fix(mcp): prevent body_iter deadlock + use cached toolset lookup in responses API

- _stream_mcp_asgi_response: add done callback to handler_task that puts
  the EOF sentinel on body_queue when the task exits, preventing body_iter
  from hanging forever if the handler raises after headers are sent.
- litellm_proxy_mcp_handler: replace raw get_mcp_toolset_by_name() DB call
  with global_mcp_server_manager.get_toolset_by_name_cached() so toolset
  resolution uses the 60s TTL cache added for this purpose instead of
  hitting the DB on every responses-API request.

litellm/proxy/proxy_server.py

@@ -13532,6 +13532,14 @@ async def _stream_mcp_asgi_response(
 
     handler_task = asyncio.create_task(handle_fn(scope, receive, bridging_send))
 
+    # If the handler task dies (exception or cancellation) without sending the EOF
+    # sentinel, body_iter() would block forever on body_queue.get().  The callback
+    # below guarantees the queue gets unblocked regardless of how the task ends.
+    def _ensure_eof(task: asyncio.Task) -> None:
+        body_queue.put_nowait(None)
+
+    handler_task.add_done_callback(_ensure_eof)
+
     try:
         status, raw_headers = await asyncio.wait_for(
             asyncio.shield(headers_ready), timeout=30.0

litellm/responses/mcp/litellm_proxy_mcp_handler.py

@@ -170,13 +170,14 @@ class LiteLLM_Proxy_MCP_Handler:
                     from litellm.proxy._experimental.mcp_server.server import (
                         _apply_toolset_scope,
                     )
-                    from litellm.proxy._experimental.mcp_server.toolset_db import (
-                        get_mcp_toolset_by_name,
-                    )
                     from litellm.proxy.proxy_server import prisma_client
 
                     if prisma_client is not None and user_api_key_auth is not None:
-                        toolset = await get_mcp_toolset_by_name(prisma_client, name)
+                        toolset = (
+                            await global_mcp_server_manager.get_toolset_by_name_cached(
+                                prisma_client, name
+                            )
+                        )
                         if toolset is not None:
                             user_api_key_auth = await _apply_toolset_scope(
                                 user_api_key_auth, toolset.toolset_id