diff --git a/litellm/cost_calculator.py b/litellm/cost_calculator.py
index 38c0177479a..7e3b2154698 100644
--- a/litellm/cost_calculator.py
+++ b/litellm/cost_calculator.py
@@ -2,8 +2,9 @@
 ## File for 'response_cost' calculation in Logging
 import logging
 import time
-from collections.abc import Sequence
+from collections.abc import Mapping, Sequence
 from functools import lru_cache
+from types import MappingProxyType
 from typing import TYPE_CHECKING, Any, Final, Literal, cast
 
 from httpx import Response
@@ -236,67 +237,127 @@ def _cost_per_token_custom_pricing_helper(
     return None
 
 
+def _litellm_params_as_mapping(litellm_params: object | None) -> Mapping[str, object] | None:
+    if litellm_params is None:
+        return None
+    if isinstance(litellm_params, Mapping):
+        return litellm_params
+    dump: Final = getattr(litellm_params, "model_dump", None)
+    if not callable(dump):
+        return None
+    dumped: Final = dump()
+    if not isinstance(dumped, Mapping):
+        return None
+    return dumped
+
+
+def _model_info_from_params(params: Mapping[str, object], metadata_key: str) -> Mapping[str, object] | None:
+    metadata: Final = params.get(metadata_key)
+    if not isinstance(metadata, Mapping):
+        return None
+    return _litellm_params_as_mapping(metadata.get("model_info"))
+
+
+def _custom_rates_from_mapping(source: Mapping[str, object] | None) -> Mapping[str, float] | None:
+    if source is None:
+        return None
+    input_cost: Final = source.get("input_cost_per_token")
+    output_cost: Final = source.get("output_cost_per_token")
+    if input_cost is None and output_cost is None:
+        return None
+    cache_read: Final = source.get("cache_read_input_token_cost")
+    cache_creation: Final = source.get("cache_creation_input_token_cost")
+    pairs: Final = (
+        ("input_cost_per_token", input_cost),
+        ("output_cost_per_token", output_cost),
+        ("cache_read_input_token_cost", cache_read),
+        ("cache_creation_input_token_cost", cache_creation),
+    )
+    return MappingProxyType({key: float(value) for key, value in pairs if value is not None})
+
+
 def extract_custom_cost_per_token(
     litellm_params: object | None,
-) -> CostPerToken | None:
-    """Return deployment token rates from litellm_params when both input and output are set.
+) -> Mapping[str, float] | None:
+    """Return deployment token rates from litellm_params when input and/or output is set.
 
     Rates may sit on litellm_params itself (UI / model_list) or under
     metadata.model_info / litellm_metadata.model_info (/v1/messages, /v1/responses).
+    One-sided rates are returned as-is; callers that need a complete CostPerToken
+    fill the missing side from the published price map.
     Optional cache rates are copied when present so the custom-pricing helper can
     apply them instead of falling back to the input rate.
     """
-    if litellm_params is None:
+    params: Final = _litellm_params_as_mapping(litellm_params)
+    if params is None:
         return None
-    if not isinstance(litellm_params, dict):
-        dump = getattr(litellm_params, "model_dump", None)
-        if not callable(dump):
-            return None
-        dumped = dump()
-        if not isinstance(dumped, dict):
-            return None
-        litellm_params = dumped
+    return (
+        _custom_rates_from_mapping(params)
+        or _custom_rates_from_mapping(_model_info_from_params(params, "metadata"))
+        or _custom_rates_from_mapping(_model_info_from_params(params, "litellm_metadata"))
+    )
 
-    def _from_mapping(source: object) -> CostPerToken | None:
-        if not isinstance(source, dict):
-            return None
-        input_cost = source.get("input_cost_per_token")
-        output_cost = source.get("output_cost_per_token")
-        if input_cost is None or output_cost is None:
-            return None
-        result: CostPerToken = {
-            "input_cost_per_token": float(input_cost),
-            "output_cost_per_token": float(output_cost),
-        }
-        cache_read = source.get("cache_read_input_token_cost")
-        if cache_read is not None:
-            result["cache_read_input_token_cost"] = float(cache_read)
-        cache_creation = source.get("cache_creation_input_token_cost")
-        if cache_creation is not None:
-            result["cache_creation_input_token_cost"] = float(cache_creation)
-        return result
 
