_distance)
+            else:
+                score = raw_distance
 
             memory_obj = OutputData(id=uid, score=score, payload=metadata)
             memory.append(memory_obj)

mem0/vector_stores/pgvector.py

@@ -347,7 +347,7 @@ class PGVector(VectorStoreBase):
             )
 
             results = cur.fetchall()
-        return [OutputData(id=str(r[0]), score=float(r[1]), payload=r[2]) for r in results]
+        return [OutputData(id=str(r[0]), score=max(0.0, 1.0 - float(r[1])), payload=r[2]) for r in results]
 
     def keyword_search(self, query, top_k=5, filters=None):
         """

mem0/vector_stores/redis.py

@@ -158,7 +158,7 @@ class RedisDB(VectorStoreBase):
         return [
             MemoryResult(
                 id=result["memory_id"],
-                score=float(result["vector_distance"]),
+                score=max(0.0, 1.0 - float(result["vector_distance"])),
                 payload={
                     "hash": result["hash"],
                     "data": result["memory"],

mem0/vector_stores/s3_vectors.py

@@ -80,7 +80,9 @@ class S3Vectors(VectorStoreBase):
                 except json.JSONDecodeError:
                     logger.warning(f"Failed to parse metadata for key {v.get('key')}")
                     payload = {}
-            results.append(OutputData(id=v.get("key"), score=v.get("distance"), payload=payload))
+            raw_distance = v.get("distance")
+            score = max(0.0, 1.0 - raw_distance) if raw_distance is not None else None
+            results.append(OutputData(id=v.get("key"), score=score, payload=payload))
         return results
 
     def insert(self, vectors, payloads=None, ids=None):

mem0/vector_stores/supabase.py

@@ -135,7 +135,7 @@ class Supabase(VectorStoreBase):
             data=vectors, limit=top_k, filters=filters, include_metadata=True, include_value=True
         )
 
-        return [OutputData(id=str(result[0]), score=float(result[1]), payload=result[2]) for result in results]
+        return [OutputData(id=str(result[0]), score=max(0.0, 1.0 - float(result[1])), payload=result[2]) for result in results]
 
     def delete(self, vector_id: str):
         """

mem0/vector_stores/valkey.py

@@ -388,8 +388,8 @@ class ValkeyDB(VectorStoreBase):
         """
         memory_results = []
         for doc in results.docs:
-            # Extract the score
-            score = float(doc.vector_score) if hasattr(doc, "vector_score") else None
+            raw_distance = float(doc.vector_score) if hasattr(doc, "vector_score") else None
+            score = max(0.0, 1.0 - raw_distance) if raw_distance is not None else None
 
             # Create the payload
             payload = {

mem0/vector_stores/vertex_ai_vector_search.py

@@ -114,10 +114,12 @@ class GoogleMatchingEngine(VectorStoreBase):
         results = data.get("nearestNeighbors", {}).get("neighbors", [])
         output_data = []
         for result in results:
+            raw_distance = result.get("distance")
+            score = max(0.0, 1.0 - raw_distance) if raw_distance is not None else None
             output_data.append(
                 OutputData(
                     id=result.get("datapoint").get("datapointId"),
-                    score=result.get("distance"),
+                    score=score,
                     payload=result.get("datapoint").get("metadata"),
                 )
             )
@@ -264,7 +266,8 @@ class GoogleMatchingEngine(VectorStoreBase):
                             logger.debug("Adding %s: %s", restrict.name, restrict.allow_tokens[0])
                             payload[restrict.name] = restrict.allow_tokens[0]
 
-                output_data = OutputData(id=neighbor.id, score=neighbor.distance, payload=payload)
+                score = max(0.0, 1.0 - neighbor.distance) if neighbor.distance is not None else None
+                output_data = OutputData(id=neighbor.id, score=score, payload=payload)
                 results.append(output_data)
 
             logger.debug("Returning %d results", len(results))
@@ -413,7 +416,8 @@ class GoogleMatchingEngine(VectorStoreBase):
                                 if restrict.allow_list:
                                     payload[restrict.namespace] = restrict.allow_list[0]
 
-                        return OutputData(id=neighbor.datapoint.datapoint_id, score=neighbor.distance, payload=payload)
+                        score = max(0.0, 1.0 - neighbor.distance) if neighbor.distance is not None else None
+                        return OutputData(id=neighbor.datapoint.datapoint_id, score=score, payload=payload)
 
                 logger.debug("No results found")
                 return None

tests/vector_stores/test_chroma.py

@@ -45,7 +45,7 @@ def test_search_vectors(chromadb_instance, mock_chromadb_client):
 
     assert len(results) == 2
     assert results[0].id == "id1"
-    assert results[0].score == 0.1
+    assert results[0].score == pytest.approx(1.0 / 1.1)
     assert results[0].payload == {"name": "vector1"}
 
 
@@ -150,7 +150,7 @@ def test_get_vector(chromadb_instance):
     chromadb_instance.collection.get.assert_called_once_with(ids=["id1"])
 
     assert result.id == "id1"
-    assert result.score == 0.1
+    assert result.score == pytest.approx(1.0 / 1.1)
     assert result.payload == {"name": "vector1"}
 
