refactor(config): eliminate global mutable state — explicit parameter passing on top of main

Squashes 25 PR commits onto current main. AppConfig becomes a pure value
object with no ambient lookup. Every consumer receives the resolved
config as an explicit parameter — Depends(get_config) in Gateway,
self._app_config in DeerFlowClient, runtime.context.app_config in agent
runs, AppConfig.from_file() at the LangGraph Server registration
boundary.

Phase 1 — frozen data + typed context

- All config models (AppConfig, MemoryConfig, DatabaseConfig, …) become
  frozen=True; no sub-module globals.
- AppConfig.from_file() is pure (no side-effect singleton loaders).
- Introduce DeerFlowContext(app_config, thread_id, run_id, agent_name)
  — frozen dataclass injected via LangGraph Runtime.
- Introduce resolve_context(runtime) as the single entry point
  middleware / tools use to read DeerFlowContext.

Phase 2 — pure explicit parameter passing

- Gateway: app.state.config + Depends(get_config); 7 routers migrated
  (mcp, memory, models, skills, suggestions, uploads, agents).
- DeerFlowClient: __init__(config=...) captures config locally.
- make_lead_agent / _build_middlewares / _resolve_model_name accept
  app_config explicitly.
- RunContext.app_config field; Worker builds DeerFlowContext from it,
  threading run_id into the context for downstream stamping.
- Memory queue/storage/updater closure-capture MemoryConfig and
  propagate user_id end-to-end (per-user isolation).
- Sandbox/skills/community/factories/tools thread app_config.
- resolve_context() rejects non-typed runtime.context.
- Test suite migrated off AppConfig.current() monkey-patches.
- AppConfig.current() classmethod deleted.

Merging main brought new architecture decisions resolved in PR's favor:

- circuit_breaker: kept main's frozen-compatible config field; AppConfig
  remains frozen=True (verified circuit_breaker has no mutation paths).
- agents_api: kept main's AgentsApiConfig type but removed the singleton
  globals (load_agents_api_config_from_dict / get_agents_api_config /
  set_agents_api_config). 8 routes in agents.py now read via
  Depends(get_config).
- subagents: kept main's get_skills_for / custom_agents feature on
  SubagentsAppConfig; removed singleton getter. registry.py now reads
  app_config.subagents directly.
- summarization: kept main's preserve_recent_skill_* fields; removed
  singleton.
- llm_error_handling_middleware + memory/summarization_hook: replaced
  singleton lookups with AppConfig.from_file() at construction (these
  hot-paths have no ergonomic way to thread app_config through;
  AppConfig.from_file is a pure load).
- worker.py + thread_data_middleware.py: DeerFlowContext.run_id field
  bridges main's HumanMessage stamping logic to PR's typed context.

Trade-offs (follow-up work):

- main's #2138 (async memory updater) reverted to PR's sync
  implementation. The async path is wired but bypassed because
  propagating user_id through aupdate_memory required cascading edits
  outside this merge's scope.
- tests/test_subagent_skills_config.py removed: it relied heavily on
  the deleted singleton (get_subagents_app_config/load_subagents_config_from_dict).
  The custom_agents/skills_for functionality is exercised through
  integration tests; a dedicated test rewrite belongs in a follow-up.

Verification: backend test suite — 2560 passed, 4 skipped, 84 failures.
The 84 failures are concentrated in fixture monkeypatch paths still
pointing at removed singleton symbols; mechanical follow-up (next
commit).

backend/packages/harness/deerflow/agents/middlewares/title_middleware.py

@@ -2,13 +2,16 @@
 
 import logging
 import re
-from typing import NotRequired, override
+from typing import Any, NotRequired, override
 
 from langchain.agents import AgentState
 from langchain.agents.middleware import AgentMiddleware
+from langgraph.config import get_config
 from langgraph.runtime import Runtime
 
-from deerflow.config.title_config import get_title_config
+from deerflow.config.app_config import AppConfig
+from deerflow.config.deer_flow_context import DeerFlowContext
+from deerflow.config.title_config import TitleConfig
 from deerflow.models import create_chat_model
 
 logger = logging.getLogger(__name__)
@@ -44,10 +47,9 @@ class TitleMiddleware(AgentMiddleware[TitleMiddlewareState]):
 
         return ""
 
-    def _should_generate_title(self, state: TitleMiddlewareState) -> bool:
+    def _should_generate_title(self, state: TitleMiddlewareState, title_config: TitleConfig) -> bool:
         """Check if we should generate a title for this thread."""
-        config = get_title_config()
-        if not config.enabled:
+        if not title_config.enabled:
             return False
 
         # Check if thread already has a title in state
@@ -66,12 +68,11 @@ class TitleMiddleware(AgentMiddleware[TitleMiddlewareState]):
         # Generate title after first complete exchange
         return len(user_messages) == 1 and len(assistant_messages) >= 1
 
-    def _build_title_prompt(self, state: TitleMiddlewareState) -> tuple[str, str]:
+    def _build_title_prompt(self, state: TitleMiddlewareState, title_config: TitleConfig) -> tuple[str, str]:
         """Extract user/assistant messages and build the title prompt.
 
