feat: add keyterms_prompt to AssemblyAI service

src/pipecat/services/assemblyai/models.py

@@ -108,6 +108,7 @@ class AssemblyAIConnectionParams(BaseModel):
         end_of_turn_confidence_threshold: Confidence threshold for end-of-turn detection.
         min_end_of_turn_silence_when_confident: Minimum silence duration when confident about end-of-turn.
         max_turn_silence: Maximum silence duration before forcing end-of-turn.
+        keyterms_prompt: List of key terms to guide transcription. Will be JSON serialized before sending.
     """
 
     sample_rate: int = 16000
@@ -117,3 +118,4 @@ class AssemblyAIConnectionParams(BaseModel):
     end_of_turn_confidence_threshold: Optional[float] = None
     min_end_of_turn_silence_when_confident: Optional[int] = None
     max_turn_silence: Optional[int] = None
+    keyterms_prompt: Optional[List[str]] = None

src/pipecat/services/assemblyai/stt.py

@@ -174,11 +174,16 @@ class AssemblyAISTTService(STTService):
 
     def _build_ws_url(self) -> str:
         """Build WebSocket URL with query parameters using urllib.parse.urlencode."""
-        params = {
-            k: str(v).lower() if isinstance(v, bool) else v
-            for k, v in self._connection_params.model_dump().items()
-            if v is not None
-        }
+        params = {}
+        for k, v in self._connection_params.model_dump().items():
+            if v is not None:
+                if k == "keyterms_prompt":
+                    params[k] = json.dumps(v)
+                elif isinstance(v, bool):
+                    params[k] = str(v).lower()
+                else:
+                    params[k] = v
+        
         if params:
             query_string = urlencode(params)
             return f"{self._api_endpoint_base_url}?{query_string}"