diff --git a/src/google/adk/models/gemini_llm_connection.py b/src/google/adk/models/gemini_llm_connection.py
index 8d8ed5d6dc..fe9938b1e3 100644
--- a/src/google/adk/models/gemini_llm_connection.py
+++ b/src/google/adk/models/gemini_llm_connection.py
@@ -109,6 +109,17 @@ async def send_content(self, content: types.Content):
           function_responses=function_responses
       )
     else:
+      # 3.1 models reject LiveClientContent for mid-conversation text
+      if self._model_version and '3.1' in self._model_version:
+        text_parts = [p.text for p in content.parts if p.text]
+        if text_parts:
+          combined = ' '.join(text_parts)
+          logger.debug(
+              'Sending text via realtime input for 3.1 model: %s',
+              combined[:100],
+          )
+          await self._gemini_session.send_realtime_input(text=combined)
+          return
       logger.debug('Sending LLM new content %s', content)
       is_gemini_31 = model_name_utils.is_gemini_3_1_flash_live(
           self._model_version
diff --git a/src/google/adk/models/google_llm.py b/src/google/adk/models/google_llm.py
index 0114d73a82..8e289e2c7c 100644
--- a/src/google/adk/models/google_llm.py
+++ b/src/google/adk/models/google_llm.py
@@ -415,6 +415,16 @@ async def connect(self, llm_request: LlmRequest) -> BaseLlmConnection:
             ' backend. Please use Vertex AI backend.'
         )
     llm_request.live_connect_config.tools = llm_request.config.tools
+
+    # 3.1 models require history_config for session history to work
+    model_name = llm_request.model or ''
+    if '3.1' in model_name and not getattr(
+        llm_request.live_connect_config, 'history_config', None
+    ):
+      llm_request.live_connect_config.history_config = types.HistoryConfig(
+          initial_history_in_client_content=True
+      )
+
     logger.debug('Connecting to live with llm_request:%s', llm_request)
     logger.debug('Live connect config: %s', llm_request.live_connect_config)
     async with self._live_api_client.aio.live.connect(