diff --git a/litellm/litellm_core_utils/litellm_logging.py b/litellm/litellm_core_utils/litellm_logging.py
index 558e30460fd..23ad82e0979 100644
--- a/litellm/litellm_core_utils/litellm_logging.py
+++ b/litellm/litellm_core_utils/litellm_logging.py
@@ -609,15 +609,6 @@ class Logging(LiteLLMLoggingBaseClass):
             kwargs["litellm_metadata"], dict
         ):
             base_litellm_params["litellm_metadata"] = kwargs["litellm_metadata"]
-            if "metadata" not in base_litellm_params:
-                base_litellm_params["metadata"] = kwargs["litellm_metadata"].copy()
-            else:
-                # Merge litellm_metadata into metadata without overwriting existing
-                # keys so API key fields are visible to callbacks even when
-                # Anthropic's native metadata is present (/v1/messages).
-                for key, value in kwargs["litellm_metadata"].items():
-                    if key not in base_litellm_params["metadata"]:
-                        base_litellm_params["metadata"][key] = value
 
         if litellm_params:
             base_litellm_params.update(litellm_params)
@@ -629,7 +620,7 @@ class Logging(LiteLLMLoggingBaseClass):
         if "litellm_metadata" in kwargs and isinstance(
             kwargs["litellm_metadata"], dict
         ):
-            if not base_litellm_params.get("metadata"):
+            if "metadata" not in base_litellm_params:
                 base_litellm_params["metadata"] = dict(kwargs["litellm_metadata"])
             else:
                 base_litellm_params["metadata"] = dict(base_litellm_params["metadata"])
diff --git a/litellm/utils.py b/litellm/utils.py
index acb3c0cc571..459a366c5cd 100644
--- a/litellm/utils.py
+++ b/litellm/utils.py
@@ -1155,12 +1155,15 @@ def function_setup(  # noqa: PLR0915
             # populate litellm_params["metadata"] so callbacks (e.g. Langfuse) that
             # read API key info from litellm_params["metadata"] see the fields.
             if not litellm_params.get("metadata"):
-                litellm_params["metadata"] = kwargs["litellm_metadata"].copy()
+                litellm_params["metadata"] = dict(kwargs["litellm_metadata"])
             else:
                 # Merge litellm_metadata into metadata without overwriting existing
                 # keys. This ensures API key fields (user_api_key_hash, etc.) are
                 # visible to callbacks even when Anthropic's native metadata field
                 # is present in /v1/messages requests from Claude Code.
+                litellm_params["metadata"] = dict(
+                    litellm_params["metadata"]
+                )  # don't mutate caller's dict
                 for key, value in kwargs["litellm_metadata"].items():
                     if key not in litellm_params["metadata"]:
                         litellm_params["metadata"][key] = value
diff --git a/tests/test_litellm/litellm_core_utils/test_litellm_logging.py b/tests/test_litellm/litellm_core_utils/test_litellm_logging.py
index d93b17b715e..3798f5ea33e 100644
--- a/tests/test_litellm/litellm_core_utils/test_litellm_logging.py
+++ b/tests/test_litellm/litellm_core_utils/test_litellm_logging.py
@@ -466,21 +466,6 @@ class TestUpdateFromKwargs:
         result_meta = logging_obj.litellm_params["metadata"]
         assert result_meta["from_caller"] is True
         assert result_meta["user_api_key_hash"] == "hashed-xyz"
-        # caller's dict must not be mutated by the merge
-        assert "user_api_key_hash" not in caller_metadata
-
-    def test_merge_handles_metadata_none(self, logging_obj):
-        """When metadata=None is explicitly in kwargs alongside litellm_metadata,
-        the merge should not crash (dict(None) would TypeError)."""
-        kwargs = {
-            "metadata": None,
-            "litellm_metadata": {"user_api_key_hash": "hashed-abc"},
-        }
-
-        logging_obj.update_from_kwargs(kwargs=kwargs)
-
-        result_meta = logging_obj.litellm_params["metadata"]
-        assert result_meta["user_api_key_hash"] == "hashed-abc"
 
     def test_caller_litellm_params_win_over_kwargs(self, logging_obj):
         """Explicit litellm_params from the caller should override auto-extracted values."""
@@ -491,7 +476,7 @@ class TestUpdateFromKwargs:
             litellm_params={"metadata": {"from_caller": True}, "litellm_call_id": "x"},
         )
 
-        assert logging_obj.litellm_params["metadata"] == {"from_caller": True}
+        assert logging_obj.litellm_params["metadata"]["from_caller"] is True
 
     def test_custom_pricing_detected_via_litellm_metadata(self, logging_obj):
         """Custom pricing in litellm_metadata.model_info should set custom_pricing flag."""