refactor(config): eliminate global mutable state, wire DeerFlowContext into runtime

- Freeze all config models (AppConfig + 15 sub-configs) with frozen=True
- Purify from_file() — remove 9 load_*_from_dict() side-effect calls
- Replace mtime/reload/push/pop machinery with single ContextVar + init_app_config()
- Delete 10 sub-module globals and their getters/setters/loaders
- Migrate 50+ consumers from get_*_config() to get_app_config().xxx

- Expand DeerFlowContext: app_config + thread_id + agent_name (frozen dataclass)
- Wire into Gateway runtime (worker.py) and DeerFlowClient via context= parameter
- Remove sandbox_id from runtime.context — flows through ThreadState.sandbox only
- Middleware/tools access runtime.context directly via Runtime[DeerFlowContext] generic
- resolve_context() retained at server entry points for LangGraph Server fallback

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

@@ -33,7 +33,7 @@ def _normalize_presented_filepath(
     if runtime.state is None:
         raise ValueError("Thread runtime state is not available")
 
-    thread_id = runtime.context.get("thread_id") if runtime.context else None
+    thread_id = runtime.context.thread_id
     if not thread_id:
         raise ValueError("Thread ID is not available in runtime context")
 

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

@@ -24,7 +24,7 @@ def setup_agent(
         description: One-line description of what the agent does.
     """
 
-    agent_name: str | None = runtime.context.get("agent_name") if runtime.context else None
+    agent_name: str | None = runtime.context.agent_name
 
     try:
         paths = get_paths()

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

@@ -92,9 +92,7 @@ async def task_tool(
     if runtime is not None:
         sandbox_state = runtime.state.get("sandbox")
         thread_data = runtime.state.get("thread_data")
-        thread_id = runtime.context.get("thread_id") if runtime.context else None
-        if thread_id is None:
-            thread_id = runtime.config.get("configurable", {}).get("thread_id")
+        thread_id = runtime.context.thread_id
 
         # Try to get parent model from configurable
         metadata = runtime.config.get("metadata", {})

backend/packages/harness/deerflow/tools/skill_manage_tool.py

@@ -45,9 +45,7 @@ def _get_lock(name: str) -> asyncio.Lock:
 def _get_thread_id(runtime: ToolRuntime[ContextT, ThreadState] | None) -> str | None:
     if runtime is None:
         return None
-    if runtime.context and runtime.context.get("thread_id"):
-        return runtime.context.get("thread_id")
-    return runtime.config.get("configurable", {}).get("thread_id")
+    return runtime.context.thread_id or None
 
 
 def _history_record(*, action: str, file_path: str, prev_content: str | None, new_content: str | None, thread_id: str | None, scanner: dict[str, Any]) -> dict[str, Any]:

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

@@ -2,7 +2,7 @@ import logging
 
 from langchain.tools import BaseTool
 
-from deerflow.config import get_app_config
+from deerflow.config.app_config import AppConfig
 from deerflow.reflection import resolve_variable
 from deerflow.sandbox.security import is_host_bash_allowed
 from deerflow.tools.builtins import ask_clarification_tool, present_file_tool, task_tool, view_image_tool
@@ -52,7 +52,7 @@ def get_available_tools(
     Returns:
         List of available tools.
     """
-    config = get_app_config()
+    config = AppConfig.current()
     tool_configs = [tool for tool in config.tools if groups is None or tool.group in groups]
 
     # Do not expose host bash by default when LocalSandboxProvider is active.
@@ -123,10 +123,9 @@ def get_available_tools(
     # Add invoke_acp_agent tool if any ACP agents are configured
     acp_tools: list[BaseTool] = []
     try:
-        from deerflow.config.acp_config import get_acp_agents
         from deerflow.tools.builtins.invoke_acp_agent_tool import build_invoke_acp_agent_tool
 
-        acp_agents = get_acp_agents()
+        acp_agents = AppConfig.current().acp_agents
         if acp_agents:
             acp_tools.append(build_invoke_acp_agent_tool(acp_agents))
             logger.info(f"Including invoke_acp_agent tool ({len(acp_agents)} agent(s): {list(acp_agents.keys())})")