-    from_top = _from_mapping(litellm_params)
-    if from_top is not None:
-        return from_top
-    for metadata_key in ("metadata", "litellm_metadata"):
-        metadata = litellm_params.get(metadata_key) or {}
-        from_info = _from_mapping(metadata.get("model_info") if isinstance(metadata, dict) else None)
-        if from_info is not None:
-            return from_info
-    return None
+def _published_token_rate(
+    model: str | None,
+    custom_llm_provider: str | None,
+    field: str,
+) -> float:
+    if not model:
+        return 0.0
+    try:
+        info: Final = litellm.get_model_info(model=model, custom_llm_provider=custom_llm_provider)
+    except Exception:
+        return 0.0
+    value: Final = info.get(field)
+    if value is None:
+        return 0.0
+    return float(value)
+
+
+def _complete_custom_cost_per_token(
+    rates: Mapping[str, float] | None,
+    *,
+    model: str | None,
+    custom_llm_provider: str | None,
+) -> CostPerToken | None:
+    if rates is None:
+        return None
+    input_cost: Final = rates.get("input_cost_per_token")
+    output_cost: Final = rates.get("output_cost_per_token")
+    if input_cost is None and output_cost is None:
+        return None
+    resolved_input: Final = (
+        float(input_cost)
+        if input_cost is not None
+        else _published_token_rate(model, custom_llm_provider, "input_cost_per_token")
+    )
+    resolved_output: Final = (
+        float(output_cost)
+        if output_cost is not None
+        else _published_token_rate(model, custom_llm_provider, "output_cost_per_token")
+    )
+    cache_read: Final = rates.get("cache_read_input_token_cost")
+    cache_creation: Final = rates.get("cache_creation_input_token_cost")
+    completed: Final[CostPerToken] = {
+        "input_cost_per_token": resolved_input,
+        "output_cost_per_token": resolved_output,
+        "cache_read_input_token_cost": (float(cache_read) if cache_read is not None else resolved_input),
+        "cache_creation_input_token_cost": (float(cache_creation) if cache_creation is not None else resolved_input),
+    }
+    return completed
 
 
 def _custom_cost_per_token_from_logging_obj(
     litellm_logging_obj: LitellmLoggingObject | None,
-) -> CostPerToken | None:
+) -> Mapping[str, float] | None:
     if litellm_logging_obj is None:
         return None
-    extracted = extract_custom_cost_per_token(getattr(litellm_logging_obj, "litellm_params", None))
-    if extracted is not None:
-        return extracted
-    details = getattr(litellm_logging_obj, "model_call_details", None) or {}
-    nested = details.get("litellm_params") if isinstance(details, dict) else None
+    from_attr: Final = extract_custom_cost_per_token(getattr(litellm_logging_obj, "litellm_params", None))
+    if from_attr is not None:
+        return from_attr
+    details: Final = getattr(litellm_logging_obj, "model_call_details", None)
+    nested: Final = details.get("litellm_params") if isinstance(details, Mapping) else None
     return extract_custom_cost_per_token(nested)
 
 
@@ -1273,9 +1334,6 @@ def completion_cost(
         - For un-mapped Replicate models, the cost is calculated based on the total time used for the request.
     """
     try:
-        if custom_cost_per_token is None:
-            custom_cost_per_token = _custom_cost_per_token_from_logging_obj(litellm_logging_obj)
-
         call_type = _infer_call_type(call_type, completion_response) or "completion"
 
         if (
@@ -1331,6 +1389,16 @@ def completion_cost(
         if model is not None:
             potential_model_names.append(model)
 
