Agent runner cannot pass temp_state via state_delta; session service ignores temp state during invocation

[dincal]

Describe the bug
When passing a state_delta to the agent runner, I need to include a temp_state. However, in the current ADK flow, the session service ignores the provided temp_state when creating the invocation and injecting events. As a result, temp-only state cannot be applied for a single turn and is effectively dropped.

To Reproduce

1. Create an agent invocation through the agent runner with state_delta that includes a temp_state payload intended only for the current turn.
2. Observe that the session service builds the invocation and injects events without applying the provided temp_state.
3. The agent runs as if temp_state was never provided.

Impact

1. Cannot apply ephemeral, per-turn overrides or sandboxed state adjustments.
2. Forces callers to mutate persistent state for transient needs, which is undesirable and error-prone.

[llalitkumarrr]

Hello @dincal,

Could you please share the relevant part of your code? This will help us reproduce the issue, analyze it in detail and provide you with a more accurate response.

[DeanChensj]

Hi @dincal , this is expected as temp state should not be persisted in session service, it is in-memory only.

[dincal]

@DeanChensj @llalitkumarrr

import asyncio

from google.adk.agents import Agent
from google.adk.runners import Runner
from google.adk.sessions import InMemorySessionService
from google.genai import types

app_name = "test_agent"
user_id = "test"
session_id = "test"
state = {}
agent = Agent(
    name="test_agent",
    description="A Agent Test",
    tools=[],
    instruction="You are an agent that can answer questions and help with tasks.",
    model="gemini-2.5-flash",
    before_agent_callback=lambda callback_context: print(callback_context.state.to_dict()),
)

session_service = InMemorySessionService()


async def main() -> None:
    if not await session_service.get_session(
        app_name=app_name,
        user_id=user_id,
        session_id=session_id,
    ):
        await session_service.create_session(
            app_name=app_name,
            user_id=user_id,
            session_id=session_id,
            state=state,
        )
    runner = Runner(
        agent=agent,
        app_name=app_name,
        session_service=session_service,
    )

    async for event in runner.run_async(
        user_id=user_id,
        session_id=session_id,
        new_message=types.Content(parts=[types.Part.from_text(text="hello")]),
        state_delta={"state_a": "a", "temp:state_b": "b"},
    ):
        pass


if __name__ == "__main__":
    asyncio.run(main())

output

{'state_a': 'a'}

I am aware that the temp state is only stored in memory and exists only within the invocation. However, when I pass the temp state while executing the runner as shown in the code above, I expect the temp state to be loaded into memory as the invocation is created, but that is not happening. Looking at the code, it seems to only insert an event into the Session Service and does not follow the code path for loading it into memory.

[dincal]

The feature I ultimately need is the ability to store state that is used only within the invocation (i.e., temporary state) without saving it to the session (DB) when creating the invocation.