fix: propagate grounding and citation metadata in streaming responses

Co-authored-by: Sasha Sobran <asobran@google.com>
PiperOrigin-RevId: 868324488

src/google/adk/utils/streaming_utils.py

@@ -36,6 +36,8 @@ class StreamingResponseAggregator:
     self._text = ''
     self._thought_text = ''
     self._usage_metadata = None
+    self._grounding_metadata: Optional[types.GroundingMetadata] = None
+    self._citation_metadata: Optional[types.CitationMetadata] = None
     self._response = None
 
     # For progressive SSE streaming mode: accumulate parts in order
@@ -251,6 +253,10 @@ class StreamingResponseAggregator:
     self._response = response
     llm_response = LlmResponse.create(response)
     self._usage_metadata = llm_response.usage_metadata
+    if llm_response.grounding_metadata:
+      self._grounding_metadata = llm_response.grounding_metadata
+    if llm_response.citation_metadata:
+      self._citation_metadata = llm_response.citation_metadata
 
     # ========== Progressive SSE Streaming (new feature) ==========
     # Save finish_reason for final aggregation
@@ -347,6 +353,8 @@ class StreamingResponseAggregator:
 
           return LlmResponse(
               content=types.ModelContent(parts=final_parts),
+              grounding_metadata=self._grounding_metadata,
+              citation_metadata=self._citation_metadata,
               error_code=None
               if finish_reason == types.FinishReason.STOP
               else finish_reason,
@@ -374,6 +382,8 @@ class StreamingResponseAggregator:
       candidate = self._response.candidates[0]
       return LlmResponse(
           content=types.ModelContent(parts=parts),
+          grounding_metadata=self._grounding_metadata,
+          citation_metadata=self._citation_metadata,
           error_code=None
           if candidate.finish_reason == types.FinishReason.STOP
           else candidate.finish_reason,