PipelineTask: avoid cancellation if application is finished

CHANGELOG.md

@@ -13,6 +13,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Fixed
 
+- Fixed a `PipelineTask` issue that could prevent the application to exit if
+  `task.cancel()` was called when the task was already finished.
+
 - Fixed an issue where local SmartTurn was not being ran in a separate thread.
 
 ## [0.0.86] - 2025-09-24

src/pipecat/pipeline/task.py

@@ -13,8 +13,7 @@ including heartbeats, idle detection, and observer integration.
 
 import asyncio
 import time
-from collections import deque
-from typing import Any, AsyncIterable, Deque, Dict, Iterable, List, Optional, Tuple, Type
+from typing import Any, AsyncIterable, Dict, Iterable, List, Optional, Tuple, Type
 
 from loguru import logger
 from pydantic import BaseModel, ConfigDict, Field
@@ -31,7 +30,6 @@ from pipecat.frames.frames import (
     ErrorFrame,
     Frame,
     HeartbeatFrame,
-    InputAudioRawFrame,
     InterruptionFrame,
     InterruptionTaskFrame,
     MetricsFrame,
@@ -395,7 +393,8 @@ class PipelineTask(BasePipelineTask):
         Cancels all running tasks and stops frame processing without
         waiting for completion.
         """
-        await self._cancel()
+        if not self._finished:
+            await self._cancel()
 
     async def run(self, params: PipelineTaskParams):
         """Start and manage the pipeline execution until completion or cancellation.