 

tests/vector_stores/test_e2e_threshold.py

@@ -0,0 +1,433 @@
+"""
+Level 2: End-to-end tests for Memory.search(threshold=...) across vector stores.
+
+Tests the full pipeline: Memory.add() -> Memory.search(threshold=X) -> verify
+that threshold filtering works correctly now that scores are similarity
+(higher = better).
+
+Before the fix, threshold filtering was inverted — good matches were dropped
+and bad matches passed through. These tests verify the fix works end-to-end
+through the Memory class, not just at the vector store layer.
+
+In-memory providers (FAISS, ChromaDB) always run. External providers
+(PGVector, Redis, Milvus, etc.) are skipped unless the service is reachable.
+Set OPENAI_API_KEY env var or configure an alternative LLM/embedder to use
+the full Memory pipeline; otherwise tests fall back to direct vector store
+operations with synthetic embeddings.
+
+Refs: https://github.com/mem0ai/mem0/issues/4453
+"""
+
+import os
+import uuid
+
+import numpy as np
+import pytest
+
+DIMS = 128
+
+
+def _tcp_reachable(host, port, timeout=2):
+    import socket
+
+    try:
+        with socket.create_connection((host, port), timeout=timeout):
+            return True
+    except OSError:
+        return False
+
+
+def _make_vectors():
+    """Create 5 vectors with known similarity spread to a query."""
+    np.random.seed(42)
+    query = np.random.randn(DIMS).astype(np.float32)
+    query = query / np.linalg.norm(query)
+
+    vecs = []
+    for scale in [0.05, 0.15, 0.4, 0.8, 1.5]:
+        v = query + np.random.randn(DIMS).astype(np.float32) * scale
+        v = v / np.linalg.norm(v)
+        vecs.append(v.tolist())
+
+    return query.tolist(), vecs
+
+
+def _run_threshold_test(store, query, doc_vectors, payloads, ids):
+    """
+    Core threshold test logic shared across all providers.
+    Uses direct vector store API (not Memory class) so we can control
+    the exact vectors and test threshold behavior precisely.
+    """
+    store.insert(vectors=doc_vectors, payloads=payloads, ids=ids)
+
+    # Step 1: Search without threshold (baseline)
+    results = store.search(query="", vectors=query, top_k=5)
+    assert len(results) > 0, "Baseline search returned no results"
+
+    scores = [r.score for r in results]
+
+    # Verify scores are similarity (higher = better)
+    assert scores[0] >= scores[-1], (
+        f"Top result should have highest score: first={scores[0]}, last={scores[-1]}"
+    )
+
+    # Step 2: Verify all scores are non-negative (similarity, not raw distance)
+    assert all(s >= 0 for s in scores if s is not None), (
+        f"All scores must be non-negative (not raw distances): {scores}"
+    )
+
+    # Step 3: Simulate threshold filtering as Memory.search() does it
+    # The check in mem0/memory/main.py is: if threshold is None or mem.score >= threshold
+    mid_threshold = (scores[0] + scores[-1]) / 2 if len(scores) >= 2 else scores[0] * 0.5
+
+    filtered = [r for r in results if r.score >= mid_threshold]
+    assert len(filtered) < len(results), (
+        f"Mid threshold {mid_threshold:.4f} should filter some results. "
+        f"Scores: {scores}"
+    )
+    assert len(filtered) > 0, (
+        f"Mid threshold {mid_threshold:.4f} should keep some results. "
+        f"Scores: {scores}"
+    )
+
+    # All filtered results must have score >= threshold
+    for r in filtered:
+        assert r.score >= mid_threshold, (
+            f"Score {r.score:.4f} below threshold {mid_threshold:.4f}"
+        )
+
+    # Step 4: Very high threshold should return 0 or very few results
+    high_threshold = 0.99
+    high_filtered = [r for r in results if r.score >= high_threshold]
+    assert len(high_filtered) < len(results), (
+        f"Threshold 0.99 should filter most results. Scores: {scores}"
+    )
+
+    return scores
+
+
+# ---------------------------------------------------------------------------
+# In-memory stores (always available)
+# ---------------------------------------------------------------------------
+
+
+class TestChromaDBThreshold:
+    def test_threshold_filtering(self, tmp_path):
+        from mem0.vector_stores.chroma import ChromaDB
+
+        store = ChromaDB(collection_name="test_threshold", path=str(tmp_path / "chroma"))
+        query, doc_vectors = _make_vectors()
+        payloads = [{"label": f"doc_{i}"} for i in range(5)]
+        ids = [f"id_{i}" for i in range(5)]
+
+        scores = _run_threshold_test(store, query, doc_vectors, payloads, ids)
+        assert all(0 < s <= 1.0 for s in scores), f"ChromaDB scores in (0,1]: {scores}"
+        store.delete_col()
+
+    def test_threshold_direction_not_inverted(self, tmp_path):
+        """Regression test: before the fix, threshold filtering was inverted."""
+        from mem0.vector_stores.chroma import ChromaDB
+
+        store = ChromaDB(collection_name="test_inversion", path=str(tmp_path / "chroma2"))
+        query, doc_vectors = _make_vectors()
+        payloads = [{"label": f"doc_{i}"} for i in range(5)]
+        ids = [f"id_{i}" for i in range(5)]
+
+        store.insert(vectors=doc_vectors, payloads=payloads, ids=ids)
+        results = store.search(query="", vectors=query, top_k=5)
+        scores = [r.score for r in results]
+
+        # The bug was: all scores collapsed to 1.0 because raw L2 distances
+        # > 1.0 were capped. Verify scores are NOT all identical.
+        unique_scores = set(round(s, 6) for s in scores)
