fix(subagent): inherit parent agent's tool_groups in task_tool (#2305)

* fix(subagent): inherit parent agent's tool_groups in task_tool

When a custom agent defines tool_groups (e.g. [file:read, file:write, bash]),
the restriction is correctly applied to the lead agent. However, when the lead
agent delegates work to a subagent via the task tool, get_available_tools() is
called without the groups parameter, causing the subagent to receive ALL tools
(including web_search, web_fetch, image_search, etc.) regardless of the parent
agent's configuration.

This fix propagates tool_groups through run metadata so that task_tool passes
the same group filter when building the subagent's tool set.

Changes:
- agent.py: include tool_groups in run metadata
- task_tool.py: read tool_groups from metadata and pass to get_available_tools()

* fix: initialize metadata before conditional block and update tests for tool_groups propagation

- Initialize metadata = {} before the 'if runtime is not None' block to
  avoid Ruff F821 (possibly-undefined variable) and simplify the
  parent_tool_groups expression.
- Update existing test assertion to expect groups=None in
  get_available_tools call signature.
- Add 3 new test cases:
  - test_task_tool_propagates_tool_groups_to_subagent
  - test_task_tool_no_tool_groups_passes_none
  - test_task_tool_runtime_none_passes_groups_none

backend/packages/harness/deerflow/agents/lead_agent/agent.py

@@ -332,6 +332,7 @@ def make_lead_agent(config: RunnableConfig):
             "reasoning_effort": reasoning_effort,
             "is_plan_mode": is_plan_mode,
             "subagent_enabled": subagent_enabled,
+            "tool_groups": agent_config.tool_groups if agent_config else None,
         }
     )
 

backend/packages/harness/deerflow/tools/builtins/task_tool.py

@@ -88,6 +88,7 @@ async def task_tool(
     thread_id = None
     parent_model = None
     trace_id = None
+    metadata: dict = {}
 
     if runtime is not None:
         sandbox_state = runtime.state.get("sandbox")
@@ -107,8 +108,11 @@ async def task_tool(
     # Lazy import to avoid circular dependency
     from deerflow.tools import get_available_tools
 
+    # Inherit parent agent's tool_groups so subagents respect the same restrictions
+    parent_tool_groups = metadata.get("tool_groups")
+
     # Subagents should not have subagent tools enabled (prevent recursive nesting)
-    tools = get_available_tools(model_name=parent_model, subagent_enabled=False)
+    tools = get_available_tools(model_name=parent_model, groups=parent_tool_groups, subagent_enabled=False)
 
     # Create executor
     executor = SubagentExecutor(