fix(proxy): stop 500 on /tag/update when the request carries budget_id

handle_budget_for_entity collects the update fields from
LiteLLM_BudgetTable.model_fields, which includes budget_id, then calls
BudgetNewRequest(budget_id=existing_budget_id, **fields) - so any update
carrying budget_id, even the entity's own unchanged id, passed it twice
and the endpoint 500'd before writing anything.

budget_id is the row identity, already handled separately via
data_budget_id; exclude it from the collected fields.

Fixes #46999

litellm/proxy/management_helpers/utils.py

@@ -215,8 +215,10 @@ async def handle_budget_for_entity(
         update_budget,
     )
 
-    # Get all budget field names
-    budget_params: Final = LiteLLM_BudgetTable.model_fields.keys()
+    # Get all budget field names, except budget_id: that is the row identity,
+    # handled separately via data_budget_id. Collecting it here passes it twice
+    # to BudgetNewRequest on the update path and 500s the request.
+    budget_params: Final = LiteLLM_BudgetTable.model_fields.keys() - {"budget_id"}
 
     # Extract budget fields from data
     _json_data: Final = _BUDGET_DATA_MAPPING.validate_python(

tests/unit/proxy/management_helpers/test_management_helpers_utils.py

@@ -309,6 +309,41 @@ async def test_handle_budget_for_entity_updates_only_cleared_or_supplied_fields(
     }
 
 
+@pytest.mark.asyncio
+async def test_handle_budget_for_entity_update_carrying_own_budget_id() -> None:
+    """Regression for #46999: a /tag/update that carries the tag's own budget_id
+    500'd with "multiple values for keyword argument 'budget_id'" because the id
+    was collected into the update fields and also passed explicitly. The id is
+    the row identity, not an updatable field, and the update must go through."""
+    from litellm.proxy.management_helpers.utils import handle_budget_for_entity
+    from litellm.types.tag_management import TagUpdateRequest
+
+    tag: Final = TagUpdateRequest.model_validate({"name": "budget-tag", "budget_id": "budget-1", "max_budget": 10})
+    budget_update: Final = AsyncMock()
+    prisma_client: Final = cast(
+        PrismaClient,
+        SimpleNamespace(db=SimpleNamespace(litellm_budgettable=SimpleNamespace(update=budget_update))),
+    )
+
+    with (
+        patch("litellm.proxy.proxy_server.prisma_client", prisma_client),
+        patch("litellm.proxy.proxy_server.litellm_proxy_admin_name", "admin"),
+    ):
+        returned: Final = await handle_budget_for_entity(
+            data=tag,
+            existing_budget_id="budget-1",
+            user_api_key_dict=UserAPIKeyAuth(user_id="admin"),
+            prisma_client=prisma_client,
+            litellm_proxy_admin_name="admin",
+            cleared_budget_fields=frozenset(),
+        )
+
+    assert returned == "budget-1"
+    budget_update.assert_awaited_once()
+    update_data: Final = cast(Mapping[str, object], budget_update.await_args.kwargs["data"])
+    assert update_data.get("max_budget") == 10
+
+
 @pytest.mark.asyncio
 async def test_add_new_member_no_budget_when_default_budget_row_is_missing():
     from litellm.proxy._types import LitellmUserRoles