Fix MCP settings apply NameError

Use the active settings dictionary when scheduling MCP config updates so applying global MCP servers no longer references an undefined config variable.

Add a focused regression test covering the settings apply path and document the deferred MCP update contract in settings.py DOX.

helpers/settings.py

@@ -648,7 +648,7 @@ def _apply_settings(previous: Settings | None, browser_timezone: str | None = No
                 )
 
             task2 = defer.DeferredTask().start_task(
-                update_mcp_settings, config.mcp_servers
+                update_mcp_settings, _settings["mcp_servers"]
             )  # TODO overkill, replace with background task
 
         # update token in mcp server

helpers/settings.py.dox.md

@@ -63,6 +63,7 @@
 
 - Important called helpers/classes observed in the source: `TypeVar`, `files.get_abs_path`, `dotenv.get_dotenv_value`, `opts.insert`, `str.strip`, `_is_valid_timezone`, `str.strip.lower`, `_normalize_timezone_setting`, `SettingsOutput`, `get_default_settings`, `_ensure_option_present`, `_resolve_runtime_timezone`, `get_default_secrets_manager`, `get_settings`, `normalize_settings`, `_load_sensitive_settings`, `settings.copy`, `_write_settings_file`, `reload_settings`, `set_settings`, `initialize_agent`.
 - Applying settings refreshes active context configs while preserving each subordinate agent's own profile.
+- Applying settings starts a deferred `MCPConfig.update(...)` with the current `mcp_servers` string when global MCP server settings change.
 - Keep request/response, tool, or helper semantics documented here at the same time as source changes.
 
 ## Work Guidance

tests/test_settings_mcp.py

@@ -0,0 +1,81 @@
+import asyncio
+import sys
+from pathlib import Path
+from types import ModuleType
+
+PROJECT_ROOT = Path(__file__).resolve().parents[1]
+if str(PROJECT_ROOT) not in sys.path:
+    sys.path.insert(0, str(PROJECT_ROOT))
+
+import helpers.settings as settings_module
+
+
+def test_apply_settings_updates_mcp_from_current_settings(monkeypatch):
+    base_settings = settings_module.get_default_settings()
+    previous_mcp_servers = '{"mcpServers": {}}'
+    current_mcp_servers = '{"mcpServers": {"deepwiki": {"url": "https://mcp.deepwiki.com/mcp"}}}'
+    previous = {
+        **base_settings,
+        "mcp_servers": previous_mcp_servers,
+        "mcp_server_token": "unchanged-token",
+    }
+    current = {
+        **base_settings,
+        "mcp_servers": current_mcp_servers,
+        "mcp_server_token": "unchanged-token",
+    }
+    received_mcp_servers: list[str] = []
+
+    class FakeDeferredTask:
+        def start_task(self, func, *args, **kwargs):
+            asyncio.run(func(*args, **kwargs))
+            return self
+
+    class FakePrintStyle:
+        def __init__(self, *args, **kwargs):
+            pass
+
+        def print(self, *args, **kwargs):
+            pass
+
+    class FakeMCPConfig:
+        @classmethod
+        def get_instance(cls):
+            return cls()
+
+        @classmethod
+        def update(cls, mcp_servers):
+            received_mcp_servers.append(mcp_servers)
+
+        def model_dump_json(self):
+            return "{}"
+
+    agent_stub = ModuleType("agent")
+    agent_stub.Agent = object
+
+    class FakeAgentContext:
+        @staticmethod
+        def all():
+            return []
+
+    agent_stub.AgentContext = FakeAgentContext
+
+    initialize_stub = ModuleType("initialize")
+    initialize_stub.initialize_agent = lambda override_settings=None: None
+
+    mcp_handler_stub = ModuleType("helpers.mcp_handler")
+    mcp_handler_stub.MCPConfig = FakeMCPConfig
+
+    monkeypatch.setitem(sys.modules, "agent", agent_stub)
+    monkeypatch.setitem(sys.modules, "initialize", initialize_stub)
+    monkeypatch.setitem(sys.modules, "helpers.mcp_handler", mcp_handler_stub)
+    monkeypatch.setattr(settings_module, "_settings", current)
+    monkeypatch.setattr(settings_module, "_apply_timezone_setting", lambda *args, **kwargs: None)
+    monkeypatch.setattr(settings_module.defer, "DeferredTask", FakeDeferredTask)
+    monkeypatch.setattr(settings_module, "PrintStyle", FakePrintStyle)
+    monkeypatch.setattr(settings_module.NotificationManager, "send_notification", lambda **kwargs: None)
+    monkeypatch.setattr(settings_module, "create_auth_token", lambda: "unchanged-token")
+
+    settings_module._apply_settings(previous)
+
+    assert received_mcp_servers == [current_mcp_servers]