fix(proxy): drop a forged spend logs metadata header from provider_specific_header

The provider handlers merge provider_specific_header over data["headers"] last of all, so a caller copy there made the upstream proxy record an attribution this proxy never logged. The strip now walks every request-body header dict the handlers merge, not just extra_headers.

litellm/proxy/litellm_pre_call_utils.py

@@ -4,7 +4,7 @@ import json
 import re
 import time
 from collections import OrderedDict
-from collections.abc import Mapping, MutableMapping, Sequence
+from collections.abc import Iterator, Mapping, MutableMapping, Sequence
 from datetime import datetime
 from types import MappingProxyType
 from typing import TYPE_CHECKING, Any, Final, cast
@@ -1266,6 +1266,20 @@ class LiteLLMProxyRequestSetup:
             return None
         return encoded
 
+    @staticmethod
+    def _caller_supplied_header_dicts(
+        data: Mapping[str, object],
+    ) -> Iterator[dict]:  # mutable-ok: the caller deletes the forged key out of each one
+        """Every request-body dict a provider handler merges over ``data["headers"]``."""
+        extra_headers: Final = data.get("extra_headers")
+        if isinstance(extra_headers, dict):
+            yield extra_headers
+        provider_specific: Final = data.get("provider_specific_header")
+        for entry in provider_specific if isinstance(provider_specific, list) else [provider_specific]:
+            scoped = entry.get("extra_headers") if isinstance(entry, dict) else None  # rebind-ok: loop-local
+            if isinstance(scoped, dict):
+                yield scoped
+
     @staticmethod
     def add_spend_logs_metadata_to_llm_call_headers(
         data: MutableMapping[str, object],  # mutable-ok: this helper writes the outbound header into it
@@ -1288,15 +1302,15 @@ class LiteLLMProxyRequestSetup:
         if not general_settings or general_settings.get("forward_spend_logs_metadata_to_llm_api") is not True:
             return
 
-        # Past the opt-in gate the proxy owns this header, and `extra_headers` beats
-        # `headers` in every provider handler, so a caller copy left in the request body
-        # would forge the attribution the upstream records whenever nothing is emitted
-        caller_extra_headers: Final = data.get("extra_headers")
-        if isinstance(caller_extra_headers, dict):
+        # Past the opt-in gate the proxy owns this header, and both `extra_headers` and
+        # `provider_specific_header` are merged over `headers` by the provider handlers,
+        # so a caller copy left in the request body would forge the attribution the
+        # upstream records even when this proxy resolved and logged a different one
+        for caller_headers in LiteLLMProxyRequestSetup._caller_supplied_header_dicts(data):
             for key in [
-                k for k in caller_extra_headers if isinstance(k, str) and k.lower() == SPEND_LOGS_METADATA_HEADER_NAME
+                k for k in caller_headers if isinstance(k, str) and k.lower() == SPEND_LOGS_METADATA_HEADER_NAME
             ]:
-                del caller_extra_headers[key]  # rebind-ok: dropping the forged copy is the point
+                del caller_headers[key]  # rebind-ok: dropping the forged copy is the point
 
         encoded: Final = LiteLLMProxyRequestSetup._encode_spend_logs_metadata_header(data.get(_metadata_variable_name))
 

tests/test_litellm/proxy/test_litellm_pre_call_utils.py

@@ -4387,6 +4387,7 @@ async def test_bearer_token_not_in_debug_logs():
 # =====================================================================# Tests for credential overrides from model_config (team/project metadata)
 # =====================================================================
 
+
 @pytest.fixture()
 def setup_test_credentials():
     """Populate litellm.credential_list with test credentials and enable feature flag, clean up after."""
@@ -5612,6 +5613,7 @@ class TestApplyKeyTagsPreAuth:
 # user-facing model name has no provider prefix.
 # =====================================================================
 
+
 def test_resolve_provider_from_deployment_uses_litellm_params_model():
     """When custom_llm_provider is unset, fall back to the prefix of model."""
     router = MagicMock()
@@ -7741,9 +7743,7 @@ def _proxy_chain_auth(
     return UserAPIKeyAuth(
         api_key="hashed-key",
         metadata=(
-            metadata
-            if metadata is not None
-            else {"spend_logs_metadata": {"user_id": "U0099887", "username": "jdoe"}}
+            metadata if metadata is not None else {"spend_logs_metadata": {"user_id": "U0099887", "username": "jdoe"}}
         ),
         team_metadata=(
             team_metadata
@@ -7802,6 +7802,55 @@ async def test_forward_spend_logs_metadata_overrides_caller_supplied_extra_heade
     )
 
 
+@pytest.mark.asyncio
+@pytest.mark.parametrize(
+    "provider_specific_header",
+    [
+        {
+            "custom_llm_provider": "openai",
+            "extra_headers": {SPEND_LOGS_METADATA_HEADER_NAME: json.dumps({"user_id": "forged"})},
+        },
+        [
+            {"custom_llm_provider": "anthropic", "extra_headers": {"anthropic-beta": "v1"}},
+            {
+                "custom_llm_provider": "openai",
+                "extra_headers": {SPEND_LOGS_METADATA_HEADER_NAME: json.dumps({"user_id": "forged"})},
+            },
+        ],
+    ],
+    ids=["single", "list"],
+)
+async def test_forward_spend_logs_metadata_overrides_caller_supplied_provider_specific_header(
+    provider_specific_header: object,
+):
+    """
+    `provider_specific_header` is merged over `headers` last of all, so a caller copy there
+    forged the attribution the upstream recorded while this proxy logged its own resolved value.
+    """
+    updated = await add_litellm_data_to_request(
+        data={
+            "model": "gpt-4o",
+            "messages": [],
+            "provider_specific_header": provider_specific_header,
+        },
+        request=_spend_logs_metadata_request(),
+        user_api_key_dict=_proxy_chain_auth(),
+        proxy_config=MagicMock(),
+        general_settings={"forward_spend_logs_metadata_to_llm_api": True},
+    )
+
+    assert json.loads(updated["headers"][SPEND_LOGS_METADATA_HEADER_NAME])["user_id"] == "U0099887"
+    scoped = updated["provider_specific_header"]
+    entries = scoped if isinstance(scoped, list) else [scoped]
+    for entry in entries:
+        assert SPEND_LOGS_METADATA_HEADER_NAME not in entry["extra_headers"], (
+            "the caller's copy must be dropped so the proxy's resolved value is what ships"
+        )
+    assert [e["extra_headers"] for e in entries if e["extra_headers"]] == (
+        [{"anthropic-beta": "v1"}] if len(entries) > 1 else []
+    ), "only the forged key goes, every other scoped header the caller sent survives"
+
+
 @pytest.mark.asyncio
 @pytest.mark.parametrize(
     "key_metadata",