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/app/gateway/routers/thread_runs.py

@@ -19,7 +19,8 @@ from fastapi import APIRouter, HTTPException, Query, Request
 from fastapi.responses import Response, StreamingResponse
 from pydantic import BaseModel, Field
 
-from app.gateway.deps import get_checkpointer, get_run_manager, get_stream_bridge
+from app.gateway.authz import require_permission
+from app.gateway.deps import get_checkpointer, get_current_user, get_feedback_repo, get_run_event_store, get_run_manager, get_run_store, get_stream_bridge
 from app.gateway.services import sse_consumer, start_run
 from deerflow.runtime import RunRecord, serialize_channel_values
 
@@ -53,6 +54,7 @@ class RunCreateRequest(BaseModel):
     after_seconds: float | None = Field(default=None, description="Delayed execution")
     if_not_exists: Literal["reject", "create"] = Field(default="create", description="Thread creation policy")
     feedback_keys: list[str] | None = Field(default=None, description="LangSmith feedback keys")
+    follow_up_to_run_id: str | None = Field(default=None, description="Run ID this message follows up on. Auto-detected from latest successful run if not provided.")
 
 
 class RunResponse(BaseModel):
@@ -92,6 +94,7 @@ def _record_to_response(record: RunRecord) -> RunResponse:
 
 
 @router.post("/{thread_id}/runs", response_model=RunResponse)
+@require_permission("runs", "create", owner_check=True, require_existing=True)
 async def create_run(thread_id: str, body: RunCreateRequest, request: Request) -> RunResponse:
     """Create a background run (returns immediately)."""
     record = await start_run(body, thread_id, request)
@@ -99,6 +102,7 @@ async def create_run(thread_id: str, body: RunCreateRequest, request: Request) -
 
 
 @router.post("/{thread_id}/runs/stream")
+@require_permission("runs", "create", owner_check=True, require_existing=True)
 async def stream_run(thread_id: str, body: RunCreateRequest, request: Request) -> StreamingResponse:
     """Create a run and stream events via SSE.
 
@@ -126,6 +130,7 @@ async def stream_run(thread_id: str, body: RunCreateRequest, request: Request) -
 
 
 @router.post("/{thread_id}/runs/wait", response_model=dict)
+@require_permission("runs", "create", owner_check=True, require_existing=True)
 async def wait_run(thread_id: str, body: RunCreateRequest, request: Request) -> dict:
     """Create a run and block until it completes, returning the final state."""
     record = await start_run(body, thread_id, request)
@@ -151,6 +156,7 @@ async def wait_run(thread_id: str, body: RunCreateRequest, request: Request) ->
 
 
 @router.get("/{thread_id}/runs", response_model=list[RunResponse])
+@require_permission("runs", "read", owner_check=True)
 async def list_runs(thread_id: str, request: Request) -> list[RunResponse]:
     """List all runs for a thread."""
     run_mgr = get_run_manager(request)
@@ -159,6 +165,7 @@ async def list_runs(thread_id: str, request: Request) -> list[RunResponse]:
 
 
 @router.get("/{thread_id}/runs/{run_id}", response_model=RunResponse)
+@require_permission("runs", "read", owner_check=True)
 async def get_run(thread_id: str, run_id: str, request: Request) -> RunResponse:
     """Get details of a specific run."""
     run_mgr = get_run_manager(request)
@@ -169,6 +176,7 @@ async def get_run(thread_id: str, run_id: str, request: Request) -> RunResponse:
 
 
 @router.post("/{thread_id}/runs/{run_id}/cancel")
+@require_permission("runs", "cancel", owner_check=True, require_existing=True)
 async def cancel_run(
     thread_id: str,
     run_id: str,
@@ -206,6 +214,7 @@ async def cancel_run(
 
 
 @router.get("/{thread_id}/runs/{run_id}/join")
+@require_permission("runs", "read", owner_check=True)
 async def join_run(thread_id: str, run_id: str, request: Request) -> StreamingResponse:
     """Join an existing run's SSE stream."""
     bridge = get_stream_bridge(request)
@@ -226,6 +235,7 @@ async def join_run(thread_id: str, run_id: str, request: Request) -> StreamingRe
 
