diff --git a/litellm/vector_stores/vector_store_registry.py b/litellm/vector_stores/vector_store_registry.py
index b5c19cddee2..e0b536d6c57 100644
--- a/litellm/vector_stores/vector_store_registry.py
+++ b/litellm/vector_stores/vector_store_registry.py
@@ -2,6 +2,7 @@
 import json
 from collections.abc import Mapping
 from datetime import datetime, timezone
+from itertools import chain
 from typing import (
     TYPE_CHECKING,
     Any,  # noqa: TID251  # untyped non_default_params dict is the only source of the unknown key type
@@ -36,8 +37,10 @@ _DB_ROW: Final = TypeAdapter(Mapping[str, object], config=ConfigDict(strict=True
 
 
 class VectorStoreIndexRegistry:
-    def __init__(self, vector_store_indexes: list[LiteLLM_ManagedVectorStoreIndex] = []):
-        self.vector_store_indexes: list[LiteLLM_ManagedVectorStoreIndex] = vector_store_indexes
+    def __init__(self, vector_store_indexes: list[LiteLLM_ManagedVectorStoreIndex] | None = None):
+        self.vector_store_indexes: list[LiteLLM_ManagedVectorStoreIndex] = (
+            vector_store_indexes if vector_store_indexes is not None else []
+        )
 
     def get_vector_store_indexes(self) -> list[LiteLLM_ManagedVectorStoreIndex]:
         """
@@ -109,8 +112,8 @@ class VectorStoreIndexRegistry:
 
 
 class VectorStoreRegistry:
-    def __init__(self, vector_stores: list[LiteLLM_ManagedVectorStore] = []):
-        self.vector_stores: list[LiteLLM_ManagedVectorStore] = vector_stores
+    def __init__(self, vector_stores: list[LiteLLM_ManagedVectorStore] | None = None):
+        self.vector_stores: list[LiteLLM_ManagedVectorStore] = vector_stores if vector_stores is not None else []
         self.vector_store_ids_to_vector_store_map: dict[str, LiteLLM_ManagedVectorStore] = {}
 
     def _extract_tool_params(self, tool: dict) -> VectorStoreToolParams:
@@ -392,17 +395,14 @@ class VectorStoreRegistry:
 
         return vector_stores_to_run
 
-    def _get_vector_store_ids_from_tool_calls(
-        self, tools: list[dict] | None = None, vector_store_ids: list[str] = []
-    ) -> list[str]:
+    def _get_vector_store_ids_from_tool_calls(self, tools: list[dict] | None, vector_store_ids: list[str]) -> list[str]:
         """
         Returns the vector store ids from the tool calls
         """
-        if tools:
-            for tool in tools:
-                if "vector_store_ids" in tool:
-                    vector_store_ids.extend(tool["vector_store_ids"])
-        return vector_store_ids
+        return [
+            *vector_store_ids,
+            *chain.from_iterable(tool["vector_store_ids"] for tool in tools or () if "vector_store_ids" in tool),
+        ]
 
     def load_vector_stores_from_config(self, vector_stores_config: list[dict]):
         """
diff --git a/tests/unit/vector_stores/test_vector_store_registry.py b/tests/unit/vector_stores/test_vector_store_registry.py
index a29ce1463ab..f6c888d20ff 100644
--- a/tests/unit/vector_stores/test_vector_store_registry.py
+++ b/tests/unit/vector_stores/test_vector_store_registry.py
@@ -15,7 +15,11 @@ from datetime import datetime, timezone
 from unittest.mock import AsyncMock, MagicMock
 
 import litellm
-from litellm.types.vector_stores import LiteLLM_ManagedVectorStore
+from litellm.types.vector_stores import (
+    IndexCreateLiteLLMParams,
+    LiteLLM_ManagedVectorStore,
+    LiteLLM_ManagedVectorStoreIndex,
+)
 from litellm.vector_stores.main import search
 from litellm.vector_stores.vector_store_registry import VectorStoreIndexRegistry, VectorStoreRegistry
 
@@ -343,3 +347,30 @@ async def test_vector_store_index_row_without_optional_columns_gets_empty_defaul
 async def test_malformed_vector_store_index_row_from_the_db_raises_a_validation_error(row: object) -> None:
     with pytest.raises(ValidationError):
         await VectorStoreIndexRegistry.get_vector_store_indexes_from_db(_database_listing_index_rows([row]))
+
+
+class TestRegistriesDoNotShareDefaultState:
+    def test_adding_to_one_registry_leaves_the_next_one_empty(self):
+        VectorStoreRegistry().add_vector_store_to_registry(
+            LiteLLM_ManagedVectorStore(vector_store_id="vs-leak", custom_llm_provider="bedrock")
+        )
+        assert VectorStoreRegistry().vector_stores == []
+
+    def test_upserting_into_one_index_registry_leaves_the_next_one_empty(self):
+        VectorStoreIndexRegistry().upsert_vector_store_index(
+            LiteLLM_ManagedVectorStoreIndex(
+                id="idx-leak",
+                index_name="leak",
+                litellm_params=IndexCreateLiteLLMParams(vector_store_index="vs-leak", vector_store_name="leak"),
+            )
+        )
+        assert VectorStoreIndexRegistry().get_vector_store_indexes() == []
+
+
+def test_vector_store_ids_to_run_merge_the_param_and_tools_once_per_request():
+    registry: Final = VectorStoreRegistry()
+    first: Final = registry.get_vector_store_ids_to_run(
+        {"vector_store_ids": ["vs-a"]}, tools=[{"type": "file_search", "vector_store_ids": ["vs-b", "vs-a"]}]
+    )
+    second: Final = registry.get_vector_store_ids_to_run({}, tools=[{"type": "file_search", "vector_store_ids": ["vs-c"]}])
+    assert (first, second) == (["vs-a", "vs-b"], ["vs-c"])