+        resolved_custom_cost_per_token: Final = (
+            custom_cost_per_token
+            if custom_cost_per_token is not None
+            else _complete_custom_cost_per_token(
+                _custom_cost_per_token_from_logging_obj(litellm_logging_obj),
+                model=selected_model,
+                custom_llm_provider=custom_llm_provider if isinstance(custom_llm_provider, str) else None,
+            )
+        )
+
         for idx, model in enumerate(potential_model_names):
             try:
                 if verbose_logger.isEnabledFor(logging.DEBUG):
@@ -1680,7 +1748,7 @@ def completion_cost(
                     response_time_ms=total_time,
                     region_name=region_name,
                     custom_cost_per_second=custom_cost_per_second,
-                    custom_cost_per_token=custom_cost_per_token,
+                    custom_cost_per_token=resolved_custom_cost_per_token,
                     prompt_characters=prompt_characters,
                     completion_characters=completion_characters,
                     cache_creation_input_tokens=cache_creation_input_tokens,
diff --git a/litellm/proxy/pass_through_endpoints/pass_through_endpoints.py b/litellm/proxy/pass_through_endpoints/pass_through_endpoints.py
index 3d60f4f5f3a..e5939a81816 100644
--- a/litellm/proxy/pass_through_endpoints/pass_through_endpoints.py
+++ b/litellm/proxy/pass_through_endpoints/pass_through_endpoints.py
@@ -77,7 +77,11 @@ from litellm.proxy.common_utils.http_parsing_utils import (
 from litellm.proxy.common_utils.sse_keepalive import (
     wrap_passthrough_sse_bytes_with_keepalive_pings,
 )
-from litellm.proxy.litellm_pre_call_utils import LiteLLMProxyRequestSetup
+from litellm.proxy.litellm_pre_call_utils import (
+    LiteLLMProxyRequestSetup,
+    _key_or_team_allows_client_pricing_override,
+    _strip_client_pricing_overrides,
+)
 from litellm.proxy.utils import normalize_route_for_root_path
 from litellm.repositories.team_repository import TeamRepository
 from litellm.secret_managers.main import get_secret_str
@@ -549,6 +553,8 @@ class HttpPassThroughEndpointHelpers(BasePassthroughUtils):
         from litellm.types.utils import all_litellm_params
 
         _parsed_body = _parsed_body or {}
+        if not _key_or_team_allows_client_pricing_override(user_api_key_dict):
+            _strip_client_pricing_overrides(_parsed_body)
 
         litellm_params_in_body: Final = {}
         for k in all_litellm_params:
diff --git a/tests/pass_through_unit_tests/test_pass_through_unit_tests.py b/tests/pass_through_unit_tests/test_pass_through_unit_tests.py
index ed04b63000f..2be66827006 100644
--- a/tests/pass_through_unit_tests/test_pass_through_unit_tests.py
+++ b/tests/pass_through_unit_tests/test_pass_through_unit_tests.py
@@ -11,6 +11,7 @@ import httpx
 import pytest
 import litellm
 from typing import AsyncGenerator
+from litellm.cost_calculator import extract_custom_cost_per_token
 from litellm.litellm_core_utils.litellm_logging import Logging as LiteLLMLoggingObj
 from litellm.types.passthrough_endpoints.pass_through_endpoints import EndpointType
 from litellm.proxy.pass_through_endpoints.success_handler import (
@@ -235,6 +236,113 @@ def test_init_kwargs_with_litellm_metadata(mock_request, mock_user_api_key_dict)
     assert metadata["user_api_key"] == "test-key"
 
