(fix) tag merging / aggregation logic (#6932)

* use 1 helper to merge tags + ensure unique ness

* test_add_litellm_data_to_request_duplicate_tags

* fix _merge_tags

* fix proxy utils test

litellm/proxy/litellm_pre_call_utils.py

@@ -288,12 +288,12 @@ class LiteLLMProxyRequestSetup:
 
         ## KEY-LEVEL SPEND LOGS / TAGS
         if "tags" in key_metadata and key_metadata["tags"] is not None:
-            if "tags" in data[_metadata_variable_name] and isinstance(
-                data[_metadata_variable_name]["tags"], list
-            ):
-                data[_metadata_variable_name]["tags"].extend(key_metadata["tags"])
-            else:
-                data[_metadata_variable_name]["tags"] = key_metadata["tags"]
+            data[_metadata_variable_name]["tags"] = (
+                LiteLLMProxyRequestSetup._merge_tags(
+                    request_tags=data[_metadata_variable_name].get("tags"),
+                    tags_to_add=key_metadata["tags"],
+                )
+            )
         if "spend_logs_metadata" in key_metadata and isinstance(
             key_metadata["spend_logs_metadata"], dict
         ):
@@ -319,6 +319,30 @@ class LiteLLMProxyRequestSetup:
             data["disable_fallbacks"] = key_metadata["disable_fallbacks"]
         return data
 
+    @staticmethod
+    def _merge_tags(request_tags: Optional[list], tags_to_add: Optional[list]) -> list:
+        """
+        Helper function to merge two lists of tags, ensuring no duplicates.
+
+        Args:
+            request_tags (Optional[list]): List of tags from the original request
+            tags_to_add (Optional[list]): List of tags to add
+
+        Returns:
+            list: Combined list of unique tags
+        """
+        final_tags = []
+
+        if request_tags and isinstance(request_tags, list):
+            final_tags.extend(request_tags)
+
+        if tags_to_add and isinstance(tags_to_add, list):
+            for tag in tags_to_add:
+                if tag not in final_tags:
+                    final_tags.append(tag)
+
+        return final_tags
+
 
 async def add_litellm_data_to_request(  # noqa: PLR0915
     data: dict,
@@ -442,12 +466,10 @@ async def add_litellm_data_to_request(  # noqa: PLR0915
     ## TEAM-LEVEL SPEND LOGS/TAGS
     team_metadata = user_api_key_dict.team_metadata or {}
     if "tags" in team_metadata and team_metadata["tags"] is not None:
-        if "tags" in data[_metadata_variable_name] and isinstance(
-            data[_metadata_variable_name]["tags"], list
-        ):
-            data[_metadata_variable_name]["tags"].extend(team_metadata["tags"])
-        else:
-            data[_metadata_variable_name]["tags"] = team_metadata["tags"]
+        data[_metadata_variable_name]["tags"] = LiteLLMProxyRequestSetup._merge_tags(
+            request_tags=data[_metadata_variable_name].get("tags"),
+            tags_to_add=team_metadata["tags"],
+        )
     if "spend_logs_metadata" in team_metadata and isinstance(
         team_metadata["spend_logs_metadata"], dict
     ):

tests/proxy_unit_tests/test_proxy_utils.py

@@ -574,3 +574,108 @@ def test_get_docs_url(env_vars, expected_url):
 
     result = _get_docs_url()
     assert result == expected_url
+
+
+@pytest.mark.parametrize(
+    "request_tags, tags_to_add, expected_tags",
+    [
+        (None, None, []),  # both None
+        (["tag1", "tag2"], None, ["tag1", "tag2"]),  # tags_to_add is None
+        (None, ["tag3", "tag4"], ["tag3", "tag4"]),  # request_tags is None
+        (
+            ["tag1", "tag2"],
+            ["tag3", "tag4"],
+            ["tag1", "tag2", "tag3", "tag4"],
+        ),  # both have unique tags
+        (
+            ["tag1", "tag2"],
+            ["tag2", "tag3"],
+            ["tag1", "tag2", "tag3"],
+        ),  # overlapping tags
+        ([], [], []),  # both empty lists
+        ("not_a_list", ["tag1"], ["tag1"]),  # request_tags invalid type
+        (["tag1"], "not_a_list", ["tag1"]),  # tags_to_add invalid type
+        (
+            ["tag1"],
+            ["tag1", "tag2"],
+            ["tag1", "tag2"],
+        ),  # duplicate tags in inputs
+    ],
+)
+def test_merge_tags(request_tags, tags_to_add, expected_tags):
+    from litellm.proxy.litellm_pre_call_utils import LiteLLMProxyRequestSetup
+
+    result = LiteLLMProxyRequestSetup._merge_tags(
+        request_tags=request_tags, tags_to_add=tags_to_add
+    )
+
+    assert isinstance(result, list)
+    assert sorted(result) == sorted(expected_tags)
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize(
+    "key_tags, request_tags, expected_tags",
+    [
+        # exact duplicates
+        (["tag1", "tag2", "tag3"], ["tag1", "tag2", "tag3"], ["tag1", "tag2", "tag3"]),
+        # partial duplicates
+        (
+            ["tag1", "tag2", "tag3"],
+            ["tag2", "tag3", "tag4"],
+            ["tag1", "tag2", "tag3", "tag4"],
+        ),
+        # duplicates within key tags
+        (["tag1", "tag2"], ["tag3", "tag4"], ["tag1", "tag2", "tag3", "tag4"]),
+        # duplicates within request tags
+        (["tag1", "tag2"], ["tag2", "tag3", "tag4"], ["tag1", "tag2", "tag3", "tag4"]),
+        # case sensitive duplicates
+        (["Tag1", "TAG2"], ["tag1", "tag2"], ["Tag1", "TAG2", "tag1", "tag2"]),
+    ],
+)
+async def test_add_litellm_data_to_request_duplicate_tags(
+    key_tags, request_tags, expected_tags
+):
+    """
+    Test to verify duplicate tags between request and key metadata are handled correctly
+
+
+    Aggregation logic when checking spend can be impacted if duplicate tags are not handled correctly.
+
+    User feedback:
+    "If I register my key with tag1 and
+    also pass the same tag1 when using the key
+    then I see tag1 twice in the
+    LiteLLM_SpendLogs table request_tags column. This can mess up aggregation logic"
+    """
+    mock_request = Mock(spec=Request)
+    mock_request.url.path = "/chat/completions"
+    mock_request.query_params = {}
+    mock_request.headers = {}
+
+    # Setup key with tags in metadata
+    user_api_key_dict = UserAPIKeyAuth(
+        api_key="test_api_key",
+        user_id="test_user_id",
+        org_id="test_org_id",
+        metadata={"tags": key_tags},
+    )
+
+    # Setup request data with tags
+    data = {"metadata": {"tags": request_tags}}
+
+    # Process request
+    proxy_config = Mock()
+    result = await add_litellm_data_to_request(
+        data=data,
+        request=mock_request,
+        user_api_key_dict=user_api_key_dict,
+        proxy_config=proxy_config,
+    )
+
+    # Verify results
+    assert "metadata" in result
+    assert "tags" in result["metadata"]
+    assert sorted(result["metadata"]["tags"]) == sorted(
+        expected_tags
+    ), f"Expected {expected_tags}, got {result['metadata']['tags']}"