diff --git a/packages/services/voice-agent/src/plugins/speechmatics_stt.py b/packages/services/voice-agent/src/plugins/speechmatics_stt.py
index fd0fdcd..9e632bd 100644
--- a/packages/services/voice-agent/src/plugins/speechmatics_stt.py
+++ b/packages/services/voice-agent/src/plugins/speechmatics_stt.py
@@ -2,17 +2,54 @@
 Speechmatics STT factory for voice-agent.
 
 Creates a livekit-plugins-speechmatics STT instance configured for
-Mandarin-English bilingual recognition with speaker diarization support.
+Mandarin recognition with speaker diarization support.
 
 The SPEECHMATICS_API_KEY environment variable is read automatically
 by the livekit-plugins-speechmatics package.
 """
+import asyncio
 import logging
 
+from livekit.agents import stt, utils
 from livekit.plugins.speechmatics import STT, TurnDetectionMode
+from livekit.plugins.speechmatics.stt import SpeechStream
 
 logger = logging.getLogger(__name__)
 
+# ---------------------------------------------------------------------------
+# Monkey-patch SpeechStream._process_audio so that a FlushSentinel triggers
+# client.finalize().  In EXTERNAL turn-detection mode the Speechmatics server
+# only emits AddSegment (FINAL_TRANSCRIPT) after an explicit finalize signal.
+# The upstream plugin flushes the byte-stream but never calls finalize(),
+# which means LiveKit's VAD-driven flush never produces a final transcript.
+# ---------------------------------------------------------------------------
+_original_process_audio = SpeechStream._process_audio
+
+
+async def _patched_process_audio(self: SpeechStream) -> None:  # type: ignore[override]
+    try:
+        audio_bstream = utils.audio.AudioByteStream(
+            sample_rate=self._stt._sample_rate,
+            num_channels=1,
+        )
+        async for data in self._input_ch:
+            if isinstance(data, self._FlushSentinel):
+                frames = audio_bstream.flush()
+                # >>> patch: tell Speechmatics the turn ended <<<
+                if self._client and self._client._is_connected:
+                    self._client.finalize()
+            else:
+                frames = audio_bstream.write(data.data.tobytes())
+
+            if self._client:
+                for frame in frames:
+                    self._speech_duration += frame.duration
+                    await self._client.send_audio(frame.data.tobytes())
+    except asyncio.CancelledError:
+        pass
+
+
+SpeechStream._process_audio = _patched_process_audio  # type: ignore[assignment]
 
 # Map Whisper language codes to Speechmatics language codes
 _LANG_MAP = {