fix(model hub): serve custom tags and metadata on model_group_alias rows

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

litellm/proxy/proxy_server.py

@@ -17064,7 +17064,11 @@ def get_model_group_info(
                 ModelGroupInfoProxy.model_validate(
                     {
                         **_model_group_info.model_dump(),
-                        **model_group_custom_fields(llm_router.get_model_list_of_routed_group(model)),
+                        **model_group_custom_fields(
+                            llm_router.get_model_list_of_routed_group(
+                                resolve_model_group_alias(llm_router.model_group_alias, model) or model
+                            )
+                        ),
                     }
                 )
             )

tests/integration/management/test_model_hub_custom_metadata.py

@@ -205,6 +205,7 @@ def _yaml_config(
     model_info: Mapping[str, object] = MappingProxyType(
         {"custom_tags": ["deprecated", "ptu"], "custom_metadata": LIFECYCLE_METADATA}
     ),
+    model_group_alias: Mapping[str, str] = MappingProxyType({}),
 ) -> Path:
     config: Final = yaml.safe_load(Path("tests/integration/proxy_config.yaml").read_text())
     deployment: Final = {
@@ -213,7 +214,12 @@ def _yaml_config(
         "model_info": dict(model_info),
     }
     path: Final = directory / "custom_fields.yaml"
-    path.write_text(yaml.safe_dump({**config, "model_list": [*config["model_list"], deployment]}))
+    router_settings: Final = {**config.get("router_settings", {}), "model_group_alias": dict(model_group_alias)}
+    path.write_text(
+        yaml.safe_dump(
+            {**config, "model_list": [*config["model_list"], deployment], "router_settings": router_settings}
+        )
+    )
     return path
 
 
@@ -256,3 +262,15 @@ def test_yaml_custom_metadata_that_json_cannot_carry_is_dropped_without_breaking
         assert every_group.status_code == 200, every_group.text
         group: Final = _model_group(owned.gateway, model_name)
         assert _custom_fields(group) == (["ptu"], {"retirement_date": "2027-03-01"}), group
+
+
+@pytest.mark.timeout(2 * graceful_stop_seconds() + 120)
+def test_an_alias_group_serves_the_custom_tags_and_metadata_of_the_group_it_points_to(
+    gateway: Gateway, tmp_path: Path
+) -> None:
+    model_name: Final = f"integration-yaml-{uuid.uuid4().hex}"
+    alias: Final = f"{model_name}-alias"
+    config: Final = _yaml_config(tmp_path, gateway.upstream_url, model_name, model_group_alias={alias: model_name})
+    with owned_proxy_process(gateway, tmp_path, {}, config=config) as owned:
+        group: Final = _model_group(owned.gateway, alias)
+        assert _custom_fields(group) == (["deprecated", "ptu"], LIFECYCLE_METADATA), group

tests/unit/proxy/public_endpoints/public_v1/test_model_hub.py

@@ -24,6 +24,7 @@ class _FakeRouter:
     """Stands in for the running Router: `_get_model_group_info` only ever asks it these."""
 
     infos: Mapping[str, ModelGroupInfo]
+    model_group_alias: Mapping[str, str] = MappingProxyType({})
 
     def get_model_group_info(self, model_group: str) -> ModelGroupInfo | None:
         return self.infos.get(model_group)

tests/unit/proxy/test_proxy_utils.py

@@ -1679,6 +1679,33 @@ def test_get_model_group_info_merges_custom_tags_and_metadata_across_deployments
     assert (group.custom_tags, group.custom_metadata) == (expected_tags, expected_metadata)
 
 
+
+@pytest.mark.parametrize(
+    "alias_target",
+    [pytest.param("gpt-4", id="string"), pytest.param({"model": "gpt-4", "hidden": False}, id="item")],
+)
+def test_get_model_group_info_serves_the_target_groups_custom_fields_on_an_alias_row(
+    alias_target: str | dict[str, object],
+) -> None:
+    from litellm.proxy.proxy_server import get_model_group_info
+
+    router: Final = Router(
+        model_list=[
+            {
+                "model_name": "gpt-4",
+                "litellm_params": {"model": "gpt-4", "api_key": "fake"},
+                "model_info": {"custom_tags": ["deprecated"], "custom_metadata": {"retirement_date": "2027-03-01"}},
+            }
+        ],
+        model_group_alias={"gpt-alias": alias_target},
+    )
+
+    groups: Final = get_model_group_info(llm_router=router, all_models_str=["gpt-4", "gpt-alias"], model_group=None)
+
+    assert {group.model_group: (group.custom_tags, group.custom_metadata) for group in groups} == {
+        model_group: (("deprecated",), {"retirement_date": "2027-03-01"}) for model_group in ("gpt-4", "gpt-alias")
+    }
+
 @pytest.fixture
 def mock_team_data():
     return [