fix: harden realtime pipeline lifecycle

backend/services/realtime/lifecycle.py

@@ -12,13 +12,33 @@ from loguru import logger
 active_connections: set[object] = set()
 pipeline_tasks: set[asyncio.Task[None]] = set()
 connection_tasks: dict[object, asyncio.Task[None]] = {}
+connection_cleanup_tasks: set[asyncio.Task[None]] = set()
 DEFAULT_CLOSE_GRACE_SECONDS = 10.0
 
 
+async def _disconnect_connection(connection: object) -> None:
+    """Release media even when construction failed before transport startup."""
+    try:
+        async with asyncio.timeout(DEFAULT_CLOSE_GRACE_SECONDS):
+            await connection.disconnect()
+    except Exception as exc:
+        logger.warning(f"Realtime 连接清理失败: {type(exc).__name__}")
+
+
 def _consume_pipeline_result(task: asyncio.Task[None], connection: object) -> None:
     pipeline_tasks.discard(task)
     if connection_tasks.get(connection) is task:
         connection_tasks.pop(connection, None)
+    if connection in active_connections:
+        active_connections.discard(connection)
+        # Run after the pipeline task is done: closed handlers can safely wait
+        # for that task without making pipeline shutdown wait on itself.
+        cleanup = asyncio.create_task(
+            _disconnect_connection(connection),
+            name=f"realtime-disconnect:{getattr(connection, 'pc_id', id(connection))}",
+        )
+        connection_cleanup_tasks.add(cleanup)
+        cleanup.add_done_callback(connection_cleanup_tasks.discard)
     try:
         error = task.exception()
     except asyncio.CancelledError:
@@ -86,11 +106,15 @@ async def shutdown_active_sessions(
 ) -> None:
     connections = list(active_connections)
     if connections:
+        active_connections.difference_update(connections)
         await asyncio.gather(
-            *(connection.disconnect() for connection in connections),
+            *(_disconnect_connection(connection) for connection in connections),
             return_exceptions=True,
         )
-        active_connections.difference_update(connections)
+
+    cleanup_tasks = list(connection_cleanup_tasks)
+    if cleanup_tasks:
+        await asyncio.gather(*cleanup_tasks, return_exceptions=True)
 
     tasks = list(pipeline_tasks)
     if not tasks:
@@ -106,4 +130,3 @@ async def shutdown_active_sessions(
     logger.info(
         f"Realtime 会话清理完成: normal={len(done)} cancelled={len(cancelled)}"
     )
-