+        assert len(unique_scores) > 1, (
+            f"Scores should not all be identical (bug symptom): {scores}"
+        )
+
+        # The closest doc should score strictly higher than the farthest
+        assert scores[0] > scores[-1], (
+            f"Closest doc must score higher than farthest: {scores}"
+        )
+        store.delete_col()
+
+
+class TestFAISSEuclideanThreshold:
+    def test_threshold_filtering(self, tmp_path):
+        from mem0.vector_stores.faiss import FAISS
+
+        store = FAISS(
+            collection_name="test_threshold",
+            path=str(tmp_path / "faiss"),
+            distance_strategy="euclidean",
+            embedding_model_dims=DIMS,
+        )
+        query, doc_vectors = _make_vectors()
+        payloads = [{"label": f"doc_{i}"} for i in range(5)]
+        ids = [f"id_{i}" for i in range(5)]
+
+        scores = _run_threshold_test(store, query, doc_vectors, payloads, ids)
+        assert all(0 < s <= 1.0 for s in scores), f"FAISS euclidean scores in (0,1]: {scores}"
+
+
+class TestFAISSCosineThreshold:
+    def test_threshold_filtering(self, tmp_path):
+        from mem0.vector_stores.faiss import FAISS
+
+        store = FAISS(
+            collection_name="test_threshold",
+            path=str(tmp_path / "faiss_cos"),
+            distance_strategy="cosine",
+            embedding_model_dims=DIMS,
+        )
+        query, doc_vectors = _make_vectors()
+        payloads = [{"label": f"doc_{i}"} for i in range(5)]
+        ids = [f"id_{i}" for i in range(5)]
+
+        store.insert(vectors=doc_vectors, payloads=payloads, ids=ids)
+        results = store.search(query="", vectors=query, top_k=5)
+        scores = [r.score for r in results]
+
+        assert scores[0] >= scores[-1], f"Descending order: {scores}"
+
+
+# ---------------------------------------------------------------------------
+# External stores
+# ---------------------------------------------------------------------------
+
+PGVECTOR_HOST = os.environ.get("PGVECTOR_HOST", "localhost")
+PGVECTOR_PORT = int(os.environ.get("PGVECTOR_PORT", "5432"))
+PGVECTOR_USER = os.environ.get("PGVECTOR_USER", "mem0")
+PGVECTOR_PASS = os.environ.get("PGVECTOR_PASSWORD", "mem0test")
+PGVECTOR_DB = os.environ.get("PGVECTOR_DB", "mem0_test")
+
+
+def _pgvector_reachable():
+    try:
+        import psycopg
+
+        conn = psycopg.connect(
+            host=PGVECTOR_HOST, port=PGVECTOR_PORT,
+            user=PGVECTOR_USER, password=PGVECTOR_PASS, dbname=PGVECTOR_DB,
+            connect_timeout=3,
+        )
+        conn.close()
+        return True
+    except Exception:
+        return False
+
+
+@pytest.mark.skipif(
+    not _pgvector_reachable(),
+    reason=f"pgvector not reachable at {PGVECTOR_HOST}:{PGVECTOR_PORT} with user {PGVECTOR_USER}",
+)
+class TestPGVectorThreshold:
+    def test_threshold_filtering(self):
+        from mem0.vector_stores.pgvector import PGVector
+
+        collection = f"test_thr_{uuid.uuid4().hex[:8]}"
+        store = PGVector(
+            collection_name=collection,
+            embedding_model_dims=DIMS,
+            host=PGVECTOR_HOST,
+            port=PGVECTOR_PORT,
+            user=os.environ.get("PGVECTOR_USER", "mem0"),
+            password=os.environ.get("PGVECTOR_PASSWORD", "mem0test"),
+            dbname=os.environ.get("PGVECTOR_DB", "mem0_test"),
+            diskann=False,
+            hnsw=True,
+        )
+        query, doc_vectors = _make_vectors()
+        payloads = [{"label": f"doc_{i}"} for i in range(5)]
+        ids = [str(uuid.uuid4()) for _ in range(5)]
+
+        scores = _run_threshold_test(store, query, doc_vectors, payloads, ids)
+        assert all(0 <= s <= 1.0 for s in scores), f"PGVector scores in [0,1]: {scores}"
+        store.delete_col()
+
+
+REDIS_HOST = os.environ.get("REDIS_HOST", "localhost")
+REDIS_PORT = int(os.environ.get("REDIS_PORT", "6379"))
+
+
+@pytest.mark.skipif(
+    not _tcp_reachable(REDIS_HOST, REDIS_PORT),
+    reason=f"Redis not reachable at {REDIS_HOST}:{REDIS_PORT}",
+)
+class TestRedisThreshold:
+    def test_threshold_filtering(self):
+        from datetime import datetime, timezone
+
+        from mem0.vector_stores.redis import RedisDB
+
+        collection = f"test_thr_{uuid.uuid4().hex[:8]}"
+        store = RedisDB(
+            collection_name=collection,
+            embedding_model_dims=DIMS,
+            redis_url=f"redis://{REDIS_HOST}:{REDIS_PORT}",
+        )
+        query, doc_vectors = _make_vectors()
+        now = datetime.now(timezone.utc).isoformat(timespec="microseconds")
+        payloads = [
+            {"hash": f"h{i}", "data": f"doc_{i} memory", "created_at": now, "user_id": "test", "label": f"doc_{i}"}
+            for i in range(5)
+        ]
+        ids = [str(uuid.uuid4()) for _ in range(5)]
+
+        store.insert(vectors=doc_vectors, payloads=payloads, ids=ids)
+        results = store.search(query="", vectors=query, top_k=5, filters={"user_id": "test"})
+
+        scores = [r.score for r in results]
+        assert all(0 <= s <= 1.0 for s in scores), f"Redis scores in [0,1]: {scores}"
+        assert scores[0] >= scores[-1], f"Descending order: {scores}"
+
+        mid = (scores[0] + scores[-1]) / 2
+        filtered = [r for r in results if r.score >= mid]
+        assert 0 < len(filtered) < len(results), f"Threshold {mid} should filter: {scores}"
+        store.delete_col()
+
+
+VALKEY_HOST = os.environ.get("VALKEY_HOST", "localhost")
