fix(mcp): attribute the agent veto for differently cased server names

litellm/proxy/_experimental/mcp_server/server.py

@@ -1414,13 +1414,10 @@ if MCP_AVAILABLE:
                 server_name_matched = False
 
                 for server in allowed_mcp_servers:
-                    if server:
-                        match_list = [s.lower() for s in iter_known_server_prefixes(server) if s]
-
-                        if server_or_group.lower() in match_list:
-                            filtered_server[server.server_id] = server
-                            server_name_matched = True
-                            break
+                    if server and _server_answers_to(server, server_or_group):
+                        filtered_server[server.server_id] = server
+                        server_name_matched = True
+                        break
 
                 if not server_name_matched:
                     try:
@@ -1450,6 +1447,10 @@ if MCP_AVAILABLE:
 
         return allowed_mcp_servers
 
+    def _server_answers_to(server: MCPServer, name: str) -> bool:
+        requested: Final = name.lower()
+        return any(requested == known.lower() for known in iter_known_server_prefixes(server) if known)
+
     class _McpDeniedDetail(TypedDict):
         error: ReadOnly[str]
 
@@ -1470,15 +1471,11 @@ if MCP_AVAILABLE:
                 mcp_servers=requested_names,
                 client_ip=client_ip,
             )
-            resolved_ids: Final = frozenset(server.server_id for server in resolved_without_agent)
 
-            def _registered_server_id(name: str) -> str | None:
-                server: Final = global_mcp_server_manager.get_mcp_server_by_name(name, client_ip=client_ip)
-                return server.server_id if server is not None else None
+            def _resolved_to_server(name: str) -> bool:
+                return any(_server_answers_to(server, name) for server in resolved_without_agent)
 
-            vetoed_server: Final = next(
-                (name for name in requested_names if _registered_server_id(name) in resolved_ids), None
-            )
+            vetoed_server: Final = next((name for name in requested_names if _resolved_to_server(name)), None)
             if vetoed_server is not None:
                 agent_denial: Final[_McpDeniedDetail] = {
                     "error": (
@@ -1493,7 +1490,7 @@ if MCP_AVAILABLE:
                 (
                     name
                     for name in requested_names
-                    if _registered_server_id(name) is None
+                    if not _resolved_to_server(name)
                     and any(name in (server.access_groups or ()) for server in resolved_without_agent)
                 ),
                 None,

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

@@ -2,6 +2,7 @@ import asyncio
 import contextvars
 import os
 from datetime import datetime, timedelta
+from types import SimpleNamespace
 from unittest.mock import AsyncMock, MagicMock, patch
 
 import pytest
@@ -1336,12 +1337,19 @@ def _denied_scope_manager(known_server_names_to_ids: dict[str, str]) -> MagicMoc
     return manager
 
 
-def _scope_resolver(resolved_without_agent: list[str], access_groups: tuple[str, ...] = ()) -> AsyncMock:
+def _scope_resolver(resolved_without_agent: dict[str, str], access_groups: tuple[str, ...] = ()) -> AsyncMock:
     async def resolve(user_api_key_auth, mcp_servers, client_ip=None):
         if user_api_key_auth is not None and user_api_key_auth.agent_id:
             return []
         return [
-            MagicMock(server_id=server_id, access_groups=list(access_groups)) for server_id in resolved_without_agent
+            SimpleNamespace(
+                server_id=server_id,
+                server_name=server_name,
+                alias=None,
+                short_prefix=None,
+                access_groups=list(access_groups),
+            )
+            for server_name, server_id in resolved_without_agent.items()
         ]
 
     return AsyncMock(side_effect=resolve)
@@ -1380,7 +1388,7 @@ async def test_scoped_list_denied_by_agent_binding_raises_403_naming_agent():
     pytest.importorskip("litellm.proxy._experimental.mcp_server.server")
 
     user_api_key_auth = UserAPIKeyAuth(api_key="test_key", user_id="test_user", agent_id="agent-123")
-    resolver = _scope_resolver(resolved_without_agent=["srv-github"])
+    resolver = _scope_resolver(resolved_without_agent={"github": "srv-github"})
 
