deer-flow/backend/tests/test_subagent_checkpointer_isolation.py

"""Regression test: subagent _create_agent() must isolate from parent run checkpointer.

When a parent run carries a synchronous checkpointer (e.g. SqliteSaver via
DeerFlowClient), the subagent's ``agent.astream()`` inherits it through
``copy_context()`` + ``ensure_config()``. Without ``checkpointer=False``
at compile time, LangGraph's resolution prioritizes the inherited value
and calls the sync checkpointer's async methods, raising NotImplementedError.

The subagent is a one-shot delegation — it rebuilds state, calls astream
once, and extracts the last AIMessage. It never resumes, so persistence
is unnecessary and inheriting the parent checkpointer is harmful.
"""

import sys
from types import ModuleType, SimpleNamespace
from unittest.mock import MagicMock

import pytest

# Module names mocked to break circular imports (same set as test_subagent_executor.py)
_MOCKED_MODULE_NAMES = [
    "deerflow.agents",
    "deerflow.agents.thread_state",
    "deerflow.agents.middlewares",
    "deerflow.agents.middlewares.thread_data_middleware",
    "deerflow.sandbox",
    "deerflow.sandbox.middleware",
    "deerflow.sandbox.security",
    "deerflow.models",
    "deerflow.skills.storage",
]


def _default_app_config():
    return SimpleNamespace(tool_search=SimpleNamespace(enabled=False))


def _clear_stale_executor_package_attr() -> None:
    subagents_pkg = sys.modules.get("deerflow.subagents")
    if subagents_pkg is not None and hasattr(subagents_pkg, "executor"):
        delattr(subagents_pkg, "executor")


@pytest.fixture(autouse=True)
def _setup_executor_module():
    """Set up mocked modules and import the real executor (same pattern as test_subagent_executor.py)."""
    original_modules = {name: sys.modules.get(name) for name in _MOCKED_MODULE_NAMES}
    original_executor = sys.modules.get("deerflow.subagents.executor")

    if "deerflow.subagents.executor" in sys.modules:
        del sys.modules["deerflow.subagents.executor"]
    _clear_stale_executor_package_attr()

    for name in _MOCKED_MODULE_NAMES:
        sys.modules[name] = MagicMock()
    storage_module = ModuleType("deerflow.skills.storage")
    storage_module.get_or_new_skill_storage = lambda **kwargs: SimpleNamespace(load_skills=lambda *, enabled_only: [])
    sys.modules["deerflow.skills.storage"] = storage_module

    from deerflow.subagents.config import SubagentConfig
    from deerflow.subagents.executor import SubagentExecutor

    executor_module = sys.modules["deerflow.subagents.executor"]
    executor_module.get_app_config = _default_app_config

    yield {
        "SubagentConfig": SubagentConfig,
        "SubagentExecutor": SubagentExecutor,
        "executor_module": executor_module,
    }

    for name in _MOCKED_MODULE_NAMES:
        if original_modules[name] is not None:
            sys.modules[name] = original_modules[name]
        elif name in sys.modules:
            del sys.modules[name]

    if original_executor is not None:
        sys.modules["deerflow.subagents.executor"] = original_executor
    elif "deerflow.subagents.executor" in sys.modules:
        del sys.modules["deerflow.subagents.executor"]


class TestSubagentCheckpointerIsolation:
    """Verify _create_agent() unconditionally passes checkpointer=False to create_agent()."""

    def test_create_agent_receives_checkpointer_false(
        self,
        _setup_executor_module,
        monkeypatch: pytest.MonkeyPatch,
    ):
        """Assert checkpointer=False is always passed to create_agent()."""
        SubagentConfig = _setup_executor_module["SubagentConfig"]
        SubagentExecutor = _setup_executor_module["SubagentExecutor"]
        executor_module = _setup_executor_module["executor_module"]

        captured_kwargs: dict = {}

        def fake_create_agent(**kwargs):
            captured_kwargs.update(kwargs)
            agent = MagicMock()
            agent.checkpointer = False
            return agent

        def fake_build_subagent_runtime_middlewares(**kwargs):
            return []

        monkeypatch.setattr(executor_module, "create_agent", fake_create_agent)
        mw_module = ModuleType("deerflow.agents.middlewares.tool_error_handling_middleware")
        mw_module.build_subagent_runtime_middlewares = fake_build_subagent_runtime_middlewares
        monkeypatch.setitem(
            sys.modules,
            "deerflow.agents.middlewares.tool_error_handling_middleware",
            mw_module,
        )

        executor = SubagentExecutor(
            config=SubagentConfig(
                name="test",
                description="test",
                system_prompt="You are a test agent.",
            ),
            tools=[],
        )

        # Simulate lazy model_name resolution
        def fake_create_chat_model(**kwargs):
            return MagicMock()

        executor.model_name = "test-model"
        executor._base_tools = []

        monkeypatch.setattr(executor_module, "create_chat_model", fake_create_chat_model)
        monkeypatch.setattr(executor_module, "resolve_subagent_model_name", lambda config, parent, app_config=None: "test-model")

        result = executor._create_agent()

        assert captured_kwargs.get("checkpointer") is False, f"Expected checkpointer=False in create_agent() kwargs, got: {captured_kwargs.get('checkpointer')!r}"
        assert result.checkpointer is False