From 9f7fc215f639bfe5e07bef667e4ee89bd438c1f4 Mon Sep 17 00:00:00 2001
From: mateo-berri <277851410+mateo-berri@users.noreply.github.com>
Date: Thu, 29 Oct 2026 04:52:04 -0700
Subject: [PATCH] fix(router): list cache prices at the input rate billing
 charges when a deployment has none

---
 .../litellm_core_utils/llm_cost_calc/utils.py | 20 ++++-
 tests/unit/test_router/test_router.py         | 73 +++++++++++++++++++
 2 files changed, 90 insertions(+), 3 deletions(-)

diff --git a/litellm/litellm_core_utils/llm_cost_calc/utils.py b/litellm/litellm_core_utils/llm_cost_calc/utils.py
index edfabf43ad0..5f5d5b4b920 100644
--- a/litellm/litellm_core_utils/llm_cost_calc/utils.py
+++ b/litellm/litellm_core_utils/llm_cost_calc/utils.py
@@ -959,14 +959,28 @@ _get_cost_per_unit = get_cost_per_unit
 _HALF_PRICED_BATCH_KEYS: Final = frozenset(
     {f"input_cost_per_token{_BATCH_KEY_SUFFIX}", f"output_cost_per_token{_BATCH_KEY_SUFFIX}"}
 )
+_TIER_KEY_SUFFIXES: Final = ("", *SERVICE_TIER_COST_KEY_SUFFIXES)
+_CACHE_KEYS_BILLED_AT_INPUT_RATE: Final = MappingProxyType(
+    {
+        **{f"cache_read_input_token_cost{suffix}": f"input_cost_per_token{suffix}" for suffix in _TIER_KEY_SUFFIXES},
+        **{
+            f"cache_creation_input_token_cost{suffix}": f"input_cost_per_token{suffix}" for suffix in _TIER_KEY_SUFFIXES
+        },
+    }
+)
 
 
 def billed_rate(model_info: Mapping[str, object], cost_key: str) -> float | None:
     rate: Final = get_cost_per_unit(model_info, cost_key, default_value=None)
-    if rate is not None or cost_key not in _HALF_PRICED_BATCH_KEYS:
+    if rate is not None:
         return rate
-    standard_rate: Final = get_cost_per_unit(model_info, cost_key.removesuffix(_BATCH_KEY_SUFFIX), default_value=None)
-    return None if standard_rate is None else standard_rate / 2
+    if cost_key in _HALF_PRICED_BATCH_KEYS:
+        standard_rate: Final = get_cost_per_unit(
+            model_info, cost_key.removesuffix(_BATCH_KEY_SUFFIX), default_value=None
+        )
+        return None if standard_rate is None else standard_rate / 2
+    input_key: Final = _CACHE_KEYS_BILLED_AT_INPUT_RATE.get(cost_key)
+    return None if input_key is None else get_cost_per_unit(model_info, input_key, default_value=None)
 
 
 def deployment_pricing(model_info: ModelInfo | None) -> ModelInfo | None:
diff --git a/tests/unit/test_router/test_router.py b/tests/unit/test_router/test_router.py
index 4acacb6bac2..c1612540224 100644
--- a/tests/unit/test_router/test_router.py
+++ b/tests/unit/test_router/test_router.py
@@ -2802,6 +2802,79 @@ def test_model_group_info_lists_tier_and_batch_prices_at_the_most_any_deployment
     assert tuple(listed[key] * tokens for key in listed_keys) == pytest.approx(highest_bills)
 
 
+def test_model_group_info_lists_cache_prices_at_the_most_any_deployment_bills(monkeypatch: pytest.MonkeyPatch):
+    from litellm.utils import _invalidate_model_cost_lowercase_map
+
+    backends: Final = ("made-up-cached-backend", "made-up-uncached-backend")
+    monkeypatch.setattr(
+        litellm,
+        "model_cost",
+        {
+            **litellm.model_cost,
+            backends[0]: {
+                "litellm_provider": "openai",
+                "mode": "chat",
+                "input_cost_per_token": 1e-06,
+                "output_cost_per_token": 4e-06,
+                "input_cost_per_token_priority": 2e-06,
+                "cache_read_input_token_cost": 1e-07,
+                "cache_read_input_token_cost_priority": 2e-07,
+                "cache_creation_input_token_cost": 1.25e-06,
+            },
+            backends[1]: {
+                "litellm_provider": "openai",
+                "mode": "chat",
+                "input_cost_per_token": 3e-06,
+                "output_cost_per_token": 1.2e-05,
+                "input_cost_per_token_priority": 6e-06,
+            },
+        },
+    )
+    _invalidate_model_cost_lowercase_map()
+    router: Final = litellm.Router(
+        model_list=[
+            {
+                "model_name": "mixed-cache-group",
+                "litellm_params": {"model": f"openai/{backend}", "api_key": "fake"},
+                "model_info": {"id": backend},
+            }
+            for backend in backends
+        ]
+    )
+    tokens: Final = 1_000_000
+
+    def highest_prompt_bill(cache_read_tokens: int, cache_creation_tokens: int, service_tier: str | None) -> float:
+        return max(
+            litellm.cost_per_token(
+                model=backend,
+                custom_llm_provider="openai",
+                prompt_tokens=tokens,
+                completion_tokens=0,
+                cache_read_input_tokens=cache_read_tokens,
+                cache_creation_input_tokens=cache_creation_tokens,
+                service_tier=service_tier,
+            )[0]
+            for backend in backends
+        )
+
+    highest_bills: Final = (
+        highest_prompt_bill(tokens, 0, None),
+        highest_prompt_bill(tokens, 0, "priority"),
+        highest_prompt_bill(0, tokens, None),
+    )
+
+    info: Final = router.get_model_group_info(model_group="mixed-cache-group")
+
+    assert info is not None
+    listed: Final = info.model_dump()
+    listed_keys: Final = (
+        "cache_read_input_token_cost",
+        "cache_read_input_token_cost_priority",
+        "cache_creation_input_token_cost",
+    )
+    assert tuple(listed[key] * tokens for key in listed_keys) == pytest.approx(highest_bills)
+
+
 @pytest.mark.parametrize(("team_id", "listed_cache_read_cost"), [(None, 1e-07), ("team-b", 1e-07), ("team-a", 9e-06)])
 def test_model_group_info_lists_a_team_deployment_price_only_to_that_team(
     monkeypatch: pytest.MonkeyPatch, team_id: str | None, listed_cache_read_cost: float