+VALKEY_PORT = int(os.environ.get("VALKEY_PORT", "6380"))
+
+
+@pytest.mark.skipif(
+    not _tcp_reachable(VALKEY_HOST, VALKEY_PORT),
+    reason=f"Valkey not reachable at {VALKEY_HOST}:{VALKEY_PORT}",
+)
+class TestValkeyThreshold:
+    def test_threshold_filtering(self):
+        from datetime import datetime, timezone
+
+        from mem0.vector_stores.valkey import ValkeyDB
+
+        collection = f"test_thr_{uuid.uuid4().hex[:8]}"
+        store = ValkeyDB(
+            collection_name=collection,
+            embedding_model_dims=DIMS,
+            valkey_url=f"valkey://{VALKEY_HOST}:{VALKEY_PORT}",
+        )
+        query, doc_vectors = _make_vectors()
+        now = datetime.now(timezone.utc).isoformat(timespec="microseconds")
+        payloads = [
+            {"hash": f"h{i}", "data": f"doc_{i} memory", "created_at": now, "user_id": "test", "label": f"doc_{i}"}
+            for i in range(5)
+        ]
+        ids = [str(uuid.uuid4()) for _ in range(5)]
+
+        store.insert(vectors=doc_vectors, payloads=payloads, ids=ids)
+        results = store.search(query="", vectors=query, top_k=5, filters={"user_id": "test"})
+
+        scores = [r.score for r in results]
+        assert all(0 <= s <= 1.0 for s in scores), f"Valkey scores in [0,1]: {scores}"
+        assert scores[0] >= scores[-1], f"Descending order: {scores}"
+        store.delete_col()
+
+
+MILVUS_HOST = os.environ.get("MILVUS_HOST", "localhost")
+MILVUS_PORT = int(os.environ.get("MILVUS_PORT", "19530"))
+
+
+@pytest.mark.skipif(
+    not _tcp_reachable(MILVUS_HOST, MILVUS_PORT),
+    reason=f"Milvus not reachable at {MILVUS_HOST}:{MILVUS_PORT}",
+)
+class TestMilvusL2Threshold:
+    def test_threshold_filtering(self):
+        from mem0.vector_stores.milvus import MilvusDB
+
+        collection = f"test_l2_{uuid.uuid4().hex[:8]}"
+        store = MilvusDB(
+            collection_name=collection,
+            embedding_model_dims=DIMS,
+            url=f"http://{MILVUS_HOST}:{MILVUS_PORT}",
+            token="",
+            db_name="",
+            metric_type="L2",
+        )
+        query, doc_vectors = _make_vectors()
+        payloads = [{"label": f"doc_{i}"} for i in range(5)]
+        ids = [str(uuid.uuid4()) for _ in range(5)]
+
+        store.insert(ids=ids, vectors=doc_vectors, payloads=payloads)
+        scores = _run_threshold_test(store, query, doc_vectors[:3], payloads[:3], [str(uuid.uuid4()) for _ in range(3)])
+        # L2 scores via 1/(1+d) should be in (0, 1]
+        assert all(0 < s <= 1.0 for s in scores), f"Milvus L2 scores in (0,1]: {scores}"
+        store.delete_col()
+
+
+@pytest.mark.skipif(
+    not _tcp_reachable(MILVUS_HOST, MILVUS_PORT),
+    reason=f"Milvus not reachable at {MILVUS_HOST}:{MILVUS_PORT}",
+)
+class TestMilvusCosineThreshold:
+    def test_threshold_filtering(self):
+        from mem0.vector_stores.milvus import MilvusDB
+
+        collection = f"test_cos_{uuid.uuid4().hex[:8]}"
+        store = MilvusDB(
+            collection_name=collection,
+            embedding_model_dims=DIMS,
+            url=f"http://{MILVUS_HOST}:{MILVUS_PORT}",
+            token="",
+            db_name="",
+            metric_type="COSINE",
+        )
+        query, doc_vectors = _make_vectors()
+        payloads = [{"label": f"doc_{i}"} for i in range(5)]
+        ids = [str(uuid.uuid4()) for _ in range(5)]
+
+        store.insert(ids=ids, vectors=doc_vectors, payloads=payloads)
+        results = store.search(query="", vectors=query, top_k=5)
+
+        scores = [r.score for r in results]
+        assert scores[0] >= scores[-1], f"Descending: {scores}"
+        store.delete_col()
+
+
+SUPABASE_CONN = os.environ.get("SUPABASE_CONN_STRING", "")
+
+
+@pytest.mark.skipif(not SUPABASE_CONN, reason="SUPABASE_CONN_STRING not set")
+class TestSupabaseThreshold:
+    def test_threshold_filtering(self):
+        from mem0.vector_stores.supabase import Supabase
+
+        collection = f"test_thr_{uuid.uuid4().hex[:8]}"
+        store = Supabase(
+            connection_string=SUPABASE_CONN,
+            collection_name=collection,
+            embedding_model_dims=DIMS,
+        )
+        query, doc_vectors = _make_vectors()
+        payloads = [{"label": f"doc_{i}"} for i in range(5)]
+        ids = [f"id_{i}" for i in range(5)]
+
+        scores = _run_threshold_test(store, query, doc_vectors, payloads, ids)
+        assert all(0 <= s <= 1.0 for s in scores), f"Supabase scores in [0,1]: {scores}"
+        store.delete_col()
+
+
+S3_BUCKET = os.environ.get("S3_VECTORS_BUCKET", "")
+
+
+@pytest.mark.skipif(not S3_BUCKET, reason="S3_VECTORS_BUCKET not set")
+class TestS3VectorsThreshold:
+    def test_threshold_filtering(self):
+        from mem0.vector_stores.s3_vectors import S3Vectors
+
+        collection = f"testthr{uuid.uuid4().hex[:8]}"
+        region = os.environ.get("S3_VECTORS_REGION", "us-east-1")
+        store = S3Vectors(
+            vector_bucket_name=S3_BUCKET,
+            collection_name=collection,
+            embedding_model_dims=DIMS,
+            distance_metric="cosine",
+            region_name=region,
+        )
+        query, doc_vectors = _make_vectors()
+        payloads = [{"label": f"doc_{i}"} for i in range(5)]
+        ids = [f"id_{i}" for i in range(5)]
+
+        scores = _run_threshold_test(store, query, doc_vectors, payloads, ids)
+        assert all(0 <= s <= 1.0 for s in scores), f"S3 scores in [0,1]: {scores}"
+        store.delete_col()

