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Allow limiting num. of Session events fetched when calling Runner.run_async #3562
Description
Is your feature request related to a problem? Please describe.
Yes.
I want to limit the number of events pulled from the Session DB when calling session_service.get_session inside the Runner.run_async. Without limiting, the get_session can pull a large num. of events from the DB.
I am using a Runner class object to run an agent as below:
runner = Runner(
agent=orchestrator_agent, app_name=APP_NAME, session_service=session_service
)
async for event in runner.run_async(
user_id=req.user_id, session_id=session.id, new_message=user_message
):
if event.is_final_response():
if event.content and event.content.parts:
agent_response = event.content.parts[0].textHere, inside the Runner.run_async method, it is fetching session events using the session service we passed when constructing the Runner object.
with tracer.start_as_current_span('invocation'):
session = await self.session_service.get_session(
app_name=self.app_name, user_id=user_id, session_id=session_id
)This call is leading to fetch all the session events which is not desired. It would be better to have a way to limit the num. of session events fetched.
Describe the solution you'd like
The BaseSessionService already accepts a [GetSessionConfig](config: Optional[GetSessionConfig] = None) field in get_session method. This is used in DatabaseSessionService's get_session method if provided.
if config and config.after_timestamp:
after_dt = datetime.fromtimestamp(config.after_timestamp)
stmt = stmt.filter(StorageEvent.timestamp >= after_dt)
stmt = stmt.order_by(StorageEvent.timestamp.desc())
if config and config.num_recent_events:
stmt = stmt.limit(config.num_recent_events)My Solution:
Add an optional field to RunConfig class which is passed as run_config parameter of Runner.run_async method. Then it can be used to pass to SessionService.get_session method as config.
class RunConfig(BaseModel):
get_session_config: Optional[GetSessionConfig] = None # New optional field
# Use above field in run_async method
class Runner:
async def run_async(..., run_config: Optional[RunConfig] = None, ) -> AsyncGenerator[Event, None]:
# existing code ...
async def _run_with_trace(
new_message: Optional[types.Content] = None,
invocation_id: Optional[str] = None,
) -> AsyncGenerator[Event, None]:
with tracer.start_as_current_span('invocation'):
session = await self.session_service.get_session(
app_name=self.app_name, user_id=user_id, session_id=session_id, config=run_config.get_session_config
)
# existing code ....Describe alternatives you've considered
Without native support from ADK, I would have to implement a custom DatabaseSessionService that allows users to set a limit and pass an instance of that session service to the runner. I don't like this approach.
Additional context
I noticed there's a closed PR for this feature: #2843
Activity
nimanthadilz commentedon Nov 15, 2025
Hi,
I am happy to raise a PR with your comments/suggestions regarding this issue.
nimanthadilz commentedon Nov 22, 2025
@DeanChensj @adk-bot Do you think
RunConfigis a better place to add aboveget_session_configproperty?thomasErich135 commentedon Dec 28, 2025
Hi Team,
I´m facing the same problem regarding sessions with a lot of events in Vertex Session Service.
When a session has too many events, we run into two main issues:
Depending on the use case, we don't need to fetch the entire history. The proposal from @nimanthadilz allows us to set a limit on the number of events or define a timestamp cutoff.
Could you please prioritize this feature?
klateefa commentedon Feb 11, 2026
@nimanthadilz Thanks for the update. The request is currently being reviewed, and I will let you know if anything further is needed. Thank you for your understanding.
feat(runners): pass GetSessionConfig through Runner to session service
GWeale commentedon Jun 17, 2026
Thanks for raising this. It landed on main via #4693 (commit eff724a): RunConfig now takes a get_session_config, so you can pass GetSessionConfig(num_recent_events=..., after_timestamp=...) through run_async to limit the events fetched. Closing as fixed, please reopen if it doesn't cover your case.
feat(runners): pass GetSessionConfig through Runner to session service