fix: guard check_and_fix_namespace against None key

When user_id is None, the cache key can be None, causing
AttributeError: 'NoneType' object has no attribute 'startswith'
in check_and_fix_namespace.

Add an early return for None key to prevent the error and the
ERROR-level log noise it produces on every unauthenticated request.

Fixes #30424

litellm/caching/redis_cache.py

@@ -369,6 +369,8 @@ class RedisCache(BaseCache):
         """
         Make sure each key starts with the given namespace
         """
+        if key is None:
+            return key
         if self.namespace is not None and not key.startswith(self.namespace):
             key = self.namespace + ":" + key
 

tests/test_litellm/caching/test_check_and_fix_namespace_none_guard.py

@@ -0,0 +1,49 @@
+"""
+Test that check_and_fix_namespace handles None key gracefully.
+
+Regression test for https://github.com/BerriAI/litellm/issues/30424
+"""
+from unittest.mock import MagicMock
+
+from litellm.caching.redis_cache import RedisCache
+
+
+def test_check_and_fix_namespace_with_none_key():
+    """When key is None, check_and_fix_namespace should return None without raising."""
+    cache = MagicMock(spec=RedisCache)
+    cache.namespace = "litellm"
+    # Call the real method
+    result = RedisCache.check_and_fix_namespace(cache, key=None)
+    assert result is None
+
+
+def test_check_and_fix_namespace_with_none_key_no_namespace():
+    """When key is None and namespace is None, should return None without raising."""
+    cache = MagicMock(spec=RedisCache)
+    cache.namespace = None
+    result = RedisCache.check_and_fix_namespace(cache, key=None)
+    assert result is None
+
+
+def test_check_and_fix_namespace_with_valid_key():
+    """Normal behavior: prefix key with namespace if not already prefixed."""
+    cache = MagicMock(spec=RedisCache)
+    cache.namespace = "litellm"
+    result = RedisCache.check_and_fix_namespace(cache, key="my_key")
+    assert result == "litellm:my_key"
+
+
+def test_check_and_fix_namespace_with_already_prefixed_key():
+    """If key already starts with namespace, don't double-prefix."""
+    cache = MagicMock(spec=RedisCache)
+    cache.namespace = "litellm"
+    result = RedisCache.check_and_fix_namespace(cache, key="litellm:my_key")
+    assert result == "litellm:my_key"
+
+
+def test_check_and_fix_namespace_no_namespace():
+    """When namespace is None, return key as-is."""
+    cache = MagicMock(spec=RedisCache)
+    cache.namespace = None
+    result = RedisCache.check_and_fix_namespace(cache, key="my_key")
+    assert result == "my_key"