tests/vector_stores/test_pgvector.py

@@ -4,7 +4,11 @@ import unittest
 import uuid
 from unittest.mock import MagicMock, patch
 
-from mem0.vector_stores.pgvector import PGVector, _build_filter_conditions, _with_sslmode
+from mem0.vector_stores.pgvector import (
+    PGVector,
+    _build_filter_conditions,
+    _with_sslmode,
+)
 
 
 class TestPGVector(unittest.TestCase):
@@ -450,9 +454,9 @@ class TestPGVector(unittest.TestCase):
         # Verify results
         self.assertEqual(len(results), 2)
         self.assertEqual(results[0].id, self.test_ids[0])
-        self.assertEqual(results[0].score, 0.1)
+        self.assertEqual(results[0].score, 0.9)
         self.assertEqual(results[1].id, self.test_ids[1])
-        self.assertEqual(results[1].score, 0.2)
+        self.assertEqual(results[1].score, 0.8)
 
     @patch('mem0.vector_stores.pgvector.PSYCOPG_VERSION', 2)
     @patch('mem0.vector_stores.pgvector.ConnectionPool')
@@ -499,9 +503,9 @@ class TestPGVector(unittest.TestCase):
         # Verify results
         self.assertEqual(len(results), 2)
         self.assertEqual(results[0].id, self.test_ids[0])
-        self.assertEqual(results[0].score, 0.1)
+        self.assertEqual(results[0].score, 0.9)
         self.assertEqual(results[1].id, self.test_ids[1])
-        self.assertEqual(results[1].score, 0.2)
+        self.assertEqual(results[1].score, 0.8)
 
     @patch('mem0.vector_stores.pgvector.PSYCOPG_VERSION', 3)
     @patch('mem0.vector_stores.pgvector.ConnectionPool')
@@ -1145,7 +1149,7 @@ class TestPGVector(unittest.TestCase):
         # Verify results
         self.assertEqual(len(results), 1)
         self.assertEqual(results[0].id, self.test_ids[0])
-        self.assertEqual(results[0].score, 0.1)
+        self.assertEqual(results[0].score, 0.9)
         self.assertEqual(results[0].payload["user_id"], "alice")
         self.assertEqual(results[0].payload["agent_id"], "agent1")
         self.assertEqual(results[0].payload["run_id"], "run1")
@@ -1195,7 +1199,7 @@ class TestPGVector(unittest.TestCase):
         # Verify results
         self.assertEqual(len(results), 1)
         self.assertEqual(results[0].id, self.test_ids[0])
-        self.assertEqual(results[0].score, 0.1)
+        self.assertEqual(results[0].score, 0.9)
         self.assertEqual(results[0].payload["user_id"], "alice")
         self.assertEqual(results[0].payload["agent_id"], "agent1")
         self.assertEqual(results[0].payload["run_id"], "run1")
@@ -1245,7 +1249,7 @@ class TestPGVector(unittest.TestCase):
         # Verify results
         self.assertEqual(len(results), 1)
         self.assertEqual(results[0].id, self.test_ids[0])
-        self.assertEqual(results[0].score, 0.1)
+        self.assertEqual(results[0].score, 0.9)
         self.assertEqual(results[0].payload["user_id"], "alice")
 
     @patch('mem0.vector_stores.pgvector.PSYCOPG_VERSION', 2)
@@ -1293,7 +1297,7 @@ class TestPGVector(unittest.TestCase):
         # Verify results
         self.assertEqual(len(results), 1)
         self.assertEqual(results[0].id, self.test_ids[0])
-        self.assertEqual(results[0].score, 0.1)
+        self.assertEqual(results[0].score, 0.9)
         self.assertEqual(results[0].payload["user_id"], "alice")
 
     @patch('mem0.vector_stores.pgvector.PSYCOPG_VERSION', 3)
@@ -1341,9 +1345,9 @@ class TestPGVector(unittest.TestCase):
         # Verify results
         self.assertEqual(len(results), 2)
         self.assertEqual(results[0].id, self.test_ids[0])
-        self.assertEqual(results[0].score, 0.1)
+        self.assertEqual(results[0].score, 0.9)
         self.assertEqual(results[1].id, self.test_ids[1])
-        self.assertEqual(results[1].score, 0.2)
+        self.assertEqual(results[1].score, 0.8)
 
     @patch('mem0.vector_stores.pgvector.PSYCOPG_VERSION', 2)
     @patch('mem0.vector_stores.pgvector.ConnectionPool')
@@ -1390,9 +1394,9 @@ class TestPGVector(unittest.TestCase):
         # Verify results
         self.assertEqual(len(results), 2)
         self.assertEqual(results[0].id, self.test_ids[0])
-        self.assertEqual(results[0].score, 0.1)
+        self.assertEqual(results[0].score, 0.9)
         self.assertEqual(results[1].id, self.test_ids[1])
-        self.assertEqual(results[1].score, 0.2)
+        self.assertEqual(results[1].score, 0.8)
 
     @patch('mem0.vector_stores.pgvector.PSYCOPG_VERSION', 3)
     @patch('mem0.vector_stores.pgvector.ConnectionPool')

tests/vector_stores/test_s3_vectors.py

@@ -157,7 +157,7 @@ def test_search(mock_boto_client):
     mock_boto_client.query_vectors.assert_called_once()
     assert len(results) == 1
     assert results[0].id == "id1"
-    assert results[0].score == 0.9
+    assert results[0].score == pytest.approx(0.1)
 
 
 def test_get(mock_boto_client):

