refactor(api): make tool_handlers require a DeviceManager

Eliminates the silent fallback to DEFAULT_MANAGER that produced the
DeviceNotFoundError incident. All existing callers already pass
manager explicitly.

api/mcp.py

@@ -3,7 +3,7 @@ from collections.abc import Callable
 from typing import Any
 
 from api.errors import call_with_semantic_errors
-from device.manager import DEFAULT_MANAGER, DeviceManager
+from device.manager import DeviceManager
 from tools.describe_screen import describe_screen
 from tools.find_icon import find_icon_on_screen
 from tools.find_text import find_text_on_screen
@@ -17,12 +17,11 @@ from tools.ui_tree import get_ui_tree
 
 def tool_handlers(
     *,
-    manager: DeviceManager | None = None,
+    manager: DeviceManager,
 ) -> dict[str, Callable[..., Any]]:
-    device_manager = manager or DEFAULT_MANAGER
 
     def _screenshot(device_id: str | None = None) -> dict[str, Any]:
-        image = take_screenshot(device_id, manager=device_manager)
+        image = take_screenshot(device_id, manager=manager)
         return {
             "ok": True,
             "image_base64": base64.b64encode(image).decode("ascii"),
@@ -39,7 +38,7 @@ def tool_handlers(
             x,
             y,
             device_id=device_id,
-            manager=device_manager,
+            manager=manager,
         ),
         "swipe": lambda start_x, start_y, end_x, end_y, duration_ms=500, device_id=None: call_with_semantic_errors(
             swipe,
@@ -49,55 +48,55 @@ def tool_handlers(
             end_y,
             duration_ms=duration_ms,
             device_id=device_id,
-            manager=device_manager,
+            manager=manager,
         ),
         "input_text": lambda text, device_id=None: call_with_semantic_errors(
             input_text,
             text,
             device_id=device_id,
-            manager=device_manager,
+            manager=manager,
         ),
         "launch_app": lambda app_id, device_id=None: call_with_semantic_errors(
             launch_app,
             app_id,
             device_id=device_id,
-            manager=device_manager,
+            manager=manager,
         ),
         "find_text": lambda query, device_id=None: call_with_semantic_errors(
             find_text_on_screen,
             query,
             device_id=device_id,
-            manager=device_manager,
+            manager=manager,
         ),
         "find_icon": lambda name, device_id=None: call_with_semantic_errors(
             find_icon_on_screen,
             name,
             device_id=device_id,
-            manager=device_manager,
+            manager=manager,
         ),
         "get_ui_tree": lambda device_id=None, include_app_info=False: (
             call_with_semantic_errors(
                 get_ui_tree,
                 device_id,
-                manager=device_manager,
+                manager=manager,
                 include_app_info=include_app_info,
             )
         ),
         "describe_screen": lambda device_id=None: call_with_semantic_errors(
-            lambda: describe_screen(device_id, manager=device_manager).to_dict()
+            lambda: describe_screen(device_id, manager=manager).to_dict()
         ),
         "list_devices": lambda: [
-            device.to_dict() for device in device_manager.list_devices()
+            device.to_dict() for device in manager.list_devices()
         ],
         "device_status": lambda device_id: call_with_semantic_errors(
-            lambda: {"device_id": device_id, "status": device_manager.status(device_id)}
+            lambda: {"device_id": device_id, "status": manager.status(device_id)}
         ),
     }
 
 
 def create_mcp_server(
     *,
-    manager: DeviceManager | None = None,
+    manager: DeviceManager,
     skill_catalog_store: Any | None = None,
     skill_active_subscriptions: set[str] | None = None,
     skill_local_store: Any | None = None,
@@ -107,6 +106,9 @@ def create_mcp_server(
     except ImportError as exc:
         raise RuntimeError("mcp SDK is not installed") from exc
 
+    if manager is None:
+        raise ValueError("create_mcp_server requires a non-None manager")
+
     handlers = tool_handlers(manager=manager)
     server = FastMCP("apex-agent")
 

tests/test_mcp.py

@@ -64,3 +64,12 @@ def test_mcp_ui_tree_can_include_active_app_info() -> None:
         "activity": ".MainActivity",
     }
     assert isinstance(response["nodes"], list)
+
+
+def test_tool_handlers_requires_manager() -> None:
+    """D12: tool_handlers must not silently fall back to DEFAULT_MANAGER."""
+    from api.mcp import tool_handlers
+    import pytest
+
+    with pytest.raises(TypeError):
+        tool_handlers()  # type: ignore[call-arg]