fix: Extract grounding_metadata from Live API server_content

src/google/adk/models/gemini_llm_connection.py

@@ -139,14 +139,21 @@ async def send_realtime(self, input: RealtimeInput):
     else:
       raise ValueError('Unsupported input type: %s' % type(input))
 
-  def __build_full_text_response(self, text: str):
+  def __build_full_text_response(
+      self,
+      text: str,
+      grounding_metadata: types.GroundingMetadata | None = None,
+      interrupted: bool = False,
+  ):
     """Builds a full text response.
 
     The text should not partial and the returned LlmResponse is not be
     partial.
 
     Args:
       text: The text to be included in the response.
+      grounding_metadata: Optional grounding metadata to include.
+      interrupted: Whether this response was interrupted.
 
     Returns:
       An LlmResponse containing the full text.
@@ -156,6 +163,8 @@ def __build_full_text_response(self, text: str):
             role='model',
             parts=[types.Part.from_text(text=text)],
         ),
+        grounding_metadata=grounding_metadata,
+        interrupted=interrupted,
     )
 
   async def receive(self) -> AsyncGenerator[LlmResponse, None]:
@@ -166,6 +175,7 @@ async def receive(self) -> AsyncGenerator[LlmResponse, None]:
     """
 
     text = ''
+    last_grounding_metadata = None
     async with Aclosing(self._gemini_session.receive()) as agen:
       # TODO(b/440101573): Reuse StreamingResponseAggregator to accumulate
       # partial content and emit responses as needed.
@@ -179,17 +189,38 @@ async def receive(self) -> AsyncGenerator[LlmResponse, None]:
           )
         if message.server_content:
           content = message.server_content.model_turn
+          # Extract grounding_metadata from server_content (for VertexAiSearchTool, etc.)
+          grounding_metadata = message.server_content.grounding_metadata
+          if grounding_metadata:
+            last_grounding_metadata = grounding_metadata
+            # Warn if grounding_metadata is incomplete (has queries but no chunks)
+            # This helps identify backend issues with Vertex AI Search
+            if (
+                grounding_metadata.retrieval_queries
+                and not grounding_metadata.grounding_chunks
+            ):
+              logger.warning(
+                  'Incomplete grounding_metadata received: retrieval_queries=%s'
+                  ' but grounding_chunks is empty. This may indicate a'
+                  ' transient issue with the Vertex AI Search backend.',
+                  grounding_metadata.retrieval_queries,
+              )
           if content and content.parts:
             llm_response = LlmResponse(
-                content=content, interrupted=message.server_content.interrupted
+                content=content,
+                interrupted=message.server_content.interrupted,
+                grounding_metadata=grounding_metadata,
             )
             if content.parts[0].text:
               text += content.parts[0].text
               llm_response.partial = True
             # don't yield the merged text event when receiving audio data
             elif text and not content.parts[0].inline_data:
-              yield self.__build_full_text_response(text)
+              yield self.__build_full_text_response(
+                  text, last_grounding_metadata
+              )
               text = ''
+
             yield llm_response
           # Note: in some cases, tool_call may arrive before
           # generation_complete, causing transcription to appear after
@@ -266,32 +297,50 @@ async def receive(self) -> AsyncGenerator[LlmResponse, None]:
               self._output_transcription_text = ''
           if message.server_content.turn_complete:
             if text:
-              yield self.__build_full_text_response(text)
+              yield self.__build_full_text_response(
+                  text,
+                  last_grounding_metadata,
+                  interrupted=message.server_content.interrupted,
+              )
               text = ''
             yield LlmResponse(
                 turn_complete=True,
                 interrupted=message.server_content.interrupted,
+                grounding_metadata=last_grounding_metadata,
             )
+            last_grounding_metadata = None  # Reset after yielding
             break
           # in case of empty content or parts, we sill surface it
           # in case it's an interrupted message, we merge the previous partial
           # text. Other we don't merge. because content can be none when model
           # safety threshold is triggered
           if message.server_content.interrupted:
             if text:
-              yield self.__build_full_text_response(text)
+              yield self.__build_full_text_response(
+                  text, last_grounding_metadata, interrupted=True
+              )
               text = ''
             else:
-              yield LlmResponse(interrupted=message.server_content.interrupted)
+              yield LlmResponse(
+                  interrupted=message.server_content.interrupted,
+                  grounding_metadata=last_grounding_metadata,
+              )
         if message.tool_call:
           if text:
-            yield self.__build_full_text_response(text)
+            yield self.__build_full_text_response(text, last_grounding_metadata)
             text = ''
           parts = [
               types.Part(function_call=function_call)
               for function_call in message.tool_call.function_calls
           ]
-          yield LlmResponse(content=types.Content(role='model', parts=parts))
+          yield LlmResponse(
+              content=types.Content(role='model', parts=parts),
+              grounding_metadata=last_grounding_metadata,
+          )
+          # Note: last_grounding_metadata is NOT reset here because tool_call
+          # is part of an ongoing turn. The metadata persists until turn_complete
+          # or interrupted with break, ensuring subsequent messages in the same
+          # turn can access the grounding information.
         if message.session_resumption_update:
           logger.debug('Received session resumption message: %s', message)
           yield (