 
+def _passthrough_logging_obj():
+    return LiteLLMLoggingObj(
+        model="test-model",
+        messages=[],
+        stream=False,
+        call_type="test-call-type",
+        start_time=datetime.now(),
+        litellm_call_id="test-call-id",
+        function_id="test-function-id",
+    )
+
+
+def test_init_kwargs_strips_client_token_rates(mock_request, mock_user_api_key_dict):
+    """Client-supplied 0 rates must not land in litellm_params (budget bypass)."""
+    request = mock_request()
+    parsed_body = {
+        "model": "claude-sonnet-4-5-20250929",
+        "input_cost_per_token": 0.0,
+        "output_cost_per_token": 0.0,
+        "messages": [{"role": "user", "content": "hi"}],
+    }
+    passthrough_payload = PassthroughStandardLoggingPayload(
+        url="https://test.com",
+        request_body={},
+    )
+
+    result = HttpPassThroughEndpointHelpers._init_kwargs_for_pass_through_endpoint(
+        request=request,
+        user_api_key_dict=mock_user_api_key_dict,
+        passthrough_logging_payload=passthrough_payload,
+        _parsed_body=parsed_body,
+        litellm_call_id="test-call-id",
+        logging_obj=_passthrough_logging_obj(),
+    )
+
+    assert "input_cost_per_token" not in result["litellm_params"]
+    assert "output_cost_per_token" not in result["litellm_params"]
+    assert extract_custom_cost_per_token(result["litellm_params"]) is None
+
+
+def test_init_kwargs_strips_client_model_info_pricing(
+    mock_request, mock_user_api_key_dict
+):
+    request = mock_request()
+    parsed_body = {
+        "litellm_metadata": {
+            "tags": ["keep-me"],
+            "model_info": {
+                "input_cost_per_token": 0.0,
+                "output_cost_per_token": 0.0,
+            },
+        }
+    }
+    passthrough_payload = PassthroughStandardLoggingPayload(
+        url="https://test.com",
+        request_body={},
+    )
+
+    result = HttpPassThroughEndpointHelpers._init_kwargs_for_pass_through_endpoint(
+        request=request,
+        user_api_key_dict=mock_user_api_key_dict,
+        passthrough_logging_payload=passthrough_payload,
+        _parsed_body=parsed_body,
+        litellm_call_id="test-call-id",
+        logging_obj=_passthrough_logging_obj(),
+    )
+
+    metadata = result["litellm_params"]["metadata"]
+    assert metadata["tags"] == ["keep-me"]
+    assert "model_info" not in metadata
+
+
+def test_init_kwargs_keeps_client_pricing_when_key_allows_override(mock_request):
+    request = mock_request()
+    user_api_key_dict = UserAPIKeyAuth(
+        api_key="test-key",
+        user_id="test-user",
+        team_id="test-team",
+        end_user_id="test-user",
+        metadata={"allow_client_pricing_override": True},
+    )
+    parsed_body = {
+        "input_cost_per_token": 0.0,
+        "output_cost_per_token": 0.0,
+    }
+    passthrough_payload = PassthroughStandardLoggingPayload(
+        url="https://test.com",
+        request_body={},
+    )
+
+    result = HttpPassThroughEndpointHelpers._init_kwargs_for_pass_through_endpoint(
+        request=request,
+        user_api_key_dict=user_api_key_dict,
+        passthrough_logging_payload=passthrough_payload,
+        _parsed_body=parsed_body,
+        litellm_call_id="test-call-id",
+        logging_obj=_passthrough_logging_obj(),
+    )
+
+    assert result["litellm_params"]["input_cost_per_token"] == 0.0
+    assert result["litellm_params"]["output_cost_per_token"] == 0.0
+    assert extract_custom_cost_per_token(result["litellm_params"]) == {
+        "input_cost_per_token": 0.0,
+        "output_cost_per_token": 0.0,
+    }
+
+
 def test_init_kwargs_with_tags_in_header(mock_request, mock_user_api_key_dict):
     """
     Tags should be added to metadata if they exist in headers
diff --git a/tests/test_litellm/test_cost_calculator.py b/tests/test_litellm/test_cost_calculator.py
index 09974c18c74..a9b88a61403 100644
--- a/tests/test_litellm/test_cost_calculator.py
+++ b/tests/test_litellm/test_cost_calculator.py
@@ -11,6 +11,9 @@ import litellm
 from litellm.cost_calculator import (
     BaseTokenUsageProcessor,
     RealtimeAPITokenUsageProcessor,
+    _complete_custom_cost_per_token,
+    _custom_cost_per_token_from_logging_obj,
+    _published_token_rate,
     completion_cost,
     cost_per_token,
     extract_custom_cost_per_token,
@@ -20,6 +23,7 @@ from litellm.cost_calculator import (
 from litellm.types.llms.openai import OpenAIRealtimeStreamList
 from litellm.types.utils import (
     CacheCreationTokenDetails,
+    CustomPricingLiteLLMParams,
     ModelInfo,
     ModelResponse,
     PromptTokensDetailsWrapper,
@@ -956,7 +960,13 @@ def test_custom_pricing_cost_calc_uses_router_model_id_from_litellm_metadata():
 
 def test_extract_custom_cost_per_token_from_litellm_params_and_model_info():
     assert extract_custom_cost_per_token(None) is None
-    assert extract_custom_cost_per_token({"input_cost_per_token": 1.2e-05}) is None
+    assert extract_custom_cost_per_token({"custom_llm_provider": "anthropic"}) is None
+    assert extract_custom_cost_per_token({"input_cost_per_token": 1.2e-05}) == {
+        "input_cost_per_token": 1.2e-05,
+    }
+    assert extract_custom_cost_per_token({"output_cost_per_token": 3.6e-05}) == {
+        "output_cost_per_token": 3.6e-05,
+    }
     assert extract_custom_cost_per_token(
         {
             "input_cost_per_token": 1.2e-05,
@@ -968,6 +978,20 @@ def test_extract_custom_cost_per_token_from_litellm_params_and_model_info():
         "output_cost_per_token": 3.6e-05,
         "cache_read_input_token_cost": 1.2e-06,
     }
+    assert extract_custom_cost_per_token(
+        {
+            "metadata": {
+                "model_info": {
+                    "id": "deploy-meta",
+                    "input_cost_per_token": 0.0002,
+                    "output_cost_per_token": 0.0008,
+                },
+            },
+        }
+    ) == {
+        "input_cost_per_token": 0.0002,
+        "output_cost_per_token": 0.0008,
+    }
     assert extract_custom_cost_per_token(
         {
             "litellm_metadata": {
@@ -984,6 +1008,48 @@ def test_extract_custom_cost_per_token_from_litellm_params_and_model_info():
     }
 
