diff --git a/litellm/llms/openai/common_utils.py b/litellm/llms/openai/common_utils.py
index 5f9559df77..28de9f1303 100644
--- a/litellm/llms/openai/common_utils.py
+++ b/litellm/llms/openai/common_utils.py
@@ -3,9 +3,10 @@ Common helpers / utils across al OpenAI endpoints
 """
 
 import hashlib
+import inspect
 import json
 import ssl
-from typing import TYPE_CHECKING, Any, Dict, List, Literal, Optional, Union
+from typing import TYPE_CHECKING, Any, Dict, List, Literal, Optional, Tuple, Union
 
 import httpx
 import openai
@@ -14,8 +15,6 @@ from openai import AsyncAzureOpenAI, AsyncOpenAI, AzureOpenAI, OpenAI
 if TYPE_CHECKING:
     from aiohttp import ClientSession
 
-import inspect
-
 import litellm
 from litellm.llms.base_llm.chat.transformation import BaseLLMException
 from litellm.llms.custom_httpx.http_handler import (
@@ -25,13 +24,13 @@ from litellm.llms.custom_httpx.http_handler import (
 )
 
 
-def _get_client_init_params(cls: type) -> List[str]:
+def _get_client_init_params(cls: type) -> Tuple[str, ...]:
     """Extract __init__ parameter names (excluding 'self') from a class."""
-    return [p for p in inspect.signature(cls.__init__).parameters if p != "self"]  # type: ignore[misc]
+    return tuple(p for p in inspect.signature(cls.__init__).parameters if p != "self")  # type: ignore[misc]
 
 
-_OPENAI_INIT_PARAMS: List[str] = _get_client_init_params(OpenAI)
-_AZURE_OPENAI_INIT_PARAMS: List[str] = _get_client_init_params(AzureOpenAI)
+_OPENAI_INIT_PARAMS: Tuple[str, ...] = _get_client_init_params(OpenAI)
+_AZURE_OPENAI_INIT_PARAMS: Tuple[str, ...] = _get_client_init_params(AzureOpenAI)
 
 
 class OpenAIError(BaseLLMException):
@@ -170,12 +169,12 @@ class BaseOpenAILLM:
             f"is_async={client_initialization_params.get('is_async')}",
         ]
 
-        LITELLM_CLIENT_SPECIFIC_PARAMS = [
+        LITELLM_CLIENT_SPECIFIC_PARAMS = (
             "timeout",
             "max_retries",
             "organization",
             "api_base",
-        ]
+        )
         openai_client_fields = (
             BaseOpenAILLM.get_openai_client_initialization_param_fields(
                 client_type=client_type
@@ -192,8 +191,8 @@ class BaseOpenAILLM:
     @staticmethod
     def get_openai_client_initialization_param_fields(
         client_type: Literal["openai", "azure"]
-    ) -> List[str]:
-        """Returns a list of fields that are used to initialize the OpenAI client"""
+    ) -> Tuple[str, ...]:
+        """Returns a tuple of fields that are used to initialize the OpenAI client"""
         if client_type == "openai":
             return _OPENAI_INIT_PARAMS
         else:
diff --git a/tests/test_litellm/llms/openai/test_openai_common_utils.py b/tests/test_litellm/llms/openai/test_openai_common_utils.py
index f2740be642..8489040660 100644
--- a/tests/test_litellm/llms/openai/test_openai_common_utils.py
+++ b/tests/test_litellm/llms/openai/test_openai_common_utils.py
@@ -146,12 +146,12 @@ def test_precomputed_init_params_match_inspect_signature():
         _OPENAI_INIT_PARAMS,
     )
 
-    expected_openai = [
+    expected_openai = tuple(
         p for p in inspect.signature(OpenAI.__init__).parameters if p != "self"
-    ]
-    expected_azure = [
+    )
+    expected_azure = tuple(
         p for p in inspect.signature(AzureOpenAI.__init__).parameters if p != "self"
-    ]
+    )
 
     assert _OPENAI_INIT_PARAMS == expected_openai
     assert _AZURE_OPENAI_INIT_PARAMS == expected_azure
@@ -161,6 +161,17 @@ def test_precomputed_init_params_match_inspect_signature():
 def test_get_openai_client_initialization_param_fields(client_type):
     """Verify the method returns the correct pre-computed params for each client type."""
     result = BaseOpenAILLM.get_openai_client_initialization_param_fields(client_type)
-    assert isinstance(result, list)
+    assert isinstance(result, tuple)
     assert len(result) > 0
     assert "self" not in result
+
+
+@pytest.mark.parametrize("client_type", ["openai", "azure"])
+def test_get_openai_client_cache_key(client_type):
+    """Verify get_openai_client_cache_key doesn't raise on tuple + tuple concatenation."""
+    key = BaseOpenAILLM.get_openai_client_cache_key(
+        client_initialization_params={"api_key": "sk-test"},
+        client_type=client_type,
+    )
+    assert isinstance(key, str)
+    assert "api_key=sk-test" in key