refactor: thread app_config through lead and subagent task path (#2666)

* refactor: thread app config through lead prompt

* fix: honor explicit app config across runtime paths

* style: format subagent executor tests

* fix: thread resolved app config and guard subagents-only fallback

Address two PR review findings:

1. _create_summarization_middleware passed the original (possibly None)
   app_config into create_chat_model, forcing the model factory back to
   ambient get_app_config() and risking config drift between the
   middleware's resolved view and the model's view. Pass the resolved
   AppConfig instance through end-to-end.

2. get_available_subagent_names accepted Any-typed config and forwarded
   it to is_host_bash_allowed, which reads ``.sandbox``. A
   SubagentsAppConfig (also accepted upstream as a sum-type input) has
   no ``.sandbox`` attribute and would be silently treated as "no
   sandbox configured", incorrectly disabling the bash subagent. Guard
   on hasattr and fall back to ambient lookup otherwise.

Adds regression tests for both paths.

* chore: simplify hasattr guard and tighten regression tests

- Collapse if/else into ternary in get_available_subagent_names; hasattr(None, ...) is False so the explicit None check was redundant.
- Drop comments that narrate the change rather than explain non-obvious WHY (test names already convey intent).
- Replace stringly-typed sentinel "no-arg" in regression test with direct args tuple comparison.

---------

Co-authored-by: greatmengqi <chenmengqi.0376@bytedance.com>

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

@@ -19,8 +19,6 @@ from deerflow.agents.middlewares.view_image_middleware import ViewImageMiddlewar
 from deerflow.agents.thread_state import ThreadState
 from deerflow.config.agents_config import load_agent_config, validate_agent_name
 from deerflow.config.app_config import AppConfig, get_app_config
-from deerflow.config.memory_config import get_memory_config
-from deerflow.config.summarization_config import get_summarization_config
 from deerflow.models import create_chat_model
 
 logger = logging.getLogger(__name__)
@@ -52,7 +50,8 @@ def _resolve_model_name(requested_model_name: str | None = None, *, app_config:
 
 def _create_summarization_middleware(*, app_config: AppConfig | None = None) -> DeerFlowSummarizationMiddleware | None:
     """Create and configure the summarization middleware from config."""
-    config = get_summarization_config()
+    resolved_app_config = app_config or get_app_config()
+    config = resolved_app_config.summarization
 
     if not config.enabled:
         return None
@@ -73,9 +72,9 @@ def _create_summarization_middleware(*, app_config: AppConfig | None = None) ->
     # as middleware rather than lead_agent (SummarizationMiddleware is a
     # LangChain built-in, so we tag the model at creation time).
     if config.model_name:
-        model = create_chat_model(name=config.model_name, thinking_enabled=False, app_config=app_config)
+        model = create_chat_model(name=config.model_name, thinking_enabled=False, app_config=resolved_app_config)
     else:
-        model = create_chat_model(thinking_enabled=False, app_config=app_config)
+        model = create_chat_model(thinking_enabled=False, app_config=resolved_app_config)
     model = model.with_config(tags=["middleware:summarize"])
 
     # Prepare kwargs
@@ -92,18 +91,13 @@ def _create_summarization_middleware(*, app_config: AppConfig | None = None) ->
         kwargs["summary_prompt"] = config.summary_prompt
 
     hooks: list[BeforeSummarizationHook] = []
-    if get_memory_config().enabled:
+    if resolved_app_config.memory.enabled:
         hooks.append(memory_flush_hook)
 
     # The logic below relies on two assumptions holding true: this factory is
     # the sole entry point for DeerFlowSummarizationMiddleware, and the runtime
     # config is not expected to change after startup.
-    try:
-        resolved_app_config = app_config or get_app_config()
-        skills_container_path = resolved_app_config.skills.container_path or "/mnt/skills"
-    except Exception:
-        logger.exception("Failed to resolve skills container path; falling back to default")
-        skills_container_path = "/mnt/skills"
+    skills_container_path = resolved_app_config.skills.container_path or "/mnt/skills"
 
     return DeerFlowSummarizationMiddleware(
         **kwargs,
@@ -279,10 +273,10 @@ def _build_middlewares(
         middlewares.append(TokenUsageMiddleware())
 
     # Add TitleMiddleware
-    middlewares.append(TitleMiddleware())
+    middlewares.append(TitleMiddleware(app_config=resolved_app_config))
 
     # Add MemoryMiddleware (after TitleMiddleware)
-    middlewares.append(MemoryMiddleware(agent_name=agent_name))
+    middlewares.append(MemoryMiddleware(agent_name=agent_name, memory_config=resolved_app_config.memory))
 
     # Add ViewImageMiddleware only if the current model supports vision.
     # Use the resolved runtime model_name from make_lead_agent to avoid stale config values.
@@ -316,7 +310,9 @@ def _build_middlewares(
 
 def make_lead_agent(config: RunnableConfig):
     """LangGraph graph factory; keep the signature compatible with LangGraph Server."""
-    return _make_lead_agent(config, app_config=get_app_config())
+    runtime_config = _get_runtime_config(config)
+    runtime_app_config = runtime_config.get("app_config")
+    return _make_lead_agent(config, app_config=runtime_app_config or get_app_config())
 
 
 def _make_lead_agent(config: RunnableConfig, *, app_config: AppConfig):