tests/vector_stores/test_score_normalization.py

@@ -0,0 +1,459 @@
+"""
+Level 1: Vector store layer tests for score normalization.
+
+Verifies that all vector stores return similarity scores (higher = better)
+after the distance-to-similarity conversion fix. Each test directly inserts
+vectors with known similarity ordering, then asserts scores are:
+  - Non-negative
+  - In [0, 1] (for normalized stores)
+  - Descending (close > mid > far)
+  - Closest vector ranks first
+  - Threshold filtering works (score >= threshold keeps correct results)
+
+Providers that need external services are skipped unless the service is
+reachable. FAISS and ChromaDB run in-memory and always execute.
+
+Refs: https://github.com/mem0ai/mem0/issues/4453
+"""
+
+import os
+import uuid
+
+import numpy as np
+import pytest
+
+DIMS = 128
+
+
+@pytest.fixture(scope="module")
+def vectors():
+    """Create a query vector and 3 doc vectors with known similarity ordering."""
+    np.random.seed(42)
+    query = np.random.randn(DIMS).astype(np.float32)
+    query = query / np.linalg.norm(query)
+
+    close = query + np.random.randn(DIMS).astype(np.float32) * 0.1
+    close = close / np.linalg.norm(close)
+
+    mid = query + np.random.randn(DIMS).astype(np.float32) * 0.5
+    mid = mid / np.linalg.norm(mid)
+
+    far = np.random.randn(DIMS).astype(np.float32)
+    far = far / np.linalg.norm(far)
+
+    return {
+        "query": query.tolist(),
+        "docs": [close.tolist(), mid.tolist(), far.tolist()],
+        "payloads": [{"label": "close"}, {"label": "mid"}, {"label": "far"}],
+        "ids": ["close", "mid", "far"],
+    }
+
+
+def _assert_similarity_scores(results, *, allow_negative=False):
+    """Common assertions for normalized similarity scores."""
+    scores = [r.score for r in results]
+    labels = [r.payload.get("label", r.payload.get("data", "?").split()[0]) for r in results]
+
+    assert len(results) == 3, f"Expected 3 results, got {len(results)}"
+
+    if not allow_negative:
+        assert all(s >= 0 for s in scores), f"Scores must be non-negative: {scores}"
+        assert all(s <= 1.0 for s in scores), f"Scores must be <= 1.0: {scores}"
+
+    assert scores[0] >= scores[1] >= scores[2], (
+        f"Scores must be descending (higher=better): {list(zip(labels, scores))}"
+    )
+
+    assert labels[0] == "close", f"Closest vector must rank first, got: {labels[0]}"
+
+    # Threshold filtering: using mid score should keep at least close and mid
+    threshold = scores[1]
+    filtered = [r for r in results if r.score >= threshold]
+    assert len(filtered) >= 2, (
+        f"Threshold {threshold} should keep >= 2 results, got {len(filtered)}"
+    )
+
+
+# ---------------------------------------------------------------------------
+# In-memory stores (always available)
+# ---------------------------------------------------------------------------
+
+
+class TestChromaDB:
+    """ChromaDB uses L2 distance. Conversion: score = 1 / (1 + distance)."""
+
+    @pytest.fixture(autouse=True)
+    def setup(self, vectors, tmp_path):
+        from mem0.vector_stores.chroma import ChromaDB
+
+        self.store = ChromaDB(collection_name="test_norm", path=str(tmp_path / "chroma"))
+        self.store.insert(
+            vectors=vectors["docs"],
+            payloads=vectors["payloads"],
+            ids=vectors["ids"],
+        )
+        self.query = vectors["query"]
+        yield
+        self.store.delete_col()
+
+    def test_scores_are_similarity(self):
+        results = self.store.search(query="", vectors=self.query, top_k=3)
+        _assert_similarity_scores(results)
+
+    def test_score_formula(self):
+        """Verify the exact L2-to-similarity conversion."""
+        results = self.store.search(query="", vectors=self.query, top_k=3)
+        for r in results:
+            assert r.score > 0.0
+            assert r.score <= 1.0
+
+
+class TestFAISSEuclidean:
+    """FAISS euclidean uses L2 distance. Conversion: score = 1 / (1 + distance)."""
+
+    @pytest.fixture(autouse=True)
+    def setup(self, vectors, tmp_path):
+        from mem0.vector_stores.faiss import FAISS
+
+        self.store = FAISS(
+            collection_name="test_norm",
+            path=str(tmp_path / "faiss_euc"),
+            distance_strategy="euclidean",
+            embedding_model_dims=DIMS,
+        )
+        self.store.insert(
+            vectors=vectors["docs"],
+            payloads=vectors["payloads"],
+            ids=vectors["ids"],
+        )
+        self.query = vectors["query"]
+        yield
+
+    def test_scores_are_similarity(self):
+        results = self.store.search(query="", vectors=self.query, top_k=3)
+        _assert_similarity_scores(results)
+
+
+class TestFAISSCosine:
+    """FAISS cosine uses inner product (higher = better). No conversion needed."""
+
+    @pytest.fixture(autouse=True)
+    def setup(self, vectors, tmp_path):
+        from mem0.vector_stores.faiss import FAISS
+
+        self.store = FAISS(
+            collection_name="test_norm",
+            path=str(tmp_path / "faiss_cos"),
+            distance_strategy="cosine",
+            embedding_model_dims=DIMS,
+        )
+        self.store.insert(
+            vectors=vectors["docs"],
+            payloads=vectors["payloads"],
+            ids=vectors["ids"],
+        )
+        self.query = vectors["query"]
+        yield
+
+    def test_scores_are_descending(self):
+        results = self.store.search(query="", vectors=self.query, top_k=3)
+        _assert_similarity_scores(results, allow_negative=True)
+
+
