Google ADK: why InMemoryMemoryService never calls add_session_to_memory

Disclosure: I work on MemorySync (I'm Mohammed, the founder). I drafted this page with AI assistance and checked it against the source issue and the MemorySync Google ADK guide. I didn't run any code on this page.

The question

In google/adk-python#7527 (opened Oct 13 2026), a developer asked why initialising an agent with InMemoryMemoryService doesn't call add_session_to_memory automatically, and whether it has to be called through callbacks.

Status (checked 2026-11-02 via the GitHub API): closed. A maintainer replied that ADK does not add sessions to memory automatically, so the app has to call add_session_to_memory. A bot marked the issue stale on Oct 23 and closed it on Oct 31, 2026 with no code change, so the answer below still applies.

Skip the memory plumbing around this fix. Once the fix below is in, the MemorySync Google ADK guide shows how to add per-user memory with MemorySync. MemorySync doesn't fix this error itself. When you're ready, see MemorySync. Founding offer: use code FOUNDING30 for 30% off Starter for your first 3 months (Settings → Billing).

The answer

A memory service in ADK is storage plus search. Passing one to the Runner makes it available to tools like load_memory and preload_memory, but nothing copies a finished session into it unless your code does. Per the maintainer's reply and the ADK memory docs, you have two places to do it:

1. After a run, fetch the session and call memory_service.add_session_to_memory(session).
2. In an after_agent_callback, so every agent run ingests its session without extra code at the call site.

Sketch of option 1 (not run; check names against your ADK version):

session = await runner.session_service.get_session(
    app_name="support", user_id="customer-7", session_id="thread-42"
)
await memory_service.add_session_to_memory(session)

Two things to keep in mind:

• InMemoryMemoryService lives in process memory, so whatever you add is gone after a restart. It's meant for prototyping.
• If you ingest the whole session after every turn, think about duplicates: the in-memory service in the issue's snippet overwrites per session ID, but other backends may not.

Skip the plumbing with MemorySync

Disclosure: I build MemorySync.

Only if you need memory that outlives the process. The MemorySync Google ADK guide documents a MemorySyncMemoryService that implements add_session_to_memory against managed storage, so ADK's own preload_memory can recall a user's facts in a later session. You still have to call it (or use the guide's context tool or callback), exactly as the maintainer described. It doesn't change the answer above.

From the guide:

Unverified (not run):

pip install google-adk-memorysync google-adk

Requires google-adk 2.0+ (Python 3.10+).

from google.adk.agents import LlmAgent
from google.adk.runners import Runner
from google.adk.sessions import InMemorySessionService
from google.adk.tools import preload_memory
from google_adk_memorysync import MemorySyncMemoryService

memory_service = MemorySyncMemoryService()  # reads MEMORYSYNC_API_KEY

agent = LlmAgent(
    name="assistant",
    model="your-model",
    instruction="You are a helpful assistant.",
    tools=[preload_memory],  # ADK's native tool — our service powers it
)

runner = Runner(
    agent=agent,
    app_name="support",
    session_service=InMemorySessionService(),
    memory_service=memory_service,
)

# ... after a conversation, ingest the session:
session = await runner.session_service.get_session(
    app_name="support", user_id="customer-7", session_id="thread-42"
)
await memory_service.add_session_to_memory(session)

# The next run — any session, any process, any deploy —
# preload_memory injects what MemorySync knows about the user.

Snippet adapted from the MemorySync Google ADK guide; I haven't run it for this page.

Try it: MemorySync is optional here: the steps above work without it. If you want the memory layer from the snippet, see MemorySync, create an API key in the dashboard and drop the snippet into your agent.

Next step

Read the MemorySync Google ADK guide. For an overview of MemorySync, see the MemorySync homepage.

Sources

• google/adk-python#7527, "InMemoryMemoryService does not call add_session_to_memory?" (read 2026-10-28)
• ADK docs: Memory, https://adk.dev/sessions/memory/
• MemorySync Google ADK guide: docs.memorysync.io/guides/google-adk

Next step: read the MemorySync Google ADK guide, then see MemorySync. Founding offer: use code FOUNDING30 for 30% off Starter for your first 3 months (Settings → Billing).