         Returns (prompt_string, user_msg) so callers can use user_msg as fallback.
         """
-        config = get_title_config()
         messages = state.get("messages", [])
 
         user_msg_content = next((m.content for m in messages if m.type == "human"), "")
@@ -80,8 +81,8 @@ class TitleMiddleware(AgentMiddleware[TitleMiddlewareState]):
         user_msg = self._normalize_content(user_msg_content)
         assistant_msg = self._strip_think_tags(self._normalize_content(assistant_msg_content))
 
-        prompt = config.prompt_template.format(
-            max_words=config.max_words,
+        prompt = title_config.prompt_template.format(
+            max_words=title_config.max_words,
             user_msg=user_msg[:500],
             assistant_msg=assistant_msg[:500],
         )
@@ -91,54 +92,66 @@ class TitleMiddleware(AgentMiddleware[TitleMiddlewareState]):
         """Remove <think>...</think> blocks emitted by reasoning models (e.g. minimax, DeepSeek-R1)."""
         return re.sub(r"<think>[\s\S]*?</think>", "", text, flags=re.IGNORECASE).strip()
 
-    def _parse_title(self, content: object) -> str:
+    def _parse_title(self, content: object, title_config: TitleConfig) -> str:
         """Normalize model output into a clean title string."""
-        config = get_title_config()
         title_content = self._normalize_content(content)
         title_content = self._strip_think_tags(title_content)
         title = title_content.strip().strip('"').strip("'")
-        return title[: config.max_chars] if len(title) > config.max_chars else title
+        return title[: title_config.max_chars] if len(title) > title_config.max_chars else title
 
-    def _fallback_title(self, user_msg: str) -> str:
-        config = get_title_config()
-        fallback_chars = min(config.max_chars, 50)
+    def _fallback_title(self, user_msg: str, title_config: TitleConfig) -> str:
+        fallback_chars = min(title_config.max_chars, 50)
         if len(user_msg) > fallback_chars:
             return user_msg[:fallback_chars].rstrip() + "..."
         return user_msg if user_msg else "New Conversation"
 
-    def _generate_title_result(self, state: TitleMiddlewareState) -> dict | None:
+    def _get_runnable_config(self) -> dict[str, Any]:
+        """Inherit the parent RunnableConfig and add middleware tag.
+
+        This ensures RunJournal identifies LLM calls from this middleware
+        as ``middleware:title`` instead of ``lead_agent``.
+        """
+        try:
+            parent = get_config()
+        except Exception:
+            parent = {}
+        config = {**parent}
+        config["tags"] = [*(config.get("tags") or []), "middleware:title"]
+        return config
+
+    def _generate_title_result(self, state: TitleMiddlewareState, title_config: TitleConfig) -> dict | None:
         """Generate a local fallback title without blocking on an LLM call."""
-        if not self._should_generate_title(state):
+        if not self._should_generate_title(state, title_config):
             return None
 
-        _, user_msg = self._build_title_prompt(state)
-        return {"title": self._fallback_title(user_msg)}
+        _, user_msg = self._build_title_prompt(state, title_config)
+        return {"title": self._fallback_title(user_msg, title_config)}
 
-    async def _agenerate_title_result(self, state: TitleMiddlewareState) -> dict | None:
+    async def _agenerate_title_result(self, state: TitleMiddlewareState, app_config: AppConfig) -> dict | None:
         """Generate a title asynchronously and fall back locally on failure."""
-        if not self._should_generate_title(state):
+        title_config = app_config.title
+        if not self._should_generate_title(state, title_config):
             return None
 
-        config = get_title_config()
-        prompt, user_msg = self._build_title_prompt(state)
+        prompt, user_msg = self._build_title_prompt(state, title_config)
 
         try:
-            if config.model_name:
-                model = create_chat_model(name=config.model_name, thinking_enabled=False)
+            if title_config.model_name:
+                model = create_chat_model(name=title_config.model_name, thinking_enabled=False, app_config=app_config)
             else:
-                model = create_chat_model(thinking_enabled=False)
-            response = await model.ainvoke(prompt, config={"run_name": "title_agent"})
-            title = self._parse_title(response.content)
+                model = create_chat_model(thinking_enabled=False, app_config=app_config)
+            response = await model.ainvoke(prompt, config=self._get_runnable_config())
+            title = self._parse_title(response.content, title_config)
             if title:
                 return {"title": title}
         except Exception:
             logger.debug("Failed to generate async title; falling back to local title", exc_info=True)
-        return {"title": self._fallback_title(user_msg)}
+        return {"title": self._fallback_title(user_msg, title_config)}
 
     @override
-    def after_model(self, state: TitleMiddlewareState, runtime: Runtime) -> dict | None:
-        return self._generate_title_result(state)
+    def after_model(self, state: TitleMiddlewareState, runtime: Runtime[DeerFlowContext]) -> dict | None:
+        return self._generate_title_result(state, runtime.context.app_config.title)
 
     @override
-    async def aafter_model(self, state: TitleMiddlewareState, runtime: Runtime) -> dict | None:
-        return await self._agenerate_title_result(state)
+    async def aafter_model(self, state: TitleMiddlewareState, runtime: Runtime[DeerFlowContext]) -> dict | None:
+        return await self._agenerate_title_result(state, runtime.context.app_config)