     denial = await _denied_scoped_list(
         user_api_key_auth, ["github"], _denied_scope_manager({"github": "srv-github"}), resolver
@@ -1452,13 +1460,13 @@ async def test_scoped_list_unknown_name_raises_same_generic_403_as_unauthorized(
     user_api_key_auth = UserAPIKeyAuth(api_key="test_key", user_id="test_user", agent_id="agent-123")
 
     unknown = await _denied_scoped_list(
-        user_api_key_auth, ["github"], _denied_scope_manager({}), _scope_resolver(resolved_without_agent=[])
+        user_api_key_auth, ["github"], _denied_scope_manager({}), _scope_resolver(resolved_without_agent={})
     )
     unauthorized = await _denied_scoped_list(
         user_api_key_auth,
         ["github"],
         _denied_scope_manager({"github": "srv-github"}),
-        _scope_resolver(resolved_without_agent=[]),
+        _scope_resolver(resolved_without_agent={}),
     )
 
     assert unknown.status_code == unauthorized.status_code == 403
@@ -1479,7 +1487,7 @@ async def test_scoped_list_access_group_vetoed_by_agent_names_agent_and_group():
         user_api_key_auth,
         ["prod-group"],
         _denied_scope_manager({}),
-        _scope_resolver(resolved_without_agent=["srv-github"], access_groups=("prod-group",)),
+        _scope_resolver(resolved_without_agent={"github": "srv-github"}, access_groups=("prod-group",)),
     )
 
     assert denial.status_code == 403
@@ -1502,7 +1510,7 @@ async def test_scoped_list_mixed_unknown_and_vetoed_group_names_the_group_that_r
         user_api_key_auth,
         ["no-such-group", "prod-group"],
         _denied_scope_manager({}),
-        _scope_resolver(resolved_without_agent=["srv-github"], access_groups=("prod-group",)),
+        _scope_resolver(resolved_without_agent={"github": "srv-github"}, access_groups=("prod-group",)),
     )
 
     assert denial.status_code == 403
@@ -1519,7 +1527,7 @@ async def test_scoped_list_agent_key_denied_by_key_grants_raises_generic_403():
     pytest.importorskip("litellm.proxy._experimental.mcp_server.server")
 
     user_api_key_auth = UserAPIKeyAuth(api_key="test_key", user_id="test_user", agent_id="agent-123")
-    resolver = _scope_resolver(resolved_without_agent=[])
+    resolver = _scope_resolver(resolved_without_agent={})
 
     denial = await _denied_scoped_list(
         user_api_key_auth, ["github"], _denied_scope_manager({"github": "srv-github"}), resolver
@@ -1532,6 +1540,27 @@ async def test_scoped_list_agent_key_denied_by_key_grants_raises_generic_403():
     assert resolver.await_count == 2
 
 
+@pytest.mark.asyncio
+async def test_scoped_list_agent_veto_attributed_for_differently_cased_server_name():
+    """The scope filter matches `/mcp/GitHub` to a server named `github` case-insensitively, so the
+    agent-attributed 403 must match the same way instead of falling back to the generic denial."""
+    pytest.importorskip("litellm.proxy._experimental.mcp_server.server")
+
+    user_api_key_auth = UserAPIKeyAuth(api_key="test_key", user_id="test_user", agent_id="agent-123")
+
+    denial = await _denied_scoped_list(
+        user_api_key_auth,
+        ["GitHub"],
+        _denied_scope_manager({"github": "srv-github"}),
+        _scope_resolver(resolved_without_agent={"github": "srv-github"}),
+    )
+
+    assert denial.status_code == 403
+    message = denial.detail["error"]
+    assert "MCP server 'GitHub'" in message
+    assert "agent 'agent-123'" in message
+
+
 @pytest.mark.asyncio
 async def test_handle_list_tools_converts_permission_httpexception_to_mcp_error():
     """The MCP protocol handler surfaces a permission HTTPException as a clean JSON-RPC error