diff --git a/litellm/llms/vertex_ai/common_utils.py b/litellm/llms/vertex_ai/common_utils.py
index a42e56ef178..f882a54ae72 100644
--- a/litellm/llms/vertex_ai/common_utils.py
+++ b/litellm/llms/vertex_ai/common_utils.py
@@ -4,7 +4,7 @@ from collections.abc import Callable, Iterable, Mapping, Sequence
 from copy import deepcopy
 from datetime import datetime, timezone
 from enum import Enum
-from functools import lru_cache
+from functools import lru_cache, reduce
 from itertools import accumulate, chain, repeat, takewhile
 from types import MappingProxyType
 from typing import Any, Final, Literal, TypeVar, cast, get_type_hints
@@ -913,22 +913,23 @@ def _root_cannot_be_vertex_parameters(root: Mapping[str, object]) -> bool:
     ) or not _is_absent_or_object_type(root.get("type"))
 
 
-def _resolve_root_ref(
-    schema: Mapping[str, JsonValue], defs: Mapping[str, JsonValue], seen_refs: frozenset[str]
-) -> Mapping[str, JsonValue]:
+def _root_ref_target(schema: Mapping[str, JsonValue], defs: Mapping[str, JsonValue]) -> Mapping[str, JsonValue]:
     match schema.get("$ref"):
-        case str() as ref if ref.startswith(_ROOT_DEFS_REF_PREFIX) and ref not in seen_refs:
+        case str() as ref if ref.startswith(_ROOT_DEFS_REF_PREFIX):
             target: Final = defs.get(ref.removeprefix(_ROOT_DEFS_REF_PREFIX))
-            return _resolve_root_ref(target, defs, seen_refs | {ref}) if isinstance(target, dict) else schema
+            return target if isinstance(target, dict) else schema
         case _:
             return schema
 
 
+def _resolve_root_ref(schema: Mapping[str, JsonValue], defs: Mapping[str, JsonValue]) -> Mapping[str, JsonValue]:
+    resolved: Final = reduce(lambda current, _: _root_ref_target(current, defs), range(len(defs)), schema)
+    return resolved if _root_ref_target(resolved, defs) is resolved else schema
+
+
 def needs_parameters_json_schema(parameters: Mapping[str, JsonValue]) -> bool:
     defs: Final = parameters.get("$defs")
-    return _root_cannot_be_vertex_parameters(
-        _resolve_root_ref(parameters, defs if isinstance(defs, dict) else {}, frozenset())
-    )
+    return _root_cannot_be_vertex_parameters(_resolve_root_ref(parameters, defs if isinstance(defs, dict) else {}))
 
 
 def parameters_json_schema_for(parameters: Mapping[str, object]) -> Mapping[str, JsonValue] | None:
diff --git a/tests/unit/llms/vertex_ai/test_vertex_ai_common_utils.py b/tests/unit/llms/vertex_ai/test_vertex_ai_common_utils.py
index 243dc9fdebd..e389fbb4eea 100644
--- a/tests/unit/llms/vertex_ai/test_vertex_ai_common_utils.py
+++ b/tests/unit/llms/vertex_ai/test_vertex_ai_common_utils.py
@@ -1624,6 +1624,12 @@ def test_map_function_keeps_integer_enum_when_tools_are_reused():
 
 
 _OBJECT_BRANCH: Final = {"type": "object", "properties": {"a": {"type": "string"}}, "required": ["a"]}
+_DEEP_ROOT_REF_CHAIN_LENGTH: Final = 3000
+
+
+def _deep_root_ref_chain(end: Mapping[str, JsonValue]) -> Mapping[str, JsonValue]:
+    links: Final = {f"d{i}": {"$ref": f"#/$defs/d{i + 1}"} for i in range(_DEEP_ROOT_REF_CHAIN_LENGTH)}
+    return {"$ref": "#/$defs/d0", "$defs": {**links, f"d{_DEEP_ROOT_REF_CHAIN_LENGTH}": end}}
 
 
 @pytest.mark.parametrize(
@@ -1649,6 +1655,9 @@ _OBJECT_BRANCH: Final = {"type": "object", "properties": {"a": {"type": "string"
         ({"$ref": "#/$defs/A", "$defs": {"A": {"$ref": "#/$defs/B"}, "B": {"anyOf": [_OBJECT_BRANCH]}}}, True),
         ({"$ref": "#/$defs/A", "$defs": {"A": {"$ref": "#/$defs/B"}, "B": _OBJECT_BRANCH}}, False),
         ({"$ref": "#/$defs/A", "$defs": {"A": {"$ref": "#/$defs/B"}, "B": {"$ref": "#/$defs/A"}}}, False),
+        ({"$ref": "#/$defs/A", "$defs": {"A": {"$ref": "#/$defs/B"}, "B": {"$ref": "#/$defs/A", "anyOf": [_OBJECT_BRANCH]}}}, False),
+        (_deep_root_ref_chain({"anyOf": [_OBJECT_BRANCH]}), True),
+        (_deep_root_ref_chain(_OBJECT_BRANCH), False),
     ],
     ids=[
         "object",
@@ -1671,6 +1680,9 @@ _OBJECT_BRANCH: Final = {"type": "object", "properties": {"a": {"type": "string"
         "chained-root-ref-to-union",
         "chained-root-ref-to-object",
         "cyclic-root-ref",
+        "cyclic-root-ref-through-a-union",
+        "deep-root-ref-chain-to-union",
+        "deep-root-ref-chain-to-object",
     ],
 )
 def test_needs_parameters_json_schema(parameters: Mapping[str, JsonValue], expected: bool) -> None: