Propagate Azure TTS/STT cancellation errors to the pipeline

Azure TTS _handle_canceled was putting None (the normal completion
signal) into the audio queue for all cancellation reasons, so run_tts
treated errors identically to success—silently producing no audio.
Now error cancellations put an Exception marker in the queue, which
run_tts converts to an ErrorFrame.

Azure STT had no canceled event handler at all, so auth failures,
network errors, and rate-limit cancellations were invisible. Added
_on_handle_canceled which pushes an ErrorFrame upstream via push_error.

Fixes pipecat-ai/pipecat#3892

changelog/3893.fixed.md

@@ -0,0 +1 @@
+- Fixed Azure TTS and STT services silently swallowing cancellation errors (invalid API key, network failures, rate limiting) instead of propagating them as `ErrorFrame`s to the pipeline.

src/pipecat/services/azure/stt.py

@@ -35,6 +35,7 @@ from pipecat.utils.tracing.service_decorators import traced_stt
 
 try:
     from azure.cognitiveservices.speech import (
+        CancellationReason,
         ResultReason,
         SpeechConfig,
         SpeechRecognizer,
@@ -209,6 +210,7 @@ class AzureSTTService(STTService):
             )
             self._speech_recognizer.recognizing.connect(self._on_handle_recognizing)
             self._speech_recognizer.recognized.connect(self._on_handle_recognized)
+            self._speech_recognizer.canceled.connect(self._on_handle_canceled)
             self._speech_recognizer.start_continuous_recognition_async()
         except Exception as e:
             await self.push_error(
@@ -280,3 +282,13 @@ class AzureSTTService(STTService):
                 result=event,
             )
             asyncio.run_coroutine_threadsafe(self.push_frame(frame), self.get_event_loop())
+
+    def _on_handle_canceled(self, event):
+        details = event.result.cancellation_details
+        if details.reason == CancellationReason.Error:
+            error_msg = f"Azure STT recognition canceled: {details.reason}"
+            if details.error_details:
+                error_msg += f" - {details.error_details}"
+            asyncio.run_coroutine_threadsafe(
+                self.push_error(error_msg=error_msg), self.get_event_loop()
+            )

src/pipecat/services/azure/tts.py

@@ -561,9 +561,13 @@ class AzureTTSService(TTSService, AzureBaseTTSService):
         # User cancellation (from interruption) is expected, not an error
         if reason == CancellationReason.CancelledByUser:
             logger.debug(f"{self}: Speech synthesis canceled by user (interruption)")
+            self._audio_queue.put_nowait(None)
         else:
-            logger.warning(f"{self}: Speech synthesis canceled: {reason}")
-        self._audio_queue.put_nowait(None)
+            details = evt.result.cancellation_details
+            error_msg = f"Azure TTS synthesis canceled: {reason}"
+            if details.error_details:
+                error_msg += f" - {details.error_details}"
+            self._audio_queue.put_nowait(Exception(error_msg))
 
     async def push_frame(self, frame: Frame, direction: FrameDirection = FrameDirection.DOWNSTREAM):
         """Push a frame and handle state changes.
@@ -676,6 +680,9 @@ class AzureTTSService(TTSService, AzureBaseTTSService):
                     chunk = await self._audio_queue.get()
                     if chunk is None:  # End of stream
                         break
+                    if isinstance(chunk, Exception):  # Error from _handle_canceled
+                        yield ErrorFrame(error=str(chunk))
+                        break
 
                     if self._first_chunk:
                         await self.stop_ttfb_metrics()