test(router): cover model_info promotion in add_deployment

DB-loaded and /model/new deployments reach the router through add_deployment, so pin the promotion there too

The cost-map fixture now puts back the entries it removes. The shipped map prices the backend model, and popping that entry for good left it unpriced for every later test in the same process

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/unit/test_router_nested_model_info_pricing.py

@@ -3,12 +3,14 @@ import pytest
 import litellm
 from litellm import Router
 from litellm.router import _model_info_nested_under_litellm_params
+from litellm.types.router import Deployment, LiteLLM_Params
 
 BACKEND_MODEL = "deepinfra/deepseek-ai/DeepSeek-V4-Flash-0731"
 PUBLIC_MODEL = "deepseek-ai/DeepSeek-V4-Flash-0731"
 INPUT_COST = 7.2e-08
 OUTPUT_COST = 1.44e-07
 CACHE_READ_COST = 1.44e-08
+DEPLOYMENT_ID = "db-deployment-id"
 
 
 def _pricing_model_info():
@@ -46,17 +48,23 @@ def _deployment_level_config():
 
 @pytest.fixture(autouse=True)
 def clean_cost_map():
-    """Keep registrations from bleeding across tests."""
+    """Keep registrations from bleeding across tests, and put back the entries the cost map already had."""
     from litellm.utils import _invalidate_model_cost_lowercase_map
 
+    cost_map = litellm.model_cost
+    keys = (BACKEND_MODEL, PUBLIC_MODEL, DEPLOYMENT_ID)
+    original = {key: cost_map[key] for key in keys if key in cost_map}
+
     def _clear():
-        litellm.model_cost.pop(BACKEND_MODEL, None)
-        litellm.model_cost.pop(PUBLIC_MODEL, None)
+        for key in keys:
+            cost_map.pop(key, None)
         _invalidate_model_cost_lowercase_map()
 
     _clear()
     yield
     _clear()
+    cost_map.update(original)
+    _invalidate_model_cost_lowercase_map()
 
 
 def _deployment_pricing(router):
@@ -64,6 +72,16 @@ def _deployment_pricing(router):
     return deployment.get("model_info", {})
 
 
+def _nested_deployment(model_info):
+    """A deployment built the way the proxy loads one from the DB, nested block included."""
+    config = _nested_config()
+    return Deployment(
+        model_name=config["model_name"],
+        litellm_params=LiteLLM_Params.model_validate(config["litellm_params"]),
+        model_info=model_info,
+    )
+
+
 def test_promotes_nothing_when_no_nested_block():
     """No nested block, and a non-dict nested value, both promote nothing."""
     assert _model_info_nested_under_litellm_params({"model": BACKEND_MODEL}, {}) == {}
@@ -175,3 +193,45 @@ async def test_nested_model_info_produces_non_zero_response_cost():
     response_cost = response._hidden_params.get("response_cost")
     assert response_cost is not None
     assert response_cost > 0
+
+
+@pytest.mark.asyncio
+async def test_add_deployment_applies_nested_model_info_pricing():
+    """
+    DB-loaded and /model/new deployments reach the router through add_deployment,
+    not _create_deployment, so the nested block has to be applied there as well.
+    """
+    router = Router(model_list=[])
+    assert router.add_deployment(_nested_deployment({"id": DEPLOYMENT_ID})) is not None
+
+    model_info = _deployment_pricing(router)
+    assert model_info.get("input_cost_per_token") == INPUT_COST
+    assert model_info.get("output_cost_per_token") == OUTPUT_COST
+    assert model_info.get("cache_read_input_token_cost") == CACHE_READ_COST
+
+    # Exact, not just > 0: the shipped cost map also prices this backend model.
+    response = await router.acompletion(
+        model=PUBLIC_MODEL,
+        messages=[{"role": "user", "content": "hi"}],
+        mock_response="hello",
+    )
+    usage = response.usage
+    assert response._hidden_params.get("response_cost") == pytest.approx(
+        usage.prompt_tokens * INPUT_COST + usage.completion_tokens * OUTPUT_COST
+    )
+
+
+def test_add_deployment_keeps_deployment_level_values_and_id():
+    """Only unset fields are applied, and the nested `id` never re-keys the deployment."""
+    deployment = _nested_deployment({"id": DEPLOYMENT_ID, "input_cost_per_token": INPUT_COST})
+    deployment.litellm_params.model_info.update(id="nested-id-should-be-ignored", input_cost_per_token=999.0)
+
+    router = Router(model_list=[])
+    router.add_deployment(deployment)
+
+    model_info = _deployment_pricing(router)
+    assert model_info.get("input_cost_per_token") == INPUT_COST
+    assert model_info.get("output_cost_per_token") == OUTPUT_COST
+    assert model_info.get("id") == DEPLOYMENT_ID
+    assert router.has_model_id(DEPLOYMENT_ID)
+    assert not router.has_model_id("nested-id-should-be-ignored")