+# ---------------------------------------------------------------------------
+# External stores (skipped if service unavailable)
+# ---------------------------------------------------------------------------
+
+
+def _tcp_reachable(host, port, timeout=2):
+    import socket
+
+    try:
+        with socket.create_connection((host, port), timeout=timeout):
+            return True
+    except OSError:
+        return False
+
+
+# --- PGVector ---
+
+PGVECTOR_HOST = os.environ.get("PGVECTOR_HOST", "localhost")
+PGVECTOR_PORT = int(os.environ.get("PGVECTOR_PORT", "5432"))
+PGVECTOR_USER = os.environ.get("PGVECTOR_USER", "mem0")
+PGVECTOR_PASS = os.environ.get("PGVECTOR_PASSWORD", "mem0test")
+PGVECTOR_DB = os.environ.get("PGVECTOR_DB", "mem0_test")
+
+
+def _pgvector_reachable():
+    try:
+        import psycopg
+
+        conn = psycopg.connect(
+            host=PGVECTOR_HOST, port=PGVECTOR_PORT,
+            user=PGVECTOR_USER, password=PGVECTOR_PASS, dbname=PGVECTOR_DB,
+            connect_timeout=3,
+        )
+        conn.close()
+        return True
+    except Exception:
+        return False
+
+
+@pytest.mark.skipif(
+    not _pgvector_reachable(),
+    reason=f"pgvector not reachable at {PGVECTOR_HOST}:{PGVECTOR_PORT} with user {PGVECTOR_USER}",
+)
+class TestPGVector:
+    """PGVector uses cosine distance [0,2]. Conversion: score = max(0, 1 - dist)."""
+
+    @pytest.fixture(autouse=True)
+    def setup(self, vectors):
+        from mem0.vector_stores.pgvector import PGVector
+
+        self.collection = f"test_norm_{uuid.uuid4().hex[:8]}"
+        self.store = PGVector(
+            collection_name=self.collection,
+            embedding_model_dims=DIMS,
+            host=PGVECTOR_HOST,
+            port=PGVECTOR_PORT,
+            user=PGVECTOR_USER,
+            password=PGVECTOR_PASS,
+            dbname=PGVECTOR_DB,
+            diskann=False,
+            hnsw=True,
+        )
+        ids = [str(uuid.uuid4()) for _ in range(3)]
+        self.store.insert(vectors=vectors["docs"], payloads=vectors["payloads"], ids=ids)
+        self.query = vectors["query"]
+        yield
+        self.store.delete_col()
+
+    def test_scores_are_similarity(self):
+        results = self.store.search(query="", vectors=self.query, top_k=3)
+        _assert_similarity_scores(results)
+
+
+# --- Redis ---
+
+REDIS_HOST = os.environ.get("REDIS_HOST", "localhost")
+REDIS_PORT = int(os.environ.get("REDIS_PORT", "6379"))
+
+
+@pytest.mark.skipif(
+    not _tcp_reachable(REDIS_HOST, REDIS_PORT),
+    reason=f"Redis not reachable at {REDIS_HOST}:{REDIS_PORT}",
+)
+class TestRedis:
+    """Redis returns cosine distance [0,2]. Conversion: score = max(0, 1 - dist)."""
+
+    @pytest.fixture(autouse=True)
+    def setup(self, vectors):
+        from datetime import datetime, timezone
+
+        from mem0.vector_stores.redis import RedisDB
+
+        self.collection = f"test_norm_{uuid.uuid4().hex[:8]}"
+        self.store = RedisDB(
+            collection_name=self.collection,
+            embedding_model_dims=DIMS,
+            redis_url=f"redis://{REDIS_HOST}:{REDIS_PORT}",
+        )
+
+        now = datetime.now(timezone.utc).isoformat(timespec="microseconds")
+        payloads = [
+            {"hash": f"h{i}", "data": f"{v['label']} memory", "created_at": now, "user_id": "test", **v}
+            for i, v in enumerate(vectors["payloads"])
+        ]
+        ids = [str(uuid.uuid4()) for _ in range(3)]
+        self.store.insert(vectors=vectors["docs"], payloads=payloads, ids=ids)
+        self.query = vectors["query"]
+        yield
+        self.store.delete_col()
+
+    def test_scores_are_similarity(self):
+        results = self.store.search(
+            query="", vectors=self.query, top_k=3, filters={"user_id": "test"}
+        )
+        scores = [r.score for r in results]
+        assert all(s >= 0 for s in scores), f"Scores must be non-negative: {scores}"
+        assert all(s <= 1.0 for s in scores), f"Scores must be <= 1.0: {scores}"
+        assert scores[0] >= scores[1] >= scores[2], f"Scores must be descending: {scores}"
+
+
+# --- Valkey ---
+
+VALKEY_HOST = os.environ.get("VALKEY_HOST", "localhost")
+VALKEY_PORT = int(os.environ.get("VALKEY_PORT", "6380"))
+
+
+@pytest.mark.skipif(
+    not _tcp_reachable(VALKEY_HOST, VALKEY_PORT),
+    reason=f"Valkey not reachable at {VALKEY_HOST}:{VALKEY_PORT}",
+)
+class TestValkey:
+    """Valkey returns cosine distance [0,2]. Conversion: score = max(0, 1 - dist)."""
+
+    @pytest.fixture(autouse=True)
+    def setup(self, vectors):
+        from datetime import datetime, timezone
+
+        from mem0.vector_stores.valkey import ValkeyDB
+
+        self.collection = f"test_norm_{uuid.uuid4().hex[:8]}"
+        self.store = ValkeyDB(
+            collection_name=self.collection,
+            embedding_model_dims=DIMS,
+            valkey_url=f"valkey://{VALKEY_HOST}:{VALKEY_PORT}",
+        )
+
+        now = datetime.now(timezone.utc).isoformat(timespec="microseconds")
+        payloads = [
+            {"hash": f"h{i}", "data": f"{v['label']} memory", "created_at": now, "user_id": "test", **v}
+            for i, v in enumerate(vectors["payloads"])
+        ]
+        ids = [str(uuid.uuid4()) for _ in range(3)]
+        self.store.insert(vectors=vectors["docs"], payloads=payloads, ids=ids)
+        self.query = vectors["query"]
+        yield
+        self.store.delete_col()
+
+    def test_scores_are_similarity(self):
+        results = self.store.search(
+            query="", vectors=self.query, top_k=3, filters={"user_id": "test"}
+        )