 
+def test_extract_custom_cost_per_token_from_pydantic_params():
+    both_sides = CustomPricingLiteLLMParams(
+        input_cost_per_token=1.2e-05,
+        output_cost_per_token=3.6e-05,
+    )
+    assert extract_custom_cost_per_token(both_sides) == {
+        "input_cost_per_token": 1.2e-05,
+        "output_cost_per_token": 3.6e-05,
+    }
+    input_only = CustomPricingLiteLLMParams(input_cost_per_token=1.2e-05)
+    assert extract_custom_cost_per_token(input_only) == {
+        "input_cost_per_token": 1.2e-05,
+    }
+
+
+def test_extract_custom_cost_per_token_rejects_non_mapping_sources():
+    assert extract_custom_cost_per_token("not-params") is None
+    assert extract_custom_cost_per_token([1, 2]) is None
+
+    class _UncallableDump:
+        model_dump = "not-callable"
+
+    assert extract_custom_cost_per_token(_UncallableDump()) is None
+
+    class _NonDictDump:
+        def model_dump(self):
+            return ["not", "a", "mapping"]
+
+    assert extract_custom_cost_per_token(_NonDictDump()) is None
+    assert extract_custom_cost_per_token({"metadata": "not-a-dict"}) is None
+    assert extract_custom_cost_per_token({"metadata": {"model_info": "x"}}) is None
+
+
+def test_complete_custom_cost_per_token_defensive_branches(_local_model_cost_map):
+    assert _complete_custom_cost_per_token(None, model="gpt-4o-mini", custom_llm_provider="openai") is None
+    assert _complete_custom_cost_per_token({}, model="gpt-4o-mini", custom_llm_provider="openai") is None
+    assert _custom_cost_per_token_from_logging_obj(None) is None
+    assert _published_token_rate(None, "openai", "input_cost_per_token") == 0.0
+    assert _published_token_rate("", "openai", "output_cost_per_token") == 0.0
+    assert _published_token_rate("gpt-4o-mini", "openai", "this_field_does_not_exist") == 0.0
+
+
 def test_completion_cost_unknown_anthropic_model_uses_litellm_params_rates():
     """Unknown anthropic models logged $0 on /v1/messages even when the
     deployment set input/output rates in litellm_params.
@@ -1111,6 +1177,175 @@ def test_anthropic_passthrough_unknown_model_spend_uses_litellm_params_rates():
     assert kwargs["response_cost"] > 0
 
