Stop spurious watchdog re-prompts after the call ends

The SilenceWatchdog armed a timer on the goodbye turn; it then fired ~silence_secs
later, after EndCallProcessor had already hung up — logging phantom "re-prompt"s
(3 of 5 in the last batch were after "Goodbye"). Now it stops for good on a
closing keyword (LLMFullResponseEnd) or an EndFrame/CancelFrame, so it never
re-arms once the call is closing. Real mid-call silences still re-prompt.
Runtime-tested: no reprompt after goodbye / endframe; reprompt on normal silence.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

bot.py

@@ -25,6 +25,7 @@ from pipecat.audio.vad.vad_analyzer import VADParams
 from pipecat.frames.frames import (
     BotStartedSpeakingFrame,
     BotStoppedSpeakingFrame,
+    CancelFrame,
     EndFrame,
     EndTaskFrame,
     Frame,
@@ -373,6 +374,8 @@ class SilenceWatchdog(FrameProcessor):
         self._prompts = 0
         self._bot_speaking = False
         self._ending = False
+        self._stopped = False   # call is closing/ended — never arm again
+        self._buf = ""
 
     def _cancel(self):
         if self._timer and not self._timer.done():
@@ -409,7 +412,19 @@ class SilenceWatchdog(FrameProcessor):
 
     async def process_frame(self, frame: Frame, direction: FrameDirection):
         await super().process_frame(frame, direction)
-        if isinstance(frame, UserStartedSpeakingFrame):
+        # Stop for good once the call is closing — otherwise a timer armed on the goodbye
+        # turn fires ~silence_secs later, after the call already ended (spurious re-prompt).
+        if isinstance(frame, (EndFrame, CancelFrame)):
+            self._stopped = True
+            self._cancel()
+        elif isinstance(frame, LLMTextFrame):
+            self._buf += frame.text
+        elif isinstance(frame, LLMFullResponseEndFrame):
+            if EndCallProcessor._is_closing(self._buf):
+                self._stopped = True
+                self._cancel()
+            self._buf = ""
+        elif isinstance(frame, UserStartedSpeakingFrame):
             self._prompts = 0  # caller engaged again — reset
             self._cancel()
         elif isinstance(frame, BotStartedSpeakingFrame):
@@ -417,7 +432,9 @@ class SilenceWatchdog(FrameProcessor):
             self._cancel()
         elif isinstance(frame, BotStoppedSpeakingFrame):
             self._bot_speaking = False
-            if self._ending:
+            if self._stopped:
+                pass  # call ending — don't re-arm
+            elif self._ending:
                 asyncio.create_task(self._end_soon())
             else:
                 self._arm()  # start counting silence once the agent finishes