Main merge into the branch + error string update

Author: DanieleMorotti

.github/workflows/tests.yml

@@ -84,5 +84,7 @@ jobs:
           enable-cache: true
       - name: Install dependencies
         run: make sync
+      - name: Install Python 3.9 dependencies
+        run: UV_PROJECT_ENVIRONMENT=.venv_39 uv sync --all-extras --all-packages --group dev
       - name: Run tests
         run: make old_version_tests

src/agents/memory/openai_conversations_session.py

@@ -19,9 +19,6 @@ async def start_openai_conversations_session(openai_client: AsyncOpenAI | None =
     return response.id
 
 
-_EMPTY_SESSION_ID = ""
-
-
 class OpenAIConversationsSession(SessionABC):
     def __init__(
         self,

src/agents/run.py

@@ -418,7 +418,8 @@ async def run(
         if run_config is None:
             run_config = RunConfig()
 
-        # Prepare input with session if enabled
+        # Keep original user input separate from session-prepared input
+        original_user_input = input
         prepared_input = await self._prepare_input_with_session(
             input, session, run_config.session_input_callback
         )
@@ -447,8 +448,8 @@ async def run(
             current_agent = starting_agent
             should_run_agent_start_hooks = True
 
-            # save the original input to the session if enabled
-            await self._save_result_to_session(session, original_input, [])
+            # save only the new user input to the session, not the combined history
+            await self._save_result_to_session(session, original_user_input, [])
 
             try:
                 while True:
@@ -1490,13 +1491,14 @@ async def _prepare_input_with_session(
         if session is None:
             return input
 
-        # If the user doesn't explicitly specify a mode, raise an error
+        # If the user doesn't specify an input callback and pass a list as input
         if isinstance(input, list) and not session_input_callback:
             raise UserError(
-                "You must specify the `session_input_callback` in the `RunConfig`. "
-                "Otherwise, when using session memory, provide only a string input to append to "
-                "the conversation, or use session=None and provide a list to manually manage "
-                "conversation history."
+                "When using session memory, list inputs require a "
+                "`RunConfig.session_input_callback` to define how they should be merged "
+                "with the conversation history. If you don't want to use a callback, "
+                "provide your input as a string instead, or disable session memory "
+                "(session=None) and pass a list to manage the history manually."
             )
 
         # Get previous conversation history