fix: address Gemini review feedback

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: giulio-leone

src/google/adk/flows/llm_flows/base_llm_flow.py

@@ -702,6 +702,9 @@ def get_author_for_event(llm_response):
       else:
         return invocation_context.agent.name
 
+    # Cache maps function call names to generated IDs so that partial and
+    # final streaming events for the same call share a stable ID.
+    function_call_id_cache: dict[str, str] = {}
     try:
       while True:
         async with Aclosing(llm_connection.receive()) as agen:
@@ -726,6 +729,7 @@ def get_author_for_event(llm_response):
                     llm_request,
                     llm_response,
                     model_response_event,
+                    function_call_id_cache,
                 )
             ) as agen:
               async for event in agen:
@@ -959,6 +963,7 @@ async def _postprocess_live(
       llm_request: LlmRequest,
       llm_response: LlmResponse,
       model_response_event: Event,
+      function_call_id_cache: Optional[dict[str, str]] = None,
   ) -> AsyncGenerator[Event, None]:
     """Postprocess after calling the LLM asynchronously.
 
@@ -967,6 +972,9 @@ async def _postprocess_live(
       llm_request: The original LLM request.
       llm_response: The LLM response from the LLM call.
       model_response_event: A mutable event for the LLM response.
+      function_call_id_cache: Optional dict mapping function call names to
+        previously generated IDs. Keeps IDs stable across partial and final
+        streaming events.
 
     Yields:
       A generator of events.
@@ -1028,7 +1036,8 @@ async def _postprocess_live(
 
     # Builds the event.
     model_response_event = self._finalize_model_response_event(
-        llm_request, llm_response, model_response_event
+        llm_request, llm_response, model_response_event,
+        function_call_id_cache,
     )
     yield model_response_event
 

src/google/adk/flows/llm_flows/functions.py

@@ -194,12 +194,12 @@ def populate_client_function_call_id(
       # Use (name, index) as cache key so that two calls to the same
       # function in a single response keep separate stable IDs.
       cache_key = f'{function_call.name}:{idx}'
-      if function_call_id_cache is not None and cache_key in function_call_id_cache:
-        function_call.id = function_call_id_cache[cache_key]
+      if function_call_id_cache is not None:
+        function_call.id = function_call_id_cache.setdefault(
+            cache_key, generate_client_function_call_id()
+        )
       else:
         function_call.id = generate_client_function_call_id()
-        if function_call_id_cache is not None:
-          function_call_id_cache[cache_key] = function_call.id
 
 
 def remove_client_function_call_id(content: Optional[types.Content]) -> None: