fix: Fix some swallowed CancelledError

src/backend/base/langflow/api/v1/chat.py

@@ -347,14 +347,11 @@ async def build_vertices(
         client_consumed_queue: asyncio.Queue,
         event_manager: EventManager,
     ) -> None:
-        build_task = asyncio.create_task(_build_vertex(vertex_id, graph, event_manager))
         try:
-            await build_task
-            vertex_build_response: VertexBuildResponse = build_task.result()
+            vertex_build_response: VertexBuildResponse = await _build_vertex(vertex_id, graph, event_manager)
         except asyncio.CancelledError as exc:
             logger.exception(exc)
-            build_task.cancel()
-            return
+            raise
 
         # send built event or error event
         try:
@@ -370,12 +367,7 @@ async def build_vertices(
             for next_vertex_id in vertex_build_response.next_vertices_ids:
                 task = asyncio.create_task(build_vertices(next_vertex_id, graph, client_consumed_queue, event_manager))
                 tasks.append(task)
-            try:
                 await asyncio.gather(*tasks)
-            except asyncio.CancelledError:
-                for task in tasks:
-                    task.cancel()
-                return
 
     async def event_generator(event_manager: EventManager, client_consumed_queue: asyncio.Queue) -> None:
         try:
@@ -397,9 +389,8 @@ async def event_generator(event_manager: EventManager, client_consumed_queue: as
             await asyncio.gather(*tasks)
         except asyncio.CancelledError:
             background_tasks.add_task(graph.end_all_traces)
-            for task in tasks:
-                task.cancel()
-            return
+            raise
+
         except Exception as e:
             logger.error(f"Error building vertices: {e}")
             custom_component = graph.get_vertex(vertex_id).custom_component

src/backend/base/langflow/api/v1/mcp.py

@@ -3,7 +3,6 @@
 import json
 import logging
 import traceback
-from contextlib import suppress
 from contextvars import ContextVar
 from typing import Annotated
 from urllib.parse import quote, unquote, urlparse
@@ -266,8 +265,9 @@ async def send_progress_updates():
                     return collected_results
                 finally:
                     progress_task.cancel()
-                    with suppress(asyncio.CancelledError):
-                        await progress_task
+                    await asyncio.wait([progress_task])
+                    if not progress_task.cancelled() and (exc := progress_task.exception()) is not None:
+                        raise exc
             except Exception as e:
                 msg = f"Error in async session: {e}"
                 logger.exception(msg)
@@ -333,6 +333,7 @@ async def handle_sse(request: Request, current_user: Annotated[User, Depends(get
                 logger.info("Client disconnected from SSE connection")
             except asyncio.CancelledError:
                 logger.info("SSE connection was cancelled")
+                raise
             except Exception as e:
                 msg = f"Error in MCP: {e!s}"
                 logger.exception(msg)