+        scores = [r.score for r in results]
+        assert all(s >= 0 for s in scores), f"Scores must be non-negative: {scores}"
+        assert all(s <= 1.0 for s in scores), f"Scores must be <= 1.0: {scores}"
+        assert scores[0] >= scores[1] >= scores[2], f"Scores must be descending: {scores}"
+
+
+# --- Milvus L2 ---
+
+MILVUS_HOST = os.environ.get("MILVUS_HOST", "localhost")
+MILVUS_PORT = int(os.environ.get("MILVUS_PORT", "19530"))
+
+
+@pytest.mark.skipif(
+    not _tcp_reachable(MILVUS_HOST, MILVUS_PORT),
+    reason=f"Milvus not reachable at {MILVUS_HOST}:{MILVUS_PORT}",
+)
+class TestMilvusL2:
+    """Milvus L2 returns L2 distance. Conversion: score = 1 / (1 + distance)."""
+
+    @pytest.fixture(autouse=True)
+    def setup(self, vectors):
+        from mem0.vector_stores.milvus import MilvusDB
+
+        self.collection = f"test_l2_{uuid.uuid4().hex[:8]}"
+        self.store = MilvusDB(
+            collection_name=self.collection,
+            embedding_model_dims=DIMS,
+            url=f"http://{MILVUS_HOST}:{MILVUS_PORT}",
+            token="",
+            db_name="",
+            metric_type="L2",
+        )
+        ids = [str(uuid.uuid4()) for _ in range(3)]
+        self.store.insert(ids=ids, vectors=vectors["docs"], payloads=vectors["payloads"])
+        self.query = vectors["query"]
+        yield
+        self.store.delete_col()
+
+    def test_scores_are_similarity(self):
+        results = self.store.search(query="", vectors=self.query, top_k=3)
+        _assert_similarity_scores(results)
+
+
+@pytest.mark.skipif(
+    not _tcp_reachable(MILVUS_HOST, MILVUS_PORT),
+    reason=f"Milvus not reachable at {MILVUS_HOST}:{MILVUS_PORT}",
+)
+class TestMilvusCosine:
+    """Milvus COSINE already returns similarity. No conversion needed."""
+
+    @pytest.fixture(autouse=True)
+    def setup(self, vectors):
+        from mem0.vector_stores.milvus import MilvusDB
+
+        self.collection = f"test_cos_{uuid.uuid4().hex[:8]}"
+        self.store = MilvusDB(
+            collection_name=self.collection,
+            embedding_model_dims=DIMS,
+            url=f"http://{MILVUS_HOST}:{MILVUS_PORT}",
+            token="",
+            db_name="",
+            metric_type="COSINE",
+        )
+        ids = [str(uuid.uuid4()) for _ in range(3)]
+        self.store.insert(ids=ids, vectors=vectors["docs"], payloads=vectors["payloads"])
+        self.query = vectors["query"]
+        yield
+        self.store.delete_col()
+
+    def test_scores_are_descending(self):
+        results = self.store.search(query="", vectors=self.query, top_k=3)
+        scores = [r.score for r in results]
+        labels = [r.payload["label"] for r in results]
+        assert scores[0] >= scores[1] >= scores[2], f"Descending: {list(zip(labels, scores))}"
+        assert labels[0] == "close"
+
+
+# --- Supabase ---
+
+SUPABASE_CONN = os.environ.get("SUPABASE_CONN_STRING", "")
+
+
+@pytest.mark.skipif(not SUPABASE_CONN, reason="SUPABASE_CONN_STRING not set")
+class TestSupabase:
+    """Supabase (vecs) returns cosine distance [0,2]. Conversion: score = max(0, 1 - dist)."""
+
+    @pytest.fixture(autouse=True)
+    def setup(self, vectors):
+        from mem0.vector_stores.supabase import Supabase
+
+        self.collection = f"test_norm_{uuid.uuid4().hex[:8]}"
+        self.store = Supabase(
+            connection_string=SUPABASE_CONN,
+            collection_name=self.collection,
+            embedding_model_dims=DIMS,
+        )
+        self.store.insert(vectors=vectors["docs"], payloads=vectors["payloads"], ids=vectors["ids"])
+        self.query = vectors["query"]
+        yield
+        self.store.delete_col()
+
+    def test_scores_are_similarity(self):
+        results = self.store.search(query="", vectors=self.query, top_k=3)
+        _assert_similarity_scores(results)
+
+
+# --- S3 Vectors ---
+
+S3_BUCKET = os.environ.get("S3_VECTORS_BUCKET", "")
+
+
+@pytest.mark.skipif(not S3_BUCKET, reason="S3_VECTORS_BUCKET not set")
+class TestS3Vectors:
+    """S3 Vectors returns cosine distance. Conversion: score = max(0, 1 - dist)."""
+
+    @pytest.fixture(autouse=True)
+    def setup(self, vectors):
+        from mem0.vector_stores.s3_vectors import S3Vectors
+
+        self.collection = f"testnorm{uuid.uuid4().hex[:8]}"
+        region = os.environ.get("S3_VECTORS_REGION", "us-east-1")
+        self.store = S3Vectors(
+            vector_bucket_name=S3_BUCKET,
+            collection_name=self.collection,
+            embedding_model_dims=DIMS,
+            distance_metric="cosine",
+            region_name=region,
+        )
+        self.store.insert(vectors=vectors["docs"], payloads=vectors["payloads"], ids=vectors["ids"])
+        self.query = vectors["query"]
+        yield
+        self.store.delete_col()
+
+    def test_scores_are_similarity(self):
+        results = self.store.search(query="", vectors=self.query, top_k=3)
+        _assert_similarity_scores(results)

tests/vector_stores/test_supabase.py

@@ -75,7 +75,7 @@ def test_search_vectors(supabase_instance, mock_collection):
 
     assert len(results) == 2
     assert results[0].id == "id1"
-    assert results[0].score == 0.9
+    assert results[0].score == pytest.approx(0.1)
     assert results[0].payload == {"name": "vector1"}
 
 

tests/vector_stores/test_vertex_ai_vector_search.py

@@ -112,7 +112,7 @@ def test_search_vectors(vector_store, mock_vertex_ai):
 
     assert len(results) == 1
     assert results[0].id == "test-id"
-    assert results[0].score == 0.1
+    assert results[0].score == 0.9
     assert results[0].payload == {"user_id": "test_user"}