 
 @router.api_route("/{thread_id}/runs/{run_id}/stream", methods=["GET", "POST"], response_model=None)
+@require_permission("runs", "read", owner_check=True)
 async def stream_existing_run(
     thread_id: str,
     run_id: str,
@@ -265,3 +275,99 @@ async def stream_existing_run(
             "X-Accel-Buffering": "no",
         },
     )
+
+
+# ---------------------------------------------------------------------------
+# Messages / Events / Token usage endpoints
+# ---------------------------------------------------------------------------
+
+
+@router.get("/{thread_id}/messages")
+@require_permission("runs", "read", owner_check=True)
+async def list_thread_messages(
+    thread_id: str,
+    request: Request,
+    limit: int = Query(default=50, le=200),
+    before_seq: int | None = Query(default=None),
+    after_seq: int | None = Query(default=None),
+) -> list[dict]:
+    """Return displayable messages for a thread (across all runs), with feedback attached."""
+    event_store = get_run_event_store(request)
+    messages = await event_store.list_messages(thread_id, limit=limit, before_seq=before_seq, after_seq=after_seq)
+
+    # Attach feedback to the last AI message of each run
+    feedback_repo = get_feedback_repo(request)
+    user_id = await get_current_user(request)
+    feedback_map = await feedback_repo.list_by_thread_grouped(thread_id, user_id=user_id)
+
+    # Find the last ai_message per run_id
+    last_ai_per_run: dict[str, int] = {}  # run_id -> index in messages list
+    for i, msg in enumerate(messages):
+        if msg.get("event_type") == "ai_message":
+            last_ai_per_run[msg["run_id"]] = i
+
+    # Attach feedback field
+    last_ai_indices = set(last_ai_per_run.values())
+    for i, msg in enumerate(messages):
+        if i in last_ai_indices:
+            run_id = msg["run_id"]
+            fb = feedback_map.get(run_id)
+            msg["feedback"] = {
+                "feedback_id": fb["feedback_id"],
+                "rating": fb["rating"],
+                "comment": fb.get("comment"),
+            } if fb else None
+        else:
+            msg["feedback"] = None
+
+    return messages
+
+
+@router.get("/{thread_id}/runs/{run_id}/messages")
+@require_permission("runs", "read", owner_check=True)
+async def list_run_messages(
+    thread_id: str,
+    run_id: str,
+    request: Request,
+    limit: int = Query(default=50, le=200, ge=1),
+    before_seq: int | None = Query(default=None),
+    after_seq: int | None = Query(default=None),
+) -> dict:
+    """Return paginated messages for a specific run.
+
+    Response: { data: [...], has_more: bool }
+    """
+    event_store = get_run_event_store(request)
+    rows = await event_store.list_messages_by_run(
+        thread_id, run_id,
+        limit=limit + 1,
+        before_seq=before_seq,
+        after_seq=after_seq,
+    )
+    has_more = len(rows) > limit
+    data = rows[:limit] if has_more else rows
+    return {"data": data, "has_more": has_more}
+
+
+@router.get("/{thread_id}/runs/{run_id}/events")
+@require_permission("runs", "read", owner_check=True)
+async def list_run_events(
+    thread_id: str,
+    run_id: str,
+    request: Request,
+    event_types: str | None = Query(default=None),
+    limit: int = Query(default=500, le=2000),
+) -> list[dict]:
+    """Return the full event stream for a run (debug/audit)."""
+    event_store = get_run_event_store(request)
+    types = event_types.split(",") if event_types else None
+    return await event_store.list_events(thread_id, run_id, event_types=types, limit=limit)
+
+
+@router.get("/{thread_id}/token-usage")
+@require_permission("threads", "read", owner_check=True)
+async def thread_token_usage(thread_id: str, request: Request) -> dict:
+    """Thread-level token usage aggregation."""
+    run_store = get_run_store(request)
+    agg = await run_store.aggregate_tokens_by_thread(thread_id)
+    return {"thread_id": thread_id, **agg}