Fix 法规对话

backend/app/shared/async_utils.py

@@ -0,0 +1,38 @@
+"""Async utility helpers for bridging sync generators to async FastAPI routes."""
+
+from __future__ import annotations
+
+import asyncio
+import threading
+from typing import AsyncGenerator, Generator, TypeVar
+
+T = TypeVar("T")
+
+_SENTINEL = object()
+
+
+async def iter_in_thread(sync_gen: Generator[T, None, None]) -> AsyncGenerator[T, None]:
+    """Yield items from a synchronous generator without blocking the event loop.
+
+    Runs the generator in a daemon thread, forwarding items via an asyncio.Queue.
+    Use this to wrap blocking LLM streaming generators inside async FastAPI routes.
+    """
+    loop = asyncio.get_running_loop()
+    queue: asyncio.Queue = asyncio.Queue(maxsize=32)
+
+    def _drain() -> None:
+        try:
+            for item in sync_gen:
+                future = asyncio.run_coroutine_threadsafe(queue.put(item), loop)
+                future.result()
+        finally:
+            asyncio.run_coroutine_threadsafe(queue.put(_SENTINEL), loop).result()
+
+    thread = threading.Thread(target=_drain, daemon=True)
+    thread.start()
+
+    while True:
+        item = await queue.get()
+        if item is _SENTINEL:
+            break
+        yield item  # type: ignore[misc]