VertexAiSessionService.get_session Becomes Super Slow When There Are Higher Numbers of Session Events

Describe the bug
VertexAiSessionService.get_session Becomes Super Slow When There Are Higher Numbers of Session Events

To Reproduce
Accumulate some events for a session and get_session will start slowing down when the number of events gets higher.

Expected behavior
It should not get all events by default

@DeanChensj

Hey @DeanChensj
This issue makes the session service unusable as the response time grows linearly as the number of session events increase.
Please take a look.

@touhonoob

Hi @touhonoob , may I know how do you use session service? Do you use the adk api_server, or do you manage the runner yourself? I'm thinking adding configuration to only load number of recent events in session service, it will either be in the RunConfig in runner, or in the config of App

@DeanChensj

Hello @DeanChensj Thanks for checking.
I deployed my agent on Google Cloud's Vertex AI Agent Engine and didn't add any customization.
It can be easily reproduced by having a longer conversation with an ADK agent I believe.
When I checked the profiler chart it's trying to traverse through all session events pages for every single query I made, which apparently would be making it getting slower over time with growing chat history.

Maybe you guys should work on something like https://platform.openai.com/docs/api-reference/responses ?
The session service is pointless if it needs to retrieve all of the historical events

any updates pl? This is critical for production-grade deployments

@adk-bot

@adk-bot any solutions?

@adk-bot

@adk-bot any updates or quick fixes?

Thank you for reporting this performance issue and sharing the detailed analysis!

Since this issue was opened, ADK has added two mechanisms on main to prevent VertexAiSessionService.get_session from loading unbounded historical events on every turn:

Per-Run GetSessionConfig via RunConfig.get_session_config:
RunConfig (src/google/adk/agents/run_config.py) now exposes get_session_config: GetSessionConfig | None = None, which Runner forwards to session_service.get_session(..., config=run_config.get_session_config):
- after_timestamp (server-side filter): In VertexAiSessionService.get_session (src/google/adk/sessions/vertex_ai_session_service.py), setting after_timestamp pushes a server-side filter='timestamp>="..."' directly to the Vertex AI Agent Engine events.list RPC so older events are never transferred over the network.
- num_recent_events: Setting num_recent_events=0 skips calling events.list completely when only session metadata/state is needed, and num_recent_events=N bounds the events retained on the session.
```
from google.adk.agents.run_config import RunConfig
from google.adk.sessions.base_session_service import GetSessionConfig

run_config = RunConfig(
    get_session_config=GetSessionConfig(after_timestamp=cutoff_timestamp)
)
```
Automatic Sliding-Window Event Compaction (EventsCompactionConfig):
You can configure EventsCompactionConfig on App (src/google/adk/apps/app.py) to periodically summarize older turns into a single compacted event so active sessions stay bounded in length.

We're closing this issue as resolved. Please feel free to reopen it if you still experience performance bottlenecks with these options enabled!

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VertexAiSessionService.get_session Becomes Super Slow When There Are Higher Numbers of Session Events #3039

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VertexAiSessionService.get_session Becomes Super Slow When There Are Higher Numbers of Session Events #3039

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touhonoob commented on Oct 23, 2025

DeanChensj commented on Oct 24, 2025

touhonoob commented on Oct 24, 2025

touhonoob commented on Oct 24, 2025

couchrishi commented on Oct 30, 2025

arminhamp commented on Feb 5, 2026

devashishupadhyay-unlocq commented on Feb 17, 2026

DeanChensj commented on Oct 13, 2026

github-actions commented on Oct 13, 2026

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