Merge pull request #41514 from BerriAI/litellm_mcp_api_key_static_header_slot

fix(mcp): count admin static headers as api_key credential slots

litellm/proxy/_experimental/mcp_server/openapi_to_mcp_generator.py

@@ -512,7 +512,7 @@ def create_tool_function(
             )
             from litellm.proxy._experimental.mcp_server.outbound_credentials.result import Error, Ok
 
-            match validate_static_credential(auth_type, effective_headers, upstream_token_header):
+            match validate_static_credential(auth_type, effective_headers, upstream_token_header, headers or ()):
                 case Error(error):
                     raise_public(error)
                 case Ok():

litellm/proxy/_experimental/mcp_server/outbound_credentials/adapter.py

@@ -13,7 +13,7 @@ from __future__ import annotations
 
 import base64
 import os
-from collections.abc import Mapping
+from collections.abc import Iterable, Mapping
 from typing import TYPE_CHECKING, Final, Literal, NoReturn
 
 from fastapi import HTTPException
@@ -426,16 +426,19 @@ def validate_static_credential(
     auth_type: MCPAuthType,
     headers: Mapping[str, str],
     upstream_token_header: str | None = None,
+    static_header_names: Iterable[str] = (),
 ) -> Result[None, CredError]:
     if auth_type not in _STATIC_MODES:
         return Ok(None)
     default_slot: Final = "X-API-Key" if auth_type == MCPAuth.api_key else "Authorization"
+    admin_chosen_slots: Final = tuple(static_header_names) if auth_type == MCPAuth.api_key else ()
     slots: Final = frozenset(
         name.lower()
         for name in (
             upstream_token_header or default_slot,
             default_slot,
             "Authorization",
+            *admin_chosen_slots,
         )
     )
     values: Final = tuple((name.lower(), value.strip()) for name, value in headers.items() if name.lower() in slots)
@@ -448,7 +451,9 @@ async def prepare_mcp_client(server: MCPServer, client: MCPClient) -> MCPClient:
     if server.auth_type not in _STATIC_MODES or client.transport_type == MCPTransport.stdio:
         return client
     request: Final = await client.prepare_request_auth()
-    match validate_static_credential(server.auth_type, request.headers, server.upstream_token_header):
+    match validate_static_credential(
+        server.auth_type, request.headers, server.upstream_token_header, server.static_headers or ()
+    ):
         case Error(error):
             raise_public(error)
         case Ok():

tests/test_litellm/proxy/_experimental/mcp_server/outbound_credentials/test_adapter.py

@@ -23,7 +23,7 @@ from litellm.proxy._experimental.mcp_server.outbound_credentials.adapter import
     to_subject,
     validate_static_credential,
 )
-from litellm.proxy._experimental.mcp_server.outbound_credentials.result import Ok
+from litellm.proxy._experimental.mcp_server.outbound_credentials.result import Error, Ok
 from litellm.proxy._experimental.mcp_server.outbound_credentials.types import (
     ApiKeyConfig,
     AuthorizationCodeConfig,
@@ -59,6 +59,22 @@ def test_static_credential_preserves_supported_api_key_and_raw_headers(
     assert isinstance(result, Ok)
 
 
+@pytest.mark.parametrize("auth_type,headers,static_header_names,expected", [
+    (MCPAuth.api_key, {"apikey": "static-key"}, ("apikey",), Ok),
+    (MCPAuth.api_key, {"apikey": "static-key", "X-API-Key": ""}, ("apikey",), Ok),
+    (MCPAuth.api_key, {"apikey": ""}, ("apikey",), Error),
+    (MCPAuth.api_key, {"apikey": "static-key"}, (), Error),
+    (MCPAuth.api_key, {"apikey": "static-key"}, ("X-Tenant",), Error),
+    (MCPAuth.bearer_token, {"apikey": "static-key"}, ("apikey",), Error),
+    (MCPAuth.token, {"apikey": "static-key"}, ("apikey",), Error),
+])
+def test_static_credential_counts_api_key_static_headers_only(
+    auth_type: MCPAuthType, headers: dict[str, str], static_header_names: tuple[str, ...], expected: type,
+) -> None:
+    result: Final = validate_static_credential(auth_type, headers, static_header_names=static_header_names)
+    assert isinstance(result, expected)
+
+
 def _server(**kwargs) -> MCPServer:
     return MCPServer(server_id="s", name="n", transport=MCPTransport.http, **kwargs)
 

tests/test_litellm/proxy/_experimental/mcp_server/test_mcp_server_manager.py

@@ -13652,6 +13652,28 @@ class TestProtectedCredentialPreparation:
         assert client._credential_slot == "X-Custom"
         assert await client.discovery_auth_fingerprint()
 
+    @pytest.mark.asyncio
+    @pytest.mark.parametrize("static_headers,accepted", [
+        ({"apikey": "static-key"}, True),
+        ({"apikey": ""}, False),
+        ({"X-Tenant": "tenant"}, True),
+    ])
+    async def test_api_key_carried_by_static_header_passes_fail_closed_check(
+        self, static_headers: dict[str, str], accepted: bool
+    ) -> None:
+        server: Final = MCPServer(
+            server_id="static-slot", name="static-slot", url="https://upstream.example/mcp",
+            transport=MCPTransport.http, auth_type=MCPAuth.api_key, static_headers=static_headers,
+        )
+        if not accepted:
+            with pytest.raises(HTTPException) as exc:
+                await MCPServerManager()._create_mcp_client(server, extra_headers=dict(static_headers))
+            assert exc.value.status_code == 500
+            return
+        client: Final = await MCPServerManager()._create_mcp_client(server, extra_headers=dict(static_headers))
+        request: Final = await client.prepare_request_auth()
+        assert all(request.headers[name] == value for name, value in static_headers.items())
+
     @pytest.mark.asyncio
     @pytest.mark.parametrize("static,forwarded,caller", [
         ({"X-API-Key": "static"}, {"x-api-key": "forwarded"}, None),

tests/test_litellm/proxy/_experimental/mcp_server/test_openapi_to_mcp_generator.py

@@ -133,6 +133,26 @@ async def test_static_auth_uses_configured_custom_header(
         assert destination.call_count == 0
 
 
+@pytest.mark.asyncio
+@pytest.mark.parametrize("credential", ["static-key", ""])
+async def test_static_auth_accepts_api_key_carried_by_static_header(
+    respx_mock: MockRouter, monkeypatch: pytest.MonkeyPatch, credential: str,
+) -> None:
+    monkeypatch.setenv("DISABLE_AIOHTTP_TRANSPORT", "True")
+    tool: Final = create_tool_function(
+        "/echo", "get", {}, "https://upstream.example", headers={"apikey": credential}, auth_type=MCPAuth.api_key,
+    )
+    destination: Final = respx_mock.get("https://upstream.example/echo").respond(200, text="authenticated")
+    if credential:
+        assert await tool() == "authenticated"
+        assert destination.calls.last.request.headers["apikey"] == credential
+        assert "x-api-key" not in destination.calls.last.request.headers
+    else:
+        with pytest.raises(HTTPException, match="requires a usable upstream credential"):
+            await tool()
+        assert destination.call_count == 0
+
+
 @pytest.mark.asyncio
 @pytest.mark.parametrize("auth_type,resolved", [
     (MCPAuth.none, None),