 
+@pytest.mark.parametrize(
+    "declared",
+    [
+        {"input_cost_per_token": 1e-06},
+        {"output_cost_per_token": 5e-06},
+    ],
+    ids=["input-only", "output-only"],
+)
+def test_completion_cost_one_sided_custom_rate_keeps_published_other_side(
+    _local_model_cost_map, declared
+):
+    """A deployment may configure only one direction.
+
+    The missing side must keep the published price-map rate, not 0.
+    """
+    import time
+
+    from litellm.litellm_core_utils.litellm_logging import Logging as LiteLLMLoggingObj
+
+    model = "gpt-4o-mini"
+    published = litellm.get_model_info(model=model)
+    prompt_tokens = 100
+    completion_tokens = 20
+    input_cost = declared.get(
+        "input_cost_per_token", published["input_cost_per_token"]
+    )
+    output_cost = declared.get(
+        "output_cost_per_token", published["output_cost_per_token"]
+    )
+
+    logging_obj = LiteLLMLoggingObj(
+        model=model,
+        messages=[{"role": "user", "content": "Hi"}],
+        stream=False,
+        call_type="completion",
+        start_time=time.time(),
+        litellm_call_id="test-one-sided-custom-pricing",
+        function_id="test-fn",
+    )
+    logging_obj.update_environment_variables(
+        model=model,
+        user="",
+        optional_params={},
+        litellm_params={"custom_llm_provider": "openai", **declared},
+    )
+    logging_obj.model_call_details["custom_llm_provider"] = "openai"
+
+    response = ModelResponse(
+        id="test-id",
+        model=model,
+        choices=[],
+        usage=Usage(
+            prompt_tokens=prompt_tokens,
+            completion_tokens=completion_tokens,
+            total_tokens=prompt_tokens + completion_tokens,
+        ),
+    )
+    cost = completion_cost(
+        completion_response=response,
+        model=model,
+        custom_llm_provider="openai",
+        litellm_logging_obj=logging_obj,
+    )
+    expected = prompt_tokens * input_cost + completion_tokens * output_cost
+    assert cost == pytest.approx(expected)
+
+
+def test_completion_cost_one_sided_unknown_model_uses_zero_for_missing_side():
+    """Unmapped models have no published other-side rate, so that side is 0."""
+    import time
+
+    from litellm.litellm_core_utils.litellm_logging import Logging as LiteLLMLoggingObj
+
+    unknown_model = "litellm-unmapped-custom-priced-qwen-onesided"
+    input_cost = 1.2e-05
+    prompt_tokens = 100
+    completion_tokens = 20
+
+    logging_obj = LiteLLMLoggingObj(
+        model=unknown_model,
+        messages=[{"role": "user", "content": "Hi"}],
+        stream=False,
+        call_type="anthropic_messages",
+        start_time=time.time(),
+        litellm_call_id="test-unmapped-one-sided",
+        function_id="test-fn",
+    )
+    logging_obj.update_environment_variables(
+        model=unknown_model,
+        user="",
+        optional_params={},
+        litellm_params={
+            "custom_llm_provider": "anthropic",
+            "input_cost_per_token": input_cost,
+        },
+    )
+    logging_obj.model_call_details["custom_llm_provider"] = "anthropic"
+
+    response = ModelResponse(
+        id="test-id",
+        model=unknown_model,
+        choices=[],
+        usage=Usage(
+            prompt_tokens=prompt_tokens,
+            completion_tokens=completion_tokens,
+            total_tokens=prompt_tokens + completion_tokens,
+        ),
+    )
+    cost = completion_cost(
+        completion_response=response,
+        model=unknown_model,
+        custom_llm_provider="anthropic",
+        call_type="anthropic_messages",
+        custom_pricing=True,
+        litellm_logging_obj=logging_obj,
+    )
+    assert cost == pytest.approx(prompt_tokens * input_cost)
+
+
+def test_completion_cost_reads_nested_litellm_params_from_model_call_details():
+    import time
+
+    from litellm.litellm_core_utils.litellm_logging import Logging as LiteLLMLoggingObj
+
+    unknown_model = "litellm-unmapped-nested-litellm-params"
+    input_cost = 1.2e-05
+    output_cost = 3.6e-05
+    prompt_tokens = 100
+    completion_tokens = 20
+
+    logging_obj = LiteLLMLoggingObj(
+        model=unknown_model,
+        messages=[{"role": "user", "content": "Hi"}],
+        stream=False,
+        call_type="anthropic_messages",
+        start_time=time.time(),
+        litellm_call_id="test-nested-litellm-params",
+        function_id="test-fn",
+    )
+    logging_obj.litellm_params = None
+    logging_obj.model_call_details["litellm_params"] = {
+        "custom_llm_provider": "anthropic",
+        "input_cost_per_token": input_cost,
+        "output_cost_per_token": output_cost,
+    }
+    logging_obj.model_call_details["custom_llm_provider"] = "anthropic"
+
+    response = ModelResponse(
+        id="test-id",
+        model=unknown_model,
+        choices=[],
+        usage=Usage(
+            prompt_tokens=prompt_tokens,
+            completion_tokens=completion_tokens,
+            total_tokens=prompt_tokens + completion_tokens,
+        ),
+    )
+    cost = completion_cost(
+        completion_response=response,
+        model=unknown_model,
+        custom_llm_provider="anthropic",
+        call_type="anthropic_messages",
+        custom_pricing=True,
+        litellm_logging_obj=logging_obj,
+    )
+    expected = prompt_tokens * input_cost + completion_tokens * output_cost
+    assert cost == pytest.approx(expected)
+
+
 def test_per_request_custom_pricing_with_router():
     """When custom pricing is passed as per-request kwargs (not in model_list),
     _select_model_name_for_cost_calc should fall back to the model name